Brake callipers not long enough to allow adjustment of pads

Question

I upgraded the standard Tektro brakes on my SE Lager to Shimano 105s. The braking performance is vastly improved. I also have Charge Plug wheels, rather than the stock wheels.

However I've noticed that there's not quite enough adjustment in the calipers to position the pads correctly. Even at the lowest position in the caliper arms, the pads are still very slightly too 'high' and overlap the upper curve of the rim.

Is this a problem? Is there anything I can do to solve it?

lantius · Accepted Answer

Those pads do look ever-so slightly too high on the rim, the main danger being that any slight vertical eccentricity could result in the pad contacting the tire and causing a blowout.

There are two main solutions:

Firstly, you could use a round file and simply file out the bottom of the slot slightly to increase the clearance.  This works best if you only need a very small amount of additional reach and are willing to accept permanently modifying your brakes.

Secondly, you could buy a set of brakes with a longer reach.  The Shimano 105mm calipers are 39-49mm reach; if you instead purchase some higher-quality dual pivot calipers that are 47-57mm reach you'd have plenty of room for adjustment and should be able to achieve equally good braking capability.

Mr-swiss · Answer

I have just had to do the same thing with ultegra brakes on my Giant Ocr C1. Filed them down so theres only a millimetre or so at the bottom. Working well so far. Only needed to adjust the rear so at least ill have my fronts if they fail :-/

Answered by Mr-swiss on August 18, 2021

Criggie · Answer

Yes - there are several ways to alter the relationship of the caliper to the rim, but they all have downsides of adding flex or more complexity to the brake system.

Drop the pads down  The suggestion of filing has been made, that that's okay if you only need a millimetre.  Depending on the beefiness of the metal, you may not have a lot remaining.  Enter the offset brake pad holder:

These simply change the relationship of the pad to the bottom of the caliper.
Downsides

They can rotate in place.  Since the braking force is not through the single fixing bolt, there is a torque applied.  This might rotate the pad holder under aggressive braking.  I suspect the left side of the bike would be most at risk.  Mitigate by using thread lock and torque.

The holder might interfere with the tyre. Here the top of the holder touches the sidewall under braking:
^{From https://www.bikeforums.net/classic-vintage/1112364-650-bdop-cautionary-tale.html}
So this rider ended up grinding some relief into the rear of the holder. Risk is that as the brake pad wears, this will touch the tyre again causing quiet sidewall damage and risk a blowout.

Also mechanical advantage is decreased.  As the pads get further from the pivot, the force applied to the rim will decrease, resulting in less braking effect.

Another answer is to lower the entire brake caliper to be lower by dropping the brake-bridge mounting hole with an offset adapter.

Downsides This would be a neat solution, but there's potential for the whole caliper to flex under braking.  Also this increases leverage on a single small mounting bolt, so make sure its a good one.
Here's a home-made version of the same:

Brake callipers not long enough to allow adjustment of pads

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