Gt3stig

I burned through a set a of rear tires, I replaced them with the same size Michelin Pilot Sports 295/30ZR18.
I did not replace the fronts because they hardly have any wear on them and are only three years old.


Rears 295/30ZR 18
Fronts 225/40ZR18

After I had the rears replaced I was driving the car and went into a left turn and the brakes came on briefly. This only happened twice in one month. I researched why this happened and learned that the front tires are supposed to taller than the rear tires. So I measured their heigth.

The rears are 25 inches tall and the fromts are 24 1/2 inches tall.

Does a 1/2 inch make a difference? Can I ruin the front drive?

Thanks.

infinkc

You may need to wear the coating off the new tires a bit more. I had a similar situation.

Macster

The front tires are 25.1" tall. Not 24.5" tall.

The tire sizes are ok at least the revs/mile of the rears (832) is a bit more than the revs/mile of the fronts (828). Thus there is torque being transferred from the rear to the front and this is the way it should be.

I'm with infinkc. Most likely the problem is the new tires need some use to eliminate the mold release stuff and get the rear tires to their normal level of grip.

Just try to remember to avoid pushing the car very hard for a few hundred miles which should be plenty of time for the tires to normalize.

Wouldn't hurt you to double check tire inflation pressures just to be sure the tires (front and rear) are inflated properly. The tire pressures on the inside of the gas tank filler lid are for a fully loaded car. For a lightly loaded car the inflation pressures can be reduced by 2psi though some reduce the pressures even more. You can experiment but don't go overboard. Be sure you have a good tire pressure gage.

Unlikely to be a problem but while you are there might as well be sure the new rear tires are the correct tires (same brand, model, etc. as the front tires) and if unidirectional mounted in the right direction.

What wear pattern did the old tires have? If uneven across the tread face this can be a sign alignment is incorrect.

Gt3stig

Tire pressure sticker states 36 and 44 rear.
i have 34 and 42.

i just re measured the front tires and they are 24 1/2 inches tall.

Rear tires wore out evenly.....I'm an aggressive driver with psm off.

Third-Reef

Sounds like the front and read tire brand and or model are different? If so that is something that can cause some squirrley traits. I had 295 35 18 and 235 45 18 on my car and it provided a small stagger in the wrong direction. i had some PSM interventions occasionally with that setup. Now with a new set of PS2 295 30 18 and 235 40 18 on, i have not had a PSM intervention in 5K miles and my rears still look great.

Gt3stig

Michelin Pilot Sports front and rear.
stock size tires on stock wheels.

Third-Reef

Good for you keeping it consistent. Go do a couple tire smoking doughnuts and you should be fine.

fpb111

https://www.tirerack.com/tires/tires...t&autoModClar=


Michelin Pilot Sport
Pilot Sport PS2
Max Performance Summer

225/40ZR18(92Y) XL N3(Porsche) Front 220 AA A 1,389 lbs. 50 psi 9.5/32" 21 lbs. 7.5-9" 8" 9.1" 7.8" 25.1" 829

295/30ZR18(98Y) XL N3(Porsche) Rear 220 AA A 1,653 lbs. 50 psi 9.5/32" 27 lbs. 10-11" 10.5" 11.9" NA 25" 832

What do your rears measure?

Kevinmacd

Heres my thought the rears being new with new tread made it a mismatch, they are at their max diameter causing your PSM To kick in! You have more wear on the fronts than you realize. Even though you are running the correct sizes, if not the same brand you can create more of a mismatch, since different manufacturers even though have the right size stated, their diamters could vary between them. If all 4 were new of the same brand the PSM would not kick in. Even if the fronts were the same brand and already had mileage on them, it would still work.
i get 2x the life on the fronts than the rear, but always replace either with same brand. Never have the PSM kick in.

Gt3stig

25 inches tall

Gt3stig

Thanks Kevin
I'll get new tires for the front Monday.

imlumpy

Imagine that , a 996tt that kills rear tires, lol.

Thomas42

Who knew?

Kevinmacd

Get back and let us know how it goes!