Crown

Board: Porsche - 911 - 996 - Turbo Language: English Region: Worldwide Share/Save/Bookmark Close

Forum - Thread

    Feb 4, 2004 6:18:17 AM

    Joe Weinstein
    Junior
    Joe Weinstein
    Loc:
    Posts: 56, Gallery
    Registered on: Aug 1, 2002

    How much can the front and rear tire diameters differ?

    Hi folks. Is there any Porsche info on how closely the front and
    rear tire diameters have to match in order to prevent damage to
    the viscous torque transfer unit? It seems that the published specs
    of the officially approved tires are not exactly the same. I want this
    info for considering what range to stay within if I were to run
    other tires and sizes if I were to change wheels etc.
    thanks,
    Joe

    Feb 4, 2004 9:15:17 PM

    RCA
    Rennteam Administrator
    RC
    Loc: Rennteam HQ , Germany
    Posts: 59605, Gallery
    Registered on: Mar 26, 2002
    Reply to: Joe Weinstein

    Re: How much can the front and rear tire diameters differ?

    Quote:
    Joe Weinstein said:
    Hi folks. Is there any Porsche info on how closely the front and
    rear tire diameters have to match in order to prevent damage to
    the viscous torque transfer unit? It seems that the published specs
    of the officially approved tires are not exactly the same. I want this
    info for considering what range to stay within if I were to run
    other tires and sizes if I were to change wheels etc.
    thanks,
    Joe



    To my knowledge, more than 5% are "deadly" for the viscous coupling and less than 3% are recommended. But don't nail me on this one.

    Feb 5, 2004 12:16:04 AM

    Joe Weinstein
    Junior
    Joe Weinstein
    Loc:
    Posts: 56, Gallery
    Registered on: Aug 1, 2002
    Reply to: RCA

    Re: How much can the front and rear tire diameters differ?

    Thanks for the rough guidelines, and you'll be hearing from
    my lawyer...

    Feb 7, 2004 10:30:50 PM

    fritz
    Rennteam VIP
    fritz
    Loc: BaWü , Germany
    Posts: 10248, Gallery
    Registered on: Jul 23, 2003
    Reply to: Joe Weinstein

    Re: How much can the front and rear tire diameters differ?

    Quote:
    Joe Weinstein said:
    Hi folks. Is there any Porsche info on how closely the front and
    rear tire diameters have to match in order to prevent damage to
    the viscous torque transfer unit?



    I doubt you'll find any Porsche info on thís, because their line would have to be that, if you stick with their officially approved tire combinations, you' ll have no problems with viscous coupling life!

    Just considering the VC, the right answer to your question would probably be "How short a VC life are you prepared to accept?"

    But.........., as so often in real life, there is a big BUT!

    The big BUT is that changing relative rolling radii of front and rear tires also changes relative inputs to ABS control unit, which will then influence ABS characteristics.

    Cannot give you the gospel on what will happen first, whether you will get an error report in your display, or whether ABS will become over-sensitive and cut in much too soon, or become less sensitive and not cut in when you really want it.
    But the set-up will not be what the development engineers intended you to have. And that would not necessarily be a good thing.

    fritz

    Feb 15, 2004 7:00:56 AM

    Joe Weinstein
    Junior
    Joe Weinstein
    Loc:
    Posts: 56, Gallery
    Registered on: Aug 1, 2002
    Reply to: fritz

    Re: How much can the front and rear tire diameters differ?

    I forgot to thank you Fritz... That makes perfect sense.
    What about the GT2s? I've seen lots of those running differnt
    diameter fronts and rears, and they have ABS too, right?
    Are the stock front and rear GT2 tires the same diameter?

    Feb 16, 2004 9:06:16 PM

    fritz
    Rennteam VIP
    fritz
    Loc: BaWü , Germany
    Posts: 10248, Gallery
    Registered on: Jul 23, 2003
    Reply to: Joe Weinstein

    Re: How much can the front and rear tire diameters differ?

