AWD cars and tires size importance?
04-12-2010, 03:51 PM
#17
Nordschleife Master
Thread Starter
04-12-2010, 08:49 PM
#18
Drifting
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.
04-12-2010, 09:29 PM
#19
Race Car
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.
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.
04-12-2010, 10:50 PM
#21
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
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
04-13-2010, 08:42 AM
#23
Nordschleife Master
Thread Starter
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
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
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.
04-16-2010, 07:49 AM
#24
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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!!
04-16-2010, 10:51 AM
#28
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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.
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.
04-16-2010, 10:54 AM
#29
Nordschleife Master
Thread Starter
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.
The T1R only comes in a 295/35/18 for the rear. They don't have a 315/30.
