Frame sizing confusion!

Boneidle24Seven

Hi,

I've noticed that bike manufacturers like to confuse us with frame sizing. For example, if my usual frame size is a 56cm, Which is the measurement of the effective top tube length. When I'm looking at another make in a 56cm, it's stated that this is the measurement of the seat tube. So really I'd need to be looking at their 54 in order to get the right ETT length. Is that correct?

Thanks in advance! :?

N0bodyOfTheGoat

Stack and reach.

keef66

You are correct. Different manufacturers use different sizing conventions. So as well as differing geometry you have to be aware that a 51 in one bike can be similar to a 54 in another (I have both)

Simplest way is to try a few out, but if you don't have that opportunity, working out the stack and reach is a way of comparing dissimilar frames

drlodge

You need to look at the frame dimensions/geometry and compare that to your ideal size/fit. Ignore what size the manufacturer calls their frame.

My ideal fit is eTT of 545mm with 73.5 STA, and go from there.

Boneidle24Seven

Thanks. My current bike ( Genesis Equilibrium) is a 56 ETT which to be honest, even with an 80mm stem still feels too long.
I sat on a 54 Surly Straggler yesterday, which also felt too long. So now I'm looking at a 52 which has an ETT of 55 which should be ok, but the shop didn't have one in that size to try. But now the stack difference between a 52 Straggler and my Equilbrium is massive. Surly 534mm and Genesis 584mm. That's a lot of headset spacers!!!!

drlodge

Boneidle24Seven wrote:

Thanks. My current bike ( Genesis Equilibrium) is a 56 ETT which to be honest, even with an 80mm stem still feels too long.
I sat on a 54 Surly Straggler yesterday, which also felt too long. So now I'm looking at a 52 which has an ETT of 55 which should be ok, but the shop didn't have one in that size to try. But now the stack difference between a 52 Straggler and my Equilbrium is massive. Surly 534mm and Genesis 584mm. That's a lot of headset spacers!!!!

This is the comprise you'll be facing. To get a shorter eTT, you downsize on the frame, which means shorter head tube and hence greater drop between saddle and bars.

When looking at eTT, you also need to consider seat tube angle. I think (IIRC) 1 degree steeper on seat tube angle means 1cm off the eTT to give the same reach.

mfin

Remember you have to accept that there are loads of frames which will not really have a suitable size for you, then set about understanding why.

Boneidle24Seven

mfin wrote:

Remember you have to accept that there are loads of frames which will not really have a suitable size for you, then set about understanding why.

I don't think there are many frames that fit me. Short legs, long torso (think Orangutan) Not to mention stiff back and increasing old age!

N0bodyOfTheGoat

What is the reach of your current Genesis?
What length stem and angle, + or - position?
What reach are the bars?

Use these to judge what reach your new bike needs to be. I'm also more torso than leg for my 5'10" height, the 58cm Cube fits me pretty well with 388mm reach and 610mm stack.