Just managed to get hold of a new hybrid pro for £675…I want to change the stem but it doesn’t say steerer size, the bars are 31.8mm, I wanted to put a Thomson one on there, can I assume it will be a 1 1/8 steerer?
I pick the bike up Sunday so I could wait and ask them but I didn’t know if anyone on here would know
Cheers…

I would probably assume that it is 1 1/8th yes. Are you that desperate to get a new stem on for what will probably be just one ride?

Why one ride jekkyl?

because you can get it, ride it that day, measure it then order that stem which will arrive in 2 or 3 days. Unless you plan to ride every single day until the new stem arrives we can assume that it is very likely you will do one ride with the existing stem.

I agree with Jekyl, ride it first and make sure you know what length, rise etc you need.