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Old 03-29-2018, 04:33 PM   #1
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4 New Tires installed but different specs?

I just had my Tire guy order and install new rubber on all 4 corners.
I went with the Michelin Pilot SUPER SPORT. I noticed that the specs on the Rear tires are 101Y and the Front tires are 95Y. Otherwise all specs are the same.
Will this cause problems of any kind, ride, handling,durability ect.Thx

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Old 03-29-2018, 04:37 PM   #2
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What does the Y mean
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Old 03-29-2018, 05:07 PM   #3
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Y means that the tire was tested in excess of 186mph. I think you are good :-)
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Old 03-29-2018, 05:07 PM   #4
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What does the Y mean
I believe the Y is the load rating
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Old 03-29-2018, 05:30 PM   #5
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The load rating is the number. The letter is speed rating.
101 = 1819 pounds.
95 = 1521 pounds.
Y = 186mph.

You're good.

Last edited by particlewave; 03-29-2018 at 05:32 PM.
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Old 03-30-2018, 02:03 PM   #6
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A little further explanation:

The tire load index specifies the maximum weight that a tire can carry (per the tire manufacturer). The same model/size of a tire can have different load indexes (like 95 vs 101) because the tire construction is slightly different between the two tires. Back in the old days, this usually meant they the two tires had a different number of plies but that's not really true in modern tires where the strength of an individual ply can vary.

The load index difference within a tire model/size has little effect on tire performance factors like grip, wear, or handling so it is highly doubtful that you will notice any difference in those characteristics between a 95 and a 101 load index tire.

The reason why using 95 or 101 load index tires on your Boxster doesn't matter is because neither of those tires is anywhere near their maximum load capacity when installed on a Boxster.

101 index = 1819 lbs/tire x 4 tires = 7,276 lbs total weight (car + passengers + cargo)
95 index = 1521 lbs/tire x 4 tires = 6,084 lbs total weight

For example: If two heavyweight people were to take a trip in a Boxster with 500 lbs of luggage each, the total weight would be something like: 3,200 lbs car + two x 300 lb passengers + 1,000 lb luggage/cargo = 4,800 lbs. This is still substantially less than 6,084 lbs or 7,276 lbs so it doesn't matter which set of tires (or mix of 95 or 101 load index tires) is on the car.

You'd have to fill both trunks with cement to get the total weight anywhere near the load index maximums!
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Last edited by thstone; 03-30-2018 at 02:16 PM.
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Old 03-30-2018, 04:45 PM   #7
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Quote:
Originally Posted by thstone View Post
A little further explanation:

The tire load index specifies the maximum weight that a tire can carry (per the tire manufacturer). The same model/size of a tire can have different load indexes (like 95 vs 101) because the tire construction is slightly different between the two tires. Back in the old days, this usually meant they the two tires had a different number of plies but that's not really true in modern tires where the strength of an individual ply can vary.

The load index difference within a tire model/size has little effect on tire performance factors like grip, wear, or handling so it is highly doubtful that you will notice any difference in those characteristics between a 95 and a 101 load index tire.

The reason why using 95 or 101 load index tires on your Boxster doesn't matter is because neither of those tires is anywhere near their maximum load capacity when installed on a Boxster.

101 index = 1819 lbs/tire x 4 tires = 7,276 lbs total weight (car + passengers + cargo)
95 index = 1521 lbs/tire x 4 tires = 6,084 lbs total weight

For example: If two heavyweight people were to take a trip in a Boxster with 500 lbs of luggage each, the total weight would be something like: 3,200 lbs car + two x 300 lb passengers + 1,000 lb luggage/cargo = 4,800 lbs. This is still substantially less than 6,084 lbs or 7,276 lbs so it doesn't matter which set of tires (or mix of 95 or 101 load index tires) is on the car.

You'd have to fill both trunks with cement to get the total weight anywhere near the load index maximums!
All of this is dependent upon adequate air pressure to support the load also.
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Old 03-31-2018, 06:56 AM   #8
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All of this is dependent upon adequate air pressure to support the load also.
No...............
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Old 03-31-2018, 07:07 AM   #9
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Originally Posted by thstone View Post

You'd have to fill both trunks with cement to get the total weight anywhere near the load index maximums!
And at that point you'd be sitting with the suspension completely bottomed out and the wheel wells likely sitting on the tires! The load rating would be the least of your worries.
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Old 03-31-2018, 12:46 PM   #10
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Originally Posted by Starter986 View Post
No...............
Is it possible you can elaborate your response to do more than waste space?
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Old 03-31-2018, 04:10 PM   #11
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Originally Posted by particlewave View Post
The load rating is the number. The letter is speed rating.
101 = 1819 pounds.
95 = 1521 pounds.
Y = 186mph.

You're good.
^^ This!

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