MRnMRS Posted September 30, 2009 Share Posted September 30, 2009 So this morning I noticed that my right rear passenger tire was really low on air so I drove about 1/4 mile down to the nearest gas station to fill up on air. When I heard a loud hissing sound I knew I had a nail or screw puncture. Sadness. I take the car down to what I was told is a reputable tire shop (Les Schwab) and he told and showed me the 6" nail that poked through the tread and gouged out some bits from the sidewall. More sadness. The tiredude then tells me since I have an AWD car that I would have to replace all 4 tires. Wow are you kidding me? The other 3 tires on the car are fine with less than 12k miles on them. So my question is, would I be ok with just replacing 2 tires or would all 4 be necessary? Cuz personally I think that's some BS. Or I could be wrong and owe the tirejockey a virtual apology. Your pals, MrnMrs Link to comment Share on other sites More sharing options...
lookslikeanevo Posted September 30, 2009 Share Posted September 30, 2009 tread has to be withint a certian range to not cause damage...a few solutions to this... buy 4 tires shave new tire down to same tread as other 3 Current:MY05 SWP wagon - 253/290 UP, AEM CAI, Invidia Q300, tuned@yimisport OLD: MY06 GRP - 274/314 Link to comment Share on other sites More sharing options...
mightyS Posted September 30, 2009 Share Posted September 30, 2009 Tirerack will shave a new tire and send it to you. You don't need to buy 4 new tires unless they are old or very worn. Link to comment Share on other sites More sharing options...
MRnMRS Posted September 30, 2009 Author Share Posted September 30, 2009 Tirerack will shave a new tire and send it to you. You don't need to buy 4 new tires unless they are old or very worn. so shaving a tire is pretty safe? I found some threads on here that don't recommend shaving. the car is an '09 outback (purchased dec '08) with ~12,000miles. just curious, why isn't replacing just 2 tires an option? i'm new to awd. Link to comment Share on other sites More sharing options...
krzyss Posted September 30, 2009 Share Posted September 30, 2009 RTFM You should find a statement that tires' circumference must be within 1/4 inch (or is it 1/2). If new tire has more than this you may fry your AWD system. Options: - Manual magic value has probably some safety margin built in and you may be willing to push it; it may be safer to push it on axle with open differential (if you have LSD). - Shave new tire so its circumference is within SOA spec - Buy 4 new tires Krzys Link to comment Share on other sites More sharing options...
Trax Posted September 30, 2009 Share Posted September 30, 2009 Shaving a tire is safe. I had to do it on a full set back when no one knew who Yokohama was - their tires weren't as round then as they are now! Link to comment Share on other sites More sharing options...
wpmarky Posted September 30, 2009 Share Posted September 30, 2009 Your tires need to be within .25" circumference of each other to prevent your diff from frying. If you only replace 2 tires, the new ones will have less RPM's than your older tires since the circumference is bigger. Your open differential will sense that, and will try send power to the tires it thinks are slipping (rotating faster). Since your new tires will always be bigger, your diff will always be 'working', and may lead to overheating and frying your diff. Link to comment Share on other sites More sharing options...
MRnMRS Posted September 30, 2009 Author Share Posted September 30, 2009 Your tires need to be within .25" circumference of each other to prevent your diff from frying. If you only replace 2 tires, the new ones will have less RPM's than your older tires since the circumference is bigger. Your open differential will sense that, and will try send power to the tires it thinks are slipping (rotating faster). Since your new tires will always be bigger, your diff will always be 'working', and may lead to overheating and frying your diff. thanks for your explanation. thanks to the others too that replied. i also got a hold of my service tech at the and got pretty much the same technical explanation. he recommended that i go to a different shop that they send their cars to and they will measure tread depth on my other 3 tires and make their recommendation based on that. where as les schwab just told me i'd need to replace all 4 with either their house brand tire or some $1000 toyo tourevo's. Link to comment Share on other sites More sharing options...
krzyss Posted October 1, 2009 Share Posted October 1, 2009 Do not use tread depth measure. Use tape to measure total circumference. Small error in depth translates to big error in circumference. Krzys Link to comment Share on other sites More sharing options...
MRnMRS Posted October 1, 2009 Author Share Posted October 1, 2009 well.. i dunno what went wrong.. but my wife & i went in to get the Nokian WRG2s got the Nokian WRG2s then we said to each other "hey let's check out the new OB 2010s at the dealership down the street.." got the new OB 2010 what a crazy day. Link to comment Share on other sites More sharing options...
wpmarky Posted October 1, 2009 Share Posted October 1, 2009 wow congrats, i like the new outbacks too. Link to comment Share on other sites More sharing options...
NSFW Posted October 5, 2009 Share Posted October 5, 2009 got the new OB 2010 Oh yeah, that's another option when you lose a tire. With all the options people listed above, I'm surprised nobody mentioned that one. Link to comment Share on other sites More sharing options...
wpmarky Posted October 5, 2009 Share Posted October 5, 2009 that happened to my friend. He lost his cup holder liners for his nissan xterra, so one day he goes to the dealership to get new cupholders, and walk out with a new 350z... Link to comment Share on other sites More sharing options...
