Biggest rear rotor for Rail?

[Philly G]

Everyone seems to be running 220 on the back of the Rail just fine. I was on the phone to Trek today, was told 203 max size, 220 might work fine in a straight line but would rub the chainstay when cornering due to frame flex. Any damage not covered by warranty etc. Nobody has had any problems at all with the bigger disc rubbing on the frame?

 

[dixie600mhz]

Magura 220mm on mine front and back and no problems at all. Works perfect.

 

[Stihldog]

Everyone seems to be running 220 on the back of the Rail just fine. I was on the phone to Trek today, was told 203 max size, 220 might work fine in a straight line but would rub the chainstay when cornering due to frame flex. Any damage not covered by warranty etc. Nobody has had any problems at all with the bigger disc rubbing on the frame?

I agree. 220’s for the rear are selling out everywhere. The only incident that I have seen is my neighbour’s cracked lower left triangle. The LBS talked to Trek also about this also. It’s very very likely that his riding style cracked the triangle. I cannot see how braking with a larger rotor could cause this.

Almost any type of brake and any size of rotor can stop your rear tire very quickly. But during a long decent the 220’s, along with larger calliper and 4 pads will dissipate heat and prevent most brake fade. After a long decent I can hammer on the brakes and I will stop. I don’t worry anymore if I’ll be able to stop.

My only experience is with Magura f/r with 220’s, but I’m sure most 220/223 rotors, regardless of brand, are designed to stop a heavier bike after a long decent.

 

[Doug Stampfer]

Everyone seems to be running 220 on the back of the Rail just fine. I was on the phone to Trek today, was told 203 max size, 220 might work fine in a straight line but would rub the chainstay when cornering due to frame flex. Any damage not covered by warranty etc. Nobody has had any problems at all with the bigger disc rubbing on the frame?

Phil what's the feedback on the bigger front disc? I was wondering as I negotiated a steep drop corner trying not to go over the bars whether a bit of brake fade might be a good thing?

 

[Philly G]

@Doug Stampfer I haven't tried bigger rotors yet. I read an interesting article about running a bigger rotor on the rear than the front Ending the rotor size myth – Why you should have a bigger brake rotor at the back than the front | ENDURO Mountainbike Magazine I don't know if I'm going to go that way, but the way i ride, I tend to use the back brake more, so the article does make sense to me, so yes what you say makes sense, a bigger rotor up front could give me too much braking power and just cause the front to lock up. The stock Shimano brakes do tend to be quite on/off though, whereas my Hopes have lots of modulation, so I might not find it too much of an issue

 

[Stihldog]

I really think it depends on where and how you ride. I just returned from Whistler where the trails we were riding were mostly single track and groomed. Switchback climbs and switchback descents. Completely different from the trails I’m used to. My 220mm rotors f/r were overkill. No way did I need 220mm rotors.
However, on Burke Mountian, the climbs and descents can be long and straight. I’ve used Shimano 203mm rotors and XTR brakes for almost a year. After switching to Magura 220mm f/r…well that was the answer. On a long straight descent I can stop when I need to stop. I don’t get the brake fade or heating issues that I did before. If I mostly rode switchback trails 203mm brakes and rotor would have that moment to cooldown.

For this area, 220mm rotors are selling out and getting hard to find. Our heavier bikes need to stop or at least slow down. My tree-hugging days are behind me now…I hope.

 

[Philly G]

I really think it depends on where and how you ride.

Yes, I agree, how you ride and what trails you ride, both important factors

 

[Doug Stampfer]

Yes interesting article. It doesn't sit right with my experience or style of riding though. My back wheel is constantly locked up with the slightest touch of the lever so I guess I'm over the front a bit more & the trails I ride never really allow me time to let off the brakes & build up any great head of speed & usually have sketchy surfaces - it's only really after a fresh rain that the tracks get into that lovely tacky surface.
I guess the goldilocks ideal for me is medium amount of bite but great heat dissipation.

 

[Philly G]

I guess the goldilocks ideal for me is medium amount of bite but great heat dissipation.

So brakes with more modulation paired with 220 rotors and sintered pads could be your ideal setup.

 

[Philly G]

I used the hope HBMP front and rear on my 9.8XT to go 200 to 220mm.

https://www.hopetech.com/_repository/1/documents/BrakeAdaptorChart2021.pdf

Do you have a 2021 9.8? I have a 2020 7 alloy, both frame and fork are 180 post mount, so I think Hope mount M is what I need to run 220s...but I think your bike has the Zeb which is 200 post mount....

 

[dixie600mhz]

Do you have a 2021 9.8? I have a 2020 7 alloy, both frame and fork are 180 post mount, so I think Hope mount M is what I need to run 220s...but I think your bike has the Zeb which is 200 post mount....

Hi Philly, yes I have the 2021 9.8XT with the Zeb. My originals were 200mm. I think the 220mm upgrade is one of the best bang for the bucks available. 220mm with metallic pads work really well.

 

[Philly G]

Hi Philly, yes I have the 2021 9.8XT with the Zeb. My originals were 200mm. I think the 220mm upgrade is one of the best bang for the bucks available. 220mm with metallic pads work really well.

Yes I'm sure I'm going to love the extra braking power, also less strain on the hands...I also tend to drag the back brake a bit, and I've noticed the rotor is a bit discolored, so it's obviously been getting a bit hot...but my appetite for bike parts is greater than my income so may have to wait a bit longer for this upgrade

 

[Doug Stampfer]

Thos of you who have gone to 220mm, Can I just buy a 20mm adaptor & add it on to the existing adaptor to bring it out to match or do I need to get a 43mm one? 2020 Yari 35mm forks.
It also seems that most of the available rear wheels have centrelock hubs. Has anyone found a way around this re the rear magnet?

