SUMO FRONT SUSPENSION HAZARD !!!!!

[dave]

Spoke to a friend of mine today who has a newly SVA'd and registered Sumo.
His car has been on the road for just under 2 months and done less than 50 miles.
He jacked up the front of the car on the chassis,nothing unusual in that until the front wheel left the ground whereupon the top balljoint SNAPPED.
This was a new top balljoint (Transit drag link)that was fitted when the car was built.
It seems that the balljoints run out of travel before the shock absorbers do...not a good idea!
Fortunately this happened while the car was on the jack,just imagine if it had happened going over a hump back bridge...The outcome could have been catastrophic.
It might be an idea for Sumo Mk 111 sierra based owners to jack up the front of the car on the chassis,remove front wheels,loosen shock absorber and see if you can remove it,and then re fit it. If it can be re fitted without the use of pry bars or adjusting the spring seat etc(just slots straight in with no effort)you should not have the above problem.If it wont fit then you may run the risk of your front suspension letting go.
SERIOUS STUFF EH!!!!!

[PeteV]

Hmm.... sounds like this one needs further investigation. In the particular case that you quote Dave, surely the top joint must have been pretty duff to give way under just the weight of the wheel when being jacked-up ?. Although if the mechanism you describe is real, perhaps the ball joint got that way through being bottomed-out a few times whilst on the road ??

When you say snapped - do you actually mean snapped or came-apart ?


Pete.

[Kevin W]

If the ball joint had run out of rotation first, doesnt that mean that it was built with it under tension in the first place?

If I remember correctly, the build manual show that you fit lower wishbone to chassis, then fit shock to upper chassis mount and then offer up lower wishbone to botton of SPAX shock absorber.

Then bolt on upperwishbone to chassis, and lower this onto top of axle stub. You then have to set the camber (or was it caster?) with suspension on full droop. I remember doing this and it was one aspect of the build where there were no problems, forcing of components or other arssing about that I can remember. Could this car have been on the road with incorrectly set-up suspension, perhaps set too low - I think that would have the same effect, say if ride height was lowered without re-setting suspension properly after an SVA (headlanp height) test.

Or do you mean that the balljoint broke where it goes into the wishbone? Now thats something else entirely.

Kevin

[sideoiler]

the top balljoint is under a slight load at full droop (well it is on mine)and i remember phoning pilgrim with my concern at the time of build however he reasured me although not ideal it was safe after all it had passed the tuv test.I do remember that there were some balljoints produced with restricted movement this was documented somewhere, which could bind at full deflection dangerous to say the least .were these fitted to said sumo
If anyone is overly concerned it wouldn't take much to fit a check strap to take the strain at full droop

[dave]

>Hmm.... sounds like this one needs further investigation. In the
>particular case that you quote Dave, surely the top joint must have
>been pretty duff to give way under just the weight of the wheel when
>being jacked-up ?.
It is not the weight of the wheel that causes the problem ,it's to do with the fact that there is a spring capable of holding up the front of the car (isn't it a 450 lb - inch spring on a Sumo)pushing against it,when really the shock absorber travel should have run out before the ball joint reached the end of its travel.

Although if the mechanism you describe is real,
>perhaps the ball joint got that way through being bottomed-out a few
>times whilst on the road ??

Bottoming out does not affect the top ball joint as it is still within its operating range.
>
>When you say snapped - do you actually mean snapped or came-apart ?

The part that screws into the top wish bone snapped.
>
>
>Pete.

According to my friend a mechanic with 20 years experience told him that the designe of the geometry was wrong and that caused the undue loading on the ball joint.

P.S. I feel that i must point this item out as i feel it is the right thing to do for my fellow members safety ,however i also have to tread carefully in just what i say as we all know what happens to people who make statements regarding this particular Cobra replica.

[dave]

It snapped where it went into the top wishbone.
Where it snapped i feel is irrelavent cos if one snaps when you're on the road the outcome would be the same....frightening.

[dave]

>the top balljoint is under a slight load at full droop (well it is on
>mine)and i remember phoning pilgrim with my concern at the time of
>build however he reasured me although not ideal it was safe after all
>it had passed the tuv test.

Ditto...I did build a Sumo 3 years ago same probs,same answer from the manufacturer.

I do remember that there were some
>balljoints produced with restricted movement this was documented
>somewhere, which could bind at full deflection dangerous to say the
>least .were these fitted to said sumo

I don't know in this case , but the car i built 3 years ago hab ball joints supplied by Pilgrim.

>If anyone is overly concerned it wouldn't take much to fit a check
>strap to take the strain at full droop

But who will....I think the manufacturer should supply one with the kit.

[robert]

>P.S. I feel that i must point this item out as i feel it is the right
>thing to do for my fellow members safety ,however i also have to tread
>carefully in just what i say as we all know what happens to people who
>make statements regarding this particular Cobra replica.

Dave

Point 5 of the Acceptable User Policy.

5. All posts are deemed to be the opinion(s) of the poster. Such posts can be used if deemed defamatory and the poster could be held liable.

When shal we see you in court?

I know a good lawyer.



Robert
Forum Admin

http://www.cobraclub.com/flags/UK.gif

[PeteV]

>It is not the weight of the wheel that causes the problem ,it's to do
>with the fact that there is a spring capable of holding up the front
>of the car (isn't it a 450 lb - inch spring on a Sumo)pushing against
>it,when really the shock absorber travel should have run out before
>the ball joint reached the end of its travel.


I should clarify my original comments & add that yes, not just the weight of the wheel & suspension bits but of course any spring loading thats also present - I had probably incorrectly assumed that at full drop the spring would be almost un-loaded. However, I would have hoped that the top joint could easily take a loading well in excess of a few hundred pounds even when bound. Although this is obviously not what the joint is designed to do surely if it can't take this kind of loading what happens when subjected to the huge 'sideways' loads caused by heavy breaking ??

>Bottoming out does not affect the top ball joint as it is still within
>its operating range.

By bottoming out, what I meant was suspension at full drop - I probably should have said 'topping out' !




>The part that screws into the top wish bone snapped.

Dave, do you mean the threadded bit or the actual ball-joint casing ?

Back to my previous argument - surely its going to get loaded in a similar way under breaking conditions - where it will be subjected to a much greater loading.

Pete.

[PeteV]

>It snapped where it went into the top wishbone.


If it snapped here sounds to me like a duff balljoint - its always going to see a big load here when under braking etc.

A different issue altogether is whether a Transit drag link is the thing to use for a top ball-joint - but the Lotus 7 brigade have been using these for years (in albeit a lighter car) without trouble.


Pete.