Do I Need a New Tire? - Check Tire Wear at 40K Miles

[Chronos]

Front tires suffer from edge wear for obvious reasons - they move - which is why rotation will prolong tire life. Differential wear on one side signals you have an alignment problem. Unless you weigh over 200 kg, passenger weight is not an issue. The suspension system balances the load. Get your alignment checked. Proper alignment will do more to improve tire life than almost anything else.

 

[Borek]

The issue to address is that it contradicts the common advice that you should rotate your tires. Look, I get the logic of what you guys are saying. It does make sense. What I want to know is why I've never heard this before and instead I hear everywhere that you should rotate your tires!?

I don't see a (serious) contradiction. Rotating tires guarantees uniform wear, so the difference between wear on back and front is never large enough to be of a real importance. Problems start when the differences are large.

 

[jim hardy]

1. Can't tell from the photos whether the inside edge tread is worn down like the outside edge tread.
If both edges are worn more than the center that's under-inflation, just one edge is alignment.
2. On a front drive car you want the best tires on the rear. Reason is in wet slippery conditions you need the rear tires to behave like a rudder.
http://www.tirereview.com/always-install-two-new-tires-on-the-rear-axle/

Draw a free body diagram of the car viewed from above...
When you take your foot off the gas, the front wheels are now pushing backward.
On the slightest deviation from straight ahead(yaw), the cg is no longer aligned with the front wheels' center of effort.
Forward force (MA) against cg isn't aligned with opposing force from front wheels, so you have a "couple" that tries to rotate the car. More rotation makes the couple bigger.
Rear wheels need to have traction so they can exert sideways force to oppose the rotation.

So the question is, which axle do you want to lose traction last? The one that causes rotation or the one that opposes rotation? Put the new tires there.
Front drive cars with bad tires have a propensity in wet conditions to swap ends.

 

[russ_watters]

I don't see a (serious) contradiction. Rotating tires guarantees uniform wear, so the difference between wear on back and front is never large enough to be of a real importance. Problems start when the differences are large.

Unless you blow two front tires in 3 days like I just did. That's part of why I'm asking. My car now has tires with 30,000 miles on them on the back and new tires on the front. The advice I'm getting here suggests I am doing that wrong. While my manual doesn't explicitly have this situation, it implies even wear is important and never mentions putting new tires on the back if even wear becomes unworkable.

The manual's advice would seem to have very limited applicability because as soon as something happens to make the wear uneven, you'd never get it back under the new tires in back theory.

 

[dlgoff]

I was thinking that rotating tires was probably more important when tires weren't as well constructed. But after seeing how much I don't know about tires, I'm sure I'm wrong.

 

[Borek]

Unless you blow two front tires in 3 days like I just did.

I see your point. But this is a fubar situation, so no wonder it is not covered but the standard army manuals

 

[russ_watters]

OK, I think I have a solution: I'll get the old tires put on the front. They don't have much tread left and will need to be changed before next winter. The new tires on the back will still be fairly new after 10 months, so next winter I'll have new tires on front and almost new tires on back. Then I can ease back into a normal rotation schedule.

 

[xxChrisxx]

Pootling round at low speeds in the dry, it really doesn't matter what you do.

The reason for having more grip at the back is the fronts will let go first, and understeer is easy to deal with.

Snap oversteer is more likely to lead to brown trousers.

Tyres are such a minor cost of motoring, but the single most important part of the car in terms of control. It doesn't make sense to eek out a few more miles from a set, or put on ditch finders.



Rotation was more important with crossplys. Modern radials really don't need it. It's more a habit that hasn't been shaken yet. Like oil changes every 3k miles. It's just not necessary with modern parts.

 

[cjl]

Rotation was more important with crossplys. Modern radials really don't need it. It's more a habit that hasn't been shaken yet. Like oil changes every 3k miles. It's just not necessary with modern parts.

As has been mentioned before in the thread, rotation can still help prolong tire life if your driving patterns are asymmetric, especially if they're asymmetric and you drive aggressively. There's a pretty substantial tire wear difference between my left and right tires when I take my car to the track, for example (which has more right turns than lefts).

 

[russ_watters]

It's more a habit that hasn't been shaken yet. Like oil changes every 3k miles. It's just not necessary with modern parts.

While I have your attention, what do you think about oil changes intervals on a turbocharged car...? I've heard that keeping the schedule (5k miles in my manual) is more important because the turbocharger runs fast and hot and has a lower tolerance for bad oil.

