Rotor size/lever leverage/stopping distance discussion

[Mars2]

It's the first time I have 220mm rotor's in front and it's also the first time I lock my front wheel at entry of curve and then go out of my line. I even fall a couple of time because of that. Never happen to me on this bike park that I ride 2 or 3 time a week.
200mm is exaggerating the on off style off the Shimano making it very hard to modulate brake not to block front wheel at this moment of summer where it's crazy dry and very low surface grip.
This could be even more exaggerated because I have front brake on right hand, My powerful hand.

So for me:
Summer will be 200mm rotor. Specialy on Alps bike park that get super dusty in summer. so less grip
Winter when their is much more grip here in south of France, maybe 220mm if I feel the need. But the last 7 year since I started with 200mm rotor I never felt the need for bigger rotor.

Like on MX or rally car on dirt road use smaller rotor than tarmac track car and motorBike on slippery surface to be able to modulate better brake power.

200mm compare to 220mm less unsprung weight, less gyroscopic effect, cheaper, less hard on pads ( if temp stay in control).

 

[Alexbn921]

If you have enough leverage ratio and heat resistance, then going to a larger rotor will not stop you faster. Traction is the limiting factor.

BUT

In practice larger rotors DO stop you faster. On a DH trail with soft grippy tires and high speeds.
1. Hand pressure is reduced and the lockup threshold falls into a more controllable area with less fatigue.
2. You can activate the available power quicker. 0.1 second faster at 20mph is 3 feet.
3. Heat management keeps the brakes more consistent overall. Consistency leads to shorter stopping.
4. Friction during steady state threshold braking tends to drop off from surface temperature rise and off gassing.

Too much power can lead to modulation problems and over slowing. The front and rear need different power thresholds, but some people need more rear thermal capacity.

Where you ride and what you ride, bike and terrain dictate the best overall setup. Also skill level and style.

Going to very aggressive pads(Trickstuff power) paired with 220mm rotors and saints brakes, feels like just barley enough. I can brake in a shorter distance more of the time and hit my marks better. The same setup would be overkill and maybe even troublesome on an XC bike riding flat ground.

 

[Alexbn921]

200mm compare to 220mm less unsprung weight, less gyroscopic effect, cheaper, less hard on pads ( if temp stay in control).

A 220 would always be cooler and therefore have less pad wear. Given the same rotor style was used, although the difference within a good temperature window would be very small.

 

[irie]

Am 78 kg. 2022 Alloy Trek Rail. Swissstop Catalyst Pro 220mm rotors front and rear paired with Shimano 6100 levers + 6120 calipers. As an ex motorcyclist use front and rear together most of the time. Single finger braking with great feel.

 

[Mars2]

I defenetly need to go back to 200mm as my 220 don’t have any color change compare to my ex 200 mm. Guideline from hope “ Disc size is important. A bigger size rotor will increase braking power but make sure you are generating enough momentum for the whole system to work at the optimal temperature. If not enough braking intensity, frequency and duration the system could remain too cool, and you won’t get the most out the brake pad, in this case a smaller rotor might produce more power. A good pointer is to look at the color of the disc just below the braking surface. Ideally it will be a light brown. Darker or showing a rainbow effect and you could benefit from a bigger size disc. No color means your rotor is too large and not reaching the optimum temperature.“

 

[Mars2]

If bigger was always better every pro dh rider should be on 220mm or even bigger ( Galfer 243mm) but they are not

 

[Mars2]

A 220 would always be cooler and therefore have less pad wear. Given the same rotor style was used, although the difference within a good temperature window would be very small.

grinding effect on rotor circonférence. for one wheel turn the pads will grind on the disc on a much longer distance on a bigger rotor than a small one. Specially true for people who drag brake. ( always a bit braking)

 

[Alexbn921]

grinding effect on rotor circonférence. for one wheel turn the pads will grind on the disc on a much longer distance on a bigger rotor than a small one. Specially true for people who drag brake. ( always a bit braking)

Then it would produce more friction. Instead you apply less force to the leaver to achieve the same level of friction as a smaller rotor. Energy dissipated is directly proportional to pad wear.

