camber/toe/caster relationship - Impala Tech
Brakes & Suspension Conversion Questions & more

 
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post #1 of 7 (permalink) Old 08-17-2015, 02:38 PM Thread Starter
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camber/toe/caster relationship

What affect (if any) does an adjustment to the camber and toe have on the caster angle?

Said another way, If caster angle is correct and camber and toe is adjusted, does the caster angle need verification?

Thanks.
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post #2 of 7 (permalink) Old 08-17-2015, 03:26 PM
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Because everything is connected mechanically if you move one part it could theoretically affect another part, but not by much. The actual angles are not carved in stone any way so getting it within a quarter of a degree is a waste of time. This is why when you hit a pot hole it knocks all of your alignment adjustments out of whack when only the caster should be affected.

I run as much caster as I can because I like the idea of the weight of the car centering the wheels straight ahead as soon as I loosen my grip on the steering wheel. I also run a bit more negative camber than the factory recommends to improve my car's cornering ability. I keep to factory recommended Toe in corrected for tire size as that affects your Ackerman steering geometry (real axle turning inside of the front axle track) which also affects the car's ability to be stable in a corner.

I also run a much larger tire than recommended because the bigger the contact patch the better the grip in dry conditions (you reverse the tire patch size to minimize it if it is wet, or there is any snow or ice to deal with). A larger than stock tire size also affects the front end's geometry as mentioned; as all of the angles meet in the center of the tire patch if you run the correct height tire.

The final piece of the puzzle is to have enough power available to go from under steer (the front end plowing), to over steer (the rear end passing you) at the touch of the gas pedal.

In addition to drag racing all the time I was also involved with SCCA rally racing and auto cross as turning is as important as driving in a straight line and can be even more fun!

But to answer your question they generally are independent of each other. If you are having issues consider rotten rubber suspension bushings allowing parts to move in addition to high mileage wear that creates additional front end slop.

Big Dave
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post #3 of 7 (permalink) Old 08-17-2015, 05:08 PM Thread Starter
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Thanks Dave.

I asked because I recently had a lot of work done on the front end of my 63 Impala. I switched to a Borgeson steering box and replaced my original upper control arms with tubular ones in order to get the recommended 4 degrees of positive caster. All bushings not included with the new control arms were also replaced. A mistake was made when the car was aligned. It was set to the recommended caster specs and the OEM specs for camber and toe. The vendor for the new upper arms requires different (from OEM) specs for camber and toe. The second time the car was aligned only the camber and toe were adjusted; caster was not checked. Hence my question. I will demand a third alignment if there is reasonable reason to do so. If I understand your response, I should be ok.

The car drives much better than it used to. All the vibrations and 'jiggles' are gone. The leaks are gone. The 'wander' is gone. I'm going to start another post on the one remaining 'improvement' I am looking for.

Thanks again.
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post #4 of 7 (permalink) Old 08-17-2015, 08:18 PM
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It will drive even better with the caster set to the manufacturers specification.

Think of the bad shopping cart with the fluttering front wheel. The caster angle is what straightens the wheel out. The fiber of cotton wrapped around the axle from a wet mop that was slapped against it one night is what causes the wheel to turn as it acts like the brakes are on. These two forces are in constant battle and because it is mounted on a ball bearing supported shaft it vacillates back and forth like a politician with his finger in the air.

If your unequal length a-arms want more caster it is for a reason; usually to center the wheel and reduce the tendency to wander following every crack in the road with wide tires.

Big Dave
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post #5 of 7 (permalink) Old 08-17-2015, 09:29 PM Thread Starter
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Quote:
Originally Posted by Big Dave View Post
It will drive even better with the caster set to the manufacturers specification.

Think of the bad shopping cart with the fluttering front wheel. The caster angle is what straightens the wheel out. The fiber of cotton wrapped around the axle from a wet mop that was slapped against it one night is what causes the wheel to turn as it acts like the brakes are on. These two forces are in constant battle and because it is mounted on a ball bearing supported shaft it vacillates back and forth like a politician with his finger in the air.

