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ABS/PSM failure - tire size??

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Old 06-21-2018 | 07:58 PM
  #16  
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Originally Posted by Taylorcar
Ok - so I’m not doing any long term damage with the tire sizing?

You might be harming your drivetrain or viscous coupling with those completely incorrect tire diameters. I would replace the rears with some other size around 25.5 inches in diameter immediately.

Last edited by Carlo_Carrera; 06-21-2018 at 08:17 PM.
Old 06-21-2018 | 08:06 PM
  #17  
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Originally Posted by Taylorcar
When I use a tire diameter calculator that shows only a 3.5% difference. Could this be causing my issues?
I think Porsche's specification is a maximum of 3.6 or 3.7% difference. But the stagger has to be in the right direction (smaller diameter in the back).
Old 06-21-2018 | 08:47 PM
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Originally Posted by Carlo_Carrera
You might be harming your drivetrain or viscous coupling with those completely incorrect tire diameters. I would replace the rears with some other size around 25.5 inches in diameter immediately.
So that's the challenge, there really isn't a 25.5" tall 19 available at 295 width or greater.

Of course there's the rubberband thin 315/25/19 @ 25.2" tall, but wants to drive around with almost zero sidewall?
Old 06-21-2018 | 09:11 PM
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Originally Posted by Road King
So that's the challenge, there really isn't a 25.5" tall 19 available at 295 width or greater.

Of course there's the rubberband thin 315/25/19 @ 25.2" tall, but wants to drive around with almost zero sidewall?
Are you running 19" wheels? If so what tire sizes?

I run 19s but with skinny all-season tires for snow/rain.
Old 06-22-2018 | 01:39 AM
  #20  
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Originally Posted by Carlo_Carrera
Are you running 19" wheels? If so what tire sizes?

I run 19s but with skinny all-season tires for snow/rain.
No, I'm running 18" Forgestars. 8.5 and 11" with Yok Advan AD08Rs. I need all the sidewall I can get here in San Francisco, the streets are old and rough.

Interestingly enough, the 225/40/18 Advans were the exact same height and revs per mile as the 295/30s (25.0" & 831 revs) so I went with taller 235/40s up front @ 25.3" tall & 820 revs per mile to preserve the factory ratios...seems to work well paired with the 295/30s.
Old 06-22-2018 | 03:17 AM
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Awesome thanks everyone. That’s what I needed to hear. My fenders are rolled which should give me a bit more flexibility with tire options, but I’ll have to go down in size in the rears for sure. Going to make the change right away to avoid doing any damage. Thanks everyone!
Old 06-22-2018 | 11:19 AM
  #22  
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Originally Posted by Taylorcar
Awesome thanks everyone. That’s what I needed to hear. My fenders are rolled which should give me a bit more flexibility with tire options, but I’ll have to go down in size in the rears for sure. Going to make the change right away to avoid doing any damage. Thanks everyone!
:-)

So after all the discussion, what size rear tires are you going with?
Old 06-22-2018 | 12:31 PM
  #23  
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Can you share PN & instructions? I'm fighting this right now. Speed sensor fault - replaced. It cut down but did not eliminate the PSM/ABS fault. I just replaced my original 2002 MAF but still have about the same error rate.
Don't have the part number for the brake light switch, but you can find it online from Suncoast or another supplier. It was the cause of the ABS/PSM error light in my case. As others have said, many things can cause that particular error, including the brake light switch, a "chafed" ABS harness, out-of-spec. tire sizes, MAF, and battery issues.

Here are a couple of links you may find helpful:
https://rennlist.com/forums/996-turb...el-sensor.html
https://rennlist.com/forums/996-turb...trol-unit.html
Old 08-16-2018 | 02:36 PM
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Last edited by Taylorcar; 08-16-2018 at 02:40 PM. Reason: incorrect
Old 08-19-2018 | 01:49 AM
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235/35 x19 (your current front tire) pairs up identical with 275/30 x19. Not sure how good it would look...but could be your cheapest fix as it would only require a rear tire change to a slimmer one.
Old 08-25-2018 | 09:50 PM
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I am having the same issue. My car had some aftermarket 19s on it for around 10 years. (Previous owner)

This month I switched back to stock 18s with stock tire sizes.

The only thing I can notice is that the PSM switch on the dash seems to have been disabled. The ABS/PSM light comes on after about 5-10 minutes of driving.



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