No need for that much on a manual steering car.
Following the SKOSH chart - your experiences?
- Thread starter MRGTX
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You have to remember where the SKOSH chart came from, it's the correction for running radial tires on cars where the original specs were for bias ply tires. The SKOSH chart is based on radial tires and their alignment needs, so really it applies generally to all cars running radial tires. Now, specific platforms have their own specific nuances, like the notes for the F/J/M cars.
There's no reason at all why the SKOSH chart shouldn't apply to C-body cars, at least in general. For higher level performance some minor tweaks might be needed, C-bodies are generally heavier so you might see more camber wear at lower degree settings than you would on an A-body. Or you might find that the steering gets heavier at lower settings than with an A, that sort of thing. But how you use the car will probably be a bigger factor, if you really want to make your C-body carve you might actually need more camber and caster to counter the physics of those beasts and just have to deal with some of the other things that come up.
Completely disagree. The effect of caster on steering and handling performance doesn't change if your steering is manual or power. Its benefit of additional high speed stability and additional camber gain on turn in is completely unchanged by whether or not the steering is boosted or not. If performance is improved by running additional positive caster on a power steering car it is the same for a manual steering car.
The only difference between the two is the steering effort felt by the driver, especially at lower speed. That's the only reason there are different recommendations for power and manual steering, driver comfort. Not performance.
And the more tire width you run up front the more important additional caster becomes. +2.5 to 3° might be fine if all you run up front are 225/60/15's. But if you run 275/35/18's, you will need more positive caster to counteract the wider tires tendency to get pulled around or "track" with ruts and road quality issues. The wider the tires get the more caster you need to keep them going where you want them- instead of them going where they want to go.
I've been running 275's up front for years now, on both my Challenger and my Duster. +3° of caster is stupid with those tires. I ran about +5° with my Challenger, which had power steering, and that was all I could get with the suspension components I had. It wasn't bad, but with my Duster and its more adjustable suspension set up I have found that more caster is still better. I run +6.5° of caster on my Duster, and it works great. I have run everywhere from about +5° all they was up to +8° of caster on the Duster, +6.5° is the sweet spot where the tires are well controlled and the car is nice and stable and the steering effort is manageable for every day driving scenarios. Much past +6.5° and the steering effort effect from the caster increases rapidly, much less and those 275's start to have a mind of their own. And yes, the Duster is a manual steering car with the 16:1 fast ratio steering, 275/35/18's, and +6.5° of caster that I use as a daily driver about 9 months out of the year, doing at least 120+ miles a week when I'm using it. Is the steering a bit heavy at parking lot speeds? Yes it is. But it's not unmanageable.
The other thing is, the quality of your steering components matters. Ball joints, tie rod ends, pitman and idler arm resistance is all very important. I recently installed a bearing idler arm set up from BergmanAutocraft on my Duster, and the steering effort was noticeably reduced.
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This C body is just an everyday driver with radials. Upgraded brakes to deal with the little cars that cut you off on the highway.
I was just wondering why it skips over C bodies on the list and I agree it shouldn't be different. Just wanted some advice. Thank you all.
I was just wondering why it skips over C bodies on the list and I agree it shouldn't be different. Just wanted some advice. Thank you all.
Nice! So for an everyday driver with 15" radials you don't need to go too crazy, with the Firm Feel upper control arms you should be able to get a decent amount of positive caster. Somewhere in the neighborhood of -.5° of camber, +3 to +5° caster and around 1/16" toe in should be fine.
As for C-bodies not being listed on the SKOSH chart, I'm sure it was just an oversight. The skosh chart is after all around 30 years old now, maybe more. I believe it was first published by Ehrenberg in the early /mid nineties. The market for handling Mopars was pretty thin then, and even more so for C-bodies. And yeah, the charts recommended specs are a bit out of date IMO, the caster especially is lower by a degree or two across the board. But that's because it was based off of using factory control arms with offset bushings. With all the tubular and adjustable UCA's out there now +4° is no where near the maximum you can get. And tire composition has changed a ton in that time too. For the fairly common 15" tires, BFG T/A's and Cooper Cobra's, the skosh is pretty decent. But for more modern tires like you can get with 17"+ rims, the soft compounds and increased grip can tolerate more extreme settings. Most modern cars run +8° to +10° of caster. Sure, some of that is tied into the suspension design, but more of it is about high speed stability and the fact that everything has power steering now.
purplehazenils
Well-Known Member
Has anybody had any bad experiences with running too much caster on a power steering car? It seems like the only downside is steering effort which should not be a problem with power steering?
