Re: Make it handle
 

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.

Re: Make it handle
 

Great product Rob!

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

http://67-72chevytrucks.com/vboard/a...1&d=1296934939

Re: Make it handle
 

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.

Re: Make it handle
 

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

Re: Make it handle
 

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?

Re: Make it handle
 

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.

Re: Make it handle
 

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?

Re: Make it handle
 

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.

Re: Make it handle
 

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. :cool:

Re: Make it handle
 

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.

Re: Make it handle
 

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

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

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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.

Re: Make it handle
 

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.:smoke:

Re: Make it handle
 

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?

Re: Make it handle
 

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.

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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

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

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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.

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

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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!

Re: Make it handle
 

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.

Re: Make it handle
 

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.

Re: Make it handle
 

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..."

Re: Make it handle
 

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.

Re: Make it handle
 

A buddy of mine has a spare '78 frame I may be setting out in the shed to do some work on... Figured I can square and level it with scissor jacks (pick up at junkyard for $5 ea) and let the reinforcing begin!

Only problem I could forsee would be the fact that I would have to run out to my truck every 5 seconds to measure parts clearances, etc. You should have your own Sub-forum, with projects, Q&A, haha... might be too much for one dude though. Keep me posted! Thanks

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Well, I started to right a heavy rant, then i stopped, I'll save that one for later. :lol: Lets talk sway bars. - anti-roll bars. The idea here is that this bar can add roll stiffness by transfering spring rate from the inside spring to the outside spring in a corner, without making the straight line ride harsh. For years we have said that sway bars are the best 'bang-for-buck' you can spend on suspension. - Still true. A swaybar's stiffness depends on material used, diameter/or/wall thickness for solid or tube bars, width between pivit mounts, length of the arms, and mounting link style and location. - lots of factors. It's easy to see that a thicker bar is stiffer than a thin bar, givin the same shape and material. Tube bars (hollow), are usually a better grade of alloy steel, so a 1 1/4" x .250" bar may be stiffer than a 1 1/4" solid, but not always. Manufacturers of quality bars should be able to provide sway bar "rate" info. One thing to be aware of is the sway bar link. This link connects the bar to the suspension. (this is going to get close to my rant topic) Think about the front bar on a C-10. The factory bar was connected to the arm with a bushing and strap - NO MOVEMENT. The bar pivits on an arc that moves front-to-back as it moves, and the A-Arm moves on an in-to-out arc. So, as the suspension travels, the sway bar is being pulled in and out, and the A-Arm/busing is being twisted to match the bar angle. Doesn't sound to good does it? Now, the stock pivit and arm mount bushings were pretty soft rubber, so it wasn't so bad, and it was cheap for GM. And, it was 1966 when the first oned rolled out. (bias ply tires, 8-tracks,...) Now, a lot of aftermarket suppliers have bigger 'performance' bars, in urathane bushings (stiffer) and the binding is WORSE. Making the suspension less consistant. Yes, the roll stiffness is greater, but the suspension is less consistant/predictable. :sumo: Some, are going to a link connection to the arm with two rod-ends. That is a step up, but a small one. The 'average' rod end will swing 10 to 12 degrees, thats 5 or 6 either way, so with a short link these may bind up, and this type of bind may be a worse feeling than stock, and actualy reduce suspension movement. To make the link long enough not to bind, the sway bar would need to be above the steering links. No, you cant just rotate a stock style bar ( even one set up for a link) because the angle of the end would be wrong. Why don't 'they' make a bar like this? Well, to me, it looks like even the best performance bars are a copy of the original bar, with a hole in it for a mount link. To get what we all would really want, someone will need to study, TEST, and stop copying the stocker. which takes me even closer to my original rant. You would'nt take financial advice from a homeless person, or welding tips from someone who never welded. Why are we all buying parts from someone who hasn't built/drivin/owned one of the things were building? Crap, some of the rant got out. Sorry.:ito:

Re: Make it handle
 

I am rebuilding a 1969 K20 and I want to soften the ride some. I see that you can order 4, 5, or 6 leaf replacements for the leaf springs. Presently it has 6 leafs can I just remove 2 or 3 and put airbags to make up the difference and if so how do you set them up to make sure you get the best ride along with the ability to carry a load once in a blue moon.
West

Re: Make it handle
 

Rob...love reading your posts. They are one of the most informative ones out there and it's like reading a great blog. About these sway bars and the issues you are seeing with C10 versions...tell us you are working on a solution!? Your list is getting good: rear shock mounts [done], longer track bar [done], bolt in r&p [pending], lca caster mod [pending], sway bar [maybe?], rear sway bar [would love to see].

