Correct tire size question

[Topless]

Yes, mount some fresh tires ASAP because 12 yr old tires suck! Ideal sizes for those wheels on a 986 are 235/40/18 and 265/35/18.

Pretty fun discussion on tire diameter differences though. "Twitchiness"??

All 987, 997, 981, 991 run 1" smaller diameter in front than the rear. It adds a little rake to the car so there is more weight on the front tires. This helps to generate excellent car balance in the corners. The idea that all these cars are "twitchy" because of the different diameter has never been discovered until now.

If your car feels twitchy, it needs an alignment.

[KRAM36]

Originally Posted by Topless

Yes, mount some fresh tires ASAP because 12 yr old tires suck! Ideal sizes for those wheels on a 986 are 235/40/18 and 265/35/18.

Pretty fun discussion on tire diameter differences though. "Twitchiness"??

All 987, 997, 981, 991 run 1" smaller diameter in front than the rear. It adds a little rake to the car so there is more weight on the front tires. This helps to generate excellent car balance in the corners. The idea that all these cars are "twitchy" because of the different diameter has never been discovered until now.

If your car feels twitchy, it needs an alignment.

Well you learned something today again then. On a alignment for street car, the tire rotation makes a big difference when you decide to go for a spirited drive. No my car does not need an alignment as I can fell the twitchyness changing the front tire to a smaller faster rotating speed.

People that race, align their cars much different then street cars. Alignments good for race cars are not good for street cars, if you want to have proper tire wear.

"All 987, 997, 981, 991 run 1" smaller diameter in front than the rear."? You are completely wrong in this statement.

[Topless]

Originally Posted by KRAM36

Well you learned something today again then. On a alignment for street car, the tire rotation makes a big difference when you decide to go for a spirited drive. No my car does not need an alignment as I can fell the twitchyness changing the front tire to a smaller faster rotating speed.

People that race, align their cars much different then street cars. Alignments good for race cars are not good for street cars, if you want to have proper tire wear.

"All 987, 997, 981, 991 run 1" smaller diameter in front than the rear."? You are completely wrong in this statement.

Negative ghostrider, stock 981 Boxsters typically run 26" diameter in front and 27" diameter in rear. I ride right seat in a LOT of 987/997/981/991 cars at the race track as an instructor. No twitch, no unusual tire wear as long as the alignment was set up for the type of driving they do.

I drove my street 986 for 10 years and 100 track days experimenting with a lot of different tire sizes, no twitch unless I had too much rear sway bar.

Here are stock sizes for a 2013 Boxster. Note the difference F/R in diameter and revs per mi. Different sizes, no twitch.
https://www.tirerack.com/tires/tires.jsp?tireMake=Bridgestone&tireModel=Potenza+RE-71R&frontTire=345WR8RE71R&rearTire=645WR8RE71RXL&vehicleSearch=true&fromCompare1=yes&autoMake=Porsche&autoYear=2013&autoModel=Boxster&autoModClar=


My 2009 Cayman runs 25"F, 26"R as stock sizes.
https://www.tirerack.com/tires/tires.jsp?tireMake=Michelin&tireModel=Pilot+Sport+4S&frontTire=34YR8PS4SXL&rearTire=64YR8PS4SXL&vehicleSearch=true&fromCompare1=yes&autoMake=Porsche&autoYear=2009&autoModel=Cayman&autoModClar=

Here are stock sizes for a 987.2 Carrera. 25"F, 26" R
https://www.tirerack.com/tires/tires.jsp?tireMake=Michelin&tireModel=Pilot+Sport+PS2&frontTire=34YR8SPTPS2XLN4&rearTire=64YR8SPORTPS2XLN4&vehicleSearch=true&fromCompare1=yes&autoMake=Porsche&autoYear=2009&autoModel=911%20Carrera%20Coupe&autoModClar=

I think somebody has been yanking your chain a bit KRAM.

[KRAM36]

Originally Posted by Topless

Negative ghostrider, stock 981 Boxsters typically run 26" diameter in front and 27" diameter in rear. I ride right seat in a LOT of 987/997/981/991 cars at the race track as an instructor. No twitch, no unusual tire wear as long as the alignment was set up for the type of driving they do.

I drove my street 986 for 10 years and 100 track days experimenting with a lot of different tire sizes, no twitch unless I had too much rear sway bar.

Here are stock sizes for a 2013 Boxster. Note the difference F/R in diameter and revs per mi. Different sizes, no twitch.
https://www.tirerack.com/tires/tires.jsp?tireMake=Bridgestone&tireModel=Potenza+RE-71R&frontTire=345WR8RE71R&rearTire=645WR8RE71RXL&vehicleSearch=true&fromCompare1=yes&autoMake=Porsche&autoYear=2013&autoModel=Boxster&autoModClar=


My 2009 Cayman runs 25"F, 26"R as stock sizes.
https://www.tirerack.com/tires/tires.jsp?tireMake=Michelin&tireModel=Pilot+Sport+4S&frontTire=34YR8PS4SXL&rearTire=64YR8PS4SXL&vehicleSearch=true&fromCompare1=yes&autoMake=Porsche&autoYear=2009&autoModel=Cayman&autoModClar=

Here are stock sizes for a 987.2 Carrera. 25"F, 26" R
https://www.tirerack.com/tires/tires.jsp?tireMake=Michelin&tireModel=Pilot+Sport+PS2&frontTire=34YR8SPTPS2XLN4&rearTire=64YR8SPORTPS2XLN4&vehicleSearch=true&fromCompare1=yes&autoMake=Porsche&autoYear=2009&autoModel=911%20Carrera%20Coupe&autoModClar=

I think somebody has been yanking your chain a bit KRAM.

