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Once again with the bike fit questions...(14 posts)

Once again with the bike fit questions...Spinchick
Aug 31, 2001 1:24 PM
Okay, according to my calculations using the Colorado Cyclists bike fit guide, there are no frames with the geometry I need. If I find one with the tt length I need, it is usually too short height-wise. I have looked at the geometry of various models of Serrota, Kestrel, Trek, Cannondale, Waterford, Terry, etc., etc., etc. and nothing seems to add up. Am I doing something wrong or am I really going to have to do the custom geometry thing? Who does custom geometry? If I am missing something here I will truly feel like the "idiot." I really am not built like a gorilla...
Aug 31, 2001 1:30 PM
If the standover is sufficient, and tt right, what's the problem? That's 99% of fit right there. How much seatpost showing would you need? You can always raise the saddle and stem. Don't see the problem.

One step at a timeJon Billheimer
Aug 31, 2001 1:38 PM
If Doug's suggestion doesn't pan out, go find a bike shop that has a fit kit and get measured up. Then
you'll know. If a custom frame actually is required, Marinoni, a small Canadian manufacturer, does
excellent work at various price points. They also have a "stock custom" program in which they stock a
large number of sizes with various geometries one of which will fit 99% of the population. It's a good
program and they make good bikes at reasonable prices. You can probably locate a dealer by going
to their website.

But check out Doug's suggestion first.
Aug 31, 2001 2:20 PM
I checked out the Idiot's guide - said to add 2 cm to your inseam to determine standover. If that is correct (and believe me, I am open to being corrected on that one), my standover should be 81 cm. When I look at the frame geometry, I look for the standover closest (but smaller rather than larger) to that number. But then it seems the tt length is too short by at least a cm. I'm trying to avoid some of the problems I'm having with my current bike, ie my tt length is too short - even with a long stem and the seat all the way back. My standover is just fine.
subtract 2cm from inseam to get standover....C-40
Sep 2, 2001 5:09 AM
No wonder you're confused. Subtract 2-3cm from inseam to get standover! You can't standover a bike that's taller than your inseam. The idea is to establish some clearance.

If your inseam is 79cm, you need a 52 or 53cm frame which will give you 2-3cm of clearance.

If, by chance you did subtract 2cm, and your inseam is 83cm, you're my size, and need a 55cm frame. Most frames of this size will accomodate riders in the height range of 5-6" to 5-10" tall. I'm 5'-7" and fit most 55cm frames with a 110mm stem.

Many folks don't measure inseam properly. It should be done in bare feet. Use your current bike and block up the wheels until you get enough crotch pressure to almost lift your heels off the floor. The distance from the top of the top tube to the floor is you true inseam. Standover should be 2-3cm less than this dimension.

If you have to push the saddle all the way back and use a long stem (130mm?), something is wrong with your current ride.

The saddle location should be set based on your optimum knee-over-pedal (KOP) position, and should not be used to extend the reach to the bars. Using a seatpost like a Thomson straight-up design, rather than a traditional seatpost with setback can make it imposible to get the saddle back far enough. Be sure you're not making this mistake.

Remeasure and post your inseam and height for better advice.
subtract 2cm from inseam to get standover....cycleguy
Sep 2, 2001 6:53 PM
"Many folks don't measure inseam properly. It should be done in bare feet."

re: Once again with the bike fit questions...mackgoo
Aug 31, 2001 1:37 PM
How tall are you? What are the two measurements of your leg? One from where your hip rotates to where your knee rotates, then from where your knee rotates to the ball of your foot.
I think I would go for a frame that would give me a decent seat post height with out getting too high, with the correct size cranks and a seat set back that wasn't too radical. Then adjust the top tube length or really your reach with the stem.
I just heard some where the saying was a fist full of post, but that is changing some with the new sloping geometry
bike fitTig
Aug 31, 2001 3:11 PM
Online guides are good for general fitting, but are no substitute for a professional fitting from a qualified pro. The bike should fit like a glove. Fit formulas and guides don't work for everyone, just like stock frames may not fit everyone's bodies. A Serotta Fit Cycle or similar system is only as good as the tech helping you. If performed by a true pro (certified by the mfg), you can get dialed in and keep those accurate measurements for life.

If you want to go with a custom frame, I'd suggest finding a Serotta LBS. Go to to search. They didn't list an LBS that had the Fit Cycle, but a call to (518) 747-8620 helped locate them after all.
Found a Serotta dealer...Spinchick
Aug 31, 2001 3:19 PM
and will pay them a visit. Frankly, the Serotta frames came closer to any others when it came to matching my tt and SO measurements. Although I guess I'm still not convinced I did it right. Guess the "Idiot's Guide to Bike Fit" is aptly named :-/.
Bike fitters are FABULOUSPdxMark
Aug 31, 2001 3:41 PM
I paid for the full bike fitting at a Serotta dealer before I bought a bike, and the fitter steered me away from the bike I was planning to buy from that LBS (rightly, I think). The way the fitter put it, he could make the bike fit me, but I would not have been in a balanced position on the bike. No matter what, one of the main bike frame dimensions (seat tube, top tube) would be off by a couple cm from my measurements. I really appreciated the professional help with finding the right fit.

