A Question on Reach

[Ride-Fly]

Hi all,
I normally ride a 55cm ETT with the standard 73 ST angle and a 100mm stem. I have 100 stems on all my bikes but been considering changing all to a 110 stem. On my Colnagos, I ride a size 55 which has 54.3cm ETT but with a steeper 74 STA which extends the reach. I don't have a trig calculator so I can't figure out the cosine in relation to my seat length but I'd think it would add a few mm to the reach. I recently bought a Tommasini Tecno frameset which I was told had a 56 ETT with a 73 STA. I got it home and it is 56.5 ETT. I would stay with a 100 stem on this one so would I be able to make it work with this frame? I got a smoking deal and want to make it work. Thanks.

[GrantM]

Assuming you want the same saddle position set back on all the frames,
a change in seat tube angle of 1 degree = approx 1 cm of seat tube set back difference.

here's the exact chart:

[Ride-Fly]

Assuming you want the same saddle position set back on all the frames,
a change in seat tube angle of 1 degree = approx 1 cm of seat tube set back difference.

here's the exact chart:

Thanks for the chart Grant. The seat to BB height doesn't affect the setback but does affect the additional reach difference. I have a custom fit chart and it said that I needed 660 reach, so should I worry about the setback? In your opinion, do you think I could make the 56.5 cm ETT work if I use a 100mm stem considering my 54.3 Nags work well for me? The only other consideration is the standover and amount of seatpost that shows. On my level TT 55 Nags, I have very little seatpost showing- maybe 5 inches from collar to bottom of the head cluster.