Brake block adjustment

mattgardiner

Hiya,

Anyone any ideas for the following problem:

I bought a bottom of the range Forme bike last winter so that I didn't need to subject my summer bike to the salty roads. One of things that never felt that great on the Forme were the Tektro brakes (possibly more likely to be the pads rather than the brakes themselves).

I've recently upgraded my summer bike and retired the old one to a permanent turbo trainer bike which meant that the 105 brakes that were on that with new pads could be moved over to the Forme.

I've done the swap and they are working much better than the old ones but there's a niggle. At maximum extension on brake block adjustment neither is quite low enough to line up with the wheel rim perfectly. When you apply the brakes there's maybe 1/2 to 2/3 of the block that will be putting pressure on the rim and the rest is above the rim. Looking at the old blocks the same was true with the Tektros and the pads are worn over 2/3s and then the other 1/3 is just a lip that has been rubbing on the tire rather than wheel so it's not just a case of different size brakes (I was sure that they were all compatible anyway.

So, the question I'd love some help with is; Is there any way to adjust for this type of thing or is it just a problem that is probably associated with cheap frame?

Thanks in advance.

matt

Wheelspinner

You can get calipers with longer "reach", as in, the arms are longer so the pads can sit lower. I think "standard" calipers are a max of about 50mm drop from mounting bolt centre line to lowest setting of blocks in the arms, and the long reach ones go up to about 58mm or a bit more.

Typically an issue with frames/forks which are designed for people to possibly install mahooosive tyres, which require more frame clearance, so the calipers can be a bit short. The 105's will be "standard" and yoru old Tektro's will be long reach I'd guess.

You can get Shimano long reach calipers: http://www.chainreactioncycles.com/Models.aspx?ModelID=74105

They may not be significantly better than the Tektros though. Are your old ones the same as these? http://www.chainreactioncycles.com/Models.aspx?ModelID=72628

mattgardiner

I think that it's unlikely that either of the calliper sets that I have are these long reach ones as the old blocks wore unevenly with a massive lip at the top. I'm pretty sure that they are the set that you've shown in your post.

That longer set are probably just the ticket. I'd imagine that in a perfect world they will be nowhere near as good as the 105s but in a comparison between 2/3s of a pad or a whole pad making contact with the rim I'm sure that whole pad would win every time.

Wheelspinner

You definitely want the whole pad contacting only the rim, otherwise when you apply brakes the top part of the block will rub the tyre sidewall.

This Is Not Good.

Does seem unusual that the original brakes would not have fitted correctly - you sure the pads were at the limit of adjustment on the original Tektro brakes? They may have worn badly, but would be surprised if the calipers were the wrong type altogether for the frame from the manufacturer.

Just for reference, Tacx make a nifty little tool to help set up brake pads easily. It has a preset toe-in taper for the pads too:

http://www.chainreactioncycles.com/Models.aspx?ModelID=75821

paul_mck

As above, got stranded 30 miles into a 110mile ride as one block was too high and had formed a sharp lip as it wore away. This rubbed the sidewall of the tyre eventually creating a small hole. 2 punctures later I discovered the problem and had to patch the tyre with tube patches and insulating tape to finish the ride.

lesson learned!