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Discussion Starter · #1 ·
I'm 175 lbs, XC riding, some racing. At what weight do you think there is no advantage to 140mm rear rotors? Thinking of just making a switch.
 

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bbgobie said:
I'm 175 lbs, XC riding, some racing. At what weight do you think there is no advantage to 140mm rear rotors? Thinking of just making a switch.
I'm 180 - 182 and switched from a 180 f/r [Alligator Windcutters] to a 160f/140r setup [Alligator Windcutters] this season. So far in the training and three races I have been in it has been plenty of rear brake. 180 on the rear was way too much for my needs. But I live in the Midwest, so no long mountains to descend.

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Depends a lot on your riding style. I wouldn't think it's so much a power issue (easy to lock up rear wheel on almost any brake) as it is a heat dissapation issue. If you're the kind to drag the rear down long descents then I wouldn't, but at your weight and riding style I would guess that you'd be fine with 140 in the rear.
 

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Considering the front brake typically takes about 2x the braking force of the rear, a smaller rotor should be fine. Around here in Michigan we don't have sustained hills to really heat up rotors, but when I did some riding in Montana with 160 rotors front and rear, the front would start to turn blue and the rear would not. I have thought about trying a 140 rotor on the back but so far have not gone for it.
 

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How do you fit a caliper to bite a 140mm rotor?
 

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You would use a front 160mm IS-PM rotor for the rear. The front IS mount is 20mm farther from hub than the rear IS mount.
 

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Discussion Starter · #9 ·
THanks guys

I'm gonna try it out.

Yes, as mentioned use a front IS adapter on the rear.
 
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