In Reply To:
I don't have any engineering background but I'll take a crack at this. It seems to me that a fork steerer tube has to, and will flex. You run into a potential problem wherever something stops the flex in an area and then concentrates it all instead at a specific spot. I would say these points will be at the bottom of the stem, the bottom of the aluminium insert(if you have one) and at the top and bottom of the headset. I think you have a real risk of a failure if two or three of these points coincide.
It looks like Rod's might have failed right at the top of the headset and maybe the bottom of the insert was also at that point. It also sounds like he had no spacers under the stem, meaning the top of the headset and bottom of the stem were also pretty much at the same point.
I think the guidelines should be:
- a few spacers under the stem so there is an area for the fork to flex between the top of the headset and below the bottom of the stem
- make sure the bottom of the insert doesn't coincide with the bottom of the stem OR the top of the headset
Greg.
That makes sence and sounds like what Cervelo is suggesting on their forum.
It looks to me like they are disagreeing with True Temper's instructions. They are saying one measurement that contradicts the manufacturer. It's a touchy subject if True Temper treats it as slander on their building skills. I would why the differences? It seems like Cervelo has the more conservative setup though.