Another fact is that the size of a pad has no effect on braking performance. Larger pads just wear slower. This assumes that the temperature stays in an acceptable range.

 

[hansfrans]

It's actually the opposite. A smaller disc is easier to modulate as you'll need more force through the lever to stop the bike. If you have too much force through the brake then they feel "grabby" or like they're very on/off. That's also why you want a smaller brake on the rear than the front.

Downhill your weight is over the front wheel more, plus the bike is moving forwards, so when you brake the weight transfers forwards over the front wheel and off of the back wheel. As you have more braking being done by the front wheel you want a bigger disc to dissipate the extra heat and because all the weight is at the front you're less likely to lock up the wheel and it's nicer to have more power. At the rear there is less weight and so having a really powerful brake is likely to cause the wheel to lock up, also, there's less heat being generated at this end of the bike because all the weight moves forward under braking. As such, a smaller brake is better, as it allows for lower weight, better modulation and you don't generally need the additional heat dissipation.

Of course, if you're hammering really long descents on a hot day and overheating your brakes then sure, a larger/thicker rotor will help. I suspect very few people with 200mm rear rotors are overheating them though. Also, you can probably remedy it easier with different pads.

You're right about the big brakes stopping you quicker for the same amount of force applied to the lever though, but then who is out there riding that isn't able to just pull the lever a bit harder? I'd guess that we all "learn" how hard we can pull the brakes before they lock up the wheel and brake up to that point, regardless of how hard that means squeezing the lever. A small brake is just as capable of stopping a bike in the same distance as a large brake, it's just that with the large brake you will probably need to apply less force. However, the smaller brake will be easier to modulate, as you'll have to squeeze the lever harder to lock up the wheel, which means you're less likely to do so accidentally.

Unless you're regularly overheating your brakes or getting very tired braking fingers then the smaller option is probably better, for that additional modulation and reduced weight. (Otherwise bike manufacturers would just be throwing motorbike brakes on our bikes.)

It’s not about being or not being able to pull the lever harder.
You need to pull harder on the smaller brakes because they are not as strong as bigger brakes. That they can reach the same effect (locking the wheel) doesn’t make them as strong.
Also to me it cannot be correct to say it’s not a good thing when it’s easier to lock the wheel with a bigger brake.
Not only but especially when you go really steep down it’s easier to modulate your braking and controlling your steering when you have bigger discs, because you don’t need to apply so much force to you brake.
Theoretically it’s true that even a 100mm disc will be able to lock the tire but it would be very hard to control that brake and bike because it would need a lot power to pull the lever.
That’s why everybody (ok, almost everybody since I now learned that some people are seing this different) feels bigger discs as more powerful and easier to ride.
The easier modulation because of less force needed outweighs any negative as not warming up quickly enough, weight and so on.

 

[p3eps]

A different perspective... bear with me for a minute!!

Imagine you had a wheelchair wheel, with default handgrip / rail on it (which is pretty much at the outer edge of the wheel).

Imagine you somehow attached a second smaller handgrip / rail nearer the centre of the wheel.

Spin the wheel as fast as you can, and try using your gloved hand to stop it.

Is grabbing the inner or outer one going to be easier to stop the wheel?

It's going to take a lot stronger hand / arm to be able to stop the wheel spinning by grabbing the inner rail than the outer rail.

 

[irie]

A different perspective... bear with me for a minute!!

Imagine you had a wheelchair wheel, with default handgrip / rail on it (which is pretty much at the outer edge of the wheel).

Imagine you somehow attached a second smaller handgrip / rail nearer the centre of the wheel.

Spin the wheel as fast as you can, and try using your gloved hand to stop it.

Is grabbing the inner or outer one going to be easier to stop the wheel?

It's going to take a lot stronger hand / arm to be able to stop the wheel spinning by grabbing the inner rail than the outer rail.

