Originally Posted by
Banzai
I've been a stickler about CF steerer spacers and manufacturers tech data in other threads...but I'm starting to wonder just how precise this needs to be. (probably needs its own thread, really...)
For instance; Cannondale CF steerers. Due to the interface C'dale specifies NO spacers on top. Period. Yet the C'dale pro tour team bikes are pretty much all violating that guidance on their shiny Supersix Evos.
Other CF steerers, like Bontrager; 2-3mm above the stem, with a 5mm spacer. This is due to their interface.
Easton EC90; 7-8mm above, with an ugly honking 10mm spacer. Yet with their unique thread-in "bung", and the thickness of the CF steerer, why not 2-3? And, of course, pics of bike shop and team bikes routinely show "violations" of all these things. Aside from some Bontrager forks, there have not been a rash of steerer failures out there. (And Trek blamed FSA in the end, so there we go...)
Like any rule of this nature, its nuanced. Purpose of course for safeguarding against a stack of spacers on top is lack of expander reinforcement where it matters down below. Specialized which has a pretty elaborate and long reinforcement expander for example had a recall on their forks for breakage. 99% of riders won't be affected. Its worse case 'stack ups' that kill companies. What is this? Its an anomalous combination of events.
In this case, a hospital visit may result if:
- Big stack on top of the stem
- Stem bolts overtorqued
- Stem clamp design creating biggest stress riser
- 250 lb weight lifter sprinting out of the saddle in the drops putting ridiculous torque of the handlebars.
Mfr's have to safeguard designs against worse case scenario. Most of us would not be affected by stacking spacers above a stem. I have done it on many bikes. And of course, no two manufacturers have the same expander designer or even the same fork steerer tube strength. So difficult to quantify the risk for any given bike model...mostly being rider (weight and strength) dependent.