# 25.4mm vs. 31.8mm stem clamp



## nrsnow (Feb 23, 2009)

Why would someone choose a stem with a 31.8mm clamp over a stem with a 25.4mm clamp?


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## brent878 (Apr 17, 2007)

One reason would be bar selection. 25.4mm is on its way out and much easier to find 31.8mm bars. Its probably suppose to be stronger or lighter but I didn't notice much of a difference switching. But I could only find the bars I wanted in 31.8mm so it made the choice easy for me.


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## MRMOLE (May 31, 2011)

The only place I can think the 25.4 mm stem/bar would be an advantage is on a rigid bike where the additional flex will make your wrists much happier.


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## Rallyator (Nov 11, 2008)

Marketing. As simple as that. Go Extralite home page, then click MTB Components-UltraBar UL-Why 25.4mm standard beats 31.8mm?.


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## sandcritter (Jun 2, 2009)

As was said, changing industry standard. Unconvinced it makes any difference performance wise, they're not any lighter, so.... But I just resent having to buy a stem now with a front end / face plate the size of an infant's head out in front of me.

Building a retro xc bike for fun, and pretty much the only matching seatpost/stem in a lightweight 25.4 is syntace, but the F99 has odd length offerings. So it'll be 31.8 I guess.


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## doccoraje (Jan 12, 2004)

sandcritter said:


> Building a retro xc bike for fun, and pretty much the only matching seatpost/stem in a lightweight 25.4 is syntace, but the F99 has odd length offerings. So it'll be 31.8 I guess.


Extralite also offers a 25.4 stem-handlebar and lighter I believe.


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## Yogii (Jun 5, 2008)

On a rigid bike 25.4 does offer a little(little) extra cush. 31.8 is hype. Other than a track bike, 25.4 is more than strong enough.


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## Ultra Magnus (Jan 13, 2004)

You can't make blanket statements like 31.8 IS stiffer than 25.4. That's bulls*t. Theoretically 31.8 is stiffer than 2.54, but there are some good 25.4 bar/stem combos that are stiffer than some sh*tty 31.8 setups. 

We had a bike in at work one day whe 31.8 was a new thing that had an easton EA70 bar/stem combo. My bike had (and still does have) an Easton EC70 bar and an FSA XC115 stem in 25.4. My buddy at work could grab the 31.8 setup and flex the bars up and down way more they he could my 25.4 setup (torsional deflection in the stem or 2bolt clamp vs. four bolt clamp, I dunno). I'm sure a Thompson stem would have been even more stiff...

My $0.02

BM


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## Zen Cyclery (Mar 10, 2009)

On paper, the larger diameter 31.8mm bar is stiffer under deflection. This can be quite handy on full suspension bikes or hardtails with bigger forks. If your riding fully rigid though, a 25.4 may provide a bit of extra flex to help ease up the ride quality a bit.


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