superstock 3 link

[propit21]

ok here it goes, looking for suggestions or comments.
We run a prostock/superstock front clip car fab rear witha 3 link. We have been on two different setup in the last year because of rules. The first setup is an 3 link with a shorter LR arm about 15" or so with a longer RR about 20" or so.. This setup is with a long pullbar with a j-bar mounted on the pinion to the left side frame.
the other set up is an 3 link with equal 20" left and right rear arms. with an shot soild upperlink and an rear mounted panhard bar mounted to the house about even with the j-bar mount on the reverse side and mounted to the left side of the chassis.

Here are some of the questions... We run the same spring package with each which is LR-225 15" mounted on the front side of the axle, RR is a 200 13" mounted on top. For the longer link would you need to run a softer longer spring on the LR to promote easier chassi hike to make the cars get on the bars?

For rear shocks we run a LR 7/4 or 7/2 split valve shock and RR is a 4 or 5 straight valve shock. Because of running all soild links with the second set up would we need to go to a shock that allows weight transfer onto the LR since it doesn't want to hike the LR.

For the pull bar, j-bar, short trailing arm set up would you want it more like an modified set up for shock such as running a 7/4 or 7/2 to "keep it on the bars" traction?

we are looking for more drive off the corner mainly and i think we have been working on something almost in the wrong direction. if need more info i can provide if needed.Again mainly should we try the old school way of weight transfer in the chassis though the use of shocks,springs, and % or would the new school way of "keeping it on the Bars" way with mechanical drive better. Any thoughts or comment are welcome.

[Dirtrunner35]

Need more info on car, rear bar angles, tires and pressures, % , everything. Hard to say with what info you gave.

[charcoal01]

Looks like the car needs to be freer on entry and allowed to rotate the center better. The faster in and through the center the car is, the feeling of not enough forward bite won't be as noticeable. But that's just my opinion.

[charcoal01]

The other question is after how much down travel does the lr spring lose seat pressure? Bar angle on 3 links has more to do with how quickly the car creates drive off the corner, you may need to run more angle with the longer bar as it reacts slower.

If you go to a longer softer spring the driver is going to have to adjust his corner entry, staying on the gas longer and getting on the brakes sooner as the car will be much tighter off the gas. In other words, arch the corner more and trail brake to keep the car up on the bars on the lr.

[DaveBauerSS6]

And Dave, what is your answer??

[propit21]

answer
after the spring come off the upper bucket it was another 1" of down travel befor the chain kicks in.

questions
how much freer does entry need to be? and how should we achive this without hurting mid corner and exit?

so as far as spring in the LR is concern its the bar angle creating foward drive? Once you are off the spring bucket there should be very little weight on that corner, are you using the shock at that time to do the work of the spring? How do you achive wieght tranfer with a 7/2 on the LR? must you run alot of LR wheel wieght and bite in the car?

[4bangerhotrod]

i say put a swingarm on the LR, mount the spring on the swingarm on a eliminator run a 250, 300 or 350lb spring on the swingarm and put some angle in the swingarm about 15* or so at ride height and with the solid link run the 250 or 300lb LR so you can preload, an add about 100lb more lr with the solid link, a 7-2 shock or get a 8-2 for the LR and get a 3-5 for the RR when it slicks off. what springs and shocks you got on the front of that beast. and do you have to run a panhard bar for the second setup. if not leave the J-bar on an if you do could you get a longer bar and mount it like a rayburn, right side chassis to left side of housing about half way between center an hub on left side of housing.
thanks,
4bangerhotrod

[DaveBauerSS6]

No swingarms allowed in the second setup.
Must run panhard behind rear in second setup.

[propit21]

can not run swing arm on either set up sorry, and must run rear mounted panhard bar with soild upper link. front spring LF850 RF 925.

I may be missing something here so am going to ask, how does a high compression shock help the left rear (7/2 or 8/2). from what i ve have read, told , and understand wouldn't you want weight for the most part to transfer from the RF to the LR pretty quickly for a slick type track. so wouldn't that mean to run a lower compression shock on the LR and some type of easy up on the RF. Let the car turn with the LF tire and use equal traction on both rear tires.

[Dirtrunner35]

Some very great reading, a high gas compression on the left rear will help it on exit for lr bite, keeping it or getting it up on the bars faster.

Stated simply, I use shocks to alter/adjust/change a condition known as, "Instantaneous, Dynamic, Diagonal" - hereinafter refered to as "IDD"


Picture a car sitting on four wheel scales. This car has absolutely equal weight distribution, so all four wheels weigh exactly the same.

Now, if you were to push down on the exact center of this car, all four wheel scales would increase equally.....everybody agree?

If I were to add shocks to the RF and LR that had high - or higher compression values, and I pushed down on the center of the car, what would happen????

That's right....The RF and LR scales would show momentary increases over the other two scales due to the resistance of the two shocks, but everything would even itself back out again after the shocks bled down, and all four wheels would be equal in weight again......OKAY???

What happened here was a change in the IDD. For just an instant, there was more diagonal - or crossweight - with the RF and LR momentarily being more heavily loaded than the other two wheels.

