Make it handle

[GEARBOXGARAGE]

I've been following this thread for a while and have looked over the posts several times, but I haven't seen much of an answer to a topic that was covered around pages 8, 9, and 10. The topic was about anti-squat and that brought up the theory of swapping or changing the trailing arm mounts to reposition them higher at the crossmember. One member asked what a recommended pinion angle should be, but I seem to have lost the exact location of that post. Robnolimit, you comment that getting the right pinion anlge is free horsepower. Do you have a recommended pinion angle and could you give a little insight on if/how pinion anlge affects handling or perfomrnace?

[wickid demon]

I have a question, how do you calculate your roll center and the best ways to lower it. I know you can lower your motor and gat as much weight down low but can you lower it with A-arm geometry?

[PBFAB.COM]

Originally Posted by wickid demon

I have a question, how do you calculate your roll center and the best ways to lower it. I know you can lower your motor and gat as much weight down low but can you lower it with A-arm geometry?

The roll center is a product of the suspension geometry.... so any changes to it are done my modifying the suspension design.

Lowering the motor will lower your center of gravity.

[wickid demon]

Brain fart I ment center of gravity. I knew the roll center would be effected. Let me try again center of gravity?
Posted via Mobile Device

[robnolimit]

Originally Posted by wickid demon

Brain fart I ment center of gravity. I knew the roll center would be effected. Let me try again center of gravity?
Posted via Mobile Device

CG is tough to calculate 100%, but you can get pretty close. You need to weigh the truck, and get the front/rear balance. Once you have that, you can get a close estimate. Lets say the truck has 57% front weight, then the front-to-rear balance point is 57% of the wheelbase. The wheelbase is 114", so the balance point is 65" forward of the rear axle CL. (114" x .57) That gives you the front/rear line. You can do the same for side/side if you want to account for any weight offset there. For the hieght of the CG, in a car, you can use the cam centerline as an average, for a truck, it's cam centerline + 3". If you have four corner scales, there are programs, like from AutoWare, to nail it down. You weigh the truck on level ground, and then lift the scales on one side 10" and weigh it again. enter the weights, wheelbase, front and rear track width, and it will spit out the exact location.

[robnolimit]

Originally Posted by GEARBOXGARAGE

I've been following this thread for a while and have looked over the posts several times, but I haven't seen much of an answer to a topic that was covered around pages 8, 9, and 10. The topic was about anti-squat and that brought up the theory of swapping or changing the trailing arm mounts to reposition them higher at the crossmember. One member asked what a recommended pinion angle should be, but I seem to have lost the exact location of that post. Robnolimit, you comment that getting the right pinion anlge is free horsepower. Do you have a recommended pinion angle and could you give a little insight on if/how pinion anlge affects handling or perfomrnace?

Pinion angle is mostly related to the engine/trans. How the pinion angle moves, as the suspension moves, is related to the suspension geometry. Ideally, the Pinion angle should be parallel to the crank angle when the truck is at ride hieght at 60 mph. (it takes some suspension load to run a constant 60) So, if the eng/trans is set in place at 3* up in front, then the pinion should be 3* up in front. Now here's the catch, under load, the axle/suspension will rotate upwards. Trailing arms will go up 1/2 degree, 4-bars = 1 deg, leafs will go 1* to 1 1/2*. So depending on the suspension type, you need to set the pinion slightly lower so that it will rise up under load.

[jimmydean]

Nate, how about the cantilever setup? What are some of the advantages I will get with that? Will keeping it a longbed hinder the performance? I was considering a mid sized bed, I would rather not go full short since everyone runs short.

I ask here since others might benefit as well from your insight.

[robnolimit]

Originally Posted by jimmydean

Nate, how about the cantilever setup? What are some of the advantages I will get with that? Will keeping it a longbed hinder the performance? I was considering a mid sized bed, I would rather not go full short since everyone runs short.

I ask here since others might benefit as well from your insight.

I'll let Nate run with the Canti-lever set up on this one. As for wheelbase. shorter is better. Most pure roadcoarse racers follow the rule of WB = track width x 1.5. A C-10 will have a track O.D. of around 68", so 68 x 1.5 = 102" this would be the ultimate road racer C-10, but wouldn't haul much, and lok really goofy. From there, higher speeds = longer WB, lower speeds = shorter WB. Porsche 911 - 67"TW, 104 WB.

[PBFAB.COM]

Originally Posted by jimmydean

Nate, how about the cantilever setup? What are some of the advantages I will get with that? Will keeping it a longbed hinder the performance? I was considering a mid sized bed, I would rather not go full short since everyone runs short.

I ask here since others might benefit as well from your insight.

Rob... I still feel a little stange posting replies in your thread, and appreciate the fact that you have told me several time it doesn't matter... as long as it helps the cause! I just try to be as respectful as I can, and don't want to take away from all the time and energy you have spent sharing your knowledge with members of this forum.