If your unequal length a-arms want more caster it is for a reason; usually to center the wheel and reduce the tendency to wander following every crack in the road with wide tires.

Big Dave

Sorry for the ambiguity in my posts. Back whenever I used the term 'OEM' I meant the original GM specs for the 63 Impala.

So, to clarify, the car was aligned the first time (after the upgrades) to the caster recommended by the steering box manufacturer (+4 degrees) and the toe and camber specified by GM for the 63 Impala. The second alignment changed the toe and camber settings to those specified by the control arm manufacturer. Caster was not checked during the second alignment because the +4 degrees caster achieved during the first alignment also met the specifications of the control arm manufacturer.

Unless there is reason to suspect that the caster changed when the toe and camber was adjusted during the second alignment, my car should be meeting the values specified by both the steering box manufacturer and the control arm manufacturer.

That was the basis for my original question. If I understand your replies, you are saying the caster should not have changed and that the new parts should all be installed as specified by their respective manufacturers. Am I missing anything?

Thanks
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post #6 of 7 (permalink) Old 08-17-2015, 10:07 PM
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If you are using the aftermarket specs to meet the aftermarket part design then you should be golden.

This is a very common rework on a first generation Camaro due to the poor design choices made by GM in rushing a pony car into the muscle car market in the mid sixties. The engineers at Chevy were still thinking in terms of economy car, while the consumers were thinking TransAm racing, so there were a lot of garage fixes and aftermarket parts made to improve the steering geometry of the Camaro and the Nova that used the same front end.

What I wonder is how many of the Impala aftermarket front suspension parts are really necessary; since a lot of those same front end parts that were used on the Impala seem to work just fine when used on the Corvette that shared common suspension parts up through the introduction of the C4 Corvette in 1985. How much is need and how much is marketing hype I don't know. I do know that seventy percent of the price you paid is going to buy liability insurance for the "manufacturer" if they were made here in the US.

Big Dave
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post #7 of 7 (permalink) Old 08-18-2015, 08:15 PM Thread Starter
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Quote:
Originally Posted by Big Dave View Post
If you are using the aftermarket specs to meet the aftermarket part design then you should be golden.

This is a very common rework on a first generation Camaro due to the poor design choices made by GM in rushing a pony car into the muscle car market in the mid sixties. The engineers at Chevy were still thinking in terms of economy car, while the consumers were thinking TransAm racing, so there were a lot of garage fixes and aftermarket parts made to improve the steering geometry of the Camaro and the Nova that used the same front end.

What I wonder is how many of the Impala aftermarket front suspension parts are really necessary; since a lot of those same front end parts that were used on the Impala seem to work just fine when used on the Corvette that shared common suspension parts up through the introduction of the C4 Corvette in 1985. How much is need and how much is marketing hype I don't know. I do know that seventy percent of the price you paid is going to buy liability insurance for the "manufacturer" if they were made here in the US.

Big Dave
'Necessary'? Probably not. My original system needed serious work and the lure of a getting a 'better' system for a small investment (I had to spend money on the GM stock system regardless) was too good to pass up. However, if I had known the full cost of the changes necessary to swap out the original power steering system I may not have chosen that alternative.

I knew the Borgeson unit needed +4 degrees of caster (it was clearly stated on the instructions available on-line) but I did not know the GM stock upper control arms couldn't provide that much. Switching to tubular upper control arms with that much caster built in was required. Also, a bigger anti-sway bar is likely needed to finish the job.

When i'm finished, I'll evaluate my decisions. The 14:1 steering ratio is nice, and getting rid of the leak prone GM stock system will make my garage floor happy. I am expecting the 'new' system to be 'better'. Will I find it cost effective? Time will tell. If driving the car is more enjoyable, I'll get over the price tag

I kept all the original parts.
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