Make it handle

[robnolimit]

Ha, Good question. We used to make a coil-over kit that was similar to this (thats where some of the inspiration came from), but due to low sales we dropped it. The only difficulty with mounting on the forward side, to gain leverage, is that there is no room to put the dang thing. Our thinking here is that a lot of trucks already have dropped springs and/or blocks, and they just need some help to make them ride and handle better.

[N2TRUX]

Great product Rob!

I have heard of running "hot laps" to test a suspension, but isn't this bit excessive...

[robnolimit]

Lets talk about CASTER. Caster helps your truck turn, and stay straight. It's sort of like "rake" on your bike. This "rake" is the line through the center of the upper and lower ball joints, as viewed from the side. "0" caster would have the upper and lower ball joints directly level - up and down. If the upper ball joint is in 'front' of the lower, this would be "negative" caster, and we don't want that. As the upper ball joint is moved 'back' from the lower, that creates "positive" caster. - that's a good thing. Now, for '59 and older trucks, this means you need to look at the IFS kits your using/thinking about. Those who are still making IFS kits with 1* or 2* of + caster are stuck in 1979, and that 15" is a big wheel, - and a 60 series is a wide tire. So, ask them before you buy. If you already have one, and it tends to "nose in" to a hard corner, your best bet is a custom upper A-arm to move the upper ball joint back. If your interested in this type mod, let me know, and I'll put up some info. For '63-'87 trucks, if your working with the stock stuff, it may be a bit of a different choice. These trucks already have the wheel too far back in the opening. So, moving the upper ball joint back wil make things worse. I know that Porter's Dropmember & arms address this, as do Ride-Tech, and Hotchkiss. But all of the others that I have tested seem to be on the stock geometry plan. (Before you *****, if I didn't mention your parts, and you think they are better than others, contact me with the info) Noting the wheel placement issue, the answer seems to be to move the lower ball joint forward - appx 1 1/4" would be nice. So, aftermarket A-arms, or modify stockers.I'm going to modify a set of lower arms for our '72 JT next week. I'll put up some picts and show you what I've done.

[dirtball]

So......did you make it out to test the JT last night with the new rear shock kit?

[Conundrum]

Originally Posted by robnolimit

Noting the wheel placement issue, the answer seems to be to move the lower ball joint forward - appx 1 1/4" would be nice.

So how far will this move the wheel? 1/2 the amount that you move the balljoint? I would imagine it would be dependent on which spindles you use correct? Whether you are using stock, 2", 2 1/2", or 3" drop spindles, that will change that amount although a very small amount maybe?

[gringoloco]

Originally Posted by Conundrum

So how far will this move the wheel? 1/2 the amount that you move the balljoint? I would imagine it would be dependent on which spindles you use correct? Whether you are using stock, 2", 2 1/2", or 3" drop spindles, that will change that amount although a very small amount maybe?

Right on all accounts. With a 2.5-3" drop spindle, you should expect in the neighborhood of half since the spindle stub is closer to centered between the balljoints. Stock height would be slightly more since the movement would be closer to the wide end of the imaginary triangle drawn by the balljoint positioning.

[gringoloco]

Originally Posted by robnolimit

...the answer seems to be to move the lower ball joint forward - appx 1 1/4"...I'm going to modify a set of lower arms for our '72 JT next week.

Is this where the custom steering linkage and heim joints become a necessity? Or do you anticipate being able to gain some caster while utilizing stock steering components?

[robnolimit]

With stock steering, the inner TRE pivit is too high. Computor analisys shows it should move down about 5/8" to help eliminate bump steer. We usually focus on the inner TRE, because moving the outer TRE means modified spindles. - (or rod-end type and other mods)As luck would have it, "tipping" the spindle to gain + caster will also raise the outer TRE, so this could easily turn out to be a 'win-win' mod.

