2015 Rogue SV all wheel drive, 193,400 miles, original CVT, 225/65R17 Michelin Defender T plus H with about 20,000 miles left in them. picked up a drywall screw in the right rear sidewall on Government Street friday. sidewall, so nobody is patching it, i know that part.
tire shop wants to sell me four. the man was decent about it and did not oversell, he said on an all wheel drive car with a CVT they will not install one tire, shop policy, because a mismatch cooks the drivetrain. 688 dollars for four installed.
the other three measured 6/32 on his gauge. the new one would be 10/32. so my question for the people here who do this for a living: is the four tire rule real on a car like mine, or is it a policy that exists because it is easier than explaining the actual tolerance to people? losing a transmission over 300 dollars would be stupid. so would spending 688 dollars in august on a car with 193,000 miles on it.
Nissan's own site has the owner manuals in the owners section and the wording in mine is vague enough to support either argument, which is probably on purpose.
real, but not for the reason he gave you, and the detail matters because it changes what you should buy.
the coupling does not care about tread depth. it cares about rolling circumference, which is to say how many times each tire turns per mile. different circumferences front to rear means the coupling or the clutch pack is being asked to slip constantly to make up the difference, and slipping is where the heat and the wear come from. the number most manufacturers land on is roughly a quarter inch of circumference difference, which works out to about 2/32 to 3/32 of tread depth.
your system is a part time coupling that lives at the back axle and normally sends very little power there. that is more forgiving than the symmetrical setup i work on all day, where everything is connected all the time. but 6/32 against 10/32 is 4/32, which is past the number, and the difference you have is front axle against rear axle, which is exactly the one the coupling feels.
that last bit is why "just buy two and put them on one end" is the wrong instinct here. two matched new tires on an axle fixes a side to side mismatch and creates a front to rear one. your options are honestly four tires, or one tire shaved down to match the other three, which is a real service but not one most shops offer any more.
service desk view, since i write these estimates for a living.
shops quote four because the manufacturer's language gives them no cover to do anything else, and because the customer who buys one tire comes back in eight months with a drivetrain noise and wants it to be the shop's fault. it is not a scam, it is a liability policy. you can still negotiate inside it.
what i would do: ask them to measure all three remaining tires with a depth gauge and write the numbers on the estimate, not on a sticky note. if they come back 7/32 instead of 6/32 the conversation changes. and ask whether they can source one tire and shave it, because the answer tells you whether you are talking to a tire shop or a tire counter.
the other half of this is what you are protecting. at 193,000 miles on the original coupling and the original CVT, the thing you are trying not to break is not a thing anybody is going to rebuild economically. that is an argument for spending the 688, not against it.
the math is worth having in front of you because it makes the tolerance concrete.
tread depth is a radius, so each 1/32 of an inch of depth is two 32nds of diameter, which is pi times that in circumference. call it about two tenths of an inch of circumference for every 1/32 of tread. so your 4/32 difference is around eight tenths of an inch of circumference, against a tolerance that is usually written as a quarter inch. you are three times over.
my shop measured circumference directly with a tape wrapped around the tread rather than trusting a depth gauge, which i thought was fussy until i watched two of my tires measure the same depth and a sixteenth apart on the tape.
bought four. not happily, but bought four.
what decided it was priya's point about what i am protecting, plus a phone call. called a second shop and asked about shaving, and the kid on the phone had to ask somebody what that even meant, so that answer was no. so it was four Defender T plus H, 688 installed, and they measured and wrote the old depths on the invoice like she said: 6, 6 and 7. the 7 was the spare, which has never been on the ground.
i am keeping the best two old ones in the shed. if i pick up another screw in six months i will have something to put on that is within a hair of the others, and that is 200 dollars of insurance for free.
i will be the anecdote, and then i will tell you why the anecdote should not change your mind.
my neighbor ran a CR-V all wheel drive for two years on a 3/32 mismatch after a nail, no noise, no failure, sold the car at 140,000 and the next owner is still driving it. that happens, and the people on the forums predicting a grenade in every case are wrong.
but you were betting 300 dollars of savings against a coupling and a CVT that cost more than the car is worth to replace, on a car with 193,000 on it. i would have made the same call you just made and i have less patience for tire bills than anybody here.
follow up nobody asked for. 1,100 miles on the four new tires and the whine i have been blaming on the CVT since march is gone. completely gone.
it was the old tires. the two fronts were cupped on the inside edges, which i could feel with my hand once the tire guy showed me how to run it across the tread, and it made a hum at 60 that rose and fell exactly like a bad bearing or a tired transmission. i have spent six months quietly budgeting for a CVT that is apparently fine.
mileage is up about a mile and a half a gallon too, which over the life of a set of tires is not nothing. i am still annoyed about the 688 dollars. i am less annoyed than i was on the 13th of august.
