Socalfriendly

For instance, Reynolds 46mm front and 66mm rear, or a SRAM S40 front and S60 rear.

These are just examples, but you get the idea.

Any thoughts?

AdelaaR

First of all ... the actual difference between any two decent wheelsets is very small at best and often overestimated by many.

That said ... it goes like this: the most aerodynamic wheel setup is a double disc set ... this setup is sometimes used in trackracing to set certain records.
The reason why nobody uses that setup except for trackracing is because a disc in front is very prone to be difficult to handle ... especially when it's windy.
This is why many TT'ers, myself included, use a disc rear wheel and something like a 404 or 808 in front.

Unless you are racing and actually measuring your time, the difference will be that small ... that it'll be practically nothing ... even for racing in packs the difference is negligible.
For TT's and Tri's it makes sense.

ancker

I've seen people run bigger on the rear/smaller on front to combat wind.
The rear wheel is less affected by wind so people will leave it deep and just swap out the front.

I can definitely tell a difference between my 58mm wheels vs my 30mm wheels. If they matched then I would probably just swap the front on windy days. But mismatching wheels (manufacturers) is a no-no.

AEO

I think I recall one experiment that found the aerodynamics improve best when the deeper wheel is on the front, but that's only when you don't have to combat crosswinds.

Jay Olson

It is thought that a deeper wheel at the back increases the stability of a deep wheel in the front. In other words, a 46mm deep front with a 66mm deep rear is easier to handle and more stable in cross winds than a setup with 46 mm deep front and rear.

topflightpro

The size of the rear wheel has no impact on stability compared to the front.

The goal is to maximize aerodynamics by using the deepest wheels possible. As the first poster noted, the most aerodynamic wheelset is discs, front and rear.

However, that is only efficient indoors, where there are no crosswinds.

Outdoors, crosswinds will impact handling on the wheels. The front wheel, which can pivot, is affected to a much greater degree than the rear, which cannot pivot. Thus, it is easier to handle a 50mm deep wheel on the front than it is an 80 mm deep wheel.

The rear wheel is less affected by crosswinds, so you can get the aerodynamic benefits of a deeper wheel without suffering from the handling issues.

That said, if you can only afford to purchase one wheel, you would benefit more from a 45 or 50 mm front wheel with a basic box rim in the back than the other way around.

asgelle

Moving the center of pressure to the rear of a bicycle makes the turning moment from a lateral force on the front smaller. Therefore, increasing the depth of the rear rim, which moves the center of pressure of the entire system back, stabilizes the entire sustem.

Mr. Cranky

Just curious, why is that a no-no? Is it just an aesthetics thing, or is there some functional performance reason?

Homebrew01

The fashion police haven't caught me yet !

The more expensive wheel will feel insulted to share the bike with a less expensive wheel, and will thus have increased resistance. However, studies have shown that the cheaper wheel, in an effort to feel accepted and prove it's worth, will have less resistance than normal, and will likely make up for the increased resistance of the expensive wheel.

If both wheels are expensive, but of different brands, then both may have increased resistance due to having to cooperate with one of "them".

Mansram01

Reynolds offers a Strike/Assault option which is a 66/46 combo so I'm not seeing how mismatching is a manufacturer's no-no.

dtrain

Don't a whole load of Mavic's come this way? (22mm front rim, 25mm asymetrical rear rim)

That's a much smaller difference than you are talking about...but it's an example of that thinking.

AdelaaR

Haha Good one.

DScott

My wheels think your wheels are totally emo.

ancker

Purely aesthetics. And the 41 Hot-or-Not police will come find you.

Not a manufacturer's no-no. Mixing wheels between manufacturers is a no-no. (Zipp/HED, Williams/Zipp, etc)

Mansram01

Not sure how that makes a difference since that does nothing for weight distribution or load. Perhaps handling dynamics... But I guess if I was a manufacturer, I would want you riding another wheel with a different brand name.

Rob13

I bought a set of Easton EA90 SLX for my wife's Amira and the rears are 25mm and the fronts are 21mm. And my Mavic are the same way.