MR2 Championship

Fitting new pads this evening, found this:



FFS!! Not again!! This time on the rear O/S.

Anyone has this?

What I suspect is happening is that 'cos the car is so low the arm on the anti-roll bar to the drop-link is nearly vertical when the car is still and the suspension is unloaded. When the suspension is loaded the 'bar doesn't have enough travel and is trying to act like a beam axle. The mounts are the weakest point so they fail. Maybe try raising the ride hight of the car a little or see if you can fiddle with the length of the drop-link (i did look at this and it hurt my head so i left it, ride hight would be easier)

buba wrote:What I suspect is happening is that 'cos the car is so low the arm on the anti-roll bar to the drop-link is nearly vertical when the car is still and the suspension is unloaded. When the suspension is loaded the 'bar doesn't have enough travel and is trying to act like a beam axle. The mounts are the weakest point so they fail. Maybe try raising the ride hight of the car a little or see if you can fiddle with the length of the drop-link (i did look at this and it hurt my head so i left it, ride hight would be easier)

I hurt my head too on this at the front, but decided that with the shock so far up into the arch that the droplink needed to be extended to get the angle of the DL back to original.....we never did the rears though.

[quote="LuckyP...we never did the rears though. [/quote]


ah. Maybe . . . .

The angles change so much depending on the load/unload on the suspension that its very difficult to know what to do for the best, not being able to move the drop-link mounts. I couldn't decide if lengthening the drop-link would help or hinder. Ee be gett'n too mathmatickle for my bodgers brain, youm'd need a 'puter to work ee ouwt!

OK, not-a-mechanic here but here is my twopen'rth,

- Did the "tear" start at the top or the bottom? I would say the bottom because of the closeness to the weld at that point.
- If this is correct, this means that the force that started the tear will have happened when the suspension was trying to reach full compression.
- If that is correct, the droplink reached its maximum travel (while being compressed) BEFORE the car hit its bumpstop. Effectively the ARB/droplink is doing part of the bumpstop's work?

If all the above is correct, it would mean that running without bumpstops or perhaps shorter would increase the risk of this failure.

The possible fixes would be:
- raise ride height (but you're not really going to do that on a race car)
- fit bumpstops if none fitted
- fit taller bumpstops and/or spacers
- shorten the droplinks (but I don't think you are allowed to make them adjustable length(?)

I'll be interested to see if the experts agree.
Cheers JOHN

I'd also be interested to hear what other people have to say about this and more importantly how to safeguard against it as this is all way above my head!

Just a thought Pete, but as you use your car on the roads (much bumpier than most circuits we go to) do you know if the damage is happening on track or off it?

WillJohnson... If the roll bar was prevented from moving while the wheel/suspension was still moving up the lug would have been ripped off from the top (strut moving up link being held) i believe. I see why you think the crack propagated from the weld but i think it propagated from the change in profile, which would make sense the corner radius would be a stress raiser in this failure. (when mine failed on the front it looked as thought the drop link had pulled out the bottom of the bracket).

Does anybody else think the bottom half of the crack doesn't look new!!! just looks like what would be fresh metal looks slightly rusted. this would make you think the crack has slowly propagated until the final failure across the weakest point.

just some thoughts.


James

rob barnett wrote:Just a thought Pete, but as you use your car on the roads (much bumpier than most circuits we go to) do you know if the damage is happening on track or off it?

Could well have been on road Rob. Hmmm...

rob barnett wrote:Just a thought Pete, but as you use your car on the roads (much bumpier than most circuits we go to) do you know if the damage is happening on track or off it?

Not sure about this one, unless you drive like a total loon on the road your never going to work the car like you would crashing curbs or charging through gravel traps (not that you do either I'm sure!!) on a track, but roads are bumpier. At the end of the day it doesn't really matter 'cos you need a fix either way. Maybe longer drop links is the way to go. Would adjustable drop links be allowed, 'roll bars are free, would this count as part of? If so you could play with differant lengths as see how it felt.

buba wrote:

rob barnett wrote:Just a thought Pete, but as you use your car on the roads (much bumpier than most circuits we go to) do you know if the damage is happening on track or off it?

Not sure about this one, unless you drive like a total loon on the road your never going to work the car like you would crashing curbs or charging through gravel traps (not that you do either I'm sure!!) on a track, but roads are bumpier. At the end of the day it doesn't really matter 'cos you need a fix either way. Maybe longer drop links is the way to go. Would adjustable drop links be allowed, 'roll bars are free, would this count as part of? If so you could play with differant lengths as see how it felt.

Have you not seen Pete's video from the Ultima?! Only joking Pete