Thread: Rear susp questions

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Some food for thought.....NASCAR uses the truck arm suspension because it's mandated in the (sometimes archaic) chassis and suspension rule book!!!! Left to their own devices the engineers and crew chiefs would not be using that setup. Left to their own devices, the teams would have cars that weighed 1,000 lbs. less and handled like a slot car instead of a sled......

just remember that there are 2 items to consider in any rear end-----------you gotta have it mounted to push the vehicle, you gotta mount it to carry the weight-------


Other thoughts-------a quick change doesn't have the strength of the ford 9, the extra gears on the back are a gear mesh problem and drag, unsprung weight, much bigger mass under car, and more difficult to change ring/pinion


I was at Hendricks shop one day when they were cleaning out Gordans TEST trailer and they have 37 ford 9s setting there with the stuff----

You would think that when NASCAR went to the "Car of Tomorrow" they would have updated the allowed suspension.

I guess as long as everybody has the same setup, it doesn't matter how archaic it is. As long as the crews can make it work, it's good enough.

The truck arm suspension does have the advantage of being heavy duty. Probably important went they racing gets rough.

Originally Posted by Hotrod46

You would think that when NASCAR went to the "Car of Tomorrow" they would have updated the allowed suspension.

I guess as long as everybody has the same setup, it doesn't matter how archaic it is. As long as the crews can make it work, it's good enough.

The truck arm suspension does have the advantage of being heavy duty. Probably important went they racing gets rough.

True, but my main problem with the NASCAR rule book is the stupid weight!!! Some really good engineers and they still won't go with the simple fact that less weight creates less energy to be absorbed in a crash... A lighter car with IRS and rack and pinion on the front would have less energy to be dissipated when it's crash time. Pieces absorbing some of the initial and subsequent "hits" would dissipate far more energy on a lighter car then having everything Sherman Tank heavy and making the seat and the driver the weak link in absorbing crash energy! I'll take structure over mass any day!!!!!!

well they are only using the didea/layout of the truck suspension and not really truck parts----------


and they build in 2 or more separate points in the chassis as cut off points for repair of crashed cars

I'm talking about the heim joint itself. The threaded bung it goes into wouldn't be moly. The 67 chevy 2 drag car I built had regular heims in the 4 link when I bought the kit. Half way through the season I had to replace them with chrome moly heims. I'm just thinking that there will only be 2 points there that is taking all the abuse. I'm going to try bushings I think. Anybody got any ideas on a bushing that will be large enough to take some abuse? I actually got a 70 chev truck out here now I'm working on for a friend, going to take some pics and a few measurements. I've had 2 people that have told me to use poly bushings. They both said if I keep the bars long, and close together in the front I don't have to worry about flex. I plan to use 2x4 box, 1/8 wall for the arms.

how are you going to mount the tops of the coil overs??????

They will be coil springs, like the dirt cars use and a set of good gas shocks. I will build a crossmember for the springs at the top, and they will mount to the bars at the bottom. You could even make them adjustable at the top like nascar does if you wanted to be creative. I'll have to fab a way to attach the springs, you couldn't just set them in there. Friend has a bunch of those springs in different spring rates.

Oh, so you aren't using coil overs--------- With a more normal coil spring you could usesome of the base pieces from something oem and install a spring a little longer than the space for it and it would stay in place just like on a stocker------

I'm just going to get the longest pair he has and throw in it. After I get everything together, I'll figure out what rate I need. Don't have a clue what it'll weigh, out of the factory it was 3065 lbs.

"Don't have a clue"?????????????? You should weigh the car before you even start this project because spring rates and installed heights can be calculated and will make the whole effort easier to do with much more predictable results------also the mounting angle and suspension arm leverage need to be part of the planning for the design

I got the car in a 1000 pieces. To set it up, I'll just do it at the ride height I want. If you decide to build a drag car, full chassis, how you going to weigh it 1st? Same deal.

I have the poly version of these in my 72 Chevy. The chromoly ones would be really nice.

Forged Ballistic Joints & Bushings

To answer your question about how I'd build a drag car would take posting a lot of pictures and me and this site don't get along on that------


also, I start by mocking up the rear end with an alighnment tube in a 9 inch ford pinion housing that is the same size as the main bearings of what ever engine I'm using--then I set the mockup engine at the distance from the rear axle centerline for the eliminator/class,etc that is desired an set the engine driveline angle----------from there, I set up the front wheels/spindles/struts at the desired wheel base and castor/camber angles---------next is the mockup of the lower two main frame rails from the rear end mounting up forward to includethe inner lower a arm mounts plus cross member for rack/pinion mount---------from this point its time to start mounting body panels but sometimes will use a stripped out mock up body so as to have correct diminsions to build roll cage before using the minumin panels for roof and quarters-----of prime importance at this point is clearance for headers, intake manifold, and that the doors swing open and close correctly-----------

We're just talking chassis in this case. If you know what ride height you want, distance between floor and crank centerline, eng and trans placement, it's not that hard. If you get the car completed and it doesn't set like you want, you change springs or whatever it takes to get it there. I've built a few race cars, 4 link and ladder bar. I think I can handle this.