5/32" is definitely noticeable. I had new tires on the rear, and old tires on the front, and there was a 5/32" difference between the two... Stability control kept freaking out on sweeping curves, even at low speeds.
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Replacing ONE tire
- Thread starter Pianewman
- Start date
Yes. It was when I had a staggered setup and needed to replace the rears, so I installed Michelin Pilot Sport AS3 on the rears. I left the old Michelin Pilot Sport AS3 on the front, which were 5/32" < then the new ones on the back... Every time I took a sweeping turn at 30-35 mph, the stability control lights kept flashing and the car kept braking one of the corners.. I took the car back the next weekend, and replaced the front two tires and the problem went away.
Even Discount Tire told me they have seen this issue before, and had no problems pro-rating the warranty on my front two tires... I have been replacing all 4 tires now every 20-25k miles now, and they've been pro-rating the warranty every time... It shouldn't be that far fetched... The ECU has sensors for steering angle, and it can measure the wheel rotation on each corner. The ECU only complained when I was taking curves.
After I replaced the fronts, I can take that same curve at > 70mph without the stability control making a peep. I even made sure to go to the exact same sections of road that gave me issues.
If you go to the BMW and Infiniti forums, they say the same thing. When I was more involved there were a lot of topics with regards to staggered setups and making sure you stayed close to the OEM ratio of the front/height vs back/height to avoid problems... If you wandered too far and made the ratio too wide between the front and rear tire height, you had stability control issues. (The oem staggered setup was to have a slightly taller tire in back then the front)
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That's good to know the Tesla isn't picky in that way, makes it easier. BMW and Infiniti sure aren't that way, lol.
Hi All
its me again, I have just picked up a nail in the drivers rear tyre (Ms pilot sport 235/35/20), took to the shop to get repaired but They never had a tyre in store so to get me home we had to replace with a 245/40/20 part worn as I only live 4 miles from the tyre shop. Thats when the fun started the car started to make all sorts of funny noises not mechanical but what seemed like electronic it’s sort of hard to describe the sound like a lot of computer Wizardry going on adjust stuff mainly from the front drivers side. The model I have is 4WD would the size in tyre cause the computer system to have a melt down and will I have the same problem when I but the two new tyres on when they are in. More importantly am I doing any damage to the car, it’s parked on my drive now and the next journey will be 4 miles back to have the tyres changed out. The tyre pressure indicator is still showing low and the traction control light did come on once or twice on the way home.
kind regards
D
its me again, I have just picked up a nail in the drivers rear tyre (Ms pilot sport 235/35/20), took to the shop to get repaired but They never had a tyre in store so to get me home we had to replace with a 245/40/20 part worn as I only live 4 miles from the tyre shop. Thats when the fun started the car started to make all sorts of funny noises not mechanical but what seemed like electronic it’s sort of hard to describe the sound like a lot of computer Wizardry going on adjust stuff mainly from the front drivers side. The model I have is 4WD would the size in tyre cause the computer system to have a melt down and will I have the same problem when I but the two new tyres on when they are in. More importantly am I doing any damage to the car, it’s parked on my drive now and the next journey will be 4 miles back to have the tyres changed out. The tyre pressure indicator is still showing low and the traction control light did come on once or twice on the way home.
kind regards
D
Watts_Up
Well-Known Member
Following up on what Watts_Up said, a larger diameter can really confuse the car's traction control sensor. The effect would be that the car will use braking on one of the other wheels to compensate for what it sees as wheel spin. If you drive for a little while with this happening, you can put your hand near (not on, that could burn) the brakes and they'd likely feel hot.
If it were me, I'd probably take the slowest route that I could back to the tire shop. It wouldn't be good to go too far with it constantly engaging traction control like that, assuming that is what is happening. I'm not sure why it would make exactly the noises you are describing, though.
A tire rolls on its reinforcing belts, not on the outside diameter. With different size tires you have a much different reinforcing belt diameter.
This is very different than the previous situation, where the same size tires had different wear. Even with different height tread blocks they still had exactly the same belt diameter and thus very similar rolling diameter.
You aren't doing damage to the vehicle, it is simply that the traction/stability control system is very upset and abandoning its job.
(Yes, clutch type differentials can experience wear with differing wheel speed, but that isn't the case here.)
Watts_Up
Well-Known Member
The issue with tires of different diameters, and thus different circonference,
on the same axial, is that on a straight line both wheels will have a different speed rotation.
So the traction control will try to slow down the wheel spinning faster
using the brake to send more power to the other wheel.
This issue was demonstrated by EV Dave on those youtube videos using Modern Spare Tires:
1) Using a Model 3 Modern Spare Tire on a Model Y
255/45-19
135/80-18 -> -5.4%
2) Using the new updated Model Y Modern Spare Tire on a Model Y
255/45-19
145/85-18 -> - 1.1%
Note what happens at 15:20. It's not on cruise control, it's coasting. That is the result of the traction/stability control giving up and turning off both traction control and regeneration.
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