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SIZING, PROPER FIT...(10 posts)

Jan 24, 2002 7:18 AM
As a general rule of thumb, what is a great way to determine proper bicycle fit? I'm making the transition from MTB to road cycling! A friend told me my leg should be fully extended in the 12 o'clock position???
Woooooah there.Muncher.
Jan 24, 2002 7:24 AM
You are standing with an open can of worms, poised for a spliiage....

Get to a good shop and get them to explain/fit you up. If you can afford it - get a bio-fit (computer measurement/fitting) done.
Sound advicegrandemamou
Jan 24, 2002 7:51 AM
Get thee to a good pro shop and get fitted by an expert, if possible. Even if you have to pay for it believe me it's worth it. There are alot of myths and bad advice going around about fit even among bike shops. I'd talk to roadies in your area to try and find a good LBS.

Lots of set ups feel great cruising around the block but will it feel great after 4+ hrs in the saddle.
hope you didn't pay for that advicedzrider
Jan 24, 2002 7:48 AM
Fit is complicated and individual but most of us learn the feeling of a well-fitted ride. Start at a good shop, pay for a fitting if you can afford it, make really small (never more than 5mm IMO) adjustments until you get there.
Frame fitNessism
Jan 24, 2002 8:00 AM
As long as one is relatively analytical, it's not all that hard to fit yourself. Check out the following link and learn how to measure your body proportions (particularly leg length). Good luck.
here is my rough guidelineDog
Jan 24, 2002 8:12 AM
I think this is a common starting point:

Stand-over on a conventional frame (level top tube) should be around 2 inches; stand over the bike with your butt next to the seat; lift the bike; you should be able to lift the top tube around 2 inches.

When seated and with your bike shoes clipped in, the leg should be slightly bent at the 6 o'clock position with your foot level. This has more to do with seatpost height than frame size, though. Do this on a trainer.

The frame / saddle position should be so that when a pedal is in the 3 o'clock position (forward), the front of that knee is directly over the pedal spindle. If you have to move the seat radically forward or rearward to get there, you likely need another frame (either size or geometry with respect to the seat tube angle). Getting a frame that puts the seat about in the middle of the adjustment range allows you to adjust later on.

Top of seat to top of handle bar drop is a matter of personal preference, riding style, and lower back flexibility. As a general rule, you want the drop as much as you can comfortably and efficiently tolerate. As a guide, stand up and reach down to the ground with your legs together and straight. If you can place your palms flat on the ground, then try about 3-4 inches drop. If you can touch the ground, about 1-2 inches. If you cannot touch, level to 1 inch. Most riders start a little higher and then lower down as they become used to riding and the position.

For top tube (and stem) length, sit on the bike with your hands on the brake hoods. If you look down at the front hub, usually at a more or less correct fit the hub will be obscured by the top of the handlebars. This is subjective, too. If you prefer to be "stretched out" a bit and aero, then you might go a little longer. If you prefer to be more upright, you might go shorter. Depends upon your torso and arm length, too. Try to get a frame that puts you in the middle of the range using about a 115mm stem and then adjust from there with the stem.

Typically, a shorter wheelbase will have faster handling, and a longer wheelbase more stable handling. It sort of depends on you and what you plan to do. If you are going to ride criteriums, I'd go for a shorter wheelbase. If you plan to do 200 mile events or tour, maybe a longer wheelbase.

I think those are the basics that most people can agree upon as a starting point. There is no substitute for getting on the bike and riding it, though, even if on a trainer in the bike shop.

Finally, don't accept anyone's rules if they don't feel good. Human bodies are highly variable, and many "rules" don't account for this.

here is my rough guidelineBMW
Jan 24, 2002 8:16 AM
thanks for the fitting advice....BMW
2 in of clearance?colker
Jan 24, 2002 9:29 AM
hmm.. i would be ridin a bike that was way too small for me if it had 2 in of clearance.
with 81.5 cm of inseam, the formulas say i should ride a 53 c-c and a 53 bike has around 79cm from floor to top tube. so, with shoes i must have 83cm of inseam, less 79cm and...
2 in of clearance?Troyboy
Jan 24, 2002 1:26 PM
I've tried all those formulas, from CC to Lemonds. They're all different and none of them have me on my properly fitting bikes.
No No please! Not the "standover height wars" again....nmmuncher.
Jan 24, 2002 9:31 AM