Make it handle

[laid67]

Insidious 86, I would think the additional un-sprung weight of a Watts link might offset whatever benefit it might have over a well designed panhard bar set up.

[robnolimit]

Locating Devices Good topic. For normal builds, there are a few types. - I know, but most street builds are not going to have a Satchel Link, Jacobs Ladder, Mumford Link..... Lets keep it simple.
1) Diagonal Links Such as in a triangulated four bar. This is simple and effective, but the same geometry that keeps the rear axle centered also creates a bind during the suspension travel. The fix is to use piviting joints, or rod ends, for the link ends, but this can be expensive and yeild a harsh ride. Also, this design is difficult to tune and adjust the roll center and anti-squat.
2)Panhard Rod Still pretty simple, this is the 'fifth' link in a four bar system. A panhard has only one job, side to side location. They can tend to 'push' or 'pull' the axle to one side during suspension travel. The fix is to use a long panhard rod. A 30" panhard rod has appx .190" of side motion in 6" of travel - if it is level at R.H. Packaging a longer rod into the chassis can be tough. Roll center tuning is easier.
3)Diagonal locator This is more of a drag car item. Typically on a four bar or ladder bar. This is a diagonal link that mounts to the front of one lower bar, and the rear of the other lower bar. Sometimes with a bend in the middle to clear the driveshaft. While easy to fit in most of the time, this is not a real 'street' friendly set up, as it does not want to let the car 'rotate' in a corner.
4)Wish Bone Used in Off Road and Drag racing, This can be used with, or in place of two bars in a four bar. We see this more and more in air bag installs. While this works, there is little to no gain in street performance. To work correctly, it needs piviting mounts on all three ends, rod ends or pivit links, such as Johnny joints.
5)Watts Link A watts link may be the most accurate locator, and one of the most complicated to get right. Packaging may be tough. Also, while the motion is very pure, it is more difficult to have a tunable set-up for the roll center.

[laid67]

with a panhard bar. is it possible to have it too low? would it be good practice to set it as absolutely low as I can while still having adequate ground clearance?

[modernbeat]

Originally Posted by laid67

with a panhard bar. is it possible to have it too low? would it be good practice to set it as absolutely low as I can while still having adequate ground clearance?

Yes, but everything else has to be planned around it at the same time.

Here's my old Lotus 7. The Watts link is parallel to the ground and under the axle. The rest of the suspension is a three-link with a LOT of adjustment in it.

[Custom 68]

Ok all I have read and reread as most of you have and I wanted to address Bumpsteer again. I know this has been talked about a few times but here it is again.
First off the goals of my truck are like many I am sure I like to drive it! I have had this for over 20 years and it continues to evolve but one thing is I like to have it out even though I consider it somewhat of a show truck. I am also getting the urge to Autocross and I want to do it in this truck. I did this some many years ago and was in an A-mod class with a purpose built "car" for formula SAE while in college.
I have taken Rob's IC or bump steer drawing and have tried to create my own. From his drawing the upper and lower control arm extension lines both meet. Well as I have tried to measure and graph or draw mine out it appears that the upper line is running up hill and the lower almost parallel to the ground so these can never intersect.
As you know the lower arm mounts are parallel with each other so this is easy to figure however the upper has mounts where one is higher than the other What I did was average these to come up with my drawing.
Now as I measured with a tape measure there is some question on where at the ball joint you would measure too so there is some room for error but it should be close.
What I am working with is factory mounting points on my frame with a factory lower (modified for a coil over setup) and CPP upper arms. The spindle is the 2.5 inch drop CPP modular spindles. My mounting points should be "factory".

