Make it handle

[bedsled71]

does anything have to be done to the top control arm?

[76kcfdeng]

Bedsled71, nothing needs to be done to the upper arm, according to Rob 1" forward on the lower arm should net 7 degrees caster.

[tomtuna1978]

so then what dose it do for the wheel being centered in the wheel well ? will it be 1 in. forwrd ? how will it look ? ... this looks like simple way of improving the alignment !!! and im verry interested in this as id like to improve my alignment !

[robnolimit]

Originally Posted by tomtuna1978

so then what dose it do for the wheel being centered in the wheel well ? will it be 1 in. forwrd ? how will it look ? ... this looks like simple way of improving the alignment !!! and im verry interested in this as id like to improve my alignment !

with a dropped spindle, the wheel will move forward about 1/2 of the lower A-arm shift. So, about 1/2".

[tomtuna1978]

1/2 in. wont look bad ! ... so ...to get this rite ... if i move the lower control arm forward 1 in. and put on a drop spindle it will give me aprox. 7 deg of caster ? ... this is a cheep mod ! does it matter what size (2,2.5,3 in. drop) drop spindle i use ? id like 3 if i could get some.

[76kcfdeng]

Does not matter the drop, caster will be the same. It will move the wheel forward different amount depending on the spindle but a small amount no matter which, 1/2" or less.

[robnolimit]

GOOOD MORNING !!! A little help here. Just for my own info, did you guys like the drawings last week? Does that type of thing help?let me know. thanks.

[dirtball]

Originally Posted by robnolimit

GOOOD MORNING !!! A little help here. Just for my own info, did you guys like the drawings last week? Does that type of thing help?let me know. thanks.

The drawings really help me out. Really appreciating all the info you are sharing here.

[gcrtech]

Awesome stuff in this thread!! I'm new here but I've been been working on old Chevs for years. Currently working on a 66 SWB for the street and a 68 GMC for roadrace/rally fun. Preparing for a race called Targa Newfoundland, check it out at www.targanewfoundland.com.
I raced late model stock cars fo 20 years so some of this stuff is familiar, but I really like the truck specific stuff like swaybar sizes, alignment specs, etc.
Rob, I'm trying to decide on spring rates for the roadrace truck. I'm thinking 600lb front springs with a 1.25 inch sway bar and 175lb rear springs and a 1.00 rear bar. The race is held on public roads which can be quite rough. I am guessing shocks will be very important too and I was thinking about running Afco stock car shocks because I have some experience with them. Let mee know what you think would be a good setup. Thanks

[dirtball]

Looks like this could be a good time to ask something that I have been scratching my head over. On the Hotchkis site, they show that their spring rates for 67-72 trucks are 1100/380 lbs/in! Those rates sound extremely high to me, I can't afford to drive down the road and knock the fillings out of my teeth. What do you think of these rates Rob? I gather you like the soft spring/ big bar approach. Hotchkis is using a 1 1/4" front bar with those springs in the TVS kit. The other question is about them using a 4" drop spring and no dropped spindle. I don't see that as being an ideal set up. Thanks for all your input Rob!

[4x4fab]

I def. like the drawings, helps me to understand things.
I'm in the middle of my build, Chopped 64' SWB. It will be bagged on a dropmember and linked rear, prolly parallel 4 link...?..........
I have the frame on the chassis table right now, finishing the notch and started bending some 1.75 x .120 dom to stiffen the frame up. My question is if I should spend the time boxing in the frame? this isn't going to be a race truck, just want it to handle nice and I have the ability, no how, and tools to do it right. I know there is more to it than just fully boxing the frame, and I'd love to learn more.
Thanks a lot for sharing your knowledge, I've read this thread 3 times now.

[Hotchkis]

Originally Posted by dirtball

Looks like this could be a good time to ask something that I have been scratching my head over. On the Hotchkis site, they show that their spring rates for 67-72 trucks are 1100/380 lbs/in! Those rates sound extremely high to me, I can't afford to drive down the road and knock the fillings out of my teeth. What do you think of these rates Rob? I gather you like the soft spring/ big bar approach. Hotchkis is using a 1 1/4" front bar with those springs in the TVS kit. The other question is about them using a 4" drop spring and no dropped spindle. I don't see that as being an ideal set up. Thanks for all your input Rob!

