Make it handle

[robnolimit]

Right now I have 8 different sets of arms on my back bench, and a stock crossmember. I have been mocking them up and testing them. - not done yet. it takes a while to accurately measure the pivit points. Now let me put this out early, I will let you know of the arms with positive results, but I can't name names of the ones with negative results. - so, don't ask - read between the lines. I'm not going to start a pissin contest here. OK? Hopefully I am going to meet with Nate Porter during SEMA to discuss some of these thing you guys are interested in. i'm looking forward to it.

[Ian30]

Is there a minimum verticle separation that you would recommend between the upper and lower links at the axle and frame ends? In the off-road world it was 25% of the diameter of the tire you wanted to run at the axle and whatever you had room for at the frame. I havent seen it mentioned here. Also, do you think that running a non-parallel, non triangulated 4 link like your fat bar appears to be, offers advantages over a regular 3 link other than the obvious that it puts all the links outside the frame and adds a bit of strength. I'm not downing the idea, I just have been thinking about it alot lately. In fact I was set on a triangulated 4 link, but now am leaning more towards this set up with a panhard.

[robnolimit]

IAN30, good questions. First rule, "every action creates an equal and oposite reaction", so as the axle is trying to rotate the tire forward (lets say clockwise), the axle housing wants to rotate the oposite direction (counter-clockwise). The 25% rule is so that you have enough leverage to control the axle rotation, its a good rule of thumb. one more note, we want the truck to go "forward" under acceleration, so to get the leverage to help, put 2/3 of your bar span below the axle CL, and 1/3 above. * top bars that are right on the axle CL (elevation) WILL NOT transfer any wieght. ** 4-bars that are parallel (top to bottom bar) WILL NOT transfer any wieght. When it comes to three links (wishbone style) and triangulated four bars, BE CAREFULL, these set-ups build with urathane bushings all around start to bind any time they move away from ride hieght. you can help this by runnung rod-ends in the upper bars to allow them to articulate. Our kits are desinged to have the lower bar level to the ground and the upper bar slopping down at 4-5deg. at RH.

On another note, we now have custom tank-crossmember kits to fir 67-87's with Porterbuilt and others step notch kits. I'l post up some picts on the 67-72 section.

[Ian30]

Rob, I appreciate you giving out all this advice, I've had a hard time finding the information that you've given here so freely. It's interesting how much of the information out there is just people spreading hear say and not actual practical stuff. I just want to start off with a decent handling suspension without any major quirks that I can possibly tweak in the future if I want more. Can I just recap what you have suggested regarding rear suspension setups and ask a few more questions just for clarification.

Low long Panhard bar - ideally equal to axle centerline.
A light swaybar - Do I run without at first and add it if needed later on?
Mount the links wide
2/3 of link verticle separation below axle centerline
Lower link approx. level at ride height, top link sloping down 4-5 degrees
Instant center should be in front of the front axle
anti-squat less than 100%Would it be better with a number below 50%??? How low is too low??

OK, thats all I can think of for now. I am also attaching some free excel link calculators that I found. I am using the 3 link for this setup even though it will have 2 upper links as the four link calc is more for triangulated setups. I don't think that changes any of the numbers having two upper links. I don't know if you have seen these before, but can you please look at them and give me your opinion if you think they are crap or a good starting point.

Thanks again, Ian

[Ian30]

ok, I have thought of another question. I have a bunch of pivot joints from another project. Would it be better to use these at the axle end or would it be best to use all polyurethane bushings everywhere? assuming no cost involved.

[mongoose]

pivot joint being a rod end or heim joint? I'd personally use them everywhere i could, though.. i'm not a huge fan of poly.. the heim's will transmit a bit more vibration but will be butter smooth compared to poly.

[Ian30]

A flex joint like this:
http://www.summitmachine.com/index.p...tomParts&cp=fj

I have a bunch of these and wondering if there is any disadvantage/advantage to using some or all of these or poly bushings.

[robnolimit]

Ian, those joints are good. We use a pivit like that on our Track-Arm kits. If you have them, use them all around, the transmitted vibration you hear about is not noticable. I have both of those calculators handy, and they are fine, thanks for posting them. When it comes to anti-squat, remember that the trucks are very light in the rear, so we need some, less than 40% seems to unload my silver 55 (Bullit) so I would try to keep it around 50-55%, it is a balance between chassis reaction - vs - traction. Keep going, you'r on the right track!!!!

[skeeterbug]

i keep hearing the term anti-squat and seen anti-squat kits for sale online what exacly does this mean or do?

[robnolimit]

Anti-squat, is a term for rear suspension. And, Anti-dive, is for front suspension. This is discussed in a % number, such as 50%, to compare how much of the wieght transfer, or load, is put into the spring, and how much of it goes to the tire. The front is easier to visualise. With low anti-dive, the front of the truck nose dives when you apply the brakes, most of the load goes to compress the suspension, not into the tire. with more anti-dive the energy would go into the tire, and not compress the suspension as much. In the rear, anti-squat is similar. Drag cars often have anti-squat values of more than 100%, all load to the tire +, But they don't have to worry about corners or braking off-camber. High anti-squat values tend to lead to wheel hop during hard braking. Anti-dive, and anti-squat geometry are linked to CG, RC, and ft/rr wieght bias. In a pickup, with a high CG, typically low RC, and an average of 58% nose wt, we shoot fot anti-dive in the 60-70% range, and anti-squat in the 40-45% range.

