Cassettes, derailleurs, shifters

[willant]

I've made a bit of a wreck of the whole gearing of my MTB bike. Could someone please give me some advise on what to do/buy. I have a Shimano Acera M360 deraillleur, a Shimano Alfine S500 shifter, and all i know of my cassette is it is sram 8 speed. I assume that a sram cassette does is not compatible with shamino derailleur and shifter, as i have never been able to tune them. what cassette should i buy? and would i need a new chain? I don't want to spend a lot, and i like quite low teeth gears as i dont have many steep hills in my are.
thanks will

[xerxes]

8 speed Shimano and SRAM cassettes are the same, so you can use either, with Shimano derailleurs and vice versa. However, some SRAM shifters cannot be used with Shimano derailleurs and vice versa, so it's probably best not to mix and match those.

Is your current cassette worn? If it is, you may find that one or more of the front chainrings are also worn. Once cassettes and/or chainrings are worn, there's no point replacing the chain without replacing the other worn parts, otherwise the new chain will quickly wear to match the worn parts. In addition, the new chain will generally skip on the smaller cogs of a worn cassette.

In the UK there are plenty of on-line sellers and when shopping for parts I generally use Google shopping to find the best prices: http://www.google.co.uk/webhp?hl=en&tab=ww#q=8+speed+cassette&hl=en&newwindow=1&safe=off&sa=X&tbs=p_ord:p&tbm=shop&prmd=imvns&ei=EPO4T7WGG8u38gPrksHRCg&ved=0CEgQuw0oAQ&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=6a459950cb5ed9d5&biw=1335&bih=1062

I recently serviced a bicycle for a friend and that had a completely worn drive train, needing new cassette, chainrings and chain. Becuase the larger front chainrings were worn, it actually worked out cheaper to buy a whole new chainset, a Shimano Alivio FCM411, which was a similar quality to the existing one than two new chainring. It's very wasteful, but unless you have a fairly expensive cranks/chainset it seems that it's often the case, so if you do need to replace chainrings it's worth checking the price of a whole new chainset.

If you subscribe there are very good instruction videos available on this site: http://bikeride.com/guide/.

Park Tools also so have some handy guides, but no videos: http://www.parktool.com/blog/repair-help

[willant]

thanks for the reply. Does it matter what size cassette and chainring i have as to weather it will work with my derailleur/shifter?

[xerxes]

Generally, no. Although, you can't use short cage derailleurs with large rear sprockets, long cage derailleurs are fine.

If you want to raise the gearing slightly, you could use a smaller rear cassette , perhaps an 11-28. You could also look at ussing slightly larger chainrings on the front, for example replacing 32 and 42 tooth chainrings with 36 and 46, or buying a chainset with larger chainrings fitted.

Another thing to bear in mind is wear, compact 22-32-42 chainsets are good in theory, less weight, more ground clearance for MTBs, but it does tend to mean that you end up using the 11 and 12 tooth rear sprockets more. These small sprockets wear quickly and I think that a larger chainring up front means that you can use larger, longer lasting, sprockets at the rear 14, 15 or 16 tooth, to achieve a similar gear ratio. On my "shopping bike" I fitted a single 44 tooth chainset up front, which means I mainly use the 18 tooth rear sprocket when pootling around town.

[1FJEF]

(05-20-2012, 12:40 PM)xerxes Wrote:  I mainly use the 18 tooth rear sprocket when pootling around town.

Xerxes, all I do is pootle when I ride.
Shouldn't he find out what's going on first? Check for chain stretch & cog wear? Perhaps define what he means by out of tune?
Lucky for him, all of the parts he mentions are pretty inexpensive if you shop carefully. If I changed all those goodies I'd get a new shifter cable too.
Cassette HG70-I. Or HG-50.

Pretty nice derailleur for under $30 of course you can find much cheaper.

Really nice chain under $20.