Brake Rotor Size Advice

[jbrown15]

Good luck finding rotors larger that 180mm with Centerlocks. I ran into issues finding 200mm or 203mm rotors that I run on my non-ebike when I bought some new wheels a couple of months back. Ended up using adaptors so I could use 6-bolt rotors on my centerlock hubs.

In regards to using Hope 220 rotors, you should have no issues with clearance on the forks. I've used these with Fox 36, Rockshox Lyrik and Marzocchi Z1s. Your more likely to run into clearance issues with the rear brakes, where the post mounts on the frame and any adapters can interfere with the large rivet? that Hope uses to secure the brake surface to the aluminum carrier.

I can order 203mm Freeza centerlock rotors from Shimano right now, I know they have them in stock so I don't know what the issue would be? Maybe in your region they don't have stock, but I know I could order them today if I want to.

 

[schleprx7]

Maybe it was timing but was evening having issues finding centerlock rings. No one locally seemed to stock any centerlock options.

 

[Jackware]

Magura sell 203mm centre lock discs as well.

 

[urastus]

Good luck finding rotors larger that 180mm with Centerlocks. I ran into issues finding 200mm or 203mm rotors that I run on my non-ebike when I bought some new wheels a couple of months back. Ended up using adaptors so I could use 6-bolt rotors on my centerlock hubs.

In regards to using Hope 220 rotors, you should have no issues with clearance on the forks. I've used these with Fox 36, Rockshox Lyrik and Marzocchi Z1s. Your more likely to run into clearance issues with the rear brakes, where the post mounts on the frame and any adapters can interfere with the large rivet? that Hope uses to secure the brake surface to the aluminum carrier.

I upgraded my back brake from 180 to 203 and it's centrelock. There was a fair bit around here in Australia. I bought the
Shimano XTR MT900 Ice-Tech Centerlock Disc Rotor - 203mm. One of my rides has huge downhills and although I was trying to minimise braking, just grabbing before big hits, both ends were screaming by a certain point. The bigger ice tech didn't seem to make any difference, despite all the logic of a bigger rotor, but the pads are lasting longer, which does make sense. One annoying thing about the ice tech is that it often needs straightening - I didn't have that problem with plain stainless steel. Also, it is very soft and easy to bend - I hardly touch it when straightening. I'd really advise on a non ice tech bigger rotor - I wouldn't go that path again.

 

[jbrown15]

I upgraded my back brake from 180 to 203 and it's centrelock. There was a fair bit around here in Australia. I bought the
Shimano XTR MT900 Ice-Tech Centerlock Disc Rotor - 203mm. One of my rides has huge downhills and although I was trying to minimise braking, just grabbing before big hits, both ends were screaming by a certain point. The bigger ice tech didn't seem to make any difference, despite all the logic of a bigger rotor, but the pads are lasting longer, which does make sense. One annoying thing about the ice tech is that it often needs straightening - I didn't have that problem with plain stainless steel. Also, it is very soft and easy to bend - I hardly touch it when straightening. I'd really advise on a non ice tech bigger rotor - I wouldn't go that path again.

Hmmm, it's funny because I've had the exact opposite experience with the Shimano rotors. But I've only used the RT86 203mm Ice-tech rotors, which have held up way better than the Sram steel rotors that I was using before these. I scorched and warped those in less that two rides.

Maybe I'll have to try out a Hope 220mm front and 200mm rear next.

 

[urastus]

Hmmm, it's funny because I've had the exact opposite experience with the Shimano rotors. But I've only used the RT86 203mm Ice-tech rotors, which have held up way better than the Sram steel rotors that I was using before these. I scorched and warped those in less that two rides.

Maybe I'll have to try out a Hope 220mm front and 200mm rear next.

that aluminium core sandwich is never going to be as strong or as stiff as straight stainless. It actually seems to warp from heat - as though it can't handle it as well as straight stainless steel, which kind of makes sense. One of those things that looks good in theory. Admittedly I only have trouble with it on those big downhill runs which I've been avoiding while it's wet. For normal riding it is trouble free. I wonder if down hill riders use these?

 

[jbrown15]

that aluminium core sandwich is never going to be as strong or as stiff as straight stainless. It actually seems to warp from heat though - as though it can't handle it as well as straight stainless steel, which kind of makes sense. One of those things that looks good in theory. Admittedly I only have trouble with it on those big downhill runs which I've been avoiding while it's wet. For normal riding it is trouble free. I wonder if down hill riders use these?

