# Does running a 700x23 front and x25 rear affect handling?



## MJCBH (Nov 25, 2002)

So I've been running some Conti's with a 700x23 front and 700x25 rear (not for any particular reason, I think things just ended up that way as I was using up my stock-piled tires that I have). I was wondering if this subtle difference would affect handling in any way?


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## danl1 (Jul 23, 2005)

MJCBH said:


> So I've been running some Conti's with a 700x23 front and 700x25 rear (not for any particular reason, I think things just ended up that way as I was using up my stock-piled tires that I have). I was wondering if this subtle difference would affect handling in any way?


Well, if you've been running it, you've got a better answer than anyone. 

But essentially, no. Any supposed difference would be deeply into the theoretical.

FWIW, Continental sells 'mismatched' tire pairs under the Attack/Force label. 22 and 24mm, if I recall correctly.


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## sandiegosteve (Mar 29, 2004)

More comfortable ride?


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## r1lee (Jul 22, 2012)

Correct, attack force is 22 and 24. Continental believes that this is the preferred setup due to their 4 wheel racing experience.


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## martinot (Aug 14, 2009)

r1lee said:


> Correct, attack force is 22 and 24. Continental believes that this is the preferred setup due to their 4 wheel racing experience.


+1 here. I am not buying the wider is faster deal just because they say so. You put more air into the narrower tire and it will roll as fast as wide. Sure it will be less comfy but so are the ultra stiff racing bikes these days and we pay big buck for them.

Narrower front gives you better cornering and on certain wheels better aero. Wider rear gives you more traction. I am all for it without going bananas (19/28 ???). If someone does not care about front-to-rear tire rotation it sure makes sense. I think Conti has done some research and if it would not make sense they would not start producing Attack/Force in the tubular format starting 2013. If only people were not so locked on 4000S  ...


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## looigi (Nov 24, 2010)

r1lee said:


> Correct, attack force is 22 and 24. Continental believes that this is the preferred setup due to their 4 wheel racing experience.


4 wheel? That seems very strange. Wouldn't 2-wheel, as in motorcycles, be a bit more (if still distantly) relevant?


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## AndrwSwitch (May 28, 2009)

IME, nope.

You can get a noticeable difference in handling from a big difference in tire widths. Not really applicable on most road bikes, but the size mismatches possible on a mountain bike can be big enough.


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## giosblue (Aug 2, 2009)

It makes perfect sense to run a wider tyre on the back.


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## cxwrench (Nov 9, 2004)

martinot said:


> +1 here. I am not buying the wider is faster deal just because they say so. *You put more air into the narrower tire and it will roll as fast as wide.* Sure it will be less comfy but so are the ultra stiff racing bikes these days and we pay big buck for them.
> 
> Narrower front gives you better cornering and on certain wheels better aero. Wider rear gives you more traction. I am all for it without going bananas (19/28 ???). If someone does not care about front-to-rear tire rotation it sure makes sense. I think Conti has done some research and if it would not make sense they would not start producing Attack/Force in the tubular format starting 2013. If only people were not so locked on 4000S  ...


you are confused about the relationship between pressure and rolling resistance. when dealing w/ a 'normal' range of pressures, say from 80-120, and a 'normal' range of rider weights, less will be faster than more. 
you would inflate a smaller tire to a higher pressure to prevent rim damage/pinch flats, not to make it as fast/faster than a wider tire that can run lower pressure.


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## TimInSeattle (Jan 2, 2012)

Yeah, you do get a change in handling with the smaller tire up front. I usually run that set up except when using tubulars. But, you could get just as much change by a 5psi change in tire pressure. How closely to you tune your tire pressure? 

You absolutely get less aero drag with the narrow tire on the front. The rear width has less impact on aero drag since it is in the wake of the rider/frame and the higher weight on the rear is better handled by a wider tire. 

My favorite winter set-up is a 25mm 4-Season on the front and a 28mm Durano on the back, both at about 78PSI for my 161LB weight. The ride is nice and fast enough for winter.


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## dcgriz (Feb 13, 2011)

TimInSeattle said:


> You absolutely get less aero drag with the narrow tire on the front. The rear width has less impact on aero drag since it is in the wake of the rider/frame and the higher weight on the rear is better handled by a wider tire.
> 
> My favorite winter set-up is a 25mm 4-Season on the front and a 28mm Durano on the back, both at about 78PSI for my 161LB weight. The ride is nice and fast enough for winter.


I think Enve may disagree with your first statement. I believe the SES 3.4 and 6.7 place the wider rim up front to improve stability.


