newbcyclist

I'm coming from mountain biking, so this whole new realm of road riding is very new and exciting. However, one thing that isn't so great is the extreme importance of frame fit, as I seem to be caught between two sizes of most manufacturers. I was hoping to get some advice on which way to go. So I've been to bike shops and have tried riding a bunch of brands. Most of them start out putting me on a 54 cm due to my height (5'8.5"), but these frames feel too "stretched out" to me. At the moment I'm chalking this up to inexperience with road biking, as mountain bikes are more upright, but I think I really do like a slightly more compact riding position. My inseam is 31". Also, I did the wrench science fit calculator, and it spit out these recommendations:
Frame (C-C): 51 cm, Frame (C-T): 53 cm, Overall reach: 64.96 cm, Saddle height: 69.53 cm, Handlebar width: 46 cm. When stuck between two frames, is it generally better to go up or down, or is it merely a matter of personal preference?

I'm very confused as to which way to go, compounded by the fact that frames between manufacturers vary so much. Thanks for the advice! I'm looking forward to getting my first bike and hitting the asphalt (with only my tires that is; hopefully not any other body part).

JiveTurkey

Your fit analysis recommends one frame size: 51 cm, measured center of bottom bracket to center of seat/top tube intersection (c-c) & 53 cm, center of bottom bracket to top of seat tube (c-t).

While the seat tube is typically how bikes are sized, it's really the top tube and overall reach that matter more because no matter how long the seat tube is (within reason), you can adjust the seat post to achieve the correct seat height. You dial in the reach of a bike by getting the stem length correct (also, stem height--in relation to the seat height--has a bearing on comfort). Most road bike stems I see are in the 100 to 120 mm range, so you can find a frame that when used in conjunction with an average stem gives you the proper reach.

To answer your question more directly, road frames are sized so close to each other (like 2 cm) that if you're really in between frame sizes, you can usually go with the smaller one and then set your handlebars in the correct position with the appropriate stem. Again, shoot for 100 to 120 mm, any more or less and you might want a different sized frame.

You're right, bike fit (not just the frame but also the stem, handlebars, crank, etc.) is very important for comfort. A general rule I use is the 45/90 method: with your handlebars an inch or two below the saddle (whatever you find comfortable) and your hands on the brake lever hoods, elbows slightly bent, back straight and your butt on the seat--your back should be about 45-degrees from horizontal and your arms should come away from your torso at about 90-degrees. For a more performance fit, achieve the same angles, but with your hands on the bar tops instead (that way, when you're in the hoods, you stretch out further).

Good luck and welcome to the road. I started off as a mountain biker, too. I'm 5'8" and ride a 54 cm fame with 55 cm top tube and 120 mm stem.

marqueemoon

46cm bars on a frame that small seems a bit odd.

stapfam

I went from Mountain bikes to road 18 months ago. I got a compact Giant and tried two frame sizes in Giant. Went for the smaller. Within 6 months- I had to put a longer stem on and it still did not feel right. Next bike and a frame size higher and it fits. Although I would say it is mountain biking that is causing the problem at present- you have to have something that is comfortable.

Attachment of the two bikes and they are both comfortable. Think of the future and they way you may adjust. And bar height will drop as you adjust to the different style of riding.

And while on it- Think of gearing. I live in a hilly area so on the OCR went for a triple. Can assure you that if you are a Mountain Biker- You can take a compact double easily. Went 50/34 and a 12/27 rear cassette and road hills I used to rideon the MTB in 22/32 can easily be done on the compact gearing. Don't think I could manage the higher Double crankset though.

PhilThee

I was wondering the same thing but was afraid to ask.
If you measured from the outside of the arms after the shoulder joint you have measured in the wrong spot.

The measuring spot is between the shoulder joints.
Handlebar width should be the same as the distance between the shoulder joints.

A wider bar opens the chest for better breathing and more leverage, but is less aerodynamic. You'll need to find your own balance between the two.

If it is really 46cm then you have some very wide shoulders for a guy your size.

PhilThee

Fill out the fitment forms at https://www.competitivecyclist.com/za...LCULATOR_INTRO

Take all of your measurements again exactly like they say, carefully.
Push that old book up there good. We won't tell

The Eddy and French fit should be close.

stapfam

A recent bike sizing formula was posted on 50+ and seems to work. If you are thinking of a compact frame then you have to transpose the sizing to a normal frame- but the formula does give an indication of the sizing to start from. The basic rule still applies though and sit on the bike and see if it fots.


https://www.bikeforums.net/fifty-plus-50/374358-bike-fit-math-revisited.html

urbanknight

Have someone else take the measurements. I know I was off when I did it, because its calculations for me when I tried to measure myself would never work.

PhilThee

This is the direct link to that article.
https://www.trinewbies.com/Article.asp?ArticleID=183

inseam x.67= frame size is nothing new.

PhilThee

Have a female friend do it.If not things are going to get.... Ummm,.. awkward

Al1943

You may want to put some thought into frame proportions instead of just height. The top tube length (effective TT for compact frames) varies from brand to brand, and sometimes from size to size within a brand. As an example, Colnago and Specialized road bikes in your size have relatively shorter top tubes than Trek or Lemond.
Also the difference between c-c and c-t is more like 3 or 4 cm on big tube CF bikes.

Al