Make it handle

[SCOTI]

Originally Posted by Jonboy

Is there a link to the JT build? I saw it in classic trucks, but am really curious to see it. Hoping to do some budget friendly suspension on my '74 once it cools down a little here.

http://67-72chevytrucks.com/vboard/s...d.php?t=436621

[69gmcc10]

On this thread you have covered allot of great information, it has really opened my eyes to some of the things that can be done to make these trucks more enjoyable, and i was hoping you could address a question for me. What should a person do to counteract wheel hop on a leaf spring setup that wants to go around a cormer and is not just interested in going 0-60 in a straight line? also would a panhard bar benefit a leaf setup? thanks.

[RANDOMIZM]

I don't know if everyone can see their pictures, but here are their times from last night. thought it would be cool to post up on here. http://www.facebook.com/#!/photo.php...type=1&theater
Rob, you guys kicked some butt there the other night. I hope I can make it out some tuesday to watch you guys teach those import guys a thing or two.

[robnolimit]

Originally Posted by 69gmcc10

On this thread you have covered allot of great information, it has really opened my eyes to some of the things that can be done to make these trucks more enjoyable, and i was hoping you could address a question for me. What should a person do to counteract wheel hop on a leaf spring setup that wants to go around a cormer and is not just interested in going 0-60 in a straight line? also would a panhard bar benefit a leaf setup? thanks.

Hmmm, you know, detroit made a lot of cars and trucks with leaf springs. It makes you wonder why. A leaf spring suspension has the unique ability to do many jobs at once. It locates the axle front-to-back (1), side-to-side (2), controls pinion angle (3), transfers brake and acceleration forces to the chassis (4), and it is the spring part of the suspension (5). That makes leaf springs VERY economical from a manufacturing standpoint. And, since the auto industry makes cars for the masses, and most of the the masses don't drive them very hard, leafs are a perfect fit. Now on to your truck, I'm guessing it's a '69 GMC. You can add a set of traction bars, like 'Cal-Tracks', they work pretty good, this will help with the wheel hop. You could add a panhard rod, and that will reduce the side-to-side shift of the axle. These additions will make the rear a little stiffer, so you may need to take the leafs out, soften them up, and put teflon liners in the spring pack. Then you could add a sway bar, (this would be the best help, but won't affect wheel hop). All of this would cost an estimated $800 - $1000 bucks. - and, you may not be that happy. If you really want it to feel consistant, and predictable, I'd find a member here that is going to a 4-bar, or an extreme drop set up, such as Porterbuilt, and buy all of their stock trailing arm parts. It's an easy swap. And you'll be happy when your done.

[robnolimit]

Originally Posted by RANDOMIZM

I don't know if everyone can see their pictures, but here are their times from last night. thought it would be cool to post up on here. http://www.facebook.com/#!/photo.php...type=1&theater
Rob, you guys kicked some butt there the other night. I hope I can make it out some tuesday to watch you guys teach those import guys a thing or two.

Thanks for posting that. - I have to learn more to copy/paste. I'll have some cool video up in a day or so from that night. Haha, a 'Jerrizzle' (a really nice guy) is a 1600lb turbo Miata on sticky rubber. - puts things in perspective. In one of the video clips you can see the axle move sideways with the new 'flexi-bar'. in place. Maybe it is too soft. Well, it's easy to tighten up. next tues we'll go out and tune with it and see what we can do.

[Jonboy]

Originally Posted by robnolimit

Hmmm, you know, detroit made a lot of cars and trucks with leaf springs. It makes you wonder why. A leaf spring suspension has the unique ability to do many jobs at once. It locates the axle front-to-back (1), side-to-side (2), controls pinion angle (3), transfers brake and acceleration forces to the chassis (4), and it is the spring part of the suspension (5). That makes leaf springs VERY economical from a manufacturing standpoint. And, since the auto industry makes cars for the masses, and most of the the masses don't drive them very hard, leafs are a perfect fit. Now on to your truck, I'm guessing it's a '69 GMC. You can add a set of traction bars, like 'Cal-Tracks', they work pretty good, this will help with the wheel hop. You could add a panhard rod, and that will reduce the side-to-side shift of the axle. These additions will make the rear a little stiffer, so you may need to take the leafs out, soften them up, and put teflon liners in the spring pack. Then you could add a sway bar, (this would be the best help, but won't affect wheel hop). All of this would cost an estimated $800 - $1000 bucks. - and, you may not be that happy. If you really want it to feel consistant, and predictable, I'd find a member here that is going to a 4-bar, or an extreme drop set up, such as Porterbuilt, and buy all of their stock trailing arm parts. It's an easy swap. And you'll be happy when your done.