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## r1lee (Jul 22, 2012)

looigi said:


> 4 wheel? That seems very strange. Wouldn't 2-wheel, as in motorcycles, be a bit more (if still distantly) relevant?


Yes cause I had a super brain fart!


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## TimInSeattle (Jan 2, 2012)

dcgriz said:


> I think Enve may disagree with your first statement. I believe the SES 3.4 and 6.7 place the wider rim up front to improve stability.


Well, we are talking about drag here, not stability; which is a very different discussion.

I assume the OP is talking about simple swaps of tires, say a 23mm Conti GP4000 for its wider cousin, the 25mm, both on a traditional rim where frontal area the prime driver for drag. Not entire tire/rim systems like those Enve developed. Aero rims are a rather complicated subject. Simon would agree with this. We can always email him to confirm. 

Also, the Enve wider rim is a complicated subject that is used for a number of reasons.


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## martinot (Aug 14, 2009)

cxwrench said:


> you are confused about the relationship between pressure and rolling resistance. when dealing w/ a 'normal' range of pressures, say from 80-120, and a 'normal' range of rider weights, less will be faster than more.
> you would inflate a smaller tire to a higher pressure to prevent rim damage/pinch flats, not to make it as fast/faster than a wider tire that can run lower pressure.


I occasionally get confused but in this case higher pressure = lower rolling resistance does make sense to me and seems to be a common understanding of at least one tire manufacturer

EDIT\ADDITION. There is a good point made on riding at lower pressure on non-perfect surfaces - tire deflects more (energy lost here) but the bike-rider is not lifted up (energy saved here). So we really have multiple variables: road smoothness, tire deformation (and walls deform differently than center section), pressure, weight of the system, ... And then we are talking about the accelerations - higher pressure tire will transfer energy much better than lower pressure.
Where I ride roads are generally smooth (but what does smooth means, right) and there is lots of speed changes (accelerations, decelerations) so I am going to continue racing/riding on "measured" 23mm or less (unless off-season) at 100+ psi but I'll keep my ears open to new arguments/results.


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## dcgriz (Feb 13, 2011)

TimInSeattle said:


> Well, we are talking about drag here, not stability; which is a very different discussion.
> .


Didn't you say that the narrower profile on the front wheel reduces drag? 
The premise behind the Enve SES is that the wider (and shallower) profile of the 26mm front rim reduces drag and improves stability. They have an extensive discussion on the subject on their website which probably you are aware off since you know the Enve guy on a first name basis.

On my touring/commuter bike I run 25s in the front and 28s in the rear for the sole purpose of being able to carry more weight without exceeding the rating of the tire and also get a bit more cushy ride. Handling is not an issue and aero is the furthest from my mind commuting with panniers.


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## webbmx7 (Dec 4, 2012)

I've tried both situations on my personal bike, and unfortunately I am not that caliber of a rider that can tell the major difference. I logged 2.5K miles last year between a carbon bike and alum bike and in all honesty when push comes to shove, what really matters is that you are back on the bike.

I'm sure there is a difference, however for the average guy like me I couldn't tell.


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## danl1 (Jul 23, 2005)

martinot said:


> EDIT\ADDITION. There is a good point made on riding at lower pressure on non-perfect surfaces - tire deflects more (energy lost here) but the bike-rider is not lifted up (energy saved here). So we really have multiple variables: road smoothness, tire deformation (and walls deform differently than center section), pressure, weight of the system, ... And then we are talking about the accelerations - higher pressure tire will transfer energy much better than lower pressure.
> Where I ride roads are generally smooth (but what does smooth means, right) and there is lots of speed changes (accelerations, decelerations) so I am going to continue racing/riding on "measured" 23mm or less (unless off-season) at 100+ psi but I'll keep my ears open to new arguments/results.


If you want see the other side of the argument, start here; Repeat "Jan Heine" in your google searches until you are convinced one way or another. 

Bicycle Quarterly: Performance of Tires | Off The Beaten Path

The truth isn't quite as cut-and-dry as either the "wide" or "skinny" adherents want it to be.


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## charlox5 (Jan 31, 2011)

martinot said:


> I think Conti has done some research and if it would not make sense they would not start producing Attack/Force in the tubular format starting 2013. If only people were not so locked on 4000S  ...


I'm no racer, but I hated Force/Attack and I love GP4000s for a variety of reasons, none of them empirical haha.