Yebbut there's hydraulics involved with MTB brakes

 

[p3eps]

Yebbut there's hydraulics involved with MTB brakes

Principle is the same though - the hydraulics are going to have to work harder to grab and slow the inner rail than the outer rail.
I run 203/180 brakes with zero issue, but I understand the logic that bigger is more efficient.

 

[Bontee]

So,let me throw a spanner here.My bike runs 200mm rotors with xt twin piston calipers.My other bike (lighter) runs Hope X2 calipers (single piston) on 185 rotors.I love the feel of the X2s compared to the shimanos.So what would happen if I put the X2 calipers on the bike running 200mm rotors.I know I will have to pull harder but the X2s are very strong brakes.I also know they will run hotter due to the smaller pad size ,but in normal use ? Will it actually matter.
I am very tempted to try this out.I have never found either bike to be underbraked and feel there is little or no difference in braking traction (breakaway point) between the X2s on 185 discs vs the shimano twin pots on 200mm rotors……………….discuss

Small point but I always change the standard brake fluid for high temp racing fluid and have never had brake fade on either bike ever.

 

[RJUK]

If you have enough leverage ratio and heat resistance, then going to a larger rotor will not stop you faster. Traction is the limiting factor.

BUT

In practice larger rotors DO stop you faster. On a DH trail with soft grippy tires and high speeds.
1. Hand pressure is reduced and the lockup threshold falls into a more controllable area with less fatigue.
2. You can activate the available power quicker. 0.1 second faster at 20mph is 3 feet.
3. Heat management keeps the brakes more consistent overall. Consistency leads to shorter stopping.
4. Friction during steady state threshold braking tends to drop off from surface temperature rise and off gassing.

Too much power can lead to modulation problems and over slowing. The front and rear need different power thresholds, but some people need more rear thermal capacity.

Where you ride and what you ride, bike and terrain dictate the best overall setup. Also skill level and style.

Going to very aggressive pads(Trickstuff power) paired with 220mm rotors and saints brakes, feels like just barley enough. I can brake in a shorter distance more of the time and hit my marks better. The same setup would be overkill and maybe even troublesome on an XC bike riding flat ground.

Yes, I agree with most of what you're saying, and again, it seems people are getting the idea that I'm saying smaller brakes are better than larger ones, which isn't the case.

You've stated a very specific example of when a larger brake may stop you faster.

I would argue on point one that the difference between a 200mm and a 220mm rotor is going to make very little difference to hand fatigue unless you have weak fingers and are having serious issues by the end of a ride on 200mm rotors. I've never had anything larger than a 203mm rotor on my bike (until my current bike) and I was always able to brake fine by the end of a ride. Again though, this has nothing to do with the stopping distance - it's about rider comfort.

I'd also argue that activating the power quicker isn't really a thing and could be just as easily influenced by lever set up, bite point adjustment and general brake maintenance.

Larger rotors combat fade better. Absolutely. I've never disputed this. In fact, it's always been my point that reduced fade is the entire point of larger rotors, not reduced braking distances.

Point 4 just seems to be an extension of point 3.

I agree with the remainder of your post more - in that too much power an lead to issues with modulation. Adding power does not make modulation easier, it makes it harder. If 100% is the point at which your wheels lock up, then you want a brake that can apply more than that, to allow for some degradation in their braking ability, so you always have the power to lock the wheels. Let's say 120%, for argument's sake, even though the actual figure is likely much higher on all brakes.

Having a brake that can apply 500% of the power needed to lock the wheel will feel more on/off, because the power applied to the lever on the 120% brakes to threshold brake would immediately lock the wheel on the 500% brake. Then we move up to a 1000% brake and you'd have to lightly caress the lever... Anything more than that would see you over the bars in an instant.

(Percentages are juet for illustration.)

Of course, it's balancing act of having enough power to keep your hands comfortable without going so far as to make the brakes like a switch.

 

[RJUK]

A different perspective... bear with me for a minute!!

Imagine you had a wheelchair wheel, with default handgrip / rail on it (which is pretty much at the outer edge of the wheel).

Imagine you somehow attached a second smaller handgrip / rail nearer the centre of the wheel.

