I have an old cannnodale aero frameset ( tt bike, relaxed geometry- I think around 74 degree seat tube), and was thinking of having some fun with it and putting a 650c front fork and wheel to get lower in the front. would this work with its geometry? do ‘funny bikes’ have a special geometry to accomodate the smaller front wheel? you might save me some money with your advice before I do this…
thanks!!
Of course you can.
You won’t have any brakes and you will fall on your head of course…
Yep. Dunno what speedsnake is talking about… as your brake mounts are on the fork.
speedsnake was thinking wheel, not fork.
It will change the geometry some, not sure about the amounts. The headtube and seattube will get more steep. Never tried it though to see how it will change the way it handles.
Give it a go! - if you have a rigid fork MTB with the right size steerer tube you could try that front end out to check the handling before spending any $$ on it?
I suspect that you are goint to end up with some pretty quick steering by angling the front end down like that you are steepening the fork rake & also putting more weight over the front wheel - I would personaly try to suss it out for free before spending too much, but it sounds like an interesting project
Bikes were available before like that. I remember for smaller frame sizes that was the norm for Puegot. But didn’t rules change where that was not legal to do?
I am probably talking out of the wrong orifice, so take this with a huge grain of sand, but you might want to estimate the tracking distance. Check some of slowmans’ articles on geometry and what not.
I think with the canting down of the front end with the shorter fork, you might be decreasing the tracking length which could effect handling. The solution would be a fork with a bigger angle at the bottom for the droputs, if that makes any sense in english.
Ditto it affecting the handling.
"The solution would be a fork with a bigger angle at the bottom for the droputs, if that makes any sense in english. " Look at the rake measurement. Or just try it and see how it feels…
Actaully, as the head angle increases, the rake needs to decrease to maintain trail…
Bikes were available before like that. I remember for smaller frame sizes that was the norm for Puegot. But didn’t rules change where that was not legal to do?
What you’re thinking of were called “funny bikes”, at least that’s what we call them where I come from. 650 wheel on the front, 700 on the back. I’ll still see one in transition occasionally, or maybe I should say infrequently/rarely. I seem to recall Joe Bonness on one at IMLP in 2001(?). They’re not precluded in the rules. I have no idea what was what regarding the geometry, fork, rack,trail.
I think there’s reference in old “Kona Bike Counts” somewhere on ST (tech center maybe?).
By some rough calcs the angles would increase by ~1.7deg
front end drop by ~30mm
650 forks usually have less rake, even if you found one with 10mm less rake than the 700c fork you would still lose 9mm of trail.
Up to you whether you feel safe doing so. Other consideration is throwing the ground clearance of your cranks out.
I think I read funny bikes are illegal(now) in some sports rules, not sure which. I tried it while I had 700 and 650 bikes. The steering didn’t bother me but teh cranks are lower and seat able changes.
Uci rules say 2 wheels of equal diameter. Proper funny bikes were designed to have have odd sized wheels, though friends who’ve ridden such bikes didn’t thenk they were well designed for the purpose.
Correct. uci says wheels have to be the same size ( but only for national and international championships). Other than that you can still ride one. I have a Panasonic Team TT. 24" front wheel 700c rear. Its still faster than my Bianchi Crono.
