Does anyone have any useful information on the torsional stiffness of stems? I’ve been riding for the last few years on a Thomson 70mm X4 stem and I always thought it was pretty decent (compared to cheap/OEM stems, it definitely is). However I recently borrowed an Easton Haven 50mm stem to try and it’s remarkable how much stiffer it is. I’m sure part of that is the decreased length, of course.

Anyway, if I was in the market for a new stem in the 50-60mm range, are there any recommendations for stems with an optimal stiffness:weight ratio? How would I go about finding out?

I have the X4 50mm with the Thomson 780 DH bars on my trail bike, not sure how stiff it is in comparison but I can’t find any flex in there, probably a lot to do with there being nowhere in the stem for it to flex 🙂

Pepsi taste challenge time! I can’t tell any diffence between any of mine, cheapo Pro, made-of-fresh-air KMC and forth bridge answer dh and eh, whatever it is that’s on the other bike.

I am tempted to do some science though. But not right now!

Torsional stiffness due to stem length or reduced bar twist due to the bar clamping interface being better?

To be honest I’m not convinced I can tell much difference when riding, but when I torque the bars sideways, I can see (and feel) a bit of rotation relative to the axis of the fork steerer. I suspect that there is more to be gained from running a stiffer stem than in, say, the difference between 1.1/8th and a 1.5″ or tapered steerer.

The four stems I’ve attempted to compare (all very non-objectively):
1. Lapierre own-brand that came on a Zesty 514, 80mm – obvious, visible flex with relatively minor force on the end of the bar
2. Spesh own-brand 80mm with angle adjust sleeve, I believe from a recent Stumpy FSR – better than the lapierre one
3. Thomson Elite x4 80mm. If I try my hardest, I think I can see some deflection in the stem. I can feel it a bit, but that might equally be the bars*
4. Easton Haven 50mm – No visible twisting at all, feels solid.

*Easton Havoc carbon bars. Not thought to be especially flexy!

Torsional stiffness due to stem length or reduced bar twist due to the bar clamping interface being better?

I mean torsional rotation perpendicular to the long axis of the stem. Not the bar twisting (gripshift style) in the clamp. Although I’m sure that the clamp has an effect on both factors.

hmm looks like stem length is the factor not the manufacturer.

hmm looks like stem length is the factor not the manufacturer.

I’m sure that’s definitely the case, but I can see significant differences between three different 80mm stems. I.e. not all stems are created equal and whilst the Thomson is a lovely bit of kit, if it’s not functionally as good as another option I might change it.

on the 80’s you say (1) is very flexy, and the thomson can only be flexed if you try very very hard? Dropping to 50mm removes most of the material that can flex from the stem.

Sounds like the Thomson is a good bet at 80mm, try an 80mm Easton before deciding if it’s good or not.

Superficial, I doubt that. 1 1/8th is flexy as hell on 160mm+ single crown forks and 1.5 actually increases a stems stiffness due to the larger diameter clamping area. That’s also the engineering reason for giants overdrive standard.

Also I notice bar flex before stem flex tbh

I can remember when magazines used to actually test stuff like this. Bars, stems, forks. It’s not the be all and end all of a review but I found it interesting. I think reviewing of kit has become lazy over the years.

just get a haven 55mm.

Have one and it’s lovely to look at, definitely stiffer than my 70mm thomson (obviously there is the length issue but the clamping area feels better too).

Lighter than a thomson too.