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Jnr's got a new bike which has a u-brake at the back. It did go through a gyro but he's 7 and would never use it so it's just a straight cable to the straddle and u brake. Only prob is it's really hard to pull the brake lever to get the brake on. It's fine for an adult but for him it's tough so he tends to jump down off the bike to stop it. Not ideal in an emergency situation! Previous bike had a pedal back rear brake and a front lever which was fine. Just this one I can't seem to make it "easier" for him to pull. It's been 30 + years since I faffed with BMX's. It's a new cable, and new lever. Any ideas?
Wow, not seen a U-brake in decades. Are the arms moving freely on the bosses? There would be a build up of paint on them.
*edit
Seems they're quite common on bmx bikes.
Yeah I took the lot off and cleaned it all up. Guess it's cos he's only got ikkle hands and never had a rear brake on the old bike to build up any real finger power.... Yet.
Suppose MTFU, 7 year old!
My lads has a salt moto u brake on his, it cost around £25 if I remember right for the full setup, works surprisingly well and is nice and easy to press.
Spring tension is usually set in a similar way to canti's - theres a helical spring in the arm, you set the tension by pushing the arms away from the rim and nipping up the bolt that holds them on the stud. The further away they are the greater the spring tension/force required to get the brake to hit the rim. Unless its an Odyssey Springfield brake with the spring across the tops of the arms, think that one can't be adjusted.
Same issue here and struggling also to find brake levers that are small. Have some Hoy kids v brake levers on his mountain bike, which have really small reach, but the u brake levers are a fair way away from the bars.
Separate issue but if you can find levers that are smaller, might make the issue easier? And if you do find levers let me know what/where!
the u brake levers are a fair way away from the bars.
Can you not adjust the reach with a grub screw? If there isn't one - It's easy enough to drill and tap a small hole to add a reach adjust screw - I've done it previously on a set of levers.
I think U brakes require levers with more pull like canti and road stuff. If there is a V-brake lever on right now that's why it's hard the pull. Check if it's V or canti.
If the thingy where the cable attaches is farther from the pivot point it's for a V-brake, if it's pretty close it's a canti lever.
Sort of like this:
[img] 
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Tektro makes small levers for kids for both V and canti brakes.
Less pull. V brakes have more pull as greater mechanical advantage.
Check cable routing & quality, but brakes on kids bikes are often crap, their hands are too wee to pull enough cable with enough force.