On these cars with the available parts you’d have to work pretty hard to run “too much” caster.
It is possible in general though. The more positive caster you add the more the wheels camber when your turn. That’s actually what adds the steering effort, as you turn the wheels thr positive caster actually adds negative camber, which turns the wheel more on its edge, which literally lifts the car. So, you can run so much caster that the turn in camber change will be too much and the lifting effect can actually unsettle the car in a corner.
And there is a point where you have too much camber gain too, what you’re trying to do is have the outside wheel flat on the ground so you have the best traction. The camber gain counters the body roll and CG change, so ideally you want the camber gain to match the lean angle. Too much can also reduce traction.
But that’s the theoretical side, the reality of the parts available is you’d have a hard time adding so much caster that you’d unsettle the car or have too much camber gain.
It is possible in general though. The more positive caster you add the more the wheels camber when your turn. That’s actually what adds the steering effort, as you turn the wheels thr positive caster actually adds negative camber, which turns the wheel more on its edge, which literally lifts the car. So, you can run so much caster that the turn in camber change will be too much and the lifting effect can actually unsettle the car in a corner.
And there is a point where you have too much camber gain too, what you’re trying to do is have the outside wheel flat on the ground so you have the best traction. The camber gain counters the body roll and CG change, so ideally you want the camber gain to match the lean angle. Too much can also reduce traction.
But that’s the theoretical side, the reality of the parts available is you’d have a hard time adding so much caster that you’d unsettle the car or have too much camber gain.
The guy who made the skosh chart geared it towards performance driving. Due to their size, and especially weight, he didn't believe C-Bodies were well suited for that.
You can always ask him yourself. Look for the link on the page.
Rick Ehrenberg's Mopars
purplehazenils
Well-Known Member
That is interesting thank you, aiming for+6° caster might be a happy medium then.
Wvbuzzmaster
Well-Known Member
I followed the Skosh for Typical Street Performance on my 1972 Duster. Running 16:1 manual steering box with 215/65R15 on stock rebuilt front suspension with BBP (no offset bushings) and +2 rear leafs on 255/60R15 out back. Running 340/727 and 1.03 PST torsion bars cranked to factory ride height and full interior for additional info (all part of the alignment process). I have no clue how much positive caster I made it to because I have yet to take it to an alignment shop (not sure where I trust yet). But I did the alignment in my garage carefully and the handling is fine, no regrets. Basically I started by adjusting upper A arms for max positive caster and then started moving them out until I had -0.5 camber, and finished by setting toe. So far so good.
I just completely rebuilt my front suspension
70 Dart with factory Kelsey Hayes discs,
a Fat Hellwig front sway bar,
medium duty front gas shocks,
Rear shocks PST,
16:1 manual box
1.03 PST bars,
Moog Offset Bushings for the upper control arms which are allowing me to run 225 70 Coopers.
Im telling the guy who aligns my front to go with max street perf settings.
Am I inviting eating up tires quickly ???
Kudos to 72NuBlu who give us all very valuable advice, I have picked his brain for suspension knowledge and he never disappoints !
I have high expectations for the excellent handling charcteristics on my Dart
70 Dart with factory Kelsey Hayes discs,
a Fat Hellwig front sway bar,
medium duty front gas shocks,
Rear shocks PST,
16:1 manual box
1.03 PST bars,
Moog Offset Bushings for the upper control arms which are allowing me to run 225 70 Coopers.
Im telling the guy who aligns my front to go with max street perf settings.
Am I inviting eating up tires quickly ???
Kudos to 72NuBlu who give us all very valuable advice, I have picked his brain for suspension knowledge and he never disappoints !
I have high expectations for the excellent handling charcteristics on my Dart
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Those settings do not eat tires unless you do some stupid exotic maximum camber adjustments. How are you going to use it? Circle track or Rally? If so you need it aligned for that use. Maximum street performance is ok. Remember, the more caster you have the harder it is to steer and maneuver at stops and low speeds. If you have power steering, who cares.
Nope, no tire eating with those specs. Keep the camber under -1° and you won’t notice any abnormal tire wear. I’ve run -1° up to around -1.5°, once you go past 1° you will start to see camber wear if all you do is freeway driving.
