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Discussion Starter · #1 ·
I was reading a review recently on a set of carbon wheels, and it said that running a 23mm front and a 25mm rear had some sort of aero advantage.

Is there any truth to that?

At least twice, I've heard other cyclist say that they run a large front and smaller rear wheel, something about better contact patch on the road.

BS? Placebo? What say you?
 

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Regarding different tire sizes, it's usually okay to run a wider tire on the rear because it's not the leading edge of the air flow. By the time the air reaches your rear wheel it's already been broken, and it's blocked by the seat tube anyway. For the front wheel running a 23mm tire can be advantageous if the rim is wide and wing-shaped. This ideal on rims like the November Rail 52 or Zipp 404 where a 23mm tire would mesh well with the rim's shape.
 

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I ride with a 23/25 now only because there's more weight on the rear (and I'm basically a clydesdale nowadays) whether or not there's an aero advantage is besides the point.
Kind of sucks that I can't rotate front to rear like I used to do, though. :(
 

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Just guessing but I would say people are running a narrower rear tire due to tire clearance issues, not necessarily for performance reasons. That said, all but ENVE SES shallowest front rims are 1.5-2mm wider external width than the rear. I suppose you could achieve a similar effect using a narrow rear tire on rims of the same width:

Smart ENVE System, True Form and Function

The Smart ENVE System optimizes the interface between the frame surfaces and the wheels, creating an integrated system. The front and rear wheels interact differently with the air and the rest of the bicycle. Rim shapes are optimized to allow airflow to stay attached at higher yaw angles, thus reducing drag and improving ride performance.

  • The front wheel is wider and shallower to improve stability and reduce drag in any wind condition.
  • The rear wheel is deeper to reduce drag where stability is less affected.
  • Wheels were tested on multiple frame designs in order to produce the maximum drag reduction. The result is a wheel system, which handles predictably, and displays superior drag results when installed in multiple bicycle frame designs.
 

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I was reading a review recently on a set of carbon wheels, and it said that running a 23mm front and a 25mm rear had some sort of aero advantage.

Is there any truth to that?

At least twice, I've heard other cyclist say that they run a large front and smaller rear wheel, something about better contact patch on the road.

BS? Placebo? What say you?
Absolutely there is an aero advantage (assuming rim dimensions are appropriate). And that advantage is absolutely tiny. If I were a world class cyclist racing at the top level of the sport and paid the big bucks to win time trials, I would most likely be running a narrower front tire (to match my super aero wheel). Otherwise I would not be interested that much in saving a second or two per mile. But that's just me.
 

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Discussion Starter · #7 ·
Thanks for the replies.

I'm about the size of an ogre so aero-components are not something I worry, I was simply curious why some people run such setups.

Regarding sharper handling on 23's...that's an interesting notion. I can't say I noticed any difference in handling when I switch to 25mm tires but then again I have not tried it myself (i.e. 23mm front & 25mm rear).
 

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I picked up a set of enve 2.2 tubular that have a 27 mm external width. I have always run 23s in the front and rear. This time around, I will run 23 in the front and 25 in the rear...not so much for any significant advantages, but b/c the front fork may not be able to clear the 25 up front.
 

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It's not a bad idea. The front and rear tires do very different jobs. Continental tried selling road racing tires that were different tread and width front and rear but they didn't catch on.

While I run 25's both wheels, I always run my front tire ~15psi lower than the rear.
 
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