As far as wheel position, with a dropped spindle, the wheel will move about 1/2 the distance of the LBJ. So if we move the LBJ forward 1 1/4", the wheel will move about 5/8". Yes, different drop or stock spindles will move a different amount. The more the drop, the less the wheel will move.

[gringoloco]

Is the 5/8" at stock height, or with lowered springs? Or do lowering springs even affect this measurement? Any worrries of binding the TREs with the spindle tilted? What mods do you anticipate having to make to the LCA?

Thanks for the info, sounds like a cool idea.

[robnolimit]

Spring hieght does not come into play, as there is very little caster gain in these trucks, the CL moves almost straight up as the suspension moves. Tre's wont have any binding with this mod. I'll put up picts and specs for this one next week.

[SCOTI]

Thanks for all the info sharing BTW.....

[gringoloco]

Originally Posted by SCOTI

Thanks for all the info sharing BTW.....

No doubt. Very informative. Always interested to see what's next with JT and this thread.

[Conundrum]

Originally Posted by robnolimit

With stock steering, the inner TRE pivit is too high. Computor analisys shows it should move down about 5/8" to help eliminate bump steer. We usually focus on the inner TRE, because moving the outer TRE means modified spindles. - (or rod-end type and other mods)As luck would have it, "tipping" the spindle to gain + caster will also raise the outer TRE, so this could easily turn out to be a 'win-win' mod.

So I guess if you cut 1 1/2" out of the crossmember, it will put you back to needing a custom center link? If it turns out that "tipping" the spindle helps with the TRE.

[robnolimit]

Yes to the last post.
As some threads are talking about camber, caster and bumpsteer, It seems this is a good time to shed some light here. 1. Anyone who claims "NO BUMPSTEER" is full of steer stuff (b.s.) So. we need a way to compare bumpsteer. Some use degrees of steering, and some use a dimension. You can convert one to the other with some trig., but it's not really needed. Unless you have a laser rack, and lots of other toys, we'll talk in dimesion. What were trying to find out is HOW MUCH does it turn during the travel? and does it turn 'in' or 'out'? Most racers and chassis builders use a 'toe plate' and some dial indicators. The typical toe plate is 20" wide and 6"+ tall. We have a "floating" guage stand which is a bit easier to use. Once set up, you chart total toe movement for every inch of travel. We typically test + or - 3" from RH. The goal is to be less than .1" of bumpsteer per 1" of travel. Of coarse, the lower the better. When you first look at the chart it looks really bad, but look at the scale. Each 1/4" on the bump scale = .020" . To the right on the chart is a 1 to 1 drawing, as you can see, it's very hard to compare changes this way. In 3" up compression travel we have .173" on bump 'in', and in 3" of droop, we have .148" of bump 'in'. An outside average of .058" per 1" of travel. If you converted this to degrees it would be .163 degrees per inch average. Just so you know, the first pict, and graph are tests on our C-10 R/P kit. Bech testing is easier than on the vehicle, but it takes about 1 1/2 hrs to set up, the 20 min to chart. Each time you make a change, you start over. Fun stuff, but it pays off.

[tubbedII]

So, .058" per inch is well under the goal. Did you guys happen to do the same tests to the stock steering to find the difference? Also, were there any other mods for caster already done during this test or does that not effect on bump steer?

[robnolimit]

The test I did here is using a stock 72 crossmember, spindles, and Ride-Tech Strong Arms. I tested our rack with this crossmember and stock arms also, and was able to get similar results. The Ride Tech arms change the caster, once aligned (camber and toe to 0), I got 7 1/2 deg of caster. Stock arms gave us 2 deg. As the camber increases, (the spindle is tipping back) the steering arm raises up. This change in the hieght of the TRE will change the bumpsteer curve. I have not yet tested a stock C-10, but we will soon, and I expect it to be a bunch. If we put a jack under our JT and lift it up you can watch the wheel turn out. - not good.

