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Achieving high camber/caster for road race |
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blenny 
AMC Apprentice 
Joined: Dec/13/2014 Location: 77541 Status: Offline Points: 82 |
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 Topic: Achieving high camber/caster for road racePosted: Jun/19/2018 at 4:35pm |
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We have a 74 Gremlin we road race. We want -2.5 camber and +5 caster. With both the offset bolt and strut maxed out we are at around -1.5 and +2. Is that normal? What are people doing to get more besides control freak or other high dollar options?
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73Gremlin401
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Joined: Mar/02/2013 Location: Stmbt Sprgs CO Status: Offline Points: 946 |
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Posted: Jun/19/2018 at 4:44pm |
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why do you want/need that much camber in particular? Most modern road race tires that I'm aware of work their best in the .5 - 1.5 degree range. On the caster issue, the most the lower control arm pivot bushing can stand is about 2.5 degrees. 2 degrees works well, and the basic geometry of the AMC front suspension and steering work well at that amount of positive caster. You'll still be replacing that bushing on a fairly regular basis at 2 degrees, and inspection of the control arm for cracking around the bushing shell is an every-weekend thing. What is the car doing (or not doing) that makes you feel like you need to dial in more? In all the years that I've run AMCs on track (mostly Gremlins, but also later Javelins) I got what I needed in terms of steering response and accuracy and grip via relatively modest alignment adjustment, but through use of rear sway bars, various bushing durometers, and tire pressure adjustment. On Gremlins in particular, the loss of fuel load during a 30 minute session will change the handling and braking of the car rather dramatically, I used an adjustable brake bias valve to compensate for this.
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73 Gremlin 401/5-spd.
77 Matador Wagon 360/727. 81 Jeep J10 LWB 360/4-spd 83 Concord DL 4-dr 258/auto  |
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farna
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Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19675 |
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Posted: Jun/20/2018 at 5:57am |
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About the only thing you can do to increase the caster is to move the ball joint forward on the upper arm and/or rearward on the lower arm. Not an easy task with stock parts. You might consider building a tubular lower arm with the ball joint offset to the rear a bit. Could make it a bit longer to get more camber as well, while you're making a custom lower arm and really want/need it...
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Frank Swygert
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FSJunkie
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Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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Posted: Jun/21/2018 at 2:02am |
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Let me guess, you are trying to reduce understeer. Getting weight out of the front of the car and more of it to the back will help you. Move the battery to the back. Get the heavy options under the hood like A/C and power steering out. Unfortunately, AMC engines are heavy monsters. Even the AMC I6 weighs as much as a Chevrolet small block. Not much you can do there if you want to keep AMC power. This Gremlin has a front anti-sway bar, right? Six cylinder Gremlins did not come standard with a front anti-sway bar. Even with a front anti-sway bar, all your roll resistance will be in the front suspension and that will tend to overload the outside front tire and make it scrub....understeer. Getting a rear sway bar installed will increase the rear roll resistance and take some of that loading off the outside front tire. Make the rear wheels take more of the cornering force. |
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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farna
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Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19675 |
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Posted: Jun/21/2018 at 6:00am |
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Or get a longer wheelbase car. The short wheelbase hurts cornering.
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Frank Swygert
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blenny
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Joined: Dec/13/2014 Location: 77541 Status: Offline Points: 82 |
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Posted: Jun/21/2018 at 8:02am |
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The car is pretty balanced with a full tank and starts to suffer some oversteer once losing 160 lbs from behind the rear wheels after a 2 hour session. The only time it seems to understeer is low speed narrowing radius turns, but that is kinda expected. It has the factory i6 front sway, the car was a rally x, and addco rear sway bar. All poly bushings and kyb “gas adjust) shocks. We generally run BFG Rival S in 225s if memory is serving me correctly.