Spin the wheel as fast as you can, and try using your gloved hand to stop it.

Is grabbing the inner or outer one going to be easier to stop the wheel?

It's going to take a lot stronger hand / arm to be able to stop the wheel spinning by grabbing the inner rail than the outer rail.

It'll be easier to stop on the outer ring. But to make the analogy correct, you'd have to be able to stop the wheel immediately in either scenario (as all brakes, unless faulty, can lock a bike wheel immediately). Then ask yourself, if you grab the wheel in the inside or the outside, does one stop faster than the other? No, they stop ate a tly the same speed, you just need to grab the inner part harder than you would the outer part to get the same effect. It's an exaggerated comparison though, as it's similar to comparing a 200mm disc to a 29" disc.

Now imagine having a 29" disc on your bike. Would it have better leverage? Of course! Would it have better heat dissipation? Yes!

Well why haven't we all got them then? Because it's unnecessary and would make the brakes like a switch because of all that extra leverage (assuming the same brake levers). Plus, it STILL wouldn't stop us any faster! It would just reach the tyre's grip threshold quicker, leading to more lock ups.

 

[RJUK]

It’s not about being or not being able to pull the lever harder.
You need to pull harder on the smaller brakes because they are not as strong as bigger brakes. That they can reach the same effect (locking the wheel) doesn’t make them as strong.
Also to me it cannot be correct to say it’s not a good thing when it’s easier to lock the wheel with a bigger brake.
Not only but especially when you go really steep down it’s easier to modulate your braking and controlling your steering when you have bigger discs, because you don’t need to apply so much force to you brake.
Theoretically it’s true that even a 100mm disc will be able to lock the tire but it would be very hard to control that brake and bike because it would need a lot power to pull the lever.
That’s why everybody (ok, almost everybody since I now learned that some people are seing this different) feels bigger discs as more powerful and easier to ride.
The easier modulation because of less force needed outweighs any negative as not warming up quickly enough, weight and so on.

Sorry but this is all incorrect.

Big brakes aren't "stronger" than smaller brakes, we're talking the same levers and calipers here, the larger discs just afford more leverage on the hub, which means the same force in the lever results in a higher slowing force at the hub. (I know, potatoe - potato, but the point is that one isn't stronger than the other and having more leverage on the hub does not make you stop faster. If it did then rim brakes would stop you on a dime and discs would have never caught on.)

Why would it ever be a good thing to lock the wheel? (Unless you're doing trials.) Power is nothing without control. If locking the wheels is desirable then why even have a lever? Just fit an on/off switch. Modulation is key in a good brake. The more powerful the brake, the less modulation it has (Assuming the same lever). Between a 200mm and a 220mm the difference is likely to be small, but the more powerful a brake is, the more careful you have to be with your inputs to avoid locking the wheel.

This is probably even more pronounced when throwing yourself down something steep, as people tend to get death grip and pull the levers too much. On a weaker brake it's less of an issue as you're less likely to lock the wheels. On a really powerful brake a bit of death grip will likely see you over the bars.

Again though, I'm absolutely NOT saying that smaller brakes are better than larger ones. (Although is some instances they are.)

This all goes back to the original assertion that bigger brakes slow you faster. They do not. Assuming both the smaller and larger brakes are identical other than the size of the discs themselves and the bikes are otherwise identical, and assuming both brakes are working perfectly within the parameters of their operation, then both bikes would stop on the same distance.

The point of a larger rotor is heat dissipation to prevent brake fade. As such, larger discs will provide more consistent braking and resist fade for a longer period. This is important for heavier riders/bikes, sustained long downhills, hot climates, etc. and is the reason bigger brakes get fitted to performance cars.

A side "benefit" of the larger disc is increased leverage on the hub, which gives the feel of the brake being more powerful as it requires less force at the lever for the same leverage at the hub.

The downside to this additional "power" is reduced modulation, as that increased power makes it easier to surpass the grip threshold of the tyres.

If you want to stop your brakes overheating then fit larger/thicker discs (or uprated pads).

