Tire Sizes With Larger Wheels Rx300

[sigtauenus]

I have a 2000 RX 300 that we bought with 18" RX350 wheels already on it. Story was a friend of the seller totalled the RX350 and they got the wheels and tires free.

We have always had a problem with the tires rubbing up front against the inner wheelwell with the steering wheel against the stop in either direction.

We will need tires soon so I want to size the tires closer to OEM size to avoid the rubbing.

OEM tire size is 225/70 R16 - dimensions spec out to 29" high by 10.0" wide

Current tire size is 255/55 R18 - dimensions spec out to 28.4" high by 8.9" wide

Keeping the 18" wheels, the closest tire size I have found to the OEM spec is 225/60 R18 which is 28.6" high by 8.9" wide

Primary concern is the possibility that the wheel itself is not wide enough to support the thinner tire.

Lastly, Lexus is built for comfort, not necessarily performance, and this is my wife's car. The tires that are on there now (don't recall the brand) look like they belong on my Mustang. What's a good all season tire (brand/type) that has good longevity that is good for the typical soccer mom. (my kids don't play soccer yet, but that's the profile my wife fits). We live in Virginia Beach.

[pauljcl]

I have a 2000 RX 300 that we bought with 18" RX350 wheels already on it. Story was a friend of the seller totalled the RX350 and they got the wheels and tires free.

We have always had a problem with the tires rubbing up front against the inner wheelwell with the steering wheel against the stop in either direction.

We will need tires soon so I want to size the tires closer to OEM size to avoid the rubbing.

OEM tire size is 225/70 R16 - dimensions spec out to 29" high by 10.0" wide

Current tire size is 255/55 R18 - dimensions spec out to 28.4" high by 8.9" wide

Keeping the 18" wheels, the closest tire size I have found to the OEM spec is 225/60 R18 which is 28.6" high by 8.9" wide

Primary concern is the possibility that the wheel itself is not wide enough to support the thinner tire.

Lastly, Lexus is built for comfort, not necessarily performance, and this is my wife's car. The tires that are on there now (don't recall the brand) look like they belong on my Mustang. What's a good all season tire (brand/type) that has good longevity that is good for the typical soccer mom. (my kids don't play soccer yet, but that's the profile my wife fits). We live in Virginia Beach.

I can't help decide the relative width or rim vs. tire - though I would assume another course of action would be to get (exchange) the 18" rims against 16" ones or even 17" ones... [but I am a believer in OEM sizes of rims for cars, and unles sthere is good reason, I do not favour taller rims which usually weigh more, thus increasing unsuspended weight and have more inertia, which reduces acceleration and braking power].But it might help to know the relative circumferences of tire/rim combinations, and to that end, you might wish to use the following website:

http://www.miata.net/garage/tirecalc.html

Good luck!

[PK_3]

As simple trick is in understanding the tire designations, first, Tte "55" "225 55- 18" is where the "55" is the percentage of the width of the width of the tire, in this case "225" . So: 55% of 225 is you sidewall height in millimeterrs. Im not sure the side walls heigth includes part tucked under the rim ( or the sum of the 2 sidewalls height), call a tire shop (probavly ou try wikipedia this, (http://en.wikipedia.org/wiki/Wheel_sizing describes it better) or call your tire guy.

On one care I've been running 17 235 40's on rims that are about an inch narrower than the rims (same as your reassons). no probs in 4 years

Regards, PK.

[lemon]

235/55/18 is the stock tire size for the 18" wheels on the 330/400h. They are very close in overall size to your stock 225/70/16.

You may find your rubbing problem goes away as well, since the 235 is a narrower tire than the 255.

[sigtauenus]

235/55/18 is the stock tire size for the 18" wheels on the 330/400h. They are very close in overall size to your stock 225/70/16

Thanks for the replies, particularly the OEM size for RX330. The miata calculator helped too, it said the size I came up with was .08% bigger than the stock size, while the RX330 size above is .08% smaller. I guess that's closest I can get either side of OEM for my car. Since the RX330 is a stock size for those years, that probably means tires that size are more readily available so I'll go that route.

