Bicycle Mechanics - Front/Rear Wheel symmetry, does it matter?

I don't know if this has already been covered but I was wanting to know the advantages of having a front wheel larger then the rear?

Boneshaker, matey. Arrr/

Probably a title for the thread would stimulate people to help you!

Probably a title for the thread would stimulate people to help you!
Yeah I guess your right.

The smaller the diameter of a wheel, all other things being equal, the stronger the wheel will be. Since the rear wheel bears more load on a bicycle, that would potentially be an advantage. Another thing that comes to mind is the fact that a setup like this is conducive to building a bike with very stable handling characteristics. A good illustration of that is in the case of off-road motorcycles, with their super fat, but smaller diameter rear tires and somewhat skinnier, but larger diameter front tires. Cannondale messed around with the concept back in the '80's on mountain bikes, and I think I've seen some downhill mountain bikes like this as well.

What about smaller front wheel? I know there's one brand of women's bike (the name escapes me just now) that have smaller front tires to fit into a tighter geometry for shorter people... But I seem to recall someone saying (probably here in BF) it's a big no-no.

I fixed the title for ya Brock.

I remeber seeing one of those bikes Treefox, it king of reminded me of the setups they were using on Time Trial bikes in the late eighties. Depending on geometries & weight bias, I'd think a smaller front wheel would tend to wash out easier.

Thanks for the replies, I dunno anything about smaller front wheel... it seems kinda whack.

A larger front wheel would have a tendency to roll over objects easier than a smaller one, as in the MotoX example above. An interesting experiment would be a 26" wheeled MTB with a nice wide 700c laced on up front. Curious.

An interesting experiment would be a 26" wheeled MTB with a nice wide 700c laced on up front. Curious.

I agree about the 29er wheel up front being better able to roll over obstacles. And now that you mention it, I think it's not all that uncommon to see a mountain bike set up that way (26" rear, 29" front) nowadays since 29ers are gaining in popularity. I haven't seen one in person (a 26"/29" combo), but I believe I've seen them in magazines (they call them 69ers, I think). The old Cannondales I mentioned above used a 24"/26" combo-

Differential wheel sizes main effect on the bike is to change the basic frame geometry, specifically, the effective head tube angle, which is the single most important factor in how quickly a bike steers.

Lets say your bike has a 74 degree HT angle with equal sized wheels. Put a smaller wheel in front, your effective head tube angle is now steeper than 74 and the bike will steer quicker.

If you put a bigger wheel in front, the effective head tube angle is now shallower and you will have a bike that steers less quickly.

Differential wheel sizes main effect on the bike is to change the basic frame geometry, specifically, the effective head tube angle, which is the single most important factor in how quickly a bike steers.

Lets say your bike has a 74 degree HT angle with equal sized wheels. Put a smaller wheel in front, your effective head tube angle is now steeper than 74 and the bike will steer quicker.

If you put a bigger wheel in front, the effective head tube angle is now shallower and you will have a bike that steers less quickly.

Agreed, I wouldn't recommend running an asymmetrical setup on a bike not designed for it. In the examples I mentioned in my above posts, the bikes' geometries are designed with the unequal wheel sizes factored in. The point is still to give stable handling, but you don't want to over-do it-

Thanks for the title stacey and replies everyone, I was thinking of doing 24"/26" if that makes a difference.

What about smaller front wheel? I know there's one brand of women's bike (the name escapes me just now) that have smaller front tires to fit into a tighter geometry for shorter people... But I seem to recall someone saying (probably here in BF) it's a big no-no.

You're probably thinking of Georgena Terry bikes. They may look a little funny, but the women who own them all seem to love them. I've never had a serious buyer test ride one and not buy it.

I suspect that the larger front rim question has to do with tire width. An inflated tire has a roughly circular cross section so a fatter tire will also be taller. Using a smaller rim diameter allows the designer to use a significantly fatter tire in the rear and still keep the rolling circumference of the two tires similar.