racer_dave

FWIW I looked up the shear load for the 3/4" high carbon clevis's on my late model. According to the book they have a shear strength of 310,000lbs. I'm pretty sure that'll cover a stock mustang. Obviously there are also cheap a$$ clevis's out there so make sure you buy good ones. And just becasue its grade 8 doesn't mean it really is, counterfeit GR 8 stuff is all over the place.

The strut tubes are what's cheap on the race car, they are aluminum and sell for about 20-30 bucks. And they fold up easily to protect the high dollar hubs, spindles to protect the chassis.

I think this setup is pretty solid, and to be honest I was figuring on doing something similar on my stang and have been watching this with interest. I was going to go a different way. For $600 I can have a full late model front clip with all the suspension and rack mounts. I was going to graft it into the mustang frame rails and then bolt on my racing parts. Gives me huge adjstments, light weight and coil-overs & rack all in one. And I can get the roll center (moment center) any place I want it to balance the car.

I'm still undecided because I really like my clip idea, but I'd run on this pretty hard with confidence. Awesome job so far.

And if you're anywere near me I could use help most Saturday nights :-)

Norm Peterson

I don't think shear strength is what's critical here. More likely it's reversed bending and cyclic fatigue.

As long as none of your loads are trying to bend the clevis, you're probably going to be OK. I suspect that means that the ball joint center needs to be located as close to the plane of the lateral link and strut rod as possible. Otherwise under braking you will get a bending moment in the strut and the lateral link will try to twist.


Norm

racer_dave

On my race car, the shock mount, clevis attachment, and ball joint are within about 2" of each other. Ball joint at outer end of lower strut, clevis back about 1" and coil-over mount back about another 1" at most.

The spherical bearing on the other end of the strut lets is rotate the bit it needs to, but in 5-6 inches of travel it doesn't bind up the spherical bearing, so there shouldn't be enough twist to affect the clevis. As long as the other end of the strut doesn't bind up under compression/rebound there shouldn't be any twisting force to worry about.

Trying to recall and I don't think I've ever seen one fail that wasn't due to car vs concrete. He used steel swedge tubes if I remember right, so under an impact he's going to have more force transferred through the suspension points, but at that point he'll be rebuilding it all anyway...

OCHOHILL

Norm,

They don't get it. Because Ron Morris has a similar kit, they think it is OK.





If the general public understood the compromises in many suspension kits, a lot less kits would be sold.

What forces are applied to the clevis if the car was driven in reverse at speed and the brakes were firmly applied several times? What happens when backing out of a parking space and the brakes are applied
What is the difference? This relates to Norm's comments.

buening

Ocho don't take my reply as being OK with it, just pointing out that I found it interesting a commercially available kit uses the same clevis set up. Only time will tell with this, and eZ sounds like he's running hit hard to find its weak spots.

racer_dave

I guess Port City Racing, Lefthander Chassis, Shaw, Rayburn, Howe, Childress, Rocket, GRT (Companies with engineering staff in house)... are all selling race cars with inherent suspension problems then. These cars are driven at speeds over 150mph on tracks banked 15-33 degrees. Pulling way more than 1 G in the corners and containing engines with up to and past 700HP in some cases and have 4-6 piston brakes that put huge rotational forces on the spindles and tires that have 10x the grip of street tires. If there's an inherent safety problem these cars would all be eating concrete regularly when the clevis failed, and they don't. Not even with all rubbing, wall scraping etc...

I do understand what the thought train is behind all this, but I don't agree that it's a problem. As long as the other end of the strut has the correct rotaional movement, the clevis won't twist or bind. I've never seen one fail in 27yrs of racing and if it was an issue I'd have seen it at some point.

buening

Dave, in your experience how often are these suspension compenents (specifically the clevis) replaced on these race cars? If they only last a few races, then the fatigue cycle is very small compared to a street car that would have them on there for years. Sorry eZ, I didn't mean to bring up this dead horse lol

racer_dave

My current Lefthander late model chassis is a 2006. The right side was replaced once in 2007 due to concrete impact. Actually the two lower strut rods and upper a-arm took the impact, but I replaced the clevis, rod ends and hub to be safe. The left clevis has never been replaced and shows no signs of fatigue (stretch marks, discoloration, misalignment). There have been times when racing action has caused damage to spindles, strut rods, wheels, but the clevis' haven't need to be replaced. The rod ends get replaced when they go out of tolerance. They usually last for 3-4 years barring impact damage.

buening

Thanks for the feedback Dave! Does this car have a similar stut rod/LCA setup as our mustangs? Just making sure we are comparing apples to apples, since you mention its a late model chassis.

Norm Peterson

The devil is in the details. So when you're designing to use a clevis from the get-go, you can end up with a design that a clevis can live with. There is no guarantee that a modified OE production design will be that good, as it was built around a different set of compromises.

I'm not even saying that you couldn't make a modified OE arrangement that uses a clevis OK, just that throwing one on there without considering what's going on is throwing parts at a problem without knowing what the problem is. I'd hate to hear where some unknown copycat took a clevis idea, tried to run with it, and ended up with something that truly was unsafe.


Norm