Custom Bike - 650 vs. 700 wheels

[TxDoc]

Hi Susan,
first of all let me throw in a little disclaimer: I am not an expert or a pro, so put whatever I say in perspective.
I would strongly recommend 700c. The advantages are enormous - one above all being the endless choice of wheels and tires for 700c. You can find the best wheelsets in this size, both clinchers and tubulars.
The perceived 'issues' with 700's on small frames are really not a deal in my opinion:
The slower acceleration is rarely an issue - as most pro racers can demonstrate, since they race 700's.
People that suggest 650's to avoid toe overlap make me wonder whether they plan to ride in a parking lot at 4mph. Toe overlap is basically never an issue in road riding because 1-we do not usually steer, and 2-we do not ride slowly enough to even encounter that problem. So that is sort of a myth the way I see it.
I would go with 700c wheels, and pick a wheelset you like.
Oh, and by the way - CONGRATS on your custom build!!!

[sbctwin]

I, as an owner of a Bella Lightspeed with 650c wheels, had little choice for my selection. At 4'10" when I looked for a new road bike, I wanted a bike that fit. I was tired of 'make do' with what was out there. Now, at 4'9.75" or less, I am happy with the 650c's on my bike. I sure wish I could ride a bike with 700c wheels, but I can't!! or do I say, I shouldn't ... I am happy with Bella, because it will be the last road bike I purchase, I hope/... My mom, bless her heart, had shrunk in inches to 4'6" before she died. My twin still holds out to be 4'11". I know, as I get older, I won't be as tall and at close enough to be 56, I want a bike that will last me until I can no longer ride and that probably means when I am dead because I hope to be riding in some fashion until then!!! I am in the market for a new commuter and it has become increasingly difficult to find something that will fit me until I am 65 and hope to retire...I may just save enough pennies for that custom bike

[Triskeliongirl]

I ride a 48cm cervelo RS w 650c wheels. Its the best handling bike I ever had, and there is no toe clip overlap. I have no problem getting tires (love the schwalbe stelvio 23c), and in a pinch you can use a folded over 700c tube. The aesthetics are great too (see pic attached). I posted the pic to make the point that everything on a bike needs to be proportional, so it makes sense that a small frame will have small wheels, shorter reach bars, etc.

If you want wider tires (terry makes a 28c) or do like Deb, and ask your builder to make it so you can swap out 650c and 26" wheelsets.

I think its crazy to build a small frame around 700c wheels unless you require neutral race support that only carries 700c.

Regarding the gearing, its true that the gearing will be lower for the same chain rings, but I found for me it made it easier to gear the bike a tad lower which is great for climbing. Mimi, there is no reason to believe you would work harder with smaller wheels as long as you choose an appropriately sized chain rings and casette.

So, while there are more choices in wheel and tire for 700c, there is no shortage of excellent wheels and tires in 650c, although you may have to mail order.

[Bluetree]

Wheelsets. Wheelsets. Wheelsets.

700c wheels allows me options and benefits that just aren't possible with 650's. I can borrow wheelsets from teammates to test them out, experiment with types/weights, and get great deals with members of the local community. I've experienced tubulars, deep rims, carbon, ultralights, bladed spokes, you name it -- and marvelled at how the different technologies transform how my bikes roll. Speaking for myself, I know I would be sorely disappointed if I didn't have those options. YMMV.

[sarahkonamojo]

Reading between the lines. You WANT the 650 bike. So maybe you should just get it. And see what the fuss is about.

Seems the only negative to the 700 is the toe overlap. And aesthetics, PLLLEASE, nothing beats a new ride. Besides you will be on it, not looking at it ride by.

sarah

[Triskeliongirl]

It a little more complicated than that. Cervelo has some good info. on this at their website, as they offer 48cm riders a choice of the RS w 650c or the R3 with 700c, which they think are the two most accptable solutions, which I agree with: http://www.cervelo.com/bikes.aspx?bike=RS2009#G.

To build a small framed bike with 700c wheels, one of three things have to happen to fit the 700c wheel. One is severe toe clip overlap, which some people think isn't a problem, especially at high speeds on a racing bike, but clearly there are mixed opinions on this, especially for a more multi-use bike (and I have friends that have taken bad falls, or just got sick of always having to think about it, and some of us do need to navigate moving in and out of parking lots a couple times a day or traffic at slow speeds where it is a problem, but this is clearly an issue we will all have to agree to disagree on, it is very personal). There are many good racing bikes built this way, including the R3, blue, etc., so its clearly an option, especially for women who race and want access to a wider variety of high end wheels as blue tree mentioned.

The second option is changes to frame angles to accomodate the larger wheel in an attempt to reduce tco. Usually this means increasing the fork rake to push the front wheel further away from the rider, but this results in a bike that is too stable and handles poorly (I test rode a 50cm trek madonne that had this problem, it was very hard to get it to turn, felt like I was driving a mach truck).

The third option is to build the bike with too long a top tube, and expect the rider to accomdote with a very short stem. This also results in a bike that handles poorly, because it is too twitchy since the steering arc is dramatically reduced. (Or in this situation a rider could also push the saddle too far forward which effects their effeciency and balance on the bike).

SO, pros of 650c wheels are no toe clip overlap and good handling, with a reduced but adequate (at least for most of us) supply of high end wheels.

THe pros of 700s are a wider supply of high end wheels, but either severe toe clip overlap or compromises to the frame geometry that will effect the handling.

From what Susan says she wants this bike to do, I would recommend 650.

To understand better why its hard to fit a 700c wheel in a small framed bike, view the videos here: http://www.terrybicycles.com/videos
especially frame design 1 and 2.

[Triskeliongirl]

FYI, I pasted this nice explanation from the link I gave above from the cervelo website which I think gives a pretty balanced explanation of the issues (and they do sell 48cm bikes with both wheel sizes):

You will notice three geometric changes on the RS.

Longer headtube, to match the higher handlebar position.
Longer chainstay length. Because a higher handlebar position rotates the rider’s torso and therefore his center of gravity backwards. Longer chainstays ensure the weight distribution between the two wheels remains balanced for optimal handling characteristics.
Eliminated toe-overlap by using 650c wheels for the XS size. Toe overlap is not a problem for experienced riders, but can be intimidating for some. Using 650c wheels in the XS size is the only way to solve this problem without compromising the weight distribution and thus handling. Every solution that eliminates toe-overlap but keeps 700c wheels suffers in handling.
Explanation for the 650c wheel solution on the XS size: A smaller frame means the front wheel moves closer to the rider’s feet, causing toe-overlap. While inconvenient at walking pace, this issue disappears at normal riding speeds as the actual steering angles become very small. There are four ways to deal with this:

1) Accept toe overlap, after all it is not a problem if the rider is aware of it at low speeds, and it does not occur at higher speeds.
2) Use 650c wheels, which allow us to move the wheel closer but thanks to its smaller diameter it will never touch the rider’s toes.
3) Leave the front wheel far out front, but then the weight distribution will not be balanced.
4) Mess up the rider position by moving the rider forward instead of the wheel and handlebar rearward. But a changed position will not be comfortable, and the weight distribution will again be compromised.

Compromised weight distribution and therefore handling make options 3 and 4 unacceptable, leaving options 1 & 2. If you are a racer and neutral support is important, or you want commonality of parts with other 700c bikes, then option 1 is the best solution. We offer this on most of our road bikes. Option 2 is a great solution if you are concerned about toe overlap, never need neutral support and carry a spare for yourself (since your riding partners will likely have only 700c spare tubes, although even those work in a pinch, just fold them in – no problem).