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<p>Went out on my Cervelo c3 the other day. After riding down Kirkstone Pass every time I pedal hard there’s a rubbing noise from the rear disc when my left leg’s near the bottom of its stroke. It’s never done this in 18 months. Been back to the shop to be fettled but it’s still doing it. They tightened the through axle and trued&nbsp;the wheel slightly. Anyone out there with a theory?</p>

<p>Mike &nbsp;</p>

<p>&nbsp;</p>

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9 comments

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Drinfinity [182 posts] 1 week ago
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<straw clutch> Pad wear leading to pistons out further than usual, and getting stuck out, so less clearance? Then pad is detecting slight flex in frame.

Callipers moved slightly on mounts? </straw clutch>

 

 

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hawkinspeter [3502 posts] 1 week ago
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I'd be thinking of pads/disc alignment. Check the disc isn't warped and maybe re-align the caliper.

If you put the bike on a stand (or even *THE HORROR* turn it upside down), then when spinning the back wheel you should be able to get your head in a position to eyeball the gap between the disc and the pads. A light surface or piece of paper put the other side from your head will sometimes make it easier to see. If the gap is nicely consistent and about 1mm or so either side of the disc, then the alignment is spot on.

If the alignment is good, then I'd be looking for anything that could shift the position whilst pedalling. Rear wheel bearings could be a suspect.

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Mikehudson [7 posts] 1 week ago
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Pad/disc alignment seems spot on. Bearings were checked at the shop and found to be ok. It only manifests when putting the power down, ie when introducing a twisting force into the frame. It was absolutely fine until the first time I stood on the pedals after a fairly fast descent. Looks like a back to the shop job. I don’t suppose you can break a thru ankle? They seem pretty substantial to me. 

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hawkinspeter [3502 posts] 1 week ago
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Mikehudson wrote:

Pad/disc alignment seems spot on. Bearings were checked at the shop and found to be ok. It only manifests when putting the power down, ie when introducing a twisting force into the frame. It was absolutely fine until the first time I stood on the pedals after a fairly fast descent. Looks like a back to the shop job. I don’t suppose you can break a thru ankle? They seem pretty substantial to me. 

A thru-axle should be pretty tough. You'd certainly not snap it in half, but the thread on the end could get fouled up, I suppose. You'd notice if the thru-axle was faulty when removing it and then putting it back in place. Also, I wouldn't expect a thru-axle to be able to slip/move around if it's tightened correctly.

If the wheel bearings are all fine, then maybe there's an issue with the frame?

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Team EPO [197 posts] 1 week ago
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bit of cleaner often does the trick next stop change the pads 

https://www.amazon.co.uk/Muc-Off-Disc-Brake-Cleaner-400ml/dp/B002MXKGZC/...

 

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ktache [1509 posts] 1 week ago
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I noticed yesterday that Decathlon had it for £8.99.

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CXR94Di2 [2552 posts] 1 week ago
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grab the wheel at the rim with boths hands on opposite sides. Push and pull to see if you can hear or feel flex in the hub. If no flex then its alignment of caliper/pads or rotor bent. Last resort, extremely unlikely there is something wrong with the frame-crack or weakness in stays

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huntswheelers [177 posts] 1 week ago
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R8000 per chance...

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Swiss Tony [3 posts] 1 week ago
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huntswheelers wrote:

R8000 per chance...

is there a known problem with R8000 then?