19" 991 4S DE tire sizes
02-24-2018, 08:56 PM
#1
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19" 991 4S DE tire sizes
I know there have been a bunch of threads on this topic - I feel like I've read them all - but I'm trying to figure out what size tires to run on my 19" wheels. I'm looking not only for sizes, but for actual brands and models which make said sizes.
I drive back and forth to the track(s) so I need them to be DOT compliant.
For example, I'm currently looking at Pilot Sport Cups in sizes 235/35/19 and 305/30/19, but I'm wondering if the overall diameter of those tires differ too much from the OEM 20" PZeros. I've read threads where too much of a delta there can cause ABS issues and be dangerous.
What will work? What is working for you all you 991S-ers? Looking forward to your ideas!
I drive back and forth to the track(s) so I need them to be DOT compliant.
For example, I'm currently looking at Pilot Sport Cups in sizes 235/35/19 and 305/30/19, but I'm wondering if the overall diameter of those tires differ too much from the OEM 20" PZeros. I've read threads where too much of a delta there can cause ABS issues and be dangerous.
- 20" OEM PZeros @ 245/35/20=26.8"
- 20" OEM PZeros @ 305/30/20=27.2"
- Sport Cup 2 @ 235/35/19=25.5"
- Sport Cup 2 @ 305/30/19=26.2"
What will work? What is working for you all you 991S-ers? Looking forward to your ideas!
02-24-2018, 09:11 PM
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Originally Posted by mgtrackin
I've read threads where too much of a delta there can cause ABS issues and be dangerous.
02-24-2018, 09:25 PM
#3
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Do you mean the difference between the front tire and the back tire diameters within a single setup , or do you mean the difference between stock front tire diameter and track front tire diameter?
02-24-2018, 09:34 PM
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02-24-2018, 09:38 PM
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Indeed - can I run Yokohama AD08Rs with:?
245/35/19 = 25.8"
305/30/19 = 26.2"
They're only 0.4" delta between themselves, but they are a full inch smaller than stock...
Just read your 2nd post - How much front/rear delta is too much?
245/35/19 = 25.8"
305/30/19 = 26.2"
They're only 0.4" delta between themselves, but they are a full inch smaller than stock...
Just read your 2nd post - How much front/rear delta is too much?
02-24-2018, 10:17 PM
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I am no expert on this for your car, just speaking from experience with my Cayman. You will want to have the front/rear diameter ratios as close as possible to stock. Check the stock front diameter, check the stock rear diameter and calculate the ratio. Then compare that to the ratio of your alternate tire set. It should be pretty much the same. There should be alternate stock tire sizes available for your car. That should give you a good indication in terms of a band of deltas.
02-24-2018, 10:20 PM
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I am no expert on this for your car, just speaking from experience with my Cayman. You will want to have the front/rear diameter ratios as close as possible to stock. Check the stock front diameter, check the stock rear diameter and calculate the ratio. Then compare that to the ratio of your alternate tire set. It should be pretty much the same. There should be alternate stock tire sizes available for your car. That should give you a good indication in terms of a band of deltas.
Thank you.
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02-24-2018, 10:35 PM
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Tire Rack suggests 19" tires spec'd with:
235/40/19 = 26.4"
295/35/19 = 27.1"
Within setup delta = 0.7"
Delta between 19" and 20" stock = 0.4"F, 0.1"R
Problem here is that it's difficult to find track-oriented tires sized 295/35/19.
235/40/19 = 26.4"
295/35/19 = 27.1"
Within setup delta = 0.7"
Delta between 19" and 20" stock = 0.4"F, 0.1"R
Problem here is that it's difficult to find track-oriented tires sized 295/35/19.
02-25-2018, 09:25 AM
#9
I ran19s R888 on my 991 for a couple years w no issues - whatever is closest to stock i think it was 255 305. also ran PSC2s w no issue before that.
i would not sweat diameters too much just dont do anything weird. also find a good tyre guy
i would not sweat diameters too much just dont do anything weird. also find a good tyre guy
02-25-2018, 01:53 PM
#10
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Frank is right and you're almost there - just doing the math wrong, it's the ratio between the two, don't disturb the ratio. Here's your math:
20" Front: 26.8"
20" Rear: 27.2"
Front to Rear ratio: 0.9853
19" Front: 25.2"
19" Rear: 26.2"
Front to Rear ratio: 0.9733
difference in ratios: 0.012 < very, very little, you are okay
or you can look at it this way:
20" Front: 26.8"
19" Front: 25.5"
That's a 95.15% reduction in diameter
20" Rear: 27.2"
19" Rear: 26.2"
That's a 96.32% reduction in diameter
difference in ratios is 1.2% or 0.012 < very, very little
You are good to go
20" Front: 26.8"
20" Rear: 27.2"
Front to Rear ratio: 0.9853
19" Front: 25.2"
19" Rear: 26.2"
Front to Rear ratio: 0.9733
difference in ratios: 0.012 < very, very little, you are okay
or you can look at it this way:
20" Front: 26.8"
19" Front: 25.5"
That's a 95.15% reduction in diameter
20" Rear: 27.2"
19" Rear: 26.2"
That's a 96.32% reduction in diameter
difference in ratios is 1.2% or 0.012 < very, very little
You are good to go
04-28-2018, 10:08 AM
#12
There's no problem with rubbing when going this size on a 991.1 C4S? No modifications are needed? Will most wheels with the appropriate widths work, or is something specific required due to clearances?
04-28-2018, 10:35 AM
#13
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FWIW on my 15 GTS I just put together a track set of wheels and tires.
265/35 19 F
315/30 19 R
will let you know after next weekend if any issues but test fit at shop was fine.
265/35 19 F
315/30 19 R
will let you know after next weekend if any issues but test fit at shop was fine.
04-28-2018, 10:44 AM
#14
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