Thorn Cycles Forum

Technical => Transmission => Topic started by: Pasabeograd on July 03, 2010, 11:57:57 am

Title: Chain advice needed
Post by: Pasabeograd on July 03, 2010, 11:57:57 am

I was on a ride today and my chain came off while going up a hill.  When I put it back on I realised it was very slack indeed - so decided I would remove a link.  Don't laugh - but I mistakenly pushed out the pin completely and then couldn't get it back in.  I took it to a local bike shop, who said you can't put the pins back in when they've been taken completely out - so they put on a new chain and I was able to get home.

I'm a bit concerned because the new chain has very little play in it, and I can feel more vibrations through the pedals than before when I pedal hard.  I would appreciate some advice on what to do.  Should I find someone who can get the original chain back on?  Is a too tight chain potentially damaging to the bike?  Any other advice for a distinctly non-technical cyclist?  I've a Thorn Nomad MkII (if that's relevant).

Title: Re: Chain advice needed
Post by: rualexander on July 03, 2010, 12:57:42 pm

Can you not just slacken off the chain tension a touch using the eccentric bottom bracket tool?
A tight new chain on your existing sprocket and chainring is probably bound to feel kind of rough.

Title: Re: Chain advice needed
Post by: mski on July 03, 2010, 03:44:55 pm

Quite curious about this, it appears the local shop put the chain on as if you are riding a single speed ie limited slack.
Did they reset the eccentric when they put the new chain on, as if you haven't adjusted the eccentric yourself, then you will have no movement to play with. I suspect they removed too many links, you can run a rohloff with a reasonable amount of slack.

Title: Re: Chain advice needed
Post by: Pasabeograd on July 03, 2010, 05:15:17 pm

Thanks for the quick replies.  Is one option just to live with it until the chain slackens - or is that likely to damage something.  I'm reluctant to play with the eccentric bottom bracket.  I've look at the instructions, and can't really work out what I need to do. 

Title: Re: Chain advice needed
Post by: stutho on July 05, 2010, 12:06:42 am

Pasabeograd,

You DONT want to run with the chain too tight - It can damage both the bottom bracket and the Rohloff hub.  The EBB looks far more complicated than it really is. To adjust just follow these steps:

• Fully loosen off both EBB bolts (The two bold that face the ground)
• Rotate the bottom bracket. You could use the special tool but I just use my hands!
• Check the tension in the chain
• Check the position of the EBB  there should be more 'meat' on the side facing the EBB Bolts than the side facing the seat tube
• Tighten the EBB bolts - don't over tighten these bolts

job done  -  honestly just do it there isn't much to get wrong see pages 10 & 11 of the manual (http://www.thorncycles.co.uk/thornpdf/ThornBikeOwnerManual2Web.pdf)

Title: Re: Chain advice needed
Post by: Pasabeograd on July 06, 2010, 07:41:03 pm

Thanks stutho - I'll give it a go.

I've now done it.  You were right, it was easy.  I just needed some confidence.

Thanks again.