wukindada Posted June 17, 2005 Share Posted June 17, 2005 Since switching to 18's will I be able to use the spare (in an emergency) or will it cause a driveline failure (AWD) Toyota 6EATS .........SUCK!!!!!! Link to comment Share on other sites More sharing options...
rao Posted June 17, 2005 Share Posted June 17, 2005 No, your car will explode So long as you have maintained the overall diameter of the wheels (within 2% is the spec IIRC, and which you should), it will work just fine. Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
wukindada Posted June 17, 2005 Author Share Posted June 17, 2005 I did not think it would be anything dramatic;) My toy is a toyota landcruiser FJ80 TRD and I know that is an issue with their AWD setup. Dramatic driveline wear:( I installed a set of 19" wheels & had to use the stock 16" spare one time less than 30 miles.....big $$$$$$$ Toyota 6EATS .........SUCK!!!!!! Link to comment Share on other sites More sharing options...
IwannaSportSedan Posted June 17, 2005 Share Posted June 17, 2005 Its all about circumference. If the spare is within 2% of the circumference of whatever road tires you are using, it should be fine. If not, then it is either time for run-flats, or a can of tire inflator/repair goo. Or a full-size spare. Link to comment Share on other sites More sharing options...
rc0032 Posted June 17, 2005 Share Posted June 17, 2005 So if I run a 225/45/17 summer tire and have a full size spare (215/45/17) and I keep it below 60 i'm kewl? Link to comment Share on other sites More sharing options...
eb50 Posted June 17, 2005 Share Posted June 17, 2005 a spare LGT? I could just use first one... Link to comment Share on other sites More sharing options...
IwannaSportSedan Posted June 17, 2005 Share Posted June 17, 2005 225mm x .45 (aspect ratio) = 101.25mm sidewall. 215mm x .45 (aspect ratio) = 96.75mm sidewall a 17" rim is nominally 431.8mm So, summer tires have a nominal diameter of 431.8 + 101.25 = 533.05 And the full size spare has a nominal diameter of 431.8 + 96.75 = 528.55 Multiplying each by Pi, we get: 1674.63, and 1660.49, which is the circumference in millimeters of each, respectively. Divide one by the other, and you get that the spare tire is .84% smaller that the road tires. That is nearly nine-tenths of one percent. Well within the 2% differential guideline. (if the manufacturing of the wheels and tires is exact, which it never is, especially for tires. Not to mention inflation pressure.) Should be fine. BTW, as extra credit for showing my work, can I have your spare LGT? j/k Link to comment Share on other sites More sharing options...
emosound Posted June 17, 2005 Share Posted June 17, 2005 Sidewall needs to be added twice to get the total diameter. 431.8+101.25+101.25=634.3mm 431.8+96.75+96.75=625.3 So, the 215 is 98.58% as tall as the 225. In reality, look up the actual dimensions from the tire manufacturer. -Paul 225mm x .45 (aspect ratio) = 101.25mm sidewall. 215mm x .45 (aspect ratio) = 96.75mm sidewall a 17" rim is nominally 431.8mm So, summer tires have a nominal diameter of 431.8 + 101.25 = 533.05 And the full size spare has a nominal diameter of 431.8 + 96.75 = 528.55 Multiplying each by Pi, we get: 1674.63, and 1660.49, which is the circumference in millimeters of each, respectively. Divide one by the other, and you get that the spare tire is .84% smaller that the road tires. That is nearly nine-tenths of one percent. Well within the 2% differential guideline. (if the manufacturing of the wheels and tires is exact, which it never is, especially for tires. Not to mention inflation pressure.) Should be fine. BTW, as extra credit for showing my work, can I have your spare LGT? j/k Link to comment Share on other sites More sharing options...
IwannaSportSedan Posted June 17, 2005 Share Posted June 17, 2005 DOH! I have wondered about the sidewall bit before, whether or not the aspect ratio is the combined sidewall heigth above and below, or whether the bead of the dire is included in the sidewall height, or not. I guess it is just one sidewall height, (not both above and below) and probably from bead to tread. I guess I just went on the assumption that the sidewall height from rim to tread doesn't really look like it would be 45% of the tire's tread width. It looks nowhere near half as tall from the rim as it is wide. I would guess closer to 22.5% of the width... But that is what I get for judging by appearance. Wrong. Link to comment Share on other sites More sharing options...
zmarko Posted June 18, 2005 Share Posted June 18, 2005 Just use this and keep the total circumference as close as possible to the stock setup. http://www.miata.net/garage/tirecalc.html Link to comment Share on other sites More sharing options...
wukindada Posted June 18, 2005 Author Share Posted June 18, 2005 Thanks Guys;) Toyota 6EATS .........SUCK!!!!!! Link to comment Share on other sites More sharing options...
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