    Hello Joe,

    The effective front/rear tire radii on the GT2 díffer more than those on the Turbo, but the GT2 has its own ABS software, which already compensates for this.

    So it's not a problem.

    fritz
     
    Edit

    Forum

    1. All 

    Boards

     
    Board Subject Last post Rating Views Replies
    Porsche Sticky SUN'S LAST RUN TO WILSON, WY - 991 C2S CAB LIFE, END OF AN ERA (Part II) 5/15/24 8:44 AM
    art.italy     		803980 1808
    Porsche Sticky Welcome to Rennteam: Cars and Coffee... (photos) 4/7/24 11:48 AM
    Boxster Coupe GTS     		448724 565
    Porsche Sticky OFFICIAL: Porsche 911 (992) GT3 RS - 2022 3/12/24 8:28 AM
    DJM48     		266333 323
    Porsche Sticky The new Macan: the first all-electric SUV from Porsche 1/30/24 9:18 AM
    RCA     		90161 45
    Porsche Sticky OFFICIAL: Taycan 2024 Facelift 3/15/24 1:23 PM
    CGX car nut     		6747 50
    Porsche The moment I've been waiting for... 2/1/24 7:01 PM
    Pilot
     
     
     
     
     
    		 886067 1364
    Porsche 992 GT3 7/23/23 7:01 PM
    Grant     		834304 3868
    Porsche GT4RS 4/21/24 11:50 AM
    mcdelaug     		400019 1454
    Porsche Welcome to the new Taycan Forum! 2/10/24 4:43 PM
    nberry     		396116 1526
    Others Tesla 2 the new thread 12/13/23 2:48 PM
    CGX car nut     		383339 2401
    Porsche Donor vehicle for Singer Vehicle Design 7/3/23 12:30 PM
    Porker     		371032 797
    Porsche Red Nipples 991.2 GT3 Touring on tour 5/12/24 6:23 PM
    blueflame     		293651 669
    Porsche Collected my 997 GTS today 10/19/23 7:06 PM
    CGX car nut
     
     
     
     
     
    		 265996 812
    Lambo Huracán EVO STO 7/30/23 6:59 PM
    mcdelaug     		244103 346
    Lotus Lotus Emira 6/25/23 2:53 PM
    Enmanuel     		238673 101
    Others Corvette C8 10/16/23 3:24 PM
    Enmanuel     		222407 488
    Others Gordon Murray - T.50 11/22/23 10:27 AM
    mcdelaug     		173207 387
    Porsche Back to basics - 996 GT3 RS 6/11/23 5:13 PM
    CGX car nut     		144996 144
    BMW M 2024 BMW M3 CS Official Now 12/29/23 9:04 AM
    RCA     		121182 303
    Motor Sp. 2023 Formula One 12/19/23 5:38 AM
    WhoopsyM     		111944 685
    Porsche 2022 992 Safari Model 3/7/24 4:22 PM
    WhoopsyM     		85733 239
    AMG Mercedes-Benz W124 500E aka Porsche typ 2758 2/23/24 10:03 PM
    blueflame     		75933 297
    Porsche 992 GT3 RS 3/3/24 7:22 PM
    WhoopsyM     		54979 314
    Motor Sp. Porsche 963 5/14/24 7:53 AM
    Porker     		26601 247
    Ferrari Ferrari 296 GTB (830PS, Hybrid V6) 1/21/24 4:29 PM
    GT-Boy     		21792 103
    BMW M 2022 BMW M5 CS 4/8/24 1:43 PM
    Ferdie     		20313 140
    AMG G63 sold out 9/15/23 7:38 PM
    Nico997     		17146 120
    AMG [2022] Mercedes-AMG SL 4/23/24 1:24 PM
    RCA     		14534 225
    Motor Sp. 24-Hour race Nürburgring 2018 5/25/23 10:42 PM
    Grant     		11582 55
    Porsche Porsche Mission X Hypercar 12/3/23 8:52 AM
    996FourEss     		11206 63
    123 items found, displaying 1 to 30.