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Metric Street Stocks


Truck99

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Terry T. did exactly that with the 01 car early this year I think - short panhard with the 4 link still in place. His thinking was that the panhard bar became the determining factor in the rear roll center equation rather than the 4 links. I think he may have unhooked one of the upper links also in the end. But I think you're right JP about the angles of the links. Those two uppers are just nuts.

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If you could write a realistic cad cam simulation for a stock metric rear suspension, you would see that adding the panhard bar without undoing at least one of the top control arms simply adds to the bind already inherent in the four link geometry when body roll is present. You cannot believe all the various forces working against each other to produce massive amounts of bind (especially if you use stiff rear control arm bushings).

 

However, unhooking the right side top arm (legally, illegally whatever) and adding a relatively long, fairly level (not going there in this explanation) panhard bar allows the rear suspension to remain relatively bind-free through 3.5 inches of body roll as measured by rr shock travel.

 

Even better would be the removal of both upper rear control arms and adding the ubiquitous third link centered over the axle housing and the addition of the panhard bar. Someone paying attention to the rest of the rear geometry should be about to obtain about 4 inches of body travel at the rr shock without suspension bind with that setup.

 

Of course, this explanation is vastly oversimplified. One could write a book on the ins and outs of the metric 4-link rear suspension, but why???

 

Nick Holt

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The why is the interest shown about this topic in just two days. Terry T. seems to be the only one who has tried any of these ideas. While I get that adding the panhard bar won't change roll center in this case,do you think by limiting bind from side loading it would help some? in a car that doesn't have a lot of body roll?

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The why is the interest shown about this topic in just two days. Terry T. seems to be the only one who has tried any of these ideas. While I get that adding the panhard bar won't change roll center in this case,do you think by limiting bind from side loading it would help some? in a car that doesn't have a lot of body roll?

 

You bring up a couple of issues.

 

1) Body roll.

 

It is true that one could put very stiff springs in to make sure the body does not roll far enough to get into the suspension bind during cornering. But usually (on pavement anyway) the car with relatively soft suspension springs and very good suspension geometry has the advantage over a car with very stiff springs and poor geometry.

 

2) Adding panhard bar to stock 4-link.

 

Keeping the chassis centered over the rear end is a good thing (unless, of course, you are using planned rear roll steer as a tuning device). But adding a panhard bar to a suspension that is trying its best to find a way to relieve some of its bind simply removes the lateral component from the already way too few ways that it can relieve the bind in the turns. Although I have not run the actual numbers (there are too many unmeasurable variables involved in this suspension-bind-to-resist-body-roll scenario), I would predict that a standard panhard bar added to a stock 4-link rear setup would increase, not decrease, the suspension bind during body roll already present in the stock 4-link setup.

 

Nick Holt

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The reason the bar worked on the 01 car is because I removed both upper arms and installed a short bar 11 inches long straight foreward in the center. I tried the long panhard bar without removing either upper arms and got no benefit , then I removed the right upper arm and it helped a little but the rear end would sway sideways too much and the pinion angle would change a lot because the rear end would rotate too much. Before I put the third link on this car I could only get about 1 3\4 inches of shock travel but after I put on the link with the same rear springs I got 4 1\2 inches of shock travel. The rear spring rates I used before the third link were 200 lr and 125 rr after the third link I had to go up on rates 225 lr and 200 rr to get 3 1\4 inches of shock travel. I think if these cars could use a third link and a panhard bar they could be made to compete with the leaf spring cars even without using weight jacks.

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Of course, this explanation is vastly oversimplified. One could write a book on the ins and outs of the metric 4-link rear suspension, but why???

For those of us that haven't been able to attend one of your seminars and might not understand why there are very few metric cars in Street Stock/Sportsman/Super Street but the ARTS/MARS Stock Cars/Limited Modifieds use them.

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Of course, this explanation is vastly oversimplified.  One could write a book on the ins and outs of the metric 4-link rear suspension, but why???

For those of us that haven't been able to attend one of your seminars and might not understand why there are very few metric cars in Street Stock/Sportsman/Super Street but the ARTS/MARS Stock Cars/Limited Modifieds use them.

 

Let's get one thing straight. I my seminars I NEVER advise anyone to cheat. But I do explain how a metric rear might be made to work if the rules would allow certain (rather easy to hide) modifications to the rear suspenson. Terry wisely and honorable elected to cheat openly. By that I mean he tried the modified rear setup and openly admitted to using it to Jack Sanderfur and was quite correctly dq'd for not submitting to tech.

 

To answer you question, ARTS allows certain modification in their rules and I'm sure none of them would even think of cheating up the rear control arm mounts or disabling one of the top control arms. LOL

 

Metrics (MARS and Limited Mods) work pretty well on tacky dirt because the rear end likes to get loose when the suspension starts to bind. It's when the track is dry/slick that they present the same sort of binding problems that are present in the asphalt metrics.

 

Nick Holt

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This thread answers a lot of questions I've had since I first found out about THR, 6 or 7 years ago, and started reading the rules. I knew that the metric and F-body cars were full frame and a 108" wb but I didn't really know what made them different. I know that the MARS Stock Cars allow weight jackers and the Limited Modifieds don't. I know the 4-link isn't optimum and wonder why if weight jackers are easy to install they aren't legal, at least for the rear, on the Limited Mods and asphalt metrics. Apparently, they aren’t the complete answer to making the metrics equal. I guess the question is do tracks want to make them legal and, if so, what is the most economical way to get them there.

