Which longacre for bump steer
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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IDK
But all you need is to measure the toe-change with ever changing front ride height from full down to full up, or at least the middle 60% or so.
The toe changes with the camber change, that automatically changes as the control arms move thru their arcs. And the camber change is because the control arms are of different lengths.
So if the castor/ camber has already been set, then all you need is to measure the toe-change. And all you need for that is a tape measure, and something to lock the steering wheel in place.
But sometimes the cross-camber is doing a little dance too and you gotsto fix that first.This can happen if the cross-caster is messed up, or if the car is not going up/down level. Sometimes you have to fix the back of the car first, if the springs are not of the same rate, or if for some reason the back is not level, or if it changes it's cross-height during the test.So be careful to not end up chasing your tail!
When I did mine, I had to jack the rear up, remove the wheels, reset the ride-height and put blocking under the front spring perches, to ensure the rear stayed at a constant height and remained side-to-side level.
I was fortunate in that I was an alignment tech at the time and so I spent the day on the rack.
But all you need is to measure the toe-change with ever changing front ride height from full down to full up, or at least the middle 60% or so.
The toe changes with the camber change, that automatically changes as the control arms move thru their arcs. And the camber change is because the control arms are of different lengths.
So if the castor/ camber has already been set, then all you need is to measure the toe-change. And all you need for that is a tape measure, and something to lock the steering wheel in place.
But sometimes the cross-camber is doing a little dance too and you gotsto fix that first.This can happen if the cross-caster is messed up, or if the car is not going up/down level. Sometimes you have to fix the back of the car first, if the springs are not of the same rate, or if for some reason the back is not level, or if it changes it's cross-height during the test.So be careful to not end up chasing your tail!
When I did mine, I had to jack the rear up, remove the wheels, reset the ride-height and put blocking under the front spring perches, to ensure the rear stayed at a constant height and remained side-to-side level.
I was fortunate in that I was an alignment tech at the time and so I spent the day on the rack.
What is it that you're noticing that you're attributing to bump steer? Because most of these old Mopars aren't actually all that bad with regard to bump steer. So, what you're noticing and attributing to bump steer could be something else.
While this article is about using FMJ spindles, it does a pretty good job of explaining what bump steer is and how it effects handling on the street. It also provides an analysis of both A body and FMJ spindles with regard to bump steer, and you can see that for a street car the numbers aren't bad at all. I mean, they're not race car numbers, but they're not bad. They also cover some of their method for measuring everything if you click through the pictures and captions.
Swapping Disc-Brake Spindles - Mopar Muscle Magazine
While this article is about using FMJ spindles, it does a pretty good job of explaining what bump steer is and how it effects handling on the street. It also provides an analysis of both A body and FMJ spindles with regard to bump steer, and you can see that for a street car the numbers aren't bad at all. I mean, they're not race car numbers, but they're not bad. They also cover some of their method for measuring everything if you click through the pictures and captions.
Swapping Disc-Brake Spindles - Mopar Muscle Magazine
Living in northern Alberta our roads/ highways see a crazy amount of heavy traffic and freezing months creating less then desirable driving conditions. The biggest thing I notice is when I go over an old frost heave that hasn't settled. When I go over one naturally the car goes up ( steering pulls one way or the other ) then the car goes down ( steering pulls the opposite way ). I also notice if I hit a pothole with one tire, car will pull the same direction as to which tire hits hole ( hit with left tire, car will pull left, visa/ versa )
Gotcha. Well, some of that could definitely be bump steer. It could also be a combination of worn out bushings and alignment settings. Has your suspension been rebuilt, and what is your alignment set at?
All components are new. Can't remember alignment specs but very similar to newer mustang.
Firm feel stage 2 box
Cap upper arms
.96 torsion bars
Firm feel sector support
Qa1 single adjustable shocks
Front stabilizer bar but no rear
Car is a 74 barracuda so I believe it has the good spindles ?
Tires on front are 245 so that might be contributing?
Firm feel stage 2 box
Cap upper arms
.96 torsion bars
Firm feel sector support
Qa1 single adjustable shocks
Front stabilizer bar but no rear
Car is a 74 barracuda so I believe it has the good spindles ?
Tires on front are 245 so that might be contributing?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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If you cranked a buch of caster into it, then yes you created the bumpsteer; more so if you also cranked in more than 1* of negative camber
Some of the pull tho could be in the Wheels, and tire heights. If the center of the contact patch is not where it's supposed to be, in reference to the SAI, that easily contributes to twitchiness, as can not enough tire pressure.
So, you probably have some work to do alrightey!
Some of the pull tho could be in the Wheels, and tire heights. If the center of the contact patch is not where it's supposed to be, in reference to the SAI, that easily contributes to twitchiness, as can not enough tire pressure.
So, you probably have some work to do alrightey!
E-body! Well that would have been good to know. Yes it has the taller spindles because it's an E-body, but E-bodies had different geometry to begin with so it's not like those spindles add any bump steer on that car, it was designed for them.
