997.1 TT tire size question
03-03-2018, 06:54 PM
#1
Rennlist Member
Thread Starter
997.1 TT tire size question
Greetings all,
I'm new to my 997.1 TT and new to AWD Porsche completely. On my other cars (997s and 964) I never had to worry about the drive ratios of the axles in an AWD system.
It's my understanding that Porsche recommends as OEM a setup of 235/35 R19 front, 305/30 R19 rear. This setup yields a 2.7% delta in tire diameter from front to rear.
I am staying with 19s and just bought a fantastic set of Fuchs from a friend and fellow rennlister (thanks again Andy!), but the tires mounted may present an issue. They're great tires, Pilot Sports, but they are 245/40 R19 front, 275/40 R19 rear. This set up yields a delta of 3.7% between front and rear. 3.7 is an overall big spread, but only 1% off of the spread between what Porsche recommends. Am I thinking of this correctly? Would you guys think I'm ok with the 275/40, 245/40 setup?
Here's the data:
I'm new to my 997.1 TT and new to AWD Porsche completely. On my other cars (997s and 964) I never had to worry about the drive ratios of the axles in an AWD system.
It's my understanding that Porsche recommends as OEM a setup of 235/35 R19 front, 305/30 R19 rear. This setup yields a 2.7% delta in tire diameter from front to rear.
I am staying with 19s and just bought a fantastic set of Fuchs from a friend and fellow rennlister (thanks again Andy!), but the tires mounted may present an issue. They're great tires, Pilot Sports, but they are 245/40 R19 front, 275/40 R19 rear. This set up yields a delta of 3.7% between front and rear. 3.7 is an overall big spread, but only 1% off of the spread between what Porsche recommends. Am I thinking of this correctly? Would you guys think I'm ok with the 275/40, 245/40 setup?
Here's the data:
03-03-2018, 10:10 PM
#2
Personally I sure woudn't. You're getting over an inch less tire width on the rear. With the amount of power this car has, I'm not worried about the discrepancy of the overall diameter with respect from front/back, but the overall handling characteristics and traction available...
. Sounds dangerous to me to lose a substantial percentage of contact patch.... The engineers who designed the car put a lot of time into the wheel and tire size; you're messing with physics way too much IMHO....
. Sounds dangerous to me to lose a substantial percentage of contact patch.... The engineers who designed the car put a lot of time into the wheel and tire size; you're messing with physics way too much IMHO....
03-04-2018, 12:27 AM
#4
Rennlist Member
Greetings all,
I'm new to my 997.1 TT and new to AWD Porsche completely. On my other cars (997s and 964) I never had to worry about the drive ratios of the axles in an AWD system.
It's my understanding that Porsche recommends as OEM a setup of 235/35 R19 front, 305/30 R19 rear. This setup yields a 2.7% delta in tire diameter from front to rear.
I am staying with 19s and just bought a fantastic set of Fuchs from a friend and fellow rennlister (thanks again Andy!), but the tires mounted may present an issue. They're great tires, Pilot Sports, but they are 245/40 R19 front, 275/40 R19 rear. This set up yields a delta of 3.7% between front and rear. 3.7 is an overall big spread, but only 1% off of the spread between what Porsche recommends. Am I thinking of this correctly? Would you guys think I'm ok with the 275/40, 245/40 setup?
Here's the data:
I'm new to my 997.1 TT and new to AWD Porsche completely. On my other cars (997s and 964) I never had to worry about the drive ratios of the axles in an AWD system.
It's my understanding that Porsche recommends as OEM a setup of 235/35 R19 front, 305/30 R19 rear. This setup yields a 2.7% delta in tire diameter from front to rear.
I am staying with 19s and just bought a fantastic set of Fuchs from a friend and fellow rennlister (thanks again Andy!), but the tires mounted may present an issue. They're great tires, Pilot Sports, but they are 245/40 R19 front, 275/40 R19 rear. This set up yields a delta of 3.7% between front and rear. 3.7 is an overall big spread, but only 1% off of the spread between what Porsche recommends. Am I thinking of this correctly? Would you guys think I'm ok with the 275/40, 245/40 setup?
