MIN 

Sorry noob question but I can't find an answer: 25.4mm (MTB) stem use with 26mm (road) bars. Possible, ill-advised or not at all?

MattRennick

I'm pretty sure that they can with a shim.

jayrooney

you can shim a 25.4 bar with a 26 stem, but you can't do the opposite.
it wn't fit.
if you use an openface stem that's 25.4 with a 26 bar it will crimp the bar.

MIN 

Yes this is for a 26mm bar and a 25.4mm stem. So .6mm makes that much of a difference huh?

dutret

maybe a timelord shim

It will hold the bars but will focus pressure at the ends of the clamp since the curves won't match. Depending on the bar it won't be a problem or it will snap.

MattRennick

I definitely read the OP backwards. Boy is my face RED!

Nims

I will openly admit to having no practical experience with this topic, but I'm surprised to hear you say it's a significant difference.

.6mm = .024" I'd bet that on average quality parts you can see almost that much variance in part tolerance alone. Maybe not. I really have no idea, I'm just making conversation. The Nitto bars I just measured came in at 1.005-1.007" for an actual diameter.

Have you done this and had it crimp the bar?

lvleph

If you put a 26.0mm bar in a 25.4mm stem, there is the possibility the bar may snap, from being pinched.

obstacle

Ummm, ya. Common sense wins again. Yippie!

Nims

There were 6 replies... would it really have taken that long to read them all?

dubstylee

I just put 26.0 Salsa bars in my 25.4 Bontrager clamp on my cyclocross bike. Worked fine for me. I have an open-face stem.

I asked the guy at my LBS when I picked up the bars, and he said he's done it many times without a problem.

I would think as long as the threads on the stem engage you'd be okay.

You could always try sanding a bit of material away from the stem with some sandpaper on a cylinder of some sort near the same size.

fetch

cut up soda cans for shims FTW

bonechilling

"There were 10 replies... would it really have taken that long to read them all? "

11.4

Crazy thread. Half the answers are for the reverse combination of bar and stem.

Lots of bars and stems are anything but precise in how they're measured, and many aren't even round. Just get out a caliper and you'll quickly see this. So that means some people get away with this kind of mismatch if their bars and stem happen to cooperate in their imprecision. Plus, if you were clamping on a bar with a large reinforcing shim (such as Nitto track bars have) or a steel bar, you are less likely to have problems than with an internally expanded standard road bar or a lighter track bar.

But to someone's question, I have seen two crimped bars and one bar that actually bent and broke from this kind of mismatch. You have to remember that the actual measurement is the circumference of the bar or the stem clamp -- and that's a good bit more than the diameter (circumference = 3.14 times diameter). I've seen problems with adequate clamping between 25.8 and 26.0 mm bars and stems, so this is in fact plenty. Just put a 25.4 bar into many 26.0 stems and you'll see what 0.6 mm diameter amounts to -- it often prevents the stem from holding the bar without rotating.

Retem

nitto shim I use one works great close thread now

bwa ha ha I mixed it up

you might be able to stretch the clamp but it isn't the best thing to do just get a new stem they are cheap

Nims

As least you preface your posts with admission of dyslexia...

redtires

You can do this...I've done it on my own bikes in the past for one reason or another...but I would have never, ever done this to a customers bike, just for liability and the fact that a good mechanic does not do stuff like that to people's bikes. I would say that if you are using a steel or titanium stem you should have zero problems but I would not recommend it with a forged alloy stem, as they just don't have the malleable properties of the two former mentioned materials. I also would not recommend this combination if you are using a very lightweight alloy bar, especially one that is manufactured with a "bulged" center, or one made from a composite material. Your just not going to crimp a "regular", shimmed alloy road bar. A question though...do you already have a bar in your possession? Most of the Nitto bars come in a 25.4 diameter and would be compatible with your mtb stem.

MIN 

What? Then why are they called 26.0mm bars?

lvleph

I read them, but I decided to put it in one reply.

They have both if I recall. I know my B123 are 25.4mm.

MIN 

I started this thread because I want to get something like this for use with my Nitto RB021 bullhorns. Silver 70mm is nice.

11.4

The Nitto B123, 125, and 127 are 25.4. Several of the road bars and I believe all of the bullhorns are 26.0.
Do your bars have a sleeve in the middle? If so, these stems may be wider than the sleeve and won't be able to mount properly. Worth checking. A Thomson Elite mountain stem in 25.4 just barely handles a Nitto B123 alloy sleeve.

You're aware that bullhorns don't have much reach and to use a stem with no reach, you'll be poking your ribs with your elbows. You likely need a longer stem.

crbrown

I've been using a 25.4 clamp with 26.0 bars for some time now. There's a little gap between the removable front and the stem body, of maybe 1mm on both topside and underside.

I don't think you can really torque those screws enough to break butted aluminum... and if your bike is setup properly, there shouldn't be a whole lot of force on the handlebars when you're riding.

There are situations where a large amount of force may be put onto the handlebars (i.e. when you're shifting your weight over the front wheel for long skids). I would probably avoid this seeing as the fit is less-than-ideal.

BuddyMike

I put 26 bars into a 25.4 stem. Works fine. It wasn't open-faced either. I win.

Gordiep

Absolutely brilliant.

I think SRAM is working on a 'Tardis' line.

mykrrrr

I did it w/my old RB021's and the stem that came on my RL925. No problem/no crimping of the bar.