[ajgriffin]

Originally Posted by robnolimit

Anti-squat, is a term for rear suspension. And, Anti-dive, is for front suspension. This is discussed in a % number, such as 50%, to compare how much of the wieght transfer, or load, is put into the spring, and how much of it goes to the tire. The front is easier to visualise. With low anti-dive, the front of the truck nose dives when you apply the brakes, most of the load goes to compress the suspension, not into the tire. with more anti-dive the energy would go into the tire, and not compress the suspension as much. In the rear, anti-squat is similar. Drag cars often have anti-squat values of more than 100%, all load to the tire +, But they don't have to worry about corners or braking off-camber. High anti-squat values tend to lead to wheel hop during hard braking. Anti-dive, and anti-squat geometry are linked to CG, RC, and ft/rr wieght bias. In a pickup, with a high CG, typically low RC, and an average of 58% nose wt, we shoot fot anti-dive in the 60-70% range, and anti-squat in the 40-45% range.

So how does the anti-squat number affect acceleration?

[robnolimit]

Think about it like this. It takes some amount of force to move anything. - - -thinking - - - -IFthe tire will hold traction, the best aceleration would be with no squat. no force being used to compress the suspension, and all available force used to move the truck forward. Lots of squat will add traction, but slows chassis reaction time, because some of the force (hp&torque) is being used by the suspension. It's all a balancing act. Get enough traction to launch, but not waist time compressing the suspension more than you need.

[ajgriffin]

Originally Posted by robnolimit

Think about it like this. It takes some amount of force to move anything. - - -thinking - - - -[B]IF[B]the tire will hold traction, the best aceleration would be with no squat. no force being used to compress the suspension, and all available force used to move the truck forward. Lots of squat will add traction, but slows chassis reaction time, because some of the force (hp&torque) is being used by the suspension. It's all a balancing act. Get enough traction to launch, but not waist time compressing the suspension more than you need.

I get it. At first I was thinking you want all the force at the wheels because that's what's going to get you going down the road, but I completely for got that would be the case only IF the tire can hold traction. But the more I think about it, maybe you don't care if it can hold traction....

So in your experience what kind of driving are the anti-squat & -dive numbers good for and how does it feel in the seat?

[robnolimit]

HAHAHAHA, Let me tell you guys a bit about myself. I have a varied racing background. My dad and I ran a car at Bonneville and El-Mirage in the late 70's & early 80's. For a few years i worked on the Nissan 'P' car team, a great experience. I drag raced a bracket 1 nova, and have run Dwarf cars and an Imca modified. So, its in the blood. When I drive my dually around town, or pulling a trailer, I think even some old people are passing me. What can I say, I baby my equipment. BUT when it comes to fun driving, in a truck, mustang, the '46, or on the bike, I would say that my driving style is "spirited". Brakes and suspension allow you to get all the power out and play with it. With a bit of chassis tuning, you can get your truck to pass corvettes, on the outside! The feel of a balanced chassis is foreign to most people, But how cool would it be to have your truck feel like a 370Z or an Audi R8 (must save all pennies for an R8) I like to know that it will turn into a corner, and it will come out under power, it's pretty cool.

[M5-]

That pretty much describes what I want out of my truck. The big question is how do I get there, fix the stock chassis or just flat out replace it? If I knew that every part I purchased was going to be the perfect part I'd probably just mod the 65 chassis but if my previous projects are any indication a guy ends up buying quite a few parts that don't seem to end up on the finished product because something better is discovered at a later date. This time I'd really like to just do it once. On that note any progress on the control arm testing?

M5

[68GMCCustom]

thats where mines headed also....tho it won't be completed anytime soon.
some of us just prefer trucks over cars... and want our "street truck" to handle like a performance car.

My current front end mods are only temporary...I plan on adding a coil over IFS with rack and pinion (but not a MustangII design) to help me get there. I also wonder if I should just save up for the complete chassis that also replaces the trailing arm setup with a 4 link or something else.

