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Carbon steerer stiffness (Look)(2 posts)

Carbon steerer stiffness (Look)DanH
Jul 6, 2001 12:54 AM
I am currently riding a Look HSC-3 (1 1/8in), with the steerer cut down to just below the top of the stem (~1mm, ie no spacers above the stem). I recently upgraded to this fork from an Icon Air Rail with an alloy steerer. I have found that in sprints and hard climbs, I notice increased flex in the front end. Also, after a bit of riding, the front can emit some clunking noises on hard out-of-the-saddle efforts. When I readjust the stem/headset area, the noise goes away temporarily, but later returns.

I think this is all due to the steerer tube being quite flexy - is this a property of all carbon steerer forks, or are the Looks particularly bad? Would it be improved if I had cut the steerer off above the stem and had a spacer between stem and headset cap? I had heard some comments about flex prior to buying, but I figured the oversize tube should be stiffer than the standard 1inch.

Anyone have any recommendations for a stiffer all-carbon fork? (I am a bit of a weight-weenie and want to avoid going back to alloy.) I have heard good things about the Easton EC 70 & 90, and the AME alpha q.

Thanks for the advice.
headset adjustment...C-40
Jul 6, 2001 5:03 PM
The LOOK HSC-3 fork with 1-1/8" steering tube should be plenty stiff. I think you're confusing headset adjustment problems with fork flex. First, be absolutely sure that the steering tube is not only cut below the top of the stem, but also below the bottom of the top cap. Some top caps have a reduced diameter on the underside that protrudes below the top of the stem. This style works on steel and aluminum tubes, but not on CF tubes. If the top cap isn't totally flat on the underside, it could be clamping against the steering tube, instead of the stem. You should be able to apply enough pressure with the top cap bolt, to cause minor binding of fork when you try to turn it.

Normal adjustment should place a light preload on the headset, with zero play. After the preload is applied, tighten the steering tube clamp bolts on the stem, and then apply another 1/8 turn to the top cap to insure it doesn't vibrate loose. If adjusted properly, the headset should almost never need readjusting.