Tweaks to get some oomph from a V brake?

[LittleSkink]

Picked up a minty 24" wheel RockRider MTB for my eldest a while back. Its barely used but the brakes are not great - really soft, no bite

First I cleaned the rims and pads - no effect. Swapped the levers from the OEM plastic ones to a metal pair and it made no real difference either. Tried a new cable and outer to the front - same, no better

So I am unsure what to try next, dont have any cash for new calipers but I guess there is stuff I can do in the set up . . . maybe?

 

[RickTheUncivil]

Something is flexing or stretching.
Brake booster can help keep the bosses together, if the pads are bendy that's something you can fix by replacement. Looks like you have looked at stretchy cables. How about the actual cantis, plasticy ones might be bending rather than pulling together?

 

[greencat]

Brake booster? If the frame is flexing under heavy breaking it might help.

 

[FluffyChicken]

Re:

Boosters will not alter 'bite' that jsut means they are not working.
Only two things matter as there is little to go wrong.
(Assuming they are set up correctly*)

Pads and rims
Pads, buy some new ones. Cheap from somewhere like discobrakes.

Rims, other than clean them then bed the pads in there is not a lot you can do.

*I.e. cables, levers and brakes are all correct.

 

[hamster]

Try decent pads (Aztecs or Ashima), then make sure it's all worn in a bit. I reckon proper braking only really gets settled after around 50 miles in the dry.

 

[LittleSkink]

Something is flexing or stretching.

thats how it feels, frame is pretty solid alloy affair and rear shows very little flex

didnt think about pads, was planning to swap the washers round to bring the arms in - the pads are "as new" so reluctant to change them yet

 

[FluffyChicken]

Something is flexing or stretching.

thats how it feels, frame is pretty solid alloy affair and rear shows very little flex

didnt think about pads, was planning to swap the washers round to bring the arms in - the pads are "as new" so reluctant to change them yet

But if old 'as new' then they will need the surface worn down.

V's should be near parallel when setup.

Initial flex could be pads that are not set flat or correctly


Anyway, pictures !

 

[Fatal Swan]

One thing I don't think anyone has mentioned so far is the spring tension in the brake arms. On a few pairs of V-brakes I've had down the years (mainly XTR) the spring tension has gone slack over time and gives them a really dead, soft and powerless feel, a bit like you're describing.

To check whether that's causing a problem you could first try and screw the spring tension bolts in all the way on each arm (at least as far as that allows the arms to be aligned properly - you'll probably have to back off one side a little to get them aligned) and see if it improves performance at all in the way you're looking for. The other thing you could do is to reinstall the calipers with the spring pivot on the highest of the three holes on the frame bosses. That will make even a dead spring feel as tight as anything (and you'll have to back off the spring tension bolts again if you try that). On the front, forks don't usually have the three holes on the bosses so you probably won't be able to try that on the front. But the above you might get an idea of whether the springs are the problem - if so any cheap set of new calipers will be an improvement.

 

[02gf74]

Pads set up so when they contact rim are parallel and with some toe in, i.e. the front of the pad touches rim first. Put a credit card between pad and rim at rear when adjusting them.

Also clearance between pads when brakes not applied is a couple of mm so it doesnt need a lot of lever travel.

 

[hamster]

Daft question: are you positive that the replacement levers are for V and not canti?