Guys, I'm trying to wrap my head around some drag race suspension theory.

I get the idea of front drag shocks, such as a '90/10', which extends more easily to allow the front end to rise (for weight transfer to the rear) but compresses harder to keep the front end up longer.

But I puzzle some over rear shocks. I thought I'd been told that they are more the opposite; they are softer on compression but harder on rebound (or extension). True?

I've watched slow motion videos of cars launching. I see the slicks wrap up and flatten out against the pavement, increasing the contact patch.
But at once, it looks like the distance between the face of the tread and the wheel rim decreases, as you might expect, from the tire buckling.

Does that not then decrease the per-square-inch pressure that is applied by the tire to the pavement (at least for that millisecond until gravity and the rear springs can react and take up the 'space')?

Would you want then the rear shocks to be softer on extension, to allow the rear springs to react quicker, to push down on that compressed slick sooner?

May I assume then that is why I've been told that the rear suspension too should be loose?

My S10 has all stock suspension with leaf springs, save for the Cal-Tracs. I've got over 100 lbs. of ballast in the back.
My horsepower does not exceed 350 I'm sure.

The goal here is to insure good, consistent traction with less ballast. I've experienced the results of dead-hooking on every pass, and I like it alot. ;^)

From now on, I'm buying new slicks every spring.
I'll probably install some sort of drag shocks on the front, and see what I can do to loosen up the movement some. I'm not ready to invest in new springs.

I've raced for 8 seasons now, and some of these things I should 'already know'..... but often if I act like a dummy I learn more.

Check out "Compcams Dave Morgans chassis manual" available at Amazon for 57.49. best money you will ever spend on your chassis. Very involved reading.

Shocks, there is no simple answer for all. Two different cars can have almost same suspension, weight etc and require different shock settings. Many reasons, too much to list here but I can give you some things to think about.

Four link settings can change if it lifts front of car up more (wheelie) or rear of car (plant tires) too much of either one will not work well. The further back and up the IC is in relation to center of Gravity the more it will work the shocks at the hit also making shocks more critical. The four link is going to push car forward and up, where it pushes up depends on weight, center of gravity, how four link is set up and other factors.

Ladder bars try to lift rear of car up planting tire and you need good shocks to control it. If rear shocks top out in any suspension it will temporarily unload rear tires. With ladder bars and even some traction bars you need good shocks to control that extension. Also with a four link that has IC too far back and up. Caltracs act similar to ladder or traction bars.

When a four link is set up right there is not a whole lot of rear shock travel but it is still very important for good shocks.

Loose front suspension is good in low powered cars to help transfer weight to rear tires, as you go up in horsepower you need less weight transfer and travel to keep front end under control.

Video the car and watch closely what it is doing. The higher powered cars will have less shock travel front and rear.

One strange exception is the Radial tire class, I have seen some who appear to have the IC way back and up and probably setting shock extension very tight, by mid track the back of the car is way up there. They are not setting it up as has been done traditionally but it appears to be working. They are also doing other things to bring in the power exactly where they want it and that gives them a little more flexibility than some have.

Another factor is the rear tire and how it handles the hit.

Factory cars are set up for smooth ride and to handle rough roads etc. They are not set up to handle hard hits from standing stop and wheelies.

I have Dave Morgans Chassis book, Rick Jones Chassis book and Jerry Bickels book. All are good but I would not say any one of them it the only one to get. There is good information in all three for sure but they have different ways of looking at it. Also I think it is the Rick Jones book that seems to be all about Pro Stock style chassis and not too much general.

The Dave Morgan book is an older book and more general. Some things have changed since it was written. I still recommend it though.

quote:

Originally posted by Curly1:
When a four link is set up right there is not a whole lot of rear shock travel but it is still very important for good shocks.

^^^^^^ X2

quote:

Originally posted by markemark:

quote:

Originally posted by Curly1:
When a four link is set up right there is not a whole lot of rear shock travel but it is still very important for good shocks.

