what should I expect from a rear brake

danlightbulb

My rear brake is very poor - well thats my perception anyway, which I want to check is correct.

I have replaced the pad as they were well worn, but there's still no stopping power.

They are V brakes on a decathlon bike. The pads were the standard decathlon ones now replaced with clarks ones.

The front brake I would describe as punchy, can feel it engage, can feel the deceleration. However the back brake I don't feel anything, and it gives no tactile feedback whatsoever.

Thanks

cooldad

Should be the same as the front. Either need adjusting or more likely, clean the rim.

danlightbulb

There doesn't seem to be anything mechanically wrong with it. The rims are clean enough, the cable is good, the adjustment is fine, its just I pull the lever as hard as I can, brakes are in contact with the rim, but there's no power there at all.

I can't even lock the rear wheel up when riding (obviously I don't try this on the front one lol).

It won't hold me still on a hill, whereas the front one will.

cooldad

Well I would say one of those things isn't.

danlightbulb

Its almost like its a leverage problem, thats how it feels, it takes much more squeeze on the lever compared to the front and thats zapping the power.

Is there anything you suggest I adjust?

cooldad

Not much to adjust
http://www.parktool.com/blog/repair-hel ... brake-type
Arm angle makes a big difference

danlightbulb

I have followed all these things before, the brakes are set up correctly, there's just no braking power there whatsoever.

NGMTB

Hi,
Take the brake cable inner out and reinstall it with it coated in grease.

gezebo

Personally if it's not a routing problem or setup then as mentioned I'd certainly go for cleaning the rim even if it looks clean.

Rubbing with a degresser and a sponge is a good way or even wire-wool (gently though!) and then a good rinse with clean water -Hose pipe if you are allowed! Try not to let the degresser run into the hub area though.

Hope it helps

paulmgreen

gezebo wrote:

Personally if it's not a routing problem or setup then as mentioned I'd certainly go for cleaning the rim even if it looks clean.

Rubbing with a degresser and a sponge is a good way or even wire-wool (gently though!) and then a good rinse with clean water -Hose pipe if you are allowed! Try not to let the degresser run into the hub area though.

Hope it helps

yes -definitely do all this.... Also I would take the tyre off and clean the rims with wet and dry ...... Then spray with disc brake cleaner .... And repeat!

If your rim looked clean but was actually contaminated (eg with silicon spray or similar) then the new brake blocks may still be contaminated. Either resurface them with a file .... Or replace again when you have one the above

The Rookie

You've not got a road lever on one side rather than linear pull? That makes the lever very wooden and gives little braking (although travel is long......)

danlightbulb

no, levers are the same both sides.

I have lubed the cable, no noticable difference and i have wiped the rim clean, not much residue on it really as i clean the bike quite often anyway.

I'm at a loss.

gezebo

Has it always been bad or was it good once?

danlightbulb

When the bike was new it was never as strong as the front brake, and the lever always felt a stiffer to operate than the front, but I could lock up the rear wheel whilst riding and it would hold me on a hill.

So now its definitely worse, but by quite how much I'm not really sure.

The pads that came off were worn down to the body, so its doing something, just nothing I can feel confident about.

The front pads are worn down too, replacing them tomorrow.

paulmgreen

When you say you clean it regular - what do you use to clean ???? Definitely try toclean the rims fully with brake cleaner and ribs then dry off

danlightbulb

Well I wash it after most rides, with normal soapy car wash stuff and hot water. Ive never applied any form of degreaser or silicone to the mech, all I use is a drop of chain oil so the rim can't be contaminated.

Nevertheless I shall thoroughly clean it once more to eliminate that as the cause.

Russell160

Are you cleaning the brake blocks shoes as well? They could have picked up contamination which still affects performance after you've cleaned the rim. This could explain why cleaning the rim isn't making much difference.
You could clean the rim then swap the brake shoes fom the front as a definitive test. If this improves things then it's definitely your blocks . If so, you can file down your blocks as suggested above or even better just use new blocks. Are they the same blocks front and rear? I would recommend Kool Stop blocks over Clarks.
I always clean rims with meths and cotton wool, you can really see the filth. Even a bit of oil thrown off the chain onto the rim or dripping down overnight can have a contaminant effect.

YeehaaMcgee

I always had this to a degree with V-brakes. I always put it down to the greater cable length allowing more cable compression effect.

twonks

In the dry a rear V brake should be able to lock the wheel quite easily if all is correct.

So, assuming it is set up correctly, not contaminated, not flexing any mounting locations and not simply bending the lever - it must simply be rubbish

If all of the above can be assured, then try swapping the calipers and pads front to rear and see if the front brake becomes weak and rear strong. If so then there has to be something wrong with the setup or rim. Swap the pads over but leave the calipers and see if the problem moves with the pads.

Basically keep going until you can pin it down to something.

However, my money would be on a rim being greasy as it is nearly always spilled on when lubing chains etc.

YeehaaMcgee

twonks wrote:

However, my money would be on a rim being greasy as it is nearly always spilled on when lubing chains etc.

True that. And virtually all degreasers leave a residue.

danlightbulb

I have stripped down the entire rear brake, cleaned and re-greased all the pivot points, cables and re-aligned all the pads etc. Its back to as new condition now and is adequate performance. I think I may be out growing the capabilities of these v brakes in my riding now which is why I believe it not to be powerful enough.

Yacoby

danlightbulb wrote:

I think I may be out growing the capabilities of these v brakes in my riding now which is why I believe it not to be powerful enough.

Really? I know on my old bike I could easily lock the rear wheel (It did take more force than on my current disk brake equipped bike).

Disk brakes just work in the wet and take less force to apply them.