YCAGEL TG Posted October 6, 2009 Share Posted October 6, 2009 I broke the shifter cable on my 91 Golf, so I bought a 04 WRX Link to comment Share on other sites More sharing options...
subie_dude05 Posted October 6, 2009 Share Posted October 6, 2009 http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18 some more info on why we can't get just one new tire. hope it helps Link to comment Share on other sites More sharing options...
FireB Posted October 6, 2009 Share Posted October 6, 2009 Would it be safe to say as long as the diameter is the same, you can mix the tires like Bridgestone Blizzak LM-22 and Bridgestone Blizzak LM-60 Same Size and everything but shaved to the same diameter. I have a situation where one of the LM-22 Blew and they are discontinued. So it would be like 2 LM-60 Shaved in the Fronts and 2 LM-22 Old in the Back. Or should I stop being cheap? Link to comment Share on other sites More sharing options...
muddy02 Posted October 6, 2009 Share Posted October 6, 2009 i would like to understand a technical explaination for "frying the differential" and "100% of the time". Seems to me, Subaru would then be on the hook for supplying a full size spare tire, which they don't (i don't think). It's not about speed, it's about acceleration! Link to comment Share on other sites More sharing options...
MRnMRS Posted October 7, 2009 Author Share Posted October 7, 2009 Would it be safe to say as long as the diameter is the same, you can mix the tires like Bridgestone Blizzak LM-22 and Bridgestone Blizzak LM-60 Same Size and everything but shaved to the same diameter. I have a situation where one of the LM-22 Blew and they are discontinued. So it would be like 2 LM-60 Shaved in the Fronts and 2 LM-22 Old in the Back. Or should I stop being cheap? The tech at my local dealership was adamant about all 4 tires being the same brand/model/size due to tread compound, tread wear rating, etc. For some reason I felt that the explanation coming from him was better than an explanation from the tireshop guy who's really just interested in selling me 4 new tires. I'm not sure what I'd do in your case, which I'll definitely have to keep in the back of my mind now knowing that tire models do get discountinued every few years. :spin: Link to comment Share on other sites More sharing options...
MRnMRS Posted October 7, 2009 Author Share Posted October 7, 2009 i would like to understand a technical explaination for "frying the differential" and "100% of the time". Seems to me, Subaru would then be on the hook for supplying a full size spare tire, which they don't (i don't think). here's a quick & dirty recap of what the Subaru tech told me.. due to wheel tire circumference tolerances, if there is a difference greater than 20% tread wear between the old tires and new tires... our car's computer would detect the difference in wheel spin on the older wheels/tires (since they would turn over quicker than a new wheel/tire) and apply more power to the new wheel/tire because the computer would think that it is "slipping" when in really isn't or something to that effect. if someone can clean up the mess of an explanation i gave please feel free to do so. mind you that we just got the new '10 ob ltd so i may not be thinking so clearly! http://i215.photobucket.com/albums/cc147/ceejaybeegee/2010_OutbackLTD.jpg rolling up Mt. Rainier & playing with the 6-speed CVT!!! who knew paddle-shifting could be so fun... Link to comment Share on other sites More sharing options...
Cannonball Posted October 10, 2009 Share Posted October 10, 2009 It has to be related to long term use. Taking turns one after the other would cause the same effect to the nth degree IMO. So how does that pertain to people who live in the mountains and drive on twisty roads all the time? BTW the tech guy would be talking about the VDC system and not the AWD system. Can't speak for the AT, but the MT is all mechanical. Link to comment Share on other sites More sharing options...
OGG Posted October 10, 2009 Share Posted October 10, 2009 It has to be related to long term use. Taking turns one after the other would cause the same effect to the nth degree IMO. So how does that pertain to people who live in the mountains and drive on twisty roads all the time? BTW the tech guy would be talking about the VDC system and not the AWD system. Can't speak for the AT, but the MT is all mechanical. Her could be referring to the VDC or the AWD. The AWD in the automatics is computer controlled and you will wear out the transfer clutches with mismatched tires. In a manual it would cause extra wear on the center diff because it would effectively be constantly slipping. Link to comment Share on other sites More sharing options...
blackfang Posted October 10, 2009 Share Posted October 10, 2009 Ok. What happens mainly for the EAT cars is when you have tires that are more than a 1/4 inch difference in circumference this throws it for a loop. Say you put on less than 4 tires. The AWD will detect specific and excessive tire spin verse the others. The AWD will transfer the power from the spinning or in this case rotating faster tire to the tires rotating at a slower speed via the transfer solenoid and it pumping fluid. The problem is this burns out the transfer clutches. Manual cars are similar, but they have a center differential with a viscous coupling that handles the transfer of torque with the inner and outer plates and an air/silicone oil mixture. When the same occurs that would be slipping more and putting stress on it. Manuals tend to be less sensitive of the issue verse an EAT vehicle, but the same damage can occur. There is a post on this that is not stickied in the section. [SIZE=1][URL="http://public.fotki.com/blackfang/"]Pics[/URL] [B]08 KawasakiZZR 600- exhaust and other mods 98 Camaro Z/28 HT- some mods......street/strip car 07 Legacy 2.5i- SPT exhaust...daily driver[/B][/SIZE] Link to comment Share on other sites More sharing options...
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