Hotrod to Hell's Truck Arm Suspension
- Thread starter rjleiker
- Start date
Re: Hotrod to ####'s Truck Arm Suspension
Hey There,
Well I don't have any experience w/ HTH's truck arm set up but do have an opinion for you,had a 65 Chev truck years ago,The original Truck Arm Suspension,short bed,somewhat hot,loved the way it handled and always thought that would be a cool car suspension,like really long ladder bars! Got into Nascar a while back and discovered they all are truck arm and thought that was really cool! Millions of dollars and that's the best they could come up with for 200mph race cars! My guess is some Southern Gentleman needed to build a race car and had a pick up chassis laynig around and well took it and smoked everyone else as I havn't found any history on it,discovered HTH and was delighted to find they were working on a G-body kit,lots of adjustability,stable at high speeds,great hook,what more could you want? After studying the pics for a while I discovered you have to chop the rear foot wells,no big deal as I'm a weldor/fabricator and you have to run side outlet exhaust ala Nascar,sacrifices you have to make,I
decided that was the way to go till I read a test in a magazine,they did HTH's 66 Malibu shop car,put down good #'s,skidpad & slalom,cool,
then a few pages later did a test on a 65 Malibu equiped with i think a Hotchkiss set up,basically all bolt ons,it put up the same if not a tad better #'s in the same tests,so for my money I just can't see it,to anyone connected with HTH looks like great products and for someone wanting extreem high speed performance it would be the way to go,
maybe in my next life if I wanted to bulid a 200mph nightstalker to go play with rich kids in Porches & Ferraris and things like that I would deffinatly use one as that design has been proven time & time again!
Well there it is,hope it helps! Later KillerDave
Hey There,
Well I don't have any experience w/ HTH's truck arm set up but do have an opinion for you,had a 65 Chev truck years ago,The original Truck Arm Suspension,short bed,somewhat hot,loved the way it handled and always thought that would be a cool car suspension,like really long ladder bars! Got into Nascar a while back and discovered they all are truck arm and thought that was really cool! Millions of dollars and that's the best they could come up with for 200mph race cars! My guess is some Southern Gentleman needed to build a race car and had a pick up chassis laynig around and well took it and smoked everyone else as I havn't found any history on it,discovered HTH and was delighted to find they were working on a G-body kit,lots of adjustability,stable at high speeds,great hook,what more could you want? After studying the pics for a while I discovered you have to chop the rear foot wells,no big deal as I'm a weldor/fabricator and you have to run side outlet exhaust ala Nascar,sacrifices you have to make,I
decided that was the way to go till I read a test in a magazine,they did HTH's 66 Malibu shop car,put down good #'s,skidpad & slalom,cool,
then a few pages later did a test on a 65 Malibu equiped with i think a Hotchkiss set up,basically all bolt ons,it put up the same if not a tad better #'s in the same tests,so for my money I just can't see it,to anyone connected with HTH looks like great products and for someone wanting extreem high speed performance it would be the way to go,
maybe in my next life if I wanted to bulid a 200mph nightstalker to go play with rich kids in Porches & Ferraris and things like that I would deffinatly use one as that design has been proven time & time again!
Well there it is,hope it helps! Later KillerDave
Re: Hotrod to ####'s Truck Arm Suspension
I'm a little bit curious about whether the magazine article discussed things like predictability, as well as what made up the rest of the suspension. And what the Hotchkis setup was. I'm not a big fan of the OE converging/triangulated 4-link, and have some autocross experience as basis.
Reason being that if nothing else, the truckarm is predictable and easy to drive fast. A suspension that makes the driver nervous up around 90% will discourage him from ever going much past 75-80%. The various NASCAR "driving experiences" that turn folks with zero verifiable driving skill loose at over 125 mph between real concrete walls wouldn't be doing so if the cars had any "twitchy" tendency at all. My opinion is that the truckarm works best in relatively heavy cars, say 3400# and up.