I am close to getting the rack and pinion setup mentioned in here but wanted to understand this better. Since the outer tie rod mounts on the bottom of the steering arm instead of teh top it seems backwards and will only hurt my bump steer unless the rack is much much lower.
That also brings up the question of why would you using the factory setup mount this to the lower side of the mount, I have read of this swap too.
Rob mentions the steering mount is too high from the factory I am having a hard time grasping that based on my sketch. Help me out, what am I missing.
Thanks
Dave

[Custom 68]

Alright my new tires came in and I got them mounted. I am probably going to lower the front another 1/2 inch or so to see if that will bring the upper a-arm back into a better position. Then off the the alignment shop I have them setup for tomorrow after work. Currently visually it looks like my camber is out of wack the top seems too far in. I will get them my specs and go from there.
After I get this all back home and where it needs to be I will get some more measurements. I would really like to understand this and get things to where it feels right.
I am still struggling with moving the outer tie rod piviot to the bottom of the arm that still seems backwards...

[laid67]

Thats awesome, Never thought of a watts link working on its side like that. that has to be one of the most compact rear ends I've ever seen.

[modernbeat]

That axle is out of an '85 Mazda RX7. For reference the tires are 20" tall and 10" wide. The wheels are 13x10.

[Big Rick 53]

Thanks to all of you for showing how to make my truck handle. I hope I'm thinking right. Well I all ready have rebuilt the front end I used Moog parts bushing,ball joints,tie rod ends and Monroe magnum shocks both ends. I added power steering and disk brakes I'm using a fruit jar master cylinder(for now). The sway bar is a 3/4" bar with new bushing. Springs on both ends are Moog cargo coils,the rear end is a12 bolt 411 I have all ready cleaned up arms and welded up 1" skip top and bottom new Moog bushing. The first time I get a ride with a 12bolt 411 and I need 340 or 307. What I'm thinking is remount the the rear shocks out side of the frame and behind axle, the sway bar wider than the frame the arms mounting just in side of the brake backing plates. For the track bar the rod end on the end of the driver side trailing arm and bushed rod end mounted level and a mount to out side of frame at the level of the pass side trailing arm. I'm looking for a front sway bar about 11/4" and longer than the one I have to mount just in side of ball joint on both sides. Well am I thinking close to right? The power for now is a 283 punched 120 for close to 301ci down the road it will get a big inch sbc I'm putting a 700r in it has a 4speed Grannie trans (bad clutch) it will be pulling a small trailer and mostly road trips.

[Southern Shaker]

whats a good height for cornering ? how low can i bring her down and whats the best way to do it ? Thanks in advance -Aden

[jimmydean]

Rob, are you and Hellboy going to get a shot as a ringer on R U Faster than a Redneck?

The C10 they had was bad ass, but nothing your level. I would like to see what y'all would do against that GT-R.

[Big Rick 53]

I LEFT out that my truck is a 66 c10 sub and that's why I want to mount everything as wide as I can all that roof up top = body roll in my thinking. The info on this site made me rethink my whole setup the only thing bothering me is who's wheels and tire will take a MONTANA chuck hole. That kinds of our autocross in the spring we have frost heaves and all the roads turn into a autocross with DEEP chuck holes instead of ORNAGE cones. Short side wall tire = broken wheel. That's why we have winter and road construction for seasons. WILL BE ORDERING A TRACK BAR and shock kit from NO LIMIT soon thanks to all this is best upto date info going.

[midnight340]

Rob, I have read this entire thread over the last week or so, taking notes all the way. I really appreciate your sharing your knowledge and love your trucks! (warning: non-Chevy content, but trailing arm related)

I need some help and have a couple of questions. I've run my truck for 20 years, street, drags, and autocross a few times... and want to improve handling.

First here is what I'm working on (a bit different from most here, but I trust the questions will be relevant to this forum):

1950 Ford F-1 w/ 340 Dodge/727 (so small block weight). Volare front suspension that I have ordered a Firm Feel 1-1/4" sway bar for, and plan to order Fatman dropped spindles. Am installing a Firm Feel stage two steering box and longer pitman. The truck weighs right at 3200 lbs (no driver) and is fairly light in the back end as I have no tailgate and am running an aluminum bed floor. Truck sits low, is chopped, with steel tilt front sheet metal. Rear end is Ford 9" with 3.89 gears.