Changing the alignment does change the bumpsteer, but that still may not be what you're feeling. I run my '72 Challenger with the later FMJ spindles, Hotchkis UCA's, 1.12" torsion bars, Bilstein shocks, and 275/40/17's on 17x9's up front, 5" backspace (0 offset). Unlike on an A-body you don't need to massively increase the offset to run wider tires, so there's less of an effect there. I was running my car with -.9* camber, +5* caster, and 1/16" toe in with all new bushings. I was running it without sway bars, that's been remedied but the car isn't back on the road yet. I didn't feel like there was a ton of bump steer on that car, although the Hotchkis UCA's do change the geometry.
Wider tires do tend to track bumps and grooves more than narrower tires. The wider you make them the more they'll track ruts and bumps. I'd bet this is a large part of what you're feeling. This can be be dealt with by increasing the positive caster, which will recenter the wheels faster. With power steering I would run at least +5* caster, more if you can get it. Like anything else with a torsion bar set up the ride height plays a part too. So, what I would say is that it's probably worth checking the bump steer to see what you have. I wouldn't be surprised if you don't find a whole lot, but if it is there then you can make adjustments.
Lastly, I would remove those CAP uca's and throw them directly in the trash. That's a disaster waiting to happen. I used to run CAP uca's and lca's on my Challenger. I had a weld fail on the lca's, just like many other people that had issues with CAP's welding. I didn't break the UCA's, but there's no way in hell I'd run them again.
Changing the alignment does change the bumpsteer, but that still may not be what you're feeling. I run my '72 Challenger with the later FMJ spindles, Hotchkis UCA's, 1.12" torsion bars, Bilstein shocks, and 275/40/17's on 17x9's up front, 5" backspace (0 offset). Unlike on an A-body you don't need to massively increase the offset to run wider tires, so there's less of an effect there. I was running my car with -.9* camber, +5* caster, and 1/16" toe in with all new bushings. I was running it without sway bars, that's been remedied but the car isn't back on the road yet. I didn't feel like there was a ton of bump steer on that car, although the Hotchkis UCA's do change the geometry.
Wider tires do tend to track bumps and grooves more than narrower tires. The wider you make them the more they'll track ruts and bumps. I'd bet this is a large part of what you're feeling. This can be be dealt with by increasing the positive caster, which will recenter the wheels faster. With power steering I would run at least +5* caster, more if you can get it. Like anything else with a torsion bar set up the ride height plays a part too. So, what I would say is that it's probably worth checking the bump steer to see what you have. I wouldn't be surprised if you don't find a whole lot, but if it is there then you can make adjustments.
Lastly, I would remove those CAP uca's and throw them directly in the trash. That's a disaster waiting to happen. I used to run CAP uca's and lca's on my Challenger. I had a weld fail on the lca's, just like many other people that had issues with CAP's welding. I didn't break the UCA's, but there's no way in hell I'd run them again.
Alignment specs are
Camber -.56. -.75
Caster. 6.28. 6.79
Toe. .09. .08
As far as the uca's I've heard about the hotchkiss will change the geometry. Do all uca's change the geometry or just hotchkiss. I'm thinking if I'm going to change them out I should get some that will address any issues.
Camber -.56. -.75
Caster. 6.28. 6.79
Toe. .09. .08
As far as the uca's I've heard about the hotchkiss will change the geometry. Do all uca's change the geometry or just hotchkiss. I'm thinking if I'm going to change them out I should get some that will address any issues.
Huh. Well first, your alignment is set up for pretty significantly crowned roads. A 1/4* of camber and a 1/2* of caster both set to pull the car left is pretty significant. I set mine the same on both sides and don't worry about the pull to the right when I drive on crowned roads. But even if you spend a lot of time on crowned roads I would set the camber equal and set up a 1/2* of cross caster. You have about 1/16" of toe as well, depending on your car and the amount of play in your steering that's on the small side. Driving down the road pulls all the slack out of the steering, so, if you only have 1/16" toe in you may actually be getting a little toe out when you drive. You're shooting for 0 when in motion. With all new stuff you can usually get away with 1/16", but that's pretty small on these old cars. Going closer to 1/8" toe in may improve the twitchiness. Already having over 6* of caster though should be plenty caster to have it return to center, so you may have some bump steer in there contributing to what you're feeling. Most E-bodies don't if they're lowered a bit, but there are always exceptions.
As far as the tubular arms go, they all change the geometry some. Most have about an extra +3* of caster built into them. The E-body Hotchkis arms are unique in that they relocate the front suspension mounting point to remove anti-dive. E-bodies used the same suspension as the B-bodies, which included the B-body station wagons. So, that suspension has a lot of anti-dive built into it for those big block station wagons. But that makes your camber curves worse. So Hotchkis moved the front mount to take anti-dive out and improve the camber curves. They figured most folks that want a good handling car have already doubled the spring rate of their torsion bars, which is plenty of anti-dive. Problem is they use heim joint ends, and I don't think those belong on street cars. My first sent only lasted 7k miles before Hotchkis was nice enough to replace them for me. My second set got their little heim boots, but another 7k miles in and I don't think they'll make 10k.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I agree with Blu as to the first paragraph and have no comment as to the second cuz I got's no experience there.
