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Help with sizing, too much info out there.(11 posts)

Help with sizing, too much info out there.DougG
Jun 7, 2002 7:53 AM
How much standover should I have on a road bike? I'm 6'00" with a 83 cm standover using the Colorado Cyclist method of measuring with a book pressed firmly in your crotch. Their method says 55 to 56 cm. I went in a local bike shop and the guy told me "NO WAY, you need a 58!" I rode a Cannondale 56 and 58. The 56 seemed more comfortable, but I'm used to mountain biking. The bike shop guy said the 58 fit me better. When he saw I prefered the 56, his story changed to "that 56 will handle great for you!" I called another shop to check inventory and he told me that I was definately a 55cm.

How much standover do I need on a road bike. With both the 56 and 58 I'm lightly touching the toptube. The bike shop guy was telling me to pull the toptube up tightly and then he was measuring the gap between the front wheel and the floor. Is this correct?? I'm going to try another shop this weekend, but I'm afraid everyone just wants to sell a bike.

I'm afraid I'll buy what I think fits now, then regret it after I get used to the road bike fit versus mountain bike fit.
what you need..merckx56
Jun 7, 2002 8:04 AM
1- is a shop that may actually know what they are talking about.
2- the guy who told you to pull the top tube up is a moron!
that method is used when selling a 50 year old woman a hybrid! standover is a small concern simply because you aren't going to come of it like a mtb. i think i have about an inch over both of my bikes.
3- if you are 6' with a 32 inch inseam, a 56 cm bike with a top tube of between 56 and 56.75 will fit. the stem will be anywhere from 110 to 125. a good LBS will fit you and allow for stem changes upon the final fitting. if you have a longish torso (it sounds so), the 56 and a 120 stem!
I am 6' and have a 32 inch inseam. my eddy merckx is a 56 center to center with a 56 top tube and a 125 stem. my look is a 57 center to top with a 56.5 top tube and a 120 stem. the handlebars that are on the bike will also effect the reach, as all handlebars do not share equal proportions.
the 56 cannondale is the better choice, as it is a bit smaller than the 58 in standover and top tube. the 56 has a 56 top and the 58 has a 56.75 top. the rule of thumb that i always used when fitting someone was to find the bike that fit the best and was the smallest. i could ride a 58, 59, 60, but they all feel like i'm driving a truck. don't just buy it because it's a good deal. it's VERY slow in the shops right now and they want to move product! find what fits and make a deal then!
Seems mostly like bad advice.djg
Jun 7, 2002 10:46 AM
Point (1) is correct: you need a shop person who knows what he or she is doing and simply having you straddle a bike is a fairly impoverished way to asses fit.

Point (2) is partly correct: there's no precise amount of standover you really need on a bike, although if a bike is MUCH too tall you'll have problems mounting and dismounting (and will probably be lugging around more bike than you need). For many folks, the "inseam" measurement is a good enough proxy for calculating a frame size that works (or can be made to work with a little fiddling), but it's not ideal and can lead to very uncomfortable numbers if your proportions vary from the model. But trying to measure your own "inseam" (the real measure is not your inseam, properly speaking) with a book is notoriously unreliable. In fact, if you can level the wheels (blocking them is more reliable) actually pulling a seat tube firmly up into your crotch is likely to give you a better, not worse, measure of what we might call "cycling inseam." A couple of the fitting kits have a pretty simple tool for taking this relevant (but only one of several) measure in a reliable way.

Point (3) seems a little nuts to me. A good fit on the bike is not purely a function of the length of your legs--however you measure them-- and overall height and you cannot possibly know the poster's ideal reach based on those numbers alone. It's crazy to predict his "ideal" top tube within less than a centimeter, and crazier still to add a precise stem calculation. (And what's the angle of that stem, by the way?) Do you know anything about the guy's riding style? Flexibility? Upper body size? The length of his arms?

My own guess is that the crotch measurement is off. I'm basing my guess on the facts that: (a) my own measurement is 83 cm; and (b) I'm just 5'8" tall (a hair over, but 5'8 1/2" would be a lie) and do not have long legs for my height--in fact, my legs are a tad on the short side. Now, it's not impossible for you to have proportions that much different, but it's more likely that you mismeasured. Your own comfort on the bike is paramount--so nobody should discount your subjective impressions of your test ride--but I'd consider that what you like might change a bit as you do more road riding. And I'd ask around clubs in my area (or even more specifically on this board) for suggestions of a decent bike fitter.
I appreciated everyone's help, but...DougG
Jun 7, 2002 10:57 AM
in socks with the book pulled up tight into my crotch, it's still 83 cm. I actually had my girlfriend measure and she got 83 cm, 83.5 cm andt 825 or so, for an average of 83. I tried five minutes ago with a another book. If I pull the book up as tight as possible I come up with 84. But my eyes were about to pop out of my head!

Is it a problem it your privates are lightly touching the bar?? I ride more standover on a mountain bike, but I'm not sure about the road bike. I stood over a friends 55 at lunch and it felt fine. I didn't have time to actually ride the bike.
No, it's not a problem.djg
Jun 7, 2002 11:35 AM
Unless it bothers you.

Standing over a friend's bike comfortably is a definitive way to find out whether you can stand over a friend's bike comfortably. Interesting bit of trivia for some, but not terribly relevant to the question whether you can ride it efficiently and comfortably.

