Can You Change The Number Of Gears On A Mountain Bike

[Sycamore3House]

I have a mountain bike that has 3 chain rings on the front and 5 chain rings on the back (I think that is what you call them) so 3x 5 is 15 gears. It has levers to change gear which I do not like and want to change them to thumb shifters. I can find one for the front but cannot find one for the back.
So can I say use one on the back that is for 7 gears but I will know I have only got 5. Or can I change the cassette ring on the back to 7. The second option my question there is would there be enough room for 2 extra gears within the bike frame??

Any advise would be useful.

[Khandro]

In theory, yes, but it's impossible to say from here. Are you saying you can only find a thumb shifter for a 7 cassette? Do you want more gears or just to change to thumb shifting, if so the 7 shifter should work on the 5 cassette.

[Hopkirk]

Is there a decent little independant cycle shop near you, which does more than just sell bikes?

I would go in and talk to them and see what they suggest.

[Booldawg]

The cassette should fit onto the hub if its a standard Shimano rear hub. You will need to change the chain as well as they are specific to the amount of gears on the rear cassette. Also your rear shifter will have to have the right amount of 'clicks' to accommodate the extra gears.

I take it the bike is quite old if it only has 15 gears? As Hopkirk suggests, its worth taking it to a bike shop to talk through the options.

[Sycamore3House]

Yes the bike is quite old. I have had it for approx 6 months and use it to go to and from work every day and general running about. I only paid £25 for it. But it rides well. It is a Townsend and it says 'Made in England' down the cross bar. My local bike shop wanted £25 labour to change the shifters and then quoted me £30 for a set of them. So on good old ebay I can find the front one for the 3 chain rings but no luck in finding 5 for the rear only 7 but thanks for the answers I think I will be changing somehow shortly. Did not know about the chain thing though

[Khandro]

The in and out travel of the rear mech. (the derailleur) is governed by adjustments of two screws acting as stops. If you fit the thumb-shifters you want, it will only mean that 2 of the positions (clicks) will not be needed, and it should work OK on the 5 you do need.

[Sycamore3House]

Thanks for that Khandro. I will try and find a cheap 7 shifter and use that. I begrudge paying out for things that I can sort myself. And although I have already had my money's worth out of the bike it still goes well and I am now used to riding it but if I change jobs I do not know if I will use it again.

[Slapshot]

Not strictly true Khandro more much more too it that anything noted on the page so far.

Firstly the number of sprockets on the rear is governed by the "dishing" or the shape of the rear wheel. if it's dished for 5 it might stretch to a 6 but no more, to go to 7 you'd need to replace the back wheel.

Second, if you swap a 5 to a 7 you'll need to change the chain because the links are a bit broader on a 5, there won't be the clearance on a 7 sprocket cassette to handle the wider chain.

Third, the rear dérailleur WILL NOT FIT, they are designed to work with a specific number of Sprockets and you cannot change that. Shimano designed some that would work 7 to 8 but not smaller. The grub screw adjustments only work to the width of the dérailleur throw, for 5 sprockets the throw will be 5 for a 10 it'll be ten.

Fourth, Shifters - again they need to be specific you will need a that will handle 7 gears and they are quite rare these days. You may have to change the front dérailleur as the chain lines will need to align properly with the wider gearing

Drop me an email to [email protected] I should be able to help some more