Hi,

The front lower wishbones on my car are sliding and chopping off the end under braking force. I have them pinned but it doesn't appear to be enough to hold them. The same thing has happened on both sides, and it's the second time this has happened. Approx. 15 events from new to this.

What am I doing wrong!?

Cheers

 

How freely do the control arms/bushing move when you install the arm in the car and push/pull it up and down?

I initially had problems with poly bushing binding due to the poly shoulders being too wide. Basically the bushings when installed in the arm were wider than the steel sleeve, so there is a lot of force being applied to them just to rotate the control arm. I ended up using a belt sander to reduce the shoulder thickness of the bushings, which made the arms fit easier in the subframe and the arms move much more freely.

 

The arms fit easily into the subframe, don't bind, and moves relatively freely. Energy suspension bushes FWIW.

I am fairly sure it's the control arm force (in a longitudinal direction) slicing the end of the bush off, rather than any issue from the bush rotating axially.

 

Delrin is the answer.
Check out the Bushing Megathread: https://www.miataturbo.net/suspensio...cussion-87573/
Under track braking conditions the thrust force is pushing the arm forward "rearward" and crushing/cutting through the rubber bushing collar.

 

Rearwards, but yeah; braking forces need to go through a thrust surface somehow. Not sure at which point (tires) this becomes an issue though.

 

Yes sorry, rearward. Post corrected. I had this happen on track with Yokohama AD08R, so moderately grippy tyres and heavy brake zone did it for me.
Neddy, check all your other bushes too. When mine did this the rear lower outers and rear inner uppers had all pushed out too.

 

Why not replace those "doughnuts" with steel washers?
Chop the bushing down to the sleeve and have a thick washer (with the sleeve going through) take up the slop on the rear sides of the arms.

It will make some noise of course, maybe some softer material between this washer and the subframe?

 

Definitely not steel. Some sort of POM plastic would be what I would use. Nielex makes a similar product, albeit for OEM and their bushings.

https://nielex.net/footwork_as.html

 

Thanks for the replies. I'm going along with brake forces. Not sure about steel washers either but perhaps Delrin bushes as suggested are the solution...
EDIT: I can't see how how the poly / bronze kits would help?

 

The poly bronze thing just stops the poly binding. Different issue to what you're having. The delrin bushing (think of it as a solid bushing) takes all the thrust forces so the control arm cant shift rearwards and cut into the other bushing. What you use in the second bush position is up to you (rubber/poly etc).