Bar diameter

[Zipperhead]

Oh noes, I'm all confused.

For a quill stem, which is the standard bar diameter, is it 25.4 or 26mm?

Do Cinelli use something larger than 26mm?

TIA.

[border-rider]

Oh noes, I'm all confused.

For a quill stem, which is the standard bar diameter, is it 25.4 or 26mm?

Either ?

Do Cinelli use something larger than 26mm?

yes.  26.4 I think, or at least they used to

[Biggsy]

25.4 traditional. See S Brown for others.

[Biggsy]

Modern road quils are 25.8 or 26 depending on make.

[Biggsy]

Modern Cinelli quill is 26.0.

[border-rider]

Modern Cinelli quill is 26.0.

The old stuff is different though.

[Zipperhead]

Why do manufacturers have to mess around with such fractions of a millimetre!

So, I've a pair of bars which are 26mm (measured), in a Cinelli stem, which has a fractured clamp bolt. I've got a new stem but I can't remember what size it is - definitely not 26.4.

Am I going to get anywhere by trying to measure the inside diameter of the stem?

[border-rider]

Try it and see ?

If it's too tight it's too tight (just be careful not to score the bars), but if it's too loose you can shim it with a bit of coke can.

[Zipperhead]

I was hoping to work it out without putting metal to metal.

The new stem is still wrapped up, so I could take it back and change it if necessary. Perhaps I should just go back to the shop and ask them!

[Biggsy]

Measuring stem no good. Research stem, with photos, or buy yet another stem.

[Biggsy]

Umbranded cheap stem likely to be 25.4.  Find out or measure bar diameter then buy decent stem.

[Zipperhead]

Umbranded cheap stem likely to be 25.4.  Find out or measure bar diameter then buy decent stem.

Ah, that's given me an idea - it's not a cheapo unbranded stem, but a nice branded one. If I google it when I get home I can have a look.

Hopefully I won't find that it's available in 25.4 & 26mm!

[rogerzilla]

Here we go:

25.4mm is ISO standard.  Normally found on non-road bars, i.e. MTBs and everything else.  Also used on some OEM dropped bars, especially Japanese and other Far Eastern ones.

26.0mm is an unofficial Italian standard.  Used on*most* aftermarket dropped bars.

31.8mm is oversize, and is the same whether for "MTB" or "road".

Cinelli used to use 26.4.  Some manufacturers make stuff in 25.8 for compatibility with both the normal-sized "standards".

Stems with a removable front are generally tolerant of 25.4 or 26.0, although 25.4 in 26.0 looks a bit happier than 26.0 in 25.4, which may pinch the bar and weaken it.  With conventional one-bolt quill stems you really need to get it right, although you can shim a 25.4 bar for a 26.0 stem (or a 26.4 Cinelli stem).

It is all very silly.

Next week: ISO vs JIS crank tapers, and the impossibility of finding out which you need.

[Biggsy]

Some ITM & 3T are 25.8 - interchangable with 26. Older road often 25.4 as well as mtb.

[Zipperhead]

It is an ITM. I'll have to have a play around tomorrow.

[Euan Uzami]

to add to the confusion I have got some bars and a stem that are 24.8.

[Zipperhead]

Well, the answer at the end of the day was - it didn't matter.

You see, I thought that the clamp bolt had snapped at the back, but I found that it hadn't, but was a nice recessed allen bolt, and when I had looked at it in poor light I hadn't noticed that.

Of course, I only saw that everything was ok when I had chopped the gear and brake cables, removed the bar tape, removed one lever from the bar and then taken the bar & stem off.

Ah well, some nice new cables & bar tape and peace of mind isn't a bad price to pay for my stupidity.