Shimano 105 front caliper - fitting advice needed!

Shadowduck

Among other things, Santa kindly brought me a shiny new 105 front brake caliper for my steel framed relic. It's still running the original Weinmann calipers at the mo, which I can live with at the back but it really needs a bit more power at the front - on steep downhills I can slow the bike down but sometimes find it very difficult to bring it to a complete stop!

So, the question. The mounting rod (the bit that goes through the fork) on the 105 caliper is a lot shorter than that on the original. The caliper comes with some very deep allen drive nuts of various lengths to compensate for this, but these are much too large diameter to fit into the back mounting hole (they're also too big to go through the mudguard mount). So, before I get the drill out and open out the holes in the fork and mudguard to let the nuts fit through - am I missing something here? I can understand a new caliper being made to a standard that didn't exist when my museum piece was built, but it worries me that it doesn't fit through the mudguard, which is a relatively modern thermoplastic job.

Help..?

Monty Dog

You guessed right - you need to get the hole in the back of your fork crown drilled out to take the larger Allen key nut of the new brake - you only need to do the back, not the front or the brake will waggle about. Best to remove the forks and hold them firmly in a vice before brandishing your Black & Decker and nice sharp, new drill. A cordless drill probably wouldn't have the power to make a nice clean hole either - a bench or pillar drill is ideal - don't forget to apply oil to keep the cut lubricated and not cook the drill bit.

John.T

The 105 brake only comes in allen nut fitting so you will have to drill the rear of the fork out. Only the rear section though. As for the mudguard, just fit it in front of the fork.
I need to type faster.

Steve I

It seems a bit drastic to drill out the fork to get the nut to fit. I think you'd be better either trying to improve the Weinmann brake by fitting new pads and/or cable, or fitting a fork designed to take the 105 brake. Sudden fork or front brake failure could be pretty dangerous I reckon. Sorry if that's not what you wanted to hear.

John.T

You will never get the Weinman to work as well as a dual pivot brake. There is plenty of spare metal on the fork crown and this area is not highly stressed anyway.

Shadowduck

Wow, nothing all day then four replies in ten minutes! :shock:

Thanks for the concern, Steve, but it's a relatively small amount of metal I need to remove and this isn't a wispy, lightweight modern fork by any means - in fact the term "tank-like" comes to mind. I already tried a new cable and different pads on the Weinmann; they improved it from suicidal to merely godawful but I've had a few too many dodgy moments to leave it as is. There's some mighty big hills round here and I don't want to repeat the recent experience where both brakes could only slow me from 30mph down to about 15mph and I had to wait for the road to level out before I could stop...* Those shorts will never be the same again.

Can't believe I didn't think to just move the mudguard mount to the other side. D'Oh! Thanks for confirming my suspicions, folks!

*If my darling wifey happens to read this post, this anecdote is totally untrue and only used for effect. Honest.

Steve I

Ok, good luck with the conversion. I know what you mean about poor brakes, I've gone down Anglezarke (steep hill in Rivington, Lancashire) and had a pretty heart stopping moment on a mid 80s raleigh with 105 non dual pivot brakes.

peanut

I think the rear hole has to be countersunk not drilled right through ? doesn't the allen key bolt have a lip at one end ?
I think from memory you need to drill right through at the diameter of the allen key bolt then countersink the new hole slightly to accommodate the allenkey bolt head which is slightly wider than the bolt body

am I too late ??? maybe I should have typed faster lol

JWSurrey

http://www.sheldonbrown.com/harris/brake-calipers.html
http://sheldonbrown.com/gloss_ra-e.html#recessed

I'm guessing that you've already measured the drop on the caliper, and it's OK?

Shadowduck

@peanut - I'm not sure if the metal is thick enough to countersink effectively and the lip on the recessed nut doesn't have a taper that would suggest it was intended for a countersunk hole. The second link JWSurrey posted below doesn't make any mention of countersinking so I think I'll leave it as a plain hole. Thanks anyway.

@JWSurrey - Thanks for the links, never thought to check if Sheldon had anything about it. Nice to see I'm on the right lines, I think one of the supplied recessed nuts is long enough to use if I just open out the back hole - I'll check before I drill though.

I checked the drop before I wrote my letter to Santa so I know that's ok. I naively thought that was the only thing I had to worry about for compatability, should have known that nothing's ever that straightforward! :roll:

richardast

Just before xmas, I put a Shimano 105 caliper on the front of my 25 year old steel framed bike to replace a Weinmann brake.
It has made a huge difference to braking, so go for it.
The minor adaptation took just a couple of minutes and an 8mm drill to widen the rearmost hole in the fork.

blackhands

peanut wrote:

I think the rear hole has to be countersunk not drilled right through ? doesn't the allen key bolt have a lip at one end ?
I think from memory you need to drill right through at the diameter of the allen key bolt then countersink the new hole slightly to accommodate the allenkey bolt head which is slightly wider than the bolt body

am I too late ??? maybe I should have typed faster lol

You are technically correct - but countersinking (more correctly counter boring) is not necessary as long as the nut is long enough. Your LBS should be able to supply a longer one if not.

Shadowduck

Well, I finally got chance to spend an hour drilling and fitting and it's on.

Richardast, you were absolutely right - the difference is amazing! This is probably the most effective upgrade I've ever done, especially given it was pretty cheap (£16).

If anyone reads this thread thinking of doing the same, I can't recommend it highly enough.