But, once the shocks bled down, the setup returned to the equal-wheel-weights setup.

Now, go the opposite way.....lift slightly on the car.

All four wheel scales should show equal reduction of weight on all four wheels.

Add shocks with more REBOUND to the RF and LR, then lift again.

The RF and LR scales should show a momentary, increased reduction of weight over the other two scales until the shocks allow the wheels to go into full droop.

In this case, we have, momentarily, reduced the diagonal - or crossweight - for an instant.....

......which explains - for those of you who have read the Penske shocks setup manual - the suggestion to set the car up with a slight push on turn entry, dialing it out with LR rebound.

LR rebound induces a momentary reduction of crossweight upon turn entry, but allows the suspension to return to its original setup for turn exit.....effectively giving you one diagonal - or crossweight - for turn entry and a different one for turn exit.


With the right shocks, you could actually instantaneously DECREASE the diagonal or crossweight for turn entry, and INCREASE it for turn exit - or vice-versa.

The above is an over-simplified example of how it SHOULD work, and as we all know, nothing in racing is really "simple."

But, if you can get the concept of "controlling" body roll or weight transfer out of your mind, and visualize instantaneously - and momentarily - increasing or decreasing the diagonal or crossweight for better turn entry or exit, and you SHOULD begin to grasp the concept of shock tuning....

....and, by the time the car rolls into your pit stall, you'll have a pretty good idea of what sort of change you'll want to make without needing to dig out a chart.

[propit21]

i enjoy that reading, it really makes you think. To add a few questions to that.

There are 4 shocks on a car not 2 shocks, so how then must you adjust the LF and RR shock if you take weight transfer out of your head?

isn't crossweight a form of weight transfer to gain LR "bite or drive"?

Why is it the new trend to run a shock such as an 8/2 or 7/2 on the LR which have very little rebound control, whould it take out crossweight on turn entry as brakes are applied there for making it looser?


i love reading and learning this stuff and what people know about the tech side of race car set up any info is appricated.

On to what we have maybe learned or what we are trying to achive. First set up is at least 20" trailing arms, max 20" soild upper link, Min 20" rear mounted panhard bar. Second setup LR trailing are 15" RR 20", long spring pullbar for upper link, and a j-bar.
What we have found so far between the two setups are that you can set them up about the same with almost same angles and springs and shocks and be just ok. Now here is our thinking about this. Yes for the longer arms you are going to need more LR static angle is the trailing arm if you are running the soild upper link, the car will not want to climb up on the bars if not. Second if you don't add static angle in the LR trailing arm you can try and promote hike with a taller softer spring on the LR to get bound up energy to push the chassis up and arm down.
Now what are people thoughts on this if you leave the longer arms with a soild upperlink in with a rear mounted panhard bar in, and you don't run alot of angle in the LR to gain foward bite you need to look into weight transfer with shocks and ballast alot more. easy up front shocks and tie down rear shocks, ballast moved foward over the rear end to get wieght to transfer foward and back in the car. Need to run a good amount of LR bite in the car and cross can stay about the same. Do people agree with this or our we full of it. Or should we try and get the car to come up onto the bars with stiff LR shock, more LR bar angle, and taller softer LR spring and set the rest of the corners as needed for the set up?

[Dirtrunner35]

You have alot of stuff with 2 setups . What is wrong with the car ??

A higher compression GAS shock on the left rear, will help the car stay up on the bars on turn entry.

If you LR spring is coming off the spring cup, at that time it doesn't matter what your static cross weight was. A taller softer spring may or may not help, depends on what the car needs.

THAT EXAMPLE
The RF and LR scales would show momentary INCREASES over the other two scales due to the RESISTANCE of the two shocks, but everything would even itself back out again after the shocks bled down, and all four wheels would be equal in weight again......OKAY Once again depends on what your car needs.

More good reading
Total weight transfer, CGH, lateral acceleration and track width. Note that this is TOTAL transfer. This transfer happens no matter what spring, bar, shock, RC combination is used. What the springs, bars, shocks, RC do control is where the weight is transfered.

[sj valley dave]

The car in questions runs tracks that have 2 different rules packages...Package 1 is his home track rules and rules package 2 is when he comes to California and runs here....I saw the car run once and it looked tight going in which made it snap when it finally did rotate and cause it to be "loose" coming off...I know with our 4 bar DLM, you get the entry nice and free, let the car rotate, keep the tires under it and the exit is 90% taken care of...

[Dirtrunner35]

So it's a tight/loose problem. Car needs loosened ?

[propit21]

dave what race was that, SMS? yes it was very tight there and we know that since then made some good adjustments but still off alittle. i do believe it is all starting at corner entry and other problems are because of it.

[sj valley dave]

Yes it was the Santa Maria race...I know with our 4 link DLM, when you are talking about tight/loose going in and people talk about springs, one thing a lot don't bring up is how are you going into the turn...If you've 'set" the car and going in on the gas, the changes are totally different than going in off the throttle, more rolling in waiting for it to roate befoore you pick it back up again...Before we got our guy to set the car early and go in under throttle, we went softer on LF spring and that really helped...we only ran a 450/400 combo across the front...It would turn in wherever we went at that point...