Where's The Caster? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 11 Old 01-16-2006, 02:51 AM Thread Starter
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Where's The Caster?

My current setup is; 92 5.0 Mustang with 98 Cobra spindles/brakes, sn95 ball-joints, Energy Suspension polyurethane A-arm bushings, Tokico Illumina struts, stock V8 springs, 200k+ 4 cylinder rack and end links, and most recently Steeda aluminum CC plates.

Previous to the CC plates, the car had .2 degrees of positive caster. With the plates, I can only get 1.3 degrees positive caster. Other people with similar setups seem to be getting a lot more.

What can be done to get more caster?


Quantum materiæ materietur marmota monax si marmota monax materiam possit materiari?

Last edited by Blixa_Bargeld; 01-16-2006 at 02:55 AM.
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post #2 of 11 Old 01-16-2006, 08:39 AM
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If your front springs are weak and sagging you won't get much caster. As the front of the car is lowered caster gets more negative. Perhaps with the age of the car a new set of springs are needed? There are also offset LCA bushings available that will give you more caster.

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post #3 of 11 Old 01-16-2006, 11:18 AM
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I would expect LCAs with different geometry (shifting the balljoint fwd) to give you more caster, but how does changing the offset of the bushing do it?
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post #4 of 11 Old 01-16-2006, 01:08 PM
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The offset bushings move the control arm forward. Since the strut tower remains unchanged the results are the same as moving the top of the strut back thus creating more positive caster. The Steeda offset bushings move the lower control arm forward by 5/16" I think.

I made some offset bushings for my car out of teflon and if memory serves me right I gained almost 2 degrees.

MM also has some lower control arms that move the ball joint 3/4" forward but I'm not sure if they have them that will accept stock springs.

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post #5 of 11 Old 01-16-2006, 01:10 PM Thread Starter
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How can I determine if my springs are worn?

The car defiantly has a rake to it, the back in considerably higher than the front. A measurement puts the top of the front tires, 1.5” from the fender in the front, and 3.3” from the fender in the rear. The tires are 245/45 17”s.

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post #6 of 11 Old 01-16-2006, 02:31 PM
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Quote:
Originally Posted by Blixa_Bargeld
How can I determine if my springs are worn?

The car defiantly has a rake to it, the back in considerably higher than the front. A measurement puts the top of the front tires, 1.5” from the fender in the front, and 3.3” from the fender in the rear. The tires are 245/45 17”s.
Therein lies your problem. Ride height measurements should not be taken between the tire and fenderwell opening. For the rear compare the height of the front and rear lower control arm pivot points. For the front use the lower A-arm front pivot and the ball joint heights. Using these reference points eliminate changes due to tire size and discrepancies from build tolerance in body parts.

Mustangs generally seem to do well with the rear LCA pivot bolts at the same height front and rear. Adjust spring length, or ride height accordingly to get the car at a level stance, or even slightly higher in front.
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post #7 of 11 Old 01-16-2006, 04:01 PM
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Quote:
Originally Posted by Glenn
If your front springs are weak and sagging you won't get much caster. As the front of the car is lowered caster gets more negative. Perhaps with the age of the car a new set of springs are needed? There are also offset LCA bushings available that will give you more caster.
Howdy Glenn. Long time, no talk.

Are you sure you're not thinking of camber? As the spindle and strut top get closer, the angle between the two approaches horizontal. Assuming the strut top is behind the spindle, that means positive caster will increase. Further, offset bushings increase positive caster slightly, but the main gains are seen in the negative camber (since the bushings push the control arm farther out than forward).

Brainfart or am I missing something?

As far as the relative lack of caster, my first question would be if the car had ever been in a wreck or had the K-member removed for some reason. You sould have quite a bit more than that, especially considering the 98 spindles. Using the stock A-arms?

Dan
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post #8 of 11 Old 01-16-2006, 05:09 PM Thread Starter
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I've got approximately (I could only find a flimsy plastic protractor) a 3 and quarter inch rise back to front on the rear LCAs. I assume that's pretty extreme. The lower rears are Steeda aluminum with polyurethane bushings. Uppers are Ford heavy duty.

I don't think the car was ever wrecked. Failing collision repair, I doubt the K-member was ever removed as it was a stock four cylinder when I bought it. I’ll check it out though. Are there some reference points I can use to determine if the K-member is in the correct, if not optimal, fore-aft position?

The front arms are off an ’87 vert, new sn95 ball joints, and poly bushings.

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post #9 of 11 Old 01-16-2006, 05:45 PM
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Quote:
Originally Posted by Blixa_Bargeld
1. I've got approximately (I could only find a flimsy plastic protractor) a 3 and quarter inch rise back to front on the rear LCAs. I assume that's pretty extreme.

2. Are there some reference points I can use to determine if the K-member is in the correct, if not optimal, fore-aft position?
1. Umm, yeah. Your springs are seriously messed up. If this is a 4 to 8 conversion, maybe the 4 cylinder springs are still in there and being compressed more by the weight of the V-8. And, it sounds way too high in the back - some drag racer's wet dream, maybe.

If this is a street machine, the Bullitt spring/shock combo should put you at a good ride height with a decent ride/handling compromise. If it's going to see some track/autocross use, maybe the H&R Super Race springs and some Bilsteins. More money, better handling firmer ride.

2. Read the panhard bar or torque arm instructions on the Maximum Motorsports web site. They include detailed instructions on squaring your chassis. You may be able to push the k-member a bit forward and remain square. Either MM or Griggs has some good info on measuring ride height on their website.

On the other hand, some camber/caster plates are more equal that others. I.e, some have a greater range of adjustability (and, some are much better engineered). So, once you have proper springs (if you do it yourself, search re putting the pigtail on the spring in the right place. This will affect ride height.), see what you can get. Some C/C plates give minimal caster if you max out on camber. If that is the case, get some MM plates and try again.

With crappy Mac plates, I can get -3.2 camber and +5.0 caster. That's with the offset front lca bushings and it's an SN95 - not sure if Foxes give less.

Worst case scenario, you can get some flat plates to shim up the short springs and cut the too tall ones down a bit. Not likely to give you good or even predictable ride/handling.

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post #10 of 11 Old 01-16-2006, 05:53 PM
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Quote:
Originally Posted by baglock1
Howdy Glenn. Long time, no talk.

Are you sure you're not thinking of camber? As the spindle and strut top get closer, the angle between the two approaches horizontal. Assuming the strut top is behind the spindle, that means positive caster will increase. Further, offset bushings increase positive caster slightly, but the main gains are seen in the negative camber (since the bushings push the control arm farther out than forward).
Hey baggie, yeah, long time.

Think as the caster angle as being a line drawn from the top of the strut mount pivot point through the center of the lower ball joint. With positive caster that line will meet the ground towards the front of the tire, hopefully creating an angle of about 3-5 degrees from vertical. Now, if you lower the front of the car (or conversely raise the rear) the strut top mount will rotate forward compared to the lower BJ which will remain in the same location. In essence this will reduce positive caster. It no doubt will change camber, but caster will be affected as well.

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post #11 of 11 Old 01-16-2006, 06:37 PM
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Gotcha Glenn. I wasn't thinking of lowering only the front, but rather both ends an equal amount.

Dan
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