# Why 31.8mm vs. 25.4mm Handlebars



## tbear1 (Sep 6, 2010)

I have a 26er with 25.4mm handlebars and a 29er with 31.8mm handle bars. When I search online, it looks like most of the manufacturers have more 31.8mm versions. Other than more selection, is there a reason to switch to the larger diameter bar? Thanks,

Glenn


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## LMN (Sep 8, 2007)

In theory 31.8 is stronger and stiffer. Personally I can't tell a difference but maybe a big guy can.

However I do like the look of the larger bar.


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## Glide the Clyde (Nov 12, 2009)

LMN said:


> In theory 31.8 is stronger and stiffer. Personally I can't tell a difference but maybe a big guy can.


Stronger, stiffer, less flex in the bars and stem. Quite necessary on the now more popular 28"+ bars.


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## jeffw-13 (Apr 30, 2008)

More clamping area :thumbsup:


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## breakingbryan (May 29, 2008)

There's a strong correlation between handlebar thickness and badassness.


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## CroMoHo (Oct 20, 2009)

Same reason some trucks have big, huge tires and others have the right sized tires.


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## jimbowho (Dec 16, 2009)

My new bike came with 31's I wanted to run Fleegle bars, and they only come in 25's! So I changed the stem. They flex more, but I like it. I'm on rigid so it seems like a good idea.

I broke one bar long ago. It was a steel bar that came on a rockhopper. No big air for me so I'm good!!

On my race bike Yamaha yz450f I run Faastflex bars that have elastomers for intentional flex.

A good point about fat bars is they are way strong. Fat bars on off road motorcycles have basically eliminated broken bars. You have to wod it up
huge to hurt them.


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## JonathanGennick (Sep 15, 2006)

jimbowho said:


> A good point about fat bars is they are way strong. Fat bars on off road motorcycles have basically eliminated broken bars. You have to wod it up
> huge to hurt them.


That's interesting, actually. Now you've got me curious. What clamp diameter do off road bikes use?


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## jimbowho (Dec 16, 2009)

Interesting question. While drinking coffee!!!

No micrometers. But a Mtn fat bar is amazingly fatter than a set of pro-taper
fat offroad bars. I slipped a stem on both, and Mtn is fatter.

Then got curious! Stock OEM offroad bars, and 25.4 Mtn bars are also different.
Mtn bars are a tad bigger also.

Someone with Mic's can chime in!! Good mornin.


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## LyNx (Oct 26, 2004)

For me this is a tad bit more than theory, it's true. I had an Easton EA50 low rise 25.4 bar/stem combo and when I stood up to hammer and used the bars as leverage they flexed so bad it worried me they'd break, got a EA50 flat bar 31.8 clamp and stem and that feeling totally disappeared - solid as a rock and I'm no big guy @ 6'2" and 170lbs.



LMN said:


> In theory 31.8 is stronger and stiffer. Personally I can't tell a difference but maybe a big guy can.
> 
> However I do like the look of the larger bar.


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## shickapooka800 (Sep 21, 2010)

Malibu412 said:


> Stronger, stiffer, less flex in the bars and stem. Quite necessary on the now more popular 28"+ bars.


I'd be curious to see when these really wide bars showed up. I hate them. Everytime I've ridden a bike in the last few months while shopping I keep thinking to myself "my sawzall could fix that..."

I just recently ran into this 31 vs 2x issue. I naively bought some 'mustache' looking bars to convert my mtb to more road use (after a decade+ of trails and urban pavement pounding) since I bought a new bike (still in the mail).

I fully expected to use my current stem, but when I got the bars I though "wtf is wrong with these fat things!" and then realized there are several 'standards' of bar OD. looks like I get to buy a new stem. good thing I broke a stem clamp bolt on my current rig while adjusting it for one last hoorah on a trail before road use.

ironically lever/grip/shifter manufacturers still make things in the smaller size, and it is widely accepted that the smaller size is more comfortable on the hand, so now all bars taper.... 
I would have solved the flex issue by buying those sweet dirt bike style bars with the cross brace (why don't those exist anymore!?).