How about for those of us that aren't 67-72 guys? My '74 is dropped about 6/8, and has the HD leaves out back (with a flip kit and shackles). Scoti and I have been looking tightening it up a bit (or a lot) once it cools off. We will be adding a sectioned crossmember up front. The truck has 3" spindles and cut stock coils in the front, along with the factory sway bar. Do you have a blueprint for us squares that want to have fun and not break the bank? I have air helper bags on the rear for towing (normally deflated), but they are controlled individually. I do not want to go to air ride, but to keep it static dropped.

[SCOTI]

Originally Posted by Jonboy

How about for those of us that aren't 67-72 guys? My '74 is dropped about 6/8, and has the HD leaves out back (with a flip kit and shackles). Scoti and I have been looking tightening it up a bit (or a lot) once it cools off. We will be adding a sectioned crossmember up front. The truck has 3" spindles and cut stock coils in the front, along with the factory sway bar. Do you have a blueprint for us squares that want to have fun and not break the bank? I have air helper bags on the rear for towing (normally deflated), but they are controlled individually. I do not want to go to air ride, but to keep it static dropped.

I'm curious if Rob's recommendations will differ from mine so I'll post up the one's I suggested....

Same spindles currently installed
Remove the cut sbc springs & swap in Moog's # 6102 1015 lbs/in
Swap to the notched x-member to retain the current drop w/o the travel limitations
Keep the current 1.25" 1-ton solid sway bar
Upgrade to the No Limit R&P set-up
Swap to Porterbuilts SqBody Truck arm rear set-up or CPP's (PB's for adjustability to still load it down & better T/A's)
Bilstein replacement shocks or adjustable shocks

The only other thing I recommended that will hurt the wallet is different a-arms for improved geometry since we're limited on caster.

[leftcoast66]

I just finished using that Front Suspension Geometry Pro and I'm not happy with where the roll center is. The design is all hypothetical at this point, I'm just finishing it up on the computer before I start building it. I've got all of the parts though in a box but placement on the frame is yet to be determined. Any idea on lowering my roll center? Currently on the corner optimizer at entry the roll center is at 3.94, midturn is 2.410, and corner exit is 4.982. Any suggestions on how to get this lower? I read in Herb Adams book on how it should be between -1 and 3. Any suggestions on where I should start?

[NPilot1975]

Rob, great thread. Reading through this, I am now going to scrap my triangulated 4-bar I was working on and go back to a trailing arm setup with a watts link. I already have an ece center crossmember installed. I am going to build the trailing arms using the ball style joints like on your 55. My question is about the actual arms. The factory arms kick up at the back, but I noticed your arms are straight. Does this make a difference? I was going to build them from 2.5" x 2.5" 1/4"wall steel. Btw my engine is set back roughly 4", which hopefully will help weight distribution.

Thanx for all the info I am sure I will have some more questions once I get started.
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[k5warwagon]

I am new to the site. I love it. It gives us truck guys the resource we need that Pro-Touring.com doesn't.
I do have a question for this thread. I have a '87 c10 short bed stepside. It was a prostreet project for someone else and I got a good deal on it. The PO removed the narrowed 9" rear and 4-link setup so I have nothing in the rear except the (removed) original leafs and shackels. I want to convert to trailing arms with jack bolts. Am I wasting my time looking to swap from a 67-72 and modifying it or should I just save my money and buy a kit from you or HotRods to Hell? I will be going the kit route on the front but money saved now helps.
Thanks,

[NPilot1975]

K5warwagon, I haven't done the mod, but I know you can use 67-72 parts to change your truck to trailing arms. If you are on a budget I would suggest getting a crossmember from Porterbuilt, cpp, ride tech, or early classiscs and use the factory arms. If you have the money you can buy a kit from any of the above that has all the parts.
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[robnolimit]

Originally Posted by SCOTI

I'm curious if Rob's recommendations will differ from mine so I'll post up the one's I suggested....

Same spindles currently installed
Remove the cut sbc springs & swap in Moog's # 6102 1015 lbs/in
Swap to the notched x-member to retain the current drop w/o the travel limitations
Keep the current 1.25" 1-ton solid sway bar
Upgrade to the No Limit R&P set-up
Swap to Porterbuilts SqBody Truck arm rear set-up or CPP's (PB's for adjustability to still load it down & better T/A's)
Bilstein replacement shocks or adjustable shocks

The only other thing I recommended that will hurt the wallet is different a-arms for improved geometry since we're limited on caster.

