Frame sizing

[Paul J]

I've been measured up for a bike. I have an in seam of 85cm (34in) with shoes off. I have been told that I should add another 2.0cm (~1in) to this for the shoes and multiplying by 0.67 gives a frame size of 58cm (23in).

I've tried the bike out overnight and this morning and it feels a bit large. I measured the seat tube c-c and sure enough it's 58cm. However the other way c-t it is about 60cm. Should this frame be 58 or 60? Should I be adding 2cm to my height for the shoes? Does this sound right? What is the truth?

Oh and the frame has a standard geometry (non compact).

 

[boudreaux]

Originally posted by Paul J
I've been measured up for a bike. I have an in seam of 85cm (34in) with shoes off. I have been told that I should add another 2.0cm (~1in) to this for the shoes and multiplying by 0.67 gives a frame size of 58cm (23in).

I've tried the bike out overnight and this morning and it feels a bit large. I measured the seat tube c-c and sure enough it's 58cm. However the other way c-t it is about 60cm. Should this frame be 58 or 60? Should I be adding 2cm to my height for the shoes? Does this sound right? What is the truth?

Oh and the frame has a standard geometry (non compact).

Frames are measured,c-c, c-t and c to top of an extended seattube. You cannot go by just inseam.It's only a place to start, assuming adequate standover,worry more about TT length and reach to the bars. Some people do better on either somewhat larger or smaller frames than the guidelines might indicate. If it feels too big,try the next smaller size. don't get hung up on numbers.

 

[Rudy]

true...top tube length is most important...only occasion when the seat tube matters is if you can't stand over it.

go to www.competitivecyclist.com and check out their size checklist. It should dial you in pretty close.

 

[Aztec]

I go with 79cm from center of crank to top of saddle (sighting along seat tube), when I use Sidi shoes and Look pedals (which does add about 2cm of stack height). I ride a 56cm, ctc, and could go with 57 or even 58 in some cases, depending on that top tube. Fitting isn't terribly hard, but it can be subtle and is important! Look for pro help if you don't mind spending some $.

 

[pudster]

You should always start out with your inseam times your .883 to determine your saddle height then find your saddle position on the cranks. Knee over pedal spindle is forgotten a lot when sizing for the top tube. Then you want to see what your stem length is to see how long it is to fit you to the top tube. This is a general way to help you fiqure things out about a frame for you. If the seat tube is steep then the top tube length may need to be longer or visa versa. Do not use the specs that are given on the bike they, are a lot of times wrong. So have the shop measure you up on the bike , if they won't do that for you go to another shop. I hope this helps you out.

 

[Paul J]

Thanks comrades,

I've taken the bike for a couple more spins and it certainly feels sweet. I've lowered the saddle a few centimetres and it's a lot more comfortable now. The reach seems pretty spot on. I guess a big part of my problem is I've been on a large compact design for quite a while and I'm used to having a mile or two of seat post showing and not being used having such a close relationship with the top tube. It is certainly nowhere near as twitchy and harsh a ride as my last bike.

Thanks again all.

 

[boudreaux]

Originally posted by pudster
Do not use the specs that are given on the bike they, are a lot of times wrong.

That is sure alot of hooey.