Rotor sizing

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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ParisCarbon
Posts: 1092
Joined: Mon Feb 05, 2007 5:39 am
Location: Winnipeg Canada

by ParisCarbon

Hey guys,
Question on rotor sizing.. Ive got my 2016 Stevens cross bike at the shop with post mount brakes.. they are R785 brakes.. I bought Ice99 140 mm rotors to install.. the shop just got back to me and said they are too small and need a min of 160mm... Ive got pics of Van Der poel's bike with RT98 140mm rotors... did Shimano change the sizing between the rt98 and rt99 rotors? Is a 140 RT98 a 160 RT99? Stevens also told me the 140mm would fit 2 years ago when I got the thing... weird...
Thanks

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FIJIGabe
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by FIJIGabe

Why did they say the bike needed 140's? Did they give an explanation, or just said it needed it and left it at that? I wouldn't compare pro bikes to consumer bikes - although the products are supposed to be available to the consumer market, often times, they aren't. That said, if Stevens told you a 140 rotor would work, and it doesn't, I would call them and ask if there's anything special you need to put on the bike to make it work.
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ParisCarbon
Posts: 1092
Joined: Mon Feb 05, 2007 5:39 am
Location: Winnipeg Canada

by ParisCarbon

They said it would work, and I had ordered a set with the wheels.. installing them, theres no way it would work..Ive got a pic of MVDP bike from that era with the same brakes and 140 rotors... it does look like the mounting posts are shorter though....

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ms6073
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by ms6073

ParisCarbon wrote:
Fri Aug 10, 2018 3:29 am
Ive got a pic of MVDP bike from that era with the same brakes and 140 rotors... it does look like the mounting posts are shorter though....
That is because MVDP's mechanic most likely used a facing tool to mill down the posts in order to position the calipers to handle 140 mm rotors. As for Steven's response, most likely they assumed you were either asking about the current generation of cross frames that incorporate Shimano's flat mount brake standard or were unaware of the customization of the frame in question. In the top image is MVDP's bike which compared to a 2015 consumer version of the Stevens Super Prestige Disc in the other image, it seems pretty apparent that the post mount was highly modified to work with 140 mm rotors:

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ParisCarbon
Posts: 1092
Joined: Mon Feb 05, 2007 5:39 am
Location: Winnipeg Canada

by ParisCarbon

Yeah.. I got 160mm on order today... place had em on sale.. now Ive got 4 brand new 140mms for sale.. mounted, but never used!

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