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[MightyMouseTech]

Originally Posted by Kgolf31

You are correct on the statement about understeer. Personally I have my front toe set to 0, and the rear is around 7 minutes IIRC

So 0.12 degrees toe in? Never seen an alignment rack that expresses minutes and seconds.

[Kgolf31]

Originally Posted by MightyMouseTech

So 0.12 degrees toe in? Never seen an alignment rack that expresses minutes and seconds.

Yep.

I found my sheet

[MightyMouseTech]

Cool! Is your left rear camber like that on purpose?

[Kgolf31]

Originally Posted by MightyMouseTech

Cool! Is your left rear camber like that on purpose?

The numbers were bouncing around. It is just when the screenshot was captured it was at that value.

[bradleyland]

Originally Posted by JimD

So what should toe be set to for wear to be similar on the rear tires? Why not have it set that way?

Because toe adjustment isn't just about tire wear. It's about handling and safety. Also, toe is not the only factor that affects tread wear.

Tire wear is really simple. Any time a tire is generating force it will wear. The forces a tire is expected to generate are:

• Accelerating - Drive wheels only.
• Decelerating - The front brakes generate most of the stopping force under heavy braking, but at around town speeds, the load is spread more evenly.
• Cornering - Front tires wear faster under cornering, but keep in mind that you spend the vast majority of your time going relatively straight.
• Suspension geometry load (caster, camber, toe) - Amongst these, toe has the greatest impact. Camber affects the way a tire wears, and significant camber angles can really wear a tire unevenly.

To answer your question directly: an unloaded tire will always wear more slowly, so 0° toe will result in the least tire wear. Cars with live rear axles typically have 0° rear toe.

The thing is that toe in/out has a significant impact on how a car handles. In general (and there are limits to this) toe in increases stability, while toe out decreases stability (sometimes desirable). It is, of course, not nearly that simple in reality, but those are the generalities.

Most BMWs run a small amount of toe-in in front and rear. This is fairly typical for production road cars with independent rear suspension. A dedicated sports car might run some toe out at the front, which increases steering feel and makes the car more willing to turn. The trade-off is that toe out can make a car feel squirrely. That's one of the reasons driving sports cars long distances is tiring. They require active steering management to keep them going straight, while a car with more toe in will naturally track more straight.

There is no way to make the fronts and rears wear at exactly the same rate in a RWD car. Even if you ran 0° toe all around, the rears would wear faster because they are used to accelerate the car, while the fronts simply roll along.

[bradleyland]

Damn, I forgot to refresh before posting. Sorry for all the repetition of stuff that has already been said.

[MightyMouseTech]

Also, toe changes as you drive.

The pivot point on the front tires is not in the middle of the tread. The distance between the pivot point and the center of the tread is called the Scrub Radius. The larger the scrub radius, the more the toe changes as you drive. Running the wrong offset wheels really fucks this up. If you had no scrub, the car would wander all over the road.

http://en.wikipedia.org/wiki/Scrub_radius

You can see the scrub radius if you dry steer the tires and then roll the car ahead a bit to see the marks left on the tire.

Like this:



In this pic, you can see the pivot point is towards the inside of the tire from center. That means more force is acting to pull the tire outwards while driving straight, meaning more toe out.

This is often why cars are set with a little toe in, as the wheels will toe out from that position while moving on a RWD car. On a FWD car, the wheels tend to toe in during steady state cruise and acceleration.

[JimD]

Not all rear wheel drive vehicles wear the rear tires out faster. My latest rear wheel drive was my first Suzuki SUV. It had a little motor so it wasn't spinning it's tires but the rears lasted noticably longer than the front tires. My first car, a lot of years ago, was a 1966 Mustang with a 200 cubic inch 6. It also couldn't do a "burn out" or anything approaching that and rear tire life was at least as long as the fronts. Both had solid rear axles. I think that is key. Independent rear suspension has advantages but tire life doesn't seem to be one of them.

[Diver]

Front tires will wear out quickly on RWD cars that go the track a lot.

[CAVU]

I had the alignment last month after having the BMW Performance Suspension kit installed. The shop dialed in a bit more camber than 'factory settings'. For those of you more knowledgable on wheel alignment, I would be interested in any opinions or comments on the new alignment settings:

[bradleyland]

Originally Posted by JimD

Not all rear wheel drive vehicles wear the rear tires out faster. My latest rear wheel drive was my first Suzuki SUV. It had a little motor so it wasn't spinning it's tires but the rears lasted noticably longer than the front tires. My first car, a lot of years ago, was a 1966 Mustang with a 200 cubic inch 6. It also couldn't do a "burn out" or anything approaching that and rear tire life was at least as long as the fronts. Both had solid rear axles. I think that is key. Independent rear suspension has advantages but tire life doesn't seem to be one of them.

True. If you accelerate less forcefully than you brake, the fronts will wear out first because they're doing stopping duty and turning the car. My '84 MR2 hardly had enough power to get out of its own way. It was RWD and wore out fronts first (it had IRS too).

Just keep in mind that you don't have to be doing a burn out to wear the tires under acceleration. Even moderate levels of acceleration will cause tire wear. Engines that generate high levels of torque will make that job easier

[JimD]

Originally Posted by bradleyland

True. If you accelerate less forcefully than you brake, the fronts will wear out first because they're doing stopping duty and turning the car. My '84 MR2 hardly had enough power to get out of its own way. It was RWD and wore out fronts first (it had IRS too).

