Road racing suspension

[Spray-Bomb]

Hey guys, Im planning on building a full chassis for my truck Killer

The plan is road race driver that is powered by a twin turbo duramax

I want this thing to ride about 2 to 3 inches off the ground to the door (truck will be doored)

Most likely will be on 20" wheels & whatever tire sizes & have to run to make em work (will go smaller wheels if needed)

What my questions as of right now are: #1 would I be better off building the frame from round tubing or something like 2x3 rectangular tubing ???

And #2 I want to run IRS & an improved IFS, so what would yall suggest to run front & rear... Mustang II, C4, ??? in the front & C4, explorer, Jag, ??? in the rear

I want this thing to be safe & handle great, so hit me with what you got

Thanks, Matt

[Shane]

Just curious, but have you finished any of your other projects yet?

[Musclerodz]

you will definitely have to go smaller if you plan to track it. At least 18".

[Painter D]

Originally Posted by Shane

Just curious, but have you finished any of your other projects yet?

x2

[abadsvt]

What is everyones opinion on using a satchel link for the rear suspension? You get a low RC for a 4 link and then get a properly sized sway bar or do you guys think a watts link is better because of the fixed RC even though its a couple inches higher up? I think with 20" wheels, just guessing here, you might get a RC thats 5" +or- with a satchel link. I am looking for opinions. Trying to expand my suspension knowledge

[Twisted Minis]

I would probably run 2x4 for the frame. If you don't build it right from round tube it may end up weaker. But if you want to go that route, it will just be a bit more labor intensive.

As far as suspension, for IRS I would not run Jaguar if you want it to handle. It uses the axle shaft as a control arm. It can get sloppy when the u-joints and bushings wear out, and any axle failure would be devastating, especially in a corner. If you blow a U-joint, you loose your upper control arm.

For the front, I don't necessarily like MII that much. I would go with a different kit, or something scratch built that is meant to do what you want.


I am in the middle of a similar project, idea wise. Race worthy suspension, big brakes, scratch built spindles and front suspension, small block sunk into the firewall, narrowed 9" with parallel 4-link and a low mounted panhard.

[PBFAB.COM]

I would have to recommend a link style rear set-up with a straight axle, preferrably 9 inch. You would be putting down gobs of torque with the TT diesel, and without investing a large sum of money into an IRS... it won't hold up long. A properly designed rear link set-up and a straight axle can be made to handle just as well, if not better.

[Spray-Bomb]

Ok, so properly designed strait axle set up in the rear will work
What style link set up would you recommend

Im not bent on using any one type of suspension, I just want it to handle really well

For the front: why not a Mustang II ??? What about a C4 (too light duty for the diesel ???) If not one of those two am I better off designing my own IFS for it ???

Thanks, Matt

[Twisted Minis]

Originally Posted by Spray-Bomb

Ok, so properly designed strait axle set up in the rear will work
What style link set up would you recommend

Im not bent on using any one type of suspension, I just want it to handle really well

For the front: why not a Mustang II ??? What about a C4 (too light duty for the diesel ???) If not one of those two am I better off designing my own IFS for it ???

Thanks, Matt

I have no experience with C4 suspension, so I can't comment on that. But I feel MII would be too light duty for your application. I think something based on a more HD spindle and control arm design would be best. Something with a decent aftermarket for big brakes. So maybe start with the standard C10 McGaughy's spindle and big brake kit, and build your own suspension based on that.

Or what someone else on here did, was get a PB cross member meant to weld to a scratch built frame.

[Spray-Bomb]

Originally Posted by Twisted Minis

I have no experience with C4 suspension, so I can't comment on that. But I feel MII would be too light duty for your application. I think something based on a more HD spindle and control arm design would be best. Something with a decent aftermarket for big brakes. So maybe start with the standard C10 McGaughy's spindle and big brake kit, and build your own suspension based on that.

Or what someone else on here did, was get a PB cross member meant to weld to a scratch built frame.

Thanks

I have thought about the PB DM, & I need to call Nate & see what he has to say about the front

[joeys66pickup]

this would be a *****in idea! truck that outcorners a car, that is something i would indeed like to see...should be interesting

[texastrendz]

thats a heavy motor if i recall, and big, would be hard to get it to do what you want it to do no matter what. best of luck to you and your wallet. going to be pricey build but nothing is impossible. once again good luck on it.

shane are they ever finished, i see your point, he has like fifty trucks he is working on.

[Twisted Minis]

I would prefer a Satchell link over the traditional Watt's link seen today. If you are looking for a race type setup, I would run adjustable mounts, no matter what kind of link setup you use. Because you realistically won't get it right the first time, no matter how many numbers you crunch. Nothing works better than real world driving.

