Fatter tires on stock 18in rims, yes 255/55/18 !
07-13-07, 11:32 AM
#76
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I use to eat and breathe this tire stuff when I use to work in marketing for Yokohama tires. You all make some good points, but I thought I would give you guys some rule of thumbs to ensure you maintain a smooth and quite ride on your RX.
(1) When changing tire or wheel size try and keep the overall diameter "OD" the same as the stock tire size OD. Here is how to calculate your OD:[URL="http://www.pepboys.com/learning_center/car_care/articles/tire_diameter.html"]. This will prevent you from throwing your speedometer off and yes bigger tires and wheels do typically; eat more gas and lengthen braking distance. Try and avoid using wheel spacers this just ands more weight and it was not accounted for during Lexus R&D testing.
(2) Inflate your tires per Lexus specifications. Your PSI will have the biggest impact on ride comfort next to reducing sidewall height. The recommended PSI is usually located in the driver side door jam. You will be surprised how many people just read the max PSI number on the sidewall and inflate to that level or just put 35PSI as a default. This is very important not only for safety reasons but also to maintain consistent handling characteristics. When your tires are cold, fill your air pressure 1-2 PSI below the recommendation, this is because when the tire gets warm it will raise the PSI level 1-2 PSI and get you to your recommended spec. If you plan on taking any extra load you may want to bump the PSI 3-5 PSI greater then what’s recommended.
(3) To Vroom Vroom's point, we all spent some decent money on a great car lets not let tires be an after-thought. The only thing that keeps your RX connected to the road is a rubber patch about the size of your palm - that’s all. So make sure you get some quality rubber hoops. The Japanese made tires are excellent in quality and cost less then the Michelins, the Korean made tires are getting better as well. Skip the made in China stuff you are driving a Lexus.
(4) Last try and get your RX aligned and tires rotated on a scheduled interval. I know it’s a pain in the butt to have done, but this will pay dividends by preventing irregular / premature ware and will help avoid tire noise. I always wondered what people were thinking when they would never get their tires rotated; check their air pressure, get their vehicle aligned and suspension checked, and then complain that the tire is prematurely worn and noisy.
These recommendations should help you get more mileage and comfort from your tires. Good luck!
(1) When changing tire or wheel size try and keep the overall diameter "OD" the same as the stock tire size OD. Here is how to calculate your OD:[URL="http://www.pepboys.com/learning_center/car_care/articles/tire_diameter.html"]. This will prevent you from throwing your speedometer off and yes bigger tires and wheels do typically; eat more gas and lengthen braking distance. Try and avoid using wheel spacers this just ands more weight and it was not accounted for during Lexus R&D testing.
(2) Inflate your tires per Lexus specifications. Your PSI will have the biggest impact on ride comfort next to reducing sidewall height. The recommended PSI is usually located in the driver side door jam. You will be surprised how many people just read the max PSI number on the sidewall and inflate to that level or just put 35PSI as a default. This is very important not only for safety reasons but also to maintain consistent handling characteristics. When your tires are cold, fill your air pressure 1-2 PSI below the recommendation, this is because when the tire gets warm it will raise the PSI level 1-2 PSI and get you to your recommended spec. If you plan on taking any extra load you may want to bump the PSI 3-5 PSI greater then what’s recommended.
(3) To Vroom Vroom's point, we all spent some decent money on a great car lets not let tires be an after-thought. The only thing that keeps your RX connected to the road is a rubber patch about the size of your palm - that’s all. So make sure you get some quality rubber hoops. The Japanese made tires are excellent in quality and cost less then the Michelins, the Korean made tires are getting better as well. Skip the made in China stuff you are driving a Lexus.
(4) Last try and get your RX aligned and tires rotated on a scheduled interval. I know it’s a pain in the butt to have done, but this will pay dividends by preventing irregular / premature ware and will help avoid tire noise. I always wondered what people were thinking when they would never get their tires rotated; check their air pressure, get their vehicle aligned and suspension checked, and then complain that the tire is prematurely worn and noisy.
These recommendations should help you get more mileage and comfort from your tires. Good luck!
07-13-07, 12:57 PM
#77
There you go, an expert offering his opinion....better learn from the experts!
07-13-07, 01:05 PM
#78
Super Moderator
Noting FlintRX04s point 4, I see this issue virtually all the time down here. If you look at the the driver's side front tire on a lot of vehicles here, you will see wear at the outside edges. Rotation isn't too common along with balancing down here in terms of owners carrying out such maintenance and a lot of people end up blaming the tires.
07-13-07, 02:28 PM
#79
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Great point Lexmex, tire balancing is critical as well. Typically you will see the drivers front tire wearing a little more then the other front due to the torque characteristics of a front wheel drive car. Outside edge ware can be from a number of issues such as poor camber alignment, under inflated tires or just taking corners a little too hard.
07-13-07, 03:10 PM
#80
I use to eat and breathe this tire stuff when I use to work in marketing for Yokohama tires. You all make some good points, but I thought I would give you guys some rule of thumbs to ensure you maintain a smooth and quite ride on your RX.
