missing linc
Loose nut behind the wheel
I can understand why an all wheel drive vehicle would need to have all 4 tires wearing evenly, but I don't see any reason for it with a fwd or rwd only.
Do you change all four of your tires?
- Thread starter tom999w
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Moving the goal posts are we? How does the number of cars in ditches change anything? Oh, and what's your source on that information? Casual observation of your neighborhood?
You were whining about having to change all 4 tires, well, whether or not a car ends up in a ditch doesn't change the fact that all cars nowadays have speed sensors and ECU's that control traction, braking, etc. And the presence of those things is what determines whether or not the car needs its tires changed in pairs or all 4 at once. Whether it works or not to keep the car out of the ditch is irrelevant, how the sensors read data and how the ECU interprets it is what makes the tire height differences significant.
Again, it depends entirely on what sensors are on the car, how the ECU is using that data, etc. In general it shouldn't matter for a FWD or RWD car, but because of advanced ABS and traction control features I wouldn't be surprised if there are FWD or RWD cars out there that are sensitive to tire height changes that could mean changing all 4. If you don't know what sensors are on the car and what the ECU is doing with that data, you may not be making a good decision.
So, I guess that people nowadays keep their tires inflated properly? Seems that could change diameters (actually, radius) and screw up them thar fancy puters!
Oldiron440
Big blocks rule small blocks drool!
A couple of years ago I needed to replace the front tires on my daily a 08 Ford Expedition with auto 4x4. I had aggressive Goodyear E 285/70/17 on it from when I used it for work. But the front tires were shot and the rear tires had years worth of tread left on them. I wanted to go with a hywy tread but at $400 per tire I couldn’t swing all four in one shot so I ran the new front tires for about six months before I switched the rear tires. There was no issues with anything including ABS, traction control or even the automatic 4WD.
I use the Expedition for pulling multiple different trailers including my 30’ camper so the tire selection is necessary, the bonus was getting 75K out of the tires.
I use the Expedition for pulling multiple different trailers including my 30’ camper so the tire selection is necessary, the bonus was getting 75K out of the tires.
Well that has a transfer case. Totally different animal.
harrisonm
Well-Known Member
I knew that different sized tires were a big problem with all wheel drive and 4 wheel drive vehicles, but I had no idea that wear differences between same size tires was also a problem.
Something with a transfer case ain't near as picky as something AWD with a viscous coupling. Heck, I've seen 4x4 guys run different sizes and even different gear ratios front and rear to get what they're lookin for in the mud. It works good sometimes.
Oldiron440
Big blocks rule small blocks drool!
yes on an all wheel drive vehicle you should replace all the tires at one time. Now if I had a tire that was not repairable and all the tires only had 7k on them I would replace just the one.
BSB67
Well-Known Member
What an entertaining thread.
My friend has a sophisticated late model Audi. He is not mechanically inclined. His dealer stories are priceless. He has a new one every six months. I’d say $1500 is typical. I think oil changes are like $350.
My friend has a sophisticated late model Audi. He is not mechanically inclined. His dealer stories are priceless. He has a new one every six months. I’d say $1500 is typical. I think oil changes are like $350.
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I find it interesting that the speed sensor can supposedly tell 1 tire turned 1 less rotaton in over a mile but the coupling of the AWD cant handle it. What am I missing?
Not a thing. I believe you got it.
It seems to me, there is deniability if the AWD fails due to some customer caused issue. Oh, didnt you read the manual? It says you can only use Tires made in the month of October. Sorry, warranty has been voided. Had it not been leap year, then those tires would have been in spec
It's not about a date stamp. It's about the physical diameter, which is a very legitimate point. It's the buyer's job to learn about what they are buying.
I meant that as being some obscure way to deny warranty. It was mentioned above somewhere about manufacture dates all being equal as a recommendation. If that is the case, then it is a design problem. In all these cases, with mm of difference causing failures, its a design issue.
I know, but that's not what they use it to do. It's a legitimate concern. Insurance companies are going to try to deny regardless of whether you follow the rules. We already know that.
a $350 oil change is not other worldly expensive in the grand scheme of things. especially with high end euro cars.
let's say he's got an A8 with a 4.0
that's 9L of full synth at $12 a quart plus a $25 filter so you're at like $150. throw in an air filter, a few o-rings, crush washers, some air box wax, disposal, tax, envro fee and presto there's $200 easy money. labor's easily that balance at $150/hr to bring it out to $350
Daughters Mazda CX-3 AWD doesn't use TPS's to tell you you have a soft tire. It monitors tire rotation differential, so a soft tire (or a worn tire) is a different diameter and sets it off and I'm sure does no good to her drive train components.
Yes, because on some of those cars you'd get multiple different warning lights if your tire got that low. Just see post #45. On pretty much everything you'd get an air pressure alarm from your TPMS, and on an AWD you'd likely get a secondary alarm from the differential or something telling you your traction control was out of sync, possibly an ABS light as well. Different manufacturers run different sensors and feedback systems, but on a full time AWD with traction control you're dash would light up like a christmas tree if your tire diameters were out of whack. So yeah, you'd keep the tires inflated properly. Or have to tune out a lot of blinking and dinging.
Absolutely not, depending on the car.
As @dadsbee just pointed out, there are actually multiple ways a modern car could reasonably measure tire diameters and inflation levels, from TPMS to comparing VSS values. And yeah, running around with a low tire on an AWD car could totally burn up a differential, again, depending on the car and how it's set up. Which is why it could trigger an alarm on those vehicles.
The most entertaining part of this thread is seeing the people that clearly have absolutely no clue how some of the basic sensors and ECU's work on newer vehicles. Guys that probably fancy themselves as pretty mechanical just talking straight out of the wrong sphincter on some of this stuff.
How do they account for tolerances in manufacturing? Can't tell me every tire is manufacturered to the EXACT same diameter. But I guess there is a sensor for rhat!!
And except for bias ply tires I STILL DO...
That's why on AWD vehicles with the viscous coupling, the manufacturer recommends getting a set of sequential serial number tires, to assure they are from the same batch. We're not makin this stuff up, I promise.
had one the other day on an AWD nissan. nail in the tire was throwing a TPMS light, tire got low enough to trigger the traction control and ECU responded by sending it into limp mode-- i'm guessing so that you couldn't drive it fast enough to hurt it or make it dangerous to drive.
i only found this out after i'd swapped the rim/tire figuring i'd get the guy out the door and to work-- with instructions to come back at lunch after i'd have time to repair or replace the tire. the car wouldn't even leave the lot. i wound up putting him in another vehicle in the fleet while i played guessing games for a few min before hooking it up to the scanner. sure as **** the dashboard was a x-mas tree and the DTC list was TMPS, TC, input on values/signal for diff/trans and a ABS light for good measure.
icing on that cake was having to do a sequence of driving cycles in order to reset the TC & input valves. sheesh.
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