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Right bike size.....(8 posts)

Right bike size.....Rollingbones
Sep 8, 2001 7:34 PM
...I'm a mountainbiker who's about to purchase a road bike (some would say I'm selling out, but I don't think so). Any hoot, I'm 6'0" and wear a 30" inseam trousers. I usually ride a 18"-19" mountainbike which is a bit on the small/normal range for me I think I'd like a bit more frame under me on the road. Soooo who out there has an opinion (and please no wise-cracks) as to an appropriate frame size(not to mention all that metric centimeter hooey). I'd like to have it narrowed down a bit when I start shopping. Any help would be appreciated...Thanks!!
re: Right bike size.....Skip
Sep 8, 2001 7:55 PM
Check out Colorado Cyclist's web page - specifically on bikefit - very informative, and a good place to start. It will guide you through taking the right measurements. For the inseam measurement, you need to take it in your stocking feet, with your feet approx. 6" apart; then hold a level, or board in level position, etc. as tight as you can against your pubic bone (just to the point you want to raise up on your toes because of the pressure) - this is your inseam. If you took it in inches, the multiply this number by 2.54 to get centimeters. Good luck.
re: Right bike size.....Akirasho
Sep 8, 2001 8:00 PM
... first, remeasure your inseam... your trouser measurment is not as "intimate" as your cycling measurment.

Have a good friend... help you in getting an accurate inseam measurment. There are a few more variables to consider (see above links) but this will get you in the ballpark as you dial in your fit (and shop for bikes).

All the above methods are a variation on a theme and allow for an individual's personal needs and tastes.

Remember, it's 2.54 cm per inch... and since most aspects of road bikes are measured metrically (the chain is an exception), might as well get used to it now.

And when you shop, remember that many good roadie shops will offer a fit session at a nominal charge (usually goes towards the purchase of a bike if you buy from said shop).

Fit on a road bike is a bit more critical than a MTB... cuz your position is more static. Don't forget to look at torso and arm length as well as you dial in your fit (again, the above links illustrate the point). Once you've amassed your personal anthrometric data, you can reliably predict which frames will or will not work for you (bought a GT Vengeance based mainly on it's top tube and head tube lengths).

Once you're ready, come back to the forum and ask specific questions about the bikes (frames are the heart and soul... consider the frame attributes as second only to fit) you've seen... chances are, someone will have an opinion that you can use...

Good luck and...

Be the bike.
short legs...C-40
Sep 9, 2001 5:04 AM
You have short legs for a 6'-0" height. I also wear 30" pants, but measured for cycling, my inseam is 32-5/8". I'm only 5'-7" tall.

If your legs are really that short, a proper vertical fit will require a 54-56cm frame, but the top tube on this size of frame will be too short. A custom frame may be required. Post again when you get accurate info from the web sites that have been listed.
C-40 I have..........bear
Sep 9, 2001 9:41 AM
C-40 I am 5'9 and have 33 inseam, if I go by my inseam the top tube is so darn long,,and I have trouble reaching the hoods even on a tipical set far I replace the stem and next is the handlebar for a short and shollow modle... I think my correct size might be a 52cm and just play with the seat hight and stem next time,,any ideas? I cant go custom,,kids in college.... any comments are welcome.
top tube shouldn't be too long....C-40
Sep 9, 2001 3:45 PM
You are 2 inches taller than me, with a 1cm longer inseam. Your proportions appear to be fine for getting a good fit on a stock frame. If you've measured your inseam correctly, a 55-56cm frame with a 55-56cm top tube should fit fine, with a 100 to 110mm stem.

I ride a 55cm frame, which has a 54.3cm top tube and a 74 degree seat tube angle (STA). Note that top tube length and seat tube angle must be compared together. My C-40 with it's 74 STA and 54.3cm TT length is the same as a frame with a 73 STA and a 55.5cm top tube (Litespeed for example). The top tube length on the Colnago is effectively lengthened by 1.2cm, after the saddle is moved back to produce an identical KOP.

I like to use my bike to double check my inseam and standover clearance. If I but a board that is 1.5 inches thick (standard 2 X 4) under each of the wheels, I can just barely standover the bike in barefeet. The top tube pressure almost causes me to lift my heels off the floor a bit. The distance from the floor to the top of the top tube is an accurate inseam meassurement. Check your inseam using this method. Subtract 28cm from this measurement to determine your proper frame size.

I currently ride with a 110mm stem, which provides a perfect fit. I've used a 120mm stem, but felt that it was a little too stretched out. A 100mm stem would have my knees and elbows almost touching when I pedal in the drops, with my hands near the brake levers. The knee-to-elbow clearance test is a decent way to check for appropriate stem length.

Be sure that you have your KOP set in a reasonable position, not more than 2cm behind the pedal spindle. The vertical distance from the top of the saddle to the top of the bars should not exceed 10cm (4 inches). Check for excessive knee to elbow clearance. If all this checks out and you feel still feel uncomfortable reaching the hoods, you may simply lack flexibility and need to start performing some stretching exercises.
top tube shouldn't be too long....bear
Sep 9, 2001 4:45 PM
thanks,,I guess I have more homework to do.My present bike is a zep,,,conpact frame, is a 54 but when I put a ruler to it is actually a 56, the top tube from the head to the top of the downtube is actually 56.Even with a 90 stem there is so much room from my knees to the bar. I think I may have to go to a LBS and just try out diffent sizes, I feel bad doing this known I am not buying from them though.
I just went through this...CJ3
Sep 10, 2001 8:57 AM
... and just purchased a bike which fits. I'm 6'3/4", with a 30" inseam. At bike stores, the bikes I was put on were measured for standover height, not cockpit length. Consequently I felt cramped on the bikes I tried. I then used the Wrench Science fit program, available from . It provided useful information, and then not only did I spend time with Zak on the phone, but I went to their shop in Berkeley - great place. If you have the bux, I recommend them because they will fit you with a custom bike for about $1500 and up. If you do the Wrench Science fit program, you may get a message saying you got your measurements wrong or have a nonstandard body, which is their way of saying your legs are too long or too short for your torso.
Anyway, I learned I needed about a 56 cm tube height and about a 71 cm cockpit length, including stem. Given general stem length variability of 10 - 13 cms more or less, I could find a top tube lengthe of 58 - 61 cms - the smaller the better. So I started looking for a bike with a slightly longer TT than seat tube. That is what you'll want to tell your LBS.
I found a bike through my LBS, Dublin Cyclery (another great place). They made some calls with the fit info, and found a Univega Modo Vincere which I bought. Go to and download their tech/geometry info. At the bottom of a one page chart is the modo series. My bike came with a 59cm sticker, but the 58 cm on the chart contains the sizing info. I have about an inch of standover clearance on my new bike, and once I started to ride the bike, I have not noticed standover as an issue. The cockpit is long enough for me - I have a 120 stem and a set back seat post (another variable to fit you right). This is a steel frame bike with campagnolo veloce components (aluminum fork which you may want to change out). I got it for a great price. I believe the maker in NJ is going out of business, and some internet bike companies have bought up a lot of stock. Search on univega modo to find out more.
Good luck.