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I am new to this mountain bike lark and ive bought myself a carrera vengeance, i didn't have hundreds of quid to spend so i knew i wouldn't get anything amazing. Ive been out on it a cpl of times and it seems to do the job alrite but i want to start slowly upgrading it starting with the forks, however i know that not all forks fit all frames etc. Ive currently got a pair of SR SUNTOUR XCM V3 forks which have a 30mm diameter tube but when ive been looking around at other forks nearly all of them have 32mm tubes which im guessing won't fit, is this the case or is there some kind of adapter you can buy etc. Might seem like a stupid question but im coming into this new.
The 30/32mm size relates to the thickness of the fork legs and nothing else. The steerer (the single tube that goes into the headtube of the bike) will generally be measured in inches and this is the measurement you need to look out for. I'd guess you'll be looking for 1 1/8" which is fairly common for a mtb.
30/32/36mm refers to the diameter of the fork stantions, and is a trade off between stiffness and weight depending on what type of riding the fork is aimed at. That does not affect whether it will fit the bike.
The steerer tube diameter is the figure you want which will most likely be in inches and is probably 1 1/8"
You also do not want to increase the travel too much over what it has now as that will affect the geometry and the way it rides.
The 30mm is the diameter of the fork upper legs, the one that you have to be concerned with is the diameter of the steerer, thats the bit that fits into the head tube of the frame and the stem bolts to.
Your forks will be 1 1/8th inch diameter, so long as you get a fork with that diameter steerer and suitable travel - up to 100mm probably - you'll be fine with most ones.
Cheers people that's really helpful all makes a bit more sense now :D,
thanks.
In addition to the steerer diamerer (see above) other things to check for fit are:
* How the front-wheel attaches to the fork lowers. A 9mm quick-release system, as used on road bikes, is the most common still. But many bikes now come with forks and wheels that use a bolt-through axle, either 15mm or 20mm.
* Make sure the replacement fork lowers have the right kind of lugs for your front brake. Some bikes still use cable-operated v-brakes with legs that need posts near the top of the fork lowers. Others have disk brakes that have calipers needing lugs near the bottom of the lowers, but these can be either tabs (called IS) or posts (called post-mount).
Good suspension forks can be quite expensive so it's worth getting the right one. If you are unsure, have you considered buying from a good bike shop?