I'm told that a bunch of the Pros running Shimano brakes run the center lock Freeza rotors, Shimano has also stated they have no plans to offer the Freeza rotors in a 220mm version and feel like the current 203mm size do more than an adequate job of staying cool under heavy braking loads. So how knows.

 

[urastus]

Well, an update to that shitty ice tech form over function rotor I had on the rear. I was forever straightening it, and after a while bit the bullet and bought an el cheapo shimano rt-64. Glued some magnets on and haven't had to look at it since.

 

[jbrown15]

Well, an update to that shitty ice tech form over function rotor I had on the rear. I was forever straightening it, and after a while bit the bullet and bought an el cheapo shimano rt-64. Glued some magnets on and haven't had to look at it since.

I guess maybe I've just had good luck with my Icetech rotors, I had 203mm front and rear. I'm a solid 265lbs and I'm pretty hard on brakes and I still didn't warped either of my rotors. I recently decided to try out Galfer 223 rotors front and rear along with their ebike pads and I'm really loving them so far. Made my XTR brakes just that much better. Being a little thicker at 2mm compared to 1.8mm makes a nice difference with heat too.

 

[urastus]

I guess maybe I've just had good luck with my Icetech rotors, I had 203mm front and rear. I'm a solid 265lbs and I'm pretty hard on brakes and I still didn't warped either of my rotors. I recently decided to try out Galfer 223 rotors front and rear along with their ebike pads and I'm really loving them so far. Made my XTR brakes just that much better. Being a little thicker at 2mm compared to 1.8mm makes a nice difference with heat too.

It's probably the model I got - it is just woefully soft (9100). There's a lot of soft aluminium in that sandwich.

 

[jbrown15]

It's probably the model I got - it is just woefully soft (9100)

I had the SM-RT86's

 

[urastus]

I had the SM-RT86's

I had to buy locally - the rt64 is what they had in stock. I knew I'd be paying a lot more. I also ordered one online as a backup in case of a good ding. My front 203 which came standard is an even cheaper shimano rt30 - I've never touched it either. Lots of steep, long, technical downhill near where I live (approx. 1.8km each ride).

 

[Waynemarlow]

Don’t mix up rotor size and stopping power with pad compound / force per sq cm and heat dissipation. A 180 rotor with a medium compound small pad in say a two pot brake can be just as effective as a larger pad running a harder compound in a 203 rotor. Simple mathematical calculation will support that.

Some caliphers are better at getting heat transfer away from the pads, than others.

The front does the majority of braking. Under normal braking circumstances, the bike tries to rotate around the front axel, lifting the rear and thus giving less contact force on the back tyre, which means you have to modulate the rear brake, thus virtually every vehicle out there has smaller brakes on the rear.

It’s all about matching your requirements to your needs, for me the old go to of 203 / 180 with a 2 pot on the back using a medium compound does all I need.

Also a lot of people complain of there brakes failing on longer stopping sequences, first thing to ask is do they spray there bikes with something like GT40 after washing them down. The heat in the pads boils the GT40 that is now in the pads as soon as you first turn the disc, and brings it to the surface and lubricates the pad until it turns into carbon from the heat. Carbon in itself is a wonderful lubricant at high temperature.

 

[urastus]

Don’t mix up rotor size and stopping power with pad compound / force per sq cm and heat dissipation. A 180 rotor with a medium compound small pad in say a two pot brake can be just as effective as a larger pad running a harder compound in a 203 rotor. Simple mathematical calculation will support that.

Some caliphers are better at getting heat transfer away from the pads, than others.

The front does the majority of braking. Under normal braking circumstances, the bike tries to rotate around the front axel, lifting the rear and thus giving less contact force on the back tyre, which means you have to modulate the rear brake, thus virtually every vehicle out there has smaller brakes on the rear.

It’s all about matching your requirements to your needs, for me the old go to of 203 / 180 with a 2 pot on the back using a medium compound does all I need.

Also a lot of people complain of there brakes failing on longer stopping sequences, first thing to ask is do they spray there bikes with something like GT40 after washing them down. The heat in the pads boils the GT40 that is now in the pads as soon as you first turn the disc, and brings it to the surface and lubricates the pad until it turns into carbon from the heat. Carbon in itself is a wonderful lubricant at high temperature.

I understand most of the accepted theory - for mtb I tend to disagree with this, much of the time. On awesome rock slab or on the road, front brake is king. Where I ride it is mostly loose over hard and steep up or down, so the rear gets used most. I usually drop my bum hard toward the back wheel and roll my ankles back for hard braking - otherwise it's mostly modulating the rear in sketchy areas.

