996 Turbo Tire Ratio Calculator
#16
You're using the OEM size for the fronts, but not the OEM size for the rears. If you use the OEM sizes, Michelin PS2s are:
829 revs per mile front
832 revs per mile rear
Bridgestone S-02 As (also an OEM fitment) are:
823 revs per mile front
837 revs per mile rear
So... presumably... the PS2s might cause less front diff wear and tear.
Either way, if an OE tire is different front to rear by 14 revs per mile, you can probably assume that level (or anything less) is within the acceptable safety range.
829 revs per mile front
832 revs per mile rear
Bridgestone S-02 As (also an OEM fitment) are:
823 revs per mile front
837 revs per mile rear
So... presumably... the PS2s might cause less front diff wear and tear.
Either way, if an OE tire is different front to rear by 14 revs per mile, you can probably assume that level (or anything less) is within the acceptable safety range.
#17
To comment on a few posts above- the proposed sizes 225/40 with 315/30 has a 12 rev per mile mismatch- FOUR TIMES the heat and impact on the differential.
(Common issue- people want to upgrade sizes, but don't want to have to replace the fronts when there is so much tread left... )
This is the root of the issue of using outer diameters- you get stuck on %s, and lose sight of the issue which is the revolutions the diff must turn to compensate.
A
#18
The revs per mile is more precise, in terms of a published number. The published spec is in 0.x or one tenth. I would not be surprised if the PS2 in OE sizes (225/40; 295/30 is within one tenth- yet has a 3 revs per mile 'mismatch')
To comment on a few posts above- the proposed sizes 225/40 with 315/30 has a 12 rev per mile mismatch- FOUR TIMES the heat and impact on the differential.
(Common issue- people want to upgrade sizes, but don't want to have to replace the fronts when there is so much tread left... )
This is the root of the issue of using outer diameters- you get stuck on %s, and lose sight of the issue which is the revolutions the diff must turn to compensate.
A
To comment on a few posts above- the proposed sizes 225/40 with 315/30 has a 12 rev per mile mismatch- FOUR TIMES the heat and impact on the differential.
(Common issue- people want to upgrade sizes, but don't want to have to replace the fronts when there is so much tread left... )
This is the root of the issue of using outer diameters- you get stuck on %s, and lose sight of the issue which is the revolutions the diff must turn to compensate.
A
Said differently, the PS2s in 225 and 315, apparently are still a closer match than the OE Bridgestones in 225 and 295. So less heat and impact on the front diff than an acceptable OE solution.
Honestly though, if someone wants to run the 315 rear, they really should upgrade to the 235s in front (i.e. go to the full 996 GT2 fitment - not just the rears). JMHO.
#19
The OE Bridgestones, in the OE 225/40 and 295/30 fitments, are 14 revs per mile different.
Said differently, the PS2s in 225 and 315, apparently are still a closer match than the OE Bridgestones in 225 and 295. So less heat and impact on the front diff than an acceptable OE solution.
Honestly though, if someone wants to run the 315 rear, they really should upgrade to the 235s in front (i.e. go to the full 996 GT2 fitment - not just the rears). JMHO.
Said differently, the PS2s in 225 and 315, apparently are still a closer match than the OE Bridgestones in 225 and 295. So less heat and impact on the front diff than an acceptable OE solution.
Honestly though, if someone wants to run the 315 rear, they really should upgrade to the 235s in front (i.e. go to the full 996 GT2 fitment - not just the rears). JMHO.
#20
To comment on a few posts above- the proposed sizes 225/40 with 315/30 has a 12 rev per mile mismatch- FOUR TIMES the heat and impact on the differential.
(Common issue- people want to upgrade sizes, but don't want to have to replace the fronts when there is so much tread left... ) A
(Common issue- people want to upgrade sizes, but don't want to have to replace the fronts when there is so much tread left... ) A
i find myself obsessing about this, but i attribute that to my car having thrown the abs/psm CEL after switching the sizes! so i will probably be switching out the fronts sooner than i'd have liked or necessarily "needed". if only i would settle for the hankooks again this'd be a non issue! thanks for the input also.
#21
The OE Bridgestones, in the OE 225/40 and 295/30 fitments, are 14 revs per mile different.
Said differently, the PS2s in 225 and 315, apparently are still a closer match than the OE Bridgestones in 225 and 295. So less heat and impact on the front diff than an acceptable OE solution.
Honestly though, if someone wants to run the 315 rear, they really should upgrade to the 235s in front (i.e. go to the full 996 GT2 fitment - not just the rears). JMHO.
Said differently, the PS2s in 225 and 315, apparently are still a closer match than the OE Bridgestones in 225 and 295. So less heat and impact on the front diff than an acceptable OE solution.
Honestly though, if someone wants to run the 315 rear, they really should upgrade to the 235s in front (i.e. go to the full 996 GT2 fitment - not just the rears). JMHO.
#23
the gt2 fitment would be my sizes of choice. i've run sets of pirelli's/hankooks and ps2's on two different tt's, and the ps2's are my preference. ymmv.
#24
I dont think the tirerack has actually mounted these tires and had someone roll them down the street counting how many times it rotates over a mile..
#25
I dont think it is. I suppose it is an easier relationship to understand. Rotations per mile is just a calculation derived from the diameter.
I dont think the tirerack has actually mounted these tires and had someone roll them down the street counting how many times it rotates over a mile..
I dont think the tirerack has actually mounted these tires and had someone roll them down the street counting how many times it rotates over a mile..
#26
#27
rotations per mile =1 mile(5,280ft) / circumference of tire (2(pi)r)
But, again you need the true (measured) diameter.
#28
my dilemma, absolutely.
i find myself obsessing about this, but i attribute that to my car having thrown the abs/psm CEL after switching the sizes! so i will probably be switching out the fronts sooner than i'd have liked or necessarily "needed". if only i would settle for the hankooks again this'd be a non issue! thanks for the input also.
i find myself obsessing about this, but i attribute that to my car having thrown the abs/psm CEL after switching the sizes! so i will probably be switching out the fronts sooner than i'd have liked or necessarily "needed". if only i would settle for the hankooks again this'd be a non issue! thanks for the input also.
Going to 235+315 really doesn't change the 'balance' so no big change in understeer, IMO. Y
Anyway....