If you want to stop in a shorter distance you need to increase your grip (softer compound tyres/lower tyre pressures, etc).

 

[Mars2]

It’s always compromise. Right size rotor for surface grip/ tire grip/ heat dissipation needed ( ratio of riding speed vs grip)

The only thing make me laugh is when I see those guys with sport car that spend thousand on big brake kit and will almost never go much faster than speed limit , mostly drive on autobahn ( cold brake 99 % of the time) and think this will make them stop shorter distance than oem set up. is MTB going to go that way? Marketing make human brainless slaves

 

[Mikerb]

All braking consists of a force capable of reducing the momentum of a dynamic ( moving) mass. In our case that mass consists the combination of bike plus rider. So , assuming regardless size/thickness of rotors and 2 or 4 pot callipers, if the brakes on a bike are capable of seizing the wheel(s) with achieveable lever force then the 4 main factors affecting the a bility to decellerate or stop are

1. rider plus bike mass................and equally important, position of the dominant mass...which is the rider
2. Maintenance of tyre contact with the ground ( largely by the suspension)
3. Tyre grip (relevant to surface type)
4. Braking skill/technique ( where and when to brake, reading trail surface, modulation, body position)

Agreed thicker/larger rotors help deal with heat build up as do sintered pads .A heavier mass (E bikes) is likely to result in more heat build up which will result in glazing of most common pad types. Pad/disc interfaces that REQUIRE heat ( performance pads/carbon brakes) provide very little braking when not heated!!

ps If size and thickness of rotor were a defining factor RIM BRAKES would be the most powerful!!

 

[Mars2]

Only the coward brakes. So just remove those stupid things

 

[p3eps]

It'll be easier to stop on the outer ring. But to make the analogy correct, you'd have to be able to stop the wheel immediately in either scenario (as all brakes, unless faulty, can lock a bike wheel immediately). Then ask yourself, if you grab the wheel in the inside or the outside, does one stop faster than the other? No, they stop ate a tly the same speed, you just need to grab the inner part harder than you would the outer part to get the same effect. It's an exaggerated comparison though, as it's similar to comparing a 200mm disc to a 29" disc.

Now imagine having a 29" disc on your bike. Would it have better leverage? Of course! Would it have better heat dissipation? Yes!

Well why haven't we all got them then? Because it's unnecessary and would make the brakes like a switch because of all that extra leverage (assuming the same brake levers). Plus, it STILL wouldn't stop us any faster! It would just reach the tyre's grip threshold quicker, leading to more lock ups.

I agree with everything you’re saying…
I’m 85kg’s in all my gear, and a 203mm upfront and 180mm at the rear are more than sufficient for my needs.
The hydraulics take care of the pressure, and a good set of pads do the gripping.

If I was 110kg’s, I would probably need to pull my lever that little bit harder to slow down or even lock my brakes… and perhaps having a 220mm / 203mm would help.

Yes, I agree my analogy is ridiculous as a 29” disk wouldn’t ever be a thing… and that the difference between 203 and 220mm disks is probably next to nothing… but it was purely to illustrate that there is a difference.

 

[RJUK]

All braking consists of a force capable of reducing the momentum of a dynamic ( moving) mass. In our case that mass consists the combination of bike plus rider. So , assuming regardless size/thickness of rotors and 2 or 4 pot callipers, if the brakes on a bike are capable of seizing the wheel(s) with achieveable lever force then the 4 main factors affecting the a bility to decellerate or stop are

1. rider plus bike mass................and equally important, position of the dominant mass...which is the rider
2. Maintenance of tyre contact with the ground ( largely by the suspension)
3. Tyre grip (relevant to surface type)
4. Braking skill/technique ( where and when to brake, reading trail surface, modulation, body position)

Agreed thicker/larger rotors help deal with heat build up as do sintered pads .A heavier mass (E bikes) is likely to result in more heat build up which will result in glazing of most common pad types. Pad/disc interfaces that REQUIRE heat ( performance pads/carbon brakes) provide very little braking when not heated!!

ps If size and thickness of rotor were a defining factor RIM BRAKES would be the most powerful!!

