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View Full Version : 700c -> 650c on a Road Bike



JoHunter
02-07-2006, 12:57 AM
Hi everyone, I've just bought a very small road bike frame and had it fitted with standard parts to get me going. However when I saw the 700c wheels on it it's definitely all out of proportion. I'm worried that I might have a bit of toe overlap and would like to put some 650c wheels on it instead. Does this mean that I will have to change the fork as well? Or are there brake levers that will be able to reach it that extra bit further. Also I have the 170mm cranks and have heard horror stories of pedals scraping the ground when using smaller wheels. Fact or Wivestale? Thanks a lot!

SadieKate
02-07-2006, 08:49 AM
Why did you buy this bike if you don't like 700 wheels? Frames and fork are designed to be ridden with certain wheel size. Brakes won't fit, fork rake will be wrong, BB god only knows, I'm not an engineer. I've never heard of any adaptors to make brakes work.

I don't think I have one bike that doesn't have toe overlap. I've never had a problem, you just need to be aware of it. Didn't you determine overlap before you bought the bike?

fixedgeargirl
02-07-2006, 09:52 AM
However when I saw the 700c wheels on it it's definitely all out of proportion.

Forget how it looks, does it function?

Grog
02-07-2006, 09:55 AM
However when I saw the 700c wheels on it it's definitely all out of proportion.

What do you mean by "out of proportion"???

I have a very tiny frame and the wheels _do_ look very big on it. It _looks_ out of proportion, but it's correctly sized anyway.

I think you should be a bike fit with a professional at a reputable bike shop. But it is certain that your current fork, if it is made for 700 wheels, will not take 650 wheels.

Running Mommy
02-07-2006, 12:01 PM
I have a size 44 Specialized w/ 700's on it and it rides fine. I don't know what you mean by "toe overlap" but I've never noticed a problem. I guess when I look closer at my bike I can see how the wheels look bigger, but it doesn't bother me. Though My new tri bike will prolly have 650's on it as thats what the smaller frame sizes come with.

kiwi girl
02-07-2006, 12:25 PM
You say you are worried about toe overlap - but have you actually checked if it is an issue. I'm 5'1" and yeah both road bikes I've had look out of proportion - not wanting to offend anybody but I refer to them as mutant dwarf bikes - but I think that is part of their charm. I haven't had a problem with toe overlap.

JoHunter
02-07-2006, 02:19 PM
Hi everyone thanks for the replies. I was unable to judge the toe overlap on this bike prior because it is a custom made frame (not for me, a second hand one I found in my size). My LBS was willing to fit it with standard parts. I wasn't sure if the fork of the bike was to accomodate 700c or 650c wheels. Now that I actually have it with the 700cs there is a bit of overlap. Depending how I turn it my toes clip the front wheel, so I have to be a bit careful with it. I may end up getting shorter cranks that might help. From various different sources I found that a lot of people recommended the 650c wheels for shorter people to help with acceleration and climbing hills. I have heard of people turning their road bikes into tri-bikes and wondered if they bought new forks or found long-reach brakes.

Actually thinking it about it now, it is very odd that a custom built frame would have the toe overlap problem. I would think most small frames that were made to accomodate larger wheels would make the effort to avoid it.

fixedgeargirl
02-08-2006, 09:39 AM
I was doing some investigating re: crank length yesterday. I learned that a longer crank length allows for better leverage but dictates a lower cadence. Better for power on an off-road machine. Shorter cranks allow a quicker cadence, better spin and don't require the knee to achieve as intense an angle (SAVE THE KNEES :D !)

I also came across some calculations vis a vis crank length as a percentage of femur length. Can't find the link now, but the gist of it is that even 165s can be *too long* for a petite woman. But then there's the study Sheldon Brown links to regarding wattages produced using different crank lenths (from 120-220 I believe) with the greatest wattages being produced using the mid-range cranks.So much information, is that smoke coming out of my ears....;) ?

Anyhoo, I'm 5'3", 27" inseam, on a custom frame with 165 cranks. Have 165s on all my bikes and feel loss of power and sad knees on anything longer. Shorter cranks might benefit you in many ways, including eliminating the overlap issue.

SadieKate
02-08-2006, 09:44 AM
Depending how I turn it my toes clip the front wheel, so I have to be a bit careful with it. Is this when you are riding or when you are standing in the parking lot with one foot clipped in?