 

[Philly G]

Thos of you who have gone to 220mm, Can I just buy a 20mm adaptor & add it on to the existing adaptor to bring it out to match or do I need to get a 43mm one? 2020 Yari 35mm forks.

I got confused over this too...for the 2020 Rail, both the frame and fork are Post Mount 180mm. This is the minimum rotor size, meaning if you take off your adapters and bolt your calipers directly to frame / fork, you'd be running 180mm rotors. So the adapters you need are post mount 180 - 220mm, these ones should do the trick

Brake adapter - Post to post

Post-to-Post brake adapters are for mounting Post type disc calipers to Post type frames/forks. The adapters come in a number of different sizes, be careful to select the correct one! Each adapter comes with washers and bolts as per the product photos. Adapters should be used to adapt from your...

outspokencycles.co.nz

 

[WilkyWay]

Thos of you who have gone to 220mm, Can I just buy a 20mm adaptor & add it on to the existing adaptor to bring it out to match or do I need to get a 43mm one? 2020 Yari 35mm forks.
It also seems that most of the available rear wheels have centrelock hubs. Has anyone found a way around this re the rear magnet?

You need QM45 adaptor front and rear for 220mm rotors.

 

[Stihldog]

The QM 45 adapter is the correct front and rear adapter for the 220mm Magura 6-bolt rotor. Do not stack adapters to achieve the proper fit. The 2020 Rail I have came with a Yari fork setup for a 180mm rotor but an adapter allowed a 203mm rotor. (Suitable for eMTB’s). Like @WilkyWay said, QM 45 adapter from Magura works.
However, NSB (North Shore Billet) also make an adapter that works, 40mm. I use one of each, only because it was all I could get at the time. All the other 220mm rotor and MT7 brakes I’ve installed have NSB 40mm adapters.
North Shore Billet is located in Squamish BC but they ship everywhere as far as I know.
A fork other than a Yari style may require a different size adapter.

Just ensure the fit and pad-to-rotor alignment is correct. (The cameraman was a little shaky) Both types of adapters are identical except for that one bolt

 

[Doug Stampfer]

Thanks for your replies. We don't get a lot of Magura over here - they are just starting to slowly filter in. Can't get any galfer discs either.

 

[Doug Stampfer]

I got confused over this too...for the 2020 Rail, both the frame and fork are Post Mount 180mm. This is the minimum rotor size, meaning if you take off your adapters and bolt your calipers directly to frame / fork, you'd be running 180mm rotors. So the adapters you need are post mount 180 - 220mm, these ones should do the trick

Brake adapter - Post to post

Post-to-Post brake adapters are for mounting Post type disc calipers to Post type frames/forks. The adapters come in a number of different sizes, be careful to select the correct one! Each adapter comes with washers and bolts as per the product photos. Adapters should be used to adapt from your...

outspokencycles.co.nz

Thats a great price - most of the ones I saw were about $50.00. I will match them up with these rotors - also the cheapest I found

SRAM Centreline Brake Rotor / 6-Bolt

The new Centerline Rotor was designed to keep the center of friction consistent throughout rotation thereby minimizing vibration offering consistent performance and a quiet ride. Available in 160/170/180/200mm. Hub Interface: 6 Bolt

www.thehubcyclecentre.co.nz

It seems going down the mullet path that getting my hub rebuilt as a 27.5 wheel will be the chepest option. The price of rebuilding it back to a 29 if I don't like it works out cheaper than trying to get a 6 bolt hub rear wheel anywhere over here.

 

[Philly G]

@Doug Stampfer yes those adapters are extremely good value...im told that store will soon be stocking Galfer rotors, which may be cheaper than the Sram centerlines...im looking forward to your impressions post-mullet!
edited to add, BikeInn have 223mm Galfers for $150 for the pair including shipping to NZ

Galfer Wave E-Bike 2.0 mm brake disc | Bikeinn

Buy Galfer Wave E-Bike 2.0 mm , Brakes from Bike parts for only 32.99 €. Find bike deals in Bikeinn | Fast delivery

www.tradeinn.com

 

[Doug Stampfer]

@Doug Stampfer yes those adapters are extremely good value...im told that store will soon be stocking Galfer rotors, which may be cheaper than the Sram centerlines...im looking forward to your impressions post-mullet!
edited to add, BikeInn have 223mm Galfers for $150 for the pair including shipping to NZ

Galfer Wave E-Bike 2.0 mm brake disc | Bikeinn

Buy Galfer Wave E-Bike 2.0 mm , Brakes from Bike parts for only 32.99 €. Find bike deals in Bikeinn | Fast delivery

www.tradeinn.com

Jeez your google fu is far superior to mine. I've already pulled the trigger on the other discs.
Can you find me a rear wheel now please

 

[Philly G]

@Doug Stampfer my Google-fu may be good but I'm no magican...rear wheels seem hard to find, maybe us Kiwis have gone mad for mullets?

 

[Doug Stampfer]

@Doug Stampfer my Google-fu may be good but I'm no magican...rear wheels seem hard to find, maybe us Kiwis have gone mad for mullets?

Yes I thought I might be onto a winner with these as they're coming from a respectable brand store until I read the review of the formula hubs

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