Mounting recessed bolt rear brake on standard frame

I've just got hold of a new brake set (c/o WjPrince), but my frame has the older 6mm mounting holes.

For the front this isn't a problem, as I can always drill out the hole to 8mm, but for the rear brake (I ride a single speed) I cant fit a drill in because the seat tube gets in the way.

Has anyone had to sort out this problem before? Any ideas on a solution?

Was just reading this earlier today:

http://sheldonbrown.com/calipers.html#recessed

Is it of use?

I've just drilled out the whole of the rear bridge before and it's been fine.
There is another thread about this and people have said they used a drill bit in a pair of mole grips to make just one side larger by hand... make sense?

Hey Miyagi.
Good to meet you the other day.

As I cycled away it occured to me that you might have this problem.
What I have done in the past is use the front on the back and the back on the front, securing the bolt up the inside of the fork rather then threading through completely. The rear (front calliper) will show more thread and can be secured with the bolt against the bridge. Not the prettiest solution but works fine.

or you can get busy with the drill if you're feeling brave.

You can buy flexible drill bit drives - a bit expensive for a one-off job but if you do a lot of DIY they're really useful for getting abrasive wheels into tight corners and stuff like that. They have small chucks (I think 8mm would be about the biggest... check before you buy) and are only for light duty use though.

What i've done for now is drill out the front fork to fit the front brake, and its working fine. Got the old rear brake on at the moment.

@Garnett, I had a look at that article and the backwards mounting looks interesting, but has anyone tried this? I was a little wary, because once I drill the bridge I wont be able to use my old rear brake.

@ WjPrince, sounds like a decent idea, but I'm not sure how you would go about fixing the bolt inside the fork? How would you hold the nut from inside?

You would have to take the wheel off and go up inside with a pair of needle nose pliers.

Just done this too. I drilled through both walls from the back and got lucky with some concave washers from the pile of bits, one of which got the 8mm treatment too. Not ideal, but works.

@36x18, was this done with the front brake on the rear like wjprince suggested? or did you manage to make it work with the shorter bolt rear brake?

No, it's a rear Dia-Compe BRS 202, using a 13.5mm allen 'nut'.

There is a danger that the whole thing will pivot under braking, but it won't go far if it does.

I did what 36/18 did but had a spare front brake so used that with a nut instead of the recessed end.

I've also drilled out a bridge by going in at various angles then using the drill bit in mould grips method.

you can drill right through bridge if you have something to form a 'bush' over the brake end of the drilling.
Otherwise its likely the brake caliper will shift when you tighten it up and never be aligned with the rim. If that happens, the funny concave washers can help to an extent.

I'm doing up my old track bike as a fixie for road use. It's an old track frame, probably from the late 70's or early 80's. I managed to find some old Shimano 600 brakes that look great but the rear one is not long enough. I have some options. Drill the drop another 2mm's, which would be enough. Bad idea? Only use the front brake. Bad idea or good idea? Get another brake even though it won't match? The frame would have been built for 27 inch wheels (and would not have been used with brakes anyway). I'm very very pleased with the bike so far. This is the final piece to the jigsaw.

If it's a fixie, it doesn't need a rear break.

@slimandy, I used a pair of Weinmann centre-pull brakes when I did a 70's conversion replacing 27" with 700c.

Thanks for those replies. The problem is I need a different size on the back than the front so whatever I use will not match, though I can get close. The frame would have been built for 27 inch wheel but the forks are for 700c. The drop on the front is about 45~50mm but on the back is about 60mm. That said, I am tempted to use two brakes anyway because I bought the levers and the cable clips and I think it would look nice. I've never ridden a fixie myself; I'm only doing up it because it's a nice frame and its going to waste. I'll probably sell it when it's done so I wondered what more knowledgeable people than me thought. I had some Weinman brakes that were more knackered than I realised, I bought some dual-pivot brakes not realising they'd have recessed bolts, then I bought some Shimano 600's - very nice bujt the back one is 2 or 3 mm's short. I don't know if it makes sense to drill out the difference? Maybe it would weaken them?

You can use a round needle file to elongate the slot in the caliper arm, depending on how much meat there is at the end. There's normally enough for a couple of millimetres. Using pads holders that are properly adjustable can also win you enough jiggle room to clear the tyre wall safely.

If it's a fixie, it doesn't need a rear break.

Having a rear brake on a 'fixie' is entirely down to rider preference. A rear brake will save your knees.

Yes, I think thats a good call. I'll try that first. thanks.

Having a rear brake on a 'fixie' is entirely down to rider preference. A rear brake will save your knees.

Ha! I wouldn't want anyone to hurt their knees. Mine are almost worn out! I last rode this bike at Herne Hill when it was still a tarmac track, about 28 years ago.

i have a pair of 27" rims, they are Wolber polished alloy 36h from the 70/80's.
i had the opposite problem wheels being too big.. doh!

I have just drilled the hole wider if I have ever needed to do this. The metal is surprisingly easy to enlarge.

I managed to find the extra 2mm that I needed. The brakes are now on and everything is complete. If I get time at the weekend I'll take some photos. I'm very pleased with the end result. It's a shame my intention is to sell it rather than use it. She looks remarkably good for a 30-odd year old.

http://farm9.staticflickr.com/8364/8300163069_21d3cc81b8_c.jpg