Here's the data:
Cheers
03-04-2018, 02:45 PM
#5
Rennlist Member
Thread Starter
Thanks guys! 🙏 New pilot sports it is!
Forgive the TT newbie question, but is it actually factory stock setup to have a spacer on the OEM 997.1 TT wheels?
Forgive the TT newbie question, but is it actually factory stock setup to have a spacer on the OEM 997.1 TT wheels?
03-04-2018, 03:07 PM
#6
Rennlist Member
Definitely not stock. But, a common addition to oem wheels to get them to look better - more flush with the fenders. They cause no harm at all, and Porsche does sell OE spacers for this very thing.
07-26-2019, 01:34 PM
#7
Burning Brakes
A good friend gave me some Avant Garde ruger mesh wheels while getting them refinished one of the front tires were lost. I ended up buying an new set of fronts 235/35 R19 these now have 9/32 of thread. The rears 305/30 R19 have 6/32's, this is right at the 30% tolerance that Porsche allows.
I worry about the AWD unit however the rears are already taller by .7' from the staggered setup anyone have thoughts if I'm safe?
3/32 seems insignificant but keeping me up stressing weather I should buy new rears too.
Quote below
In case of tire damage such as cuts, punctures, cracks or sidewall bulges that cause a single tire to be replaced for safety reasons, the remaining matching tire on that axle must not exceed 30 percent wear. If the remaining tire has more than 30 percent wear from new, it should also be replaced. This rule applies to all four tires on all wheel drive vehicles. Handling inconsistencies may result if this is not done.
I worry about the AWD unit however the rears are already taller by .7' from the staggered setup anyone have thoughts if I'm safe?
3/32 seems insignificant but keeping me up stressing weather I should buy new rears too.
Quote below
In case of tire damage such as cuts, punctures, cracks or sidewall bulges that cause a single tire to be replaced for safety reasons, the remaining matching tire on that axle must not exceed 30 percent wear. If the remaining tire has more than 30 percent wear from new, it should also be replaced. This rule applies to all four tires on all wheel drive vehicles. Handling inconsistencies may result if this is not done.
Trending Topics
07-27-2019, 08:33 AM
#8
A good friend gave me some Avant Garde ruger mesh wheels while getting them refinished one of the front tires were lost. I ended up buying an new set of fronts 235/35 R19 these now have 9/32 of thread. The rears 305/30 R19 have 6/32's, this is right at the 30% tolerance that Porsche allows.
I worry about the AWD unit however the rears are already taller by .7' from the staggered setup anyone have thoughts if I'm safe?
3/32 seems insignificant but keeping me up stressing weather I should buy new rears too.
Quote below
In case of tire damage such as cuts, punctures, cracks or sidewall bulges that cause a single tire to be replaced for safety reasons, the remaining matching tire on that axle must not exceed 30 percent wear. If the remaining tire has more than 30 percent wear from new, it should also be replaced. This rule applies to all four tires on all wheel drive vehicles. Handling inconsistencies may result if this is not done.
I worry about the AWD unit however the rears are already taller by .7' from the staggered setup anyone have thoughts if I'm safe?
3/32 seems insignificant but keeping me up stressing weather I should buy new rears too.
Quote below
In case of tire damage such as cuts, punctures, cracks or sidewall bulges that cause a single tire to be replaced for safety reasons, the remaining matching tire on that axle must not exceed 30 percent wear. If the remaining tire has more than 30 percent wear from new, it should also be replaced. This rule applies to all four tires on all wheel drive vehicles. Handling inconsistencies may result if this is not done.