^^^^^^ X2

On a bad run in Pro Mod the shaft moves in the main body seventy inches per second, on a good run thirty. With dampers it's velocity vs hysteresis (slack). A high technology damper builds force in extreme environments, when a low technology damper develops slack.

This is the highest technology there is. Formula One racing technology.

Look at your front suspension. Measure to the fenderwell then jack the truck under the crossmember until the wheel just begins to leave the ground and measure again. That is how much travel your front end has. Check to see if there are rubber bumpers under the upper control arms, removing them will give you more travel. Since your truck is pretty old I would remove the control arms and possibly replace the bushings. What you want to do is make the control arms just move freely. With factory bushings they have stiction as the inner tube bites into the mount and they pivot twisting the rubber. What you want is the arm to pivot on the shaft or bolt freely with no stiction. You can modify the factory bushings or but Afco or Global West.
you say you have Cal Tracs so I'm guessing the rear spring bushings are good and they move freely.

Ok guys lets not get carried away with 4link and coilovers op has leaf springs. Dave morgan book has good basic information on shock spring relationship.Spring holds up car shock controls movement.

quote:

Originally posted by Mike Rietow:

quote:

Originally posted by markemark:

quote:

Originally posted by Curly1:
When a four link is set up right there is not a whole lot of rear shock travel but it is still very important for good shocks.

^^^^^^ X2

On a bad run in Pro Mod the shaft moves in the main body seventy inches per second, on a good run thirty. With dampers it's velocity vs hysteresis (slack). A high technology damper builds force in extreme environments, when a low technology damper develops slack.

This is the highest technology there is. Formula One racing technology.

What do the ohlins ttx36 sell for?

I cannot find anything online, nor any drag shock dealers online.

I know the Menscer 4 way adjustable are $5000/pr.

Wow!! Guy comes on with a 350hp S10 pickup and we're off to the races with 4 links and Promod shocks!
Bad Nusz, you shouldn't need new slicks every year unless you're putting over 200 passes or more on them a year. If the springs on the frt. are stiff they are not compressing when at rest so there is no stored energy for weight transfer. If the springs are holding the suspension up then there is very little front end travel. The shock idea is good but they won't be able to do their job if the front doesn't have enough travel. Cutting or heating the springs doesn't accomplish the goal as you want the spring to have stored energy.

What eman said. Give the op a break hes trying to learn. We all have to start somewhere.

quote:

Originally posted by vetman:
Ok guys lets not get carried away with 4link and coilovers op has leaf springs. Dave morgan book has good basic information on shock spring relationship.Spring holds up car shock controls movement.

I sort of agree with that the reason I mentioned all of that is to point out some of the variables. And to point out there may not be just a simple answer to a simple question. My way of thinking you have to figure out what it is doing then figure out how it works and make changes until it performs like it is supposed to.

The same principles apply for 4 link ,leaf spring or ladder bar suspension systems when it comes tuning dampers / shocks. I've never seen a book with extensive instruction. 20 years ago the majority of opinions were shocks don't matter.

I was standing at payout and I guy I raced with asked if he could look under my car, I said sure. He climbs out from under the car and professes I had way too much shock. I thought that was pretty funny but that was how it was back then. I had a set of Koni doubles Jerry Bickle valved on my street car. That's a pretty decent product Koni double, even today one of the better, over the counter.

Eman and vetman; thank you, lol.
Actually, I thank all of you for your kind and thoughtful responses. I appreciate every one.

Most of you are pretty much out of my league, but one day when I progress enough to run with the big dogs, I'll be better positioned to use that knowledge of 4-links and such.
In a year or two I'll be better able to afford a different machine, and it may in fact be back-halfed already.

To me, nothing goes to waste. Nerd that I am, I copy and past all of your responses to my racing journal, so I can never lose the info.

I get what you're saying about the slicks, Eman. I do in fact put on many passes throughout the season, racing on Saturday evenings and then double-entering on Sunday. We get three time trials per event at my 'home' track, and even a long test & tune period for no extra charge on Saturdays.

