I’m starting on my first frame with thru-axle dropouts (142x12mm rear and 100x12 front).
It will have IS disc mounts and if I remember correct there’s some offset in the axis of the wheel-axle. Is that correct? and how much? front and rear difference?
If you have any advice on things that could be a challenge specifically with thruaxle compared to qr I’d be glad to hear them to minimize the risk of failure 
Best, Tore
The main challenge with thru axles is that there is no way of correcting any misalignment after welding, so extra care should be taken to make sure the cs/bb mitre is absolutely perfect and most importantly symmetric. A larger gap on one side will result in more shrinkage during welding and consequently in one chainstay being shorter than the other with no real possibility of correcting it. Also, a relatively minimal difference in length will be very visible in the way the rear wheel is centered between the chainstays.
My recommendation for the order of operations would be to mitre and weld the dropouts to the chainstays and do all the modifications (dimples, flatmount/IS brake mounts) BEFORE cutting the BB mitre because all these modifications will have an effect on the fitment of a mitre if it has been cut before.
Farr has the best write up I’ve found about how much offset you need for each axle standard.
While it’s written for his Le Disco tool, you can pretend it’s write about your tool.
Since I am still learning and not a great welder I bought the Sputnik H-Tools so if I need I can tweak the drop outs.
Do you know if there is a similar drawing for the post mount standard? I’ve looked around everywhere but haven’t been able to find anything concrete. I imagine that the hole centerline is in plane with the dropout face but don’t want to make that assumption
Awesome, thank you. Not sure how I missed this haha
All brake information can be found in the SRAM frame fit specifications, direct from the manufacturer:
See page 138ish:
It’s not fun, but reading and understanding the correct documentation will level up your bike-building skills. Relying on fixture makers and what google algorithm feeds you can compound errors.
Hey! Thanks for all the tips and resources 
Frame is finished and currently building the fork and I’m a little in doubt about the positioning of the iso disc mount.
I’ve aligned my disc tool the drop out inside (which is 2mm from the “real” inside) and spaced the mount 6mm from the tool.
Is this right?
According to Shimano, it’s 4mm from the dropout face. It is hard to tell from the photo what is going on, but it seems lite your tab is only 1-2mm from the dropout face?
Can someone else confirm?
The inside of the disc tab is 4mm from the dropout face. I’ve tried to draw the measurements on the photo. Hope it makes it easier to understand whats going on. If not I can take some better photos tomorrow
loos good to me! Maybe a fork expert can chime in
Updating this with link to 2023 road frame fit specs.
Data for post mount and flat mount brakes are there.