[stich626]

with the castor at the 7-9* how much more force is put on the ball joints.
in turns and over bumps (pot holes)

[BossHogg69]

I've been eyeballing this thread for a while and have some questions too - in regard to bracing a stock frame, I've heard that a good rollcage does wonders for stiffening a frame. That being said is it money/time better spent on a rollcage or trying to figure out how/where to brace and triangulate a stock frame? I have no plans on boxing my frame (unless absolutely necessary), but I would like to add some bracing and/or a good rollcage to stiffen it up a bit. I'm building towards a 'Pro Touring' truck since I really like that look and functionality of that genre and love trucks. Of course like everyone else here I want to surprise the unsuspecting 'sports' car every now and then, but I don't want a glaring 'racecar' with a bed either. I have tried to choose my parts carefully and already have CPP tubular upper and lower A-arms, 4 wheel disc brakes, a quick ratio steering box, front and rear sway bars and plans to fab up some trailing arms out of 2x3 .120 or 3/16" wall tubing. Not to mention the 600hp 468" BBC and TKO 5spd transmission, and the 335/30/18 rear tires on 18x12 wheels. I've got plenty of tools and a nice welder, I just need some direction on making this pile of parts work together!

[tomtuna1978]

i just read this all and am eager to see what control arms are good and what kind of figures you come up with ! id like to know how this front suspension fares and how much work ill need to do to get it up to snuff

[robnolimit]

Good Day gents. This may be my last post till after SEMA and the Optima Invitational. So, I'll try to make it a good one. When you start a project, the first thing you need is a REALISTIC budget. how much are you planning on spending all together. The chassis/suspension/brakes will use up 20% or so of the budget. So, a 50k build gives you about 10k for chassis parts/labor. With this in mindI think there is a range, around 9k, where you really need to look at a new chassis. If your budget plan is less than this, work on the stock chassis. But if it is higher than that, it's time to look at a new chassis. Your stock chassis can be made to drive very well, but at some point you are waisting time and money trying to push it too far. So, set up a plan, and stick to it.
If you have a trailing arm truck, don't give up on it. They work great, they just need a bit of a tune up. Chevy built them to be trucks, and you want a cup-car, so a bit of work should be expected.
As to my A-Arm testing, I probably would be done till after SEMA. Caster angles of 7-9deg don't put any additional load on the ball joints. The first problem created is bumpsteer. When we tip the spindle back to get more caster, the steering arm raises, in relation to the rest of the suspension. To cure this you can, A)- Use an adjustableouter tierod end, such as a Baer-Tracker. B)- Use a custom center link to raise the inner pivit points, like in the new Hotchkis kit. Or, a combination of both. The testing i have done so far has shown me a bunch of bumpsteer with the stock parts anyway, so a fix is needed. by the way, ALL CARS BUMPSTEER some, as soon as the wheel turns, its a new ball game. Be ware of those who say they have NO bumpsteer, for they may not know what it is.
Roll cages. if you can take the look, do it. Here 's the chassis lesson for today. ---- 3D is better than 2D --- got it? Take a new cardboard box, and lay it out folded flat. Grab two oposing corners and twist. Easy isn't it? Now, open the box and tape it together. Try twisting it now. Harder? it has the same amount of cardboard. 3D is better. And if you are laying out your own cage, think triangles.
Have a great week guys, and wish us luck at the Optima Invitational.

[robnolimit]

Update. Last night we went track testing at our local track. I ran a personal best 48.06 (prev best 48.40). Baer brakes and a change in rear shock compression (softer) definately help. I think we're ready for the Optima OUSCI. i'll try to get some good picts and vid at SEMA and Optima.

[68Stepbed]

If a person were to look into building a custom chassis, what benefits would ther be in switching to an IRS setup? Is IRS buildable from scratch or would one need to salvage some Corvette pieces?

I'm only asking in case someone else is interested. I know I would never be able to do an IRS on my budget.

[robnolimit]

Well, I once built an IRS from scratch, and can say that I don't recomend it. That route will cost you plenty in time, money and heartache. But, an IRS may be more reasonable to do than you think. We do a bunch of them here using the Crown Vic - TownCar IRS unit. OK, don't gasp too hard. I know it's a Ford unit, but so is a 9", don't hate on it too much. The Crown Vic IRS unbolts from the doner car in a cradle with four big bolts and drops out. Salvage yard price is around $400 in So Cal. These have an 8.8" gear set with ltd. slip, disk brakes, and are easily converted to air ride. Swapping one in is pretty easy, you just trim the stock cradle to fit into your rails, set the pinion angle, and true up the CL then weld in the cradle. From there it's a bolt in. Check one out on your next bone-yard excursion.

[Ian30]

I just saw an episode of Trucks where they put an IRS from a Mustang Cobra into a ford ranger - they said they got it for cheap and it sure didn't look all that difficult to install. I'm not convinced that its the best way to go. Rob - Good Luck at the Optima invitational, and maybe soon I will have some pictures of some chassis stiffening that I'm working on for you to critique so others can learn from it - Good or Bad.

[robnolimit]

Here's a quick lesson. BEFORE you go to the dyno shop, check to make sure that the throttle blade goes to WOT when you push the pedal to the floor. To be honest, we never did. First full pull was 331 rr whl hp. WHAT? then, we adjusted the cable/linkage to get full throttle (I felt like a 6 yr old that spilled the milk). Next pull, 428 hp. After a bit of tuning, 443 hp, 468 ft./lb. Crap, i've been running all year on about 5/8 throttle. I will say, it's a lot faster now. So, check the simple things. Have a great weekend.