Trek Rail 7 brake mount question

[Philly G]

Hi everyone! I have a 2020 Trek Rail 7 (alloy) I'm looking to upgrade my brakes to 220mm rotors. Does anyone know the post mount size of the actual frame (i.e. the minimum rotor size, with the caliper bolted directly to the frame post mounts without an adapter). I need to know this to figure out what adapter I need for my new rotors (Hope). I've looked up the fork, Rockshox say it has a 180mm post mount, so I'm guessing the frame is the same , but could be 183mm. If anyone could confirm that would be awesome !

 

[EuanS2]

The frame is Post Mount 180

 

[Philly G]

Thanks @EuanS2 !

 

[Stihldog]

I’m not familiar with the hope 220mm rotor.
The frame for the Rail 7 and 9.7 is designed for a 180mm rotor. With some adapters a 203mm rotor is installed with a 4piston calliper. With a 220mm rotor the correct adapter is required. Ensure the rotor circumference lines up with the brake pads.

I’ve installed several 220mm Magura rotors, brake levers, master cylinders, 4 piston callipers and hydraulic lines on the Rail 2020-21. The stopping power is very noticeable for an eMTB. If this mountain didn’t have the steep and long descents a 203mm rotor would be good. But a 220mm rotor is so much better. Apparently the 220mm rotor has been approved for the front fork but not for the rear triangle. The jury is still out (to much torque?). My neighbor has the same bike (rail9.7) and we both have Magura 220mm f/r. His rear triangle cracked shortly after I installed these Magura 220mm rotors. IMO his riding style and aggressiveness caused the small crack in the Carbon lower triangle. Mine has been fine with the 220mm rotors.

 

[Philly G]

Thanks @Stihldog , I have the alloy frame so should be no issues with getting extra braking forces, frame cracking etc. My only concern was whether the 220mm would actually fit, I spoke to Trek and was told no, but plenty of people here have fitted it no issues at all

 

[Stihldog]

Thanks @Stihldog , I have the alloy frame so should be no issues with getting extra braking forces, frame cracking etc. My only concern was whether the 220mm would actually fit, I spoke to Trek and was told no, but plenty of people here have fitted it no issues at all

The 220mm rotor will fit with the correct adapter. I believe that Trek is being cautious when a 220mm is fitted to the rear. (Understandable). They don’t want any warranty issues. However our front brakes are fitted to a Rockshocks fork. I understand that they have given the “ok”.

 

[EuanS2]

I was using a 220 on the rear of my alloy rail and tbh, I ended up going back to a 203 as the 220 just felt like to powerfull especially with MT7 brakes, 203 just feels perfect for my 83kg weight (I still use 220 on the front)