Changing or adding a large gear.

cramman

Sorry, new to this so appologies if the wording is wrong, which it will be, talking about cogs etc.

I think I am going to be going for this SCOTT - CX Comp 2010 - http://www.wheelies.co.uk/p28804/Scott- ... -2010.aspx on the cycle to work scheme and am just wondering how easy is it to up the gearing, idealy, just make it a triple as I'm a little concerned that I'll 'spin out' on hills etc.

Cheers,

Cramman

biondino

A triple is useful for steep UP hills, but useless for downhills which I assume is what you mean. If it's any consolation, on my fairly low-geared compact I can get to almost 45mph before spinning out in 50/12 - are you really concerned about often going faster than that?

biondino

Ah hang on, I think you ARE talking about uphills. If that's the case, we need to know the size of your chainrings and cassette before we can tell you if a compact or triple would be more suitable.

(spinning out = when your legs are pedalling faster than you can manage, so obv it only happens on downhills or in very low gears (low = easy; high gears are the harder ones))

cramman

45mph will be plenty. But, the Scott I'm looking at is geared 46-12.

To be honest, I have no idea what that mean in terms of speed. Just looking at road bikes it's a fair bit smaller.

will3

Have a look here:


http://www.sheldonbrown.com/gears/

you can enter the rpm. and get speed as an output depending on ratio.

A quick look shows that 46:11 is roughly the same as 50:12 would be, so if you're really likely to spin out, you could put a cassette with an 11 tooth on.

Begs the question though: why not just buy a bike with the right gears to start with?

edit to correct the ratios

wgwarburton

cramman wrote:

45mph will be plenty. But, the Scott I'm looking at is geared 46-12.

To be honest, I have no idea what that mean in terms of speed. Just looking at road bikes it's a fair bit smaller.

IMHO 46x12 is plenty for a commuting bike at the top end. I'd be more worried that the 36x25 low gear isn't terribly low. OTOH, you arn't going to be doing any loaded touring on it, are you? So unless you're planning on carrying tens of kilos in a backpack or you're commuting across the Pennines, I should think it'll do you fine.

I'd be looking to fit mudguards for commuting, too, but then I live in Scotland...

Cheers,
W.

wgwarburton

will3 wrote:

...
A quick look shows that 46:12 is roughly the same as 50:11 would be, so if you're really likely to spin out, you could put a cassette with an 11 tooth on. ...

Oops- typo... Should be 50x13. I wouldn't bother pointing this out, except that the OP gave the impression he wasn't quite clear on some of this... Sorry!

Cheers,
W.

biondino

Hmm, okay. You'll still be able to hit 40mph on it, but not much faster than that before you have to just tuck and freewheel. Is that likely to be a problem?

cramman

Thanks for the replies.

Seems like I was worried about nothing. :oops:

Basically the bike has to come from Wheelies and I fancy a CX for the all round use ability conbined with the fact it's probs better than a hybrid on the road.
I do plan on using it on some trails, coast to coast etc.

Won't be carrying loads of weight tho, just the laptop really.

I think it's the best choice for me, I did consider a bianchi as this has more road gearing, but, the rest of it seemed poorer than the other 1000 pound bikes.

Oh, and I though I was talking about going down hills and spinning out.

cyberknight

My 7 speed freewheel has a 14-28 range on it with a bog standard 52/42 chainring-according to sheldon brown that gives me 98 inches top gear which for me is plenty as it is a fully racked + mudguard set up with panniers so if i can pootle along on a good road at 22-23 mph i am happy ,can spin that in 52x16 .

markp2

I have just changed the cassette on my Genesis from a 24-13 9 speed to a 28-11 9 speed. Both with a 50 tooth chainwheel.
This gives a good spread of gears both up and down hill. The drawback is larger jumps in gearing in the middle of the pack.