Handlebar clamp sizes - does it matter?

[Ajax Bay]

I need to replace my drop handlebars (the drops are noticeably bent in a bit, one side more than the other).
It's an old (1999?) bar (so it's had a good innings) and its clamp OD is 25.4mm. It has a reach of 110mm and a drop of 160mm, which I'd like to reduce if possible.
It's attached to a quill stem with a bolt-on faceplate (2 bolts) which looks a good fit to the bar.
There are rather few bars with 25.4mm clamp sizes but a few more with 26.0mm clamp size, in particular this Deda one: Dedacciai-Piega-26-Handlebar which has a reach of 75mm and a drop of 130mm (attractive) BUT a 26mm OD clamp size.
The wiki says "The ISO standard for the clamping area of a handlebar is 25.4 mm (1 inch), . . . however, the Italian unofficial standard is 26.0 mm, . . . . . In practice, many modern stems with removable faceplates allow for slight differences in handlebar clamp diameter, but the older type of stem with a single pinch bolt must be accurately matched."
Would my current stem put up with a 26mm OD bar (ie grip it satisfactorily and securely)? What are the risks?
[I appreciate an alternative is to go for a quill to threadless converter and then use a 'modern' stem and a 31.8mm clamp size bar, but looking at the 25.4 to 26.0 interface to start with - I have to confess I like the aesthetic of a quill stem cf a converter).]

 

[Yellow Saddle]

Hmmmmm. I dunno. I've had plenty of cases the other way round.

Firstly, now is the right time to replace that bar. A drooping alu bar is severely fatigued and will fail imminently.

Secondly, a stem with only two bolts offers no redundancy and, the bolts will be at the end of their useful life too. Since you can't just replace them with any old bolt, why not just bite the bullet, fall in love with threadless and convert that sucker of yours. I did it recently and felt all sentimental at having to give up my beautiful swan-neck Cinelli. But, guess what, I haven't thought about it again until now, and I actually don't care.

Besides, are you sure that stem of yours can still be removed? Next time you replace headset bearings may just be hacksaw time in anyway.

Nevertheless, I'm watching to see if anyone has done the 25.4 stem to 26 bar experiment and still have all their front teeth.

 

[DCBassman]

Although I've no fatigue ussues to deal with, the Trek 800 is getting a threadless converter so I can put the wider Norco bars and stem on it, as well as the Norco's 8-speed shifters.

 

[rogerzilla]

If the stem has done the same mileage as the bars and the bars are bent, I'd replace both.

If you must keep the stem, Nitto do good 25.4mm bars.

 

[Ajax Bay]

are you sure that stem of yours can still be removed? Next time you replace headset bearings may just be hacksaw time

Stem is removed regularly and I serviced the headset bearings only a few months ago.
Thank you for the advice (and you'd mentioned the two bolt no-redundancy issue before).
@rogerzilla thank you - I have the Nitto bars on my list as the 25.4mm option (but the reach/drop are both more/deeper).

 

[rogerzilla]

See if you can try a bike with Nitto randonneur bars (B135AA). I'm a big fan, even though they look as if they've been under a bus.

 

[biggs682]

Why not get some shims ?

 

[fossyant]

I did it recently and felt all sentimental at having to give up my beautiful swan-neck Cinelli. But, guess what, I haven't thought about it again until now, and I actually don't care.

Nooo, not on a classic bike.

 

[Ajax Bay]

Why not get some shims ?

I hoped you'd comment. But not sure where a shim would be of use. I have a quill stem (with 2-bolt faceplate) which looks designed to clamp a 25.4mm bar. How/where would I use a shim (the preferred bars are are 26.0mm in the centre)?
Looking at the quill stem adaptor option, the quill itself is obviously 22.whatever to fit the threaded steerer ID, but the top part seems to provide a 25.4mm (1") OD section.
But there are almost NO stems (none with a 4 bolt faceplate anyway) which will fit: they are nearly all 28.6mm (1 and 1/8"). So if I use a quill stem adaptor then it seems I must use a shim. Is that correct?

 

[DCBassman]

Strange, not managed to see any other than 28.6mm OD for these adapters. They're not standard A-head unless 28.6, surely?

 

[biggs682]

@Ajax Bay sorry i didn't realise you were trying to fit a 26.00 mm bar in a stem designed for a smaller diameter set , if that is the case i would not suggest you do that .
Unless the faceplate follows the contour of the clamp area on the bars without any gaps when just held in place .
Quill stems with faceplate's are quite an oddity i have one on my Falcon Explorer mainly because it came with the set of butterfly bars i fitted .
I think the quill stem adapter allows a lot more choice of stem lengths and ease of swapping them about , and they come in all clamp sizes although not many look as good as an old fashioned quill stem .

 

[Ajax Bay]

Strange, not managed to see any other than 28.6mm OD for these adapters. They're not standard A-head unless 28.6, surely?

Have you seen a link to a 28.6mm one?
Been into my LBS and the one they have has a shim on the top (gives 25.4mm or 28.6mm options). But it's silver and I need black, like this link:
https://www.wiggle.co.uk/deda-quill-stem-adapter/
Top Features:

• Fork steerer inside diameter 22.2mm
• Stem inside diameter 25.4mm

To assemble threadless stem on traditional threaded fork and headset.
This converter will allow you to fit a 1" threadless stem to a 1" threaded steerer.

 

[12boy]

Never have had a quill stem fail, thank goodness. I have felt some give in the combo of long stem (long from bar to quill, not up and down) and bullhorns, though. More an issue is getting AL stems to give a bit so as to get a lightly larger handle bar in there. Having read this post I may quit that since it may stress the AL too much. I have a couple of front face plate quills, although they were mostly made for Mtn Bikes. Sure is nice to switch bars without having to take grips, brakes and shifters off one side or the other.

 

[DCBassman]

Have you seen a link to a 28.6mm one?
Been into my LBS and the one they have has a shim on the top (gives 25.4mm or 28.6mm options). But it's silver and I need black, like this link:
https://www.wiggle.co.uk/deda-quill-stem-adapter/
Top Features:

• Fork steerer inside diameter 22.2mm
• Stem inside diameter 25.4mm

To assemble threadless stem on traditional threaded fork and headset.
This converter will allow you to fit a 1" threadless stem to a 1" threaded steerer.

Just ordered this one...

 

[biggs682]

Have you seen a link to a 28.6mm one?
Been into my LBS and the one they have has a shim on the top (gives 25.4mm or 28.6mm options). But it's silver and I need black, like this link:
https://www.wiggle.co.uk/deda-quill-stem-adapter/
Top Features:

• Fork steerer inside diameter 22.2mm
• Stem inside diameter 25.4mm

To assemble threadless stem on traditional threaded fork and headset.
This converter will allow you to fit a 1" threadless stem to a 1" threaded steerer.

Have you looked at what SJS offer https://www.sjscycles.co.uk/stems-accessories/