8 - 10 speed conversion

[thatruddyvicar]

My carrera tdf is getting ready for a new chain, and probably cassette as well.

I'm thinking about a new bike, perhaps not until spring though, but I'll always keep this for a bit of a runaround/winter hack.

I can just about manage but I would like a couple of lower gears. Is it generally a worthwhile upgrade to go up to 10 speed and possibly new wheels, I wouldn't mind doing this one up a bit. Maybe a new compact chai set as well, the front rings are showing where.

This would be quite expensive, though I'll look for secondhand shifters on eBay. Is it likely to be worthwhile or is best just to stay 8 speed but getting a cassette with bigger gaps so I get one or two lower gears.

[531colin]

For winter, I would leave it at 8 speed. 10 speed is expensive to replace worn bits, almost certainly less robust than 8 speed, and generally a similar range of gears to 8 speed.
To lower the gears, there are options......
Smaller chainrings can lower the whole range, but keep the current steps.
Bigger sprockets can give you a bit lower gear, with the same top gear, and bigger jumps but you might need a new rear mech. to accommodate big sprockets.......and if you don't want big jumps, you may have to lower the top gear as well, buying 2 cassettes and swapping sprockets around....

[thatruddyvicar]

Just checked the chain rings and cassette. Front 52 & 40. Rear cassette 26 - 12

[Bicycler]

Anything which involves changing the shifters is likely to be expensive. 10spd would give you closer gears without necessarily giving you much lower ones.

A fairly cheap way to get a bigger range would be a cassette with bigger sprockets. 8 speed go up as far as 34t. You may be limited by how big a cassette your road rear derailleur will accept (28t?) but an 8 spd MTB one will play fine with your STIs and neither the derailleur nor the new cassette would be expensive.

The other option might be a smaller front chainring. Someone else will be able to advise as to whether that is possible with your current front derailleur.

Re: wheels - 10 speed cassettes fit on the same hubs as 8 speed cassettes. The 10 spd cassette's sprockets are narrower (hence Colin's point about reduced durability) in order to fit in the same space. The wheels themselves are identical.

[531colin]

Just checked the chain rings and cassette. Front 52 & 40. Rear cassette 26 - 12

I have no use at all for a 52 chainring, 46 is the biggest I have.
Unless you regularly use all the high gears, you could run 46 & 34 chainrings and shift all your gears quite a bit lower.**
With your existing rear mech. I doubt you will get bigger than 28 teeth, which is a small difference.....you might be able to use 30T .....

**see http://www.sheldonbrown.com/gloss_bo-z.html#bcd to work out what sizes will fit

[bryce]

I'd upgrade to 10 speed if it was me. A 10 speed cassette and chain is only about £30.

But given you'd need shifters, and possibly mechs, it could get expensive. Probably better to try a wider cassette on 8 speed and see how much the big gaps annoy you. Gearing is personal and depends heavily on both your legs and your riding style.

Worst case if the cassette is too big for the rear derailleur, a new one is £15-£20ish. A new rear derailleur is likely to work with an upgraded drivetrain if you decide that's what you want. You could get a new 8 speed chain, cassette, and rear mech for the cost of a 10 speed chain and cassette.

It's likely the chainrings are 130 bcd so will only go down to 38 teeth. So to reduce gearing on the front would require a new crankset, and possibly a front mech and bottom bracket.

[Pandaz]

8 speed is great for winter. Plus the chains heavier and more robust.

[foxyrider]

Lose that inappropriate chainset and get a compact on there. That will make far more difference than a couple of teeth at the rear.

All the tosh about life expectancy - well i get through as many chains and cassettes mile for mile on my 7 speed as i do on 10 speed.

If you are interested in going to 10 still i've a brand new set of Tiagra 10 shifters, rear mech and cassette going cheaply (i bought a bike with them on but i'm converting it to Campag) PM me if your interested.

[531colin]

"tosh"....?
Winter road salt wrecks stuff. Fact, not tosh.

[foxyrider]

"tosh"....?
Winter road salt wrecks stuff. Fact, not tosh.

indeed it does but the number of gears doesn't make any difference to that!

[MikeF]

I don't own a 10speed bike, but if you are thinking about buying a new bike in the spring, then to me there doesn't seem much point in make major changes to this bike. It seems extra outlay for little gain, but then that's your choice - perhaps you want to try 10speed before you buy a new bike. Otherwise, as Colin suggests, buy smaller chain rings for the front to shift all lower gears, a new 8 speed chain which should be cheaper than 10speed, and a new cassette, which could have an 11tooth small cog instead of 12tooth if you still want a high top gear. eg 48F 11R is the same as 52F 12R

[531colin]

I think side plate failure (cracks radiating out from the rivet hole) is a new form of chain failure caused by spreading the end of the rivet within the thickness of the side plate in 10 speed chains, and maybe 9 speed as well.
I never saw an 8 speed fail like that.