Just to add clarity to this important topic, a single Mango supplied HCB failed on the rear of Nipper, due to a massive pothole (which also bent a wheel very badly as well). So this was not an issue with the bolts themselves. Personally I believe the bolt failed due to me previously curbing the car and then not checking/replacing the bolts (ie point #1 below), in conjunction with what must have been a hell of a pothole impact.
My personal thoughts for HCB failures are these:
1. When wheels hit curbs, this is when the HCBs will be stretched. Anyone hitting a kerbs should really check their bolts havent stretched (ideally replacing them as a matter of course). If the bolts stretch when they no longer clamp at full torque and are subject to unintended shear forces.
2. As JG has corectly said, I suspect some people are not cleaning their threads out first, so the torque value they see is not that of the bolts head biting into the hub carrier, ie part of the toque value exerted by the fiter is simply overcoming the resistance of the badly cleaned threads.
3. I doubt many owners check the torque on all their HCBs on a regular basis, IMO they should be, seeing how critical to life and limb they are. I check mine proably every 6 months or so and even more (double + tripple checks) after any change of spacers.
4. Some Geo places that aren't aware of this bugbear on VX220s may not take as much care as they should when they fiddle with settings.
5. If people put a lot of spacers in, then new longer bolts should be bought so that there is sufficent thread contact.
6. Perhaps some people have lowered their ride height too much, such that their damper bump stops are being hit regularily. I reckon this would increase shock loading stress on the bolts (as oppopsed to the nice slow absorbion of energy by the spring + oil).
As a bit of extra info, due to the unusual front geo setup I have I was forced to use 12.9 bolts (I coudn't find any 10.8) and have not had any problems with them. Other people (I remember SteveA with the orange stage4 car which was tracked a lot) also had no problems with 12.9 bolts.
Edited by Nev, 20 October 2014 - 11:51 AM.
