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The quest for wider wheels and tires, 295, 305 and beyond...
- Thread starter Davidss2
- Start date
MasterC17
Active Member
That is not good, likely won't work work with stability control. Overall diameter should be 26"-27" - you're looking at 25.5" which is too small.
silentsnow31802
Member
Wait a sec...
I have some 275/35/18 I got cheap I was going to use for my next commuter tire set. Are you saying the smaller diameter will cause issues with stability control?
How does the car know there is a problem if all 4 tires are the same size?
MasterC17
Active Member
Yes, it will almost certainly cause problems. There are wheel speed sensors that calculate how quickly the tire/wheel is rotating based off the wheel hub. The "safe" range is 26-27". I have seen people get away with 25.8" to 27.2" but that's the maximum.
Has this actually been confirmed? Or just speculation? This exact thing was claimed to be “catastrophic” within the Corvette world but proved to be not really an issue, especially in a Auto-X setting. The exception was when running a wonky staggered setup with major Diameter differences from front to rear.
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Hi, by slotted, did you really cut into the sheet metal? How much negative camber are you running up front now?
I would be happy with -1.0* by loosening and readjusting only.
Curious, what offset is your easy button set to?With that being said, If it truly is an issue then it looks like a 275/35/19 on a 19x9.5 will be the easy button. I’m not looking to put too much effort in to this as this is not my “primary” Autocross vehicle.
I’m going +30mm square 
In Autocross, many are using 285/30-18 (Hoosier or RE71R) which are 24.8”
I have ran 3 events on these and driven over 400 miles. No issues at all. But you want to make sure the front and rear diameter is the same (within 2%) as that is an issue with any awd car.
My car is low using MPP coilovers. And this diameter makes it really low. It will scrape in the middle between the front and rear wheels and i had to remove the mudflaps built into the front of the skirt behind the front wheels.
I have ran 3 events on these and driven over 400 miles. No issues at all. But you want to make sure the front and rear diameter is the same (within 2%) as that is an issue with any awd car.
My car is low using MPP coilovers. And this diameter makes it really low. It will scrape in the middle between the front and rear wheels and i had to remove the mudflaps built into the front of the skirt behind the front wheels.
Clivew
Member
I just want to add, in an ICE car, one of the reasons front and wheel diameters need to be within a certain range is because they are mechanically linked via the transmission components, and a permanent mismatch of speeds can ultimately damage those components (depending on the car and system architecture). In an AWD EV it’s completely different, as front and rear motors are not mechanically linked, and so the rpms are software controlled. All the safety systems are designed around the standard wheel/tyre diameters, which will monitor motor and wheel rpms, and calculate from this. There will be a tolerance of course, but outside of this, the system won’t work correctly.
silentsnow31802
Member
Well due to unforeseen circumstances I had to mount the 275/35R18 tires onto my EC7s today. Found a huge screw sticking out of my sidewall on a spirited drive to the coast.
The tire ship only had PS4s available at around $274 a piece. Hard to pay that when I had a full set in my garage I paid $300 for. I also need my car to commute to work the rest of the week so I cannot wait for tires to be ordered and delivered. So far I have only drove the 15 miles home but so far so good. I will let everyone know if I have any issues running these.
P3D-R
Closed
Hope this helps.
Stock Fenders/Stock P3D rotors
Falken 510 295/30/19
19x10 +25
Camber:
-2.5F
-2.0R
+6.0 caster
Toe
+0.00 front
+0.10 rear
TBH 10.5 +20 in the rear will require a good amount of camber no matter how you cut that pie. If you have factory front camber you're gonna end up around -1 at a lowered height. With that said I'd run the rear at the same or less. When I ran a 9.5 +22 with 265/40/18 NT01's I was super flush in the rear with -0.6 camber because I had stock front camber at -1. I just wanted to have less camber in the rear and always will.
10.5 +20 sticks out another 11mm more than my existing setup which already has camber and 295's which are slightly bulgy on the 10J. I'd say 275/30/19 might work at about -2.5 rear camber. I would say you must get FUCAs though. Just budget for it so your car rotates/shifts weight nicely, and looks proper. I don't think you'll be happy with the aesthetic if your front wheel has a lot less "tilt" than the rear wheel.
I also guess you won't be upgrading to 2 piece rotors in the future because then the whole fitment goes out the window.
In short, get some FUCA's and RUCA's you'll be all set.
When the suspension compresses in the rear it cambers in and is perfectly flush. There are no visible rubs at any point and this car has been pushed.
Stock Fenders/Stock P3D rotors
Falken 510 295/30/19
19x10 +25
Camber:
-2.5F
-2.0R
+6.0 caster
Toe
+0.00 front
+0.10 rear
TBH 10.5 +20 in the rear will require a good amount of camber no matter how you cut that pie. If you have factory front camber you're gonna end up around -1 at a lowered height. With that said I'd run the rear at the same or less. When I ran a 9.5 +22 with 265/40/18 NT01's I was super flush in the rear with -0.6 camber because I had stock front camber at -1. I just wanted to have less camber in the rear and always will.
10.5 +20 sticks out another 11mm more than my existing setup which already has camber and 295's which are slightly bulgy on the 10J. I'd say 275/30/19 might work at about -2.5 rear camber. I would say you must get FUCAs though. Just budget for it so your car rotates/shifts weight nicely, and looks proper. I don't think you'll be happy with the aesthetic if your front wheel has a lot less "tilt" than the rear wheel.
I also guess you won't be upgrading to 2 piece rotors in the future because then the whole fitment goes out the window.
In short, get some FUCA's and RUCA's you'll be all set.
When the suspension compresses in the rear it cambers in and is perfectly flush. There are no visible rubs at any point and this car has been pushed.
TFSMotorsport
Member
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