Make it handle

[robnolimit]

Start with the top pict, #1. This is my best wat to show how the camber and Instant Center move, as the suspension is compressed. (outside tire in a turn). The black line is at Ride Height, and shows the position of the Instant Center. When the suspension is compresed (pink lines) note the the angle of the spindle changes - the camber increases. Also, the IC moves in and down.

Pict #2 shows the same base comparison, but with the upper A-arm raised at the ball joint. Because this makes the two ball joints farther apart, the upper arm starts farther up on its arc. And when the suspension compresses the same amount, the spindle lays over a bit farther, giving more camber change. Also, the IC is is in a different place. And although hard to see, it doesn't move as much as before.

Pict #3 is a base graphic of the A-arm arc. Both arcs, yellow and pink, are 20 deg spreads. You can easily see that by starting farther up the arc, the lateral movement is increased. - good for the upper arm, - bad for the lower.

[69gmcc10]

Thank you so much for explaining that! This thread is one of the best parts of this forum! Thanks for sharing your wealth with us, this is the most valuable thread on this forum. Do you sell the raised ball joints?

[robnolimit]

Originally Posted by 69gmcc10

Thank you so much for explaining that! This thread is one of the best parts of this forum! Thanks for sharing your wealth with us, this is the most valuable thread on this forum. Do you sell the raised ball joints?

Thanks a bunch. Just trying to elevate the truck world. Best place to buy is Speedway Motors, Howe Racing, or Stock Car Supply. Ask the techs about them. Howe and Afco also have adjustable (built with a monoball and stud) as well as 'low friction', but these types have a short lifespan - 3 to 5 k miles.

[robnolimit]

Just thought of this. The same gain can be made by lowering the inner pivit shaft for the upper A-arm. This was commonly done in road racing. Known as the 'Shelby mod' on mustangs, or the 'Guldstrand mod' on camaros. They did it by simply drilling new mounting holes a bit lower, and usually a little farther back for more caster.

[Greywolf200]

Back to 1/8" toe out. You said that on JT 1/8" toe out would give better turn in. Is this applicable on other A arm suspensions. The toe at max turn on my 80's Caprice causes a really bad scrub, would 1/8" toe out help here?

Thanks,

[robnolimit]

Originally Posted by Greywolf200

Back to 1/8" toe out. You said that on JT 1/8" toe out would give better turn in. Is this applicable on other A arm suspensions. The toe at max turn on my 80's Caprice causes a really bad scrub, would 1/8" toe out help here?

Thanks,

My guess is that the Caprice suffers from GM's backwards acreman geometry. So, the outside tire turns sharper (tighter radius) than the inside tire. This is easy to see, just park on level ground, turn the wheels to full lock, and walk about 30 feet in front of the car. Try to position yourself between the paths of the two front tires, kneel down and have a look. The outside tire will be turned in farther than the inside tire. Scrub-scrub-scrub. Try a little toe out, it will help above 20mph, but there is no escaping the scrub in a parking lot at the mall.

[Ackattack]

WOW is all I can say. I read through the 33 pages of post over the last day. WOW.

Where was this thread and wealth of information when I started building my 68, "Bruiser", in 2007. I guess I was ahead of my time applying the pro-touring concept to a truck. I had been reading on pro-touring.com and considered doing a 1st gen camaro, but what can I say, I'm a truck guy. Previous to building my 68 I had read Herb Adams book as well as a few others, and my complaint was that all the suspension stuff for our trucks was geared towards lowering them, not making them handle. I guess times are changing

I guess during my build I never thought too much about modifying what was there (at least too much).

Luckily, after reading through this novel I have gained a lot of insight as to what is now available for our trucks and some ways to modify what we already have. I'm a little slow to this section as of late since my focus lately has been on my other truck and just trying to get it to be a reliable, cool looking daily driver.

At the goodguys show in KC, I thought of taking my truck out to the autocross course, but the brakes need some work. I have tried a few different things with little gain. I think I'm going to clean up the rotors and put new pads on it....hopefully that will solve the problem as I think maybe my pads may have gotten messed up from improper break in, or something.

Based on reading through all of this, it looks like I did some things good (fuel tank in the back, battery in the back, slightly lighter engine (5.3L), rear swaybar (f-body), "OK" shocks) and could probably improve on some things. My biggest complaint about my 68 is that the steering is SO light on the highway just going in a straight line. I assume this is due to having little to no caster. I'll add that to my winter to do list. I'm also going to bite the bullet and move the engine back and lower. I probably have a good 3" from the back of the valve covers to the firewall. Guess I'll have to have a new driveshaft made and make new motor mounts....oh well, it will keep me busy.

Reading over the entire thread I see one common thing. No where does any one mention the "driver mod". Back in college I did a fair amount of autocrossing (LS1 f-bodies) and while its fun to blow money on parts to make you car faster, learning to be a better driver is just as/if not more important than the car itself. For me, other than attending some autocrosses and being in an autocross club where we discussed driving techniques and stuff I haven't really had the chance to do the driver mod. I know there are some course (can't think of the name of them) that will teach you how to be a better driver.