I think that a frame mounted Watt's link would be cool to see more often. It's more common in race cars, and it will give you a roll center that is adjustable, and doesn't change throughout your travel. Here is a frame mounted Watt's link (notice the pivot is on the frame and not the axle).


With an adjustable mount, this could probably be one of the most easily tuned suspension setups. However any time you move the central pivot, your side to side arch will change.

I am still a fan of an adjustable parallel 4-link and an adjustable panhard bar. It's simple to set up, and when you adjust it, your wheel arc does not change. I am also a fan of less moving parts, because it's simple and reliable. I also like it because a lot of people seem to be afraid of the panhard bar these days.

[abadsvt]

Originally Posted by Twisted Minis

I would prefer a Satchell link over the traditional Watt's link seen today. If you are looking for a race type setup, I would run adjustable mounts, no matter what kind of link setup you use. Because you realistically won't get it right the first time, no matter how many numbers you crunch. Nothing works better than real world driving.

I think that a frame mounted Watt's link would be cool to see more often. It's more common in race cars, and it will give you a roll center that is adjustable, and doesn't change throughout your travel. Here is a frame mounted Watt's link (notice the pivot is on the frame and not the axle).


With an adjustable mount, this could probably be one of the most easily tuned suspension setups. However any time you move the central pivot, your side to side arch will change.

I am still a fan of an adjustable parallel 4-link and an adjustable panhard bar. It's simple to set up, and when you adjust it, your wheel arc does not change. I am also a fan of less moving parts, because it's simple and reliable. I also like it because a lot of people seem to be afraid of the panhard bar these days.

THats a pretty sweet setup! Now isn't a big part of an ideal rear suspension to have the lowest RC possible. I understand the advantages from having a fixed RC but still wouldn't you a lower RC be more benificial? Or does an inch or two not really have a big difference? Now with IRS you get a much lower RC so wouldn't that be even better? I know they can only handle so much power but I don't think you need anything that makes that much power because it would more difficult to drive or even race. Now like i mentioned before i am newbie and learn by asking questions like this. Thanks for taking the time to answer my questions.

Josh

[AceX]

I'm with Seth and Nate on this one. A solid axle will hold up better to that motor and with a proper and adjustable link set-up in the rear, you should be able to dial in the suspension to your liking.

The front, I've done some research on, and what I believe to be the best system for this type of situation is a Dropmember with coil-overs and PB control arms. Adding some HUGE brakes will also help, but look for a set with a two-piece rotor like Wilwood, Brembo, and AP Racing. This will keep the unsprung weight to a minimum which will help greatly. Also, finding lightweight wheels that are just barely large enough to fit over the brakes will be essential.

EDIT: The ultimate mod you can do is the driver mod, this means getting out there and driving, hard. Learning how the truck will handle, where its limits are, and more importantly, where your limits are.

[Twisted Minis]

It's really hard to say, because every type of link setup is going to act different. They way you build your setup really depends on what you want to do with it. What kind of driving you are going to do.

A few inches does make a big difference in the way the car feels, as far as roll center location. But adjustability is good, because you can tune your suspension for different tracks.

The thing with roll center, is that there is kind of a happy medium. While a low roll center is good, too low is not necessarily. The same as too high would not be good either. There is a certain point that it becomes too drastic. And the same as most aspects of the suspension system, there is no written formula, only theories that are known to work. So there is no number for a roll center that is too low. It is dependent on so many other aspects of the car and the suspension.

One thing to remember, is that the lower your roll center, the more top heavy your vehicle will feel, and the more a sway bar seems necessary.

When I build a link setup I look at what kind of driving the owner wants to do, what kind of power they have (or will have), I look at where the vehicles center of gravity is (the estimated COG, I do not have the technology to pinpoint it), I look at the front suspension design, and where it's roll center lies, and design the suspension based on that.

For my personal preference (my own vehicles) I like a fairly neutral driver. Basically, it would excel at nothing, and do okay with everything. I like a link setup that doesn't lift or squat heavily under acceleration, which means it won't have the most traction off the line, but it will drive smooth when I am cruising, and do alright when I want to get on it. I find my front roll center at my ride height, and try to match the rear roll center to the same height, to achieve a more balanced roll center for the entire vehicle. I am more concerned with driving comfort than with racing. That doesn't mean it will handle poorly, but it won't be a race car. And I wouldn't want to drive a race car on the street.

So it is really about finding what you want to do specifically, and building the best setup for that application. I would recommend picking up Carrol Smith's book Tune To Win. It goes into great depths about tuning your suspension for what you want it to do. It can be an intimidating read, but it's a plethora of knowledge. I often refer back to his books for a refresher when I am doing something new.

