explain plus sizing?

[tommygunn]

Hello:
I got 185-70R14's on my car, and would like to plus size, but keep my odo/speed(ometer) accurate, what are my options?

I'm aware of all these tire calculators (miata.net, and 1010tires.com or whatever) that allow comparison of 2 sizes side by side, but I'm really a tire noob and don't know where I'd "start" as far as incrementing the sizes.

I'm willing to jump 2 or 3 inches (from R14 to 15-16) - yes, I've been looking at wheel packages too

 

[Colt45ws]

My first thought would be 195/60R15. Thats a common size with a good selection. Essentially identical diameter with the same load rating.
There are also a couple maybe in 16".
195/55R16 - Slightly bigger (within 1%); loses one load index number. Depending on what pressure you car specifies, this might be okay, just means it needs a bit more pressure...
205/50R16 - Slightly smaller, but getting into the area where differences between manufacturers probably amounts to more difference. Same load index issue as above.
I didnt check these two for tire availablity.

 

[CapriRacer]

Make it easy on yourself. Both Tire Rack or Discount Tire Direct will walk you through the plus sizing process on their web sites. They'll tell you what works - both tires and wheels.

From those web sites, you ought to be able to figure out what is going on. If you need technical assistance understanding what they are doing, come back here.

 

[mpvue]

+1 on using tire rack for info. but basically, the numbers in the tire mean:
185: width of tread in milimeters
70: aspect ratio, meaning the sidewall is 70% of the width
14: rim diameter

so, knowing all that, you can figure out the height of the wheel to compare with other sizes (for the speedo to be correct, the wheels need to be the same height)

185mm(or 7.28")x70%=5.1"x2=10.2"+14"=24.2" overall height

 

[Quattro Pete]

Originally Posted By: CapriRacer
Make it easy on yourself. Both Tire Rack or Discount Tire Direct will walk you through the plus sizing process on their web sites. They'll tell you what works - both tires and wheels.

Absolutely!

Whatever you get there is guaranteed to fit your vehicle.

Otherwise, the problem with some of those online calculators like miata, etc. is that they will compare two tires, but can't possibly tell you whether the new setup will rub because it's too wide, too tall, or the new wheel has incorrect offset. TireRack has already done all that legwork for you.

 

[hate2work]

Originally Posted By: mpvueso
knowing all that, you can figure out the height of the wheel to compare with other sizes (for the speedo to be correct, the wheels need to be the same height)

185mm(or 7.28")x70%=5.1"x2=10.2"+14"=24.2" overall height


Why do the wheels need to be the same height? Don't you mean tires?

 

[Quattro Pete]

By wheels he probably means rims+tires. The sum of the rim diameter plus the height of the tire sidewall (x2) should remain the same.

 

[A_Harman]

Or another way you could approach it is to find out what optional upgrade wheels and tires were available for your particular car, then try to buy a set on e-bay or craigslist. Or sometimes you can get take-offs from Discount Tire.
Since they were available from the factory, they would be sure to fit without issues.

I bought a set of 17" SS wheels for my Camaro for $400 via e-bay a few years ago.

 

[40Deluxe]

This is the best advice Discount Tire will walk you thru process,they are very good at what they do,plus they will ship for free at least they use to,i have bought two set of tires from them and had no issues.

 

[Carbon]

'"
Originally Posted By: tommygunn
Hello:
I got 185-70R14's on my car, and would like to plus size, but keep my odo/speed(ometer) accurate, what are my options?


What is your motivation for "plus sizing" of your tires?

 

[meep]

pay close attention to the weight of the miata wheels. what gen/year is it? the oem alloys are extremely light while being stronger than equivalent weight aftermarket. the miata purists strongly advise against changing the wheels due to increased unsprung weight as it upsets a very painstakingly-tuned suspension. It's a big deal on that vehicle if you truly "drive it."

I had a 97 with the stock alloys. think they were 195 60 15?? was AWESOME!

 

[George Bynum]

Originally Posted By: Carbon
What is your motivation for "plus sizing" of your tires?
Doesn't EVERYONE do it so they will have less wet and snow traction ... are there other reasons?

(that is a joke, not a flame or other bait ... it is amazing how many think that wider and shorter sidewalls yield nothing but positives. We all need to understand that there are pluses and minuses to almost everything.

Thanks, Carbon, for asking a very important question.

 

[SteveSRT8]

What's really amazing is that there are people out there unaware that a simple tire upgrade can dramatically improve their car's performance.

Typical factory tires are easily improved upon.

Wheels are an entirely different subject, too many variables to list.

 

[marc1]

Originally Posted By: Carbon

What is your motivation for "plus sizing" of your tires?


I can't predict with certainty the OP's reasons but a good guess would be the gradual obsolescence of 14" tires. There isn't much choice anymore. All my 14" vehicles that haven't already been converted to 15" will on the next tire change.

 

[Carbon]

Originally Posted By: marc1
Originally Posted By: Carbon

What is your motivation for "plus sizing" of your tires?


I can't predict with certainty the OP's reasons but a good guess would be the gradual obsolescence of 14" tires. There isn't much choice anymore. All my 14" vehicles that haven't already been converted to 15" will on the next tire change.

While that is reasonable, I would place my bets elsewhere.

 

[tommygunn]

Looks was the primary reason for upsizing. No, it's not a Miata I got the tires on lol, I was only referencing the "famous" miata.net tire sizing calculator

But yea, I've been looking around "locally" for tires, and there isn't much to chose from as far as 14" tires.....sure, tire rack, etc. has a lot to chose from. But when I'm stuck between a rock and a hard place, I don't want to be stuck on the side of the road waiting for a tire rack shipment If you get my drift.

Being primarily driven in FL, snow isn't a problem, we do get our wet seasons here.....but that's about it, I'm not running drag slicks or anything