Hello Rob99 and All,
It is legal for USAT to have different sized front and rear wheels. (But not for UCI)
** 5.11 Bicycle Specifications. All bicycles and bicycle equipment used in USA Triathlon sanctioned events must conform to the specifications set forth in this Section. Any participant using a nonconforming bicycle or otherwise violating this Section shall be disqualified. (a) Length cannot exceed two meters, and width cannot exceed 75 centimeters. (b) The distance from the ground to the center of the chain wheel axle must measure at least 24 centimeters. (c) A vertical line touching the front most point of the saddle may be no more than 5 centimeters in front of and no more than 15 centimeters behind a vertical line passing through the center of the chain wheel axle, and the cyclist must not have the capability of adjusting the saddle beyond these limits during competition. (d) The “front-to-center” distance, which is defined as the distance between a vertical line passing through the center of the chain wheel axle and a vertical line passing through the center of the front axle, must measure not less than 54 centimeters, except where the distance between the center of the chain wheel axle and the top of the saddle is less than 71 centimeters, In this case the front-to-center distance cannot be less than 50 centimeters. The “front-to-center” distance must measure not more than 65 centimeters, or seven-eights of the distance between the center of the chain wheel axle and the top of the saddle, whatever is greater. Applicability of the two foregoing exceptions is determined by measuring from a point on top of the saddle which is 14 centimeters behind the front most point of the saddle. (e) There must be no protective shield, fairing, or other device on any part of the bicycle (including frame, wheels, handlebars, chain wheel, and accessories) which has the effect of reducing resistance. Aerodynamic carriers for food, water, and or cycling provisions may be attached to or be an integral part of the aerohandlebars if they meet the following guidelines: (i) the carrier can pass from front to rear, through a rectangular loop with dimensions of 10 inches (25 cm) in width and 8 inches (20 cm) in height.(ii) The front of the carrier is behind the cyclist’s hands when the hands are placed in their customary position on the end of the aerobars, and (iii) The length of the carrier is no greater than 10 inches (25 cm) front to rear. When the carrier is an integral part of the aerobar, this integrated unit must be able to pass through the rectangular loop defined in (i) above and the carrier portion of the unit must meet criteria (ii) and (iii). In the event that compliance with this section is in doubt with respect to any particular carrier or integrated unit, a member of USA Triathlon may submit the carrier or integrated unit to USA Triathlon for evaluation. (f) No additional equipment, whether it is worn under the competitor’s clothing, over the competitors clothing, or is otherwise attached to the athlete’s body, which has the effect of reducing wind resistance is permitted. An exception is the use of safety helmets as described in Section 5.9. Such helmets may have the effect of reducing the wind resistance of the head only. (g) Except as otherwise determined by the race director in the interest of safety, the front wheel may be of a different diameter than the rear wheel, but the front wheel must be of spoke construction. The rear wheel may be either spoke or solid construction. Wheel covers shall only be permitted on the rear wheel. (h) No wheel may contain any mechanism which is capable of accelerating the wheel. (i) Handlebars and stem must be fashioned to prevent any danger. All handlebar ends must be solidly plugged to lessen the possibility of injury. (j) There must be one working brake on each of the two wheels. (k) All aspects of the bicycle must be safe to the user and to other participants in the event. Minimum safety standards include, but are not limited to, properly glued and sealed tires, tight headset and handlebars, and true wheels. 5.12 Untraditional or Unusual Bicycle Equipment. **Any unusual bicycle construction or equipment to which the specifications in Section 5.11 cannot easily be applied shall be illegal unless prior approval is received from the
Head Referee before the equipment is used in the event. Any violation of this Section shall result in disqualification.
When I got my new P3C (700c wheels) I still had my Softride with 650 wheels. I put the front 650 on my P3C (don’t need no stinkin’ brakes in front) and it seemed to work just fine.
(I did not change the fork for my test which would drop it down another inch or so and change the handling somewhat.)
I tried going around corners, up hills, down hills, etc.
I tried it and it worked just fine - although many told me it wouldn’t handle well.
I think it depends on how steep you want to get and what your back can handle.
I could get steeper than my tired old back could handle just using the regular 700c front wheel so I did not need a 650c - and I didn’t want to carry two sets of tire repair equipment.
Cheers,
Neal
Bikes had the small wheel in the back for awhile.
And then small wheel in front for fastest position for UCI hour record. (this setup later banned by UCI)
wow- some great advice here- just what I needed. thanks everyone- I will look for a fork with less rake and give er a go!
ps- remember when ullrich ran a 28" rear and 650c front on his tour tt bike ( or maybe it was 28 rear/700c front)? now that is what I am looking for, although I am sure it is a pain to replace those tires…
just to add to that, ITU rules state that both wheels must be the same size.
If you don’t change the fork it will affect the handling negatively… Joe Boness used to run a custom Elite (I believe) with a 700 rear and 650 front so maybe his wife who posts here (can’t remember her handle) can comment on the fork he used. If I’m right about Elite you can email them. I’m guessing that since it was a custom, though, the angles were correct and it just used a standard 650c fork, whereas retrofitting a 650c wheel into a 700c frame will change the angles.
This is the custom Elite 650/700. I believe David made a few others. Joe is now riding a Trek TTX, but says the Elite was a fast ride, great bike. Joe’s old Nishike was even more radical, 24in front, and more squirrely to handle too.