Exactly! If it was all about size we'd all still be on rim brakes. It's also why initially trials riders stuck with the old faithful Magura HS33's... A hydraulic rim brake makes it very easy to abruptly stop a moving wheel, which is what you need on a trials bike.

 

[RJUK]

It’s always compromise. Right size rotor for surface grip/ tire grip/ heat dissipation needed ( ratio of riding speed vs grip)

The only thing make me laugh is when I see those guys with sport car that spend thousand on big brake kit and will almost never go much faster than speed limit , mostly drive on autobahn ( cold brake 99 % of the time) and think this will make them stop shorter distance than oem set up. is MTB going to go that way? Marketing make human brainless slaves

You say that, but on the autobahn they are probably fairly useful. The mass of a modern heavy car, travelling well over 100mph and then suddenly needing to scrub off a lot of speed when somebody pulls out without looking properly...

But yeah, day to day little city runabouts can have smaller brakes and even drum brakes on the rear because for one emergency stop they're fine. Take them on a track and they wouldn't last 2 minutes.

Notice that car manufacturers never spec cheap tyres though - as that would drastically affect braking (and handling) performance. That's why even a Dacia will have tyres from a good brand.

That's why it's crazy when you see fairly new, fast cars and the owner has fitted some awful "Goodride" or similar Chinese budget tyres. Spend a ton of money on a car that accelerates, brakes and handles well, then ruin all of that by fitting cheap tyres to save a few quid. Bizarre.

 

[thewrx]

I think only 1 person really gave an answer I agree with. Qbec?

I would agree that rotors are a small part of the "braking better" solution, but they are important and will make incremental improvements on a stock setup; its kind of like swapping brake levers imo. If I really wanted to have "better braking" I would be looking for modulation (don't want to lock up the wheel lol) clamping force.

Lets assume you have good tires, at the right air pressure and your suspension is setup and what not, before you go down this journey.

First, check my riding style and adjust as needed, know how to weight transfer, understand your terrain, and limits of your bike and yourself.


Then....
clamping force - So I would find better calipers (2, 4, 6?) more pistons, radial mount, no flex, etc. and optimal pads (heat range/composition) for my riding style, also would be looking for 1/pad per caliper cylinder to reduce deflection, so in my case 4 pads/caliper.

modulation - correct piston matching between lever and caliper, adjust if needed (not mentioned very often, but seen with shiman/saint, shagura's, etc. and proper fluid along with a good bleed to eliminate any compress able air.

Now as I'm addressing the issues above, the rotors would be an obvious topic to address if I am looking to make the most out of my setup. My normal ebike/mtb setup is usually a 2-piece rotor upfront usually a 220-200, and 200-180 HD (essentially thicker, sometimes higher quality steel) 1 piece rotor out back (also helps with ebike magnet clearance).

Finally, there other little things I would make sure to address, like quality adapters if needed, proper break/bed-in procedure, lever adjustments, possibly new levers to improve ergo and leverage, good quality fluid, surface rotors slightly before install, and quality stainless lines (most bike hydraulic lines are stainless and not rubber, so usually not an issue on most systems).

Now if that still doesn't make me faster, because I'm confident I can slow/stop when needed, I should probably put the bike up and get a cage.

 

[Robstyle]

Bigger discs are great. Less finger power required and more resistance to fade...
But they warp easier and if you cook a set they're not always on the shelf. Theres added weight from extra adapters/rotor size and the extra fluffing to install stuff because of that. And all your bikes have to be the same if you wanna swap wheels.
In the end it was more of a pain than a benefit.

 

[hansfrans]

Sorry but this is all incorrect.

Big brakes aren't "stronger" than smaller brakes, we're talking the same levers and calipers here, the larger discs just afford more leverage on the hub, which means the same force in the lever results in a higher slowing force at the hub. (I know, potatoe - potato, but the point is that one isn't stronger than the other and having more leverage on the hub does not make you stop faster. If it did then rim brakes would stop you on a dime and discs would have never caught on.)

