freene55

I replaced all 4 of my tires a couple of weeks ago - the front 2 seemed to be losing air /slow punctures and were down to 3mm and the rear two were at 2mm

so i had all 4 change before i got my MOT

Like for like replacements P-Zero only difference being the front 2 are N1 and the Rear two are N0

tire pressure before replacement was 31 fronts and 39 rears as per Porsche standard


after replacing the tires i now have less grip than before - i checked the tire pressure which are now at 31 front and 40 rear (going to drop that down to 39 tomorrow)

It feels like there is less grip now i am running the new tires - slight understeer in bends which i didnt have before and i dont get that feeling like its on rails like i had before.

also now when i doing a slow turn out of my drive and dont get the driving on acrons sounds like the tire are gripping the road - it just turns smoothly now.

any advise would be great - as i thought the new tires would improve the grip :> (well that was the plan)

Thanks

PatrickC23

I wouldn't make a judgment until you break them in - I believe they say tires need about 500 miles to get fully broken in and grippy.

Edit - from Tirerack site

"Tires are comprised of many layers of rubber, steel and fabric. Due to these different components, your new tires require a break-in period to ensure that they deliver their normal ride quality and maximum performance. As tires are cured, a release lubricant is applied to prevent them from sticking in their mold. Some of the lubricant stays on the surface of your tires, reducing traction until it is worn away. Five hundred miles of easy acceleration, cornering and braking will allow the mold release lubricant to wear off, allowing the other tire components to begin working together. It is also important to note that your old tires probably had very little tread depth remaining when you felt it was time to replace them. As any autocrosser or racer who has tread rubber shaved off of his tires will tell you, low tread depth tires respond more quickly. Don't be surprised if your new tires are a little slower to respond (even if you use the exact same tire as before). Their new, full depth brings with it a little more tread squirm until they wear down."

DerekS

I agree with PatrickC23, new tires are almost dangerously slippy - chill on them for a good 300-400 miles.

STG

Try 31/34 cold

You just need to get used to the new ones and get a few miles on them. Right off the bat they may be a bit slippery I assume being new.

LexVan

Normal. You just need time to scrub off the mold release.

Pmorritt

Like he said. New shoes need to be scrubbed in. When I get new shoes for my bikes , I have them mounted and then scrub the tread with a Scotch Brite pad. M/C places alway warn riders " take it easy with lean angles for first 100 or so miles.

jennifer911

As Patrick pointed out, people will sometimes get rubber shaved off the tread of new road tires for autocross. You went from 2mm tread depth to 11 or 12 mm of depth, and consequently now have more tread squirm. Given it’s the same model of tire, the ultimate amount of grip will be the same, but you are just getting a tiny bit more under steer with the initial turn in. On cool mornings, super high performance summer tires will all give that “driving on acorns crunch sound” in slow 90-degree turning maneuvers and yes it is more pronounced with worn tires. Could it be that the temp has risen since you changed tires?

Grandma will need 500 miles to wear off the mold-release wax from a new set of tires; most Porsche owners can usually do it in 5 or 10 miles.

chuckbdc

My car was slippery on P1s with 40lbs in the rear, even after break in.

A 4 lb difference front to back will give you far better handling that the large diff you now have.

STG991's suggestion is right on.

991carreradriver

You got that right.

Cristophosphorus

+1. Give it some time and reduce the tire pressures. The "feel" will come back soon.

Al.Fresco

Great advice. Here is an interesting read about 991 tire pressure Full Load vs Comfort.
http://www.edmunds.com/porsche/911/2...-pressure.html

Larry Cable

until they are heat cycled they are bound to be slippery

dflowerz

Holy crap! I was driving on an 80 degree day on the highway and tires were hot, but pressures were 45 front and 49 rear! That is getting into bicycle tire pressures. Let the tires cool down and looked like around 40 front and 45 rear cold, at 78 degrees. The manual has lower settings even at full load. Anyway I set the tires to 31 front 35 rear at 78 degrees ambient temperature. Will be over a week before I have time to drive the car again. Thoughts? 991.2 C2s.

Vise

Rears are too high, go with 31/34 or even as low as 30/32. Highly recommend you stick with the comfort pressure settings.

dflowerz

Ok. I originally typed 31/45 when I meant 31/35. Since edited. Will drop the rears one more psi. Should help ride quality a ton.