# Caution with Stronglight chainrings & Campy Ultra Torque Cranksets



## tom_h (May 6, 2008)

A caution, so that others don't have the problem I had. This only applies to 2010 and earlier Campy carbon cranksets, having the 2-piece chainring bolts.

Ordered Stronglight brand, "Type D", 11 sp, 50/34 chainrings as a replacement for worn-out 2009 Campy Chorus 11sp rings.

The Stronglight looks well manufactured and finished. The arrangement of pins & ramps on the big ring is different than Campy, but not necessarily better or worse -- haven't tried it yet.

PROBLEM:
1) On _big_ ring, width of the Stronglight mounting pads , is about 0.5mm thicker than Campy.

2) On rear of _small _ring, the bolt holes have a shallow shoulder, just like Campy. But on Stronglight, the shoulder is about 0.5mm shallower, thus the male screw protrudes about 0.5mm less.

3) net result, there is about 1mm less thread engagement of the chainring bolts. That's about a 20% reduction.

When torquing the soft aluminum alloy chainring bolts to spec (70 in-lb), the bolt threads stripped, due to less thread engagement :mad2:

In hindsight, a possible workaround may have been: clean off all grease from the bolt threads, apply blue loctite, then torque to a lesser value (50 in-lbs ??). The loctite would have prevented bolts loosening, which normally the correct torque will accomplish.

Now that several of my bolts are stripped, I am checking into whether Fulcrum-brand bolts will fit. 
Fulcrum part # CC-R100 is a STEEL bolt kit, with vastly greater strength than aluminum, so less thread engagement should be OK.

As many of you know, Fulcrum is Campy, just re-badged so Shimano/SRAM guys don't have to put Campy parts on their bike ;-)

Will post updates.


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## martinrjensen (Sep 23, 2007)

If you greased the bolts prior to torquing them, unless specifically mentioned in Campy's spec, you almost for sure ended up effectively over torquing them. Most torque specs assume no grease. Adding grease lubes the threads which allows you to tighten easier, which in turn allows you to end up having greater pressure on the bolt/nut for the same (dry) torque setting. This means that if your torque wrench was set to 70 in lbs, your actual torque value on the bolt was well north (greater) of that. How far north, I can't tell you but you did mention that you stripped threads. 

If you didn't put grease on the threads than you may have a point.


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## tom_h (May 6, 2008)

Yes, possibly true. Threads were greased. 

I have previously removed & re-installed the original Campy rings & bolts once, maybe twice. Greased threads both times. No installation or removal problems, then.

The additional effective torque with greased threads (up to 20% by some accounts) and less thread engagement, was apparently beyond the design margin of those aluminum bolts.

Still, I am now officially an alumimum chainring bolt hater ;-) Even Ti would have been preferable.

I note on my track bike, where frequent swapping of chainrings is expected, the chainring bolts are steel!


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