Kathi
02-08-2006, 10:26 AM
Hi everyone thanks for the replies. I was unable to judge the toe overlap on this bike prior because it is a custom made frame (not for me, a second hand one I found in my size). My LBS was willing to fit it with standard parts. I wasn't sure if the fork of the bike was to accomodate 700c or 650c wheels. Now that I actually have it with the 700cs there is a bit of overlap. Depending how I turn it my toes clip the front wheel, so I have to be a bit careful with it. I may end up getting shorter cranks that might help. From various different sources I found that a lot of people recommended the 650c wheels for shorter people to help with acceleration and climbing hills. I have heard of people turning their road bikes into tri-bikes and wondered if they bought new forks or found long-reach brakes.

Actually thinking it about it now, it is very odd that a custom built frame would have the toe overlap problem. I would think most small frames that were made to accomodate larger wheels would make the effort to avoid it.


It's not so odd having toe overlap on a small frame with 700c wheels. It depends on who made the frame and what material it is. I'm planning on building a custom frame and I was working with a well known company that does custom build. I'm looking at a ti or ti/carbon combination. The frame I wanted is only available with 700c wheels because the company doesn't make a carbon or ti rear triangle small enough for 650c wheels. So I would have a 44cm frame on 700c wheels plus the spot where the tt and rear triangle meet wouldn't match up. Also, I would have 1cm of toe overlap.

Since there are other companies that can do small frames with 650's I nixed this design.

JoHunter
02-08-2006, 10:41 AM
fixedgeargirl: Thanks for the information, I've read a few articles that agree with you on crank length and have found a place that will sell me the shorter 165mm cranks. I'm hoping this might help my legs as well as help avoid the overlap problem.

jcl
02-17-2006, 08:52 PM
Hi JoHunter,
The toe clip overlap problem can be pretty bad on smaller frame bikes. I test rode a 47cm WSD Trek, a 48cm men's Cannondale, and a 47cm Bianchi Eros Donna, all with 700c tires and 170 cranks, and I found the overlap problem significant, significant enough to make me want to avoid it at all costs. Like you, I began to research the idea of retrofitting 650c wheel/tire combos, but was told that the brake setup would not work with the smaller wheels.

I'm 5' 4" and I have a shorter torso, and hence a bit of a reach problem. I need an effective top tube distance of 19.5-19.7 inches.

Eventually I began to research the possibility of a custom-built road bike, and became a regular visitor to the sites of Luna Cycles, Waterford, even Litespeed! Unfortunately, all of these great products were out of my reach money-wise. I'm a cycling newbie, and while I am wildly enthusiastic, some might say even obsessed, with the sport, I could not justify spending 3K plus on a new toy.

Finally, I stumbled upon the site for Rodriguez Cycles in Seattle. They make custom bikes for the hard-to-fit. They use 650c wheels on their smaller frames, and in addition, the women's road design has a more relaxed geometry than is typical - the top tube is sloping, the head tube is longer. I ended up ordering a custom bike from them, steel frame, 650c wheels, 165 cranks, and Campy setup for a little over 2K.

I received the bike this afternoon (waited by window all day for brown UPS van to appear), and I must say, it looks great! Because of all the rain in L.A. today, I was only able to ride it slowly, in circles, around our underground parking. Even with all the customization, there is still a bit of an overlap problem when I clip in to the pedals, but it is far less than it was with the other 700c/170 crank bikes. From my viewpoint in the saddle, it looks like 1cm of overlap, but that's a guess.

So in closing (I know, long post), I would like to say that I do not think that the toeclip-overlap problem can be entirely eradicated in a small-framed road bike design. If you talk to a builder, they'll sketch you a diagram of the bike, and show you the wheelbase and the angles that work, and then I think you just have to decide what you can live with. But smaller wheels and cranks do minimize the problem.

Good Luck with your search!

JCL

Eden
02-17-2006, 11:05 PM
I have a Fuji 44cm frame with 700's and 165 cranks. I've been informed by various sources that the setup shouldn't work at all and that the angles are all weird to accomdate the larger wheels, but it fits me to a tee. I'm short with shorter torso and arms than legs. I used to have a bigger bike and can stand over a taller frame, but I really need the shorter top tube. I have no overlap problems at all- I do have small feet - size 4.5 road shoes. As far as the crank length goes - longer ones would mess up my knee position which is pretty darn perfect now, so even if it wouldn't cause overlap I wouldn't want to change it.

