# Why run two different size tires?



## 2big2ride (Jan 6, 2004)

I noticed that some folks run a smaller tire in the rear.......
Why?


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## Ken in KC (Jan 12, 2004)

*The Theory Is...*



2big2ride said:


> I noticed that some folks run a smaller tire in the rear.......
> Why?


The larger tire in front will help you hook up on the trail better and the thinner tire in back will allow the rear wheel to bite better by settling down further.

MY theory is that you should just run two of whatever you're running in front. In my case, that means 2.4's.

Ken


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## Billy (Jan 9, 2004)

Ken in KC said:


> The larger tire in front will help you hook up on the trail better and the thinner tire in back will allow the rear wheel to bite better by settling down further.
> 
> MY theory is that you should just run two of whatever you're running in front. In my case, that means 2.4's.
> 
> Ken


You are thinking into it too much. Its because it looks cool


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## weather (Jan 12, 2004)

side point: the rear often has limited mud clearance.


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## AZBound (Jan 4, 2004)

*Suspension effects vs rolling resistance*

Some folks may prefer the cush of a big tire up front but want to have the lower rolling resistance of a narrower tire on the driven wheel.

That's a huge generalization, because tread patterns and casings also have a lot to due with rolling resistance. Still, tread for tread, tire for tire, the narrower one could be seen as faster. There may also be a minority of folks who use the big/small combo to take a fraction of a degree out of a steep head angle.

I like having same-same, because I can swap a less-worn front with a more-worn rear and get a few more miles of decent traction before replacing the set.

This leads me to a question for subsequent posters: Why do modified trials bikes have dissimilar tires? Are the rims different diameters or widths as well?

AZB


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## DiRt DeViL (Dec 24, 2003)

Tinker told us that for XC racing a 2.1 front tire is fat enough for good traction and a 1.9 rear is great to minimize rolling resistance, have better mud clearance and because the rider weight is more to the back the thiner tire will have more contact with the dirt.

I didn't followed Tinker's advise on the SS because it's more forgiving to run fat tires but on a XC rig seems to work fine.


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## KavuBiker (Jan 13, 2004)

*Having owned a modified trials bike...*



AZBound said:


> Some folks may prefer the cush of a big tire up front but want to have the lower rolling resistance of a narrower tire on the driven wheel.
> 
> That's a huge generalization, because tread patterns and casings also have a lot to due with rolling resistance. Still, tread for tread, tire for tire, the narrower one could be seen as faster. There may also be a minority of folks who use the big/small combo to take a fraction of a degree out of a steep head angle.
> 
> ...


Most trials bikes in general roll a very large DH-style rear tire, the reason being so you can run really low pressure (for traction) and also to take the hit of moves like lurches and drops. Now, believe it or not, trials bikes (especially Mods) are built to be as light as possible before having to sacrifice strength. They run a smaller front tire to save weight and also because the front tire doesn't take the abuse the rear does.

As for the rims, the rear is often wider than the front, for the same reason stated above. Also, many run a DH rear rim and an XC front again to save weight. When you have to lurch onto a 4 foot ledge, you need the bike to be as light as possible.

Just my $0.02

KavuBiker


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## itsdoable (Jan 6, 2004)

I would run as fat a tire on the back if I could, but sometimes there's just not enough room between the chain stays...


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## Tracerboy (Oct 13, 2002)

*without a doubt.*



Billy said:


> Its because it looks cool


that's how i make pretty much all my decisions; in cycling _and_ in life.


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## SlowSSer (Dec 19, 2003)

weather said:


> side point: the rear often has limited mud clearance.


extremely good point. found out the hard way on my 29er last week.

I run a 2.4 mutano, moto or a 2.5 wierwolf on the front due to the cornering-at-speed on loose SoCal gravel/sand. also, a bigger tire gives you a little more suspension when the fork is locked out, and allows a lower pressure (than, say a 2.1) for a larger contact patch on the ground.

the back? 2.1 veloci's only on the 26er bikes. why? tractor style tread. cant beat it! run something similar on the 29er- some offering from kenda.

now, if we could only get larger diameter fron tires for 29ers.


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## EBasil (Jan 30, 2004)

AZBound said:


> Some folks may prefer the cush of a big tire up front but want to have the lower rolling resistance of a narrower tire on the driven wheel.


Yep, that's me. Plus, I like the extra control and effect from a bigass front tire, and a 2.1 is about all that will fit in the back of my HT.

2.1 OnZa in the back, 2.4 Mutano in the front.


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## Gatehouse (Mar 1, 2004)

*That's interesting..*



SlowSSer said:


> extremely good point. found out the hard way on my 29er last week.
> 
> I run a 2.4 mutano, moto or a 2.5 wierwolf on the front due to the cornering-at-speed on loose SoCal gravel/sand. also, a bigger tire gives you a little more suspension when the fork is locked out, and allows a lower pressure (than, say a 2.1) for a larger contact patch on the ground.
> 
> ...


...my bike came with Velociraptor's and I never did like that paddle tread in the rear. Just didn't work for me. I like a 2.1 motoraptor or for spring and fall (wet) and a Ritchey Zmax for winter and summer (dry).


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## SlowSSer (Dec 19, 2003)

Gatehouse said:


> ...my bike came with Velociraptor's and I never did like that paddle tread in the rear. Just didn't work for me. I like a 2.1 motoraptor or for spring and fall (wet) and a Ritchey Zmax for winter and summer (dry).


keep in mind that 99% of the riding I do is in dry conditions....except for when I ride outside ouf socal.


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## GlowBoy (Jan 3, 2004)

2big2ride said:


> I noticed that some folks run a smaller tire in the rear.......
> Why?


The front and rear tires do completely different jobs. The question isn't "why would you run different tires front and rear?" ... it's "why would you run the SAME tire for front and rear?"

http://www.sheldonbrown.com/tires.html#mixing

Personally:

On MTBs I like to run as big a tire I can up front, at low pressure, to maximize cush and to some degree traction. Sadly, since I'm currently riding a 29"er my front tire is no wider than the rear one, but that will be rectified once the 29" fatties (reportedly) come out later this year. The last front tire I was running on my 26" bike was a 2.25 Geax Blade, which is considerably bigger than a 2.4" Mutanoraptor.

In back, cush isn't as critical ... fat tires do incur a weight penalty, so don't use them if you don't need them. Plus low pressure incurs a much greater RR penalty in back than it does in front, so again no need to run 'em low and fat. I've been quite satisfied with 2.0 to 2.1 inch rear tires for a long time.


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