Make it handle

[68Stepbed]

Great stuff!! I'm gonna have to go through and re-re-read some of this stuff to get a full understanding, but great info. My 68 handles really good as of now, but I want to start upgrading in the future to make it really hang some corners.

I really don't want to go with an airbag setup if I can keep from it. I really like THIS kit from Hotchkis, but apparently, so do they. What else is available for the 63-72 truck chassis? Links would be great.

What are some of you guys using? Can I see some pics?

I have a really good test track...er...road. I'm about a 30 min. drive from US129 aka "The Dragon". I'm definetly gonna try the checking heat on tires trick and see what I find.

[robnolimit]

The H kit is nice, but $$ +. I am currently looking at a bunch of A-Arms. The key is, You can only fix so much. If you're not changing the inner pivits of the suspension, and the geometry of the spindle is the same, there isn't a lot you can do. What they need is more caster. Combined with a spring, spindle and swaybar, they can be made to handle very well. The A-arms can be made to correct the ball joint angles, assist in camber gain, and get the caster in line. And this is what you need. I have about six sets of arms in my shop that I am testing to find out what they REALLY DO, and DONT. So, be a little patient and I'll let you know what I find out.

[SCOTI]

The 'H' kit touts +9° caster ability but utilizes a 1000lb+ spring-rate coil which sure seems excessive (extremely cost prohibitive for many as well....). I know Ride techs arms are advertised to allow 'a couple more degrees' but there's no definitive. I should of asked Tony when I was BS-ing w/him @ Ft.Worth.

[Portmod7]

I was going to ask if anybody had tried the H kit. I stumbled onto it a couple months ago and it sounded pretty sweet. Pricy, yes. But you know what they say, how fast do you want to go? Although, its very hard to know if you're getting the speed you pay for unless you can buy the whole gammot of options and do some testing.

I have been thinking long and hard on what to do in the rear of my truck, as far as lateral location of the rear goes. Yes, a panhard bar is simple, and NASCAR uses it, but NASCAR also only turns in one direction most of the time. I can't seem to convince myself that a panhard bar will NOT cause the vehicle to act differently in a RH turn compared to a LH turn. Depending on which end is mounted to the frame, which end is mounted to the housing, and which direction you intend to turn, it seems like there would be a separate preferred mounting orientation for each turn direction.

If the P-bar is mounted to the frame on the D-side, housing on the P-side, and you make a LH turn, the body will pivot and roll to the right. In my head, it seems like the body would pivot at the frame mount of the P-bar which is a LONG way from the RR spring, generating the majority of the roll-stiffness to the right at the RR spring. The body and CH would also "climb" around the housing mount. With the same P-bar orientation, a RH turn would cause the body to roll about the frame mount to the left, causing the CG to "climb" up and around the frame mount. It seems like the roll stiffness to the left would come from from the CG trying to "climb" because the pivot is located so close to the spring. But I suppose as it tries to climb, it will load the LR as the CG moves more to the left and above the LR spring. I'm not sure I'm anywhere in the ballpark with any of that?

So I guess my question is: Is the dynamic loading on the LR spring in a RH turn the same as the dynamic loading on the RR spring in a LH turn with a P-Bar? Also I have concern with the "radial deflection" mentioned above. Even with a long bar, it's still a factor.

A watts-link would cure radial deflection. I invision one mounted horizontal, either above or below the housing. Although, either position presents mounting/clearance challenges. My question about a watts-link is: where is the RC? It seems like the lateral location would be at the center pivot, on the housing. But what about the horizontal location? Would it be at the center pivot on the housing, or at the height of the mounting points of the links at the frame, or a combination of the two?

The watts-link, as I have suggested it, is a bummer because I'd either be mounting it above or below the housing, and moving it to one or the other will make a HUGE difference in handling. It would be really hard to tune. You could mount it vertically behind the housing, but it seems like it would deliver inconsistant handling from RH to LH turns because of the necessary difference in height of the link mounting points at the frame.

So anyway, sorry for writing a "novel". Suspension geometry intrigues me. I am a race car driver. I work on my own cars, I am my own crew/car chief and mechanic. I get to make suspension adjustments every week trying to go faster. It doesn't always work the way you think it should. I am also a mechanical engineer by profession, so that helps me understand a little more where common sense fails me. I was just looking for some friendly discussion on the topic.

Thanks for posting all the great information!

[robnolimit]

Hey, it was good to meet you guys in Tx.

[smbrouss70]

If any of you guys are seriously thinking about the Hotchkis system, you can get it through Summit for about $1000 less... http://www.summitracing.com/parts/HSS-80390/

[Portmod7]

Originally Posted by smbrouss70

If any of you guys are seriously thinking about the Hotchkis system, you can get it through Summit for about $1000 less... http://www.summitracing.com/parts/HSS-80390/

WOW! Great link, thank you!

[Portmod7]

Ok, a quick visit to the No Limit site has converted me. Really impressive Rob! I think I know where I'll be getting the suspension for my truck when the time comes.

[robnolimit]

One thing I will always push is education, and those are great questions. Search online and buy Herb Adams suspension design and tuning book. It is the best I have read, and it is understandable. NEXT, buy a copy of "suspension geometry pro" software. its only like 80 bucks. the rear suspension program isadaptable to mock up the questions that you are asking, and will show you the RC graphs for each. well worth the money.
Remember that "every action has an equal and oposite reaction" - physics class, so, the left/right force is a average of the two mount points of a P-rod - RC, and an average of the three points in a watts. As to radial deflection, yes, there is some. how much? get a 30" string and draw an arc with a 30" radius, and then measure out any 5 or 6 inches of the arc, the radial deflection is easily seen. Try it.

