I'm considering buying a 2012 Devinci Silverstone SL 2 second hand. Size is Small, 52cm.

I used several calculators online to estimate what size frames would be suitable for me and came up with several numbers.

This frame falls within the more aggressive fit which I think I'm okay with. But would still like to run by the forum here for approval.

However, what I don't understand is the numbers this calculator gives me regarding saddle setback. Most saddles allow for 10mm offset from center in either direction.



The calculator suggested a seat post with zero offset (!) and a 50-56mm setback. I know calculators are always wrong, and I will be making the minor adjustments myself, but I'm using this as a guide and I just don't understand what it means.

How could I get a 50mm setback with a zero offset seatpost?

The bike has a 25mm setback seatpost, by the way. And the stem is 120mm - 15mm longer than suggested by that calculator, (but on this type of fit, wouldn't an extra long stem such as 120mm be suitable? So the calculator is wrong in that sense, almost definitely, as per my understanding of how pros fit their bikes. Not that I'm a pro, but if I go for this bike/fit, it will be following those trends.)

Thank you very much.

If calculators are always wrong, why use one? Actually, it is you who is wrong. "Most saddles give you much more than 10mm adjustment in either direction. Zero offset seatposts are becoming very available and I've seen Nashbar blowing out some very nice FSA zero offset posts for less than a third of their list price. If you have an "aggressive" fit in mind I would seriously look into one. If you will study your own chart that you attached you will see that it is very easy to get 50mm of "setback" with a zero offset seatpost because the frame already has a significant amount of setback built in. Setback, as they define it is the distance between the saddle nose and the bottom bracket. On a plumb line, of course. You're on your own with the stem. They are cheap as well. Almost cheap enough to buy several, in 5mm increments and simply slap on the one you feel like that particular training day. "Arggg, I feel like getting stretched today, where's that 130mm Salsa..."

H

As you pointed out, the setback in in fact the horizontal distance from the center of the BB to the tip of the saddle. I actually had realized that before and forgotten about it by the time I came back looking at this issue. Problem solved.

what is the seat tube angle ? often smaller is steeper ,to reduce the reach without excessive toe clip overlap.

or BB plumb line to axis of the seat tube , since seat-posts set back is just buying a different post and using a different saddle rail design .