Please measure your Ape Index!

[horizon]

As you might know, I've been looking from time to time at the problem of horizontal bike fit - i.e. how long the top tube should be in relation to the "size" of the bike. I find most top tubes too long. This could be because I prefer the saddle to be further back (longer thighs/pelvis?) or because I have shorter arms. But I seem to have found a quick and simple way to measure arm length (see below) even though not yet pelvic length (backpackers have a way of measuring torso length so I might look at that as well).

So what I want to do now is to compare my arm length against that of other cyclists. If you go to:

http://www.swimsmooth.com/ape-index-swimming.html

you will see the very simple instruction. If you could also say how tall you are (in feet and inches) and how long your top tube is (in cm) then even better (assuming you use drops). I'm glad it isn't April.

Good luck and thank you for participating!

[meic]

What makes you think our bikes are right?

In my case the top tubes are just what the bike came with. Two of my bikes were chosen (by others) just as being vaguely "big" as I am tall.

[pedalsheep]

OK, I'll go ape!
I've an ape index of plus 1, I'm 5' 4" with a 20" (centre to centre) top tube on a custom Roberts.
Do you really want to know this?

[samsbike]

Out of curiosity wont flexibility or not have an impact?

Also I wonder if those with longer arms also have their saddles back more.

[irc]

Height - 6ft 2 1/2 inches.
Ape Index + 1/2"
Top tube 60cm. -

I have a seatpost with no layback and my saddle central on the rails. Presumably I could ride a frame with a steeper seat tube and hence shorter top tube but with the saddle further back on the rails?

[horizon]

What makes you think our bikes are right?

.

I don't. I reckon that one third are right, one third are wrong (uncomfortable and therefore maybe not cycle anymore) and one third switch to straight bars ASAP.

[horizon]

OK, I'll go ape!
I've an ape index of plus 1, I'm 5' 4" with a 20" (centre to centre) top tube on a custom Roberts.
Do you really want to know this?

Thanks pedalshep. And yes, I really do want to know this. I want to know why I don't find bikes comfortable.

[horizon]

Out of curiosity wont flexibility or not have an impact?


Yes, plus all the other proportions. So it will be interesting to see if arm length stands out.

Also I wonder if those with longer arms also have their saddles back more.

Yes, but those with shorter arms and saddles back will struggle to reach the bars. The position of the saddle is related to the BB not the bars.

[horizon]

Height - 6ft 2 1/2 inches.
Ape Index + 1/2"
Top tube 60cm. -

I have a seatpost with no layback and my saddle central on the rails. Presumably I could ride a frame with a steeper seat tube and hence shorter top tube but with the saddle further back on the rails?

Thanks irc.

And yes, every time the top tube changes length behind the BB (i.e. the seat angle changes), the saddle is moved to compensate. So top tube length is no indicator of ... top tube length.

[tatanab]

Why is top tube length important? irc (above) has a top tube of 60cm but is the stem 130mm or is it 60mm?

[Brucey]

as well as seat angle/saddle position variations, you can have different stem lengths and handlebar shapes too....

FWIW my bikes mostly have top tubes in the 22" to 23" range. I am ~5' 8" and I have an 'ape index' of +4" .

But I also have broad shoulders , which count ape-wise but matter naught in bike frame size and handlebar reach...

Still, I'm probably a bit further to the left in this picture than I'd like.....



cheers

[horizon]

Why is top tube length important? irc (above) has a top tube of 60cm but is the stem 130mm or is it 60mm?

The top tube length is now considered to be the most important sizing measurement on a bike provided there is enough steerer length left for bar height. The top tube length behind the BB is constrained (hence all the posts about layback seat posts and saddle rail length) but OK if you change the seatpost. The same is true for the top tube length in front of the BB but my experience is that most top tubes are too long and require a very short stem if you want to use drops (hence all the posts about converting to straight bars). However, as I said, that is my experience and riders with different (or even average) body proportions may find the top tube length about right and easily within the adjustment range of the stem length.

[horizon]

you can have different stem lengths and handlebar shapes too....

Unless you want conventional drop bars ...

FWIW my bikes mostly have top tubes in the 22" to 23" range. I am ~5' 8" and I have an 'ape index' of +4" .

I'm 5' 10" with an Ape of -.5". Imagine trying to get a bike to fit those two different proportions using the same top tube length!

[Brucey]

I'm not sure that the ape index is a good guide to how your bike should be designed; however it does show that people do vary in their proportions.

As a general point it is quite unusual for the contact points of a sporting or racing cyclist to move more than about 2" away from where they would be expected to be simply on the basis of someone's height. I think this explains nicely why stems can vary by about this amount and are adjustable up and down by about this amount too, and most people get a reasonable fit. However saddles don't move on the rails as much as this, plus some folk are fussy about what length stem they have. Thus there is a need for different seat angles and top tube lengths to get a really good fit.

However for touring purposes there isn't such a strong aerodynamic constraint; hence preferred riding positions can vary enormously. Add in body shape variations and suddenly you may want the contact points moved about 5" or more vs where you might expect on the basis of height. As you point out, you can't really expect to accomodate everyone using a single kind of frame design; less so even than is the case for racing cyclists.

cheers

[horizon]

One way round the reach problem is to switch to straight bars (see numerous posts on this topic) as drop bars by their nature are notorious for extending your reach - by about 12 cm. But I find drops the best bars by a long way. Thorn, to their credit, offer two lengths of top tube for each size of bike to accommodate either straight bars or drops. What I find is that the equivalent size of bike in other ranges with drop bars (e.g. Dawes Galaxy) offers a top tube length equivalent to the Thorn top tube length for straight bars. They cannot both be right, even allowing for a palava in the bike shop to switch stems.