I haven't played with pads. I understand the concept. All my stuff is pretty low end but effective. The rotor and chain ring are the only things I've upgraded - the rest is up to me

We're in Derby, and have been for nearly two weeks now. Riding most days - all I do is blast out the calipers with air mattress pump and fine nozzle pre ride. Admittedly it isn't generally as steep or as loose as home, so I do get to use the front more, especially on these near vertical rock slabs

 

[GrandPaBrogan]

I understand most of the accepted theory - for mtb I tend to disagree with this, much of the time. On awesome rock slab or on the road, front brake is king. Where I ride it is mostly loose over hard and steep up or down, so the rear gets used most. I usually drop my bum hard toward the back wheel and roll my ankles back for hard braking - otherwise it's mostly modulating the rear in sketchy areas.

I haven't played with pads. I understand the concept. All my stuff is pretty low end but effective. The rotor and chain ring are the only things I've upgraded - the rest is up to me

We're in Derby, and have been for nearly two weeks now. Riding most days - all I do is blast out the calipers with air mattress pump and fine nozzle pre ride. Admittedly it isn't generally as steep or as loose as home, so I do get to use the front more, especially on these near vertical rock slabs

We have very similar riding styles (or riding mindsets). I'm not a racer and I can't even begin to imagine what extreme advanced braking techniques involve. But like you, on fast or steep descends my weight is shifted off and behind the saddle to various degrees depending - and so the front/rear brake bias is dynamic and ever changing. On paper mixing or not mixing rotor sizes to attain 'balance' might make sense, but out on the trail things for me are reactive and spontaneous - so I don't see the front and rear brakes having any direct interdependency necessarily. If I need to scrub off some speed along corners or sketchy slippery conditions, my go to is the rear brake... just a dab here and there. If I really need to stop hard, I use the front AND the rear but only on a straight line. Maybe I don't have enough skill to be using the front around a corner because I've had too many face-plant experiences when the front tyre wipes-out.

Back when MTBs were 26" wheels, I like to use 180 at the back and 203 at the front - otherwise the rear locks out too easily. Four pots were STRONG and modulation is up to me. But now that my eMTB have 27.5" wheels (and heavy), I use 203 rotors front and rear. But, I miss the ol' brute stopping power I used to get from smaller 26" tyres. The only time I might consider mixing rotors is if I ever go mullet. With a 29" up front I would use a 220+ rotor to "even up" the braking leverage discrepancy between a big tyre up front and a smaller tyre down the back.

 

[urastus]

We have very similar riding styles (or riding mindsets). I'm not a racer and I can't even begin to imagine what extreme advanced braking techniques involve. But like you, on fast or steep descends my weight is shifted off and behind the saddle to various degrees depending - and so the front/rear brake bias is dynamic and ever changing. On paper mixing or not mixing rotor sizes to attain 'balance' might make sense, but out on the trail things for me are reactive and spontaneous - so I don't see the front and rear brakes having any direct interdependency necessarily. If I need to scrub off some speed along corners or sketchy slippery conditions, my go to is the rear brake... just a dab here and there. If I really need to stop hard, I use the front AND the rear but only on a straight line. Maybe I don't have enough skill to be using the front around a corner because I've had too many face-plant experiences when the front tyre wipes-out.

Back when MTBs were 26" wheels, I like to use 180 at the back and 203 at the front - otherwise the rear locks out too easily. Four pots were STRONG and modulation is up to me. But now that my eMTB have 27.5" wheels (and heavy), I use 203 rotors front and rear. But, I miss the ol' brute stopping power I used to get from smaller 26" tyres. The only time I might consider mixing rotors is if I ever go mullet. With a 29" up front I would use a 220+ rotor to "even up" the braking leverage discrepancy between a big tyre up front and a smaller tyre down the back.

I've got a mullet - but I rarely lock up the rear. Where I am now, I rode down a rock slab and the rear skitted a bit I made a mental note to lay on the front much more next time - the luxury of grip It seems that most folk go through rear pads before front pads - well according to LBS. Just the extra cooling factor is a biggy for me.

 

[04fuxake]

The front does the majority of braking. Under normal braking circumstances, the bike tries to rotate around the front axel, lifting the rear and thus giving less contact force on the back tyre, which means you have to modulate the rear brake, thus virtually every vehicle out there has smaller brakes on the rear.

True, although you can dramatically change the weight distribution to counteract this on a bike.