Why would it ever be a good thing to lock the wheel? (Unless you're doing trials.) Power is nothing without control. If locking the wheels is desirable then why even have a lever? Just fit an on/off switch. Modulation is key in a good brake. The more powerful the brake, the less modulation it has (Assuming the same lever). Between a 200mm and a 220mm the difference is likely to be small, but the more powerful a brake is, the more careful you have to be with your inputs to avoid locking the wheel.

This is probably even more pronounced when throwing yourself down something steep, as people tend to get death grip and pull the levers too much. On a weaker brake it's less of an issue as you're less likely to lock the wheels. On a really powerful brake a bit of death grip will likely see you over the bars.

Again though, I'm absolutely NOT saying that smaller brakes are better than larger ones. (Although is some instances they are.)

This all goes back to the original assertion that bigger brakes slow you faster. They do not. Assuming both the smaller and larger brakes are identical other than the size of the discs themselves and the bikes are otherwise identical, and assuming both brakes are working perfectly within the parameters of their operation, then both bikes would stop on the same distance.

The point of a larger rotor is heat dissipation to prevent brake fade. As such, larger discs will provide more consistent braking and resist fade for a longer period. This is important for heavier riders/bikes, sustained long downhills, hot climates, etc. and is the reason bigger brakes get fitted to performance cars.

A side "benefit" of the larger disc is increased leverage on the hub, which gives the feel of the brake being more powerful as it requires less force at the lever for the same leverage at the hub.

The downside to this additional "power" is reduced modulation, as that increased power makes it easier to surpass the grip threshold of the tyres.

If you want to stop your brakes overheating then fit larger/thicker discs (or uprated pads).

If you want to stop in a shorter distance you need to increase your grip (softer compound tyres/lower tyre pressures, etc).

It’s all wrong? So bigger discs don’t result in more leverage than smaller ones?

Same force on the lever will not result in more leverage?

Then I also have to say sorry, but you don’t know at all what you are talking about.

And then suddenly it is increased leverage on the hub:
“A side "benefit" of the larger disc is increased leverage on the hub, which gives the feel of the brake being more powerful as it requires less force at the lever for the same leverage at the hub.”
But then it just a “side effect” that “gives the feel” of being more powerful. Ridiculous. It is more powerful. At least you described the physical effect correctly this time.

If you want to stop in the same distance with lesser force to the brake lever while riding the same tires, you need a stronger brake aka larger discs.

 

[RJUK]

It’s all wrong? So bigger discs don’t result in more leverage than smaller ones?

Same force on the lever will not result in more leverage?

Then I also have to say sorry, but you don’t know at all what you are talking about.

And then suddenly it is increased leverage on the hub:
“A side "benefit" of the larger disc is increased leverage on the hub, which gives the feel of the brake being more powerful as it requires less force at the lever for the same leverage at the hub.”
But then it just a “side effect” that “gives the feel” of being more powerful. Ridiculous. It is more powerful. At least you described the physical effect correctly this time.

If you want to stop in the same distance with lesser force to the brake lever while riding the same tires, you need a stronger brake aka larger discs.

Where did I say larger discs don't provide more leverage? In fact I said the opposite.

It's not more powerful - in that the caliper isn't any stronger, it just has increased leverage from being placed further from the hub. I suspect we're saying the same thing in two different ways - you're just getting very upset about it for some reason.

Nobody ever said about stopping in the same distance with less force - you're changing the argument to suit you now. The argument has always been that larger discs don't stop you in a shorter distance.

Slowing down is all about friction between the bike and the ground. To slow down faster you need to increase that friction. If your brakes can lock the wheel then you already have the maximum stopping power available for your tyres. Putting a larger disc on there won't reduce your stopping distance, because the disc can't increase the amount of friction between the tyre and ground.
I've never said that larger discs are inferior though - larger discs are for better heat dissipation.

 

[RiderOnTheStorm]

The argument has always been that larger discs don't stop you in a shorter distance.