One other thing, on the JT build thread there was mention of using a couple of switches to trick the tranny into staying in gear and keeping the converter locked. Can you go over this a little more? Is it possible to do the same thing (or similar) with tuning? How does it work if, say you spin out and come to a stop with the converter locked up, does the engine stall out?

Again, awesome thread. The sharing of your knowledge and experience is great!

[robnolimit]

Ackattack glad you made it through all this. Yes, some caster will help. You really should go out and try the autocross at a Goodguys event, it's a bunch of fun. As far as the 'driver mod' I agree 100%. But, I'm not the guy for that thread. I have a tough enough time getting around the coarse myself. It would be nice to get Mary Pozzi or Mike Meyer to chip in, but honestly, there not into trucks to much. Here's a laugh. In Columbus, I was watching one of the vendors run, in a car that I considered to be a 'bad choice' for autocross or short coarse competition. He loves the car, but I thought, still not a great choice. Then, I walked back to our pit area and realized that I built a TRUCK. What a bonehead! Lesson learned. Build whatever turns you on and have some fun.

[danielhaskins336]

Hey rob I was wondering if you will do alignments in your shop?
Posted via Mobile Device

[robnolimit]

Originally Posted by danielhaskins336

Hey rob I was wondering if you will do alignments in your shop?
Posted via Mobile Device

Sure, by appt. We are open sat from 9am to 2pm, that seams to be most convient for alignments.

[bo-w]

Originally Posted by robnolimit

Ackattack Here's a laugh. In Columbus, I was watching one of the vendors run, in a car that I considered to be a 'bad choice' for autocross or short coarse competition. He loves the car, but I thought, still not a great choice. Then, I walked back to our pit area and realized that I built a TRUCK. What a bonehead! Lesson learned. Build whatever turns you on and have some fun.

Rob You do realize that this is why we are all reading this performance handling thread on a TRUCK forum lol . we are ALL in the same boat here !! thanks again for the amazing insight and tech on this thread

[SCOTI]

Originally Posted by bo-w

Rob You do realize that this is why we are all reading this performance handling thread on a TRUCK forum lol . we are ALL in the same boat here !! thanks again for the amazing insight and tech on this thread

Exactly his point..... these are trucks!

[Ackattack]

I was just looking at ridetech's website and in their complete suspension package: http://www.ridetech.com/store/suspen...0-level-3.html

they include tall spindles. Then, when you click on the "included" tab, it shows standard spindles. I didn't see any more on thier website on the tall spindles for our trucks, but would be interested in learning more.

[robnolimit]

Originally Posted by Ackattack

I was just looking at ridetech's website and in their complete suspension package: http://www.ridetech.com/store/suspen...0-level-3.html

they include tall spindles. Then, when you click on the "included" tab, it shows standard spindles. I didn't see any more on thier website on the tall spindles for our trucks, but would be interested in learning more.

Looks like I need to call and rag on Tony (web content isn't his job, but he needs to catch all the crap) The description is somewhat generic, those are 'A' body spindles, not C-10. As far as I know, no body makes a tall spindle for a truck. But i'll keep a lookout at SEMA.

[Ackattack]

Originally Posted by robnolimit

Looks like I need to call and rag on Tony (web content isn't his job, but he needs to catch all the crap) The description is somewhat generic, those are 'A' body spindles, not C-10. As far as I know, no body makes a tall spindle for a truck. But i'll keep a lookout at SEMA.

darn it

[FRENCHBLUE72]

Hey rob I just finished the article street trucks did on you very nicey done.. I have a question about a watts link set up.. Does it matter how long the arm is for the center pivot? I know it should be centered on the rear end but how long(or tall) per say should that center bar be? I hope I explained that right...

[robnolimit]

Originally Posted by FRENCHBLUE72

Hey rob I just finished the article street trucks did on you very nicey done.. I have a question about a watts link set up.. Does it matter how long the arm is for the center pivot? I know it should be centered on the rear end but how long(or tall) per say should that center bar be? I hope I explained that right...

I getcha. The rule on a watts is even and parallel. Usually the center pivit link is 3" to 4" from center pivit to the link mount hole. The two links MUST be the same length. AND, they must be parallel at the point where the center link is centered between them. Hope that was clear?

[shawnr21]

Man, It only took me a week and a half to read this thread.

Just a thought I've had while reading all this. I think all of Robs recomendations are awesome and maybe a bit modest. I can really appreciate a humble guy, no **** talkin, just go out and prove it on the track. I've been looking for the right rear suspension for my truck for the last few weeks when a friend pointed me to this thread. I ordered a fatbar kit from Rob last week and think he is the type of guy I want to support. He is supporting all of the forum members with all his insider info!!!

Awesome work Rob!!!

