we're navigating that now. center of rails? center of flanges? a particular flange width? a given distance shorter than 27cm? (i.e., a 24cm saddle uses our standard formulae + a fudge factor.) no good answer for you yet. working on it.

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Dan Empfield
aka Slowman

When I'm transferring or setting up that involve the saddle as a datum I use the 120mm point forward from the back of the saddle.

when you take an old turbo saddle or a new power/or stealth seat, the wide is at 120mm not the same so you will sit on a smaller or wider part of the saddle. that will be uncomfortable.

i printed a plastic gauge that is 80mm wide on the internal, that i put over the seat and measure from there.
so everything is measured, hight reach and setback from that point.

70mm and 90 mm didnt work on all seats so i came on 80mm .
it is close but not even perfect, you will have to make small adjustments

Good input Leon1, I was recommended by a reputable bike fitter to use the 120mm point as a reference and I have used it ever since. I’ve not actually tested it to see if the it corresponds to the sit bone position on various different types of saddles. He did say that this dimension is good for the longer saddles as well as the more recent shorter saddles. Incidentally I have heard of people using the 80mm point as you describe.

I modified a cheap plastic caliper to be 80mm wide as through testing almost all saddles widest part is 55mm aft of the 80mm wide part of the seat.

I use this as my reference point for saddle height, setback reach and drop. As it removes most of the possibilities due to saddle angle creating different measurements.

Thanks for the reply, the 80mm dimension certainly sounds like a good repeatable datum point to measure from, what we need now is the percentage of saddle height to the 80mm datum point which should give us a repeatable dimension for all saddle lengths. This is what I think Dan is trying to establish…..