Mountain Biking - how do you determine how much tire clearence your bike can handle?

Pretty much what it says up there. How wide can I go? I have a '98 or '99 Norco Java if you happen to know what it is off the top of yer head.:D thanks

I don't know what it is but I am sure it wouldn't be more than 2.5ish (although Norco does usually leave good clearance). Look at your chainstay and see where the tire sits. Move the centre deraileur onto the smallest ring. Now this is kind of guess work. Measure where the tire was (take tire out) and take off 1/8th to a 1/4 of an inch for mud clearance. Also make sure the tire won't hit the centre deraileur (sometimes happens on some bikes). That should give you your measurement.

For example mine is 3 inch wide. Take 1/4 off of each side leaves me with about 2.5. This give me some leeway up to about 2.7. Now the other confusing part is there is no standard for measuring tires. So you need even more play. For example I own a Maxxis mobster 2.7 dh tire. In reality it is 2.5 inches wide.

Cheers and good luck

Anywhere from a 2.0-2.3 would be safe, a 2.4 or a 2.5 if you're daring.

Its a xc bike so I wouldn't imagine it would be much. Couldn't you just measure how wide it is on the chainstay where the top of your tire is at (if you can understand that), then take off 1/8 to 1/4? That whould be sweet to be able to put 2.5's on there:D

I would probably measure both. Sometimes one is smaller than the other.

Also be aware that some tires listed as one measurement could actually be skinnier. For example I just yanked the 2.0" Roll-X's off the 'hopper and replaced them with (supposedly) 2.125 Vittoria Blue Ridges (don't ask) and the new tires are narrower than the ones I pulled off. I'n fact in comparision they actually look to be about 1.95" wide.

as far as i know about the only way to REALLY know is to try it...

or at least hand-measure the bike and the tire, because the nominal widths on tires are SO different- i think some must measure with knobs and others just the sidewalls... actually i have no idea how they can be SO different. note that with really big tires you have to watch BOTH the width and the heigth!

as Raiyn says above, i have often found tires rated bigger than others to actually be narrower.

i just replaced a Ritchey z-max 2.35 with a Specialized Roller 2.5 and the difference is not much (i have a '02 Specialized Stumpjumper FSR XC). i was actually disappointed b/c i THINK the total air volume may be less and my goal was to be able to run lower tire pressure so i'm not sure if i gained much (maybe b/c i think the sidewalls are stiffer)

i wanted to get a real 2.6 DOWNHILL tire (uh, schwalbe something Jr i think? the non-Jr is a 3.0 tire i think) but i am pretty sure it won't fit b/c
a) i think the 2.6 is MUCH wider than the Speciallized 2.5
b) b/c it's a downhill tire the sidewalls are stiffer and the tire itself "taller" so my vertical clearance will not be as much
c) the tire is more square rather than round which means the corners/knobs have less clearance.

but i'm probably going to go to the bike shop and try it out anyway...

I'll try what you said Mael, worse case scenario I'll contact the company... thanks for all the info:)

measure the size of the gap between the two rear bars (cant remember proper name :P) and then take about 1/4 of an inch off each side.... that'll give ya a rough estimate