Now, I do have another question that I havent seen any talk about. Sorry to derail from the suspension geometry but i'm wondering about rearend differentials. I've read that an eaton posi unit possibly breaking loose on exit and that a truetrack is more suited to accelerating out of the corners. Anyone care to give their opinions on this? Rob, do you mind sharing what your trucks have?

Thanks

[robnolimit]

Originally Posted by shawnr21

Man, It only took me a week and a half to read this thread.

Just a thought I've had while reading all this. I think all of Robs recomendations are awesome and maybe a bit modest. I can really appreciate a humble guy, no **** talkin, just go out and prove it on the track. I've been looking for the right rear suspension for my truck for the last few weeks when a friend pointed me to this thread. I ordered a fatbar kit from Rob last week and think he is the type of guy I want to support. He is supporting all of the forum members with all his insider info!!!

Awesome work Rob!!!

Now, I do have another question that I havent seen any talk about. Sorry to derail from the suspension geometry but i'm wondering about rearend differentials. I've read that an eaton posi unit possibly breaking loose on exit and that a truetrack is more suited to accelerating out of the corners. Anyone care to give their opinions on this? Rob, do you mind sharing what your trucks have?

Thanks

Thank you all very much. Glad we can help out. The Bullet has a true Track, and I like it, no problems. I have used Lockers and track locks in the past. Tack locks are smooth, but have a 20000 mi. lifespan before needing to be rebuilt. Detroit lockers are great for the drags, but not so smooth on the street/or roadcoarse. - But, D.L.'s are bullitproof. The J.T. has a 'Lockrite', and inexpensive locker. It works pretty good, but it clicks at low speed in parking lots. I'll be in Vegas at SEMA all week, and going to learn about 'Wavelock' and 'Black Gold' diffs. I'll let you know what I find. Check our facebook at www.facebook.com/nolimithotrods We're going to put up live SEMA feeds wed/fri, and Optima feeds on sat.

[Greywolf200]

Horsepower TV did a program on ProTouring/Autocrossing. The event was at Nashville Speedway. While all of the action shots were various cars, several times they showed a really nice dark green '67 C10 that was on the ground. I guess autocross is getting more popular.

[robnolimit]

Originally Posted by Greywolf200

Horsepower TV did a program on ProTouring/Autocrossing. The event was at Nashville Speedway. While all of the action shots were various cars, several times they showed a really nice dark green '67 C10 that was on the ground. I guess autocross is getting more popular.

Man, I missed it, hope it replays. The green truck is Mark Turner's. we saw it in Texas in the spring. Brian finch helped with the build. Turner has contacted us about a new C-10 chassis for the next truck build - he's got the bug. He also has a bad a$$ vette and camaro. -and he's a really nice guy.

[robnolimit]

The rumor is that the coverage of the RTMC (Run to music City) was a test to find out the interest level. There may be coverage next year of a 9 event series. We'll have to wait and see.

[SCOTI]

Originally Posted by robnolimit

The rumor is that the coverage of the RTMC (Run to music City) was a test to find out the interest level. There may be coverage next year of a 9 event series. We'll have to wait and see.

Is this silimar to the RTTx events (Run To The Coast, Hills, etc...)? I went to a RTTH event a couple of years ago & really enjoyed it.

[BMERDOC]

Rob asked me to post some pointers about rear thrust angle, toe and camber in my alignment thread. While walking mindlessly with the kids Trick or Treating tonight I thought it may be proper to cut and paste it to his thread too...


Per Rob's request:

I'll try to make this simple. Thrust angle is the relationship between the rear axle and the centerline of the chassis. As I had stated before, Thrust should be zero. If the centerline of the axle is 90* to the centerline of the chassis it will be zero. Just like the front toe, toe out is negative and toe in is positive. If the thrust angle points to the left of the chassis centerline the thrust angle is negative, to the right, positive. This angle is the average of the two rear toe angles which is not to be confused with total toe which is, well, the sum of the two toe angles. If the thrust angle is negative the truck will want to rear steer to the left causing the truck to want to go right. You would have to add constant left hand input causing the "dog tracking" look. Of course, the opposite would be true if the thrust angle were positive.

Camber can have an effect on tracking too. No matter wether its front or rear. Lets stick with rear camber. A vehicle will tend to steer toward the more vertical or positive cambered tire. Lets try a small quiz...if my left rear camber is 0* and my right rear is negative .75* which way would the rear of the car wanna steer?....
....
....
If you said left then you are correct. It would want to rear steer left and you would have to steer left to cancel it out. Both camber angles must closely match so as to not cause a "pull" or "drift".

Caster has NO affect on the rear axle...unless, in the off chance, you have a four wheel steer car. If that was the case it would closely follow the rules of front caster. Although I won't go into 4W steer it did remind me of a good point.

Rear angles have a greater effect on how a vehicle tracks. Anyone who has driven a forklift knows they can be very twitchy.

[robnolimit]

yes. same thing. We went to RTTC, run to the coast.It was a great event. Autocross, speed/stop, and 2.2mi. roadcoarse. It was cool to see some cars excell in one event over another, and the few cars that could do it all.