Again, thanks for the replies, very helpful.

[pauljcl]

235/55/18 is the stock tire size for the 18" wheels on the 330/400h. They are very close in overall size to your stock 225/70/16

Thanks for the replies, particularly the OEM size for RX330. The miata calculator helped too, it said the size I came up with was .08% bigger than the stock size, while the RX330 size above is .08% smaller. I guess that's closest I can get either side of OEM for my car. Since the RX330 is a stock size for those years, that probably means tires that size are more readily available so I'll go that route.

Again, thanks for the replies, very helpful.

Thank you for the 'thanks' -- but, if you are putting those tires on a RX300, they will all be of a circumference that is too large. The RX300 came with 16" wheels....

[lemon]

No, they won't. The rim size is going to increase 2" (16 - 17 - 18), but the tire profile will be reduced 3 sizes (70 - 65 - 60 -55), so the overall diameter of the wheel and tire together (which is very important) will be almost the same - 28.4 inches for the stock and 28.2 inches for the 235/55/18. This is known as 'plus' sizing and is done regularly when upgrading wheel size. The diameter difference is 0.81%, which is well within the recommended range of 3% difference or lower.

This can be confirmed as you already recommended at http://www.miata.net/garage/tirecalc.html

or this one http://www.1010tires.com/tiresizecalculator.asp

You'll want to compare 225/70/16 to 235/55/18.

By the way, the circumference (which is nowhere near as important as the diameter) is actually LESS with the 235/55/18/ (89.22 for the 16" combo vs 88.49 for the 18" combo).

My suggestion to the original poster stands - keep the 18" wheels and get the 235/55/18 tires.

[pauljcl]

No, they won't. The rim size is going to increase 2" (16 - 17 - 18), but the tire profile will be reduced 3 sizes (70 - 65 - 60 -55), so the overall diameter of the wheel and tire together (which is very important) will be almost the same - 28.4 inches for the stock and 28.2 inches for the 235/55/18. This is known as 'plus' sizing and is done regularly when upgrading wheel size. The diameter difference is 0.81%, which is well within the recommended range of 3% difference or lower.

This can be confirmed as you already recommended at http://www.miata.net/garage/tirecalc.html

or this one http://www.1010tires.com/tiresizecalculator.asp

You'll want to compare 225/70/16 to 235/55/18.

By the way, the circumference (which is nowhere near as important as the diameter) is actually LESS with the 235/55/18/ (89.22 for the 16" combo vs 88.49 for the 18" combo).

My suggestion to the original poster stands - keep the 18" wheels and get the 235/55/18 tires.

You are right. I hadn't realized the drastic effect of the sidewall ratio, and I was guessing at the weight difference. [Diameter and circumference are of the same effect, since the only difference is a mathematical constant (PI).]

[lemon]

No, they won't. The rim size is going to increase 2" (16 - 17 - 18), but the tire profile will be reduced 3 sizes (70 - 65 - 60 -55), so the overall diameter of the wheel and tire together (which is very important) will be almost the same - 28.4 inches for the stock and 28.2 inches for the 235/55/18. This is known as 'plus' sizing and is done regularly when upgrading wheel size. The diameter difference is 0.81%, which is well within the recommended range of 3% difference or lower.

This can be confirmed as you already recommended at http://www.miata.net/garage/tirecalc.html

or this one http://www.1010tires.com/tiresizecalculator.asp

You'll want to compare 225/70/16 to 235/55/18.

By the way, the circumference (which is nowhere near as important as the diameter) is actually LESS with the 235/55/18/ (89.22 for the 16" combo vs 88.49 for the 18" combo).

My suggestion to the original poster stands - keep the 18" wheels and get the 235/55/18 tires.

You are right. I hadn't realized the drastic effect of the sidewall ratio, and I was guessing at the weight difference. [Diameter and circumference are of the same effect, since the only difference is a mathematical constant (PI).]

Hahaha...first time I've seen PI mentioned on a car forum. Nice one!