[aggie91]

Originally Posted by robnolimit

... The Ride Tech arms change the caster, once aligned (camber and toe to 0), I got 7 1/2 deg of caster. Stock arms gave us 2 deg. As the camber increases, (the spindle is tipping back) the steering arm raises up....good.

I am I missing something here, or should that last part be "As the CASTER increases," and not camber??

I am really learning alot reading this thread and enjoy it!

Thanks Rob!
Posted via Mobile Device

[robnolimit]

Oops, right you are, "caster". - long day.

[afmdmc]

Originally Posted by robnolimit

New...1963-72 Chevy Pickup Rear Shock Kit
NO LIMIT ENGINEERING
New Rear Shock Kit to fit 1963-72 Chevy Pickups!! - I'm feelin pretty good about this. After dropping another 2" in back, we ran into the same trouble as everyone else. The shock issues. After researching the other kits, and solutions, and thinking about it, we came up with a plan. Here are some of the problems we noted. 1. No room for a longer shock, even with reworked or 'dropped' mounts. 2. shock angle gets worse, the lower you go. 3. If we go another 2" (8 total) we're screwed again. 4. the exhaust is a nightmare. 5. the inboard shock design doesn't handle that great. With this in mind, we set out for a fix. This is the whole idea behind the JT, to come up with tested components that WORK, and will HELP get more trucks on the road to be enjoyed.

ok so i really like the looks of this setup. i went to your website and couldn't find them. do i just need to call or can you give us the part #. also the panard bar in your JT build is pretty cool also. and thanks for all the info.

[robnolimit]

Yes, for now, just call and ask. Thanks.

[skoffice]

Rob, thanks for the bumpsteer lesson! You break it down really well, making it easy to understand. I'd be interested in seeing the comparison to stock suspension. Does the curve usually stay pretty similar for droop vs. compression, or would that depend on ride height, correct? Also, what rack are you using on the setup you have in the pic? Thank you for sharing your knowledge!

[52 choptop]

Rob, Great advice. I moved the upper shock mounts outward as far as I could with still staying inside the leaf spring. They were about 6" apart, now with the new mounts welded in they are a good 3' apart. Threw in some Monroe coil overs a buddy had still new in the box to try it out. What a huge difference. So no I'm ready to order some from you (the Monroes were the test shocks). What info do you need? Let me know, and thanks again.

[robnolimit]

That rack is from a Izusu commercial, but we are looking at others, that one has difficulties with the fitting placement.

For shocks, you can just give us a RH measurement. Glad it made an improvement.

[triophan]

I've read and re-read the majority of this thread. I'm planning my truck (its slowly converting itself-I swear- to a toy instead of a DD).
I know, when it comes right down to brass tacks, I'm trying to make a farm tool race/make handle.
Rigidity and weight reduction/re-allocation are my primary concerns since I'm trying to shave as much weight (Power to weight ratio is improved something to the effect of +10 to 15 hp if I drop 150-200 on my 5K lb truck) and these (73-87) frames are not the best in the world for rigidity (don't even hold under the pressure of the steering box pushing offroad tires sometimes).

My question is, and I know its first-grade stuff, but what would be the suggestions insofar as weight transfer, distribution, as these trucks its about 55/45 (under the most optimistic assumption).

I've not started building my suspension, because I know that those upgrades will respond MUCH better to a frame/truck built with some minor changes. Sorry for the long/elementary question... just curious.

*also, since I may be stiffening the frame, would it do me any good to drop the cab/front end an inch? I think I've got enough room to drop the cab mounts and the core mounts an inch, I could avoid dissasembling the ENTIRE truck to shave out the crossmember. "moving the weight I have lower in addition to lowering suspension..."

[robnolimit]

Triophan, I'm currently working on the JT chassis. - we bought an 'un-bent' frame for $300. to work on since the JT frame is a bit twisty. I'll put up basic chassis prep picts next week, and i'll also try to get the JT on the scales soon. The total wieght is 3820, small block, 4-speed, ft disc, p/S, P/B.