albrt 

This is probably a dumb question for those of you who work with high end components, but how is it possible to install handlebars in a stem clamp that's too tight without scratching the bars at all? I mostly work with basic co-op bikes and worrying about scratching the nice Cinelli bars is not my usual problem.

I have a bike with a nice set of Cinelli bars set in a 3TTT stem clamp. The bars appear to measure 26.0 using my (very basic) calipers. I can't measure the stem clamp because it has a set of bars stuck in it.

The stem is way too long for me so I started disassembling. I removed the bolt from the stem clamp completely, but the bars barely move in the clamp.

Seems obvious that the stem clamp is too small, but my question is how did somebody put this setup together without the slightest sign of scratching on the bars? If there is a secret technique, please let me in on it so I can use the technique to get the bars out without trashing them.

Is there an alternative explanation, such as the clamp somehow got deformed after the bike was put together?

oneclick 

It does not take much spreading for a bar to become loose. I either wedge a bit of something between the clamp faces, or use a stout set of snap-ring pliers to spread them; once it's past the centre-bulge/sleeve it's easy.

juvela

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the 3TTT clamp size is 26.0mm

the centre section of the Cinelli bar may be 26.4mm

DO NOT SPRED CLAMP TO ACCEPT A LARGER BAR CENTRE THAN CLAMP SIZE


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albrt 

The more I look at it, the more I think the clamp may originally have been too big. I can see light between the bars and the clamp on the back side, but at the bottom where the gap in the clamp is, the two ends of the clamp are very snug against the bar, like they were bent inward.

fliplap

Older Cinelli bars were 26.4mm. That 3TTT stem is probably 26.0.

And the obvious answer to removing some Cinelli sized bars from a stem that needs spreading, is a “Cinelli Size” stem spreader



I kid of course, that stem spreader is meant for Cinelli stems. Though really, it works a treat on most any 1A clamp style stem, eg Nitto Pearl and Technomic, but not Dynamic or dirt drop stems.

sd5782 

Get a large screwdriver or small chisel to act as a wedge and drive it in the bolt slot after the bolt is removed. It doesn’t take much.

albrt 

That's what I normally do. I did that, and it made a small difference, but not enough to get the bars out without significantly marring the finish.

I was looking to see if maybe there's a shim stuck in there, that's when I noticed that the clamp seems to be out of round.

albrt 

After some more looking and prodding, the clamp appears to be slightly oval with the long axis from front to back. The shorter axis from top to bottom is where the problem is. I tried to get a picture but I can't get a good angle with my limited photo capabilities.

I said a few comments back that maybe the clamp was too big and the ends of it were bent inward when it got over-tightened. Now I think it is more likely the clamp was too small and it got overstretched from back to front when it was pried open. This makes sense because that's where the force would be exerted by prying at the opening, and the top of the clamp is the thinnest part, so it would deform the most. The back 1/3 is set into the solid end of the stem so it probably wouldn't deform at all.

I may just cut this stem off. Hate to do it because it was a nice stem, but I don't actually have any use for it.

sbarner

I have a pair of Craftsman snap ring pliers that I often use for spreading stems. Unlike the more common version that have pins to engage in the holes in a snap ring, these have serrated, flat jaws. I wish I had one of those Specialized tools or its equivalent, as I need to be very careful when using these to minimize marking of the stem in the clap area. The idea of using a screwdriver or chisel makes me cringe, as I've seen so many stems butchered by this very technique. The ideal is to get the bars out or in without leaving ANY marks.

When I have a stem like a Nitto that has a binder bolt that threads directly into the aluminum, I reverse the bolt and insert a quarter in the slot. The bolt pushes against the coin and this pushes the front of the clamp open. To use the language of garbage Internet ads, it's genius.

To get the stem around the bends, remember to orient the clamp on the inside of the curve. That's why quill stems are tapered on the bottom of the clamp.

Pompiere

I have a small flat prybar like the one on the left. It is polished smooth, so it doesn't mark up the stem.

tiger1964 

Never seen one of those! I wonder how hard to find one?

albrt 

OK, I sawed into the top of the clamp until it spread easily and released the bar. Stem is destroyed but I got the bars out with no marks on the visible parts of the sleeve.

After looking at the wear marks on the inside of the clamp and the bars I'm pretty sure the clamp was too small and was overspread to get the bars in, so the integrity of the stem was probably questionable anyway.

oneclick 

Yes, of course; but for any who misunderstand how important this is -

juvela is using upper-case. You have been warned.

dddd

Lots of old stem clamps and handlebar centers end up mis-shapen from over-tightening over the years, especially the thinner-walled lightweight parts that became common during the 90's. This prompted today's 31.8 and 35mm handlebar clamping diameters, which need less squeeze on the bars to hold firmly.

I've often used an Allen key inserted in the clamp gap, then rotated 1/12 turn to adjust/grow the gap and clamp diameter by up to a mm or so, as shown below. Seems to leave no scar.
Below I am shown "honing" out a 25.4mm clamp to accept a better-dimensioned "modern" 26.0mm bar for my 1968 Sears 10 SPEED. The honing dowel is sized correctly enough and is self-aligning as I twisted the stem around the dowel, to assure a nice, straight, round bore. Identical stems are sold having 26.0 diameter already, so there was plenty of "meat" on this hot-forging to pull this off safely.

I used this model of Origin8/Kalloy stem because it is made to fit 22.2mm and 22.0mm steerer ID's within proper tolerances (also to increase the stem's reach from 8cm to 10cm).

Bergz

Excellent trick, thanks 👍