To further support this guy's ability, after I got the bike (not from that shop), he checked the sizing and said all was well except that my handlebar was 1 cm too low. I made the change, and the bike felt even better. I wouldn't have known to do that. (I had ordered the bike to his specifications, but I hadn't specified that one dimension.)

Even though I ride a few thousand miles each year, I don't know squat about bike fit. Or maybe anything else. I am a convert to the priests of professional bike fitting. Maybe rules of thumb will work on a Web site, but a trained fitter looking at you on a bike will give a much better fit. And if you're buying a spendy bike, it's a SMALL price to pay in comparison to a mis-sized frame.

PS. A couple sales guys in the shop had previously said there was no problem fitting me to that bike I had been lusting after.
re: Once again with the bike fit questions...peloton
Sep 2, 2001 6:34 AM
I agree with Dog. You should be able to find a fit that you can fine tune with seatpost, spacers, and stem. I think you are in the right direction though. It sounds like you are looking to get the appropriate top tube length for your torso. I think top tube length is far more important than is standover. Standover doesn't mean much as it used to, especially with the new compact frame designs. If your top tube reach is off though, it can make the bike feel pretty bad.

Bike fitters are good too. Remember though, it isn't an exact science. There are some parts of fit that you will just feel are right for you. There isn't a set number or formula for fit. Some people like to be stretched out more, others like to be far behind the bottom bracket and others close to on top of it. Some of fit is personal preference and style. Don't get bike fitter numbers and take them as gospel, they are just a good point to start from.

Custom is nice too. You will get a bike that fits you. Thing is though, that 99% of the people out there get custom bikes that really aren't that different from off the shelf designs. Most people's physical characteristics aren't that abnormal where a custom is absolutely needed. You can do a lot of things to bike fit by just adjusting what is there though stems, spacers, seatposts, and others. If you ask a custom builder though, you will be told you need a custom for your body. It's their business, they aren't going to push you out the door. If you do go that route though, you chances are will get a beautiful bike, well made and designed for you. You need to research first though if there really is no shelf bike that is right for you. Maybe there is, maybe there isn't. Do your homework and weight your options before you jump in though.
re: Once again with the bike fit questions...ET at home
Sep 2, 2001 6:48 PM
Not sure what your problem is. You add to 2 cms to your CC inseam to get your standover. You compare that to the bike's standover, which better be lower, and make sure the difference is between around 1 and 2.25 inches. While I agree top tube is more important than standover, I don't think you should entirely follow Doug, er, Dog. He is not typical and prefers around a five-inch drop between seat and handlebars, so he fits fine on a smaller frame exceeding the 2.25 inches upper limit. Others who need less differential might have trouble building up their stem high enough, given the limit of around 4 cms of spacers, and/or (if this matters) they might look like a dork with a stem angled way up. This is a common problem with the Trek Lance (i.e. OCLV) because its seat tube sizing is misleading, and so the 56 is really a 54 by others' standards, so some of those who just follow top tube (in this case, 56, coincidentally the same as the nominal seat tube size) find they can't comfortably reach the drops, if not the bars.

I claim that for your first serious road bike, at the least, the "idiot's" guide will get you real close, perhaps just as close, if not closer, than a Serotta size cycle (which missed a bit for me despite a credentialled fitter). The size cycle is more valuable IMHO for someone trying to fine-tune his/her current fit.

Why don't you state your height, your true CC inseam without shoes, your preferred top tube (how do you know what this is?) and we'll see what we can find for you.
Okay - here goes...Spinchick
Sep 3, 2001 6:35 AM
I am 5'5 1/2, my inseam w/o shoes is 80cm. The tt on my current bike is 52cm. Colorado Cyclist's fit guide says it should be 53cm. This would seem right to me because I think just a little more length would make it comfortable. My current stem is 11 cm and I've got the saddle back as far as it can go. I just borrowed a pair of aerobars on my ride yesterday and it made a difference in my comfort level. The too-short tt made less of a difference when I spent a good amount of time streched out over the bars.
Okay - here almost goes...ET
Sep 3, 2001 1:25 PM
I have my geometry charts at work and will give them a looksee tomorrow. Before I do, though, perhaps you can narrow things down by explaining what is causing you to have your seat all the way back. Please answer the following:

Did the seat still need to be all the way back when you tried the aerobars? If so, there may be more at play here than too short a reach.

Is there a standard setback on your seatpost, or is it clamped straight up from the seat tube? (Most of us have a setback, placing it perhaps two cms further back.)

What is the seat tube angle on your current bike? If it's very steep (e.g. 74) and you need something more like 73, that will cause you to have to push your seat much further back.