The following users liked this post:
jayi836 (07-27-2019)
07-27-2019, 11:59 AM
#9
Rennlist Member
The other ramification is replacing rears-only at 2X the interval of the fronts, means the fronts get awfully old & hard before replacement…
The following users liked this post:
jayi836 (07-27-2019)
07-29-2019, 02:56 PM
#10
Burning Brakes
If you want to buy a front diff run those tires.
I would highly suggest running the factory tire size since they are 19inch wheels.
Also is the offset of the wheels you got for a wide body car?
I would highly suggest running the factory tire size since they are 19inch wheels.
Also is the offset of the wheels you got for a wide body car?
Last edited by o7silverturbo; 07-30-2019 at 01:28 PM.
07-30-2019, 12:20 PM
#11
Burning Brakes
07 turbo- Thanks for your input:
The general question about the AWD unit and the staggered tire sizes as they relate to the overall height, with just replacing just the rear tires while the fronts are good or greater than 6/32 wear? I know this is done all the time on 911's folks will replace the rears perhaps 2:1 from what i have read.
The height difference is .7" front to rear, stock tires 235/35 R19 and 305/30 R19's
The front and rear tires spin at different revolutions normally, I don't think the 3/32 difference will affect the AWD unit. Fronts are 817 rev/mi the rears are 792 revs/mi
I don't understand your comment about frying the diff, it has nothing to do with this topic. where did you get the idea that I have 18" wheels ?
19" silver forged aluminum Wheels are standard on a turbo, yes the offset is the same as the stock wheels.
The general question about the AWD unit and the staggered tire sizes as they relate to the overall height, with just replacing just the rear tires while the fronts are good or greater than 6/32 wear? I know this is done all the time on 911's folks will replace the rears perhaps 2:1 from what i have read.
The height difference is .7" front to rear, stock tires 235/35 R19 and 305/30 R19's
The front and rear tires spin at different revolutions normally, I don't think the 3/32 difference will affect the AWD unit. Fronts are 817 rev/mi the rears are 792 revs/mi
I don't understand your comment about frying the diff, it has nothing to do with this topic. where did you get the idea that I have 18" wheels ?
19" silver forged aluminum Wheels are standard on a turbo, yes the offset is the same as the stock wheels.
07-30-2019, 01:30 PM
#12
Burning Brakes
07 turbo- Thanks for your input:
The general question about the AWD unit and the staggered tire sizes as they relate to the overall height, with just replacing just the rear tires while the fronts are good or greater than 6/32 wear? I know this is done all the time on 911's folks will replace the rears perhaps 2:1 from what i have read.
The height difference is .7" front to rear, stock tires 235/35 R19 and 305/30 R19's
The front and rear tires spin at different revolutions normally, I don't think the 3/32 difference will affect the AWD unit. Fronts are 817 rev/mi the rears are 792 revs/mi
I don't understand your comment about frying the diff, it has nothing to do with this topic. where did you get the idea that I have 18" wheels ?
19" silver forged aluminum Wheels are standard on a turbo, yes the offset is the same as the stock wheels.
The general question about the AWD unit and the staggered tire sizes as they relate to the overall height, with just replacing just the rear tires while the fronts are good or greater than 6/32 wear? I know this is done all the time on 911's folks will replace the rears perhaps 2:1 from what i have read.
The height difference is .7" front to rear, stock tires 235/35 R19 and 305/30 R19's
The front and rear tires spin at different revolutions normally, I don't think the 3/32 difference will affect the AWD unit. Fronts are 817 rev/mi the rears are 792 revs/mi
I don't understand your comment about frying the diff, it has nothing to do with this topic. where did you get the idea that I have 18" wheels ?
19" silver forged aluminum Wheels are standard on a turbo, yes the offset is the same as the stock wheels.
But the tires that you have on the wheels you just got are not the factory size......as said about you need to stay as close to the 2.7 factory split. If you do not it will damage the front diff....that is all im saying.
Its just like any AWD car. You should never put one brand new tire on with three bald ones. You will cause driveline damage