Bottom bracket swap - are Halfords talking rubbish??

rodgers73

I have an old bike with a gear cable guide riveted to the bottom of the BB shell. The hole for the rivet is quite large.

The current BB is an old unsealed unit that I'd like to replace with a modern maintenance free one.

I've found a compact chainset that I want to install and a good supplier of the correct BB too.

The one thing tripping me up is the comment made by a guy in Halfords. I had asked him if they sold spare gear cable guides and he looked at the hole that it rivets into. He said this was very large and I should really drill a new (smaller) hole further forward on the BB shell and use a tap and dye to allow a bolt to be used instead of a rivet. The reason being that a rivet in the old hole in the current position was likely to catch on the new sealed cartridge.

This seems a bit odd as I cant see how moving the position of the hole would matter if its a circular shell - surely if the cartridge bearing was circular too then no matter where I put the new hole it will still have the same clearance as the current hole would!

Does anyone see something I cant here? Am I about to make a big mistake by ignoring this guy? Should I bother with the new hole or can I just stick a new BB in there? I had thought about grinding off the end of the rivet inside the shell using a Dremel tool if there was a genuine problem with the clearance - would that work?

Thanks

Tom

the_prophet

if you can't just use the old guide, i'd get the rivet out, and just glue or stick the guide back onto the bottom of the frame. it will be held in place by the cables as they are under tension anyway.

ignore halfords advice 90% of the time in my experience, it's usually wrong or ill informed.

one_bad_mofo

I had thought about grinding off the end of the rivet inside the shell using a Dremel tool if there was a genuine problem with the clearance - would that work?

Seems like a very sensible option to me. The other option that springs to mind is drill the rivet out if it catches and then Araldite (or some similar glue) the guide in place.

rodgers73

Thank god for that! I was looking at some really annoying work otherwise.

Cheers guys.

John.T

Don't knock the Halfords guy too much. He has highlighted a possible problem. He could not know if it would happen until the old BB is removed.
Personally I would go along with the Dremel idea. You may well not need to.

Berk Bonebonce

The casing in which a cartridge bb comes in will fit quite snug into your bb shell, so snug infact that anything sticking through the bb shell more than about 5mm might snag on it.

The best thing would be to buy a new bb and try fitting it to see if it snags. It might not.

rodgers73

Berk Bonebonce wrote:

The best thing would be to buy a new bb and try fitting it to see if it snags. It might not.

Thats the plan, coupled with the Dremel

balthazar

I think that was a fair comment, from the chap in Halfords. I don't agree with his solution, but he visualised a problem which most people would miss. Still, trial fit, check etc., as everybody has said.

squibnocket

Take it to a LBS, I have a 20 year old Raliegh and recently had a new BB and chainset fitted, always good to get a second opinion.

danlikesbikes

+1 for the LBS as if their any good they will trade on giving good advice to you whether you buy from them or not.

markos1963

I think the Halfords guy was right in his advice. What he is saying is the current hole if used would be too large to fit a bolt of a reasonable size, so if you drill a smaller one and tap it you could use a small bolt(from the outside and fitting flush in the shell) I think he didn't advise glueing on the guide as he would have no idea as to whether the glue would bond to your paint(unlikely as there is a lot of oil/grease around there) or cause damage.

rodgers73

I'll be riveting and grinding off the "spare" inside the shell I think. Easiest solution all round.