2002 996 tyre wear
Discussion
I have a 2002 996 Carrera 2, my problem is i had to replace the rear two tyres because of heavy wear on the inner shoulders. OPC said it was due to the tyre pressure to low. I have replaced the two rear tyres and I make sure the pressures are correct, but I notice heavy wear again on the inner shoulders, about one inch in. Would the camber be out? They are 18" and i put 44lb in them.
If you are getting new tyres put on you should look at getting the geometry checked at the same time.
This uneven tyre wear is common, happens on my car too. The only way to get around it is do lots of trackdays or drive the car everywhere on the door handles! It's all to do with the geo being set up to optimise grip on corners, they do this by giving the wheels negative camber. This helps with hooning on the twisties but has a trade off of when driving sensibly on A roads and motorways of wearing out tyres unevenly with the inner tread wearing first.
This uneven tyre wear is common, happens on my car too. The only way to get around it is do lots of trackdays or drive the car everywhere on the door handles! It's all to do with the geo being set up to optimise grip on corners, they do this by giving the wheels negative camber. This helps with hooning on the twisties but has a trade off of when driving sensibly on A roads and motorways of wearing out tyres unevenly with the inner tread wearing first.
NBTBRV8 said:
They all do this, the inners wear twice as quick as the outers. Also you will find that the left rear goes before the right due to the camber in the road.
Absolutely agree - every car that does no have a geo set up optimised to its drivers predominant driving style will suffer uneven tyre wear - that's just simple physics - but a careful geo can prevent/minimise the issue. mollytherocker said:
Thanks for that. It explains my wear!
No it doesn't. It is all wrong. Watch a Porsche from behind go down the road. The rear tires are flat. The rear camber is set the way it is, in fact all the alignment settings are set to what they are when the vehicle is stationary so they will be right when the vehicle is moving, under power, braking, turning.The settings make no sense when viewed from the perspective of the car being stationary. But they make loads of sense when the car is moving.
As long as camber is within the specs it has no effect on alignment. I've run my 02 Boxster's rear camber at the max negative setting and the tire wear along with the car's feel was unaffected. This was as I was assured would be the case by the alignment shop.
Uneven rear (or front) tire wear, that is uneven from tire edge to tire edge, with the wear concentrated to the outer or inner edges arises from incorrect toe in.
With incorrect rear toe tire life can be cut in half, easy. I went from barely 8K miles tire life to over 20K miles with a better alignment.
With the front tires incorrect toe in had me looking at a failed wheel bearing when it was the front tires making the noise from toe setting.
I routinely get 20K or more (23K in one case with my Turbo's rear tires) with a proper alignment. What is proper? I do not specify a street oriented or track oriented alignment, just what ever is standard. Now since I drive on roads that are crowned first one way then the other or not really crowned at all I ask that any crown specific settings not be applied. I like to if the car is on a road crowned down to the right that I have to steer a bit to the left to keep the car straight. And vice versa on a road crowned the other direction. And on a flat uncrowned road I like the car goes straight when the steering wheel is straight.
Several things: Get an alignment from some place that knows these cars. Alignment is more than just setting front toe to bring the steering wheel straight.
Get before and after numbers. Every time I have had a bad alignment -- well the one time -- I failed to get a before and after printout. The result was the alignment stunk and that was the time brand new Turbo rear tires were shot in 8K miles.
Have the fuel tank full of fuel. Have the vehicle empty of junk (weight). If fitted have the spare tire and tool kit properly secured.
Be sure the tire pressures are correct.
Some places like to add weight to the car in place of having a driver in the car when the car is aligned. I have had my cars aligned both ways, with and without any ballast weight and I can't tell the difference and the tire wear is unaffected. AFAIK the factory manual on alignments does not specify any weight be added to the car. The only prerequisites are the items I stated above.
Ideally the best time to get an alignment is with new tires. If the alignment is off the incorrect tire wear and tire shape can affect the alignment outcome.
Be sure to ask the steering wheel be centered.
Oh, unequal tire wear from side to side at the rear of a rear wheel drive car arises from the open differential. In a turn the inner wheel/tire is less loaded. The outside wheel/tire is more heavily loaded. Since the outside wheel/tire must make more revolutions its speed of rotation is higher. This transfers torque to the inner wheel/tire. Being less loaded it will spin. Hence the wear.
In the USA because of right hand drive most turns and the sharpest turns are to right. Thus the inner rear tire suffers accelerated wear. It is not at all helped if the driver has a heavy right foot for this just means the inner wheel/tire will spin more often.
In the UK the opposite is true and the left rear tire is the one that can show more wear than its counterpart on the right side.
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