Ideal camber for long tire life.

[IveBeenRued]

Short version: I have just installed adjustable rear camber arms and would like to know what the ideal rear camber is for long tread life. I do not care about handling as this vehicle is strictly used as a highway cruiser.

Long version: My Ford C-Max came from the factory with rear camber of -2.2 degrees on the left and -2.4 degrees on the right which were both within Ford's acceptable range of -2.4 to -0.9 degrees. This car has already wore through the inner tread on all four of my Pirelli P7 A/S+ tires in under 40K (rotations every 10K per the manual.) which I believe was caused by the negative rear camber. I installed some adjustable rear camber arms myself and when I got new tires mounted I asked my local tire shop to dial the rear camber in for ideal tire life they set the rear camber to -1.4/-1.5. Does anyone think that my new rear camber measurements will help with my rear tire wear issues or should I dial it in closer to -0.9 or possibly even closer to 0?

 

[Cujet]

Generally, a car with IRS requires some negative camber to prevent severe, and often uncontrollable, oversteer. This negative camber will often result in high rates of wear on the inside, as you know.

There are a few items to think about. The first involves rim and tire width. As this affects the rate of wear on the inboard side. The second involves the fact that some tires have significantly lower rolling resistance with more negative camber. Electric car guys trying to eek out maximum range find that 2.5 degrees negative camber results in lower motor loads in cruise. But fully half the tire life of -1.0 degrees. Not sure it's a good trade off. The third thing to think about is your average load. As the suspension moves up in it's travel (car moves lower) the general rate of camber change may be near 1 degree of negative camber per inch of travel. So if you regularly drive with weight in the car, align it with the typical weight in. Including you.

A guess for your situation: anything -1.0 degrees or less will result in fairly even tire wear. With anything near 0 degrees resulting in oversteer that sometimes cannot be corrected for. An example might be an emergency swerve at highway speeds, where the load shifts hard right, then hard left, the tail swings out and keeps going regardless of steering wheel/front wheel positions. Please don't be that guy.

The safe thing is to pick the factory number -0.9 degrees. But you will likely see improvement all the way to nearly zero. (actually it's about -0.25) that will give the best wear.

 

[Billbert]

For a better answer, I would need to see all the alignment angles front and rear. It is impossible to answer your question with the limited information you have given.

 

[PandaBear]

Had the same problem on Mazda5 when we got it, I can see the dealer just throw in a set of new rear tires to hide the inner wear. Based on forum suggestion I also installed a camber arm and had the mom and pop tire shop set it to the closest allowable amount to 0. We'll see how it goes in a few years.

 

[IveBeenRued]

Originally Posted by Billbert
For a better answer, I would need to see all the alignment angles front and rear. It is impossible to answer your question with the limited information you have given.

Attached as requested.

 

[Nick1994]

Originally Posted by IveBeenRued
My Ford C-Max came from the factory with rear camber of -2.2 degrees on the left and -2.4 degrees on the right


I don't see that as "Before" on that alignment sheet?

 

[IveBeenRued]

Originally Posted by Nick1994
Originally Posted by IveBeenRued
My Ford C-Max came from the factory with rear camber of -2.2 degrees on the left and -2.4 degrees on the right


I don't see that as "Before" on that alignment sheet?


That was prior to the new adjustable rear camber arms. I had the alignment checked at 10K, again around 25K, and then at 56K prior to the new arms. Rear camber was always around -2.2/-2.4 with a little variation depending on the shop.

 

[ARCOgraphite]

Rear toe is still a bit excessive. I would knock that back to total 0.3 deg. Try some swerves or phantom slalom at about 40mph in a empty lot and see how she does. If it wants to swap ends too easily then get more conservative in the rear again.

front Toe loosk great. YIPES! Factory Mega caster in the front. I don't like the feel of big caster in a mac strut car with R&P steer. More like 1.5 - 1.7 deg+

Wonder what they are compensating for? This design have neg scrub? I dont like that either.

 

[PandaBear]

Your toe was likely the cause of the worn rear tires. Your original camber was already pretty close to the minimum factory spec.

 

[Traction]

Originally Posted by Cujet
Generally, a car with IRS requires some negative camber to prevent severe, and often uncontrollable, oversteer. This negative camber will often result in high rates of wear on the inside, as you know.

There are a few items to think about. The first involves rim and tire width. As this affects the rate of wear on the inboard side. The second involves the fact that some tires have significantly lower rolling resistance with more negative camber. Electric car guys trying to eek out maximum range find that 2.5 degrees negative camber results in lower motor loads in cruise. But fully half the tire life of -1.0 degrees. Not sure it's a good trade off. The third thing to think about is your average load. As the suspension moves up in it's travel (car moves lower) the general rate of camber change may be near 1 degree of negative camber per inch of travel. So if you regularly drive with weight in the car, align it with the typical weight in. Including you.

A guess for your situation: anything -1.0 degrees or less will result in fairly even tire wear. With anything near 0 degrees resulting in oversteer that sometimes cannot be corrected for. An example might be an emergency swerve at highway speeds, where the load shifts hard right, then hard left, the tail swings out and keeps going regardless of steering wheel/front wheel positions. Please don't be that guy.

The safe thing is to pick the factory number -0.9 degrees. But you will likely see improvement all the way to nearly zero. (actually it's about -0.25) that will give the best wear.

Here is most of your answer as Cujet said. There is so much more to the whole story.