(1) When changing tire or wheel size try and keep the overall diameter "OD" the same as the stock tire size OD. Here is how to calculate your OD:[URL="http://www.pepboys.com/learning_center/car_care/articles/tire_diameter.html"]. This will prevent you from throwing your speedometer off and yes bigger tires and wheels do typically; eat more gas and lengthen braking distance. Try and avoid using wheel spacers this just ands more weight and it was not accounted for during Lexus R&D testing.
(2) Inflate your tires per Lexus specifications. Your PSI will have the biggest impact on ride comfort next to reducing sidewall height. The recommended PSI is usually located in the driver side door jam. You will be surprised how many people just read the max PSI number on the sidewall and inflate to that level or just put 35PSI as a default. This is very important not only for safety reasons but also to maintain consistent handling characteristics. When your tires are cold, fill your air pressure 1-2 PSI below the recommendation, this is because when the tire gets warm it will raise the PSI level 1-2 PSI and get you to your recommended spec. If you plan on taking any extra load you may want to bump the PSI 3-5 PSI greater then what’s recommended.
(3) To Vroom Vroom's point, we all spent some decent money on a great car lets not let tires be an after-thought. The only thing that keeps your RX connected to the road is a rubber patch about the size of your palm - that’s all. So make sure you get some quality rubber hoops. The Japanese made tires are excellent in quality and cost less then the Michelins, the Korean made tires are getting better as well. Skip the made in China stuff you are driving a Lexus.
(4) Last try and get your RX aligned and tires rotated on a scheduled interval. I know it’s a pain in the butt to have done, but this will pay dividends by preventing irregular / premature ware and will help avoid tire noise. I always wondered what people were thinking when they would never get their tires rotated; check their air pressure, get their vehicle aligned and suspension checked, and then complain that the tire is prematurely worn and noisy.
These recommendations should help you get more mileage and comfort from your tires. Good luck!
(1) When changing tire or wheel size try and keep the overall diameter "OD" the same as the stock tire size OD. Here is how to calculate your OD:[URL="http://www.pepboys.com/learning_center/car_care/articles/tire_diameter.html"]. This will prevent you from throwing your speedometer off and yes bigger tires and wheels do typically; eat more gas and lengthen braking distance. Try and avoid using wheel spacers this just ands more weight and it was not accounted for during Lexus R&D testing.
(2) Inflate your tires per Lexus specifications. Your PSI will have the biggest impact on ride comfort next to reducing sidewall height. The recommended PSI is usually located in the driver side door jam. You will be surprised how many people just read the max PSI number on the sidewall and inflate to that level or just put 35PSI as a default. This is very important not only for safety reasons but also to maintain consistent handling characteristics. When your tires are cold, fill your air pressure 1-2 PSI below the recommendation, this is because when the tire gets warm it will raise the PSI level 1-2 PSI and get you to your recommended spec. If you plan on taking any extra load you may want to bump the PSI 3-5 PSI greater then what’s recommended.
(3) To Vroom Vroom's point, we all spent some decent money on a great car lets not let tires be an after-thought. The only thing that keeps your RX connected to the road is a rubber patch about the size of your palm - that’s all. So make sure you get some quality rubber hoops. The Japanese made tires are excellent in quality and cost less then the Michelins, the Korean made tires are getting better as well. Skip the made in China stuff you are driving a Lexus.
(4) Last try and get your RX aligned and tires rotated on a scheduled interval. I know it’s a pain in the butt to have done, but this will pay dividends by preventing irregular / premature ware and will help avoid tire noise. I always wondered what people were thinking when they would never get their tires rotated; check their air pressure, get their vehicle aligned and suspension checked, and then complain that the tire is prematurely worn and noisy.
These recommendations should help you get more mileage and comfort from your tires. Good luck!
On 2) Recommended PSI is measured at cold, not when tire is hot. If you fill 1-2 PSI less than the recommendated PSI at cold, you are underinflating by definition.
Tire Rack Quote
The tire pressure recommended in your vehicle's owner's manual or tire information placard is the vehicle's recommended cold tire inflation pressure.
On 1) All tires throw off odometer and speedometers because new tires have larger diameter than wore tires. A new tire has 11/32 inch thread, or 9/16 inch larger in diameter than a wore tire that has 2/32 thread.
This 9/16 difference is bigger than the diameter difference between similiarly worn 235/70/16 and 225/70/16 tires.
07-13-07, 07:49 PM
#81
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TunedRX300, you are correct if the PSI states pressure @ "cold" then inflate to the stated level. Many older vehicles just had a stated inflation pressure which the 1-2 PSI rule applied. Either way expect a hot tire to raises its PSI level because of the expansion of the hot air inside. This is something we were always cognizant of during track testing of tires.
As for overall diameter "OD" its a matter of tolerance levels, this is another reason (but probably the last reason) why you should replace worn out tires due to the the decrease in overall OD. But the reality of it is this may be to minimal for your speedo to notice. Forget about the OD on a worn tire its more about the tire not being able to provide you wet weather traction when you need it. Even a tire worn down to 2/32 can still be within tolerance, but good luck driving over a pool of water at a high rate of speed. The OD rule really applies to people putting on DUBs - aka 20 inchers and above without taking into account the OD and just putting a "tire size that won't rub".
