I tried some searching but somehow have not found the answer. I would like to change the Cinelli 1A 100mm stem ( with the older oval logo ) for a 70mm. There are two on ebay at the moment but I am not sure about diameters. The bike is a late '70's Italian make. The handlebars are 3ttt. Are they 26.4 or 26mm clamp size? I cannot accurately measure the difference. Also, is the insertion diameter 1"? One stem is 22.2mm. Thank you for any assistance.

They are most certainly 26.4 in that era.

BTW, I have a beautiful 70mm black stem attached to some 64 bars wrapped in black stitched leather that I have been meaning to post up.

My one concern was the fact that 26.4 was the stem clamping diameter and that other products such as 3ttt were 26.0 or less. I guess that means 3ttt made bars for the earlier Cinelli standard. Don't forget to show us your Cinelli stem and handlebars!

3ttt made 26.0 bars. Cinelli made 26.4 bars. I think it was the late 80's before Cinelli made 26.0 bars. I think to find 26.4 bars you will need to find Cinelli bars. There are plenty out there.

The only picture I have at the moment of the Cinelli leather wrapped bars is from a distance when they were on my wife's bike. I'll try to snap some proper pics tomorrow in the daylight.

if you want to sell your 100mm stem please hit me up.

I am wondering how it is the 3ttt bars fit the Cinelli stem. I have had them since buying the bike in 1978 with no issues. In fact I never thought there could be an issue until I looked into getting another stem and finding out about the different diameters. The 3ttt bars flare out to a larger diameter at the clamping area, and tightening the clamping bolt on the Cinelli stem has presented no difficulty.

If the 3tt bar is a 26.4, it should be marked somewhere. Maybe they made 26.4 bars, I really don't know, but have never run across a set.

So what you are saying is you have a Cinelli stem clamped to 3TTT bars and would like a shorter Cinelli stem to replace your existing one? If so, I think you have a 26.0 handlebar with a 26.0 Cinelli stem, so you'll need a 26.0 Cinelli stem if you buy a different one to use with your 3TTT bars. And 22.2mm is the correct insertion diameter.

EDIT: I think it would be worth it to go to a bike shop and have them measure the clamp diameter with calipers, so you know for sure what you have-

I have run into a set of off brand-vintage-non Cinelli bars and stem at 26.4mm so I guess they are out there.

I have too, Specialized that were actually rebranded Cinelli.

I have a 70mm Cinelli stem that I may end up not needing. I will need until next weekend to make this determination (& confirm dimensions, but I assume the diameters are standard for 70's Cinelli, whatever that is). The original pinch bolt is missing and has been replaced with a standard hardware store chrome plated allen head capscrew and chrome plated nut. However the bolt from your 100mm stem should be compatible.

There was one-I can show you when you come back North.

Thank you everyone for trying to help out. The only real way to know is measure them accurately with calipers as well biked mentioned. I keep reading that Cinelli was 26.4 only back then. That is the problem until they are measured! holiday76 - if you are interested in my 100mm it has some insertion marks at the point where the stem is inserted in the accompanying image and a few scratches, see the photo if it helps. And old's cool, keep me informed on your 70mm and whether the dimensions will allow me to use it with my 3ttt bars, I am interested!

Will do. Shoot me a PM on the 2nd if you don't hear from me by then.

I snapped some pictures of the Cinelli bar/stem combo I have available, for those who were interested. 70mm stem, 64/38 bars:

https://picasaweb.google.com/zmudshark/Bars#