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Discussion summary
YOUR RESEARCHGripe about 20 inch wheels and tires
Reported or suspected cause
briefly addressed in mt and c&d
Reported cause
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1
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0
Suspected cause
0
Reported fixes
Read evidence and context
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Reported cause
I only know that this issue was briefly addressed in MT and C&D.
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I use comfort pressure which improves the ride but does run the danger of more flats.
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I use comfort pressure which improves the ride but does run the danger of more flats.
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Suspected cause
Don't know if this is simply because the summer P zeros have stiffer sidewall although I suspect the extra sidewall in the 19s help.
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Suggestion
Lot of folks like you and on ******** highly recommend the MP4S over the P zeros.
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My C4S came with standard 20 inch wheels and tires. I am now using 19 inch winter wheels and tires. Despite the frost heaves and buckled pavement, the car rides much better on the 19s. Don't know if this is simply because the summer P zeros have stiffer sidewall although I suspect the extra sidewall in the 19s help. Read as much. Handling is fine even with the performance snows.
Porsche
doesn't offer an option to minus size your wheels with the S models which may be a good option for folks living in pothole country regardless of the season. Instead the dealers try to sell you wheel and tire insurance. A Youtuber posted a video about a flat in his
911
4s equipped with 20 inch winter wheels and tires. Also mentioned he gets multiple flats every year. Seems like a waste. First pay extra for insurance. Second, put up with a harsher ride. Third, if rims get bent and tires damaged, they are thrown away and replaced with new ones (a waste). Never mind the hassles of dealing with flats and who comes out ahead. It seems to me at least that
Porsche
should offer smaller wheels as no cost options for the S models. The base
Carrera
comes with the 19s. Maybe this belongs in WOTD.
Would love to hear apples to apples, comparing the same model tire in the two sizes. My 914 seems to have a far better ride than the BS on its 20s. But so many factors...
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Yes, apples to apples comparison would be good. I only know that this issue was briefly addressed in MT and C&D. Makes sense that extra sidewall would offer a more compliant ride but the brand of the tire cannot be discounted. I have always had better luck with ride quality with Michelins.
This may not completely solve your problem, and I don't mean to suggest that a 20" tire could be as comfortable as a 19" one, but I just replaced my
Pirelli P-Zero
N0 spec tires with the newest N0-spec
Michelin Pilot Sport 4S
, and the new tires have a more comfortable ride quality (to me). Is it as good as a 19" tire? Probably not, but I personally wouldn't switch to a 19" anyway. But maybe switching to Michelins after the P-Zeros wear out may help you?
Thank you. yes I have been thinking of dumping the P zeros (mine are N1s) for the Michelins come spring. Price is 1650 from my dealer and 200 bucks for installation. My hesitation is that the P zeros only have 2500 miles on them but I don't like them at all. (Hated them in my
981
BS as well. )
However, seems like a shame to dump them but should I drive on them for another 2-3 years if the Michelins are so much better? On a brand new
911
, it seems a shame too not use better tires.
Porsche
now is shipping new
911s
with the new Michelins.
I could use 19s in the same Michelins (but not N rated) which would mean use my
Porsche
19 inch rims for both winter and summer tires. Then I will have an extra set of 20 inch rims. I am not sure what I am going to do but am leaning to keeping the 20 inch rims and changing over to the Michelins and gift the P zeros to the dealer. Lot of folks like you and on ******** highly recommend the MP4S over the P zeros.
Well on the positive side the 20's look good. lol As to ride harshness, this is a no brainer. On my
981
CS with
Conti
's there is 2" of side wall on the front and 2 1/2 in the rear. Since the 19" will have the same diameter tires within tenths of an inch, they will have 1/2" of additional side wall. Thats 25% more side wall on the front and 20% more on the rear. That is a significant difference! With out a doubt that will result in a much smoother ride and probably fewer damaged wheels. I say "probably" because pot holes in California are starting to rival the east coast.
20s give you fewer choices for track tires. The P4S fit perfectly, but I upgraded to the Cup2s and do get a bit of rub. Given a choice, I'd pick 19s for tire options.
On my
911
, the standard sizes are 245/35/20 fronts (3.4 inches sidewall) and 305/30/20 rears (3.6 inches sidewall). Minus sizing to 235/40/19 and 295/35/19 gives 3.7 and 4 inches of sidewall respectively. Small difference but ride is much better with winter performance tires. I am sure tire construction and tire brand will make a difference. I just don’t have a direct comparison of the same tire in these different sizes.
My just arrived
GTS
w/Spasm came with
Michelin Pilot Sport 4S
tires (245/35/20 & 305/30/20), and it feels like a luxury car compared to my '15
Cayman S
w/Sport Suspension and 20's (
Pirelli
). The funny thing is I didn't feel the
Cayman S
was bad.
I just measured the sidewall of the 305 rears on a 12" wide wheel, and it is right at 2.75" from the floor, and of course that is compressed. I've never had a problem on a low profile 20 here, but I suppose my opinion might be different if I stilled lived in NH, where I grew up.
The calculated sidewall height is about 3.6 inches. That is a lot of compression for a high performance tire with a stiff sidwall. Max tread depth is about 0.28 inches.
What is the measurement on top? Also, are you running regular or comfort pressure?
Unrelated, all the new Michelins must be being bought up by
Porsche
in these sizes. They have been back ordered from TR for a while now.
My C2
GTS
with SPASM feels more comfortable in normal mode than my previous
Cayman GTS
w/
X73
suspension (w/
Pirelli
's). However with the "sport chassis" engaged, it feels very much the same.
The sidewall on my
Michelin
rears 305 on 11.5 inch wide wheels is a bit more than 2.5 inches at the bottom. They're a bit more than 3 inches at the top. Rear tires are at 45 psi.
Funny,
Porsche
appears to be moving toward fitting their cars with Michelins while
BMW
seems to be going the other way.
That is what is recommended in the manual.
Page 345 | 2017 911 Carrera Manual | Porsche iManuals
34/44 full load and 31/39 comfort pressure for the 20 inch wheels and tires.
Should add, full pressure, it is like riding on run flats in my 4S with P zeros. Also, the pressures creep up to 49-50 psi on warm days. This is at the max pressure limit on these tires.
I use comfort pressure which improves the ride but does run the danger of more flats.
