Wisper rear brake adjustment

[the_killjoy]

I am having trouble adjusting the rear brake on my 905, the offside pad continues to rub gently on the rim when the brake lever is released. Although the brake arm can be easily moved by hand it doesn't 'spring' away from the wheel in the same way as the opposing pad.

The pad isn't jammed against the wheel but there is enough pressure to slow the wheel down. I notice there is a small allen screw which appears to be part of the spring assembly.

 

[Vikki]

It's a small crosshead screw on mine. Turn it clockwise to increase the spring tension pushes the brake arm away from the wheel. Or, turn the screw on the opposite brake anti-clockwise to reduce the outward tension on that side. Also, lubricate the mechanism and give them a wiggle to work the oil in. Remove any oil that gets on the rims. It's a balanceing act to get the arms springing away the same distance each and is the worst thing about V brakes.

Vikki.

 

[the_killjoy]

I took it apart in the end and greased the pivot, which definitely helped ~ I just wish the springs were stronger.

 

[aeromys]

I think the springs have three tension settings - if you take them apart there are three holes in the mounting plate and the spring can be positioned in any one of them during re-assembly.

 

[the_killjoy]

I thought the different holes were for setting the centering

 

[aeromys]

Oh! Possibly I didn't experiment, just put mine back in the same holes.

 

[Mussels]

OK, this evening I have been experimenting.
Failure 1
Firstly I borrowed a set of Shimano XT parallelogram brakes, if anything works these should. Unfortunately the brake pivots are not central to the wheel and the left hand side didn't have enough room so the pad hit the tyre.
Failure 2
I went back to the original brakes, oiled them all up and used the hole that gave most tension hoping that they would pull back and clear the wheel properly. There is a slight wobble in the wheel which I expect, it's a couple of mm so I expect that is normal. Now the setup, I set the calipers wide so that holding the brake lever to the bar only put light pressure on the rim. The problem was that when I release the pads hardly pulled back at all and the wheel wobble means both pads touch the rim in one revolution.
Conclusions:
1. The rear wheel isn't dished enough, the wheel was rebuilt by SJS who said they got the dishing as far over as possible but the design of the hub worked against them. I don't know what can be done here as we are a bit stuck with the design of hub, SJS drilled and put eyelets in mine and it is still not great. This is more of an inconvenience because I don't notice when riding and it only means I can't fit cantilever brakes.
2. The brake lever isn't well matched with the brake arms and the position of the brake hinges (if they were slightly lower then the pads would be a bit further up the lever and have more travel). I don't know what can be done here as I've shown that brake upgrades don't help, I guess we need some Wisper advice.

So after a couple of hours work I am back to square 1 but with new brake pads fitted.

 

[Wisper Bikes]

Brakes

Hi, I have forwarded a copy of this thread to Norman at Wisper Service for his comments.

All the best David

 

[Mussels]

Hi, I have forwarded a copy of this thread to Norman at Wisper Service for his comments.

All the best David

I see on the other thread you said the new levers had a greater pull on them, this will probably fix my problem of insufficient travel.

 

[Wisper Bikes]

Pulling power

Hi Mussels

Yes the pull is about twice that of the old ones.

Please email your address to miall@aol.com again and I will get this clip off to you. I don't store customers addresses here.

All the best David

 

[Cometxt]

Hi Mussels

Yes the pull is about twice that of the old ones.

Please email your address to miall@aol.com again and I will get this clip off to you. I don't store customers addresses here.

All the best David

Found two brake problems first unequal pull which 'the Killjoy' and 'Aeromis' refer to above. Apart from greasing I found that the return springs on each side were located in different tensioning holes. The screw to which 'Vikki' referes can then be used to tweak the adjustment. Equalising helped a lot.

Second was the lenght of pull, the new brake handles are a great improvement.

Regards
Cometxt