Pedals Occasionally Slip Forward When In Top Gear

[xerxes]

Re:

The sprockets you have look OK, not much sign of wear. However, I think that is a 7 speed Uniglide cassette and freehub, with the 7th sprocket, that is threaded, missing.

That's a Uniglide cassette outer sprocket on the left of the image below, with the thread inside, which looks to be missing from your cassette.

See here: http://cycleseven.org/uniglide-and-hype ... patibility
And here: http://www.sheldonbrown.com/k7.html

 

[Silvergoat]

Re:

this page is giving me ideas...

http://cycleseven.org/customising-shima ... e-cassette

Has anyone tried one of those whopping new fangled "1X" cogs, btw?

 

[woodbine]

Re: Re:

Have to say, those cogs look in very good shape/well defined.

KMCs are pretty sound chains. Though the 'magic' link can be a bugger to undo when you need to remove the chain :facepalm:

Thanks for your verdict. So, from the image, can you see that the smallest, outer sprocket is in good condition, and unlikely to be my problem? It's only in this gear that I get occasional slipping.

The bike hasn't had too much use, being in storage for 20 years. Not sure why the UG freehub was noisy though and needed to be replaced. Don't know how long they last.

The slipping in top gear was evident immediately after re-commissioning the bike, but wasn't a problem years ago before being laid up. The occasional slipping seems to be since new chain and freehub fitted. However, the more I ride it, the slipping seems to be less frequent. Still wondering if something is 'bedding in', or what the problem is if it isn't the sprockets or chain.

 

[woodbine]

Re: Re:

The sprockets you have look OK, not much sign of wear. However, I think that is a 7 speed Uniglide cassette and freehub, with the 7th sprocket, that is threaded, missing.

That's a Uniglide cassette outer sprocket on the left of the image below, with the thread inside, which looks to be missing from your cassette.

I think the photos may be a little deceptive. There's definitely a threaded outer sprocket fitted, holding it all together. These shots were taken after I cleaned everything up, but before the worn freehub was replaced.

Are you thinking that there's too much exposed thread on the end of the hub? Will have to take a look at the bike as it is now with new hub fitted, to see if similar amount of exposed thread.

 

[jimo746]

You could try riding it a bit more, sounds like the new chain may be stretching a little to fit with the rear sprockets, you may find it settles down, and if it's only an issue on that one cog you may be able to live with it .

Just one on chains, as far as I know if you have a Uniglide freewheel on the rear then you should use a Uniglide compatible chain (UG), Is your KMC chain Uniglide compatible? You might have a Hyperglide (HG) chain which may not work very happily with a Uniglide rear end.

 

[woodbine]

Thanks for your reply, Gold Trader. The KMC X8.93 chain has the correct dimension links for my Uniglide, but as to wether it is compatible with the Uniglide in other ways, I don't know.

Do you know if this chain is compatible, or know how I could find out?

http://www.kmcchain.eu/chain-KMC_X8–93-mtb-8,7,6,5_speed

http://kmcchain.us/chain/x8-93/

I have triple oval Biopaces at the front, if this makes any difference.

 

[jimo746]

Re:

Looks like that Inc chain should work fine with the freewheeling at the back.

 

[woodbine]

Thanks. Just as a precaution, I contacted KMC to see if the chain I have is the one they would recommend, and it is the correct one. As you say, ride more (weather permitting) and see if chain stretches a little to bed in.

 

[legrandefromage]

Have you checked the rings on the chainset??

They usually wear out much quick due to their soft alloy material

 

[woodbine]

Chainring wear did occur to me, but as the problem is only in one gear (18th), I suspected the smallest rear sprocket. Looking again at the photos of the chainring, it looks like it's ok.