If you're going to go to the trouble of completely revising the rear suspension, I'd consider a 3-link plus panhard bar (or Watts link). The 3-link + PHB is a good enough arrangement that Ford dropped the converging 4-link from their 2004 and earlier Mustang platforms (Fox/SN95/New Edge) in favor of it for the 2005-up S197 Mustang. IMO, the 3-link is the best of the simple stick axle suspension linkage arrangements, and it really is that much better where cornering & handling is concerned. Improving the straight line without screwing up the cornering geometry is a matter of tweaking the UCA inclination.
For these cars, Marcus at scandc.com was at one time working on a 3-link for the A/G body, but I don't know if anything beyond some prototype bits ever came out of it.
It can't be all that difficult - keep the OE LCAs, swap out the two skewed UCAs for a single longitudinal UCA (maybe using many of the same pickup points), and add a panhard bar. Yes, I've considered doing this to my '79 and getting back to autocrossing with a RWD car.
Norm
I'm a little bit curious about whether the magazine article discussed things like predictability, as well as what made up the rest of the suspension. And what the Hotchkis setup was. I'm not a big fan of the OE converging/triangulated 4-link, and have some autocross experience as basis.
Reason being that if nothing else, the truckarm is predictable and easy to drive fast. A suspension that makes the driver nervous up around 90% will discourage him from ever going much past 75-80%. The various NASCAR "driving experiences" that turn folks with zero verifiable driving skill loose at over 125 mph between real concrete walls wouldn't be doing so if the cars had any "twitchy" tendency at all. My opinion is that the truckarm works best in relatively heavy cars, say 3400# and up.
If you're going to go to the trouble of completely revising the rear suspension, I'd consider a 3-link plus panhard bar (or Watts link). The 3-link + PHB is a good enough arrangement that Ford dropped the converging 4-link from their 2004 and earlier Mustang platforms (Fox/SN95/New Edge) in favor of it for the 2005-up S197 Mustang. IMO, the 3-link is the best of the simple stick axle suspension linkage arrangements, and it really is that much better where cornering & handling is concerned. Improving the straight line without screwing up the cornering geometry is a matter of tweaking the UCA inclination.
For these cars, Marcus at scandc.com was at one time working on a 3-link for the A/G body, but I don't know if anything beyond some prototype bits ever came out of it.
It can't be all that difficult - keep the OE LCAs, swap out the two skewed UCAs for a single longitudinal UCA (maybe using many of the same pickup points), and add a panhard bar. Yes, I've considered doing this to my '79 and getting back to autocrossing with a RWD car.
Norm
Re: Hotrod to ####'s Truck Arm Suspension
Hey, thanks for that input. The three link would be an interesting experiemntal setup.
And I totally agree, a car that is comfortable at 100+ MPH really can make or break the choice for the suspension.
What do you all think about a complimentary front suspension to the truckarm?
And what do you think about spending the extra cash and getting single or double adjustable shocks for the rear as well? Do you think it's necessary? I know you can position the panhard bar more or less parallel to the ground to reduce or increase body roll, so I figure there's your adjustability right there.
Hey, thanks for that input. The three link would be an interesting experiemntal setup.
And I totally agree, a car that is comfortable at 100+ MPH really can make or break the choice for the suspension.
What do you all think about a complimentary front suspension to the truckarm?
And what do you think about spending the extra cash and getting single or double adjustable shocks for the rear as well? Do you think it's necessary? I know you can position the panhard bar more or less parallel to the ground to reduce or increase body roll, so I figure there's your adjustability right there.