OK, this may sound like back peddling, but bear with me here. my previous recomendation was for a truck that is easily converted to trailing arms. So as to leaf spring Square body p/u's (and others) The same things apply to them as would apply to a 2nd gen Camaro. Your recipe is really good. But, no rear sway bar listed? Try the Helwig 1 1/8" rear bar. Also, the stock leaf may be a little stiff. There is an old trick of cutting the rear 40% off of a few of the shorter leafs. This keeps the front part of the leaf in place with the axle to act as a stronger axle control link, and lets the rear section of the spring act as a softer spring. I'll try to find some picts.

[robnolimit]

K5 this is an easy enough swap. I'd use the stock stuff, you'r in nascar country so I'd guess there is plenty avail. Check with Speedway or Motorstate on the spring jacks. - But remember, your frame is not the same as a 67-72, so there will be some mods needed to get the springs where you want them. You may want to consider coil-overs, it could be easier, and cost about the same.

[Jonboy]

This may sound out of place, but what will cutting the rear of the springs do to payload capacity? There are 8 or 9 leaves in the rear spring, so cutting a couple shouldn't kill it too much. Scot and I had discussed the rear sway bar; I think he may have forgot to list it. Speaking of, what would be the best way to mount it given the amount of drop (6/8)?

[leftcoast66]

Hey Rob,
Any advice on roll centers? Not sure if my post got missed, I know you're busy. I'm figuring mine out on front suspension geometry pro and it seems off.

Brendan

[NPilot1975]

Rob, I noticed that the trailing arms that you build are straight without the kickup at the end. Is there any disadvantage to this? I assume the kickup is to put that portion level to the ground, but just wondered??? Also, if you used straight trailing arms would there be any advantage to mounting them on top of the axle tubes on a lowered truck? Would this work the geometry at all as far as relation to the front mounts? or would it just completely mess it up. Thanx again.

[k5warwagon]

Originally Posted by robnolimit

K5 this is an easy enough swap. I'd use the stock stuff, you'r in nascar country so I'd guess there is plenty avail. Check with Speedway or Motorstate on the spring jacks. - But remember, your frame is not the same as a 67-72, so there will be some mods needed to get the springs where you want them. You may want to consider coil-overs, it could be easier, and cost about the same.

Thanks Rob. Working on a package deal off of a parts truck right now.

[robnolimit]

Originally Posted by leftcoast66

I just finished using that Front Suspension Geometry Pro and I'm not happy with where the roll center is. The design is all hypothetical at this point, I'm just finishing it up on the computer before I start building it. I've got all of the parts though in a box but placement on the frame is yet to be determined. Any idea on lowering my roll center? Currently on the corner optimizer at entry the roll center is at 3.94, midturn is 2.410, and corner exit is 4.982. Any suggestions on how to get this lower? I read in Herb Adams book on how it should be between -1 and 3. Any suggestions on where I should start?

Sorry about the delay. I was trying to play with some set-ups to see if i could duplicate those numbers. I got close. First off, remember that Herb Adams (all hail the master) was playing with Camaros and mustangs, not Trucks. And, those cars have a lower Center of Gravity, CG, then the trucks do. Any change you make will have effects across the board. The only number I see thats out of range a bit is the corner exit at 4.982. Idea #1. Lower the inner pivit point of the lower control arm. (try .3") - this may also require some adjustment of the steering. #2. shorten the upp control arm (try .4"), and keep the pivit on the same line at ride hieght. (moving it out, and up) #3. Work on the rear. Part of the reason that the front RC is rising is due to the front lifting. Raising the rear anti-squat will help to counter act that. So, back to the car/truck thing. There is a balance between CG, and RC, and to be resonable, about how your truck will react, and how much the street tire will hold, I would adjust my targets from the range of -1 to 3, as Herb stated, to 0 to 4. Please don't assume that I consider myself smarter than the master here, Just remember that we run run street tires, and trucks.
What is your caster range? and how about camber gain?

[robnolimit]

Originally Posted by NPilot1975

Rob, I noticed that the trailing arms that you build are straight without the kickup at the end. Is there any disadvantage to this? I assume the kickup is to put that portion level to the ground, but just wondered??? Also, if you used straight trailing arms would there be any advantage to mounting them on top of the axle tubes on a lowered truck? Would this work the geometry at all as far as relation to the front mounts? or would it just completely mess it up. Thanx again.