And the recommended grade is 5-30 or 5-40, which seems to be available in both synthetic and dinosaur from some vendors...

Suggestions?

 

[cjl]

While I have your attention, what do you think about oil changes intervals on a turbocharged car...? I've heard that keeping the schedule (5k miles in my manual) is more important because the turbocharger runs fast and hot and has a lower tolerance for bad oil.

And the recommended grade is 5-30 or 5-40, which seems to be available in both synthetic and dinosaur from some vendors...

Suggestions?

For a turbo car (or any modern high-performance engine), I'd definitely go synthetic over dino. As for intervals, it's hard to say, since it's really dependent on the engine and on how the car was driven. If you're really curious though, you can always send in your used oil for analysis with these guys, which will tell you how much life it had left: http://www.blackstone-labs.com/

 

[xxChrisxx]

While I have your attention, what do you think about oil changes intervals on a turbocharged car...? I've heard that keeping the schedule (5k miles in my manual) is more important because the turbocharger runs fast and hot and has a lower tolerance for bad oil.

And the recommended grade is 5-30 or 5-40, which seems to be available in both synthetic and dinosaur from some vendors...

Suggestions?

It depends on the type of driving you mainly do. But definitely a synthetic oil, due to the temperatures.


Some oils are designed for fixed service life, which will be short. So if you are mainly doing lots of short journeys you may as well use the cheaper oil and change it more often. 5k change

Eg. Castrol Magnatec, VW Quantum Synta.

Long life oil works best if you mainly do motorway miles on a variable service interval. Lots of long hot running. Changes at 10 - 15k.

Eg Castrol Edge, VW Longlife.



Old mineral oils desperately needed to be done every 3k. You have a lot more wiggle room with synthetics.

At the end of the day you should go by the manual, they will have a manufacturers spec.

In my BMW I use Castrol, in my Golf I use the VW stuff.

 

[leroyjenkens]

Unless you weigh over 200 kg, passenger weight is not an issue.

Actually, I weigh about 220 kg. I've picked up dancing as a hobby to try to get some of that weight off.

Just got a price quote from somewhere else of $434.02 for 4 tires, an alignment, road hazard on the tires and free rotations whenever I want them.
That beats my dealership's price quote of $550. After reading this thread, I may just get the 2 front tires replaced, but I still have yet to do the penny test on any of them.

I tried TireRack.com, but with shipping, it would be about the same price to just buy from a local store.

The tread wear seems to be only on the outside edge of the left front tire, so I think that may be an alignment issue and having never rotated the tires in the 40k miles I've been driving the car. I bought it new, and the tires are the originals.

Actually, I only weigh about 80 kg.

 

[xxChrisxx]

I doubt your alignment is out, or if it is, it's not far out. The left front is loaded during right hand turns. Which going from previous posts high load right handers are morr common in the US (highway slip roads etc).

The difference in wear from those pics is not that much considering 40k miles and no rotation.

 

[Astronuc]

When I got an oil change at my car dealership, I was told that my car needed new tires. I've had them since I got the car 40,000 miles ago. They said that they were "in the red", which I took as meaning they needed to be changed immediately. Well, when I got the car home, I looked at the tires and they all looked fine to me. My front driver's side tire seemed worn more than the others, though. I guess that's because of 99% of the time, it's just me in the car.
Just by looking at the pictures, would you say they'd need to be changed? I could understand replacing my front driver's side tire, because that one looks pretty worn, but I see no justification in replacing all of them just because one is worn a lot.
The first picture is my front passenger's side tire (All the tires basically look like this except for the front driver's side tire), and the second picture is my front driver's side tire.
Thanks.

They look pretty worn, and they may not have been rated for 40K or 50K miles. A lot depends on how one drives and how one maintains pressure. I would expect that one risks hydroplaning with those tires.

I meant completely bald. I've seen tires on friends cars that had essentially zero tread.

I've seen the same.

Not all states do inspections (auto regulations come from the states) and even then they are at best annual, so there is no way the government can know for sure how much tread is on your tires -- and those tires in the OP looked pretty thin.

Such matters as automobile inspection are set by state (and city in some cases). NY has a tread height minimum.

I'd recommend new tires, to ensure safety to oneself and others.

 

[lisab]

I'd recommend new tires, to ensure safety to oneself and others.

Heartily agree. But if that's too much trouble, just get a new car.