[abadsvt]

Originally Posted by Twisted Minis

It's really hard to say, because every type of link setup is going to act different. They way you build your setup really depends on what you want to do with it. What kind of driving you are going to do.

A few inches does make a big difference in the way the car feels, as far as roll center location. But adjustability is good, because you can tune your suspension for different tracks.

The thing with roll center, is that there is kind of a happy medium. While a low roll center is good, too low is not necessarily. The same as too high would not be good either. There is a certain point that it becomes too drastic. And the same as most aspects of the suspension system, there is no written formula, only theories that are known to work. So there is no number for a roll center that is too low. It is dependent on so many other aspects of the car and the suspension.

One thing to remember, is that the lower your roll center, the more top heavy your vehicle will feel, and the more a sway bar seems necessary.

When I build a link setup I look at what kind of driving the owner wants to do, what kind of power they have (or will have), I look at where the vehicles center of gravity is (the estimated COG, I do not have the technology to pinpoint it), I look at the front suspension design, and where it's roll center lies, and design the suspension based on that.

For my personal preference (my own vehicles) I like a fairly neutral driver. Basically, it would excel at nothing, and do okay with everything. I like a link setup that doesn't lift or squat heavily under acceleration, which means it won't have the most traction off the line, but it will drive smooth when I am cruising, and do alright when I want to get on it. I find my front roll center at my ride height, and try to match the rear roll center to the same height, to achieve a more balanced roll center for the entire vehicle. I am more concerned with driving comfort than with racing. That doesn't mean it will handle poorly, but it won't be a race car. And I wouldn't want to drive a race car on the street.

So it is really about finding what you want to do specifically, and building the best setup for that application. I would recommend picking up Carrol Smith's book Tune To Win. It goes into great depths about tuning your suspension for what you want it to do. It can be an intimidating read, but it's a plethora of knowledge. I often refer back to his books for a refresher when I am doing something new.

You have some very good points! I like how you mentioned that you build the rear suspensions to have similiar RC to the front suspensions RC. That makes sence. I will have to remember that. I have a few of Carrol Smiths book but don't have that one. I will look into getting it. Anways thanks for taking the time to answere my question. Talk to you later.


Josh

[Tony@AirRideTech]

If you are going for a serious turning vehicle you are going the wrong route with the twin charged duramax. Too heavy and too much mass. If it were me and you wanted to build something serious and put a serious contender together, I would look at running an aluminum LS motor and C-5 or 6 front and rear.


Tony....

[Twisted Minis]

Also about the IRS, they can be built with a 9" center section, and pretty much bullet proof axles. Cost is the only factor. You could spend thousands more building a capable IRS than you could a solid axle with a link setup.

[71'tahoe]

A few things to note here.

Gale Banks built a road race truck with the TT engine,of course it had a road race chassis.

Mustang II front ends are not idea for road rcing at all. The have a short spinndle hieght. Camber curve that isnt very good and in most cases a short control arm length.

I agree with Porter and Twisted you got to know what you want and the biggest thing is to be honest with your self and set realistic goals.

If you are dead set in your wanting a road race truck,then go to pro-touring.com or lateralg.net When you go there PLEASE do a search for what you want in the search thread. If you ask a typical question then plan to get flamed..they dont really like lazy people who dont want to do a lil research first. Big thing there is to read and learn before asking.

Then if you really think you got a handle on suspension and think you got it figured out you can step up to the big boys and go to corner-carvers.com
These are most generaly racers who help other racers out with tuning and design changes in exsisting race cars. they have the knowledge of all things suspension.

I have the same idea as you do with wanting a road race truck but mine is in the flavor of a 90' chevy.

Good luck with your plan. Jusst realize also that is will be easier on you to use a Porter Built x member and coil overs if you dont understand suspension design. We all hate to see another truck just sit unfinished if you get in over your head..

[Spray-Bomb]

Thanks guys

I have plenty of time to design my suspension before I get around to building it, so hopefully I get it right the first time around

[Spray-Bomb]

Ok, just curious here
I know that the diesel is a heavy engine, but with all the power & torque that it will have, and trying to get it as low in the vehicle as possible to keep the weight down low, how is that a bad choice ???

I already know this thing isnt going to competitive with a car, there is too much weight all around & its not arrow dynamic or anything like a car

[Twisted Minis]

It's a heavy motor, and being so far forward is where the problem lies. If you could move it back about a foot, foot and a half you would have better results.

[AceX]

Weight = bad

[SCOTI]

Originally Posted by AceX

Weight = bad

Depends on the type of racing. Twists & turns? Yes. Bonneville? It's a good thing.