Cassettes compatibility? help, please

[Jon C C on a Bianchi]

gents and technical ladies

went to Crawley to have a look at and hopefully buy the Boardman Comp. The bike looks good in the flesh. Sales staff reasonable Ok for Halfords; actually changed the stem for a short one. Sam rode around the shop a few times. Everything going well - good fit and just about to buy when Sam notices that the big sprocket on the cassette didn't look that big.

He was right - despite what the catalogue says it only has a 9 speed 12 -25. The boardman is a compact but the small chain ring is a bit big at 36T (most compacts are 34T aren't they?)

Anyway, Sam needs at least a 28 on the cassette - (29 would be even better ) with a 36T chain ring.

I've seen that GBs has a Campag Veloce 13- 28 9 speed - can I simple replace the existing Shimano 9 speed 12-25 with the campag?? - I've got all the tools just need to know if they are compatible/inter changeable.

failing that can I pick up individual Shimano sprokets and replace the 12 with the 28? if so who would sell them? I don't think Shimano make/sell a 9 speed cassette 13-28, 13-29 for a road bike.

I presume I'll have to change the chain as well as it'll need to be longer - won't it?

Thanks in anticipation

Jon

PS so didn't buy the bike after all that!!!!

[Grahame]

Shimano also do 9 speed mountainbike cassettes which can be swapped with their road cassettes (I use Ultegra 12-27 cassettes on a couple of my mountainbikes). The mountainbike cassettes are easily available in 11-32 and 11-34 ranges.

SRAM also make Shimano compatible 9 speed cassettes (PG950 and PG970 ranges) in 11-28, 11-32 and 11-34 ranges.

For all of these, you may also need to substitute a mountainbike rear derailleur for the original road one. I use a Depre XT one mated to the 105 STi levers on my cross bike.

Shimano mountainbike and roadbike groupset equivalences for reference:
XTR = Dura Ace
XT = Ultegra
Deore = 105

I hope this helps,

Grahame

[Andrew G]

I'll try. You can't interchange Shimano and Campagnolo cassettes due to issues with the cable pull on the indexing. You be able to "get away" without it being too bad, or you can get a shift-mate (see the useful info bit ) to fix the problem. Either way I don't think is ideal for Sam as you want it to be just right, not engineering your way around a problem that doesn't have to exist.

Check the Shimano website (or phone GBs or similar) for the BCD on the spider of the chainset. This is the bolt spacing and I think it's the same for a 34 and 36 inner ring so you could just get a 34 inner ring to replace the 36, and Robert's your mother's brother.

I would have thought there was a suitable Shimano cassette available (even if you have to order it) as they do a 12-27 anyway, but they also do mountain bike cassettes. You may be able to use a MTB cassette with a 29 or 30 big sprocket on the 36/50 set-up. Some tourers (CTC etc) use MTB cassettes on the back of their road bikes to give them the low gears they demand for winching themselves up the side of a Scottish mountain with a fully panniered bike that weighs a ton. I think this, and any of the big sprocket cassette options would be my 2nd choice for Sam to replacing the inner ring as the big sprocket options widden the spacing between the gears so would make for less smooth riding in normal conditions.

[Mike I]

You can't put a Campag cassette on a Shimano hub. If you want to switch the cassette to a bigger one, you might need a different (ie longer) rear mech to take up the extra slack in the chain. A short arm Campag mech will handle up to 26 teeth on the rear, but I don't know about the other mob. If you need a new cassette and rear mech, all your savings on the deal have gone.

The easiest and cheapest solution is probably to switch the inner chainring for a 34. Unless Sam's thinking of riding up the side of a house, that should be sufficiently twiddly with a 12-25 cassette. And when he get stronger, you can stick the 36 back on.

[Jon C C on a Bianchi]

thanks for all the info advice

This is much, much more difficult than I thought!

His Bianchi has a triple 50/39/30T with a 12-25 cassette. Lowest gear is therefore 1.2:1. Given that he is still developing - just turned 14 - I don't want him working big gears too hard. As some of you know he LOVES climbing steep, long hills!!! I've been encouraging him to keep to low gears with a high cadence.

The answer of course would be to buy another triple but it does tend to limit the choice (they also tend to be more expensive), hence why I thought about getting him a compact. But a 34T compact would need a 28 sprocket to give the similar 1.21:1 ratio. Shimano do a 12-27 which just might do.This, though, as you all seem to be saying would not simply be a question of changing the cassette but also the rear mech - which means more money - and presumably I'd need a new longer chain - even more dosh. I don't think he should ride a 34 with a 12-25 although I'm sure he could.

