# What is the effect of a wider rim? Does spreading out the tire lower its height?



## Poppadaddio (Apr 15, 2007)

23mm's are about all I can run on my present road bike With Mavic Equipe's for example, I can only accommodate 23mm's. Even some of the "fatter" 23's are close. With fat/big tires the tire tread rubs on the brake bridge. 
What is the effect of a wider rim? Would spreading out the tire lower its height (overall diameter)?
It does not seem to me that I would have side clearance problems.
I would just like to run 25's once in a while.


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## MercRidnMike (Dec 19, 2006)

If you have the clearance in your fork and frame for wider rims, they can have benefits.

First, they change the shape of the tire, widening it out. I find the effect can be a bit like a wide sport motorcycle tire....the wider profile and lower likelihood that the tire will fold / squirm results in better grip and makes cornering more confidence inspiring.

Next, the contact patch changes....it's not as thin and long, so it helps a little with rolling resistance. It's a massive exaggeration of the effect, but try flipping a ruler end-over-end vs side-over-side to see the difference.

Third, you can often run a lower pressure....better ride quality and less road chatter contribute to less rider fatigue and energy losses meaning a slight increase in speed.

Finally, better tire / rim width match usually leads to a slightly better aerodynamic profile for the wheelset as a whole so they slip through the air better.

The last 3 items will not result in earth shattering changes for the "average Joe" rider's overall speed, but there will be a slight benefit. For me, between the latex tubes I started using a couple years ago and the new, wide rim wheelset I added this year, I've found better cornering and a much more "sublime" ride quality make me that much more eager to get on the bike and go for a long ride


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## aclinjury (Sep 12, 2011)

25mm rím ain't gonna fit if you can only barely fit a 23mm on your current narrow rims


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## bikerjulio (Jan 19, 2010)

I think OP is asking about 23 mm tires vs 25 mm tires.

Counter intuitively perhaps a wider rim will make the tire taller. So no.


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## FeltF75rider (Feb 10, 2012)

I'm riding November FSW3 wheels that are 24mm wide and Vittoria Corsa Speed G+ (only come in 23) the tires measure out at almost 26mm. I have a set of Corsa G+ that measure out at 27mm for a claimed 25. Not exactly sure what is limiting your tire width but wider rims could make this worse. If you have any opportunity to maybe borrow some ones wider wheels to see how the fit is prior to buying a set, it could be a big help.


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## n2deep (Mar 23, 2014)

bikerjulio said:


> I think OP is asking about 23 mm tires vs 25 mm tires.
> 
> Counter intuitively perhaps a wider rim will make the tire taller. So no.


Sorry, not true, as the developed length of the tire does not change but the width of the rim does so the overall height has to be a little shorter, not enough to be of concern.


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## bikerjulio (Jan 19, 2010)

n2deep said:


> Sorry, not true, as the developed length of the tire does not change but the width of the rim does so the overall height has to be a little shorter, not enough to be of concern.


Sorry, not true. I told you it was counter-intuitive.


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## Jay Strongbow (May 8, 2010)

"Sorry, not true, as the developed length of the tire does not change but the width of the rim does so the overall height has to be a little shorter, not enough to be of concern."


Incorrect. Picture folding in the legs of a table. The table top drops right? And goes back up as you bring the legs back out? Of course after a certain point it starts going back down but that point is n/a with the rims/tires being discussed.


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## Lombard (May 8, 2014)

bikerjulio said:


> Sorry, not true. I told you it was counter-intuitive.


Absolutely. And it's quite easy to see why. Take a piece of paper and roll it into a semi-circle. Note that as that semi-circle gets tighter, the overall diameter is smaller. Widening the rim effectively loosens that semi-circle. As the rim gets wider, the tire becomes both wider and taller.

Of course, in a hypothetical case, if you widen the rim far enough (wider than the tire width), the tire's height will indeed be less. But as I said, hypothetical because by that time, the bike would be unrideable.


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## n2deep (Mar 23, 2014)

n2deep said:


> Sorry, not true, as the developed length of the tire does not change but the width of the rim does so the overall height has to be a little shorter, not enough to be of concern.


Biker Julio Mea Culpa!!! Your absolutely correct!!! Thanks!!!


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## MercRidnMike (Dec 19, 2006)

I'd be surprised if that image held true for all tires....the Continentals are tall tires and seem always to be tall tires. I suspect that they way those tires are put together (i.e. tread / sidewall interface and construction) influences their shape. 

My Schwalbe 1's on my Zondas (17mm internal) are taller at the same pressure than they are on my Altamonts (19.5 mm internal width). It's not much, but on my S2, it's definitely there....in fact, it's there on your image too (though the pressure is different) when comparing the 25 mm tire on the Ardennes vs Ardennes+. Wide vs. tall will be a combo of rim width, tire size, tire shape / construction induced limits and tire pressure...far beyond what we want to get into here, I'm sure.

As for the OP, it may be possible to run 25mm tires, but if you're having clearance issues now with 23 mm tires, chances are you're like me where only certain tire and rim combos will have sufficient clearance for your particular bike.


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## bikerjulio (Jan 19, 2010)

n2deep said:


> Biker Julio Mea Culpa!!! Your absolutely correct!!! Thanks!!!


Tu inexorabilis es. Obsecro, mihi iterum autem non contradico.


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## tom_h (May 6, 2008)

MercRidnMike said:


> If you have the clearance in your fork and frame for wider rims, they can have benefits. [snipped]


Some of those benefits are mutually exclusive.
For example, the slightly lower rolling resistance of a wider tire is only if the pressures of narrow & wide tires are kept same.


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## Lombard (May 8, 2014)

tom_h said:


> Some of those benefits are mutually exclusive.
> For example, the slightly lower rolling resistance of a wider tire is only if the pressures of narrow & wide tires are kept same.


This is true. But one advantage of using a wider tire is you can reduce pressure without risking pinch flats. With reduced pressure, the wider tire's rolling resistance will be *the same* as the narrow tire at its higher pressure, but you will have a more comfortable ride with the wider tire.


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## MercRidnMike (Dec 19, 2006)

tom_h said:


> Some of those benefits are mutually exclusive.
> For example, the slightly lower rolling resistance of a wider tire is only if the pressures of narrow & wide tires are kept same.


Yes and no. 

The match point for rolling resistance between a narrow and wider tire does have a difference in pressure (at least that's what the folks at bicyclerollingresistance.com found). If I can knock 10 psi off my pressures, get a smoother ride (less wasted energy getting bounced around), better cornering and still have a matching or slightly lower rolling resistance going to a wider tire, for me, that's a good thing. The difference in rolling resistance may be so small as to be negligible (for a non-racer like me), but the overall impact could be dramatic (depending on a lot of other factors).


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