Triple and short cage mech

[KneesUp]

Simple question - I hope. I have a triple (52/42/32) and a short cage rear mech. The cassette is 11-22 I think - something like that.

The rear derallieur has a total capacity of 28 teeth. Obviously I need a capacity of 31 teeth (unless I've misremembered the casette) I assume I am correct in thinking that this will just mean I won't be able to use the small chainring / small sprokets combo without the chain hanging like knitting and rattling on the guides? If so I can live with that, as I wouldn't use that combo anyway.

I am a gear cable short of being able to test it, but if someone could offer the benefit of their greater wisdom before I connect it all up it'd be much appreciated.

 

[slowmotion]

You can usually stretch the Shimano "tooth rules" given in their TechDocs by a couple of teeth or so. I do on my triple. All the gears work but there's some gentle clatter at the extremes.

 

[Yellow Saddle]

Dont' forget that you will also not able able to use the large/large combo. It is easy to say that you will just not use it but if you do, you risk the life of your RD and spokes and rear seatstay. This isn't a doomsday message since it may not be the case depending on what side of the equation you sacrifice - big/big or small/small. I'd go for the latter, as you suggested. As a rule, a very tight big/big is dangerous.

 

[KneesUp]

Thanks both. It's a frame I bought with chain, BB and cranks on and the chain seems the correct length to allow big/big as it is. Definitely agree that too tight is much worse than too loose!

I'll pick up a gear cable today. I have to break the chain again because I threaded the derallieur when I was tried last night, hence ...

 

[Ajax Bay]

Apologies if the OP has counted the teeth on the small chain ring, but triples are often 52-42-30 (ie not 32). When I've tried to push the boundaries of what a RD can wrap, I make sure the chain can manage large to large (sometimes it just happens (eg in the dark) - reasons as YS states) and if this means that third smallest to small chain ring causes rub/noise (because it can't wrap anymore) that's something a rider can immediately do something about (immediate front change, probably double change, actually).

 

[Kajjal]

Best to follow Shimano recommendations and that way you don't have any issues and can just ride the bike.

As above few people do the kind of cross chaining that causes problems but for me not worth the bother.

 

[Ajax Bay]

Best to follow Shimano recommendations and that way you don't have any issues and can just ride the bike.

But if the OP did that (follow Shimano RD spec capacity limit as you suggest) he would not be able to "just ride the bike". He'd have to replace the RD. Not using small (triple) to smallest 3 is no bother at all 32/11, 32/12, 32/14 are useless, as well as cross chaining.

 

[Kajjal]

But if the OP did that (follow Shimano RD spec capacity limit as you suggest) he would not be able to "just ride the bike". He'd have to replace the RD. Not using small (triple) to smallest 3 is no bother at all 32/11, 32/12, 32/14 are useless, as well as cross chaining.

Each to their own, for me swapping the rear derailleur for one that meets shimanos recommendations means you just ride the bike with none of the continual messing about you suggest above.

 

[KneesUp]

@Ajax Bay is correct - it is 52/42/30 The cassette is, I can confirm 12-21 8 speed meaning a total capacity of 31 (I got the small chaingring, large sprocket *and* mental arithmetic wrong in my first post!) The 20-odd year old 105 rear has a nominal capacity of 28 teeth. However, having removed a few chain links, I can now use big/big and small/small (albeit small/small clatters gently as @slowmotion suggests - it's a built in warning) As I'm using downtube shifters I'm pretty unlikely to end up in small/small by mistake as it just looks wrong at the changer end - an advantage old school shifters have over this modern STI stuff, which I'm sure will never catch on.

Thanks for all your input. I'm off to scrub my nails hard enough to remind me to buy some latex gloves.

 

[slowmotion]

@Ajax Bay is correct - it is 52/42/30 The cassette is, I can confirm 12-21 8 speed meaning a total capacity of 31 (I got the small chaingring, large sprocket *and* mental arithmetic wrong in my first post!) The 20-odd year old 105 rear has a nominal capacity of 28 teeth. However, having removed a few chain links, I can now use big/big and small/small (albeit small/small clatters gently as @slowmotion suggests - it's a built in warning) As I'm using downtube shifters I'm pretty unlikely to end up in small/small by mistake as it just looks wrong at the changer end - an advantage old school shifters have over this modern STI stuff, which I'm sure will never catch on.

Thanks for all your input. I'm off to scrub my nails hard enough to remind me to buy some latex gloves.

Nitrile gloves are the way to go. I puncture latex ones before I've managed to put them on. Nitrile's far tougher.