I was unaware that Cinelli made a larger diameter aluminum expander bolt. All of my Cinelli stems, 1A, 1R, XA and so on have steel expander bolts.
My experience with aluminum expander bolts has only been with the 6mm diameter aftermarket bolts made to fit Cinelli 1a and some 3TTT stems.
It would make sense then that a larger diameter aluminum bolt would be stronger and less likely to have problems.
Michael, I was going to mention your suggestion to draw up the wedge with a steel bolt first but I already had foot in mouth disease. Same thing with aluminum and titanium crank arm bolts.
I have an aftermarket 6mm aluminum expander bolt and wedge I got years ago that I keep as a collector's item.
The old 1-2-3 rule of thumb for material strength and weight was what I was thinking about in my original post.
Aluminum 1 Titanium 2 steel 3
In general, aluminum has 1/3rd the weight and strength of alloy steel. unalloyed titanium is in between.
There are aluminum alloys that can be heat treated to give tensile strengths over twice that of annealed low quality steel.
There are also titanium alloys that can be heat treated to much higher strengths than most common steels. The problem is that many metals get hard and brittle when they are heat treated to those high strengths so their usage is limited.
Back in the 70s when Campagnolo and others started making parts out of titanium, the used unalloyed CP (Commercially Pure) grades of titanium. CP titanium falls into the 1-2-3 spectrum.
Today, most CP titanium is used for corrosion resistant applications. Titanium alloys like Ti AL6-V4 (6% aluminum, 4% vanadium)is used for machined parts while Ti AL3-V2.5 (3% aluminum, 2.5% vanadium)was developed for improved weldability and drawing seamless tubing.
Chas. Colerich Oakland, CA USA
euromeccanicany@yahoo.com wrote:
> Some Cinelli stems came with aluminum bolts, and they work just fine. The long bolt's function is to draw up the wedge, which is what actually holds the stem. If it is going to break, it'll break when you tighten it. After installation, the bolt isn't subject to torque or shear, and isn't really holding anything together, which is why you generally have to whack the head to free the wedge to release the stem. Obviously you should inspect the bolt to see if there is any deep pitting or corrosion on it (usually white powder). Also, use some anti-seize compound on the threads & under the bolt head.
> Michael Shiffer
> EuroMeccanica, Inc.
> 114 Pearl Street
> Mount Vernon, NY 10550
> (914) 668-1300
> euromeccanicany.com