One of my frames has an ETT of 630mm and a reach figure of 395.
I’m looking at something else which has an ETT of 620 and reach is 508.
Now the ETT’s are within 10mm of each other so from my understanding they should feel the same lengthish when seated. But the difference between 395 and 508 for the reach seem quite big.
So will it feel too long for me when standing? If not how will it feel/what difference will I notice?

One of those must have a seriously steep seat angle.

Is that 508mm correct it seems very long

they should feel the same lengthish when seated

well the distance between your bum and the bars may be same/similar*, but to have that difference in reach one must have a very steep seat angle which is going top put your body in a different place relative to the BB which will feel different both seated and standing.

what’s the stack on the two frames? (or in fact all the other measurements as you need to look at the thing as a whole not isolated numbers without relation to the others!)

*depending on where you end up running the saddle and bars.

Play away

http://www.bikecad.ca

Miss read the reach.
It’s 435. Still quite a difference.
2 degrees difference in the seat tube between the two.

435mm reach for a 620mm length TT seems normal
395mm reach for a 630mm TT frame seems short – and I like short reach frames.
Apart from that I’m not much help, I tried a longer reach frame and didn’t like it for what I enjoy riding. 435 is not that long though.

On a medium frame, 2 degrees of seat angle could explain 40mm of top tube.

…and a lot of stack could easily reduce that reach on the short frame.

more numbers required!

Stack is 607 on my frame and 645 on the other frame.
Head angle on mine is 66.5 and 65 on the other.

So new frame is longer and high at the front. You wont be needing spacers to get the front end up thats for sure!

Slightly higher bars should make the bike feel shorter, counteracting the increased reach slightly.

Of course how it feels depends on how many spacers you have now, bars, stem and what you plan to run on the new bike. All affects fit/comfort (in a handling sense)

It’ll be run the same as I have it now.
Flat bar and no spacers.

It won’t be too long. My Geometron runs 508rea h with 640mm ETT and feels spot on for me at 5’10.5″. Both standing and seated.

I still ride my Spaceframe which is 23″ ETT and bloody short reach! BUT front is much higher on Jones making it feel even shorter.

This could be weird except these two bikes are at polar opposites of the intended way of riding and feel. As such I adapt easily even when using them. On the same terrain, I just ride them differently. Both make me smile.

I think I’m saying everyone that’s ridden a Geometron, a bike that smashes convention out the park for size/ETT/reach numbers for an intended rider size, has said it feels fine, like a normal bike with some small adaption required. No one has gone this is far too long, not one person, even on demo day at FOD where many just took the opportunity to have a go with no further intention.

It’s also only 40mm which could be disguised in bar sweep, stem length and saddle position if you were unsure. as mentioned 2 deg seat tube will make the pedalling position different unless you move the saddle. 10mm is comfortably 2deg on or off the effective seat angle if fore and aft. That doesn’t change the reach figure.

A more valid measurement is the BB to HT of both bikes or to manage fit BB to bar end for the same crank length.