We have good luck with straight arms. But you have to set the pinion angle/axle saddles to match with them. (pretty normal) I don't see any gain of top mounting, and a possible loss of clearance. The geometric 'push' is a relation from the tire contact patch, the axle center line, and the front pivit point of the arm. To change the relationship, you can change tire size, make the arms shorter or longer, or move the front pivit point.

[NPilot1975]

Perfect, I am going to build some straight arms and saddles (under mount). Do you think 2.5"x2.5" 1/4" wall tubing would be fine?
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[leftcoast66]

Originally Posted by robnolimit

Sorry about the delay. I was trying to play with some set-ups to see if i could duplicate those numbers. I got close. First off, remember that Herb Adams (all hail the master) was playing with Camaros and mustangs, not Trucks. And, those cars have a lower Center of Gravity, CG, then the trucks do. Any change you make will have effects across the board. The only number I see thats out of range a bit is the corner exit at 4.982. Idea #1. Lower the inner pivit point of the lower control arm. (try .3") - this may also require some adjustment of the steering. #2. shorten the upp control arm (try .4"), and keep the pivit on the same line at ride hieght. (moving it out, and up) #3. Work on the rear. Part of the reason that the front RC is rising is due to the front lifting. Raising the rear anti-squat will help to counter act that. So, back to the car/truck thing. There is a balance between CG, and RC, and to be resonable, about how your truck will react, and how much the street tire will hold, I would adjust my targets from the range of -1 to 3, as Herb stated, to 0 to 4. Please don't assume that I consider myself smarter than the master here, Just remember that we run run street tires, and trucks.
What is your caster range? and how about camber gain?

Thanks Rob! No worries, I didn't mean to rush you. I will check what the ranges are, the static camber is going to be -2 to start with, and the caster is at 8 I believe it was.

I did try adjusting my upper arm lower and was able to get the change into the -1 to 3 range for RC by lowering the rear of the a arm mounts (they were completely horizontal even with 8 degrees of caster).

The numbers may be a pain to duplicate because I'm running some allpro lower a arms that have been completely cut apart due to quality issues when I got them and some speedway motorsports upper arms. I can email you my file if that would be easier. You did answer my question though, thanks so much for the guidance. I've got the metal on order and all of the parts in, so it should be a fun learning curve.

Brendan

[robnolimit]

Originally Posted by NPilot1975

Perfect, I am going to build some straight arms and saddles (under mount). Do you think 2.5"x2.5" 1/4" wall tubing would be fine?
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I use three pieces, in a step. 2 1/2" tube, 2 1/4" tube, and 2" tube, all with 1/8" wall. This is plenty strong enough. 1/4" wall is a bit heavy. don't forget to try to get the unsprung wieght down.

[robnolimit]

Originally Posted by leftcoast66

Thanks Rob! No worries, I didn't mean to rush you. I will check what the ranges are, the static camber is going to be -2 to start with, and the caster is at 8 I believe it was.

I did try adjusting my upper arm lower and was able to get the change into the -1 to 3 range for RC by lowering the rear of the a arm mounts (they were completely horizontal even with 8 degrees of caster).

The numbers may be a pain to duplicate because I'm running some allpro lower a arms that have been completely cut apart due to quality issues when I got them and some speedway motorsports upper arms. I can email you my file if that would be easier. You did answer my question though, thanks so much for the guidance. I've got the metal on order and all of the parts in, so it should be a fun learning curve.

Brendan

I would set static camber at -1, and try to get 1 to 1/2 deg of gai per inch of compression travel. On the upper A-arm mount, drop the rear pivit 1/2" to 5/8" below the front. This should give you appx 6 to 8 deg lean back on the upper arm, or anti-dive, and the truck will need this.

[NPilot1975]

Rob, how much overlap for each step or does the 2" run all the way from end to end with the additional tubing added? Thanx again, easier to do it right from the start.
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[robnolimit]

Originally Posted by NPilot1975

Rob, how much overlap for each step or does the 2" run all the way from end to end with the additional tubing added? Thanx again, easier to do it right from the start.
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about 3", we drill a 1/2" hole in all sides, 2" back from the end of the larger tube of the overlap to plug weld as well as the end seam. If you need some parts I have inserts for the 2x2 tube with a 1 1/4" thread inside, 18.00 ea. ! 1/4" male thread monster ball pivit knuckles, 39.50 ea. and 3/16" formed steel mounts with hardware (for the monster balls) are 16.00 ea. 147 for all parts needed for the front mount/adjuster assy.