Building up a hardtail frame (Dekerf) with a Middleburn RS7 chainset (3 ring). I’m using the recommended 68 x 113mm b/b for chainline fit but, the granny ring is very very close to the chainstay (c.3mm). If I try an old XT chainset, the granyy ring is further from chainstay (5-6mm) which is more confidence inspiring!

I’d rather use the Middleburn, so what’s an acceptable closeness of granny ring to chainstay?

Or do I need to have a wider axle – and will this put the chainline horribly out?

Cheers

As long as the chainline is ok, any clearance is enough (though keeping things in good condition to avoid chain suck would be wise).

Still, I recall going up a couple of mm of BB when switching from XT to RS7; reason was the front DR couldn’t swing in far enough to get a good downchange to granny.

2mm would be the limit for me. 3mm sounds fine. Either way, just go for a short spin and see if it leaves any marks.

Te clearance is probably enough, you may struggle with the mech though