Karvalo wrote: ↑Thu Oct 14, 2021 10:57 am
tjvirden wrote: ↑Tue Oct 12, 2021 9:17 pm
Where does cable rub come into this?! As far as I can see, cable rub, or any other abrasion, is the irrelevance.
I saw some people when the recall was first hinted at assuming it was about cable rub - I thought you were also making that assumption when you talked about marks. I was clearly wrong about that, sorry for creating confusion.
Specialized are saying it's exceptional impact - it must be truly exceptional, because there's plenty of evidence of heavily used SL7s exhibiting no problems at all - no marking/damage to the steerers at all from any cause. Making the assumption that the steerer laminate (composite structure) was properly specified and made, then it really does take a huge impact to crack it, even with a load concentration onto the steerer - I can perhaps imagine a 120Kg rider using a long stem hitting a decent size, raised bump in the pavement at high speed with straight arms may be able to do it, but the bars will almost certainly fail first.
Right, that's my point. You can get loads of unmarked steerers that haven't been hit hard enough in the right way. So what?
Okay, we're on the same field as to the possible cause then.
I can accept the idea that just because something looks fine and hasn't failed so far, doesn't mean it is "good". The expression "absence of evidence doesn't equal evidence of absence" springs to mind. However, the SL7 has been out for ages with an enormous number of Kms in total for all the bikes out there.......yet there seems to be a distinct lack of damage to steerers; what gives?
How often does a brand specify a maximum stem length and maximum bar reach (distance the hands are from the steerer is really what I'm getting at) for a frameset? Or that only a particular stem can be used with their steerer? Those variables directly affect the forces on the steerer. Most framesets now have a rider weight limit, but that is only one of many important variables - what do you design for? Anything can be broken - it just takes a big enough force.
An example of this is the picture floating around on the net of a Look HSC5 SL fork, separated at the crown (it was a moulded-in-one construction) from a 20 mph impact into a log - I still use a 14 year old HSC5 that has covered many tens of thousands of Kms, and I lose no sleep over it.
