Hi,

Can anyone confirm how (or where) brake "drop" is measured? Is it between the centre of the fixing bolt and the centre of the brake block? Or to the bottom of the slot for the brake block? Or between some other points.

My bike measures 42mm from centre of fixing to centre of brake block fixing (with 27" wheels, so it'll be 46mm with 700c assuming similar rim).

I'm trying to pick up some decent calipers for the bike, and need to make sure they'll fit. At this stage I'm not sure if short drop brakes will fit.

Thanks, Tony S

I believe you are correct in that it is measured from the center of the bolt to where the center of the pad would be on the rim. What I'm not sure of is whether all (or the majority at least) of manufacturers use the same guidelines, pretty sure most do though.

Cheers. I've just checked the two types I've been offered. One is "short" defined as 39-47mm, and the other "standard" defined as 47-60mm. From two different sources, which doesn't help.

Measure from the center of the brake mount to the center of the brake surface on the rim/center of the brake shoe. Here's a link to Sheldon's site, scroll down to the nice pic:
https://www.sheldonbrown.com/gloss_ra-e.html#reach

It looks like the "short" (39-47mm) will work for both 27" and 700c (42mm. 46mm) in your case. That would be fine if you don't need fender clearance. However, I looked in my Sutherland's 3rd Edition and didn't find any brakes with exactly those precise dimensions for long and short models. Not saying they're wrong, just that it's not what Sutherland's says. What are the makes and models offered?

Sidepulls:

Shimano "short" seems to be 39-49, and "standard" 47-57, though I have some 600 calipers that will reach 59 or 60.

Campagnolo Record and other vintage "short" is usually 42-52, and 47-57 for the "standard" reach. Newer models are somewhat shorter for "short".

Suntour seems to follow the Shimano ranges.

Centerpulls:
Weinmann 610 is 61 mm to the "max" end of the brake pad slot, while the 750 is -- guess.

You should be OK with just about anybody's short reach brakes, unless it's one of those weird Dia-Compe "Aero Gran Compe" things with the eccentric bolt and the non-standard brake shoe block -- those are really short reach: max 43! eBay sellers are often wrong about the reach of calipers they're selling, or they don't measure, and you have to ask them.

I am not so sure that Sheldon's diagram is really how the manufacturers figure reach. Sutherland's has clear diagrams that show simple vertical drop to the "reach" point, not measured on the angle from bolt to center of brake shoe face.

Modolo Professional, supplier quotes "short" 39-47mm
Weinmann Carrera, (different) supplier quotes "standard" 47-60mm

Those are both too close to your "sweet spot" for comfort -- at the end of the range for both. I'd look for some different brakes.