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## martinot (Aug 14, 2009)

danl1 said:


> If you want see the other side of the argument, start here; Repeat "Jan Heine" in your google searches until you are convinced one way or another.
> 
> Bicycle Quarterly: Performance of Tires | Off The Beaten Path
> 
> The truth isn't quite as cut-and-dry as either the "wide" or "skinny" adherents want it to be.


An OK piece of work but not convincing at all. Bicycle riding does have to do with aerodynamics and "rolling-down" the slope is not the riding most of us do. You fight the aerodynamic forces, you pedal, you accelerate, you corner, .... A gravity based roll down test means very little to me. The conclusion that wider is faster for bike riding/racing with no observed plateau cannot be taken seriously. The same test with a properly shaped bicycle would show that heavier is faster. Thanks but no.


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## Dunbar (Aug 8, 2010)

martinot said:


> An OK piece of work but not convincing at all.


If you're reasonably intelligent though it's hard to keep claiming 23mm tires have a lower rolling resistance than 25mm tires after reading that article. For that reason alone it's well worth the read. And as far as the "aero" differences I would *love* to see a study on how many watts a 23mm tire saves over a 25mm tire at (say) 25mph.


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## martinot (Aug 14, 2009)

and I repeat - An OK piece of work but not convincing at all that THE WIDER IS FASTER.
I am buying the point that wider has lower rolling resistance at the same pressure. But there is a difference in rolling resistance and overall performance of the tire.
The observation that ".... the “fastest” tires had half the resistance as the slowest" should not point to the conclusion that the wider tires are faster than the narrower ones because their rolling resistance is lower at the same pressure.


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## kmak (Sep 5, 2011)

I found this article helpful in understanding optimal tire pressure (in spite of the typo in the title!):

http://www.adventurecycling.org/resources/200903_PSIRX_Heine.pdf


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## lbkwak (Feb 22, 2012)

Some people will never learn....:nono:


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## nhluhr (Sep 9, 2010)

cxwrench said:


> you are confused about the relationship between pressure and rolling resistance. when dealing w/ a 'normal' range of pressures, say from 80-120, and a 'normal' range of rider weights, *less will be faster than more*.
> you would inflate a smaller tire to a higher pressure to prevent rim damage/pinch flats, not to make it as fast/faster than a wider tire that can run lower pressure.


I've not seen any testing to indicate this. A recent issue of Velo suggested the opposite, in fact. I don't think you can make any statement like this without a fuller consideration of road surfaces, etc.


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## nhluhr (Sep 9, 2010)

dcgriz said:


> Didn't you say that the narrower profile on the front wheel reduces drag?
> The premise behind the Enve SES is that the wider (and shallower) profile of the 26mm front rim reduces drag and improves stability. They have an extensive discussion on the subject on their website which probably you are aware off since you know the Enve guy on a first name basis.


You're talking rim width. Thread is about tires. Subtle, but there is a difference. No matter which rim you use, a wider tire will BE wider than a narrower tire on that rim. All of these high end aero wheels are optimized for 23mm tires. The width of their profiles after they leave the tire bead is all about shaping and controlling airflow. Their aerodynamic characteristics are largely blown to **** as soon as you use a significantly wider tire. Josh Poertner of Zipp said this to Lennard Zinn in his column:


Josh Poertner said:


> What they are missing is the aerodynamic piece. We have data from the Zipp 303 launch showing the 303 with different width tires (see graph). The figure tells the story of how you can really optimize for tires below a certain (width) number, but eventually the tire really dominates the airflow and ruins everything. In general, our wheels are optimized around 23mm tires, which means that 21mm tires usually run about equal, maybe a fraction of a watt faster, but don’t change the behavior of the wheel. Moving to a 25mm adds drag, but can also change the stall behavior of the wheel. And by the time you are at 27mm, you have something that behaves quite differently.


If you aren't using rims that are aerodynamically optimized in some way, then it's more about frontal area and in that case, the wider tire loses.


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## Dunbar (Aug 8, 2010)

martinot said:


> The observation that ".... the “fastest” tires had half the resistance as the slowest" should not point to the conclusion that the wider tires are faster than the narrower ones because their rolling resistance is lower at the same pressure.


That is a separate variable explained in the article - the materials and type of construction (high/low TPI) have a large effect on rolling resistance. To put it plainly, some tires are just slow and it has nothing to do with their width. Anecdotally we've probably all been on a bike at some point with tires that you can tell are dogs after a few pedal strokes.


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## AndrwSwitch (May 28, 2009)

I'm glad there's some quantitative evidence in favor of my affection for fancy tires.


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