[robnolimit]

YOUR INPUT NEEDED As I am testing A-Arms, vs. performance set-ups, one thing is becoming clear. If you dail in enough caster to make it turn, you create another problem. When tipping the spindle back to get the caster in range (7 to 9 deg), the steering arm lifts up, in relation to the other steering components. I.E. the center link. One solution is to drill out the hole for the Tie Rod End in the spindle, and use a Rod-End style TRE that can be bolted up from the bottom side of the steering arm. this type of TRE gives you the ability to adjust the hight of the TRE pivit point, and tune out any bumpsteer. So, Are you guys willing to drill out the spindle, or not??What do you think about this??

[PBFAB.COM]

I would drill mine.

[68GMCCustom]

with my 2.5" drop spindles I added tubular upper control arms to my low budget build because I wanted the extra 5* of caster....if needed I'd drill for more.

[N2TRUX]

Originally Posted by robnolimit

...So, Are you guys willing to drill out the spindle, or not??What do you think about this??

If it were part of a tested package, sure I would do it. Keep in mind, I am rather conservative about modding anything with out a proven reason.

[Wvgearhead]

Rob,
I am setting up a 3 link wishbone(triang 4) and I am having trouble with fitting everything
around the driveshaft. What do you think about this set up, 57% Anit Squat,16RCH, 2* roll oversteer, Ic 127" 13", I think my Cog should be around 18 or 19. Wheel base is 116"
Thanks

[M5-]

I'd have no problem drilling that out especially if it gave you the option of using a high quality Cro Mo rod end.

M5

[robnolimit]

Good feedback, keep it coming. Those that know me, know that safety is a concern, and I tend to overbuild.
WvGearhead first off, you need to speek up more often. How about some picts. How are you getting your numbers? Are you using Suspension-Pro? You seem to be up on this stuff. Thats great. Your set-up seems to be pretty good, I'm guessing your tire is about 29" dia. thats puts your roll center a few inches above the axle center line (hieght). I would consider lowering it a bit, or at least allowing for an adjustment later, second set of forward holes. Some squat in a truck is good, to help with some weight transfer. Lets go over this on the forum so everyone can check out your work. How about shocks/springs?

[ctrow]

I'm going to have to do some reading....

Great thread BTW.

The questions I have are related to materials. Where does one find the right tubing and end links for fabricating things like rear end linkage?

Mabye it's covered in the recommended reading earlier in this thread.

Of course it probably makes sense to buy off the shelf on some items. Nothing like making your own pieces though.

[PBFAB.COM]

Originally Posted by ctrow

I'm going to have to do some reading....

Great thread BTW.

The questions I have are related to materials. Where does one find the right tubing and end links for fabricating things like rear end linkage?

Mabye it's covered in the recommended reading earlier in this thread.

Of course it probably makes sense to buy off the shelf on some items. Nothing like making your own pieces though.

We can sell you any of the necessary parts to make your own linkage and or make recommendations to help you out.

[Wvgearhead]

Rob,
I am building a 53 3100 on air, The front is a tci MII and the rear is a custom built Wishbone I picked up, The wishbone and the lowers both span 28", so it should keep constant pinion angle. My problem is, I didnt think about the driveshaft...hmmm, So now I am trying to get the best numbers I can without having to flip the wishbone around and put the single on the center section. I used a suspension calculator from a 4wheel drive form. I dont have any big intentions on racing the truck, but you never know. I figure I would atleast try to make it real fun to drive anyway. The numbers I am plugging in are: upper links ,frame end x=28 y=0 z=17.50 Axle end x=0 y=17 z=18.86 lower links frame end, x=28 y=17 z=9.14 axle end x=0 y=17 z=8.14. This equals AntiSquat=%57 RCH17", IC x=127" z= 13" Roll oversteer 2*, travel roll axis -2.78*. I am not sure about the roll steer, how much is too much. How do you think this set up would handle and ride? The Cog I am guessing to be around 19", and as for the tire size I am planning on running around a 26" tire.

Aaron

[Wvgearhead]

Oh yea just in case, X=0 on the axle y=0 at cl of chassis and z-=0 at shop floor

[PBFAB.COM]

Wvgearhead- What kind of power is your drivetrain puting out? You could always run a 2-piece driveshaft as well. It should take care of your clearance issues on your upper wishbone.

[Wvgearhead]

I am running a 450 hp small block, hopefully a lt1 t56 if I can find one and a 8.8 rear with a locker and 373s. M5 there are books, but you can learn alot by google. I looked at some other forums geared for road racing. The best calculator I have found was actually on a 4 wheeldrive forum. I still need to read a lot more, but I'm learning.
Aaron
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[Wvgearhead]

An extra ujoint scares me, I have been known to break things. Lol
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[robnolimit]

Wv Do you have the motor/trans mocked up yet? Remember that it is helpfull to mount the motor as low, and as far back, as you can. Sometimes we notch the MII crossmembers and box them back up to create more oil pan clearance. The bottom of the pan can be even with the running board. it will look small in the engine bay, but it will drive/handle better. Also, the low motor/trans hieght may solve your driveshaft issue. Try to keep the carb base level with the frame, crank angle will then be about 3*, then match the pinion.

Info search, I'll post up some book/web/chart info later

[Wvgearhead]

Great rob, thanks
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