Chain Length

tigersarethebest

I’ve had to replace the chain on my bike, I normally just get the new chain and against the old chain and cut, and fit no problem, so this time I bought a new cassette too but I’ve gone from summit like 11-34 to 11-25 as there’s no hills around here, but this time I’ve got slight shifting problems, but the chain seems slacker then before, so am I right that I may need to cut the chain smaller to compensate for the change in cassette size.

So I’m thinking I may have to put the chain on the bike avoiding the derailer and when it meets add two links and cut down but ensuring in cuts on a inner plate as it’s a master link chain

Thanks for any advice

N0bodyOfTheGoat

I've used http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html for a good few years on several bikes.

You might need to adjust the b-screw dropping to a biggest sprocket of 25 when using 34 before, you want something like just a ~6mm gap between the derailleur tooth and sprocket tooth (do Google the specifics). When not set decently, it will affect shifts.

tigersarethebest

Thanks, but I think I got the new cassette without looking into it properly, I don’t think my derailer is compatible with the cassette as looked into the specs on it, (highest max is 28), it has been a few years so I think I’m just going to get a new one, as mine also has a long cage and with being a 34,

pblakeney

You are going to have to explain your posts better.
You have gone from a 34 max to a 25 max and your derailleur has a max of 28 but is a long cage? That makes little sense.
A long cage would cope with 34, not 28. The 25 would give you closer ratios and any derailleur should cope.

dj58

tigersarethebest said:

Thanks, but I think I got the new cassette without looking into it properly, I don’t think my derailer is compatible with the cassette as looked into the specs on it, (highest max is 28), it has been a few years so I think I’m just going to get a new one, as mine also has a long cage and with being a 34,

If you were running a 34T low sprocket, the (low max) on your long cage RD is likely to be 34T. What you mean is that the min low sprocket recommended is no lower than 28T according to the RD specs. so you have gone below that with the 25T spocket.

With the correct chain length you may be able to get it to work, though as eluded to above you will need to adjust the B-tension screw to reduce the distance between the RD guide pulley wheel and the low 25T spocket. It may not be possible to achieve the optimum distance though.