I haven't ever had a bike with 650's so I can't say that I know what the difference would be like. I've heard that smaller wheels climb better, but you end up having to spin faster to keep up on the flats. I've also heard that you can compensate with the gearing. I would love to take one for a test spin someday just to see which feels better to me.

doc
02-18-2006, 05:39 AM
Toe overlap is a hugely overrated problem. It only occurs when you turn the wheel a significant amount. When actually riding, one turns the wheel very little and uses a shift in weight to take a turn. Shoe size does affect the degree of toe overlap.
As for crank arm length, there are a lot of formulas out there. The one I see repeated the most is inseam (with shoes on) in cm x 2.14 = crank arm length in mm. Here are some websites:
http://www.nettally.com/palmk/crimplic.html
www.sheldonbrown.com/cranks.htm
and so many more...

jcl
02-19-2006, 08:53 AM
JoHunter,
I forgot to mention that the Terry Bikes website has lots of good info on women's fit...
http://www.terrybicycles.com/cycling_savvy/fit.html

summer
07-05-2006, 03:28 AM
I've got some similar fit problems to those here, although I'm 5'3" and ride a 51 time trial, so not really a teeny frame. I tried 650 wheels before I bought my bike (on 700s) and I didn't find much difference in practice in climb and acceleration; certainly not enough to make up for losses downhill and on the flat. One thing's for sure; don't put 650 wheels on aframe built for 700s. Nothing will work. Also, there's less choice in wheels and tyres for 650, and if you get into trouble on a ride or at a race it's harder to borrow kit. Try to borrow one first, before you commit.

I have a bit of toe overlap (I also have big feet) and I ride 170 cranks (I actually fit 167.50 but those are hard to find). Out on the road though, it's never been a problem, but maybe I just haven't turned sharp enough (although if you're turning that sharp you probably shouldn't be leading with you're outside leg anyway, for balance). best thing is to get a professional bike fit and then try to get your bike to match it as best you can. Custom bikes sound great, but I've heard of ther examples where frames didn't work so well (including a time trial bike where the rear wheel actually rubbed the seat tube because the cutaway was in the wrong place!)

Good luck!

madisongrrl
07-05-2006, 08:07 AM
http://www.slowtwitch.com/mainheadings/techctr/650ctoday.html

Nanci
07-05-2006, 09:41 AM
Interesting how he says his training partner who weighs less than the others descends faster, and credits this to 650's. I've also noticed my bike descends fast compared to others.

Nanci

profŕvélo
07-05-2006, 11:36 AM
Toe overlap is a hugely overrated problem. It only occurs when you turn the wheel a significant amount. When actually riding, one turns the wheel very little and uses a shift in weight to take a turn. Shoe size does affect the degree of toe overlap.

I agree with Doc that toe overlap is an overrated (and misunderstood) phenomenon.

The custom fit kit at Seven Cylces has an excellent explanation of toe overlap and how trying to eliminate it completely often means a sacrifice in the bike's handling. I would simply copy it here, but it's a PDF. I highly recommend that you read these few paragraphs (on page 7) before deciding that you must eliminate toe overlap at all costs, because there are probably costs involved.
http://www.sevencycles.com/order/CustomKit2006.pdf

CycleChic06
07-07-2006, 12:11 PM
What exactly is toe overlap? Is that when you turn the wheel and it hits the tip of your toe?

If that's the case then I have toe overlap, but only when I turn the wheel at a wicked angle, which never happens when I'm riding. I think I'd kill myself if I turned the wheel at that kind of angle while riding.

wabisabi
07-07-2006, 04:15 PM
My Rivendell is 52cm, and has actually 559 wheels (like mtb 26"s). Part of the iconoclastic charm of a Grant Peterson bike--he says you have to have those size wheels to avoid toe overlap and also have room for fenders.

Yeah, it is kind of a cult :p I've not had another good road bike, so I have no basis for comparison, but it's always felt just great to me.

One downside is that I have to carry my own tubes, and it was a chore to find tires that were 25s (Continental Gran Prix makes them).

Triskeliongirl
07-08-2006, 08:27 PM
I agree with Doc that toe overlap is an overrated (and misunderstood) phenomenon.

The custom fit kit at Seven Cylces has an excellent explanation of toe overlap and how trying to eliminate it completely often means a sacrifice in the bike's handling. I would simply copy it here, but it's a PDF. I highly recommend that you read these few paragraphs (on page 7) before deciding that you must eliminate toe overlap at all costs, because there are probably costs involved.
http://www.sevencycles.com/order/CustomKit2006.pdf

FYI, while many solutions do effect bike handling (i.e. messing with the fork rake, head tube angle, fork trail, etc.) Georgena Terry's solution of a 24" front wheel does not effect handling. But, by using a 700cc rear wheel, you can still use gearing designed for a 700cc wheel. I have seen many women in my club hurt with TCO, and I personally won't accept a bike with it. Yes, when we cycle at high speeds we turn mostly with our bodies, but there are situations when one needs to turn the handlebars.