As for overall diameter "OD" its a matter of tolerance levels, this is another reason (but probably the last reason) why you should replace worn out tires due to the the decrease in overall OD. But the reality of it is this may be to minimal for your speedo to notice. Forget about the OD on a worn tire its more about the tire not being able to provide you wet weather traction when you need it. Even a tire worn down to 2/32 can still be within tolerance, but good luck driving over a pool of water at a high rate of speed. The OD rule really applies to people putting on DUBs - aka 20 inchers and above without taking into account the OD and just putting a "tire size that won't rub".
07-13-07, 07:57 PM
#82
Very true, I prefer to go for slightly larger diameter tires. Better depreciation value based on mileage.
Those Dubs rims make one wonder why won't one put a tractor rim. Frankly, it is pretty naive to ignore other factors just for that bling bling look.
Southern California is summer 3/4 of the year and no snow so summer tires with good wet for me.
Those Dubs rims make one wonder why won't one put a tractor rim. Frankly, it is pretty naive to ignore other factors just for that bling bling look.
Southern California is summer 3/4 of the year and no snow so summer tires with good wet for me.
07-15-07, 10:26 AM
#83
255/55/18 is the wrong size. This makes the vehicle ride too tall and the tires look too large. The correct size if you want a wider tire is 255/50/18. This will keep the vehicle ride height and tire diameter the same as the stock 235/55/18 tire but the tire looks a little bit wider.
07-15-07, 11:52 AM
#84
255-45-18 will be the same diameter. 255-50 is better but this size is not as popular as the 255-55's, hence are steep in price.
07-16-07, 07:25 AM
#85
255/45/18 is not the same. It is more than 4% too small. You can verify for yourself at this URL http://www.miata.net/garage/tirecalcold.html Just enter the OE tire size on the left and then enter different sizes on the right to see how they match up. 45 series is also wider than a 50 series so it probably won't fit on a 7 inch wide rim.
07-16-07, 08:07 AM
#86
You're probably right.
07-16-07, 11:30 AM
#87
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Excellent point LBCDan, a 255 50R 18 would be ideal with an overall diameter (OD) 28.03 vs. a 255/ 55R 18 OD of 29.04, stock OD is 28.17. When you increase your tire width you have to take into consideration your wheel width as well. A tire that has a 255 width typically has a wheel width range of 7-9 inches. Notice that if you use a 255 width tire on your stock 18 x 7 Lexus wheels you will be within tolerance but in the lowest width range, which will pinch the sidewalls inward. Ideally you would want to have a wheel width of 7.5 – 8.0 inches when using the 255 50R 18 in order to take full advantage of the increase in tire width. For those that are looking to go bigger on their wheels here are some recommended sizes: 255 45R 19 (OD 28.03) & 255 40R 20 (OD 28.03). Keep in mind that the wheel width and wheel offset will also affect whether or not you experience rubbing. Don’t let those big wheels on those huge SUVs fool you, a lot of them experience rubbing when doing U-turns or any hard cornering.
To calculate tire overall diameter “OD” (example 235 55R 18):
Assumption – 25.4mm in 1 inch
(1) Convert tire’s mm width into inches, 235mm / divided by 25.4mm = 9.25 inches tire width
(2) Take 9.25 inches and multiply by .55 (sidewall height is 55% of tire width) = 5.08 inches
(3) Take the 5.08 inches and multiply it by 2 (the tire has 2 sidewalls) = 10.16 inches
(4) Take the 2 combined sidewall heights 10.16 inches and add the rim size 18 = 28.16 overall diameter
Most tire manufacture websites will also show the OD for each tire size for you to reference as well. Good luck!
To calculate tire overall diameter “OD” (example 235 55R 18):
Assumption – 25.4mm in 1 inch
(1) Convert tire’s mm width into inches, 235mm / divided by 25.4mm = 9.25 inches tire width
(2) Take 9.25 inches and multiply by .55 (sidewall height is 55% of tire width) = 5.08 inches
(3) Take the 5.08 inches and multiply it by 2 (the tire has 2 sidewalls) = 10.16 inches
(4) Take the 2 combined sidewall heights 10.16 inches and add the rim size 18 = 28.16 overall diameter
Most tire manufacture websites will also show the OD for each tire size for you to reference as well. Good luck!
07-16-07, 02:41 PM
#88
How are 255-50-18 pricing? Are there Yokohamas?
07-16-07, 03:45 PM
#89
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From what I've seen not much to select from on a 255 50R 18. It goes from $160 Toyo Proxes ST to a $350 Pirelli PZero. I don't believe Yokohama makes the size. The Toyo Proxes ST is a decent tire, from what I remember they were always quick to come to the market with unique sizes and they held a good part of the market when SUV's first began putting 20 - 22 inch wheels on 5 - 6 years ago. They've always been mid-priced which made them attractive as well. However noise may become an issue later in its life if not taken proper care of.