Re: Make it handle
 

x2.
Rob, you sir have my utmost respect.

Re: Make it handle
 

Jeez I thought you said you weren't going to rant! But I'm glad you did and I agree! Often I had wondered how they determined what a "general" rate would be for an "upgraded" sway bar. Also how consistent a solid bar would be vs. a hollow one. I've been looking at Schroeder sway bars online, hollow with splined ends and arms. You probably know of them since they're out of Burbank. It seems like a MUCH better approach, but I have no clue how to determine what rate, arm length, bar diameter etc. Seems like it could be fairly easy to bolt the bushing mounts to the bottom of the frame and check different bars and adjust the different arm lengths. Test time for JT!?

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WEST9378 - Try to stick with a reasonable aproach, and you'l get good results. If you start with the leafs, lets say that the top spring with the eye is #1, and the count down from there to the shortest #6. Keep 1,2, & 3. pull #4, keep #5, pull #6. Use a hand gringer/sander to round off and radius the ends of the springs. Get some teflon liner to put between the leafs (speedway, Eaton, ..) and reassemble. Call Helwig and get a 1" rear sway bar. From RideTech, use pt # ARK2004, with a shrader fill kit. But here's the catch, when you get it done, you have to post up the results. OK?
I have some more to post up later, but i have a deadline to meat this morning. Have a great day all.

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Welcome March Madness. last weekend we attended the "Run To The Coast" event in El Toro, Ca. RTTC is a pro touring tri-athelon of sorts, with an autocross, a speed-stop, and a 1.8 mile road coarse. We ran the 'Bullit and had a great time. Only two ther trucks in attendance of the 70+ competetors, Rob Phillips - Hotchkis 69 C-10, and the Magnaflow 37 chevy. Once stats are released, I'll post them up. Show season starts soon, and that means more racing for us. - I'm ready to go. Weight is becoming our limiting factor. 1. Trucks have a naturally high CG, hey there trucks, if not they would be just cars. 2. there nose heavy, again, there trucks, its in there nature. 3. there just heavy. We're at 58.7% ft weight on the 'Bullit, which is not good, but better than the 59.6% it used to be. So keep this in mind. Move everything you can, DOWN, and BACK. Now, get in the garage, and get ready for the upcoming season. See you somewhere.

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Yeah G force, its actually not necessarily the force holding a tight corner. Keeping you in the seat of your truck, its the equal and opposite force of gravity pushing you down back unto earth as for the faster you increase your speed. The more gravity is going to push back against you depending on your trajectory and angle of tract.

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Hmmm, OK, Gravity is pulling down on you, or your truck, with the force of one G. That is a static force. In a corner, centripedal, or lateral force is created when the vehicle turns. If the truck (car) was perfectly balanced, and the tires kept the contact patch perfect, then at 1G lateral it would slide sideways as soon as it overcomes 1G of natural gravity. Just remember, gravity sucks. lol. only through downforce created by air, or a bank in the corner is it possible to pass up 1G lateral (in a car, on pavement.) ;)

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Today we're heading to Scottsdale, Az, for the spring Good-Guys show. I'll snap some picts of cool stuff for you. Hope to run into Nate Porter and chat suspension and stuff. We'll be autocrossing the 'Bullit, so stop by if your in range. This is usually a really fun show.

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good luck it would be a blast to watch u thrash on the truck.

Dave

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Rob, I loved seeing the shots of your Bullit tearing up the course in the Trucks Throwdown (or whatever they called it). Based on your lap times, it sounds like you have it pretty well dialed in. Nice work!

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Quick update. We are victorious again! By the lunch break on friday, we had set the fast lap. Not just for trucks, but for EVERYBODY. As the racing continued, we pushed our numbers down even farther, and no one ever caught us. First Truck Class win of the season, and the overal fast lap (first time I've done that). I'll get some picts and video up soon.

Re: Make it handle
 

Congrats Rob,

looking forward to seeing some video.....