Make it handle

[robnolimit]

I'm not sure about our race schedule yet. Tina's Mustang will be done soon, and we'll want to get it out too. --- I did'nt even think about changing the oil .

StevieB, I'd have to sat that Herb Adams book on suspension/handling is the building block to all performance. And it will take a few readings. There are others, but this one is really good.

[Hotchkis]

Originally Posted by robnolimit

I'm not sure about our race schedule yet. Tina's Mustang will be done soon, and we'll want to get it out too. --- I did'nt even think about changing the oil .

Rob,

We look forward to seeing you and your new projects! Let's make 2011 the best yet!

[Mechanic77]

Herb Adams Chassis Engineering is never too far out of my reach

[76kcfdeng]

Rob, here are some pics of the lower A arm moved forward an inch and how I did it. I would appreciate any thoughts on the good and bad of it. I mocked it up and cycled the suspension and steering with no issues I can see. I ground a notch in the lower cross arm an inch over from the stock dimple and cut the A arm for clearance. Did this to an old cross arm for a test, I did use my new drop spindles.


[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]

At bumpstop, tested steering lock to lock
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[robnolimit]

looks like it should work fine. I like it. There will be a small amount of spring shift from the lower pocket, but no issue. How long before you drive it?

[calvin78612]

Just got my copy of Herb Adams chassis engineering yesterday,so far a great book with lots of info.

[76kcfdeng]

Originally Posted by robnolimit

looks like it should work fine. I like it. There will be a small amount of spring shift from the lower pocket, but no issue. How long before you drive it?

Thanks Rob, I hope to have it driving in a few months. Depends on how much body work I want to do before I put it together, LOL. I may paint the firewall and prime the rest so I can drive it for a while and continue the body work. I thought about the spring pockets not lining up but came to the conclusion it would not be an issue. Still working on cross bracing the frame, have to make sure everything will fit.

[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.

[solidaxel]

Originally Posted by 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.

I think they call that a "govener" that was needed for the "break in period" on your truck !!!

[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.

[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.

[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.