silly sizing question
 

It's a 2 parter; I have a 30" inseam, and 36" arms. no, really. So in doing some basic calulations, It looks like I should be riding a 50cm frame. Is that right? it seems so little for someone who's 5'10", and it would mean that I've been riding the wrong size frame for a long time. Also, would a frame that size have a proportionally shorter top tube, thus putting me in a more upright position given the length of my arms? Yes, I know that i'm pretty well out of proportion. Thanks!

Sizing over the internet, especially with odd shaped people, is a crap shoot. Yes, a 50 sounds too small and a 55 to 58 would seem more likely, but frame geometry and rider fitness vary greatly so conclusions based on such limited information are highly suspect.

I'm 5'10" and I ride a 56cm frame, but my inseam is 32". Your legs are shorter than mine. On my bike, you would have to drop the seat quite a bit, which would give you a more upright position to the bars. You would however get the longer top tube that you will probably want with your long arms.

I think you need to go to a bike shop and really get fitted as you seem to have a little bit of odd sizing. My guess is you will either want a 56cm frame with the stem set as low as you can get it, or a smaller frame with a long reach stem to move the bars forward.

+1

I'm 5'9" with a 32.5 inseam. I ride a 56 and it fits perfect. With a 30" you should be on a 53 - 55cm frame. 50cm is just way too short. You'll need a 400mm seatpost to make it fit. This a classic case of where you really need to go to the LBS and get fit and buy the bike from them. Good luck

Tim

I'm the opposite of the OP. I'm 5' 10.5" with a 34.6" inseam and short arms for my height. I ride smaller frames (currently a 55) so that the top tube isn't too long. I use a long seatpost to compensate.

How does your current bike fit? Are you comfortable on it? If you've been riding for a long time I'd be careful about making huge changes.

+1 to visiting the LBS.

I'm riding what Giant designates "small" so I can more or less straddle the top tube. I finally had to get a stem/quill setup with the stem 15mm longer than standard. You might work with an idea like that for fine tuning the size.

WOW, long legs for your height. Did you ever consider a custom? Waterford and Merlin both offer a custom fit program. Neither charges extra for the service. I don't know anyone that offers custom carbon fiber.

Tim

I just wanted to say thanks for everybody's input. I just started thinking about it over the weekend; although I'm pretty comfortable, I may be looking for a more upright riding position. I'm probably going to switch out my bars and that should do the trick. It just made me wonder if I would be more comfortable on a smaller frame, as I had never really thought about it before.

Someday.... :)

I'm unclear as to the size of your current bike. Obviously, you need to be able to "stand over" a bike without any pain or injury. My leg length is 34 inches, with a 32 inch slack's inseam. The bikes I enjoy riding the most are in the size 57 to size 61 range. A size 60 or size 61 bike will have a "standover" of around 33 or 33 1'2 inches, so the top bar will press lightly on my jeans when standing with both feet flat on the ground. But, that bike fits perfectly when I'm riding, and not "standing".

Assuming you can "stand over" your current bike without discomfort, try raising the bars so the the highest part of the bars (next to the stem) is almost as high as the top of the saddle. Most guys who are unhappy with how their road bike "feels" have their bars two or three inches lower than the top of the saddle. After the bars are up level with the saddle, they are much more comfortable.

After the bars are level with the saddle, figure out if the "back of saddle to front of stem" measurement is right. If it is "right", your back would be at about a 45 degree angle to a level top bar with your hands on the bars next to the stem. If you are stretched out, and pulled down to about a 30 degree angle, your stem is too long. If your back is higher than 45 degrees, the stem is too short.

By adjusting the seat post, the height of the bars, and the length of the stem, it is possible to get a very good fit on a fairly wide range of bike sizes. I was able to set up a size 54 bike to give me the identical riding position that I have on my size 61 bike. However, I did not like the "look" of an ultra-long seat post and an ultra-high stem, so I sold that bike.