The main symptom we are experiencing is significant wearing to the outside edge of the front tires (compared to similar weight/balance cars) with tire temperatures increasing as you go from inside to outside. I have seen some people run strut rods with a heim joint and the adjuster in the center, are those usually stock lengths? |
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304-dude
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Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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Posted: Jun/21/2018 at 8:29am |
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There is a few nice aftermarket cupped Delrin ball strut rod kits for Ford Mustang. Greyhound was to order a kit, made to fit AMC or have info on what can be done to fit them. They are the only kits with proper centering of pivot points on the stock brackets.
As for length, none of the AMC only kits that I have seen keeps proper stock length. If you have some time on your hands and have some machining tools available. For a grand total of $70 on quality parts, you can do a Delrin ball insert between your poly strut rod bushings. It will help on keeping the strut rod stabilised and less fatigue on the threads, where it is the weakest. There was a grass roots Spirit with 69 chevy truck upper ball joints to help with steering by raising the arc, so that your closer to the sweet spot on stock suspension travel. All 70 on up AMC cars have an un equal geometry when front compresses under hard turning. The truck upper ball joints are about an inch longer, so the spindle lowers the lower arm to compensate the and stablise negative camber when springs compress with stock suspension. Don't know if you looked at my thread, but it may give you ideas and options. Though I don't expect anyone to follow everything, as it is how I am tackling issues with stock suspension being lowered and setup for double duty with the most modernised and agressive wheel/tire options, keeping up with late gen Mustang and most Vettes with track width and alignment options. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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blenny
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Joined: Dec/13/2014 Location: 77541 Status: Offline Points: 82 |
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Posted: Jun/21/2018 at 10:24am |
Wow your build and engineering is more than impressive!! I think moving the upper hump back is...out of my scope, to say the least. Anyone know if greyhound had any luck with the opentracker bushings? I was kinda hoping for “ if you use “x” upper arm it will move the ball joint in and back and fix all your problems,” or something similar, but it is never that simple. I need to look more into the grass roots Spirit. |
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304-dude
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Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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Posted: Jun/21/2018 at 1:21pm |
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The only other option that is mostly bolt on, is CF suspension. It allows a lot of adjustment, and removes the strut rod by using a lower arm similar to a Mustang II design, that bolts to the frame.
You can probably find tubular upper arm that either allows upper ball joint adjustment or has enough material to change by modification, the change of location of your ball joint. There are a few various suspension components made, that I don't have a name or reference to, but may be searchable online. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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73Gremlin401
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Joined: Mar/02/2013 Location: Stmbt Sprgs CO Status: Offline Points: 946 |
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Posted: Jun/21/2018 at 4:28pm |
OK - you are running essentially the same setup I ran for years with my Gremlin when it was a 6 cyl car, and as a V8. I too was and still am using the Addco up-and-over rear bar, and urethane bushings all around. Back in the day I was running 225 tires on 14"x7 AMC Turbocast wheels, now I'm running 245 tires on 16 x 8s with the V8 Caster/Camber. I've used as much as 1.5 degrees of negative camber, and as much as 2.5 degrees of positive caster. I've dialed both back now to 3/4 degree of neg camber, and 1.5 degree of positive caster, and the bushings, power steering pump thank me. The one difference in your setup and mine is the front sway bar - I'm using the 1 1/8" Spirit front bar, rather than the 3/4" or 15/16" Gremlin bar. While that does add in some additional front stiffness, it seemed to be just enough to help, without creating more terminal understeer under full load. The other thing that really helped was re-locating the battery to just behind the passenger front seat. I found putting it all the way in the back was counter-productive with, as you've already figured out, the shifting and steadily decreasing fuel load. Let me know if any of this helps.
Edited by 73Gremlin401 - Jun/22/2018 at 2:15pm |
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73 Gremlin 401/5-spd.
77 Matador Wagon 360/727. 81 Jeep J10 LWB 360/4-spd 83 Concord DL 4-dr 258/auto |
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304-dude wrote: