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Yoko S-Drives - Tire hardening question

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(edited)
9 hours ago, Einspritz said:

 

In broad general terms, a wider tire will not have any larger contact patch than a properly sized "skinny" tire due to the fact that the tire will compress under the same weight of the car at that corner. What WILL change is the shape of that contact patch e.g. under braking or cornering.

 

The wet performance of a tire is as much or more due to the tread pattern and the ability to evacuate water for hydroplaning purposes, such as "instant" for say puddles or consistent such as a really wet road. The composition of the rubber vs. the tarmac is also a great factor.

 

A strictly great rain tire will probably have similar characteristics as a dedicated snow tire.

 

Unfortunately, we must choose between one or the other for optimal performance or compromise.

 

The reality with '02s nowadayze is that you (we) just don't drive a whole lot of miles to wear out the tread; I have a set of Dunlops from 15 years ago on my rims and the car has been in storage for the past 12 years. So, the expense is just something you have to deal with, but I don't agree with the "4 year" rule.

 

Theoretically, a wider tire will allow you to use lower air pressure and that would give you a larger contact patch. The coefficient of friction increases as the pressure at he contact patch decreases. Formula one tires are inflated to just a little over 20 PSI. Of course they are very light cars (1616 Lbs minimum).

Edited by allbim

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Yikes...contact patch, tire width, temperature and pressure....getting into airspeed unladen swallow territory. 

Absolutely Loved my Conti Extreme Contact Sports on my RS4. (Daily Driver). Stickier than Oregon Clay on my dog..... 

Hated the soft compound and spending $$$$ every 20K miles to replace them.

Found some balance in my Yin/Yang by going to Hankooks Ventus S1 Noble 2's Cheaper, almost as sticky and very good braking in the wet here in the good Ol' Pacific Northwest....

I have had them for quite some time, tread wear has been nearly nil for well over 4 years. 

But what do I know? I ain't no Toby.....

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Thanks for the info on some summer 15" tires.  

 

Here's some notes on the Dunlop Direzza ZII 185-60-14 tires on my tii (installed June 2016):

Great all-around tires for being summer performance ones.  Aired up to 37-38 psi, they are great on twisty roads and for Autocross sessions.  Air pressure reduced to 34-35 psi, they perform fantastic on road trips and even in the rain.  I forgot to reduce the air pressure prior to driving to Dobson, NC with Andrew Wilson last Thursday. We drove thru very heavy rain in NC and the car experienced hydroplaning on several Interstate sections (granted the amount of standing water was excessive and Andrew also had issues (believe he is running 13" Kuhmo tires)).

 

 

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you really can't go wrong with ANY of the modern summer performance tires.

 

the key is changing the mindset about replacement. 99% of 2002s will not wear out the tread on tires.  they just don't get driven enough.  the tires will AGE OUT.  after a few years, soft summer performance tire rubber compounds get hard and the "stick", especially in rain or cold conditions, drops significantly.  that is a fact of life folks need to get used to.  just because a tire has lots of tread doesn't mean it is still a safe or good tire.  02 tire replacement should be based on the date code on side of tire, not tread depth.  

 

i have a set of s.drives on nice RB wheels that are 10 years old.  they only have maybe 1500 miles on them.   they are rock hard.  they are perfect for keeping my 02 off the shop floor in winter storage!  or...toby's drift demo idea....hmm...i need to find a deserted parking lot....

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11 hours ago, allbim said:

...The coefficient of friction increases as the pressure at (t)he contact patch decreases...

 

What?  The coefficient of friction is what it is (at temp T).  The force of friction varies as the load varies.  The only time you get more grip when you decrease the load is if you're on the wrong side of the peak (tire is already overloaded and you take some off, then you get more grip.)

 

(Really quick image stolen from the interweb.)

Image result for tire graph grip load

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3 hours ago, irdave said:

 

What?  The coefficient of friction is what it is (at temp T).  The force of friction varies as the load varies.  The only time you get more grip when you decrease the load is if you're on the wrong side of the peak (tire is already overloaded and you take some off, then you get more grip.)

 

(Really quick image stolen from the interweb.)

Image result for tire graph grip load

 

"The coefficient of friction is what it is".  Oh how I wish it were that simple. Yes, it pretty much is what it is when you have 2 solid surfaces in contact with each other. Even then you have a difference between static and dynamic friction. Everything changes when you have an elastomer like rubber INTERLOCKING with a rough surface. Your graph, while true, does not relate to this phenomenon; it simply illustrates the difference between rolling and sliding friction.   

 

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The four year rule is probably quite correct for performance tires, six years is considered the end for normal street tires by the German TUV. I have heard that properly stored unused tires age only when you start to use them in reality. On the other hand, the difference between cheap tires vs. performance tires that are past their expiration date is probably not that big...but the expectations on them are different. My toyos were hopeless in the rain to begin with, ok, my Yokohama a021r were great...until they aged. The toyo owner doesn't know what they missed, but may not have missed anything because the car was never in the rain or was only driven in a straight line...I am surprised by people who spend a lot of money on their cars, then skimp on the tires and brakes. It's kind of a sign of priorities / needs if your running 8 year old tires and 15 year old flex hoses....On a car at auction it does raise question marks, where else did they skimp? 

Andrew

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