The frame is boxed back to front cab mount, boxed over C-notch, has heavy cross-member about 16" behind cab. I will add the trailing arm cross-member (near rear cab mounts) and one for coil-over mounts. Frame has 7" rails.

I am changing from leafs to trailing arms. I have a Brothers aftermarket crossmember, stock trailing arms I've separated, painted and bolted together. I intend to run coil-overs at rear of arms outside the frame rails. Will run a fat Speedway Motors chromo 32" track arm at axle height or lower.

I am going to see if I can figure a way to reuse the stock Volare 1" sway bar on the rear with shortened ends to increase effectiveness (heat, flatten, re-drill ends)

Question 1: Since I failed to weigh the rear separately before tear down- do you have any suggestions as to where to start with spring rate?

Question 2: I have some budget limit, but am looking at 2" Pro TA shocks which are listed as compression 3, rebound 5, in Speedway Motors catalog. Would these be appropriate? and what length should I be looking for? Will 7" work (compressed 12.5", extended 19.5") I have about 4" axle to C-notch as it sits.

Any help you could offer (or anyone else!) would be appreciated. Or any other suggestions. Thanks, guys!

[midnight340]

Big Rick 53, I know what you mean about the chuck holes and road break up. I spent a year in Bozeman... a lot of high speed runs to Billings (no speed limit, in 1980 anyway). I think my ex still lives in Billings. Good times!!! Beautiful state.

[midnight340]

I forgot one question to do with anti-squat in the lengthy post above (sorry for the length, but didn't know how else to get to the questions...)

My truck has a 114" wheelbase, is light, and sits pretty low... so would it be best to mount the trailing arm with the bracket hole at the top vs lower position???

And thanks again, I appreciate all the info on this thread!!!

[midnight340]

Rob...Damn, I feel like a jerk! Just found where I needed to be on the No Limit Engineering site and found your fat track bar and see also you sell the Pro shocks. I'd love to order and support your business, only fair after all the great help you've been to so many!!
Posted via Mobile Device

[midnight340]

Some progress today, cleaned old brackets off 9" and clamped re-furbished arms to axle, located trailing arm crossmember. Checked centering, wheel location, x-measured everything. Will weld and bolt it up tomorrow.

(due to 1 1/4" offset of motor/trans I had to modify the crossmember a bit to give driveshaft plenty of clearance.)

I'd still like some advice on coil-over spring rate (mounted at end of arms behind axle and outside frame. Anyone with experience with this?

[robnolimit]

Looks good so far. for spring rate, think "light" Here's an estimate. 1400 lbs total rear weight. - 225 unsprung wt (axle, wheels/tires, 1/2 suspension, 1/2 drive shaft....) that nets you 1175 lbs sprung wt. , or appx 590lbs per side. If you use a coil-over with 5" of stroke, you have 2 1/2" of spring/shock compression at R.H. + 1/2" of static spring pre-load (never run the springs slack at full open) So think that you have 3" of spring compression at R.H. Now do the math, 590 lbs of sprung wt. divided by 3" of compression to R.H. = 197 lb/in or 200. Now, with the spring behind the axle, you gain on the motion ratio, making the spring feel stiffer. It has more leverage. You may want to drop to a 180 spring. With a 4" stroke shock, thats 2" to R.H., + 1/2" static compression, or 2 1/2" spring compression at R.H. so, 590lbs divided by 2 1/2" = 236lb/in. try a 225. good luck with the truck. R U going to Nashville Goodguys?

[hotrod1]

Hey ROB:

Automatic or Manual Transmission?

