Ping: Jim Warman re: MM alignment tool

For stability on daily driver cars, I like slightly positive camber with a touch of toe IN. Drag cars get 0° camber with fuel and driver on board and 0 toe with slight pressure applied to the rear of the wheels to simulate the effects of rolling resistance. Guys that really like the "twisty bits" get slightly negative camber and a wee bit of toe out.... as the car heals over in the corner, the tire gets planted on the road better and the toe out helps the car turn into the corner better though it does diddley-squat for straight line stability (even to the point of being a white knuckle experience).

There are some extenuating circumstances..... areas that see a lot of rainfall usually have roads with a higher crown. MacPherson strut and modified MacPherson strut cars don't seem to respond to cross-caster changes as much as they do to cross-camber changes. Rule of thumb..... the car will pull to the side with more positive camber and/or less positive caster. In my area, I have to build in about a half degree or so of cross-whatever (depending on the suspension design I might go with caster, I might go with camber or I might go with a combination of the two) to get a car that's boring enough for most of my customers. SAI and included angle deserve more than a passing glance, as well.

Now for the why on positive camber.... back when everything was unequal length control arm suspension, camber change during jounce and rebound was actually backwards from what most folks thought. During compression, camber would actually go negative... partly to reduce the effects of bump steer, I think. Old ideas die hard so folks on my rack get what I give them.... and that is a car that is boring to drive and tires that last a long time (strangely enough, that's what they wanted anyway).

Manufacturers (Ford, anyway) are on the "sporty" bandwagon with most every car off the line having close to too much negative camber (makes for good numbers on the G-pad). Last year I had a new Marauder that was chewing up $500CA a crack front tires at an alarming rate.... nearly -2.00° camber on the front. I used up all the adjustment I had (even to the point of saying "screw the cross-caster") to get it under -1.00° camber. The traction control system on this car doesn't like anything except stock type tires (different size front and rear and, IIRC, 18" to boot) so there is no changing tire widths... customer is "happier" but not satisfied. Not the way I had planned that one.

The Focus, too..... nice to drive in the summer but with the rear toe they spec'd, a simple patch of ice in the winter was enough to change your laundry schedule.

HTH

** For stability on daily driver cars, I like slightly positive camber with a ** touch of toe IN. Drag cars get 0° camber with fuel and driver on board and 0 ** toe with slight pressure applied to the rear of the wheels to simulate the ** effects of rolling resistance. Guys that really like the "twisty bits" get ** slightly negative camber and a wee bit of toe out.... as the car heals over ** in the corner, the tire gets planted on the road better and the toe out ** helps the car turn into the corner better though it does diddley-squat for ** straight line stability (even to the point of being a white knuckle ** experience).

I believe that stability and performance in the twisties should be a function of driver skill, not of the alignment settings. That same belief extends to other fashionable 'features' such as ABS and traction control. Further, I believe that steering performance should be a function of chassis and suspension design, not of the skill and judgement of an alignment tech.

Oh yes, crowns and road conditions do change the way a car handles. And I'm sure customers bitch when it's not as boring as it should be. I'm not one of them, and I've tried to get this across to the techs around here when I come to call. I'm sure they dislike returns, and I don't blame them. I figured that by doing my cam adjustments, I might get what I need without leaving all concerned a bit puzzled.

** Manufacturers (Ford, anyway) are on the "sporty" bandwagon with most every ** car off the line having close to too much negative camber (makes for good ** numbers on the G-pad).

We agree here. I see this trend everywhere now. But it's gotten to the point where tires that should see 50,000 miles are lucky to make it to 15,000, and it is actually beginning to affect fuel mileage from both rolling resistance and constant loading of the power steering pump.

** The Focus, too..... nice to drive in the summer but with the rear toe they ** spec'd, a simple patch of ice in the winter was enough to change your ** laundry schedule.

I've seen that laundry schedule. My old '89 LX was set up with 3/4" toe out, without my knowledge or approval. A drive up to Lake Tahoe during a snowstorm ended up being a terrifying experience. No matter what I did, that front end wandered anywhere it damn well pleased, and I had almost no steering control whatsoever. The rear was planted just fine, but the front end constantly slid on every patch of black ice without any hope of recovery. It drove so badly (even with chains) that I had to cut the trip altogether. With a zero toe/zero camber that day, maintaining control would have been a simple function of steering input and speed control.

Incidentally, I measured the cam on Charlene's rear axle. A surprising -0.25 neg. camber on both sides. I'm sure if this is a design feature or just coincidental. Back there, I can see where a bit of negative camber would help, but not up front.

-JD

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Obviously, *most* motorists simply want a car that is easy to drive.... one where they can read the paper, talk on the cell, fix their make-up, groove to the tunes and, generally, do everything except pay attention to driving. You like what you like and there is no real necessity for this to be what anyone else likes.

I'd really have to worry about your choice of alignment shops since my idea of way too much toe (in OR out) is much closer to ONE quarter inch than three quarters..... this is would kill a tire just about as fast as you can say OOPS.

For the negative rear camber.... no mystery. Metal is not the solid object everyone thinks it to be.... it is "alive" and has a "personality".... it doesn't take much input for metal to change it's shape ever so slightly..... rigid ain't.