Speak to Triton bikes – they use Russian grade OT4 which is stiffer than 3/2.5 that is often used.
..not in any way that will make a jot of difference to the ride feel of a frame. 6/4 gets the stiffer + lighter sales pitch too, but the stiffness difference really is minimal and it’s not lighter per se.
Anyway. MTG, my 2p – with your reputation… : ) I’d be buying a custom steel frame from a good builder; better good steel than cheap Ti. Especially if you want a belt drive.
I’ve seen a UK-made Ti frame that was so bad you’d be happy to buy Chinese.. Yet one of the Chinese builders mentioned here is a little way off what I’d call reputable, so ‘buyer beware’. Good ti frames are not cheap, there’s no way round that. Buy a cheap one from China and put aside the extra you would’ve spent to replace it if it cracks, as the warranty back-up isn’t going to be easy logistically, even if they do consider it.
Triton’s stuff looks good value and there’s a long, satisfied customer thread on MTBR. Since the flaws in ti frames aren’t something you can see, so you have to go on reputation and that’s where the price usually goes up.
Personally, I’d call a UK builder about an 853 TIG welded frame. Will only be 3/4lb heavier than a suitable ti frame, maybe less if the ti is beefed up for belt drive and a strong high-mileage rider.