Fitting a bigger ring

[dubman]

HI , I want to fit a bigger large chain ring to my mtb , currently 24-34-42 , would it be possible to change the 42 for something bigger without changing the middle ring , i know things can be done but what concerns me is it changing up from the middle ring to the top ok , any ideas on what sort of max size i could goto? i cant change the middle ring cause it wouldn't clear the chain stays.

i understand i may have to get a differant front mech , longer chain etc , used to have an old mtb with 52 big ring was fun


any pointers would be great thanks.

 

[bonj2]

You should easily be able to go to 44 no probs.
But another thing would be to check your cassette. If your smallest sprocket is 12, consider getting one which has an 11-tooth small sprocket. If you did this and kept your 42, this would be like going to almost 46. (42 x 12 / 11)
my highest gear on my roadbike is 51x12, which is 4.25. Only got a 44 on my MTB but smallest sprocket is 11, which gives 4.0, i.e. not much difference.

But to answer your question the highest standard chainrings you can get are 53. you could then have an 11-tooth sprocket giving you 4.8.

Best thing to do is possibly go into a LBS that have got some chainrings of different tooth numbers and measure of the radius of them compared to yours, then work out whether your mech will be able to clear this extra radius.

 

[Tim Bennet.]

You will have to workout what sort of 'triple chainset' you have as not all rings are available for all models. The links below to Sheldon Brown's site will help you understand the different terminology, including Compact triples vrs Compacts, and BCDs, etc.

Having said that, IIRC, you can go 24/34/48 on a mtb compact triple chainset, although as Bonj says, if it's for mountain biking, then just switching to a cassette with an 11 tooth top end is usually the way offroaders get some 'legs' into their gear options without disturbing the rest of the set up.

http://sheldonbrown.com/gloss_bo-z.html#bcd

http://sheldonbrown.com/harris/chainrings.html

 

[dubman]

Thanks for the reply guys , and the links , already has and 11 tooth and the back but i find on down hills once i hit about 30mph i cant get it much faster , im gonna try get hold of a couple of sizes and see what happens , my old mtb some years back had a 52 front and 11 back it used to fly