wheel sizing

[jc_cab]

whats up guys im new here just sold my lexus to get a somewhat family car so i joined this forum (originally from clublexus) anyways i have a 2016 mazda cx-5 currently on the 17 inch wheels with the 225.55.17 tires i think thats the tire size anyways my question is whats the biggest size rim you can put on there to keep your mpg at where its at? in other words how big can i go with more rim less tire type of this cause i believe the diameter of my wheels now are 28 inches total is it possible to but a 22 with a 30 series tire diameter of that comes out being 29 as well or 20 inch wheels with a 35 series tire? thanks in advanced

 

[B-ham Gary]

Holy lack of periods, Batman!

Try a tire size calculator like this one and go nuts: https://www.rimsntires.com/specspro.jsp

Fuel economy depends more on how you drive. If you always travel at a constant speed down the interstate, mileage won't differ much with a large wheel versus a small one (assuming aero and rolling resistance effects aren't large). On the other hand, larger wheels typically mean more mass. More mass takes more energy to accelerate -- translationally and rotationally. More energy means mileage suffers. Stop and go traffic will be a worse case scenario for fuel economy if you go with "big" wheels.

You should be more concerned with ride and handling degradation than fuel economy loss with larger wheels. Again, larger wheel are typically heavier, which increases suspension unsprung mass. Higher rotating mass will also affect braking performance, but I'm not sure if it's enough to be concerned about unless you go to stupid-heavy wheels. In addition, larger wheels with lower aspect ratio tires increase the chance for pinch flats or damaged wheels. There are plenty of examples of folks on this board sharing their experiences with 20" -- and larger. In fact, there's a whole thread devoted to people's tire and wheel choices.

Personally, I think it's nuts to go with 20" or larger wheels. The ride harshness, tire $$$ prices, and risk of damage would not make up for a nicer look to me. I do like looking at what others have chosen, though.

 

[jc_cab]

My plans are to go eith some 20s with 225.35.20 tires which would be the same height as 19s w 225.55.19

 

[Chris_Top_Her]

20x8.5 et 40 is a good size, sidewalll between 110-120mm.

 

[leeharvey418]

A 225/35R20 tire wouldn't even be close to the right size. As a general rule of thumb, if you keep the tire width the same and go up one inch in wheel diameter, the aspect ratio goes down by 5% - so a 225/55R19 would be about the same outside dimensions as a 225/50R20. A quick check of Tire Rack indicates that you're not going to find anything in that size.

If you're genuinely worried about maintaining fuel economy, a smaller, lighter wheel is better. If you're willing to shell out the money for a 20" wheel that's under 25 pounds, a 245/45R20 tire is a good choice. For the money, though, you're far better off going with a 19" package.

 

[Ride92]

Google tire size calculators and pick one to play with. You just have to remember you need to keep the overall diameter the same as the stock set up. There's a lot of good options out there for wheels. Don't let the nay Sayers dismay you, it's your car do what you want. Like others have said the larger the rim, the smaller the side wall, the harsher the ride is going to be. I wouldn't recommend going with anything larger then 20". While your at it, consider getting a wider rim, something in the 8-9" range which will allow you run wider tires often with better selection. I think going with a 235 or 245 series tire would be a reasonable upgrade. Some will argue that wider tires mean a larger contact patch and thus hurts your mpg, but you also have a wider contact patch and more rubber on the road for better grip when cornering.

 

[B-ham Gary]

Some will argue that wider tires mean a larger contact patch and thus hurts your mpg, but you also have a wider contact patch and more rubber on the road for better grip when cornering.

Yeah, a wider tire may result in high rolling resistance and aero drag, but I think that's splitting hairs at the level of changes people are thinking of making. The only concern I'd have for going wider is a higher degree of hydroplaning, so I'd look for a tire that's rated well for water evacuation, being here in the PNW. ;-) I must say 235-245mm wide tires sure look better...

 

[gimor]

First, welcome to the forum.

Stock 17" tires are 65 aspect not 55 also the diameter is 28.5"
One thing I love about Tire Rack is they list actual diameters under the specs tab.
I second the url below.
Plug in specs of origional tire an rim in first column and put in specs of tire/rim you're wanting in second.
Then scroll down a bit and see what the results say.
https://www.rimsntires.com/specspro.jsp