[robnolimit]

Originally Posted by hotrod1

Hey ROB:

Automatic or Manual Transmission?

thats a tough call. For longer, full road coarse, i'd say manual. But for short auto-x, an automatic may have some merit. Trent Summers (Summers and Sons black '70 C10) and Mark Bowler (Bowler Transmission) worked up what may be the ultimat short coarse package. They built an auto - 4L80 I think, that does some very cool stuff. Using some electronics and delay box stuff, this is what it does.
1) it leaves the line on the converter like a normal automatic, then within about 2 seconds of the launch, the converter goes fully locked up, and stays that way, acting like a stick trans, and allowing engine braking and throttle steering in the corners.
2) buttons on the steering wheel control the up and down shifting 1,2,and 3, using a simple ail cylinder on a ratchet shifter. The up and down shift is WAY faster than you could ever shift a stick. Reverse manual valve body.
So, using an auto, they get off the line faster and smoother, and shift faster up and down. It is a bit heavier, and needs a big cooler.

That being said, I like a stick, but, I'm currently building a 65 mustang using a C4 with a gear venders OD behind it. I want to build this car capable of finishing the 'One lap of America' next year, and this combo lays out to be the simplest and most bullit proof. What? Never heard of the One lap? google it, it's awesome.

[SCOTI]

Originally Posted by robnolimit

thats a tough call. For longer, full road coarse, i'd say manual. But for short auto-x, an automatic may have some merit. Trent Summers (Summers and Sons black '70 C10) and Mark Bowler (Bowler Transmission) worked up what may be the ultimat short coarse package. They built an auto - 4L80 I think, that does some very cool stuff. Using some electronics and delay box stuff, this is what it does.
1) it leaves the line on the converter like a normal automatic, then within about 2 seconds of the launch, the converter goes fully locked up, and stays that way, acting like a stick trans, and allowing engine braking and throttle steering in the corners.
2) buttons on the steering wheel control the up and down shifting 1,2,and 3, using a simple ail cylinder on a ratchet shifter. The up and down shift is WAY faster than you could ever shift a stick. Reverse manual valve body.
So, using an auto, they get off the line faster and smoother, and shift faster up and down. It is a bit heavier, and needs a big cooler.

That being said, I like a stick, but, I'm currently building a 65 mustang using a C4 with a gear venders OD behind it. I want to build this car capable of finishing the 'One lap of America' next year, and this combo lays out to be the simplest and most bullit proof. What? Never heard of the One lap? google it, it's awesome.

One Lap quality vehicles are the ultimate hot rods.

[68racer]

I used a 170 spring in that location with good results.

[midnight340]

68racer thanks for that input, I assume that's on a C10? or?

And Rob, I want to say I really appreciate the computations and the experience behind the knowledge.

On the installation on my F-1... in order to run low and to get good arm/frame clearance I had to pull the arms in a bit, putting the u-bolt partially below my c-notches which limits the travel I'd planned. I may modify the c-notch areas some... will have about 3-1/2" inches of travel (axle to frame) from ride height, but if I could run with only 2-1/2" spring compression I'd be fine.

So it sounds like I'd be fine with a 2" bodied (compr 3/ rebound 5) 7" shock (coil-over) with 2-1/2" 200-225# spring? Do I have this right?

And once I build the coil-over mounts (rectangular tubing across full width of frame) then I plan to x-brace from there forward to stock mid-crossmember. Should give me a good rigid rear section.

[AEA]

Something I've been wondering about. On a 67-72 C10 if you had plenty of horsepower and brakes. Would there ever be a situation where it would make sense to use ballast in the rear to help the front to rear weight balance?

[robnolimit]

Originally Posted by AEA

Something I've been wondering about. On a 67-72 C10 if you had plenty of horsepower and brakes. Would there ever be a situation where it would make sense to use ballast in the rear to help the front to rear weight balance?

Yes, I have ballasted plenty in the past. It's a trade off. Total wieght means slower acceleration, but balance can be faster in the corner. Also, rear weight can add traction. Solid steel blocks (I don't think I can say lead blocks) bolted to the frame rail, or a nice 3/16" steel tray to safegaurd the fuel tank. "No sir, thats not ballast, thats a skid plate to protect the fuel tank". "what, added strength to the rear of the chassis, no, thats a safety item"