I did my first three triathlons last year and know NOTHING about road/tri bikes. I have a question about bike fit. Let me give some info first, if you will allow me.
I have an old road bike. I put on a forward seat post and clip on aero bars for triathlons. I bought the bike from a buddy to see if I liked triathlon (didn’t see point in buying and expensive bike before knowing if I liked it…by the way, I do like it).
I am 5 feet, 11 inches tall. I have a 30 inch inseam in pants. As you can possibly tell from those figures, I have a long torso and shorter legs.
The toptube is 21.5 inches (54.61 cm) from center of seattube to center of headtube. The top of the toptube is 30 inches (78.74 cm) from the ground. The nose of the seat is directly above the center of the crank.
When I’m down in my aero bars, I just can’t get comfortable. I almost feel like I’m about to fall over the front if I don’t slide my butt back on the seat.
HERE’S QUESTION 1: From these figures, does it sound like my bike is too small for me? I have a feeling it is. I just can’t seem to remain comfortable.
QUESTION 2: When a bike is, for example, size “56” or “57”, what does this figure represent? Is is centimeters? Is it the height of the seattube? the toptube? none of these?
I know these are such basic things, but I have to start somewhere!!!
PLEASE HELP!! I can’t tell you how much I appreciate this forum and the information available. THANKS SO MUCH!!!
OK, let’s start with the road position and work from there. A bike frame size is normally measured in cm’s from the center of bottom braket to center of seat tube where it joins with the top tube. Measure along the seat post, not strait up at a vertical. Your frame size is as a guestimate about multiplying your iseam by .67.
Here’s a very good basic bike fit site. Read this over and follow it. Once you’ve mastered this and have an idea about the road position then repost here and we can talk about your options o setting up for tri. But understand this stuff first.
Well, first off, It is pretty darn impossible to answer all your fit questions over the internet unfortunately. Having said that, my inclination is to say your bike is either right for you or just a very small touch too small, but probably more likely to be right.
The top tube length is largely a function of your torso length. Your top tube is 54.61cm and, with aerobars, that is a pretty longish top tube, something we’d look for on a guy around 5’11" (like you) to maybe a touch around 6"0" tall. Now, again, the normal disclaimers apply: Dimensions vary, it is dependent on your body configuation, what races you are doing, etc, etc. I don’t think you are too far off though. Two reasons you may not be comfortable (again, a guess from a distance) are:
Because you’re using a road bike. Tri geometry may work better for body.
You may not be aclimated to sitting in the aero position yet.
And finally, what do the NAMES of bikes sizes mean? Well, not much. They are immensly cryptic. Every manufacturer seems to measure, design and build differently.
Here’s an example: I used to ride a 55cm Quintana Roo Kilo Private reserve. It fit me very nicely. Now I ride a 49 cm Guru Trilite. It fits me the same. That is a size span of 6 sizes and the bike dimensions are very close, nearly identical in fact.
The names of sizes cannot be used as a guideline to shop for bikes due to their arbitrary nature. Only the actual dimensions are relevant.
Geez, in retrospect, I don;t think I’ve helped you much.