Tires

[jl222]

Bob,  I too have a very adjustable 4 link and will be using a long panhard bar (to start).  I have elected to start with 300# springs but will have 350# if need stiffer..

As to weight, I do plan on a 52% rear, 48% front and will have 4 provisions for adding weight low on the chassis.

If the pic comes out... at the purple arrows is where I can add weight.



Charles

 The 222 camaro [bvillercr and my car] and Alston drag race chassis came with 88lb springs and Alston and Prochassis who built the car
didn't like us going to the 112lb. Of course spring rate depends on were the coil overs are mounted.
  As to weight distribution,one has to think about Fast freddy,he has got to be over 65- 35% plus the added downforce of the wing.


                                 JL222

[robfrey]

Okay, 88lb springs? How do you get enough preload on them? That sound like drag racing stuff to me. No that there's anything wrong with that (Sienfeld). I been trying to design around using road race stuff. I got so much preload in my 1200lbs springs just to get back up to ride height that I thought I was going to wear out my spanner wrench. I designed the car with 3 inches of travel and it sits one inch into travel when you take it off the jackstands. This goes for front and rear but I only have 550lb springs in the front.
I can imagine some day that we will use a wing that will generate another 1500 lbs and at that rate we will squat the car another .6" in the rear so we have to be careful. My design work though is mostly geared around Maxton and not the salt. I feel we need these rates at Maxton as the bumps are so harsh that if we used anything softer we will be bottoming on the concrete transitions.

As far as the 400lb springs, I don't feel you will get a buckboard effect as long as you have the proper dampening.

That being said, can we get back to the original topic on this thread and talk some more about tires. Does anybody know when the new 450 mph Goodyears are going to be available and what sizes they will be offered?

[Cajun Kid]

Tires ?  I just need to know what kind of tires I can use on the Stude for a max speed rating of 250mph,,

The shortest rear tire I can use would be 26"  the tallest  would be 28"  to keep my ride height where I plan.

My goal is 220 to 225 mph.  (as I think current record is 217.xxx)

Charles

[bvillercr]

Robfrey, suspension is directly related to how your tires are affected.  Too stiff and you will spin your tires right off, ask Fred. 

Bob I got severly sideways at El Mirage and had no pendulum effect, just the normal steering to correct the problem.

[Rex Schimmer]

Robfrey,
I would like to know your definition of "preload". I think of preload to be when you have the shock loaded and you have turned the adjustment collar past the point that achieves your desired ride height and the shock is fully extended such that any additional raising of the spring collar only compresses the spring and does not raise the car because the shock is fully extended. When this is done your suspension will need to be loaded until this preload is over come and then it will begin to deflect. If this is what you are doing then you definitely have a problem. This makes the suspension very stiff and skidish. As John said we do not know what your mounting system for the rear shocks is so we cannot determine the what the wheel rate is but I certainly agree with John that 1200 lb/inch springs certainly seem very high for a live rear end suspension. If you are truly "preloading" the suspension to be able to carry the aero loads from your wing then I would certainly suggest going to longer shocks and springs preferably softer. I assume that you probably have the standard 4 link rear locator suspension, are you running any anti squat or anti dive in the four bar set up? By this I mean are the bars parallel to each other, top and bottom in side view, or do the angle together with an imaginary point that their center lines intersect? This set up makes the rear end housing into a very stiff anti roll bar as the rear end is now rotating around the point of convervence of the 4 bars which will work for a bump that both wheels hit, but if only one hits the bump then the bars are trying to twist the rear end housing, just like a big anti roll bar. I am sure that your rear end is capable of some amount of deflection of one wheel but this is only due to the deflection of the bars, the heim joints and their mounting brackets. One way to still have some anti dive or anti squat is to only run one bar on one side of the rear end and two on the other, typically the single bar side is mounted to the horizontal center line of the axle on its side. If you think that you need an anti roll bar then I would suggest installing one that is designed specifically to act as an anti roll bar and this can provide your with the ability to statically transfer weight between the rear tires.

Rex

[interested bystander]

Charles, not to sound like a smarty, but re: your tire search, try (and I don't know if your computer is set up the same) the little panel that, on my machine, is in the upper right corner with GOOGLE in it.
 
Then do a search for, for instance, GOODYEAR, MICKEY THOMPSON, and , maybe DUNLOP.

Let us know what YOU found regards your tire quest.

