[I’ve been searching for this info forever with no success and finally have some answers. Thought I would share my findings in case they would help any others looking for help, although I admit they are not entirely conclusive.]
Below are the specifications and and approved/recommended snow chains for each tire size:
18" Aero, 235/45R18, 26.3" diameter, 9.3" section width
Approved chain: Pewag Servo Sport RSS76, requires 7mm inside clearance
pewag servo sport
19" Sport, 235/40R19, 26.4" diameter, 9.5" section width
Approved chain: Pewag Servo RS77, requires 12mm inside clearance
pewag servo
Tesla is very clear that the snow chains are only compatible with their respective tire sizes.
I've always wondered why the same chain size is not approved for both wheel/tire sizes. The diameters are very, very close and the chains are designed to ratchet in and support multiple sizes. Additionally, the tire diameters mentioned above are only valid when the tires are brand new. As they wear, the diameters decrease by .20" to .25", which itself is more than the .10" difference between the 18" and 19" tires.
Rhetorical questions (unless you all have actual answers!):
In any case, after not finding much concrete info, I ended up ordering the RSS76 as I currently have the 18" Aero wheels with stock tires. Didn't make much sense to order anything else. They came in a couple days ago and what do you know... the tag says they work with both 235/45R18 and 235/40R19, among other sizes.
This is very strange! Pewag's Tesla-specific tag says right on it that it is OK for 235/40R19! More confusion!
As a I said in the preface, my findings aren't entirely conclusive. I can think of some reasons why they need to be different, but then I keep thinking of counter-arguments that lead me in circles. Perhaps only the testing or QA group responsible for these recommendations / approvals would be able to shed light here.
If anyone has a photo of the RS77 tag, please post it. It would be interesting to see if 235/45R18 is listed as a compatible size.
To be continued...
Below are the specifications and and approved/recommended snow chains for each tire size:
18" Aero, 235/45R18, 26.3" diameter, 9.3" section width
Approved chain: Pewag Servo Sport RSS76, requires 7mm inside clearance
pewag servo sport
19" Sport, 235/40R19, 26.4" diameter, 9.5" section width
Approved chain: Pewag Servo RS77, requires 12mm inside clearance
pewag servo
Tesla is very clear that the snow chains are only compatible with their respective tire sizes.
I've always wondered why the same chain size is not approved for both wheel/tire sizes. The diameters are very, very close and the chains are designed to ratchet in and support multiple sizes. Additionally, the tire diameters mentioned above are only valid when the tires are brand new. As they wear, the diameters decrease by .20" to .25", which itself is more than the .10" difference between the 18" and 19" tires.
Rhetorical questions (unless you all have actual answers!):
- Why can't the RSS76 stretch just a tiny bit and support the 19" Sport size?
- Why can't the RS77 ratchet down just a smidge tighter and support the 18" Aero size?
- Assuming there is a good reason for different sizes, why doesn't Tesla recommend both Servo RS76 and RS77 or both Servo Sport RSS76 and RSS77 for 18" Aero and 19" Sport, respectively? Why recommend different model lines for different sizes?
- Assuming there is a good reason for the different model lines, why does the larger tire (19") use the chains that require MORE clearance (Servo, 12mm)? If anything, the larger tire, with less clearance, should require the lower-profile chains (RSS, 7mm) and vice versa, i.e. 18" Aero and 19" Sport should use RS76 and RSS77, respectively. This is completely unintuitive!
In any case, after not finding much concrete info, I ended up ordering the RSS76 as I currently have the 18" Aero wheels with stock tires. Didn't make much sense to order anything else. They came in a couple days ago and what do you know... the tag says they work with both 235/45R18 and 235/40R19, among other sizes.
This is very strange! Pewag's Tesla-specific tag says right on it that it is OK for 235/40R19! More confusion!
As a I said in the preface, my findings aren't entirely conclusive. I can think of some reasons why they need to be different, but then I keep thinking of counter-arguments that lead me in circles. Perhaps only the testing or QA group responsible for these recommendations / approvals would be able to shed light here.
If anyone has a photo of the RS77 tag, please post it. It would be interesting to see if 235/45R18 is listed as a compatible size.
To be continued...
