In the old days (probably from my BMX time in the early 80's) I ran a smaller tire in the rear. On and off, I still do this with on my mtb bike. I will run a 2.1 on the front and a 1.95 on the rear.
Anyone else doing this or am I just old?

Nope lets of guys, myself included. Your probably more likely to find a 2.35 or bigger on the front and a 2.1 on the back though.

I run 2.5 front and back. Main reason is, when my rear become bold I switch the old front to the rear and then put a new tyre on the front. If I buy race specific tyres I usually get a 2.35 rear and a 2,5 front.

a 2.3 is the smallest i run. lately i find myself running 2.5's and 2.7's sometimes. i've become a real fan of the big fat meats. i could understand wanting to mix it up and run a bigger tire in the front than the back, but honestly its not a practice that has appealed to my riding. but i'm on a hardtail, so i appreciate the extra give back there.

though really, for my riding today (fairly smooth trails on frozen mud) i could have had a thinner tire and been a bit faster. maybe for just such an occasion its time for me to pick up some 1.9's.

i guess, as kind of a not very good answer to your question; buy lots of tires. buy a tire that you think would be good for any of the conditions you ride in, and swap around as you see fit. if you think a bigger tire up front will work better, go for it.

Panaracer Fire 2.4 in the front
Panaracer Fire 2.1 in the rear

Zulu is 3.0 front and 2.5 back. I like the extra control you gain, I also like being able to look down at a giant tire .

2.5 front and 2.3 rear.

On the XC bike I ran the same....2.1 front and rear

I guess I forgot to say this would be for cross country riding on a hard tail.

hmmm having a hardtail i would have thought it would be better havin the bigger on the back, guess i better swap mine round as i have 2.5 back 2.3 front

Clydes who ride road bikes often have bigger tires on back to support their weight. Makes sense in the road world, but with MTB tires I would think there is no reason to have a bigger tire in back.

Is this wrong?

jim

I think I will go with a 2.1 Cinder on the front and a 1.95 on the back. Looking down a skinny tire while bombing down singletrack might be kind of scary. Think I'll log on to Jensen and maybe throw a couple of CN 9971 chains on the bill while I am at it.

I even run two completely different tires...2.4 Maxxis Holly Roller rear, 2.5 Maxxis Highroller front.

But just purchased 2 2.35 Maxxis LarsenTTs.

Me, I'm running a 42a 26x2.5 High Roller up front and 60a 26x2.35 high roller on the back.

I usually run a narrower/lighter tire on the rear.. you can get better acceleration that way. On the front I run a 2.1 or bigger knobby.. you really don't notice weight/ resistance there as bad as you would if it was on the back.

Yeah I've found that aswell and it might sound stupid but i think its easier to mono/wheelie with a narrower/slicker rear tire, I think it's got to do with the acceleration. I find that a fatter/knobbier front tyre helps on obstacles and stuff rolling over things + I hate having a front tire that skids out from under me but with the rear I don't really mind. I'm running a maxxis holy roller 2.4 up the front with a holy roller 1.9 in the rear.

I run a WTB motoraptor comp 2.4" in front and an IRC mibro 2.25" in rear. Occasionally I'll use a Panaracer Fire xc pro 2.1" in the rear.

ok so i have a 2.5 up front what would you suggest for the back on a hardrock, i do i lot of woodland riding roots and mud and stuff

Still being somewhat of a NOOB this is the first I have heard of running different size tires on front and rear. Can someone briefly give the reasoning behind this? Does it really make a difference? I noticed some of you commenting that you have less drag on the rear by having the smaller tire, but doesnt that also sacrifice some traction?

Also is there a normal ratio for size of front to rears or more or less a personal preference type of thing?

The Panaracer Fire FR 2.4 is close to a Maxxis 2.7 in size when your talking about tread width. 2.7 - 2.1, big size difference don't you think?

Anyway i use 2.5 Kenda Nevegal Stick-E up front and 2.35 Maxxis Ignitor rear for DH. For XC, i just use the Ignitor's. All seems to work pretty well for me.

Handling reasons when cornering.