Re: Hotrod to ####'s Truck Arm Suspension
Hey Norm,
I didn't mean to be taking anything away from the truck arm design as I said it's been proven to be an extremly stable high speed suspension,just for me realisticly bolt on stuff should be fine as probably all I'll do is drive to work & back,cruise in's and maybe a run down the strip every once in a while and doubt I'll ever see much over 90mph on the street anyway and that'll probably be few and far between,I had a stock 79 with 235/60 15's,HD shocks and no rear anti-
sway bar and was quite comfortable driving fast on curvy roads and thought it felt very stable at 80 to 90 on the highway but that's just me,
as I said it was just an opinion,I think those articles were in Popular Hot Rodding,I'll see if I can dig up the issue and let you know the date as you may be able to read those tests on line,by the way your 3-link idea is very interesting,Have a good one! Later,KillerDave
Hey Norm,
I didn't mean to be taking anything away from the truck arm design as I said it's been proven to be an extremly stable high speed suspension,just for me realisticly bolt on stuff should be fine as probably all I'll do is drive to work & back,cruise in's and maybe a run down the strip every once in a while and doubt I'll ever see much over 90mph on the street anyway and that'll probably be few and far between,I had a stock 79 with 235/60 15's,HD shocks and no rear anti-
sway bar and was quite comfortable driving fast on curvy roads and thought it felt very stable at 80 to 90 on the highway but that's just me,
as I said it was just an opinion,I think those articles were in Popular Hot Rodding,I'll see if I can dig up the issue and let you know the date as you may be able to read those tests on line,by the way your 3-link idea is very interesting,Have a good one! Later,KillerDave
Re: Hotrod to ####'s Truck Arm Suspension
Mostly I'm curious as to whether Hotchkis did anything beyond stiffening up the suspension to keep it in the range where its geometry is at least "OK".
BTW, I think it was Junior Johnson who first ran it, apparently because he wasn't happy with the 1963 Chevy's links.
Norm
Didn't take it that way.Killerdave8813 said:
Mostly I'm curious as to whether Hotchkis did anything beyond stiffening up the suspension to keep it in the range where its geometry is at least "OK".
BTW, I think it was Junior Johnson who first ran it, apparently because he wasn't happy with the 1963 Chevy's links.
Norm
Re: Hotrod to ####'s Truck Arm Suspension
The PHB affects the amount of roll more or less as a function of its midpoint height, not its inclination. You don't want much inclination anyway - suspension movement will work the axle side to side more. Ideally, you'd want it level or nearly so with the car loaded for its most demanding condition. For the OEM's, that's with some passengers aboard and perhaps some trunk load (this is why OE PHBs slope upward toward the chassis side, BTW). For hard cornering, maybe just the driver, or perhaps driver + front seat passenger.
For a front suspension on these cars, you still want to get the roll center above ground level. Not so much for the RC height itself as for fixing the camber curve, which is related. Instead of -1.4"-ish, maybe +1.5" or so. Since the PHB will define a rear RC height that could be 3 or 4 inches lower than that of the OE converging 4-link, you will probably first want to increase the rear roll stiffness a bit. Then balance the front accordingly. At the rear, the OE sta-bar (aka "sway bar") won't work, but perhaps something else would so you wouldn't have to rely only on stiffer rear springs. This is where you either test-n-tune with different springs and bars, maybe adjustable bars, or throw numbers at some analysis to hopefully be closer on the first shot.
Norm
Easy question first. Unless this is specifically for competition and you're going to do extensive testing, double adjustables aren't going to help you that much more than single-adjustables can. But I would consider SA's even for mostly street driving. Here's the caveat - unless you demand a lot from your car, even SA's may be more than you need. There is one exception, and that's if you're looking to drag-race with some level of seriousness. I think for that you do need to be able to play with the bump damping, which true SA's won't let you do (and what the generic adjustables won't let you set independently of the rebound damping).rjleiker said:
The PHB affects the amount of roll more or less as a function of its midpoint height, not its inclination. You don't want much inclination anyway - suspension movement will work the axle side to side more. Ideally, you'd want it level or nearly so with the car loaded for its most demanding condition. For the OEM's, that's with some passengers aboard and perhaps some trunk load (this is why OE PHBs slope upward toward the chassis side, BTW). For hard cornering, maybe just the driver, or perhaps driver + front seat passenger.
For a front suspension on these cars, you still want to get the roll center above ground level. Not so much for the RC height itself as for fixing the camber curve, which is related. Instead of -1.4"-ish, maybe +1.5" or so. Since the PHB will define a rear RC height that could be 3 or 4 inches lower than that of the OE converging 4-link, you will probably first want to increase the rear roll stiffness a bit. Then balance the front accordingly. At the rear, the OE sta-bar (aka "sway bar") won't work, but perhaps something else would so you wouldn't have to rely only on stiffer rear springs. This is where you either test-n-tune with different springs and bars, maybe adjustable bars, or throw numbers at some analysis to hopefully be closer on the first shot.