I now think the easiest solution would be to buy a triple - going full circle. aarrgh!!! Looked at the decathalon b/twin sport 4. I've heard they're good bikes with an impressive spec for £700. anyone know anything about it?

head's about to explode

Thanks again

Jon

[Grahame]

Left field suggestion:

Buy the new bike, then transfer the gears from the old bike onto it.

Result - a triple with gearing that you are happy with for him on a new bike for no significant additional expense*.

The transfer should only take a couple of hours to do REALLY properly (ask Sean). I'd offer to do it as a club night "fitting and fettling gears" session if you wanted me to.


*I would suggest new inner cables all round, using the outers supplied on the new bike. They are just easier and more reliable to fit first time than second time around - total additional expense £10- £15 (ish) depending on the specification of cable that you go for. Oh, and a cup of tea and some cake or biscuits for the mechanic is always a good investment.

[Jon C C on a Bianchi]

Hi, all and especially Graham

just got back from the pub so not sure that this makes sense...

what if I bought a 57cm Bianchi frame - would that be easier than buying a new bike??? I really wouldn't have the confidence (or tools or know how) to do it but if you'd do it for me or help me do it - cake, tea and whatever else I'd be more than happy to provide - nice idea to do it on a club night. Not sure what inner cables are but I'll make sure i buy them.

Really appreciate your help and support.

best wishes

Jon

[Andrew G]

If there is nothing wrong with the "old" equipment and you aren't going to keep the current bike for anything then it will be far more cost effective and probably sensible to switch the kit over. If I remember you changed the cassette and chain recently so they'll be fine, but it might be worth replacing the jockey wheels on the rear derailleur during the switch. These only cost about £20 though.

[Jon C C on a Bianchi]

My youngest son, Ben, wants Sam's Bianchi - so I'm back to sqaure one again!

[Andrew G]

Bet you're enjoying this aren't you .

I can't remember your budget Jon but I'm fairly sure that most of the budget aluminium frames are all turned out in the east in a few factories (more Indonesia than Upton Park) so they will all be fairly similar. Obviously excludes the high end stuff like Principia and Merckx. They're all pretty good quality and you probably won't go far wrong with any of them, they 'll just have different paint jobs/stickers, same as with just about every budget carbon frame coming out the same mould in Taiwan.

Have you looked at Ribble yet? I know a number of people in the club have had/got them and seemed very happy with them. Tricky to get to the place to test for sizing but you might find an agreeable of a similar size to Sam who'll let him have a spin to check it out. I followed their bike builder quickly and the all alu sloping top tube frame with a Veloce groupset (50/34 chainrings and 13-29 cassette) came to about £850 once I also upgraded the tyres to 4 Seasons, the saddle to a flite, and a carbon seatpin.

Pinnacle or Decathlon would still probably be one of your best options for a bargain but you may find you have to buy a bike and have compromises in some places on it. The Ribble option would allow more tailoring to Sam's needs and the groupset bits could always be carried forward to a possible future bike or be re-used for #2 son once Sam moves up to bigger gears but #2 still needs the smaller gears.

Also depending how much it is needed now or in a few months, if you can wait a couple of months or so then there will be some good deals out at the end of season (Oct/Nov) when everyone wants to get the 2009 models in their shops.

[mrP(Boonen)VT]

Ribble are good if you know exactly what you want, but I would suggest Jon/Sam want to see and try first.

Anyway, why have all those gears, when just one will do

[Jon H]

If you decide to go for a 12-27 cassette then the standard Shimano road mech is fine. I know, coz that's what I've got.

[Grahame]

[quote="Jon Hemming"]If you decide to go for a 12-27 cassette then the standard Shimano road mech is fine. I know, coz that's what I've got.

[Jon C C on a Bianchi]

Jon

probably a daft question but did you have to lengthen the chain for the 12-27?

[Andrew G]

A new chain will be long enough to cover a compact and a 12-27 with some to spare (remove), if you shortened your original and have the spare links then you can add them back in to give you the desired length. I'm personally not a huge fan of this with modern 9/10 speed chains as they are so narrow they tend not to stand up to splitting and re-joining as well. I'm sure some find it okay but I've always found it weakens them. I'd get a new chain and keep Sam's one as a spare for yourself for when you wear that out.