Help with derailleur setup.

[snaphaan]

With my LBS about 300 km away, I live on a try first and seek help later bases.

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With my slight weight disadvantage, I decided to change the granny gear on my mtb from 24 ? 30 to 24 ? 34 on an 8 speed cassette. As can be seen from the photo, the 34 sprocket is quite a step up.

 

According to the shimano website docs:  Max. Rear Sprocket  34T

                                                               Max Front Difference  20T

I have adjusted the B-tension bolt to almost maximum in order to achieve a minimum clearance with the top pulley at all times.

 

I  have tried 3 different chain lengths :

Max length + 2 Links,

Max length + 4 links (Original),

Max length + 6 links

 (

Max Length being biggest ring to biggest sprocket. )

 >>

The Max length + 2 Links produced the best result shifting through all combinations.

 

I am unsure if this is correct I would have expected a little more clearance on the derailleur. Please look at the photos and advise if something is seriously wrong.

 

Additional information can be supplied.

 

 

 

[Johan Bornman]

Without knowing what front sprocket the chain is on, I cannot make a judgement on your chain length.

 

However, put the chain on the two biggest sprockets - front and rear - and see if the rear jockey cage makes a 45 degree angle to the front. A bit more is admissible. Trim the chain until you approximately get this angle. This usually sorts things out.

 

Just to make sure, you may then want to put the chain on all the smallest sprockets and see that the jockey doesn't completely collapse backwards with the effect that the chain rubs on the cage's steel bits instead of running purely on the idler pulleys.

 

[snaphaan]

Thank you Johan.

I checked the angles and it is@ 55?  on  the one bike and 50? on the other. I will adjust the chain length on the second bike tonight and see what happens.  Both clear the cages on the jockey, with the chain on the smallest sprockets, although the second one is very close.

Thank you.

 

 

[snaphaan]

Johan

 

I adjusted the second bike to 46? by removing another link set.

We took both bikes up a steep training route today and they work fine.

 

The desired improvement in climbing ability was also achieved and we could actualy ride the complete route. 

 

Thank you for the advice.

 

Pieter

[joevan]

Pieter,

Great to have guys like Johan always ready to help with advice on this site.  Another tip if you are a long way from a LBS is Park Tools site. Thier help site is great, and covers just about any repair you can think of.              http://www.parktool.com/index.asp                                           

joevan2007-12-22 23:52:57