the 'there's no such thing as a stupid question' bike maintenance thread

Hey guys, trying to fix up a gt sanction 2014 for a friend. I replaced the bushings in the i-drive pivot near the bb as there was play in it, cant find play in any of the other bearings or bushing in the frame.

When the rear brake is locked or used heavily there is a massive vibration up through the frame, regardless of positioning on the bike. it starts at the rear but is so strong it can be felt up through the bars.

The bearings in the rear wheel have no play and ive tightened the axle way up. I tried a different wheel with a different rotor (that i know to be good) and it slightly reduced the vibration, im putting that down to bigger volume tyre though.

I also tried a different brake and that made zero difference, ive clamped the caliper bolts way past recommended torque no difference. I also over tightened the headset (bearings need replacing but theres no play in it) to see if that could be it but no.

I fix up mtb's for a living part time so im not completely clueless (i think Big Grin ) but this is completely throwing me, ive checked everything to the best of my abilities and ive found no solution. Anyone here have any ideas? I would appreciate anything at this stage.

The centering screw on top of rhe brake arm is for final tuning, but is often used (in error) for more gross adjustments, which leads to the brake arm on one side becoming too high.

Re-adjust the centering screw until the surcaces ofthe two brake arms around it are roughly level with each other or the screw is roughly level with the brake arm surface (it varies by brake model/generation).

Pull the whole brake assembly around its frame-mount bolt so that the pads are roughly centred over the rim.

Align the pads’ height, placing them as low as possible, to allow for the fact that, on dual-pivot calipers, the pads’ surface tends to creep up towards the tyre as it wears.

Apart from the adjustments above, the only other likely issues are wrong wheel size (700c wheel in a frame meant for 27” wheels) or the wrong caliper (did the bike come from the factory with those calipers?), or a bent front fork (would need to be very bent before this issue arose).

Deano12345 wrote: »

Edit : hit post by mistake

I’ve recently gotten a new bike and it’s fantastic, not really looking to upgrade with anything particular but I have a query about the brakes. It runs disks and my options for wheels are pretty limited it seems, I’d love to go carbon but I can already feel my wallet crying.

There seems to be quite a good selection of second hand carbon wheels for rim brakes, so is it possible to change the hubs to run disks, or am I starting off down a long expensive path doing that ?

A long expensive path I'd say.

Macy0161 wrote:

7 Speed cassette on an 11 Speed Hub - am I right in thinking 4.5mm spacer on top of the 8/9 speed spacer? And then adjust the limit screws? I'm thinking of having the old beater as a permanent turbo bike. It's a smart direct drive turbo, so came with the 8/9/10 speed spacer. Any reason it wouldn't work?

Macy0161 wrote:

In erg mode, and going on sheldon, I could probably mix and match cassette and chain with the 7 speed chainset and derailuers as I wouldn't have to change gears, but I haven't ruled out a go at zwift, which I think would require having gearing...

If all your using is erg mode it should be fine. If free riding in zwift im not sure how accurate the shifting would be. Might as well give it a try.

Macy0161 wrote:

Ordered the cassette and spacers, so we'll see. Loving erg mode so far - only have to change gear for spin downs as I'm spinning out!

I love doing sweetspot training on zwift in erg mode. Boosted my fitness higher than its ever been.

magicbastarder wrote: »

so - carbon newbie here. what torque setting is typical for the bolt attaching the brake calipers to the frame?

Parts of the frame like brake calliper mounting areas will have a metal insert inside the carbon, so the torque requirements should be similar to an aluminium frame.
The parts of a carbon frame which are torque-sensitive are those where it's not possible to have any metal inserts, and you really are clamping on carbon - typically the back of the stem (if the fork steerer is carbon), the front of the stem (if the bars are carbon) and the seat clamp.

My pressfit BB was creaking under load, so I got a press (the Lifeline one) and a removal tool (the Park Tool one) and set about replacing it. I thought I'd done a pretty good job. I cleaned the shell, and applied Loctite to the new BB, since I'd heard that's how you ensure there's no creak.

But it didn't ensure there was no creak. In fact, the creak was worse.

So I got a new BB, and replaced it a second time, this time using grease instead of Loctite.

The creak isn't as bad as it was with the Loctite, but it's no better than it was to begin with. It's a road bike with a Shimano BB94 bottom bracket.

Can anyone recommend a decent time machine so I can go back and strangle whoever invented pressfit BBs?

seven stars wrote: »

My pressfit BB was creaking under load, so I got a press (the Lifeline one) and a removal tool (the Park Tool one) and set about replacing it. I thought I'd done a pretty good job. I cleaned the shell, and applied Loctite to the new BB, since I'd heard that's how you ensure there's no creak.

But it didn't ensure there was no creak. In fact, the creak was worse.

So I got a new BB, and replaced it a second time, this time using grease instead of Loctite.

The creak isn't as bad as it was with the Loctite, but it's no better than it was to begin with. It's a road bike with a Shimano BB94 bottom bracket.

Can anyone recommend a decent time machine so I can go back and strangle whoever invented pressfit BBs?

Are you sure its the BB and not the chainring bolts????

seven stars wrote: »

I'm not completely sure, so that's worth investigating. But the creak got much worse with BB#2, and then reverted to its previous level with BB#3. So I'm inclined to think it's the BB installation rather than chainring bolts.

But if the creak is caused by the bolts...the creak will remain regardless of the number of BB's replaced. It could also be the pedals?

07Lapierre wrote: »

But if the creak is caused by the bolts...the creak will remain regardless of the number of BB's replaced. It could also be the pedals?

What I'm saying is that the creak actually got worse when I changed the BB. And then improved slightly when I changed it again. I don't see how this would be possible if it was something else causing it, like chainring bolts or headset or pedals. If it was, you'd expect that changing the BB would have no impact on the creak.

It definitely feels and sounds like a BB installation issue.

seven stars wrote: »

What I'm saying is that the creak actually got worse when I changed the BB. And then improved slightly when I changed it again. I don't see how this would be possible if it was something else causing it, like chainring bolts or headset or pedals. If it was, you'd expect that changing the BB would have no impact on the creak.

It definitely feels and sounds like a BB installation issue.

Fair enough, your probably right...it's just you've changed the BB 3 times now so if it was me, I'd start considering other possible causes.

I've had lots of creaks/squeaks/ knocking noises etc. And none of them were the BB itself. Pedals, cranks, wheels, headsets...they can all creak and they all sound like they are coming from the BB.

Not really bike maintenance but it may require an adjustment....

I'm getting friction on one side only so trying to get to the root cause of it.

Could dropping the saddle 5mm possibly help?