Not negative. Just because a number goes from 26 to 27 does not make it a full 1", nor does your statement that ALL 987, 997, 981, 991 run 1" smaller diameter in front than the rear hold true.

I can tell the difference, you can't, no big deal.

Only person yanking chains is you. My Boxster is my DD and it's my only vehicle, it's been that way since 2014. I notice everything on my car when something changes. I personally do not like faster rotating front tires, it throws off the balance to me.

I'll will always recommend getting your tires to rotate as close as possible to the same speed. Nothing wrong or illogical in my recommendation and you're not going to change that.

[Topless]

Carry on KRAM...

[maytag]

Originally Posted by KRAM36

My Boxster is my DD and it's my only vehicle, it's been that way since 2014. I notice everything on my car when something changes. I personally do not like faster rotating front tires, it throws off the balance to me.

You remind me of my 1st wife, who swore she could smell cats, when there were no cats.
I think much of what you THINK you notice is what I call "confirmation bias", or a simple psychosomatic response. You expect to feel a difference (you even WANT to feel a difference) and so you feel a difference.
Blindfold you and don't tell you what tires are on (or which quality-brand spark plugs are in the motor) and you won't feel the difference any longer.



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[Topless]

Originally Posted by maytag

You remind me of my 1st wife, who swore she could smell cats, when there were no cats.
I think much of what you THINK you notice is what I call "confirmation bias", or a simple psychosomatic response. You expect to feel a difference (you even WANT to feel a difference) and so you feel a difference.
Blindfold you and don't tell you what tires are on (or which quality-brand spark plugs are in the motor) and you won't feel the difference any longer.



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Oh ya this is spark plug horsepower guy. nuff said.

[KRAM36]

Originally Posted by maytag

You remind me of my 1st wife, who swore she could smell cats, when there were no cats.
I think much of what you THINK you notice is what I call "confirmation bias", or a simple psychosomatic response. You expect to feel a difference (you even WANT to feel a difference) and so you feel a difference.
Blindfold you and don't tell you what tires are on (or which quality-brand spark plugs are in the motor) and you won't feel the difference any longer.



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Change it on my car and I will notice the change without being told.

Why are you even commenting? Do you have a valid reason not to try and match the front and rear tire rotation speed best as possible on a street car? Or are you just being a chain jerkier like Topless?

[maytag]

Originally Posted by KRAM36

Change it on my car and I will notice the change without being told.



Why are you even commenting? Do you have a valid reason not to try and match the front and rear tire rotation speed best as possible on a street car? Or are you just being a chain jerkier like Topless?

Because people use these forums as a knowledge base. If ridiculousness is left unchallenged, it gets defacto credibility.

That's why I'm commenting.

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[Burg Boxster]

Originally Posted by KRAM36

Change it on my car and I will notice the change without being told.

[cough] horsesh_i-t [cough]

And I don't mean switching from summer to winter as you tried to squirrelgoat with earlier... b/c uhhh most anyone w/ a buttometer should notice that. I mean, heck even my wife noticed when I replaced RF tires on her car w/ non-RFs.

Anyhow, all other things being equal (brand, model, width, wheel diam, tire wear, etc), if someone switched rears on a vehicle you are to drive from 40 to 35 series 265s or vice versa without telling you which was on, I'll bet you a steak dinner w/ all the trimmings there's absolutely no way YOU could GUESS (because let's be honest that's ALL you would be doing - GUESSING) w/ more than 50% accuracy (with a statistically adaquate/reliable sample size) which was on after driving a kilometer.

I mean sheesh, after all it IS 13 less rotations per kilometer you insisted w/ great precision. That means every 252 feet you'd feel a rear tire rotate one less time than another. Easy peasy lemon squeezy apparently for you...

https://www.youtube.com/watch?v=fr9ppl2k_3c

I guess I stand corrected. My bad.

But that does beg the question with your F1 career in the balance, how do you find time to post w/ commoners like us here on 986forum.

Good luck in Monaco next week!

[piper6909]

Originally Posted by maytag

Blindfold you and don't tell you what tires are on (or which quality-brand spark plugs are in the motor) and you won't feel the difference any longer.

Driving blindfolded. Now there's an idea! Show us how it's done, Maytag!

[maytag]

Originally Posted by piper6909

Driving blindfolded. Now there's an idea! Show us how it's done, Maytag!

https://beta.washingtonpost.com/technology/2019/01/12/driving-blindfolded-bird-box-challenge-just-dont-officials-say/?outputType=amp


Can't make this stuff up, Haha

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