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## LyNx (Oct 26, 2004)

......and yet the trend is moving towards even wider bars as people realise how much more stable handling they give you, especially in tech terrain. I for one have slowly moved to wider bars (only 27") but will def never go back to anything under that  The BS excuse about riding tight trails, is just that, BS. I can still ride my fav trail with all it's tight bushes, vines and rocks, yet even better now with my stable, wide bars.


shickapooka800 said:


> I'd be curious to see when these really wide bars showed up. I hate them. Everytime I've ridden a bike in the last few months while shopping I keep thinking to myself "my sawzall could fix that..."


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## shickapooka800 (Sep 21, 2010)

LyNx said:


> ......and yet the trend is moving towards even wider bars as people realise how much more stable handling they give you, especially in tech terrain. I for one have slowly moved to wider bars (only 27") but will def never go back to anything under that  The BS excuse about riding tight trails, is just that, BS. I can still ride my fav trail with all it's tight bushes, vines and rocks, yet even better now with my stable, wide bars.


i don't want that stability. it makes it awkward for me because the bike then argues with me when I want to flick it about. Note that I do agree it gives you improved stability. My argument is one of comfort and familiarity. I also agree that whining about catching the bar on stuff is mostly just that, whining. All things considered, I still like the feel of my relatively (for todays standards) narrow bars. I feel like my front end is a little lighter and more responsive to sudden vertical input from me. when I pull on some wide bars I get the sense that the bike is pulling even harder in return. it's like it is fighting me. 
still though, I'll never really feel to grumpy about wide bars because, well, I own a sawzall


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## boomn (Jul 6, 2007)

shickapooka800 said:


> i don't want that stability. it makes it awkward for me because the bike then argues with me when I want to flick it about. Note that I do agree it gives you improved stability. My argument is one of comfort and familiarity. I also agree that whining about catching the bar on stuff is mostly just that, whining. All things considered, I still like the feel of my relatively (for todays standards) narrow bars. I feel like my front end is a little lighter and more responsive to sudden vertical input from me. when I pull on some wide bars I get the sense that the bike is pulling even harder in return. it's like it is fighting me.
> still though, I'll never really feel to grumpy about wide bars because, well, I own a sawzall


it sounds like you are describing how the wider bars are slower to turn in, which is true but something I quickly adjusted to. However, the bike fighting and pulling against you is the complete and exact opposite of what I've experienced. Wider bars provide more leverage against the steering axis, which means rocks and ruts and such won't be able to deflect my front wheel as easily. I have relatively more say over where my wheel is pointed and stays pointed. I find this difference quite noticeable on chunky trails, such as having a much easier time riding along one side of a rut without my wheel being twisted where I don't want it to go. "Stability" in that regard is what I really like about wider bars

fwiw, switching to longer bars without shortening up the stem a little does have potential to not fit right and not feel right


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## shickapooka800 (Sep 21, 2010)

boomn said:


> it sounds like you are describing how the wider bars are slower to turn in, which is true but something I quickly adjusted to. However, the bike fighting and pulling against you is the complete and exact opposite of what I've experienced. Wider bars provide more leverage against the steering axis, which means rocks and ruts and such won't be able to deflect my front wheel as easily. I have relatively more say over where my wheel is pointed and stays pointed. I find this difference quite noticeable on chunky trails, such as having a much easier time riding along one side of a rut without my wheel being twisted where I don't want it to go. "Stability" in that regard is what I really like about wider bars
> 
> fwiw, switching to longer bars without shortening up the stem a little does have potential to not fit right and not feel right


i'm still going to peck at finding the perfect setup and I won't let the big-bar hate get in the way.

I was talking more about lifting the front end, not turn in and steering stability. the bikes I've ridden seem to hop better with an older standard width bar than with these newer, ever widening, bars. 
but that IS a good point about stem choice. 
I gravitate towards a stubby 0-rise stem and riser bars with little to no sweep back. why? because I can't shed my bmx background and to me that is what they should be. still after more than a decade and a half, I am still a bmx hooligan trapped on a mtb. i'd have it no other way though. that's why I told my GF when she was shopping for her first serious mtb "don't listen to me, don't let me ride it, just ask me if the components are good" beacuse I have a seriously perverted view of how a bike should handle in the mtb world. 
she got on my now retired mtb to try things out and she immediately got off and said "that thing is scary, i'm not riding it". 
god help me when my 29er comes in the mail. this could get ugly.


