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dk2

Small rear rotor on street trial frame?

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Hi anybody who rides 140-160mm rear rotor  and has enough brake power? Just wondering if a 4 piston brake would be strong enought with smaller rotor. The bennefit would be more ground clerance. And in teory there should be less flex in rotor & less weigt..

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10 hours ago, dk2 said:

Hi anybody who rides 140-160mm rear rotor  and has enough brake power? Just wondering if a 4 piston brake would be strong enought with smaller rotor. The bennefit would be more ground clerance. And in teory there should be less flex in rotor & less weigt..

What’s the main problem you are having with rotors? I haven’t used anything smaller then 203mm with a 4 piston caliper with Red EBC pads which works as a great setup. 

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There are a number of street frames that come set up for 160 rotors and it would put less stress on many parts of the bike/wheel, but at the end of the day, the rotor is still a lever. The bigger the lever, the stronger the braking force. If you're just starting out or you're not very heavy, try the 160; you can always easily upgrade later. Once you get into rolling drop gaps, you're gonna want the 203s.

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I’ve been using an xt 4 pot with 160 rotor with trial tech pads and it feels more than powerful enough for me, as I side hop left I do like the fact it is tucked up out the way more than bigger rotors. Not sure the flex or weight is going to be much different though if you are looking for those to be impacted...

Edited by Matt24.

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13 hours ago, John Shrewsbury said:

What’s the main problem you are having with rotors? I haven’t used anything smaller then 203mm with a 4 piston caliper with Red EBC pads which works as a great setup. 

Hi john Dont know if i have a problem ;-), just wanted to hear if there where people riding smaller rotors. im 82kg 180mm rotor & running shimano zee 4 piston brake (never slips, but i think 140-160mm could be fine to)

-1 getting it out of the way i for when i bail of the bike (etc tailwhips , i tend to land behind the bike and sometime cut my leg on rotor.)  

-2 less flex = less change of pad rub

-3 more ground clerance 

 

well gues only option is to try it out.

 

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1 hour ago, dk2 said:

Hi john Dont know if i have a problem ;-), just wanted to hear if there where people riding smaller rotors. im 82kg 180mm rotor & running shimano zee 4 piston brake (never slips, but i think 140-160mm could be fine to)

-1 getting it out of the way i for when i bail of the bike (etc tailwhips , i tend to land behind the bike and sometime cut my leg on rotor.)  

-2 less flex = less change of pad rub

-3 more ground clerance 

 

well gues only option is to try it out.

 

Running that setup won’t be a problem. I have a zee brake on my bike for the rear and it’s been great. Also I’m running a 203mm Shimano Deore XT floating rotor. Maybe if you still want power maybe try trialtech or like myself Red EBC pads. I find a rotor like that one has more material on it compared to any other rotors so it has more bite, a lot of rotors have big holes so they cool down going fast but for trials you don’t need that. It’s why I don’t run hopes or cheap rotors.

Edited by John Shrewsbury

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I was riding a 160mm on the rear with mt5 callipers and trialtech pads for the last while
Very rarely had any issues with a lack of power although I wasn’t doing anything too big and don’t weigh much either.

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Speaking as someone running 203's who doesn't really need to be running 203's...

I was on 180mm rotors for a while, and they worked reasonably well (Ben Travis is still on 180s and does some big lines, so they certainly do the job) but there's just something you get from running larger rotors.  I don't think it's necessarily just a confidence thing, but the feel of it is quite a bit different.  How aggressive the bite is is very noticeable, and if you're riding some more tech stuff (awkward angles/edges) then that surplus of power becomes more apparent too.  I noticed the increase in power much more than I ever noticed the difference in weight, and brakes are one of the parts of my bike I'm happy to sacrifice a bit of weight on to improve performance.

What I'm getting at is that a 160 will probably 'work', but I doubt it'll really feel that great or be overly confidence inspiring.  For the sake of a fairly marginal amount per rotor and a negligible difference in clearance you're not really getting much else out of the bargain.  A well set up brake, even with 200mm rotors, will still feel stiff - I think the reduction in power you'd get from a relatively small rotor like a 160 would be more obvious than any marginal change in rotor stiffness.  You might get a bit less rotor clang if you land a spin hard I suppose.

The biggest problem will be compatibility though.  A lot of frames now come with brake mounts in a +20mm/180mm Post Mount position, so even if you wanted to run a 160mm rotor you couldn't.  Some still come with a regular IS/160mm Post Mount setup but even with that you wouldn't be able to run a 140mm, although they're probably doing you a favour there :P 

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One thing to remember is that any movement in the pads gets magnified the smaller the rotor gets. What I mean is there is less noticeable "flex" with larger rotors and rear wheel moves feel more accurate.

I'm probably explaining this badly but small rotors = more wheel movement when brakes are locked....large rotors = less movement. 

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3 hours ago, Ali C said:

One thing to remember is that any movement in the pads gets magnified the smaller the rotor gets. What I mean is there is less noticeable "flex" with larger rotors and rear wheel moves feel more accurate.

I'm probably explaining this badly but small rotors = more wheel movement when brakes are locked....large rotors = less movement. 

i get it...explanation is fine..

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