Norm
Re: Hotrod to ####'s Truck Arm Suspension
Got to thinking a little more on this, and since the truckarms are clamped to the axle, they already provide you with some roll stiffness, kind of like being a rear sta-bar that doesn't look like one. Think of it as a virtual rear bar, maybe. IOW, it's less likely that you'd have any real need for a "real" rear bar than with most other rear suspension arrangements.
Norm
Got to thinking a little more on this, and since the truckarms are clamped to the axle, they already provide you with some roll stiffness, kind of like being a rear sta-bar that doesn't look like one. Think of it as a virtual rear bar, maybe. IOW, it's less likely that you'd have any real need for a "real" rear bar than with most other rear suspension arrangements.
Norm
Re: Hotrod to ####'s Truck Arm Suspension
Sounds like ya want to go dirt tracking, we have done the 3 link deal for years works well. Usually fab a mount in the center of the rear frame and use a stock type upper link of the correct length (rules) but a heim jointed link bar would work as well.We make the upper arms mounting hieght adjustable to control bite off the corner.Works and adjusts just like a drag race 4 link only easier to dial in.For a street car a full lenght panhard bar should be used and mounted level a good starting point for ht. would be the center of the axle tube you can adjust your roll center from there.Now whether or not this will be a big improvement from stock I can't say as both types win regularly but in my opinion it would be once dialed in as the stock metric rear roll center is to high for handling and the front is to low.We correct this with relocating the stock upper arms mounts lower, using extented ball joints etc. Oh by the way a stock panhard bar from a 3rd gen f body works well.
Sounds like ya want to go dirt tracking, we have done the 3 link deal for years works well. Usually fab a mount in the center of the rear frame and use a stock type upper link of the correct length (rules) but a heim jointed link bar would work as well.We make the upper arms mounting hieght adjustable to control bite off the corner.Works and adjusts just like a drag race 4 link only easier to dial in.For a street car a full lenght panhard bar should be used and mounted level a good starting point for ht. would be the center of the axle tube you can adjust your roll center from there.Now whether or not this will be a big improvement from stock I can't say as both types win regularly but in my opinion it would be once dialed in as the stock metric rear roll center is to high for handling and the front is to low.We correct this with relocating the stock upper arms mounts lower, using extented ball joints etc. Oh by the way a stock panhard bar from a 3rd gen f body works well.
Re: Hotrod to ####'s Truck Arm Suspension
I think something like autocross is much more likely to favor the 3-link, torque arm, or even truckarms because you can get the axle steer down to a small value without affecting the antisquat (/anti-lift) very much. Some SAE paper I got hold of ages ago noted that when axle steer got above something like 5% that slalom behavior was becoming adversely affected. Based on a few of my own measurements, I'm seeing roll steer in the stock A/G up somewhere around or possibly above 8%, and the car simply hated autocross slaloms even with stiffened suspension and wheels that were unusually wide relative to the tire size . . . I'll have to see if I can find that paper just to get the exact text.
Norm
A guy who used to post quite frequently on the montecarloss board said pretty much the same thing a while back, and my thoughts are that it's likely to depend on whether your cornering is mostly steady-state or highly transitional. There's more you can do to fix steady-state cornering problems than transitions or at least it's easier to do so without screwing something up.barnym17 said:
I think something like autocross is much more likely to favor the 3-link, torque arm, or even truckarms because you can get the axle steer down to a small value without affecting the antisquat (/anti-lift) very much. Some SAE paper I got hold of ages ago noted that when axle steer got above something like 5% that slalom behavior was becoming adversely affected. Based on a few of my own measurements, I'm seeing roll steer in the stock A/G up somewhere around or possibly above 8%, and the car simply hated autocross slaloms even with stiffened suspension and wheels that were unusually wide relative to the tire size . . . I'll have to see if I can find that paper just to get the exact text.
Norm
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