Chain length query. Advice please!.

[Simon Daw]

The capacity of the mech is around 29T

26 or 28 depending on the mech, if one believes Velobase. I'm not cerain it's right, but I can't contradict it.

you are only using 26T.

He's using 30.

 

[hamster]

OP was 26. :?

Oops, no looked at the wrong post.

The official figures from Shimano are very conservative - a good guide to what will always work, but usually you can get a lot more. Typically it's a couple of extra teeth, possibly 4 if you have the right frame tooth combination and are prepared for a very rattly big-big combination.

As I can get a 5500 rear (so similar vintage I think) to work with a 28T cassette I'm still sure it's just the chain.

 

[Simon Daw]

You could be right. I agree that the capacities are often a bit on the safe side. A lot depends on the dropout when it comes to the largest sprocket, too.

However, don't forget that the RD-5500 was ten years (and three sprockets!) later than the RD-6400. People using what were essentially road bikes wanted a wider range of gears by then, and that's presumably why the designs had changed. The 5500 has a stated capacity of 29T, and would almost certainly be more comfortable with the setup being used than a 6400.

Anyway, as far as west green is concerned, the thing to check is how the chain looks in the small ring / small sprocket; if the mech's jockey cage is almost horizontal (8:30 o'clock), and the spring only just doing its job, then the chain length is probably pretty much optimal. If, on the other hand, the cage is at say 7 o'clock (or even 7:30, really!) then they've cut it too short, and I'd pay them a return visit.

 

[west green]

Great info, thanks very much. Just checked and it's an RD-6401. Took it for a third ride today and managed to change into all the gears up and down but it just sounds noisy. I'll be on the lookout for a 13-23T - thanks for the advice all - Cheers WG

 

[west green]

Actually should have said - I was able to change up and down on the large ring, haven't ried the small small combo yet, but will give that a go on the way home and check the o'clock positions - hoepfull eveyrthing is ok aprt from the noise factor

 

[west green]

Jockey wheel is almost horizontal on the small 39T and 2nd smallest cog, but changing up and down sounded ropey and felt worst. Anway, thanks for the advice, I'll see how it goes over the next few weeks and lookout for that cassette -

 

[Simon Daw]

Doesn't sound as though the chain length is far out, then. The mech is working a bit past its capacity, so it will be noisier than one set up optimally. It makes it all the more important to avoid using those gears which result in the chain running at a horrible angle, but from what you've described it should work pretty well.

 

[west green]

Thanks, all good advice