Hey Brett,
Those spring rates would be extremely high if we used them on an early Camaro.

A 69 Camaro would take about a 650 to 700 lbs spring depending on the engine size and application. The difference would be that the Camaro and the 67-72 Chevy trucks have different control arm length, spring position, and weight, which change the amount of leverage needed to compress the spring. These differences necessitate different spring rates.
By watching the PCH Rods truck on the track, it definitely doesn’t have too much spring rate. Rob really has the truck dialed in with our TVS suspension system for the ’67 through ’72 Chevy Trucks. On the autocross, Rob's truck beat many well-setup cars at the 2010 OUSCI event (shown). He even beat Steven Rupp's '68 Camaro from Camaro Performers Magazine (event Champion from 2008)!



If you were up for a road trip from Colorado, you could come to our big open house. Hotchkis is having a C-10 Show and Open House event on February 12. You could see our facility and see how we continue making high-quality products that perform. You could see us in progress of rebuilding the Hotchkis C-10 project truck in person.

http://www.hotchkis.net/press_release.html?ID=54

[robnolimit]

Spring rates for stock style C-10's seem high, but this is do to the A-arm ratio. Here are some stock spring rates
Moog # 6082 722 lbs/in 6 cyl, and light v-8
Moog # 6542 842 lbs/in std v-8
Moog # 6102 1015 lbs/in bigblock, longbed c.s.
Moog # 6104 1016 lbs/in 3/4 ton, sits 1/2" higher than #6102
Moog # 6454 1060 lbs/in 3/4t bbc, c.s, 1ton
So, Hotchkis' 1100lb may not be so heavy. I currently have the #6082 spring with one coil cut in the JT project, and it is too soft for me. I'm going to swap in the #6102 springs next week. Going to track test it tues. with the soft springs. All my number crunching shows me a 950 spring, but we'll see.
When it comes to frame boxing, i'm not a big fan of full chassis boxing, as it can lead to a cracked frame. Bracing key areas, and creating triangles is a better aproach, check the earlier posts.

[GEARBOXGARAGE]

Originally Posted by robnolimit

Spring rates for stock style C-10's seem high, but this is do to the A-arm ratio. Here are some stock spring rates
Moog # 6082 722 lbs/in 6 cyl, and light v-8
Moog # 6542 842 lbs/in std v-8
Moog # 6102 1015 lbs/in bigblock, longbed c.s.
Moog # 6104 1016 lbs/in 3/4 ton, sits 1/2" higher than #6102
Moog # 6454 1060 lbs/in 3/4t bbc, c.s, 1ton
So, Hotchkis' 1100lb may not be so heavy. I currently have the #6082 spring with one coil cut in the JT project, and it is too soft for me. I'm going to swap in the #6102 springs next week. Going to track test it tues. with the soft springs. All my number crunching shows me a 950 spring, but we'll see.
When it comes to frame boxing, i'm not a big fan of full chassis boxing, as it can lead to a cracked frame. Bracing key areas, and creating triangles is a better aproach, check the earlier posts.

Jonboy.......We're refering to the Moog # 6102. robnolimit posted this a ways back.....

[tubbedII]

Are you going to cut a coil on the 6102's as well? If so, what spring rate does that put you at?

[robnolimit]

Oops, only 1/2 the answer. I do like a softer spring/bigger bar set up. I do a lot of number crunching as a start, then go to the shop, then the track or street. This way I can cut down the development time. It's tough to get the rears to grip. I run a 220 rear spring on the bullit, it's on a rocker arm and the ratio yeilds 180 lbs on the axle. I may try a 200 spring, yeilding 163 lbs. Then it's all shock tuning. So, on a C-10, with the arm leverage and a bit more rear weight, first number crunch shows a 268 spring. So maybe a 300?

[robnolimit]

as you shorten the spring it gets stiffer. I am going to trim them to my liking, and then I'll measure and let you know.

