Tire Plus-Sizing Question: Why MUST Tire/Wheel Get WIDER When +Sizing?

Who says it's hard?

The plus-size rim and tire both get wider, and the sidewall of the tire becomes shorter("lower profile"), maintaining correct speedometer ratios.

the diameter of the rim. The width(side to side) of both the rim and tire used should remain the same. The only difference is the sidewall of the new tire will be shorter("lower profile"), to compensate for taller rim and maintaining height for correct speedometer.

width change).

for negoticating rain and snow).

keeping correct height for speedometer) so hard to accomplish?

It's not "hard" just do the math... but most of the time when someone goes to the trouble of buying a wheel/tire package in a non-standard size, they are looking for a wider footprint for better dry cornering.

If you're worried about snow driving, "plus-sizing" is probably not for you. What I would recommend is getting a summer and winter set of wheels/tires - using your stock wheels (possibly with *narrower* tires, if it's recommended by the manufacturer) with dedicated snow tires for winter, and the "plus-sized" ones for summer. If you're just after the big rim look... well, it can be done, but I'm over that... not real concerned about what you think my car looks like so much as how it drives. If I even owned a "car" anymore, which I don't, but that's another story for another time.

nate

ze is the diameter of the rim.  The width(side to side) of both the rim a nd tire used should remain the same.  The only difference is the sidewall of the new tire will be shorter("lower profile"), to compensate for taller rim and maintaining height for correct speedometer.

eeping correct height for speedometer) so hard to accomplish?

The lower the profile, the wider the tread and rim size required, even if the nominal tire width (the 225 part of 225/60-15, for example) remains the same. And the load the tire can handle depends on the air inside it, so if you have less sidewall, you have to compensate by going wider or you will lose your load rating.

Your scheme would actually require to "upgrade" from say a 225/60-16 to a. 215/55-17. Except that you have now lost one unit of load, and that tire is bigger in diameter anyway. a (slightly smaller diameter)

215/50-17 loses you a lot of load capacity.

I'm sorry, but most of that simply isn't true.

Less sidewall usually means a stiffer sidewall, which in turn means that the tire's flex under loads--particularly cornering--can be adequately controlled at lower inflation pressures. Since the size of the contact patch is inversely proportional to the inflation pressure and since rubber is not a truly linear friction material, you get better grip with lower pressures from shorter sidewalls.

Making the tire wider doesn't change that.

Nope. Simply not so.

Case in point:

Toyo Proxes T1 Sport tires in 235/45-17 are 24.3" in diameter and have a load rating of 1477 pounds.. Upsize to 18" rims and keep the same width, and you'll run 235/40-18s which are 24.7" in diameter and have a max load of 1521 pounds.

it's not "hard to accomplish" - it's simple math. if you don't want to do that yourself, use this:

untrue.

untrue.

that is a downgrade on tire width.

no, you're confused between tire diameter and rim diameter. it's possible to increase wheel diameter an reduce tire diameter at the same time. or vice versa.

load is nothing to do with size and everything to do with the tire cordage and construction.

So in short it is possible to do what I want, it's just may be a little mor e challenging and expensive to find the combo that will also keep the speed ometer accurate. My speedometer is already indicating 2-3mph faster than I' m actually going(GPS) so I can't afford to err even more in that direction. :)

challenging and expensive to find the combo that will also keep the speedometer accurate. My speedometer is already indicating 2-3mph faster than I'm actually going(GPS)

I noticed my mph was showing fast with the tires that came with the car (used.) Something like the speedo would show 60 but I really was doing 58. When it was time to replace them I used the OEM size. That fixed that. Wouldn't trust the GPS I have. I used highway mile markers and a stopwatch while on cruise, which is rock steady on my Lumina.

The GPS finding was confirmed by another source: p-o'd drivers highbeaming me and passing me like Meat Loaf! I finally adjusted for true 65mph, which is 68 on my speedometer, and I was more with the flow.

