Or any 7 type car for that matter :eek:

Speed humps are harsh on any car's suspension system .... How's about a nice 4X4 .... One thing for sure though .... Over time, speed humps will even FUBAR a 4X4s joints, like I said .... They are service parts ;) :D :D

IF your realy unsure, speek to Martin at MK sports cars, or someone from the MK owners club.

TT

I just take em slow slow slow. Does a lot less damage over time.

TT

maybe just try visualise whats going on in the suspension.

when you go over a bump the wheel goes up the spring is pushing down
if the spring is acting on the top of the upright through either the bone or joint in effect its clamping the assembly together the load is on the top spring mount

where the spring is is pushing down on the lower arm as the wheel goes up
the spring tries to hold the lower arm down and in effect is trying to force the lower swivel joint apart
thats why the lower swivel joints are quite specific
cheers les g

Maybe your over thinking it all.This design has been used by all the manufacturers incl caterham ,westfield,dax etc. I think if there was a problem with the design one of the large manufacturers ( caterham etc)would have modified it and everyone else would have followed suit.Also remember that the roadster chassis has been design on cad and tested for stress etc.
Maybe you just need to slow down over speed bumps:D
Just my 2p worth

its not so much the ball joint i am worrieds about its the knock not being able to take the constant impacts

correl i think you are worried over nothing. the original sierra setup doenst come into play here as the only part we are using is the hub.

the reason why we dont use the sierra bottom ball joint is for the reason you are trying to get at. it cant take the forces we want it to.

the maxi ball joint was chosen as it is a lot stronger and designed to be used in a twin wishbone design rather than a Mcphereson setup.

as far as i am aware almost every kit car manufacturer uses the maxi joint and i have never heard of one fail ever, even under racing conditions.

the other thing you need to think about is how many miles do you do in 2 years in your daily driver before the ball joints fail? at a rough guess it would probably take you 10 years to do the same mileage in the roadster, factor in the extra strength and the lower weight and i doubt the ball joint would fail in a very long time.

as for speed bumps you dont need to worry, you will only have about 100-120mm ground clearance so wont be going over any :D

I think Correl has fallen into one of the regular 'traps' on suspension design here.

This explaination comes from a supplier of track control arms to major OEM's:

"The track control arm, ball joint and lower section of the upright are NOT unloaded as you have presumed although thats how it looks when the vehicle is stationary, a substantial anti-roll bar passes through the track control arm and when cornering considerable forces are applied to try to pull the track control arm from the upright. The ball joint and lower part of the upright must be able to withstand these forces or they'd fail in service."

If that's what is required for the donor vehicle then I'm sure it's not a problem here.:)

My MX-5 has a very narrow part to the upright in the area you indicated and that has the spring and vehicle load acting on the lower wishbone.
The haynes design and many like it will work fine as they put less load through these parts that would have been the case with the donor vehicle due to their lower weight.:) :)

Ash as stated above the Sierra ball joint and most others CAN take the load or it would fail when you go round a corner as the anti-roll bar puts considerable forces through the track control arm, i.e. most of the load from the unloaded side of the car is transfered to the loaded side through the ARB pulling the TCA from the upright.

Hope that explains it BV.

^^^^^^Like wot he said^^^^^^^:D

Correl, I understand your argument is that the bottom part of the hub is not engineered to be the point of most of the force transfer. However, consider the following along with the other excellent points people have brought up above:

* The widely used Cortina upright looks flimsy in comparison with the Sierra design.
* Sierra parts have been the mainstay of the kit car industry for many years, no problems of uprights failing being reported.