I also think that's an awful lot (lol) of caster for a streeter.Well not awful exactly but a lot more than you need at speeds under 65.
I suspect that if you cleaned the alignment up to -.6camber and 4 to5 caster,and like Blu says about the toe; then set your rideheight sooz the LCAs are in the sweet spot, and played with the tire pressure a bit, well your bumpsteer should almost disappear, or at least the most annoying part.
Compensating for 6 plus degrees of caster could be an all-day job.
If your backspace is pushing the wheels to the outboard that will also probably have to be changed. If you do this, do it before the alignment/ bumpsteer mods. And adjust your wheel-bearings too.
I tried that wide-track cuz I liked the look. But it messed up the scrub radius,and the tires wanted to climb the edges of every rut; man that was annoying. And I mean even little depressions.Centering the tires up got rid of that.......pretty much. After the summer was over, I swapped out the sticky front rubber, for new Cooper Cobras, and then said goodbye to that nervous twitch,forever. Cuz those stickies barely made it thru the summer, and I was of the opinion that they were too expensive to replace, for the fun factor they were providing.
Yeah, I remember that summer with much fondness. Well except for the hours spent on the alignment rack to get it dialed in.
With the Coopers I just drift. Different kind of exciting.
I also think that's an awful lot (lol) of caster for a streeter.Well not awful exactly but a lot more than you need at speeds under 65.
I suspect that if you cleaned the alignment up to -.6camber and 4 to5 caster,and like Blu says about the toe; then set your rideheight sooz the LCAs are in the sweet spot, and played with the tire pressure a bit, well your bumpsteer should almost disappear, or at least the most annoying part.
Compensating for 6 plus degrees of caster could be an all-day job.
If your backspace is pushing the wheels to the outboard that will also probably have to be changed. If you do this, do it before the alignment/ bumpsteer mods. And adjust your wheel-bearings too.
I tried that wide-track cuz I liked the look. But it messed up the scrub radius,and the tires wanted to climb the edges of every rut; man that was annoying. And I mean even little depressions.Centering the tires up got rid of that.......pretty much. After the summer was over, I swapped out the sticky front rubber, for new Cooper Cobras, and then said goodbye to that nervous twitch,forever. Cuz those stickies barely made it thru the summer, and I was of the opinion that they were too expensive to replace, for the fun factor they were providing.
Yeah, I remember that summer with much fondness. Well except for the hours spent on the alignment rack to get it dialed in.
With the Coopers I just drift. Different kind of exciting.
Bump steer is when the chassis is in a compression or rebound cycle and each wheel experiences a different amount of toe change. Number one, both outer tie rods must be adjusted to the same length when the toe is set. Otherwise one tie rod is essentially shorter than the other which is what cause the car to got to one side and then the other when going over a hump in the road. Next, the idler arm and the pitman arm must follow the same arc. This is normally adjusted with the idler arm pivot mounting hole. Ever wonder why R&P steering doesn't have this problem ?
Really? Rack and pinion doesn't have bump steer. Huh. Better tell Ford they don't need to make bump steer correction kits for their Boss 302's...
Ford Racing Mustang Bump Steer Kit (05-14) M-3130-R4
If you alter the geometry, by say, lowering the car, rack and pinion set ups can have bump steer too.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I won't argue that, I just think it's more than most of us need.And getting the bumpsteer out at 4 to 5 is way less time involved.I run +7* caster on my Duster. Works great.
I run 4ish* caster on my 68 Barracuda. Works great.
I've never used a longacre before, don't even know how to pronounce it, lol. But is it possible to do your own alignment with it ? I've had my car aligned every year trying different settings and because of the uca's having to be removed for each adjustment I get charged by the hour. Usually around $300. I may as well invest in something that I can do myself if possible.
I bought my own stuff. Turntables, slip plates, camber/caster gauge, and toe plates. Got tired of trying to explain how to set the alignment on my car to the techs and why I didn't want the factory specs that all the big shops want to use.
I use this caster camber gauge
https://m.summitracing.com/parts/sps-91000
And these toe plates
https://m.summitracing.com/parts/lng-79501
The turntables and slip plates I bought used because they're expensive.
As far as the bump steer gauges go, you might be able to make your own using a set of toe plates if your drilled them to mount to the hubs, but the regular bump steer gauges don't lend themselves to doing a full alignment. You'd still need a caster/camber gauge, turntables, etc.
I use this caster camber gauge
https://m.summitracing.com/parts/sps-91000
And these toe plates
https://m.summitracing.com/parts/lng-79501
The turntables and slip plates I bought used because they're expensive.
As far as the bump steer gauges go, you might be able to make your own using a set of toe plates if your drilled them to mount to the hubs, but the regular bump steer gauges don't lend themselves to doing a full alignment. You'd still need a caster/camber gauge, turntables, etc.
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