pongobaz

36Fr 44 R is the correct cold temp for 18" wheels with 225/40/18 Fr and 295/30/18 R on the C4S. 2 weeks ago at Mosport, my tire pressure in the rear got up to 52psi after the first run. I dropped them down to 48 psi hot and kept monitoring them after each run. Tire didn't look worse for wear....hmm, maybe I'm not going fast enough.
+1 on a GOOD mechanical gauge.

JDSStudios

max (cold) pressure on all 4 tires on a C4S is 50psi.

You might already know this, but the steering is laser sharp with this
kind of high tire pressure (EDIT: I am referring to the recommended 36/44) in these cars.

JDSStudios

LOL!!
Omar
No aircraft above, and I had cruise control at 105 Km/hr, but I did check against two other gages,
one mechanical and one digital and the temps are correct.
The only difference is the digital gauge shows in .5 increments, and the TPS is
much more accurate with .1 increments.

Sooo, in the digital gauge I may see 44.0 and in the TPS could actually show
43.7 or 44.7. The tires heat up in a inconsistent manner, but they are getting old.
For example the front left heats up more and faster than the front right ,
(could it be my weight, or just a 4 year old tire? - it looks new)

Over all I really love it. No more worries about slow leaks and low tire pressures
sending me crashing around, and no more dirtying my hands with black break dust
just to check the pressure before a trip.

I have no problems like the guys in the GT3 forum, because I can set leak alarms
with a particular pressure per tire (10% lower, 25% or a dangerous 50% lower pressure)
-in every single tire! Love it!

EDIT: The digital read out just displays continually each tire pressure and tire
location (LF, RF, LR, RR) every 2 seconds or so.

John

JDSStudios

I checked this link, and the price is over $200 (249?), and it looks like
you have to take the tires out and install it inside the tires, replacing your
valve stems (I may be wrong).

The one at CT is only $149.00, and you just take your caps out by hand and replace with the sensors.
The only difference is no temperature display on the CT model;

I would like to have the temp display, but the pressure and alarms
are much more vital to me, and partially already give you an idea of
the rise in temperature.

Now, I recently read how nitrogen for several reasons:
molecules are much more dense, so less prone to leaks and moister,
and much more stable with less temperature increase
That is why the pros use it in racing.

I will try nitrogen when I install new tires.

John

Dale Gribble

i have a track day june 1st. i'll install the TPMS from CT put it thru a thorough test.

Imo000

How is the steam affected by the extra weight of the sensor? The centripetal force on the valve stem, at highway speeds, is I think substantial. The added weight can load it up and bend it even more. I know some of the high speed (open road course) cars need to run short valve stems as even just a normal but extended ones, can be a safety factor.

LAT

I installed this system in my 993TT and my CTR-2 and it works great, a couple of points to consider.

1. Stems are too thick for stock rims, but fit fine on my Techart Formula rims and the Ruf rims.

2. Tires must be rebalanced but no issue afterwards, road force balancing a plus.

My reason for installing these is that HP Lieb Ruf test driver and head of service had a blow out at 300 kph while testing an RT12. He saved it but most mortal drivers would not have and I am totally mortal but enjoy crazy speeds. In a legal way of course.

The CT system sounds like a reasonable alternative for price and ease of installation.

LAT

Corner weight of the car can contribute to inconsistent temp gains. You may want to check if not already done so.
I have had the cars set up withing 22 lbs corner to corner and the temp gain is at most 0.5 lb. from side to side

JDSStudios

The CT TPMS kit comes with balancing weights.
John

JDSStudios

LAT
Where did you get it corner balanced, and how did you get the 22Lb figure?

AFAIK corner balancing only makes a big difference in track suspensions.
Think of it as a chair on a cement floor (track suspension), versus
a chair on a carpet (OEM suspension).
John

EDIT: To corner balance the car properly, you should seat in the driver's seat
the whole 3 hours or so, while they do the job.

LAT

I had it done in Minneapolis, the shop uses electronic scales that are set up on the alignment rack. As you know any change in ride height will need a realignment.

The shop uses 20 lb plates and they put 9 of them in the drivers seat on a blanket.

Porsche insists on corner balance with "any alignment" check the service manuals. It makes a big difference if you use the car aggressively on on and off ramps, while braking and any quick lane change maneuvers. IOW when ever you are transferring weight while in motion.

Imo000

That’s irrelevant. I’m talking about the stems themselves. Yes the counter balance will balance the rim but my concern is the added weight at the end of the valve stem. The stem being at the edge of the rim will have significant loading from the tires spinning. The faster you go the more force is applied to the stem. Add the extra weight of the sensor and you might be exceeding the flexing of the stem beyond its design limit.

Dale Gribble

metal valve stems should solve this problem.

JDSStudios

There is no "flexing". It is being pushed in centrifugally 90 degrees to the rim.
The few grams the sensor weighs does not translate to huge Kg of force you somehow picture, even at high speed.

Not a problem at all.
John

Imo000

ok I see!