Shim a 35mm stem to 31.8mm?

Dodgy or not? I see shims are available on ebay, but not sure if they will work acceptably.

To reduce the handlebar clamp size you can use in 35mm stem? Given stems and bars are daily checks I’d either get a new bar or stem.

Planet X do a 35mm clamp /
780mm width bar for cheap usually. El Guapo Saloon bar. Often discounted to £15 and it’s pretty light and if you get it in black with Matt black decals it’s subtle too.

I wouldn’t, not on a stem. No reason to back that up, I just wouldn’t do it

I’ve been riding fleegles with shims for a couple of years with no issues.

I’ve been riding 25.4mm Jones Loops in a 31.8mm stem – with a Jones-supplied shim for around 8 years.

It’s been done for decades with no issues. So if you just have to have that bar / stem combo then I can’t see a problem. Having said that, this is a high stress area that relies on tight tolerances so this is one area that I wouldn’t want some random cheap Ebay purchase to be fitted. Problem Solvers make the needed shim (although seemingly not available where I live as I was looking for the same thing the other day…)

Would depend on the riding for me. A daunder with a bike – fine, ragging it around a trail – no.

I have been using them on my trail bike (with carbon bars). A bit of a faff to get all lined up but no evidence of them creeping out etc. They fit both the bars and stem spot on.

Also I imagine the tolerances for bar diameter are quite loose as that part of the bars is not machined.

To be safe I have gone all in & ordered a 35mm dia 38mm rise burgtec bar.
It was really a test I wanted to try. My 20mm carbon riser bars feel too low & I had some 30mm risers to try, but of course they didnt fit the 35mm stem.
Hopefully this will resolve my issue.

Would depend on the riding for me. A daunder with a bike – fine, ragging it around a trail – no.

Sounds like the OP’s found some 35mm bars now anyway but fatty gets hammered and whilst not an enduro/downhill bike it is rigid so probably gets similar if not higher loads.

I did think about it for a while, and concluded that as there isn’t a consistent design of stem clamp that it really shouldn’t make a difference how the bar is eventually clamped. I was more worried about the stem as it’s never normally clamping onto nothing in the center as the shim is made up of 4x parts which have a lip on the outer edge to locate them at the outer edges on the stem.