Eric04

Alright I did a bit of research on finding your frame size using your inseam and multiplying by .67, so for the most part im not truely a turtle on my back. But...I do have some questions.

Ok so, I was given a 58cm 06 trek 1200 (all stock), however im a hair under 5'9 and my inseam runs 82cm from my crotch to the floor. Using the calculation suggested by many, I come up with 54.94. Now I know the frame I have is currently a bit large, however what is the effect on efficiency compared to having say a 54cm frame? Would you guys recommend a 54cm or 55cm frame if I were to switch (with the 54, is smaller better?)

Since this is my first bike im wondering if it is benificial to find a smaller frame and at the same time would it be better to use a frame slightly smaller than the calculated value or use the frame that most closely matches it?

Thanks guys really appreciate the help.

Eric

ptle

I would go with a 54cm. With a smaller frame you can run a longer seatpost or spacers (though you shouldn't use too many!) to account for a cm (which is 4/10 of a inch).

I am 5'8" and run a very similar inseam size as you. My frame size is a 54cm and I wish it could be a tad bit shorter. Maybe a 53cm or a 53.5cm frame.

jonestr

I think the frame measurement you get by taking some fraction of your inseam is a center of the bottom bracket to the center of the intersection of seat tube and top tube (c-c). For some reason most frames are measured from the center of the bottom bracket to the top of the seat tube these days so this measure does not work unless you know the c-c of the frame. If you have a compact frame then you have to construct a virtual top tube that is parallel to the floor to get this to work.

Also, it is best to size frame by top tube and not seat tube FWIW

Eric04

Hmm i think i need to investigate frame dimensions futher to get a better idea.

Steel Man

Don't forget to take into account your reach. Using your inseam only as a base for calculation will only give you an approximation to the length of the seat-tube, which is used by the manufacturers as "size" (I am not sure if ALL manufacturers do it this way, but most of them do).

The other factors are the length of your torso, your flexibility and your overall reach, which will give you the length of the top-tube and the stem.

You need to find a balance between seat-tube and top-tube lengths. For example, if you have a short torso (like I do), in order to have a proper and conformable reach without using an extremely short stem you might have to compromise and use a smaller frame (read seat-tube length) than what the cycling inseam*0.67 formula would call for.

The best advice, get a professional fit.