Author Topic: BMX-type U-brake on the front - broken return spring  (Read 1290 times)

BMX-type U-brake on the front - broken return spring
« on: 16 July, 2018, 05:01:10 pm »
One return spring has broken on the front brake on my clunker/town bike.

Said brake is a BMX/U-brake type.

I'd just replace it with a V brake, except that the posts don't have any bits to take the return spring (no plate with holes in it). Instead, there is a removable plate with a grooved flange *above* the post. This looks to be specific to the U-brake. Two bike shop mechanics sucked teeth at it and said I'd have to find a like-for-like replacement.

Best option I can think of is to find an old BMX with similar U-brake. Anyone have other ideas?
<i>Marmite slave</i>

Torslanda

  • Professional Gobshite
  • Just a tart for retro kit . . .
    • John's Bikes
Re: BMX-type U-brake on the front - broken return spring
« Reply #1 on: 16 July, 2018, 05:07:31 pm »
A U-brake isn't a difficult thing to find, my wholesalers keep them on the shelf. Not expensive either.

A picture is worth a thousand words - Well, at least it would help to visualise the current fitting.
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

LittleWheelsandBig

  • Whimsy Rider
Re: BMX-type U-brake on the front - broken return spring
« Reply #2 on: 16 July, 2018, 05:17:41 pm »
That bike's U-brake posts allows you to fit a U-brake (or old roller cam) brake. Many (all?) of them had adjustable spring tension without the end of a spring sticking into a hole. The springs were tightened with a spanner and locked in position when the central bolt was tightened. See the pictures at the top of https://www.sheldonbrown.com/canti-u.html
Wheel meet again, don't know where, don't know when...

Torslanda

  • Professional Gobshite
  • Just a tart for retro kit . . .
    • John's Bikes
Re: BMX-type U-brake on the front - broken return spring
« Reply #3 on: 16 July, 2018, 05:22:27 pm »
If the 'adapter' is bolted thru the fork crown then we just need to know the vertical distance between the hole in the fork crown and the rim. Then it's a cinch to find the correct drop side pull.

Or have I read it wrong...?
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Torslanda

  • Professional Gobshite
  • Just a tart for retro kit . . .
    • John's Bikes
Re: BMX-type U-brake on the front - broken return spring
« Reply #4 on: 16 July, 2018, 05:31:27 pm »
*Lightbulb moment*

This isn't a 'pit bull' type brake is it? The cable pulls a wedge between two rollers?

If it is, I've got one...
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

LittleWheelsandBig

  • Whimsy Rider
Re: BMX-type U-brake on the front - broken return spring
« Reply #5 on: 16 July, 2018, 05:33:09 pm »
A Pitbull would be a drop in replacement for a U-brake on an adaptor plate.

I've never tried but the Pitbull arms might fit onto U-brake posts. You'd still need the cable stop mounted somewhere.
Wheel meet again, don't know where, don't know when...

Re: BMX-type U-brake on the front - broken return spring
« Reply #6 on: 16 July, 2018, 05:36:25 pm »
it might well be the case that a pair of springs from a cheap V brake could be made to work with the U brake.

cheers

Torslanda

  • Professional Gobshite
  • Just a tart for retro kit . . .
    • John's Bikes
Re: BMX-type U-brake on the front - broken return spring
« Reply #7 on: 16 July, 2018, 05:37:54 pm »
Please put me out of my misery, I can't picture it.
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Re: BMX-type U-brake on the front - broken return spring
« Reply #8 on: 16 July, 2018, 05:44:55 pm »
U brake adaptor



they often have slots/holes in for return springs, but I think the one above doesn't have that.

The net result of using one of these things is that you have created an oversized centre-pull brake.... ::-)

cheers

Torslanda

  • Professional Gobshite
  • Just a tart for retro kit . . .
    • John's Bikes
Re: BMX-type U-brake on the front - broken return spring
« Reply #9 on: 16 July, 2018, 05:51:46 pm »
OK, got it.

So we go back to the suggestion of measuring the drop and fitting an appropriate sidepull instead.
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Re: BMX-type U-brake on the front - broken return spring
« Reply #10 on: 16 July, 2018, 08:26:44 pm »
It is on posts - no adapter

I doubt a sidepull would fit (apart from some of the really odd cheap BMX ones. I have 1.75" tyres.

Will try to get a photo posted up.
<i>Marmite slave</i>

LittleWheelsandBig

  • Whimsy Rider
Re: BMX-type U-brake on the front - broken return spring
« Reply #11 on: 16 July, 2018, 08:33:36 pm »
Just buy another U-brake (they aren't too expensive) and fit it. http://cycle-systems.co.uk/tutorial123/brakes-set-bmx-u-brakes-front shows how to adjust brake spring tension.
Wheel meet again, don't know where, don't know when...


Re: BMX-type U-brake on the front - broken return spring
« Reply #13 on: 16 July, 2018, 09:50:34 pm »
It is on posts - no adapter

ah... I assumed it must be adjustable in some way if you were considering a V brake.  V-brakes and U brakes require the posts in completely different positions; the only brake that will fit on fixed U brake posts is another U brake.

As I mentioned earlier springs from a cheap V brake might work though.

cheers