[robfrey]

Charles, My suspension is not topped out if that is what you are asking. When we sit the car down onto its wheels, the car sits into travel 1". I did need to preload the springs in order to keep the car from bottoming under its own weight.
Everyone keep saying we are way too stiff but the car used to run all the time with no suspension. I don't believe Fast Freddie's car has any suspension. To bounce on the suspension, it feels about right to me. I wanted to make it much softer but the the safety steward of the team said "no way". He has since left the team so he is no longer an issue
The bottom two bars of the four link are "X"ed to provide lateral location for the rearend (this is also the roll center) and also act like a giant sway bay. I am not concerned about one hitting a bump and the other not. I am concerned that if the car starts fish tailing that we will not get a lot of body roll.
Without data on the rear wing, I have absolutely no idea how much down force it will make at 350mph. I would like to develop at least 1500lbs. That will compress the rear suspension another .6
Remember, this suspension was designed to be able handle 300 mph at Maxton. Those concrete transitions are KILLER.
I don't really know if I have a problem or not at this stage. I was not in the car at 284mph to feel what was going on. I was able to break the tires loose on my licensing runs at lower speeds if I tried but I was running over 1000whp and I don't know what a really good traction car feels like to compare. How much traction can I expect. We can make over 1800whp and I can increase from 1000 to 1800 very gradually with a boost controller. We know the car goes 270mph with 1070whp with no issues. I know that we need a more efficient rear wing.

[Rex Schimmer]

robfrey,
Certainly sounds like you do not meet my criterial for "preload" of the suspension, which is very good, and it also sounds like your suspension actually does travel, also good. With the welding of the "X" across the lower bars you have made the rear suspension a single swing arm arrangement which will highly resist any type of one wheel bump or any roll of the chassis. Again since your suspension is "active" i.e. it does not need to over come any "preload" (my definition) I would certainly suggest that you use the old tye wrap on the shock rod to estimate the down force of your wing. This might not work at Maxon if the track is very bumpy, which most old air strips are, but at Bonneville you could probably assume that the maximum shock deflection was due to the down force of the wing. From this information you should pretty easily be able to come up with number for the amount of down force. Still think that 1200 # springs are pretty stout but you may not be able to go to something much lighter if you don't have some pretty long shocks. Any chance of a picture of your rear suspension??

Rex

[robfrey]

You can see that even if we went with a longer shock, the rear will only come down so far as the brackets will hit under slung portion of the frame.
I could still go with a softer spring and just use the spanner wrenches to get the right preload. I always use big flat thrust bearings between the spring and the retaining nut. This will make it a bit easier.

Thanks for the compliments on the Pontiac.

[Rex Schimmer]

Rob,
When you jack up you car on the frame until the springs are unloaded and then set it back down how much do the springs compress? Obviously going to a lighter spring on the shock length you have could certainly lead to coil bind on the lighter spring, which is obviously the same as a solid suspension. This also needs to be taken into account with the potential aero load from your wing. Lots of intersting things to consider and it certainly looks like you have a very potent car, already looking forward to seeing you next year at Bonneville.

Rex

[robfrey]

Hi Rex,
The rear suspension sits into the travel 1.0 inch when we let the car down off the jack. We then have another 1 " of travel before contacting the bump stops. Thanks for the compliments but we sure have a lot to learn.

Rob

[dart4forte]

I am currently building a 64 Dart to begin my journey into land speed racing. My current plan after I have observed as a spectator is to run the car first in the 130 MPH moving later to 150 MPH. What would be the recommended tires (15") to run at thoise speeds?

[Cajun Kid]

Dart,  H Rated Tires will get you by up to 150MPH. So if you are using 15 inch wheels you will have plenty of tire choices.  If you plan on going any faster, I would try to start out with Z rated or better (I learned the hard way, bought H and had to upgrade to Z)  Only problem with Z and higher rated tires is they do not have as many size choices in 15" ... if you need taller than 26".

Good Luck and Happy Thanksgiving

Charles

[robfrey]

Can we get some info on max loading of these tires? We are concerned about wing down force + vehicle weight exceeding the loading limits.

[dart4forte]

Dart,  H Rated Tires will get you by up to 150MPH. So if you are using 15 inch wheels you will have plenty of tire choices.  If you plan on going any faster, I would try to start out with Z rated or better (I learned the hard way, bought H and had to upgrade to Z)  Only problem with Z and higher rated tires is they do not have as many size choices in 15" ... if you need taller than 26".

Good Luck and Happy Thanksgiving

Charles

So, would drag radials work?