Jimmy... there are a handful advantages to the rocker arm set-up, other than it just looking cool.... here are a couple that come to mind right off the bat.

- It can help in packaging the components when space is at a premium.

- It can allow you to change the rocker ratio and have infinite adjustment in spring rate. You can do all sorts of things by tweaking and changing the rocker arms and their geometry.

[jimmydean]

Thanks for the rule of thumb, Rob. I will play more with wheel base and as the build gets closer, Nate and I will work specifics. I was going with the C4 setup to keep with the theme of the build. But the more I talk to people, the more I am learning just how well this might work out.

I am not looking to race hardcore. But I will take it out and see what it can do against my buddies at some local events when its done next year.

[jimmydean]

The rocker ratio was my first thought, and I saw a post from Josh who had it on his custom frame (pic above). I am so giddy with anticipation.

Adding the adjistability of the select ride shockwaves make for some added refinement as well. I will play with wheelbase numbers and weight tonight.

[robnolimit]

Right you are Nate. The ratio is the big advantage. if you use a 4" stroke shockwave, and build a 1.5 ratio rocker arm, you would have 6 of travel available. Also, the 7000 series shockwave will yield appx. 350 lb/in spring rate at 75 psi. On the rocker arm with a 1.5 ratio it will net out at appx. 233 lb/in, which is right in the range you want.

Nate, one expert sharing his knowledge may be seen as opinionated. A group of experts sharing the same same knowedge will set the standards and help shape the future.

[GEARBOXGARAGE]

I see Hotchkis now has 2" front lowering springs, but at a 1500 lb/in rate. This seems kind of high compared to what has been mentioned previously in this thread..... Any thoughts?

[robnolimit]

This goes right to your "set up theory", or plan. you only get to choose one, no mixing to get good results. - 1)soft spring/big bar/low RC. -or- 2) stiff spring/soft bar/high RC. Now somewhere in the middle is med spring/med bar/med RC, but lets choose option 1 or 2. O.E. C-10 geometry nets a pretty high RC, as it should, it's truck after all. So it sort of forces you over to option 2. I have to say that for me, 1500 lbs seams stiff, but, depending on the shock and swaybar, it could work. Remember, if you drive it everyday, and it's not a dedicated weekender, you need to be comfortable in it too.

[GEARBOXGARAGE]

Rob - Yeah, it's more of a weekender and plan on hitting the local track occasionally. I would be matching up the rest of Hotchkis front end components and a custom coilover set-up out back using QA1 shocks all around. I don't mind giving up some ride quality for added performance. I noticed you used the MOOG bick block springs and just cut a coil off. Have you been satisfied with that result?

[robnolimit]

I am really happy with them, it yields appx 1200 lb spring rate, smooth and good handling. For a dual purpose driving, adjustable shocks can be a big help.

[Jonboy]

Originally Posted by robnolimit

I am really happy with them, it yields appx 1200 lb spring rate, smooth and good handling. For a dual purpose driving, adjustable shocks can be a big help.

Do you happen to have a part # for these?

[71shortwide]

awesome thread! Rob and nate and everyone else thank you for your i have learned alot about handling! I just cant make up my mind on my 57 truck or my 82 chevy!

[robnolimit]

hmm, the 9000 bags are 4.5" closed, 12" oper, spec ride height at 9" - 9.5". Oops, '7000' series, (1000 to 1200 lb cap.) they are 4" closed, 13" open, and 8" to 9" RH

[robnolimit]

Thanks, I was just going to post that.

[robnolimit]

As to welding on a swaybar, I am not for it, if your talking about it welding anywhere in the center of the bar, such as narrowing the bar. But, if we're talking about cutting off the factory end, and welding on new tabs for the link, then it's OK in my book.

[INSIDIOUS '86]

Originally Posted by robnolimit

As to welding on a swaybar, I am not for it, if your talking about it welding anywhere in the center of the bar, such as narrowing the bar. But, if we're talking about cutting off the factory end, and welding on new tabs for the link, then it's OK in my book.

A sway bar is basicly a torsion bar or uncoiled spring. By welding on a part that twists like the middle or on the bends can compromise the bar and change how it acts or cause it to break.by welding tabs on the ends there shouldn't be an issue with compromising strength as long as the welds are strong, since tends go up and down and there is hardly any twisting action.

Any issue with what's stated above?
Posted via Mobile Device

[Matt R]

Originally Posted by robnolimit

As to welding on a swaybar, I am not for it, if your talking about it welding anywhere in the center of the bar, such as narrowing the bar. But, if we're talking about cutting off the factory end, and welding on new tabs for the link, then it's OK in my book.

Cool that will be a great tuning tool to put in the tool bag!

[duallyjams]

I have a question regarding the track bar , I don't see anyone using a wish bone instead.

[robnolimit]

I have to agree with that. - better stated than me, thanks.