29 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHAWD cars and tires size importance?
Leading reported evidence
Use manufacturer specs instead and did my own computation
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
It just doesn't know the exact specs of different tires which is why I used the manufacturer specs instead and did my own computation.
Leading evidence: 'Use manufacturer specs instead and did my own computation' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check revs per mile of the tire' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
The variance is 3%, I always check the Revs Per Mile of the tire to determine this.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
Now that is a high performance tyre but not N rated and skill demanding in the rain so I would probably still recommend PS2 with 315 at the back which will give you all the grip you could dream of.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
And I would run the 225 if I went with the MPS2 or MPSC.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
With a 295/30/18 you should really be running 225/40/18 at the front.
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
Now that is a high performance tyre but not N rated and skill demanding in the rain so I would probably still recommend PS2 with 315 at the back which will give you all the grip you could dream of.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
29 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T181445Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Since I'm new to the world of AWD with the recent purchase of the Turbo, I am trying to find in the manual, etc, (with no luck) what the requirement are for tire size tolerances.
For example, is the importance of front to back variance more important than staying within a specific window of sizing (diameter) on the single axle?
What happens to the AWD system if the tire is too big or small?
I just can't find any PCNA/PAG documentation on tire size variance tolerances.
My car is delivered from the factory with the following diameters:
F: 25.1"
R: 25.0"
My car as delivered from the dealer a few weeks ago with new rubber from the PO:
F: 25.3"
R: 26.0"
I don't feel anything adverse but you never know.
according to the dude in the pca website (I forgot his name, Joe something)..... no more than 4% diff f/r for the abs to start acting funny. Thats all i got...
Its a mechanical AWD system via viscous coupling.... as long as the diff has good fluids you should be fine., very few has reported failure and the 4% rule appies to the awd setup as well.
I have heard the 600hp+ TT has burned their coupling.... having abs issues. I think the abs is more of an issue than the front diff is concerned.....
So when are you gonna convert to rear drive setup.
Dell
The variance is 3%, I always check the Revs Per Mile of the tire to determine this. The front differential is the one to suffer the most and gets damaged easily if the radial speeds of the front and rear tires are unequal or way out of spec.
Dell, use this tire calculator to see if the rolling diameter difference between the front and rear is greater than 3%.
http://www.1010tires.com/tiresizecalculator.asp
its not so much of the difference between the stock rear tire vs the new rear tire, but the error between the front and rear tire..... optimally you want as close to 25" since thats what the designers had intended for the 996. But the error of diameter between the front and rear is also very important.
plug you tire front and rear specs in this calculator.... on the bottom it will tell you the % error.
http://www.miata.net/garage/tirecalc.html
edit: 2.9% difference, between the front and rear.
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
235/40-18 3.7in 12.7in 25.4in 79.8in 794 0.0%
295/35-18 4.1in 13.1in 26.1in 82.1in 772 2.9%
That's a really good "generic" calculator. It just doesn't know the exact specs of different tires which is why I used the manufacturer specs instead and did my own computation.
I'm still looking for PCNA/PAG documentation regarding this.
Dell - On my 2000 C4 the stock tires were 225/40-18 and 265/35-18. For the past 3+ years I have been running a set of PS2's 235/40-18 and 265/40-18 and have not had any problems. Tirerack has good info on the diameter of different tire makes and sizes. I did the calculations when I first got the PS2's and I think they were slightly more than the 4% delta. The critical (not sure how critical) delta is the difference between the fronts and the rears.
Dell
Ok, I may not know **** but here is my experience (not opinion)
On my C4S (996). I had 315-25-19 and 245-35-19. According to the calculators they are pretty different: RPM: 825.3 and 807.7. You math nuts can figure the %. I had no issues in a year and a half. Yet I did all the right fluids etc.
I had my 97 993TT with the STOCK tire size and the front diff blew up within 100 miles due to ****ty diff fluid (IMHO). It has 88k on it. I know, different systems.
The 235-35-19 has an RPM of 816.6. I just ordered tires for my new C4S and went that route. Was it the smell of burning diff fluid from the 993 that pushed me to the better RPM? Who knows what the toxic stuff did to my brain by hey. This was my experience.
My $0.02
From the perspective of the viscous coupling AWD system I don't think such small % differences from stock are going to create problems. When I had my C4 cab I ran 235/40R18 and 285/30R18 Yokohamas (OEM is 225/40R18 fronts) without problems.
The Porsche viscous coupling is geared to always operate with a slight difference between front and rear shaft so no less than 5% torque is sent to the front axle. This is to reduce the time delay for torque to be sent to the front wheels when the rears wheels slip. So I would say any minor differences due to tire size is not going to matter much.
I can't imagine that Porsche engineers would design a system that would be that intolerant given variations between tire manufacturers and reduction in diameter from normal wear.
BTW, nice ride dood
Thanks! Loving every minute in it
This is what I am hoping. Of course, the next set of tires will be more "in spec" but these tires are BRAND NEW so I'd hate to toss them.
I would recommend 235/40/18 front and 315/30/18 back both available in N rated rubber and the difference is less than 0.2%. Your current rears will probably give before the fronts so when you swap out go 315/30/18 at the back. Gives you a reason to use the rear rubber you have currently!!
With a 295/30/18 you should really be running 225/40/18 at the front.
If you like Toyo you cant get a 315/30/18 T1-R but you can get a R888 in that size. Now that is a high performance tyre but not N rated and skill demanding in the rain so I would probably still recommend PS2 with 315 at the back which will give you all the grip you could dream of.
And I would run the 225 if I went with the MPS2 or MPSC. If I ran the Nitto I would do the 245/315 combo.
The T1R only comes in a 295/35/18 for the rear. They don't have a 315/30.
This is a source reference. Confirm exact model applicability in the original material.
