Bike design help needed
02-04-03 | 05:06 AM
#26
Thread Starter
Zzzzzzzzzzz
Joined: Jul 2002
Posts: 385
Likes: 0
From: Somerset, England
Originally posted by MichaelW
I dont think a 5'3" female rider will fit onto a 19" frame. The modern trend for road bikes is to allow more crotch clearance (about 3"), but to maintain the same length. This means that a small rider may be able to clear the top tube like a 1970s racer, but the frame will be way too long.
Off-road bikes need even more crotch clearance (4-6"), and these bikes should be a little shorter in length, since aerodynamics is not critical.
A CX style 531 frame built for MTB wheel size would be ideal, but dont discount MTBs if you want a ready built frame. Quality mid-range Al or steel MTBs are not overweight and are easy to pick up used. The wheels can be very strong and light, and narrow CX or touring style tyres (1.5" wide) would be fine. If you dont like the heavy MTB forks, then swap them for a set of springy 531 for much improved performance.
A triple crank would be the best gearing solution. Short legs deserve short cranks (probably 160 to 165mm). My local bikeshop has a beautiful TA triple chainset in 165 for a mere £30, its is normally £160. If building from scratch, you can use short cranks to advantage to build a bike which is lower and shorter.
You could probably simplify your shifter problems by sticking with straight bars and bar-ends, or if you need multiple hand positions, butterfly bars. Standard drop bar shifters are not built for small hands.
I dont think a 5'3" female rider will fit onto a 19" frame. The modern trend for road bikes is to allow more crotch clearance (about 3"), but to maintain the same length. This means that a small rider may be able to clear the top tube like a 1970s racer, but the frame will be way too long.
Off-road bikes need even more crotch clearance (4-6"), and these bikes should be a little shorter in length, since aerodynamics is not critical.
A CX style 531 frame built for MTB wheel size would be ideal, but dont discount MTBs if you want a ready built frame. Quality mid-range Al or steel MTBs are not overweight and are easy to pick up used. The wheels can be very strong and light, and narrow CX or touring style tyres (1.5" wide) would be fine. If you dont like the heavy MTB forks, then swap them for a set of springy 531 for much improved performance.
A triple crank would be the best gearing solution. Short legs deserve short cranks (probably 160 to 165mm). My local bikeshop has a beautiful TA triple chainset in 165 for a mere £30, its is normally £160. If building from scratch, you can use short cranks to advantage to build a bike which is lower and shorter.
You could probably simplify your shifter problems by sticking with straight bars and bar-ends, or if you need multiple hand positions, butterfly bars. Standard drop bar shifters are not built for small hands.
Bar ends are a no no I'm afraid they are not used in cx or off road mtb they are quite frankly dangerous for this type of event and you would rarely have your hands on the ends of drops to change gear when you want to if going over rough stuff.
Staight bars are probably the most practical and comfortable and twist grip gear levers the easiest to use if we can afford them.
gears need to be on the top of the bars for quick easy reach so you can constantly make use of them to maintain optimum cadence,( We will probably use the sora 8 spd set we have to save wasting money.)
The triple c/s is very cheap at £30.00 but then you would need to change the front and rear mechs and chain etc so more expense. This event is mainly on tarmac probably 30-35 out of the 40 miles so the gearing needs to have a 50 t and 12 sprocket to use the down hill sections to gainback time. If there are any hills that require more than 38 x 26 then they would get off and run with the bike. After all it is a race and running would be quicker You don't see triples on cx events
I take your point about the crank lengths but we have a db 50/ 38 c/s with 165 cranks she has been using and to get another 5 mm will cost another £100.00 or so with no real advantage.
I am not really interested in trends of bike frame geometry for this bike. A cx type bike is not going to give as much clearance as a mtb but 19" has sufficient clearance and Kathy has been using a 19" frame for the past 3 years without problem.
We use a short rising bar stem to compensate for shorter reach
already
Not perhaps ideal but compromises have to be made to reach an all round satisfactory solution at a very tight budget.
Low Weight, comfort and ease of use are the most important goals to achieve for a 8 hour triathlon endurance race. Cheap mtbs weigh upwards of 28lbs and this bike will weigh under 20 lbs!