As I said, it's possible that you're right about the crotch measurement. But if you're going to do any substantial amount of riding and are going to spend an amount of money that matters to you, it's still useful to find a shop with a decent fitting service. They'll get you set up properly.
not to start an argument...merckx56
Jun 7, 2002 1:53 PM
but if you actually READ the post, point 2 is a valid one in that you obviously wouldn't buy a bike on which you had little to no standover. that's a no brainer. the guy has an 83 cm standover, which equates to 32.5 inches. i related my similarities in sizing as points of reference since they ARE so similar. maybe he has shorter legs, as i do, than most folks!
if his inseam measurement is off, then so be it, the whole thread would be rendered moot!
if you read the part about the final fit at the LBS, then you would plainly see that i do, in fact, explain stem fit to take torso, flexibility and arm length into consideration. i didn't think i had to spell it out! sorry! if you think that a centimeter on the top tube isn't much, you obviously haven't ridden an ill fitting bike for more than 3 hours... or maybe you are right now? I was giving rough parameters, not precise calculations, as you said, as a guide to go by. AND the numbers for top tube lengths were for a cannondale! which is what he is looking to purchase! if the shop he eventually decides on doesn't, or won't allow for such things as stem swaps (even weeks after the sale and fit) or seatpost swaps (ditto on the timing) or bars for that matter, he shouldn't buy the bike there.
people are obviously shaped differntly and have different goals in mind. if he is coming from a mtb background, a "race" fit would probably be closer than an upright, "tourist" fit.
recheck inseam...C-40
Jun 7, 2002 9:08 AM
83cm would be a short inseam for someone that is 6 foot tall. I have an 83cm inseam and I'm not quite 5'-7" tall. The standover height on a 58cm C'dale in 83cm. If you can stand over it in bare feet, your inseam is more than 83cm. Using a bike to check inseam is actually a good technique. If you block up the wheels (with boards or books) until you get saddle-like crotch pressure (in bare feet & cycling shorts), the distance from the floor to the top of the top tube will be an accurate cycling inseam.

To answer the standover question, 3-5cm is the common range. More clearance may create a problem with the handlebars being too low due to the short head tube length. Clearance could be reduced to as little as 2cm, but then you get a very low saddle, which produces a tourist or "Fred" look. As a quick reference, measure from the top tube to the top of the saddle, after the saddle is adjusted to the proper height. 16-20cm is a common range.

If you truly have only an 83cm inseam, you have a long torso, which does not make for a good fit on most stock frames. The 56cm would likely have too short of top tube length, but perhaps you could get buy with a 130mm stem. If your knees and elbows don't overlap significanly when riding in the drops, the reach is long enough, IMO. The saddle must also be adjusted for the proper fore-aft position, before a stem length can be selected.

The 58cm has a 1.5cm longer top tube (and would use a 15mm shorter stem), but may have too little standover clearance.

A possible alternative for the long-torso rider is the one of the new "compact" or sloping top tube frames. The sloping top tube would allow you to ride a larger size without the standover clearance problem. There a number of brands that now offer this frame design.
recheck inseam...DougG
Jun 7, 2002 11:25 AM
The 83 cm was bare feet. I stood over the bikes with shoes on, so that's how I was able to stand over the 58cm bike.
I'd say that he did the right thing, sort oflaffeaux
Jun 7, 2002 9:26 AM
There's a lot of personal preference in choosing a bike, and the fact that you rode a 56 and 58 is a good start. However before you buy anything ride more bikes.

Standover height is a good way to get in the correct size range. However, it's a bit of personal preference beyond that. Racers prefer slightly smaller frames, and long distance riders and tourers prefer slightly larger frames. I fit into the latter category.

If you have the clearance on a 58, I'd think that you'd be better off on that frame, as a longer top tube would probably fit your torso better. However, if the 56 is more comfortable to you, it's hard to argue with that.

I'm 6'0" with a 34.5" in-seam and ride a bike with a 59cm TT and a short 9cm stem. I used to ride a 56cm frame, but found that the bars were too low for my liking, and a larger frame brought them up nicely.
re: Help with sizing, too much info out there.dirthead
Jun 7, 2002 11:07 AM
I just went through the same thing! I wanted a Merckx Team SC, but didn't know for sure what size, and didn't want to fork out $1800 for a frame with just a guess at what size would fit me. Your best bet, if ordering a new bike or frame, would be to contact Cycles BiKyle, in Pennsylvania. Their website is www.bikyle.com. Kyle, the owner of the shop, is one of the best at fitting road bikes. Standover height is not the best way to fit a new bike. You should use all of your body measurements to size it correctly (arm length, leg length, torso length, weight distribution, etc.) Kyle will send you a measurement sheet, you will take your body measurements and return to him. He will them call you personally to discuss your riding style and what you want from the new bike. He will use your measurements to fit the frame to you, and also calculation stem length, saddle position, crank length, etc.

The frame you will receive will fit you as perfectly as it possibly can. I purchased my Merckx Team SC from him, and could not be more satisfied with the fit. For his fitting service to be free, you must purchase the frame from him, but his prices on all frames are at or below their cost on other websites like Colorado Cyclist, Jenson USA, etc.

I would suggest you give him a try, you won't be disappointed.
Any thoughts about the Wrenchscience.com site?B2
Jun 7, 2002 9:05 PM
Just for kicks I plugged in all the measurements into the wrenchscience.com website. Well, they came up with the exact frame size and top tube/stem length that I'm currently using. I am 6', 85.4 inseam..... they recommend a 57cm c-t frame and a 66.5cm top tube / stem combo length. I have no complaints, the fit seems perfect to me.

I kind of like the fact that they recommend top tube & stem length along with the frame size. Sad to say, most of the shops I've seen are just trying to sell what's on the floor. Was I just lucky or have others also found some correlation with the wrenchscience fitting??

Bryan