-CC

plus-size rim and tire both get wider, and the sidewall of the tire becomes shorter("lower profile"), maintaining correct speedometer ratios.

the diameter of the rim. The width(side to side) of both the rim and tire used should remain the same. The only difference is the sidewall of the new tire will be shorter("lower profile"), to compensate for taller rim and maintaining height for correct speedometer.

width change).

for negoticating rain and snow).

correct height for speedometer) so hard to accomplish?

The answer is simple, most people who "plus" size don't want to also spend money on a new set of rims.

That makes NO sense Ashton! Any plus-sizing(the traditional waybor the way I want to) requires taller and/or wider rims. Go back, read what you just posted, and think real hard about it.

-CC

want to) requires taller and/or wider rims. Go back, read what you just posted, and think real hard about it.

I hate to point this out but a lot of people do a lot of things with tires that make no sense. Between the plus-sizing, the dubs, the rotating hubcaps and the blue lights, it's a wonder you can get stock tires anymore.

--scott

______________ What he said made no sense - about people not wanting to spend money on new rims

- that's what I was pointing out. Of course your rim size will change when you

+size. LOL!

-CC

-CC

rims - that's what I was pointing out. Of course your rim size will change when you +size. LOL!

All the plus sizing things I've seen are for wider tires with a lower aspect ratio - the net result is the same rolling radius.

Here's what wikipedia says: Plus sizing is the practice of changing a specific tire to a larger size while compensating with reductions in other aspects of the tire's size so that the new tire has the same diameter and circumference as the original tire to prevent any changes in speedometer accuracy, torque and traction control.

The LOL's on you.

"While compensating in reductions of other aspects of the tire's size" impl ies that side wall height(profile) will change, in turn implying a change i n RIM diameter. You stated earlier "people dont want to spend money on new RIMS". ALL plus-sizing, wheth the traditional method(lower profile & wide r) or my method(lower profile tire but same width tire & rim) require purch ase of appropriate size rims to compensate. Even a rancher from Texas know s that!

I think this conversation has become muddied by confusion over the terms "w idth" and "diameter". Think of it this way: WIDTH is the measurement of the rim/tire as you are facing the front or back of car head on. DIAMETER is the measurement of the wheel package when you are facing the SIDE of the ve hicle. A US Quarter(25 cents just so we're on the same page!) is NOT 15/1

6" wide(!) - it is 15/16" in DIAMETER. It is only about 3/32" WIDE!

"width" and "diameter". Think of it this way: WIDTH is the measurement of the rim/tire as you are facing the front or back of car head on. DIAMETER is the measurement of the wheel package when you are facing the SIDE of the vehicle. A US Quarter(25 cents just so we're on the same page!) is NOT 15/16" wide(!) - it is 15/16" in DIAMETER. It is only about 3/32" WIDE!

Maybe you're confused but I'm not. Plus sizing NEVER referred to anything but wider-and-lower-profile tires on the same rims. If you use different rims then you aren't plus sizing, you are "buying a different tire and wheel package". There's nothing complicated or confusing about it.

Then you need to check out:

It sure looks to me like the rims in that diagram are changing dimensions! Anyone else?

-CC

"width" and "diameter". Think of it this way: WIDTH is the measurement of the rim/tire as you are facing the front or back of car head on. DIAMETER is the measurement of the wheel package when you are facing the SIDE of the vehicle. A US Quarter(25 cents just so we're on the same page!) is NOT 15/16" wide(!) - it is 15/16" in DIAMETER. It is only about 3/32" WIDE!

No, plus sizing refers to getting different rims and also tires with about the same rolling diameter. e.g.

stock: 175/70R13

+1: 185/60R14 +2: 195/50R15 +3: 205/40R16

(to use an example with which I'm familiar; that is, the typical tire sizes used on an A1 or A2 chassis Volkswagen. I've used all of the above at one time or another save for the +3; +2 is a little stiff with aftermarket springs and shocks on anything but a well maintained road.)

that's the way that term has been used for decades...

(hint: don't search for "plus size" without any other keywords...)

nate