Hey there,
I just had my first encounter with the service department on the weekend. It was for the winter tire placement. I am a bit irked, but not sure if I should be.
Here are the facts:
- Appointment was set for 9:45am, did not come out till 11:30am
- Purchased winter package - Pirelli Sotto Zero Serie II 210 - 215/60/R17/96H
- New rims had sticky substances all around them.
- Front Passenger tire had weights on top of each other, and not stuck flush, a bit of it sticking out. (see attached image)
- Tire pressures (measured underground at around 15C/59F) were varying from 30-38 psi unevenly.
- Contacted dealer service department regarding proper tire pressure for winter tires, was advised to use B Pillar Sticker which had 46/44psi which was meant for the 255/35 R20 Tires. The specs for the tire itself notes a maximum of 44 psi.
And I still don't know how much psi to put into the winter tires.
What do you guys think?
Let me comment on each of your points and some of the others that have chimed in. Just my two cents ...
They shouldn't have been that late, and at least given you the courtesy of a call advising you of their tardiness - especially if over 20 min or so -
The Winter Tire package seems sized correctly for the car (total OD within 5%), but in which case the book takes precedent over the door sticker as to pressures, since they (pressures) vary with tire size: in this case where the size tire you have is NOT in the book, you should be given a supplemental label SPECIFICALLY for that package that you've purchased. WITHOUT such a label, an APPROXIMATE change in recommended pressure can be calculated as a variable compared to the change in TIRE VOLUME between the two tire and wheel combinations. Note that this should be done ONLY when the tires have similar or same load ratings and maximum allowable inflation pressures to start with - as these are BOTH variables that affect differential pressures.
Your new rims should have cleaned well of "sticky substances" to start with.
While weights on top of weights are not attractive, they do work to best balance the tire/wheel - another poster mentioned that you should've had them place the weights behind the spokes - this is NOT possible to do when balancing as weights go where they NEED to go, not just for looks - if that were true, just leave them completely off - The balancer CAN place them in less obvious places or combine/change/move them SOMEWHAT, but if that leads to adding more weights all over, THAT's NOT good either.
Sounds like they did NOT know what pressures to use at all so either winged it or didn't bother to check anything - a DUD!
Just using the sticker for tire/wheel sizes NOT listed is as bad or even worse than not caring at all -
So - back to recommended pressures for a minute : 96H and 97H load ratings are pretty close - at least enough to range pressures.
Original Total OD (in.) = 255*0.35*2/25.4 +20 = 27.03"
Original Total OD Volume = pi*27.03^2/4*255/25.4 = 5760 in3
Original Wheel Volume = pi*20^2/4*9 = 2827 in3
Original Tire Volume = 5760-2827 = 2933 in3
New Total OD (in.) = 215*0.6*2/25.4 + 17 = 27.16"
New Total OD Volume = pi*27.16^2/4*215/25.4 = 4904 in3
New Total Wheel Volume = pi*17^2/4*7.5 = 1702 in3
New Tire Volume = 4904-1702 = 3201 in3
For load ratings the same or similar : P1V1 = P0V0 or P1 = P0V0/V1
V0=2933 in3 P0=44 psi V1=3201 in3
P1 = P0V0/V1 so : P1 = 44*2933/3201 = 40 psi ***
***Provided the Max Inflation pressures are ALSO the same - if not then that needs to be factored into the above number such that :
P0/P0Max ~ P1/P1Max or P1/P0 ~ P1Max/P0Max
So, let's say P0Max = 48 psi and P1Max = 44 psi >> then P1 should be factored by P1Max/P0Max or : 44/48*40 = New P1 = 37 psi
JUST A GUIDE - Drive to FEEL and adjust accordingly - GET SUPPLEMENTAL LABEL FIRST
