Under hard braking, car gets “floaty”.
02-01-2022, 09:07 PM
#46
Rennlist Member
36/44 is the Porsche recommendation. NOTE : this is for full load ie. 4 persons and luggage with full fuel.
This is the "safe" default used by Dealers, ( who don't know how the car is to be loaded) . It all stems from the Ford /Firestone debacle where the tires were blowing out at speeds due to low tire pressures and causing rollovers/deaths. ( and resulted in TPMS on all vehicles since 2007 )
Tires will blow out due to low pressures (heat) and not over pressure, if MAX pressures are used. "MAX cold pressures" have a safety factor that includes pressure increase due to heat.
In other words running the tire manufactures MAX cold pressure is SAFE, but rides/handles like s**t, lower pressures will ride better/ grip better on turns ( more heat) , but do so at your own risk ( Disclaimer as a Professional ...
)
This is the "safe" default used by Dealers, ( who don't know how the car is to be loaded) . It all stems from the Ford /Firestone debacle where the tires were blowing out at speeds due to low tire pressures and causing rollovers/deaths. ( and resulted in TPMS on all vehicles since 2007 )
Tires will blow out due to low pressures (heat) and not over pressure, if MAX pressures are used. "MAX cold pressures" have a safety factor that includes pressure increase due to heat.
In other words running the tire manufactures MAX cold pressure is SAFE, but rides/handles like s**t, lower pressures will ride better/ grip better on turns ( more heat) , but do so at your own risk ( Disclaimer as a Professional ...
)
02-07-2022, 07:31 PM
#47
Rennlist Member
Thread Starter
Got the car aligned today and it's exactly as Porschetech3 said...spoke with the Indy (Protech) about it and he said "max pressures are covering their ***...but we all know we should run it a little lower else the car will handle like garbage." Turns out that's all it was. After the alignment, tire pressures are 35/40 and it's rock solid. Alignment wasn't much off either apparently. I didn't ask for a print out, but he told me it wasn't far off the mark. Had no idea these were that sensitive to alignments...good to know. Thanks for everybody's input.
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02-08-2022, 03:36 AM
#48
Thanks for posting what it was that caused the effects you noticed. It pays to check the simple things first obviously 
02-08-2022, 09:23 AM
#49
Rennlist Member
Thread Starter
I knew the alignment would probably help just not to the magnitude it did. That’s not a bad thing, it’s actually preferable to me, just an observation.
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02-08-2022, 09:38 AM
#50
Race Car
The really wide tires and short wheel base do make it super sensitive to alignment.
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Nate.Evans (02-08-2022)
02-08-2022, 09:50 AM
#51
Rennlist Member
Originally Posted by Nate.Evans;[url=tel:17960071
17960071[/url]]I knew the alignment would probably help just not to the magnitude it did. That’s not a bad thing, it’s actually preferable to me, just an observation.
02-08-2022, 10:12 AM
#52
Rennlist Member
Nate, glad you got it figured out. You will get to know the car and all its quirks, getting to the point that you will know when something is off and most likely what it is. All part of the fun of 911 ownership. And it is fun!
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Nate.Evans (02-08-2022)
02-08-2022, 01:55 PM
#53
Rennlist Member
It was the tire pressure. A tire shop put 42 up front and 46 in the back and I felt like I was set for the skating rink. Never went back to that shop again. At such high pressure the contact patches are minuscule and sidewalls don’t flex with lateral acceleration. The car will feel like it balances on the head of a pin because weight shift under braking won’t increase contact patch of fronts. Alignment will most affect turn (camber) and neutral steering track (toe), or tramlining, to a lesser extent. 48 psi is what Porsche jacks rears pressure up to for drifting exercises. The 996 is very responsive to tire pressure changes…part of why the darn things are so sweet to drive. After you get more seat time in your car you’ll probably be able to feel if a corner is a couple psi down. Try that experiment and see.
Last edited by hatchetf15; 02-08-2022 at 02:02 PM.
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02-10-2022, 02:10 PM
#54
Sorry, brain farted and should have probably stated current setup.
40 Jahre @72k miles
stock suspension (still on original shocks/springs)
stock brakes (pads have been replaced)
I got brand new tires less than 200 miles ago (Z5s at the oem size). At first I thought it was the old tires as the ones that were on the car when purchased direly needed to be replaced and while it largely went away, probably like 90%, it’s still there. Waiting on getting an alignment as the local indy is booked until the 7th. I’ll be letting him know when I drop it off, but would like to have a general idea.
Car got a 60k mile service at the dealer and had the clutch and brake pads also replaced and the service receipt showed no concerns/notes on the brakes or otherwise. Then again, that’s the same dealer that replaced the clutch and didn’t feel it was necessary to change out the IMS 😂
40 Jahre @72k miles
stock suspension (still on original shocks/springs)
stock brakes (pads have been replaced)
I got brand new tires less than 200 miles ago (Z5s at the oem size). At first I thought it was the old tires as the ones that were on the car when purchased direly needed to be replaced and while it largely went away, probably like 90%, it’s still there. Waiting on getting an alignment as the local indy is booked until the 7th. I’ll be letting him know when I drop it off, but would like to have a general idea.
Car got a 60k mile service at the dealer and had the clutch and brake pads also replaced and the service receipt showed no concerns/notes on the brakes or otherwise. Then again, that’s the same dealer that replaced the clutch and didn’t feel it was necessary to change out the IMS 😂
Don't replace the struts. My struts are 20 years old with 74k and they are still serviceable. Are the bump stops rotten, yes. Would the handling improve if they were rebuilt, yes. Is it worth prematurely replacing for the small handling improvement for a car that doesn't see the track, no.
For $700 and a little elbow grease, this DIY will exponentially improve the handling and "floatiness" of the car.
Last edited by nolift996; 02-10-2022 at 02:14 PM.