I have an existing TT bike that I was fit on, and just got a new TT bike and would like. I will be getting a fit on this one too, but wanted to get it generally correct so that it's (hopefully)fine tuning. Can anyone point me towards an article that could get me oriented?

If no article exists, would I be far off measuring BB to saddle (height and setback) and then triangulating elbow pads from tip of saddle and BB?

*In case it's relevant it was a Scott plasma 3 and the new bike is a Scott plasma 5.

Thank you!
quite a bit of Reach change over the years, from Plas3 to Plas5 frame

oddly, I'm only finding the Reach on the Plas3 circa 2013: Small was 390, Med was 415 and Large was 430
In the meantime, Scott added a fourth size, so now the Reach for Plas5 are:
S = 380
M = 397
L = 415
XL = 430

From 2014 onwards the Stack did not change, but the Plas5 the stack is 1cm taller in the middle sizes

Depending on how long ago your original fit was done, it may not be worthwhile to just transfer numbers. But yes, if you set your saddle x/y first you can then measure out to the armpads.

Don't forget the Plasma5 Pad Solver

Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com
I find stack and reach to be great not only for looking at frame sizing and selection but super useful for duplicating bike setups. Lots of stack and reach stuff here on slow twitch.

I like doing all measurement in strictly vertical and horizontal planes (sometimes taking the liberty of measuring saddle height from bb center to center of saddle).

Then it's just math to see how (or if) a different frame setup will work. I usually start with the horizontal and vertical like I said but then some simple string measurements from touch points as a double check is nice.
I think that you're on the right track. I did this with an athlete yesterday. He'd agonized over the frame choice, but had some help with Trent Nix from Tri Shop in the final selection. I see no reason you can't get a bike one day, move the measurements carefully and race it the next.

But, if you already have the framesets, then it is measure twice or thrice, and cut once. I would wait to do the cabling to be sure. If you haven't done it before, then I'd try to do it all on the same day with the bike on the same trainer, etc. That way all of the measurements are relative to one another.

If you have a different crank length, then it gets a bit trickier with the saddle height and drop, etc.

Brandon Marsh - Website | @BrandonMarshTX | Cervelo | RokaWetsuits | 1stEndurance | ATC Bikeshop |