The caster is fine, I run +6.5° with 16:1 manual steering and 275’s up front. +3.5° with 225’s will be easy still, and you may not get that much caster with factory UCA’s and offset bushings anyway.
Thats a lot of caster but I bet it goes where you point it and stays there.
It does!
It’s because of the 275’s. The wider the tire up front the more they tend to seek out ruts and imperfections in the pavement and start to wander around. 225’s don’t need that much caster to be stable.
With 275’s between my Challenger and my Duster I’ve run between about +3.5° all the way up to +8° for caster. I’ve found on my Duster that with less than +6° the front wheels start doing what they want instead of what I want, they’ll start tracking ruts and things. It’s not terrible but it becomes more noticeable as the caster decreases. I’ve also found that when I go past +7° the steering effort at lower speeds starts to increase exponentially. So I shoot for around +6.5°, at least on my car that seems to be a happy medium to balance tire wander and steering effort. Nice and stable at speed on the freeway and I can still park it at the grocery store without tearing a bicep.
ALong those same lines, toe out, or close to zero toe with loose steering components, will do some funky things. It has a mind of it's own. Each tire is fighting to be the one to steer.
For sure!
Getting the dynamic toe closer to 0 helps lighten up the steering and make turning quicker, but the closer you get to zero toe going down the road the more flightly the car will feel. Good for racing and autoX (to a degree anyway), not so great for a street car or freeway stability. My stuff is all pretty new so I try to stay between 1/16" and 1/8" toe in, closer to 1/16" if I can. But I'm using toe plates not some fancy alignment rack so that's cutting it pretty fine.
And it's all in degrees now. I had my wife's Envision when it was new because I didn't like the way it drove. AWD of course. It was within spec but not close enough for me. I had him fine tune it to real close to zero, front and back. One side was just in with the other side just a tick more and still in spec. We have about 50,000 miles on the original tires and I have never rotated them. no uneven wear, no cupping or chopping. They will make it through the winter with ease. It's just how it is.
I'm only running 15x7 wheels and 225/60 HR15 tires on the front of my A bodies - all three of them. So the typ. performance specs work fine for me. Tracks well at high speed. Actually better than my wife's E class Mercedes at any reasonable cruising speed. Her car, better keep your hands on the wheel and your eyes on the road. Cornering? - well not too much in the way of corners around here, but it seems to do well enough.
Last year when I had mine aligned, they went by my suggestions.
.75 NEG camber, 1/8" toe in or the metric equivalent to that and as MUCH POS caster as they could get.
I have stock UCAs but with offset bushings. The man got 5 1/2 degrees of POS caster.
The front tires are a 275-40-18. The car steers great, handles great too.
.75 NEG camber, 1/8" toe in or the metric equivalent to that and as MUCH POS caster as they could get.
I have stock UCAs but with offset bushings. The man got 5 1/2 degrees of POS caster.
The front tires are a 275-40-18. The car steers great, handles great too.
Nice alignment specs! I think that's the most + caster I've heard of with just factory UCA's and offset bushings. Although at this point I'm more familiar with the A body stuff than B/E, and there are definitely some differences in the suspension geometry.
I think I've the distinction of what could be called the best tolerance stack up in Mopar history. Others have the same parts but their cars couldn't get more than 3 degrees of caster. I cannot explain why I got this lucky. With the Borgeson steering box, the car steers so much different than the other Mopars I've owned. I am grateful for this great luck.
I'm glad to hear about the Borgeson box, I bought and installed a 16:1 from them. Cost more, worth it
Also have their 1.03 torsion bars
Map63Vette
Well-Known Member
Old thread, but I wonder, have you changed the ride height from stock? I think I read some of your posts about the car when looking up caster settings and may have just missed it. It looks like the caster curves on the A bodies at least are pretty quick and will add a lot of caster as you drop the suspension. I wonder if maybe one reason you got the nice numbers is if you are running a bit lower ride height than stock?
Reminds me of another question. I am considering an electric power steering for my 73 scamp. Any changes to the skosh recommendations for power vs manual steering?
autoxcuda
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Not really.
But if you use that for manual steering you might want to reduce those caster numbers depending on your front tire width and if the manual steering ratio is 20:1 or 16:1.
Caster is not as performance enhancing as Camber then Toe. Caster can induce some camber in cornering. The caster is mostly driver feel and high speed stability
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