[dirtball]

I figured the A-arm ratio had to be playing into it but didn't expect that much. The 1100 lb rate does not sound so high now. So what is your take on a 4" drop with spring only, not in conjunction with spindle? I would like to get rid of my dropped spindle so I could run more B.S. on my 15" wheels.

[robnolimit]

That brings up a good point. Springs vs. spindles. Lets start with the concept of a stock truck. If you put a set of 2 1/2" drop springs, the truck is lower, and the Roll Center changes (lower) a lot. Looking at the next drawing, first you need to understand the Instant Center. This "point" is the connection of two lines passing through the ball joints and A-arm pivit points. The I.C. is the point at which the mass of the truck rotates to push on the tire in a corner. As you lower with springs, the I.C. of each side drops.
Next is to understand the Roll Center (very important) The tire is grips the ground. So, the force line, or direction of push, on the tire, is the line from the I.C. to the center of the contact patch of the tire. The point where the two lines cross is the Roll Center. Natural "body roll" (without swaybars to control it) is created by the difference from R.C. to the Center of Gravity. We can estimate the C.G. of these trucks at about 2" above the cam shaft. The farther the R.C. is from the C.G., the more body roll, = less traction. There can be some positve benefits from shorter springs, such as more agressive camber gain, but once the lower ball joint is higher than the lower A-arm pivit, your loosing ground. In casses of really short springs, say 4"+, it is easy to have the R.C. under ground, not good. The goal is to get the R.C. as close to the C.G. as you can. When you drop with a spindle, the R.C. is not effected as much as when you drop with a spring. Just a note, Z'ing the frame up, - or - raising the crossmember may be the best aproach for handling in these trucks, as you get the lowering (lower C.G.) without lowering the R.C. - food for thought.

[dirtball]

Hmmmm....good info. Your pictures really do help to understand these concepts. It does sound as though I should keep my dropped spindles for now.

[JNJchev77]

The pics are a big help... This thread is one of the best I've seen!

[robnolimit]

As the discussion continues, there have been a few questions about Roll Center vs. Center of Gravity. If you were to built a truck from scratch, and your goal was to get these in check, your truck would look alot like a Lotus. So, bad to the business of Trucks. I've had a few chats with Nate Porter lately, and I can tell you that he is on the right track with his new performanced based Dropmember. This concept is simple. The raise crossmember drops the truck, and thus the C.G. without negatively effecting R.C. Although drop spindles are better than drop springs (for that 2 1/2" of drop) they still drop the R.C. some. Appx 1/2 the drop of the spindle, so about 1 1/4". If the Dropmember, or raising the stock crossmember, or Z'ing the frame, drops you 3" without any loss in R.C. hieght, then with drop spindles you would have a 5 1/2" drop for the truck, and C.G., with only a 1 1/4" drop in R.C. This combo would get you a net 4 1/4" gain from R.C. to C.G. This is all with a stock spring. Food for thought. If you are in the area, I suggest a trip to the Hotchkis open house on feb 12. The TVS aproach is a simple bolt-on uprade, and it is worth a good look to see how they sorted out the steering geometry.

[robnolimit]

Greywolf. It realy shouldn't be that bad. Our JT 72 has no sway bars yet, and now, with the right springs, and an adjustable panhard rod, it's OK. Check the Idler arm, could be giving you fits. The stock design is not so good, but it's all there is for now. If you have no swaybars, and its neer stock hieght, thats a problem. As luck would have it, we are currently working with Helwig to build us a custom sway bar based on our specs. Also, last week we finished prototyping rear 'long-travel' rear shock mounts for trailing arm trucks. I'll share picts next week.

[Mechanic77]

Hey Rob, quick question, how long do you suggest I make my sway bar arms on the front? I've already bought a Speedway Engineering 1.25" dia, 38.5" long bar and a set of their straight steel arms. Obviously the shorter I make the arms, the stiffer it will act. I'm just looking for a good starting point.
Thanks, Andy

[michaelnolimit]

Mech77, you may need to bend the arms outboard to get to a good connection point on the A-arm. 10" is a goo starting point. I mount the bar close to the stoch location, and start from there. Make sure that your arms clear at full L/R turn.