Will it be ok to drill the valve hole bigger in a DT swiss XR 4.2D to take a schrader valve?

I use a round file.

Drilled my 5.1’s 12 months ago with no ill effects.

Drilled my XR rims without issue.

should imagine it would be OK – but why would you want to ?

Also drilled my 420SL’s and no probs.

Half way down Snowdon my mate gets a puncture. And he’s forgotten his inner tubes. And he’s the only one of us with Presta rims. So, we enlarged his orifices with small pieces of slate. Worked quite well.

4 years on drilled out 5.1

Drilled many a rim all are fine including 7 year old WTB speed disc rims 10mm drill bit low speed bit of oil.

Well there’s a lesson, check you inner tubes before riding.

Also I don’t think there will be any ill effects but why bother. Buy Presta tubes instead.

Ok cheers guys