mikerosi

Well....I had hankooks and sumitomas activate the PSM badly when I changed the rears only. They are both NOT an N rated tire so maybe that is the reason. When I changed the rears only with my Michelins....NO Problem with the PSM kicking in. My solution to the non N rated tires was to change all 4 at the same time, even though the fronts looked like they had 50-60 percent left. Bear in mind if you drive like a granny you will not notice but like OP said, he was at the track. I drive my car hard on the street and my PSM did not like the tire difference, Mike

"02996ttx50

the ecu doesn't know whether the tires are n rated or not. it's the differences in tread depth front to rear. pure n simple.

mikerosi

Hey man, you`re not listening, I said I never had this problem with N rated tires!The ECU does know if its an N rated tire because the circumferences are more closely in spec

"02996ttx50

now you're not making sense. that's not at ALL why the ecu wouldn't know
if it was a n rated tire! the ecu would only respond to a difference in tread depth, front to rear thereby triggering psm/abs lol. i responded to what you posted upthread:


to which i replied that the ecu doesn't know whether or not the tire(s) were/are n rated or not lol.

you'll figure it out. no big deal. cheers.

Carlo_Carrera

Was this the first track event you have done with the new rears? If yes, the new rears just might need to be heat cycled to stop the PSM kicking in.

mikerosi

OK professor, the ecu knows its an N rated tire because it is NOT the oversized diameter or circumferance of the Hankooks or the Sumitomas. And of course We know the ecu does not physically SEE the N rating on the tire (DUH)!!! But because the Sumitoma front tires are worn down to 50-60% and then you add the oversized new rears then that combination causes the PSM to kick in. Now I know you read my post where I said my Michelins did not do this in this exact scenario. The reason is my Michelins (a N rated tire) has a smaller diameter than the Sumitomas and the formula works for the PSM. with the fronts worn down to 50-60% The PSM is happy and I can drive the crap out of the car without the PSM engaging unless I` heading for a cliff! LOL Now dammit I know you understand but you insist on playing Dumb and dumber!!!! Mike

"02996ttx50

mike. if the ecu doesn't recognize any discernably inconsistent ratio between tires, then the abs/psm will not be triggered. it has nothing whatsoever to do with brands, n ratings, or anything other than relaltive tread depth(s) ( and possibly ) tread pattern(s) front to rear. this of course also explains the phenomenon of abs/psm cels occurring upon placement of new rubber against old, and then the cels no longer happen and settle down after some scrubbing. provided of course that the tire combo's on the given car are within some reasonable measure of "recommended" spec...

..and i've been called many things in life, but never "professor" ( to the best of my knowledge? lol ) but i'll take it. thanks.

rmc1148

Forget it Mike and go on and enjoy your day lol.

Kevinmacd

mikeros1 -The PSM only engages based on rotational speed. Now if you were to put new N spec tires on the rear, with the fronts n spec having only 10% life, the chance of the PSM kicking in is pretty good. The problem here is even though he has Hankooks, the new tires in themselves have a lot of tread, yet the fronts are worn. The ecu sees the different rotation speeds, hence the ecu kicking in PSM. The problem is the rears when new 295-30-18 have a diameter of 26, the fronts when new have a diameter of 25.1. When run as a new set, there is not enough difference for the ecu to kick in, now take 40% or 50% away from the fronts now you have a much larger differential, and this in itself shows enough in rotational speeds to engage PSM. You will probably see this more while cornering. You are correct that Ps2 tires are much closer in diameter hence the reason some are able to get 2 rear changes to one front with no PSM interaction. In this case the rears will need to be run in before the differences are no longer a factor.

"02996ttx50

that's a better way to put it kevinmacd. well said.

mikerosi

Guys......thats what I am saying.. If you use Sumitoma or Hankooks you have to change all 4 tires at once, Ask me how I know??? Now with the Michelins I never had to do that and could always get a 2 for 1 swap on the tire changes ( about 6 sets) So its just a coincidence that the Miches are N rated and the Sumis are not. I think Porsche knows you do not have to change all 4 tires on a N rated tire at 10 K miles. and not have to worry about PSM issues

"02996ttx50

i think we all agree to agree i think

rmc1148

Touch down!

mikerosi

you guys are giving me a headache

rmc1148

Mike I fully understand what you were saying and your on top of it so take a couple aspirin and write me in the morning lol.