How to find your theoretical size?

Hi all,

I must confess I'm not really sure how decide frame size. I've read several articles and threads about it, but most deal with road/XC bikes and I doubt that applies straight to "harder" disciplines of the sport.

You can't just get a new bike of the same size of your last rig - it gives you a rough idea, but not every brand measures bikes the same way and there can be substantial differences. But you can compare the geos, if you have enough knowledge/experience to do so (I don't). Of course, giving the bike a short ride is the ultimate test, but not always doable.
So, are there any rules of thumb I could use to decide if a certain frame is "theorically" right for me based on my own measurements (~5'10" high, ~30" inseam?

I'm tired of giving up nice frames for the fear of erring the size and having to poorly resell it days later - the last one, a great deal on a small banshee morphine; same TT length as my old bike (which was a tight fit), but slightly shorter wheelbase and ST... too small for DH, and overkill for street/dirt?

Have fun!

rpet said:

5'10" = medium most likely.

Beyond that, it's personal preference plus actually riding the frames in question.

Click to expand...

I know I should use an M size, but since each manufacturer has its own point of view regarding sizing, unless you look at the geo and/or ride the frame, that is nothing but a rough orientation (for example, the Nicolai 2xmtb in M has very similar numbers to the morphine in S).

I have a very detailed excel spreadsheet that computes your ideal bike geo according to your height, inseam, foot size, etc. but sadly it's aimed at road bikes - if I trusted it to pick a DH bike, it would probably feel like riding a horse.