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## Harold (Dec 23, 2003)

shickapooka800 said:


> i'm still going to peck at finding the perfect setup and I won't let the big-bar hate get in the way.
> 
> I was talking more about lifting the front end, not turn in and steering stability. the bikes I've ridden seem to hop better with an older standard width bar than with these newer, ever widening, bars.


Sounds to me like what you notice is simply due to the muscles you've been using for so long being activated with the narrow grip, and the wider grip using different muscles that are not so strong.

Go to the gym and do a row with a narrow grip (similar muscle groups as lifting your narrow handlebar) for a few reps.

Then move to a wider grip and note how you "feel the burn" in a slightly different place.

Same thing as what you're experiencing, I think.


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## jimbowho (Dec 16, 2009)

Schickapoo. I promise! If you PM me with your address, I will ship you a cheap pair of pipe cutters. Please don't rape your bar ends with a sawzall!!!!! I am a plumber and beg your alliance to a cutter. 

I will throw in a De-burring tool also. You sound like my kind of riding partner.

Who cares!!! I'm sporting Fleegle bars at 28". I will not cut them down. 

NOTE!! I see old videos of fast guys running very narrow unit's. There's no way I can hang with their Mom's, Aunt's or uncles.


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## DeeEight (Jan 13, 2004)

JonathanGennick said:


> That's interesting, actually. Now you've got me curious. What clamp diameter do off road bikes use?


22.2 for standard bars, 28.6 for over sized. BMX bars the standard size is also a 22.2 clamp, and for many years early in mtb history when the bikes used parts available in japan for the BMX industry, there was sharing in stems and bars with 22.2 clamps. They moved to the 25.4 clamp though because it was a size that lighter/narrower alloy bars were being drawn in for the city/touring type bikes in europe (you still quite often find older road bikes with 25.4 clamp bars).

The move to bigger diameter mtb bars originally followed the MX bars with the same 28.6 standard size, but then skipped ahead 1/8" larger to 31.8 instead. Basically there wasn't a big enough difference between 25.4 and 28.6 to justify the change for most people or brands, but with 31.8 there was.


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## smilinsteve (Jul 21, 2009)

I think the new diameter is more a marketing decision than anything. There never was a problem with the old size, but there is a never ending push to make new stuff look better than old stuff. 
I have 27" LP composite downhill bars for the last 9 years. They flex in a good way to make them comfortable. I don't want them any stiffer. 25.4 aluminum bars are already too stiff. I think carbon is the perfect bar material, and 25.4 is a fine clamp diameter. 
The bigger bars are heavier. It's part of the trend toward "All Mountain" type bikes being the standard mountain bike, even though most people who buy them never use their all mountainness anyway. 
Big bars, big headsets, all that stuff, has its place on certain types of bikes, but it trickles down onto bikes that don't need it. 
Not that its a big deal either way.


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## tbear1 (Sep 6, 2010)

breakingbryan said:


> There's a strong correlation between handlebar thickness and badassness.


Best answer ever. :thumbsup:

Glenn


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## Clones123 (Apr 29, 2010)

You can have narrow, skinny bars like on all the cheap bikes, or you can have wide, fat bars like on the expensive bikes. Which ever suits your sense of style. Personally, I'm very happy to have gone from 620x25.4mm to 680x31.8mm...


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## boxman12 (Jun 13, 2004)

shickapooka800 said:


> I would have solved the flex issue by buying those sweet dirt bike style bars with the cross brace (why don't those exist anymore!?).


I've got one on my 25.4 risers. Made by Club Roost. Have had it for about ten years now. I may be scared to ride without it. :skep:


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## thaphillips (Sep 1, 2007)

I think bar width is a personal preference that relates directly to how big your shoulders are. I find it uncomfortable to have my hands gripping the bar far outside my shoulder width. The 31.8 bars taper out from the middle not allowing my shifters and brakes to be mounted as close to the stem as I like in some set ups. 

