Re: Make it handle
 

Thanks for the tips on that. I've got a notebook with all of my scribbles on those, and Herb's book is sitting next to my bed. That computer program sounds great, I'll pick that up and start playing with that. Its a huge help, so thanks for the tips, I'm sure I'll have more questions along the way, but its a great place to start learning more.

Re: Make it handle
 

Here's a quick lesson we learned, or re-learned last night. We have a local road coarse that runs 'time-attack' on tuesday nights. It's a great place to test, and a heck of a lot of fun. A frustrated group with a pretty nice 32 roadster were unhappy with its handling, and set out to fix it. - Its a good runner, and it handles well. They unhooked the rear swaybar, AND make a big change in brake bias, shutting down the rear brakes as much as possible. Next run they spun the car into some tires, and ground it down the track curb. Scuffed paint, tweeked fender tip, (slight), and a tore up lower A-arm.
Lesson 1: ONE CHANGE AT A TIME
Lesson 2: DOCUMENT YOUR CHANGES - AND THE RESULTS
Lesson 3: FEEL THE CAR OUT AT LOW SPEEDS FIRST
I know not everybody has a test track available, but you can lay out a test run area on a back road. As you run it, note your speed or rpm through different areas, check tire temps at the end of a run. We use a hand help heat gun. check the temps at the center, and each side of the tread (inside/ouside) Compare your temps. Hot in the center - too much air. Cool in the center - low pressure. Lets say temps run 122 outside, 128 center, 136 inside. - too much neg camber. This is a great tuning tool. give it a try.

Re: Make it handle
 

Did you do this backroad testing between the pizza place and the house ? I remember the 46 really likes that road..... and I didnt believe you when you said that car is like a good horse and knows its way home.....:lol:

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hey, we made it home. that is a good test road. Waterman canyon is good too, but next time you're out here I'll take you out to Adams in the 'Bullit. We'll stop by Wally-mart and get you some depends first.

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Depends.... ??? why did you finally put carpet in that thing? ;)

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ttt......

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uppers......

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Uppers? Downers? white ones, red ones? what??? Ohhh, A-Arms. got it.

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Thanks!

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OK, so we finially figuered the video load out. Pretty cool. This was the winning run in Costa Mesa. A good teazer for ya.

Re: Make it handle
 

Fun stuff Rob, thanks for sharing. I noticed that it ran very flat through most of the course. Almost zero tire squeal until you drifted through the S turn.

Looks like a fun way to spend the day. Once I get my 77 back together, I'll have to give it a try.

Re: Make it handle
 

Yeah it was a lot of fun. We'll be at the Tx Goodguys in a few weeks, come by and see us.

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Sometimes a little drift is the fast way around, - a lot of drift is not

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should i get RideTech contingency? Nice sticker placement

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I think you should hit Tony up. I'm sure that would be good for a burrito at Ft Worth.

I'll be in Ft Worth as well, with the 77 in the Ride Tech display.

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Rob
Truck looked good going around the cones,we will be in texas as well
see you there.
Justin

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Justin- You guys bringing anything to run, or just coming as a vendor?

Re: Make it handle
 

OK class, todays topic, rear locators. I chose my words carefully. Diagonal locators, Panhard rods, Watts link, wishbone,...... there are many. More than one way to skin a cat. for street performers, I like a panhard rod. I know, many favor other types. I have two reasons. 1. K.I.S.S. - keep it simple stupid! - fewer moving parts, easy to set up correctly. 2. Panhard rods allow you to set the rear roll center, and adjust it easily, without a complicated formula. While we may think (dream) about a high roll center with a low center of gravity, we are playing with trucks, not corvettes. High roll centers on the back of a truck will help keep it flat, it will also keep it spinning around. :lol: The high roll center plan works if you have a low C.G. and close to 50/50 weight balance. We dont get those with a p/u. So, you need to create some "side bite" to keep it on line.The lower you roll center the more side-bite you create, thats a plus, also, the lower the R.C., the more the truck leans over (bad). Thats why you need to be able to test/tune. Here's some tips. Made your panhard rods as long as possible, this has less angle change and pulls/pushes the rear less side to side. (Radial Deflection) Try to keep the P.R. close to level at ride height. If you are building mounts, put two or three mount holes on each set of brackets - housing and chassis. Try to start with a centered mount (height) about even with the axle center (height). You can tame some of the induced roll with a sway bar, but this also reduces side bite. It's all a balance. some amount of body roll is OK, as long is you can tune out its bad and keep its good effects. In a truck, at some point you will have to rely on the outside tire to keep you on line, and the tire will be the limiting factor. The trick is to tune up to the ability of the tire, with just enough side bite to keep it stuck. :smoke:

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Did I go too fast on that one?

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Can you briefly explain what you mean by rear roll center? feel dumb for asking but I just want to make sure I understand what you are saying here :lol:

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Don't 'feel' dumb for not knowing; it's a good question.

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;) Not a problem. Sometimes I go by this stuff so fast I get lost myself. Lets start with "roll center" or R.C., or RC for us lazy ones. The RC is the point that the truck wants to pivit around. OK, may have lost ya. When you put your truck into a corner, there are all sorts of things happening. The laws of physics are acting out all at one time. And all of these forces add together to force the truck to lean over. The RC is the pivit point, and we can change it, a bit. If you think of a picture of a truck, from straight in front of it, you would see it the front view. If you could mentally 'cut the picture out' and then hold it with a tack, you can imagine rotating the truck around the tack - ya? if you put the tack between the front wheels, even with the ground, this would be a LOW RC. And, no matter where you push on the truck, it tips over easily to the other side. Now imagine the tack throught the mirror, at the top of the winshield, and if you push on most of the lower part of the truck, it leans the other way. A HIGH RC. Now RC is only important when you compare it to something, like CG (center of gravity) think about this as the center of mass, or the balance point. Front to back is easy to understant. its the balance point front to rear. But height wise, theCG is the point at which there is equal weight above and below. For a standard, most vehicle CG hieght is about the center of the camshaft. This is where the 'Push" comes from. Now think about it, the closer you 'push' sideways on the RC, the less our picture wants to tip, or lean. Sounds great - but, it doesn't force any tires onto the pavement. In the front, where there is a motor and other weight, gravity is helping to keep the tires stuck. In the back, no weight, so no sticky-sticky. So, in the back, if we get the RC lower than the CG, it will force the truck to lean, and put pressure on the outside tire "bite"
:smoke: I'm going to stop here. This is tough to describe without pictures. Let me know if this makes sense to you. RC and CG are pretty important if you want a good handle on this stuff. (pun)

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Excellent description for explaining the difference RC & CG can play on a truck vs. a car. I hope to see your rig go round & round @ GG's Ft.Worth.

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Had to read... and re-read... but got it! Thanks for the explanation. I'm going to be running a rear trailing arm set up and just trying to get a better understanding of how it all ties together, and get the most out of my ride!