Just keep in mind that you don't have to be doing a burn out to wear the tires under acceleration. Even moderate levels of acceleration will cause tire wear. Engines that generate high levels of torque will make that job easier

Could be. The first Zuk had a 1.8l engine (it was the "big one" that year). The mustang had a 200 inch 6 but that didn't get you much power in 1966. So neither car accelerated hard. Slight slippage under acceleration would be a reason for more wear on the drive wheels.

[MightyMouseTech]

Originally Posted by JimD

Not all rear wheel drive vehicles wear the rear tires out faster. My latest rear wheel drive was my first Suzuki SUV. It had a little motor so it wasn't spinning it's tires but the rears lasted noticably longer than the front tires. My first car, a lot of years ago, was a 1966 Mustang with a 200 cubic inch 6. It also couldn't do a "burn out" or anything approaching that and rear tire life was at least as long as the fronts. Both had solid rear axles. I think that is key. Independent rear suspension has advantages but tire life doesn't seem to be one of them.

What Suzuki SUV? Are you sure it was not FWD biased? All Honda/Acura SUV's are FWD until the front tires slip.

[bradleyland]

Originally Posted by MightyMouseTech

What Suzuki SUV? Are you sure it was not FWD biased? All Honda/Acura SUV's are FWD until the front tires slip.

Surprisingly, Suzuki still makes RWD SUVs. The Sidekick was RWD, as is the current model Grand Vitara.

[JimD]

Originally Posted by bradleyland

Surprisingly, Suzuki still makes RWD SUVs. The Sidekick was RWD, as is the current model Grand Vitara.

Yep. Sidekick was also body on frame like the older American SUVs. Everything was smaller, of course, but it was like a truck based SUV with a solid rear axle for the drive wheels, and a body on frame construction. The GV is independent rear end and kind of a unit body but there is still a recognizable frame under the body panels. But still clearly rear wheel drive. Engines are not transverse. GV has OK acceleration from a 2.7l V6. Sidekick was a 1.6 or 1.8 l 4. I had the 1.8 - which was still weak. Not much fun but good reliable transportation for me.

[bradleyland]

Originally Posted by JimD

Yep. Sidekick was also body on frame like the older American SUVs. Everything was smaller, of course, but it was like a truck based SUV with a solid rear axle for the drive wheels, and a body on frame construction. The GV is independent rear end and kind of a unit body but there is still a recognizable frame under the body panels. But still clearly rear wheel drive. Engines are not transverse. GV has OK acceleration from a 2.7l V6. Sidekick was a 1.6 or 1.8 l 4. I had the 1.8 - which was still weak. Not much fun but good reliable transportation for me.

My dad has a Samurai as a ranch vehicle. They share some running gear with the Sidekick, and a lot of the stuff is interchangeable. So you had a combination of 0° toe at the rear because of the live axle, and a motor that couldn't smoke those SUV tires at a BBQ. The Suzuki I4 engines of that generation were reliable, but gutless lol

[MightyMouseTech]

Originally Posted by CAVU

I had the alignment last month after having the BMW Performance Suspension kit installed. The shop dialed in a bit more camber than 'factory settings'. For those of you more knowledgable on wheel alignment, I would be interested in any opinions or comments on the new alignment settings:

Does not seem like much toe in in the front. My machine shows spec as (Toe: +0.05- +0.22 degrees) per wheel, or +0.10- +0.44 degrees total toe, as I wrote on the first page. Do you find your car wanders on the highway?

[Kgolf31]

Originally Posted by MightyMouseTech

Does not seem like much toe in in the front. My machine shows spec as (Toe: +0.05- +0.22 degrees) per wheel, or +0.10- +0.44 degrees total toe, as I wrote on the first page. Do you find your car wanders on the highway?

I run 0 Toe and I don't tramline. It really all depends on the tire too.

[bradleyland]

With sufficient caster and the right tires, you can run 0° toe.

I once drove an 84' Celica that (as it turns out) had significant negative toe. I don't remember how much, but it was ridiculous. Like, something was bent to hell in the front end resulting in tons of negative toe in the front. Driving at anything over 25 MPH was impossible. The car would dart all over the place. Insane

[MightyMouseTech]

It's amazing the difference toe makes. After I installed the M3 arms and camber plates, I drove my car around the building a couple times to get everything settled before doing the alignment. The toe was so far out of whack, if I turned the wheel half way to full lock in either direction, the front wheels would "fall over" and self turn all the way to full lock and stay there. Was fighting the wheel like crazy to return to center. Was an interesting drive.

[CAVU]

Originally Posted by MightyMouseTech

Does not seem like much toe in in the front. My machine shows spec as (Toe: +0.05- +0.22 degrees) per wheel, or +0.10- +0.44 degrees total toe, as I wrote on the first page. Do you find your car wanders on the highway?

Thanks Mighty. The shop told me I would find the steering a bit less determined to track in a straight line, and I've found that to be true, but I wouldn't say that it wanders on the highway. I'm a bit concerned about tire wear, but at the rate I'm going the rears will wear out much faster than the fronts anyway.

Originally Posted by Kgolf31

I run 0 Toe and I don't tramline. It really all depends on the tire too.

I'm running PSSs in the stock 18" staggered sizes (215/40 and 245/35) and the car doesn't tramline, but I'm not sure how this alignment will feel when I put the winter wheel/tire set back on, which are also runflats (225/45/17 square).

[MightyMouseTech]

Hmm, will have to try less toe in on my next alignment, maybe at or close to 0.00.