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Putting weight jacks in the rear of a metric frame is easy. The reason most track won’t allow them, is when you get to the front. The stock mount shocks mount in the same place as where you would put the jack screw. I assume the rule is there to keep you running stock mount shocks and stock upper a-arms. Most tracks didn't allow after market uppers. Now there are a few companies that sell tubular a-arms that mount in the stock location, I believe they are legal in the IMCA stock car class. If you were allowed to move and manipulate the upper a-arm mounts you could get the front of the metrics closer to where you need them, i.e. caster, camber, roll center, etc....

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I would love to bring my CC Super Street up to test at THR some day with the 970's. I have weight jacks, 3 link and panhard bar. It is the only competitive metric car at CC. Atleast somebody at THR could compare and see how competitive one of these cars can be with modifications.

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I would love to bring my CC Super Street up to test at THR some day with the 970's. I have weight jacks, 3 link and panhard bar. It is the only competitive metric car at CC. Atleast somebody at THR could compare and see how competitive one of these cars can be with modifications.

 

Are you planning to come up for the Oct. 22 race? If so, any Thursday practice day would be a good time for you to practice and see what the car can do here. Let me know if you can come up, and I'll meet you there. We'll do some learning!

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Adding a panhard bar to a stock metric 4-link will cause a super bind, and not allow the car to roll.

 

The quick fix as already stated is to go to a single upper w/panhard bar. Although with some mechanical ingenuity, lots of creative welding (to hide from tech) a metric 4-link can be very good on a short track (1/4 to 3/8), did not have very good luck with the car at SAS. One of the cars I did this too has won 2 track championships in Odessa. The car did have weight jacks, and very specialized front spindles (it took about 12 hours each to modify them and look like factory stock).

 

That is the most information I will give, I may decide to race against you guys someday and want to keep some of my secrets.

 

On another note: you could always run the old k-frame chrysler.

 

Louis

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Oops, did not see the rest of the string before adding my comment on the panhard bar. Oh well,

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  • 2 weeks later...

Chase,

this is a great topic.

I too followed the adventures of Terry 01 street stock while he was trying to figure out his Metric Chassis.

I think the 3 link with a pan hard bar would put these cars in the right direction.

Nick please jump in if you know the answer to this.

I think the front roll center would be too high unless they were allowed to run Camero Spindles.

I am not even sure if that would correct the problem.

It would be great to see more of these metric cars run at the front.

Bryan

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Chase,

this is a great topic.

I too followed the adventures of Terry 01 street stock while he was trying to figure out his Metric Chassis.

I think the 3 link with a pan hard bar would put these cars in the right direction.

Nick please jump in if you know the answer to this.

I think the front roll center would be too high unless they were allowed to run Camero Spindles.

I am not even sure if that would correct the problem.

It would be great to see more of these metric cars run at the front.

Bryan

 

They can run different spindles and ball joints in the front now, so the rear is really the problem needing fixing, I think.

 

I sent a proposal to Jack for his consideration during the winter. Basically, it would allow for a 3-link rear suspension with these cars using the stock lowers, an aftermarket adjustable upper link, and a panhard bar. No weight jacks.

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the cost of the weight jacks is probably the cheapest thing to do to make a metric work,but on you proposal you left it out.why the other work to change the rear drastically but not the cheapest.and stock mount shocks is kind of a joke.the shocks that are stock mount cost way to much for the good ones,and mounting in a remote spot is nothing. dont use the answer that welding is required on the chassis.a welder is required for a cage....i dont see rules saying screw it together......

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the cost of the weight jacks is probably the cheapest thing to do to make a metric work,but on you proposal you left it out.why the other work to change the rear drastically but not the cheapest.and stock mount shocks is kind of a joke.the shocks that are stock mount cost way to much for the good ones,and mounting in a remote spot is nothing. dont use the answer that welding is required on the chassis.a welder is required for a cage....i dont see rules saying screw it together......

 

Johnny, I agree with everything you said. I left out weight jacks because I've always got the impression from Jack that he would not go in that direction with the street stocks. If he allowed them in the metric cars, I think the Camaros should get them as well. I have no beef whatsoever with weight jacks. I would just have to wonder what a significant change like that would do to an already low car count.

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Guest RandyBorlace

just because weight jacks are allowed doesn't mean they HAVE to be run , Frank's other son Adam has a nova with no weight jacks, and it's one of the best handling street stocks at the dirt track, sure you will have to go with remote mount shocks, but they are the same price as the ones that are harder to change , you don't have to jack up the car to change these. i think all the street stock/sportsman type cars need weight jacks, it's too easy to get a decent running sportsman metric car and run roadrunner all you have to do, is change springs, and put on manifolds.

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  • 4 weeks later...

I drive both a metric(my truck) and a leaf spring car(ss). My truck has weight jacks and a stock 4 link. I see the times at CCMS are identical, THR the truck .5 sec quicker. SAS I seem to remember being faster than the sportsmans. Thats with a 305 a ton less HP. I also feel like my truck is more stable on corner entry turns better in the center and is looser off.I have won with the car and not the truck yet this year. just my opinion dont know if all this rambling helps or not. I prefer to drive the truck. trying to help the four link guys might get you camoro guys beat.

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