101 replies to this topic

[Nev]

 

 

 

 

 

 

Oops forgot to put any text with the photo. Anyway just a little pictorial as regards the HCB's, these 2 are fronts, but as you can see, the long one is as clean as a whistle, the short one however is fairly heavily corroded at the midway point,, and must have some impact on its strength, just goes to show that you should be changing them out with some regularity.

  The failure point on the snapped ones is on the non-threaded shank of the longer bolts (in my case and on another that I asked the owner about).   To eliminate that rust issue, use either stainless shims or aluminium shims (as I do) instead of the Lotus' "optimum" rust inducing mild steel. Another example of where the Lotus parts are sub-optimum, not that I think that rust is serious enough to weaken the bolt great deal.   Having said that it did strike me that a build of up rust + salt between the many layers of the shims might cause extra tension on the bolts. This is why I'd recommend a more inert shim material. Ideally, making a single shim of the correct thickness is better than a stack of multiple shims, as it reduces the number of failure/slippage points and also reduces the risk of rust/salt crystal build up between the layers.        

Ooof!  Some care needs to be taken Nev.  The shims need to be a certain hardness so aluminium will need to be VERY carefully selected for the right grade and is itself prone to corrosion especially when in contact with iron like suspension parts.  Stainless will likely cause corrosion in other bits... like the bolts....through galvanic corrosion.   I use the lotus shims (which come plated and passivated) along with a smear of anticorrosion grease to help prevent rust.  Eventually they will rust but they are cheap enough to replace.

Well said FLD, the voice of reason. I think your chosen path is optimum.

Does the grease not reduce the friction of the mating faces of the joint? You fit higher spec bolts to increase the torque to maintain a higher clamp load on the joint surely you want to maintain that Friction? And going back a few posts on the other thread related to hcb's isnt the shear strength directly related to the ultimate tensile strength?

 

That was my immediate thought when it was mentioned. There was a previous thread (same one?) some time ago where someone explained that the friction created on the mating faces by the clamping force of the bolts is an important component of the joint. That being correct, would not grease on the mating surfaces compromise that friction?

 

 

 

Just confirm Nev, you are using the 12.9 bolts on ally uprights?

 

 

 

Yep, but bear in mind that they are going into threaded steel inserts within the aluminium.  

[Spitfire Engineering]

 

 

 

 

 

 

 

Oops forgot to put any text with the photo. Anyway just a little pictorial as regards the HCB's, these 2 are fronts, but as you can see, the long one is as clean as a whistle, the short one however is fairly heavily corroded at the midway point,, and must have some impact on its strength, just goes to show that you should be changing them out with some regularity.

  The failure point on the snapped ones is on the non-threaded shank of the longer bolts (in my case and on another that I asked the owner about).   To eliminate that rust issue, use either stainless shims or aluminium shims (as I do) instead of the Lotus' "optimum" rust inducing mild steel. Another example of where the Lotus parts are sub-optimum, not that I think that rust is serious enough to weaken the bolt great deal.   Having said that it did strike me that a build of up rust + salt between the many layers of the shims might cause extra tension on the bolts. This is why I'd recommend a more inert shim material. Ideally, making a single shim of the correct thickness is better than a stack of multiple shims, as it reduces the number of failure/slippage points and also reduces the risk of rust/salt crystal build up between the layers.        

Ooof!  Some care needs to be taken Nev.  The shims need to be a certain hardness so aluminium will need to be VERY carefully selected for the right grade and is itself prone to corrosion especially when in contact with iron like suspension parts.  Stainless will likely cause corrosion in other bits... like the bolts....through galvanic corrosion.   I use the lotus shims (which come plated and passivated) along with a smear of anticorrosion grease to help prevent rust.  Eventually they will rust but they are cheap enough to replace.

Well said FLD, the voice of reason. I think your chosen path is optimum.

Does the grease not reduce the friction of the mating faces of the joint? You fit higher spec bolts to increase the torque to maintain a higher clamp load on the joint surely you want to maintain that Friction? And going back a few posts on the other thread related to hcb's isnt the shear strength directly related to the ultimate tensile strength?

 

That was my immediate thought when it was mentioned. There was a previous thread (same one?) some time ago where someone explained that the friction created on the mating faces by the clamping force of the bolts is an important component of the joint. That being correct, would not grease on the mating surfaces compromise that friction?

 

 

 

Just confirm Nev, you are using the 12.9 bolts on ally uprights?

 

 

 

Yep, but bear in mind that they are going into threaded steel inserts within the aluminium.  

 

 

Ahh OK when I sent you the U2U I assumed you were talking OE steel uprights.

So are you using converted Elise S1 uprights or something else?

 

Gaz