DougKelly20 Posted May 19, 2021 Share Posted May 19, 2021 Hello friends. Through an unfortunate set of circumstances completely not our fault, we lost our beloved 2020 WRX. There was no way we could buy a new one exactly as my girl wanted short of waiting 12 weeks or more for overnight cars from Japan....so we have taken delivery of a new to us, 2018 3.6R. Yes, now there are two in the family. Getting to my point I noticed in the service record a tire had been replaced so I got to measuring and mathing and I didn't like the outcome. Can someone double check my method here and comment? 18 in rims = 451.2mm 225x50 = 112.5mm brand new (sidewall height) Together a new stock setup should measure 569.7. I have no idea how many mm of tread a new tire has but this one has 7mm and the others have 5. Circumference can't be more than 1/4" different, so converted that's 6.35mm C=2Pr, so 284.85x3.14x2=1788.86 new C= 282.85x3.14x2=1776.3 shaved by 2mm. (using radius so I didn't have to solve for more than 2mm) Delta=12.56mm= 1/2" So at this point I'm thinking uh oh...new tires... Right? Link to comment Share on other sites More sharing options...
ammcinnis Posted May 19, 2021 Share Posted May 19, 2021 (edited) Subaru says no more than 1/4 inch difference in circumference, therefore the maximum difference in radius (or tread depth) should be: (0.25 inch) / 2 / pi = 0.040 inch = 1.3/32 inch = 1.0 mm. Perhaps counterintuitively, this holds true regardless of the wheel and tire size. And yes, your measured 2 mm difference in tread depth would equal ~1/2 inch difference in tire circumference. Edited May 25, 2021 by ammcinnis "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
Max Capacity Posted May 20, 2021 Share Posted May 20, 2021 Maybe you could buy three new tires of the same type as that one ? Or play safe and just buy four new tires. It's much cheaper than having the tranny rebuilt. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
DougKelly20 Posted May 21, 2021 Author Share Posted May 21, 2021 I called SOA to get their blessing, and now I'll have to go after the dealership to shave the newer tire or heavily discount a set of 4 new ones. Unfortunately it's been this way for 6000 miles . The lesee didn't know or care.... Link to comment Share on other sites More sharing options...
boxkita Posted May 21, 2021 Share Posted May 21, 2021 get an extended warranty on the transmission and diff along with your four tires. also don't get a shaved tire. it never works out right Build my car Boxkita Track days Link to comment Share on other sites More sharing options...
Grnlantern1 Posted May 21, 2021 Share Posted May 21, 2021 I called SOA to get their blessing, and now I'll have to go after the dealership to shave the newer tire or heavily discount a set of 4 new ones. Unfortunately it's been this way for 6000 miles . The lesee didn't know or care....You just need to Buy 4 Tires.. Achilles on Ebay are pretty cheap and actually a pretty good tire they have 400 Tread Wear and great in the rainy weather Sent from my SM-G988U using Tapatalk Link to comment Share on other sites More sharing options...
DougKelly20 Posted May 21, 2021 Author Share Posted May 21, 2021 Yeah that's what I ended up demanding from the dealership...cept I asked them for a discount on some decent Yokohama's instead of the stock garbage. SOA gave me a case number which I'm sure can be used for extended warranty stuff. Link to comment Share on other sites More sharing options...
chowser51 Posted May 22, 2021 Share Posted May 22, 2021 How many miles on it? Hopefully they give you a deal on some Yokos. if not, if you see snow in your area, look into the new General AltiMAX 365 AW. I'm probably going to put some on my daughter's Subaru when it's time. Or the Nokian WR G4 runflat. Link to comment Share on other sites More sharing options...
DougKelly20 Posted May 22, 2021 Author Share Posted May 22, 2021 Sales woman accepted a discount today on 4 new Yoko's as resolution. I was glad they made it right without fighting me. Link to comment Share on other sites More sharing options...
busyychild Posted May 23, 2021 Share Posted May 23, 2021 Sales woman accepted a discount today on 4 new Yoko's as resolution. I was glad they made it right without fighting me. Hopefully they will be mounting and balancing them for free as well Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
DougKelly20 Posted May 23, 2021 Author Share Posted May 23, 2021 Yes Link to comment Share on other sites More sharing options...
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