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Old 07-22-2014, 04:01 PM   #1
baum
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Do dry, cracked tires need replacing?

I had a blowout and need to know whether it's okay to replace the one tire or are the cracks on the remaining tires a sign they all need replacing. The tread is fine.

I've had the tires 5 or 6 years and they have 15-18k miles. I drive very, very little - 3,000 miles/year at most, once every two weeks.

The car is always outdoors and most of my driving is on brutal NYC streets with gigantic potholes, ruts, and rock-covered streets under construction.

Subaru Outback 2001

I got two conflicting opinions:

1) "YOU DEFINITELY NEED ALL NEW TIRES"

- from an independent tire store, incredibly helpful clerk who discussed my options for a good 20 minutes and explained about cracking and drying and the differences between models of new tires.

--> He also said on AWD you should never replace just one tire - both tires on the axle need to have the same level of tread wear. But this doesn't apply to me because all my tires are too cracked.


2) "YOU'RE FINE FOR A FEW MORE YEARS AND CAN REPLACE JUST THE ONE TIRE"

- from the Subaru dealer's repair department. The guy was apathetic and didn't explain anything; he just said I can do whatever I want. The cracks aren't dangerous now and I've got a couple more years.


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Old 07-22-2014, 06:55 PM   #2
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Re: Do dry, cracked tires need replacing?

Hmm, 9 year old tires, they are done, awd, you need 4.
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Old 07-22-2014, 08:53 PM   #3
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Re: Do dry, cracked tires need replacing?

Thanks.
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Old 07-23-2014, 07:12 AM   #4
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Re: Do dry, cracked tires need replacing?

Yup,

Those tires are toast.

And 9 years besides.

It's time to bite the bullet.

And if you want more of an explanation of what is causing that, just post back.
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Old 07-23-2014, 08:00 AM   #5
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Re: Do dry, cracked tires need replacing?

Quote:
Originally Posted by CapriRacer View Post
And if you want more of an explanation of what is causing that, just post back.
Thanks. From a bit of reading I gather it boils down to the rubber drying out like old rubber bands, due to UV, temperature extremes and dry air - ?

What I don't understand is why infrequent driving will hasten the cracking process. It seems like, UV is UV and if the car's exposed to the elements, it wouldn't make a difference for the tires whether they're moving or not. But something else must be going on.
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Old 07-24-2014, 07:48 AM   #6
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Re: Do dry, cracked tires need replacing?

Quote:
Originally Posted by baum View Post
Thanks. From a bit of reading I gather it boils down to the rubber drying out like old rubber bands, due to UV, temperature extremes and dry air - ?

What I don't understand is why infrequent driving will hasten the cracking process. It seems like, UV is UV and if the car's exposed to the elements, it wouldn't make a difference for the tires whether they're moving or not. But something else must be going on.
All tires are made with antioxidants and antiozidants (AO's for short). They attract oxygen and ozone and consume them, instead of those attacking the long chain rubber molecules. Those AO's are dispersed throughout the rubber matrix, but the AO's on the surface are consumed first. Flexing the tire allows the unused AO's to migrate to the surface to replaced those that have been consumed.

Alternatively, not flexing a tire doesn't allow those deeply imbedded AO's to migrate - so the rubber gets attacked and it cracks.

Of course the AO's eventually are used up - and cracking eventually occurs to all tires.

Just an FYI, there are type of rubber that are relatively immune to cracking and some of those are used in the sidewalls - BUT - those kind don't have the right properties for tread rubber or internal component rubber.

And, yes, heat is a big driver of this process. Tires in Phoenix age faster than tires in Minneapolis.

But moisture (or lack of moisture) is not an issue. Rubber isn't greatly affected by water.
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Old 09-11-2014, 06:24 AM   #7
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Re: Do dry, cracked tires need replacing?

9 years are enough and your tyres need replacement. As you drive occassionaly and that too on very rough and tough roads that is why your tyres have developed cracks because of the standing idle and wear & tear on those bad roads. If you dont replace these tyres then you may have to face problem of tyre burst while driving. Even bad roads need new and good condition tyres.
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