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rear wheel lateral movement - advice pls!

by bechdan
Wed, Jan 15, 2020 14:51
3

Ive had to run my rear brake fairly loose this past year or so (maybe a little longer I cant remember) because I get wheel rub on the brakes during hard efforts. Its not generally an issue most of the year but now its wet and dirty I need more braking power.

Ive checked its not the wheel itself as Ive got another wheelset and both are true and well maintained, as are the brake calipers and pads and cables.

Ive checked there are no cracks in the frame (Focus Cayo carbon) and the QR is done up tight.

Before resigning myself to the probability its just frame flex and I cant do anything about it, is there anything else I should check?
Ta.

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3 comments

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hawkinspeter | 5 years ago
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Looks like you've discounted the most obvious causes - QR slipping, wheel out of true and bearing/hub movement. Bizarrely, you can get brake rub whilst applying lots of force if the wheel is particularly stiff - have a read of this: https://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.html

I don't know how you'd fix that without getting different wheels with more spokes though.

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bechdan | 5 years ago
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All sensible suggestions, but no its not the brake, im quite fastidious about making sure they work and correctly centered.

No lateral movement on light pressure only firm. Both wheelsets have cartridge bearings and no play by feel in the 'axle'.

Spokes all feel evenly tensioned (by hand, I dont have a spoke meter but am quite comfortable with tweaking nipples). One wheel is a 28h and the other is a 24h and well within my weight spec.

 

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bobbinogs | 5 years ago
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I know you say you have checked the wheel but it is still a possibility. I reckon it could be either build/spoke flex or perhaps play in the bearings/axle pre-load.  With the wheel in position, grab it at the rim and see how easy it is to flex.  If it moves freely for a small bit then that will probably be pre-load play (which is easy to fix with the right tools)...or perhaps it moves/flexes evenly under pressure, which could mean that you have a flexy wheel because it is by design (too few/incorrect/poor spokes, etc.)...or that the tension just needs adjusting.  Be warned, tension adjustments could be a slippery slope if you are inexperienced and you may end up wishing you had never started!

You mention another set of wheels, if they are OK when you ride, then fit them and do the same test.  If both wheels are the same then it could well be the frame, or the fact that you are simply pushing too many watts smiley

One other thing to check though is the brakes.  May sound silly but brake cable travel can be badly affected by the weather during a ride and it can be quite a shock to check your brakes whilst waiting at the top of a hill to find that the movement is down to just a few mm whereas at the start of the ride they were springing back a treat.  The back brack is very prone to this due to crud building up in the small outer cable feeding into the brake calipers.  I recently had a similar issue, componded by an iffy cable, on my winter bike.  I changed the cable /outer and lubed, reset everything, brake rub went away.

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