Mechanics and Fixing Any Questions Answered

I once worked on someone's very expensive road bike, whose mate had told him that to adjust a rubbing caliper he needed to "undo that bolt"

It was the bolt holding the two halves of the caliper together, and he couldn't understand why I was telling him that he'd need new pads, rotor, and a full brake bleed.

Maybe I should have just sanded everything...

Or walked away.

I’ll declare an interest here, I work for a company that sells two types of brake cleaner and IPA.

Yes the normal brake cleaner is very (entertainingly) flammable so I wouldn’t spray a lot around and use a naked flame (of course I would I love fire!).

I’ve checked the safety data sheet and there is nothing about it turning into phosgene, it does not contain any compounds containing chlorine so it can’t.

I’ve used it for years and on bikes and motorbikes and it leaves no residue, funnily enough our brake cleaner is formulated to not leave an unsafe residue on brakes…….

Can’t speak for anyone else’s. OR FOR IPA!

It does however contain acetone which isn’t nice.

You know more than me then, and specifically which chemical it is in some brake cleaners that gets a bit nasty when welded.
I've never felt the need to use brake cleaner on bicycles, because IPA on a cloth works and is less toxic and wasteful. Pads are cheap, so just replace them.

Bottom line is: sort out the contamination issue first. I don't know how so many people end up with brake fluid splattered over their brakes so often.

specifically which chemical it is in some brake cleaners that gets a bit nasty when welded

In the olden days, brake cleaner used chlorinated solvents, for excellent reasons from the point of view of the primary function. For equally excellent ecological and human safety reasons, all commonly available brake cleaner these days is chlorine free.

I get a massive staff discount so it’s all almost free……

on bicycles I use the brake cleaner that contains acetone on my discs and pads.
I use IPA on my Shimano calipers and levers as I’m not sure about brake cleaners effect on their seals or paint.

I’ve used brake cleaner on SRAM calipers for 3 years with no ill effects.

I use brake cleaner if I have to clean rim brake tracks.

I’ve stopped cleaning my own hands with brake cleaner because of the acetone.

the acetone free version doesn’t evaporate as quickly and I’m not used to it and what it affects

Then weld away, everyone!

I've now welded pads to the rotors and the stopping power is incredible

Oh forum discount then?

Classed as Gross Misconduct

I also get cheap Wera tools, selling them on is Gross Misconduct as well.

Mechanics are not cheap, they work on £60/hour (or complexity of jobs)

Had to reread to make sure you were talking about bike mechanics, and I’m still not sure. What shop anywhere pays bike mechanics £480 a day?

What shop anywhere pays bike mechanics £480 a day?

The charge out rate is not the same as the mechanic's wages, it also includes premises, tooling, insurance, business owner's profit etc.

Mechanics and Business Any Questions Answered

Dah, right, thanks.

I put a front rack on my fixie, is this a safe amount of threading to ride? sorry if dumb :)

2 Attachments

Hello guys, I have a question, hopefully quick to answer.
I have a set of campagnolo chorus 12 shifters (perchased used with 1200miles on them) still to assemble but I have the feeling they will be "hard" as when trying them while unconnected, I struggle to press the thumb lever.
I was thinking about giving them a good clean but I have no idea which grease to use in the moving parts once degreased. Any idea?
Online I find very different opinions and not a shared one. Thanks

Hmmm, depends. Some nuts the threading goes right to that face that sits against the dropouts, others there’s a gap of a good couple mm before the threading starts. If your nuts (ooh matron) are of the latter design it’s probably not great.

The general rule of thumb is you need as much thread in there as the nominal bolt diameter, ie 10mm of thread in the nut for an M10 bolt or whatever your equivalent is. @ojwithbits

This.

Look up Weldtite track nuts, should be 9mm for the front but do double check.

Alternatively, get regular 9mm nuts and washers.

I would probably flip the nuts until it gets sorted (via one of the methods already suggested)

Rule of thumb is thread engagement length should equal the thread diameter.

When testing exactly how tensile capacity increases with increased thread engagement, it turns out that 4 full turns of thread gives virtually 100% strength and anything further doesn’t increase tensile capacity. That is full turns of thread and the first turn is usually reduced height, so only partial engagement. That applies to both bolt and nut.

I would guess that you’ve only got a couple of turns actually engaging, given the integrated washer under the nut.

They feel harder to release the cable than pull it without a derailer attached, because there's a spring inside them to counter the derailer's return spring.

Cleaning them almost certainly won't do anything. 1200 miles is almost new; they'll soften up with use. And keep getting softer and softer, until they eventually won't hold position.

If you google up an overhaul how-to, you'll see the way the G-springs sit in the indexing part, and it'll make sense. Instead of replacing them when they're tired, you can just tweak them to get some life back in them.

cheers people, I’ve temporarily flipped the nut and put a washer in there, seems like the entirety of the nut threading is engaged on the axle now

Are weldtite nuts smaller overall in thickness? They seem to be threaded the same as the track nuts i have on now i.e not threaded to the end of the built in washer. I did buy some 10mm nuts from the local hardware shop but they don’t seem to want to thread on entirely, maybe an old vs new threading thing??? I don’t want to force them on so may just settle for some rattling track nuts for a bit

1 Attachment

I for one would not be fucking around with this

Has to be a better solution - longer axle, p clips, nitto m18 with the jubilee type clamps, new fork, etc?

It's 9mm hence 10mm nuts wont work.

Yes, Weldtite track nuts have longer threads and should give a much better grip, if not, ditch the rack or get a longer axle.