It seems this thread is going around in circle

Could we just agree that larger discs WILL stop you in a shorter distance, when the same force is applied to the levers

 

[steve_sordy]

I have just come across this thread and I thought it was interesting. I admire @RJUK for sticking to his guns and I am persuaded by his main points: that stopping quickly depends upon the tyres; smaller discs give more modulation.

I can see how his detractors may disagree because their personal experience says different; ie bigger brakes mean they stop quicker. But is it the bigger brakes doing the quicker stopping, or does it just feel quicker and/or is less effort? My personal experience has said that bigger brakes are better, because I sure as hell would not want to go back from my 200/200 combo to the 180/160 of my early years.

But I'm not comparing like for like. That 180/160 was on an XC hardtail that weighed next to nothing (and I was lighter too, and carried less kit)! It also had hard compound Maxxis Ignitor 2.1" x 26" tyres and I had zero difficulty locking them up with the basic Hayes Stroker Trail brakes. If it was possible to put my current tyres on that bike then I would probably have got by with 140/140 and still be able to lock up the wheels!

 

[RJUK]

I have just come across this thread and I thought it was interesting. I admire @RJUK for sticking to his guns and I am persuaded by his main points: that stopping quickly depends upon the tyres; smaller discs give more modulation.

I can see how his detractors may disagree because their personal experience says different; ie bigger brakes mean they stop quicker. But is it the bigger brakes doing the quicker stopping, or does it just feel quicker and/or is less effort? My personal experience has said that bigger brakes are better, because I sure as hell would not want to go back from my 200/200 combo to the 180/160 of my early years.

But I'm not comparing like for like. That 180/160 was on an XC hardtail that weighed next to nothing (and I was lighter too, and carried less kit)! It also had hard compound Maxxis Ignitor 2.1" x 26" tyres and I had zero difficulty locking them up with the basic Hayes Stroker Trail brakes. If it was possible to put my current tyres on that bike then I would probably have got by with 140/140 and still be able to lock up the wheels!

Thanks Steve! The thing is - I've been witness to this exact argument before on car forums. The boy racers all come in thinking bigger brakes = shorter stopping distances and the old boys quickly put them in their place and point out that basic physics shows that's not the case.

But some people just don't want to listen and feel the need to justify their shiny new thing, even if it contradicts physics.

Logically even, if both brakes can lock the wheels then how can adding more power to the brakes slow you any quicker?! Bigger brakes can't increase the traction at the tyres, so it's just physically impossible. Adding power will just make it easier to lock the wheels and thus less easy to modulate the brakes.

Having made this argument repeatedly here, I'm not saying that larger brakes are inferior, just that you need to understand what you're actually getting them for. Don't buy them thinking they will stop you quicker. Buy them because you want better resistance to heat fade or so that you have to put in less effort at the lever (possibly at the expense of ultimate modulation).

Anyway, it's all not worth falling out over. If anyone wants bigger brakes, buy them - it makes no odds to me.

 

[Alexbn921]

There is an optimum range of finger control. Pick a power level that lets you stay in that range.

Wheels and tires have a much bigger impact on how a brake feels then most people think. The flywheel effect of heavy tires, wheels and Cushcore significantly increase the braking requirements with zero effect on the traction limit.

Brakes that activate quicker stop you faster. More powerful brakes with bigger rotors usually have a faster ramp.

Steady state braking on very steep terrain requires lots of finger pressure and high thermal mass in the rotors. Optimizing this leads to less hand fatigue and more control.

Not all brakes can lock the wheel. This is especially true if you are already braking. Pads off-gas and the friction of the pads varies with temperature. The temperature at the point of pad/rotor contact is much much higher then the system overall temperature.

Leverage ratios can be variable and where you are in the leverage ratio effects modulation. This mostly applies to Shimano systems where having very little free stroke makes them feel very on/off.

If you need more braking like on a DH bike, then Bigger rotors will stop you faster and more consistently.
If you are on an XC bike less power will be faster as you have better control of the reduce energy requirements.

For me on my Kenevo, Sram brakes with 160mm rotors would NOT be able to lock the wheel and would overheat after a couple seconds of braking.