If you look at the frequency of bar failure you will also notice there is a very small percentage of bars that fail. Now ask yourself ...."How are parts manufacturers going to get you to buy more handle bars if your current bars are not failing?" ..... answer slowly change the standard.

Do I hate 31.8" bars? Not really .... do I have any reason to sell my 25.4" bars and buy new ones? .... Not really.

Do I need wider bars? I can ride just fine on my narrow bars without any "control" issues .... so not really.

Do I need the added weight of 31.8" oversize bars??????? NOT REALLY!

I have been on my MTB bike more than 10 years and seen many trends come and go. One thing all these trends had in common was that they had to claim to be better than the product they were replacing. Only a few of these trends have ever offered more than a marginal improvement.

I understand why many people would choose 31.8" over 25.4", but I don't think there is a need for anyone to sell there 25.4" bars and switch to 31.8" bars to get a performance improvement.


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## shickapooka800 (Sep 21, 2010)

boxman12 said:


> I've got one on my 25.4 risers. Made by Club Roost. Have had it for about ten years now. I may be scared to ride without it. :skep:


are those still made? I searched for club roost on google and at Jenson USA and all I could find was one set of cyclocross tires...

if anyone knows of a similar set of bars, please inform me, thanks.

you know what.... the first thing I would do with riser bars w/ cross brace would be to put a set of pads on them  I went barreling pubic bone first into my stem once.... not fun. that'd be my justification for some rad pads...


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## shickapooka800 (Sep 21, 2010)

back on topic: I have seen a lot more trail riders use exotic sweep/mustache handle bars. could it be that the extra clamping area keeps the bars level despite all that extra torque? I mean, back when all the bars were basically strait tubing, you didn't see a lot of torque on the bars, now that many people use crazy beach cruiser-esque bars on their trail bike (WHY?!) the bars get torqued a bit more under stress.

edit: because frankly I'm not buying the stiffness argument.


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## pitbull592 (Jul 23, 2010)

I just bought my first 31.8 bar (bontrager cf race lite). I'm a top heavy guy 5' 8" 235 & thought it would just be a bit more stable. I really like this setup, though I'm not a big fan of wide bars, because I'm short & stocky & I feel too stretched out. I think you need to find what components work for your body. After playing with spacers/stems I feel I finally have my cockpit dialed in.


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## boomn (Jul 6, 2007)

shickapooka800 said:


> back on topic: I have seen a lot more trail riders use exotic sweep/mustache handle bars. could it be that the extra clamping area keeps the bars level despite all that extra torque? I mean, back when all the bars were basically strait tubing, you didn't see a lot of torque on the bars, now that many people use crazy beach cruiser-esque bars on their trail bike (WHY?!) the bars get torqued a bit more under stress.
> 
> edit: because frankly I'm not buying the stiffness argument.


you're really good at doubting everything you've never tried 

I've owned singlespeed bikes with both clamp sizes and did notice a difference in stiffness when standing and pulling on the bars to climb, and this was with much narrower bars on my 25.4mm setup that didn't have as much leverage to flex the stem interface anyway. I honestly haven't really noticed anything in steering stiffness, but I'm also not a freerider or a downhill racer

As for the "crazy" bars, many people find the different hand positions very comfortable for their wrists and arms, especially on longer rides. Some bars even offer multiple hand positions to switch up your grip and further prevent soreness


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## charging_rhinos (Jul 29, 2008)

larger diameter means more resistance to the tensile and compressive forces along opposing sides of the bar as it flexes (providing the wall thickness is enough not to crap out). Every material has its optimal diameter vs thickness ratio, so that's why steel frames can get away with being smaller in diameter. Same reason we don't see many aluminum frames with 1" diameter tubing.

I DEFINITELY noticed a difference in the riding characteristics, but bar quality ranges a lot from company to company. Add to that, varying the wall thickness (double and triple butting the tubing), and some narrow bars could, in theory, outperform thicker bars. But a good set of fat bars should always be more rigid/stronger than the thinner sets.


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## pitbull592 (Jul 23, 2010)

because it looks cool


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