Cycling UK Forum

+1 on bending wobbly chainrings. I suffered with some Raceface thing for ages until an off-road crash forced me into trying it. Fairly easy to get them flatter than they had ever been when the bike was new.

Thanks for that CG. Can’t believe we’re well into page 2 and we’re still not clear what the problem is.

Assuming that is a 7sp cassette and the skipping is at the rear:

Seven speed cassettes used to come with a very thin spacer that sat between gear 6 and gear 7. It’s absence would be placing those 2 sprockets too close together and therefore preventing the chain sitting on the teeth properly. Doesn’t explain why the problem is confined to the middle chainring though - if that is indeed so?

531colin wrote: ↑12 Nov 2023, 11:37am I’ve seen on here somebody posting bike CADs where 2 bike frames were superimposed or you could “morph” one frame to the other.
I suspect it was somebody younger than me, but that’s most people!

Do you mean: Bikegeocalc.com? It’s definitely not CAD, but once you’ve invested a bit of time in it I find it more versatile than the ‘pre prepared’ alternatives.

Strange that the geometry geeks site doesn’t actually tell you what the front centre is for the bikes listed though. Especially as the diagram highlights what the dimension means.

So the fixing bolt is 8mm and the ‘dustcap’ 10mm? Sorry, my memory let me down there.

Thanks for the heads up to keep that bolt well greased, and occasionally remove it even if for no other reason than to check it still moves. I hadn’t appreciated that they could be so troublesome.

Just to be clear here - I did agree that the 10mm increase is likely to be fine:

TheBomber wrote: ↑10 Nov 2023, 4:31pm That said, for the change you’re proposing it should be fine.

I have just tried to explain the symptom you might experience if you were to move too far from what the frame was designed for, in case it was borderline beforehand.

531colin wrote: ↑11 Nov 2023, 7:29pm Is that 100mm travel fork in a frame designed for rigid fork?

From memory, I calculated that to achieve a similar head angle as other comparable bikes on the market at the time, I would have had to reduce the fork to 60mm of travel. I instead changed the bike and even my cycling mates could tell that ‘my’ cross country abilities improved overnight.

From memory the 8mm is the ‘dustcap’ - that enables the 6mm within it to act as an extractor, lifting the crank off the spindle’s splines. Do you need to remove the 8mm?

531colin wrote: ↑10 Nov 2023, 7:19pm Won’t it still be steeper than modern mountain bike geometry?

You’re outside my area of experience there so I can only speculate. The extra trail from a modern slack head angle could be controlled by increasing the fork offset. Or maybe that long top tube/tiny stem combo gets it all back under control. Just don’t know. I do know how compromised an otherwise lovely Kona Explosif was to ride as the frame had not been tweaked for the 100mm fork it was supplied with.

If you slacken the head angle significantly (unless you also increase the fork ‘offset’ to maintain the ‘trail’) then what you’ll notice off road is that it is difficult to climb out of ruts without the front wheel washing out beneath you. That said, for the change you’re proposing it should be fine. If it turned out to be a problem could you change any fork internals to reduce the length? It was common to be able to do this ‘back in the day’ but not sure if it still is.

My experience of disks on Shimano hubs has been similar to the OP's - on the front hub the disk side typically seems to be in a worse state than the opposite side. I've put this down to the heat, as described by Cycle tramp. More recently I've seen the problem less often - either because I've upped the inspection/maintenance or because I don't ride the bike quite so hard as I once did.

Carlton green wrote: ↑1 Nov 2023, 6:11am I’ve only ever built with plain gauge spokes, doubtless double butted is better but plain gauge has been adequate for my use and it’s been what I had to hand.

I’ve always thought PG spokes broke the ‘strong, light, cheap - pick two’ rule as they’re neither strong nor light. Usually reserved for penny pinching bike manufacturers rather than anything you’d bother with when building your own wheels.

My TV came with a 3 year guarantee but it is still working 11 years on. The three years bit is just a minimum expectation.

robc02 wrote: ↑25 Oct 2023, 3:55pm Every 17mm height increase will slacken the frame angles by roughly one degree.

That sounds like a handy rule of thumb to remember. A quick check of an online geometry calculator shows a similar one: to maintain 'trail' (one of the main determinants of bike handling) fork offset should increase by 6mm for each one degree slackening of the head angle.

Unless the crown on your existing fork is especially oversize, increasing the clearance is likely to increase the axle to crown measurement. This will have an effect of the handling of the bike - you may be happy with that but you should be aware of the possibility before purchase.

Other fork specs that need to be considered/got right:
- Fork offset (which also has an effect on handling);
- QR dropouts or through axle?
- Disc or calliper brake? With the latter you will also need to ensure there is enough reach in the brake arms if you do increase the axle-crown length.

Details on the above - or even generally on the bike you are trying to adapt - will help with more specific recommendations.