Sunday, November 05, 2006
Toe Overlap: No Problem
There was a discussion recently on Classic Rendezvous Bike list; the tread titled “Toe overlap even on good bikes,” implied that toe overlap was a design flaw and one should not expect to see this on quality bikes. Toe overlap is a result of other critical design factors and cannot always be avoided especially on smaller frames.
When a framebuilder designs and builds a racing frame, his main criteria are to: (1.) Place the rider in a position where he can pedal with maximum efficiency, and (2.) Design the frame so the finished bike will handle at speed in the best way possible. If the result of the design is toe overlap then the builder can do little because to achieve toe clearance other aspects of the frame’s design would have to be altered.
For example the picture above shows my own bike. It has a small 52 cm. (C to T) frame and has about an inch of toe overlap. If I were to make the front end of the bike one inch longer to avoid toe overlap, I would have to do one of the four following things or a combination of all four.
(1.) I could make the seat angle steeper, or (2.) the top tube longer. (3.) I could make the head angle shallower, or (4.) the fork rake (offset) longer. The first two would effect my riding position; the last two would affect the handling of the bike.
Toe overlap is not a problem because riding and cornering at normal speed the front wheel never turns far enough for the toe to hit the front wheel. The only time it becomes an issue is when turning sharply at a very slow speed; doing a U-turn on a very narrow road for example.
Caution and common sense are all that is required when executing a tight U-turn. If you are turning left then your right pedal will be down for maximum ground clearance as you coast into the turn. By the time you need to start pedaling again you are already half way through the turn, and the right crank has to complete ¾ of a turn before the toe is opposite the front wheel.
By that time, you should be all the way around and the front wheel is straight ahead again. If you are not the coast again, or ratchet the crank back again on the freewheel.
Doing the same maneuver with a fixed gear is a little trickier; but it is a matter of timing. Go very slow and start to turn as the toe passes the front wheel; that way the crank has a whole revolution to go before it makes contact again. If the front wheel is still turned the next time round; straighten the front wheel so the toe clears, then turn sharply after it has passed.
Fixed gear and fenders (Mudguards.) is going to make this move a little difficult, but not impossible. With clipless pedals, you could unclip the outside foot and move your toe back to give more clearance. I sometimes get out of the saddle and simply point my toe downwards to give more clearance.
What you need to avoid is a situation where you get your toe on the wrong side of the wheel in a turn; if you do, try not to panic. Ratchet the crank back if you have a freewheel, or if you are riding fixed gear, keep going and let the toe pass the front wheel so you can straighten up again.
Lastly, I would like to point out that a racing motorcycle with narrow swept down handlebars; turning is restricted because the handlebars touch the fuel tank. Here is a machine that will go 200 mph plus, and restricted turning seems not to be a problem. Therefore, I maintain the opinion that toe overlap on a bicycle is neither a design fault nor a problem.
Posted by Dave Moulton at 11/05/2006 12:20:00 PM