I do need new rear skins this season. Last season, I ran a pair of Hoosiers that hooked until the cords showed through, about mid-summer. Then I ran another pair of used Hoosiers that I had on hand. Though they had plenty of meat left on them, I think they were kindof 'baked out' already and probably cost me a few losses due to slight spin.

On a pro-rata basis, I'm not losing much by retiring a set of slicks at the end of the season. I need a better set of spare slicks anyway, or maybe some new kid at my track could use a free, used pair to get them in the game.

Lol, I've lost too many races in the semi-finals or some money round to fret much about the added cost. ;^)

Thanks all especially for the recommended reading. I do already have a copy of "Door Slammers: The Chassis Book" by Dave Morgan, and I've cracked it open again.

I also own and recommend "Drag Race Chassis and Suspension", an HPBooks volume by Wayne Scraba c.2007.

My favorite though is probably "How to Hook and Launch: Traction Mods for Street & Strip" by D ick Miller, c.2012.

I'm a book slut, so I'm ordering in the "Rick Jones' Chassis Tuning Guide" and probably Jerry Bickel's book as well. Lol, I wish there were .PDF versions of them.....

I don't have much of a pit crew, so this winter I'm putting a camera mount underneath the back of my truck.

Thanks again guys,
Have a winning season!
Troy

quote:

Originally posted by vetman:
What eman said. Give the op a break hes trying to learn. We all have to start somewhere.

You're in Des Moines, vetman? Cool; you're about dead center in the middle of all six tracks in Iowa. Which is your favorite?

BTW, here is I think a pretty neat YouTube vid that shows some launches, with a critique of each.

https://www.youtube.com/watch?v=vm5cA6xhsk0



What is "Corona virus" anyway? Is it anything like "Three-Two flu"??

Camera mount a great plan. As far as tracks I go to Eddyville to test. Good safe well prepped well run track. Dont know anything about Onawa i29 a no CFR a no Earlville is ok 1/4 only. Checkout Qa1s stocker shocks. They list one to fit your truck.

Bad Nusz, What rear is under your truck? I've got an S10 like yours in the shop right now. Making a Sportsman ride out of it. Total low buck used parts make everything deal.

quote:

Originally posted by Eman:
Bad Nusz, What rear is under your truck? I've got an S10 like yours in the shop right now. Making a Sportsman ride out of it. Total low buck used parts make everything deal.

I had a local mechanic narrow a Ford 9" for me and helped me measure it for Moser 31-spline axles. The bolt pattern on the axles I ordered is the standard 4 3/4" GM bolt pattern, but I asked for 1/2" studs.

The rear end housing I spotted in a salvage yard, and I think it came from a pickup truck. I noticed that it had a nodular-iron center section, so I jumped on it!
Fortunately, the tubes on it were of the non-tapered type, which I'm told is easier to narrow.

The brake kit I had ordered from Right Stuff, with new, GM locking-style "Caddy" calipers, but that was a big mistake. I replaced the locking calipers with 2" bore GM-Metric-style calipers from Speedway Motors. They seem to balance nicely with the stock, 2.5" "metric" front calipers.

I see Quick Performance in Ames, Iowa still lists a complete housing and axle package for the S10 on their website, with spring perches already welded on. Base price is $680, but you of course will need the center section too.

The driveshaft I had made locally, with 1350-series U-joints put in right away.

Have you installed the engine yet?
Cheers,
Troy

I know a guy who runs a small tire 9 inch wide I think and his car hooks and works well but he only gets one season out of them if he is lucky. If he had a larger tire it would probably last longer but he is really working sidewalls on it and reaction times and traction starts to go away.

Also tires may last longer if chassis is not right, hitting it too hard and unloading it.

I agree with you getting new tires every year and continue to work on chassis to get it to work right all of the time. With right chassis, shocks and tires you may get two seasons out of a set. But you are not there yet. No problem you realize there is room for improvement, asking questions and working on it.

Once again to me it all comes down with any car 1. To figure out what it is doing (Video?) 2. To learn how it works. 3. Then to make changes to get it right.