Tire Size

[2011KR]

I've tried searching and I've found a few posts of people with larger tires, but I couldn't tell if there was any lift or not. Will 265/50r20 tires fit on stock 20" wheels at stock height. I'm a truck guy so I'd be all for a lift and bigger tires. However, my wife would not, but if I can go up a bit and get some Cooper AT3s at stock height that'd be great!

 

[peterk9]

What is the tire size that you are replacing? The size that came with the vehicle.
You can use the following site to check the sizes and see how much the overall diameter changes. That is what would affect the 'stock height' of the vehicle.
https://www.tacomaworld.com/tirecalc?tires=245-60r18-265-50r20

Peter

 

[MikB]

I've tried searching and I've found a few posts of people with larger tires, but I couldn't tell if there was any lift or not. Will 265/50r20 tires fit on stock 20" wheels at stock height. I'm a truck guy so I'd be all for a lift and bigger tires. However, my wife would not, but if I can go up a bit and get some Cooper AT3s at stock height that'd be great!

I have been wanting to get a set of all terrains for my Ex and I've found that I could get a set of Goodyear all terrains in 265/50/20's that will fit the stock rims. Difference in diameter compared to the tires I have which are the Hankooks in less that 1/2 an inch. Well within the percentage range recommended. They are the only tires in this size I've found and that's OK by me. I'm a Goodyear All terrain fan as I have them on my Ranger and have had many years of experience with these tires. They are at a reasonable price as well.

 

[2011KR]

Thanks for the replies! They are within 1/2" of the OE tires. (255/50) I just wasn't sure if I'd getting any rubbing while turning. I've always been a Cooper guy, but I did just put some wheels on my truck that had Duratracs on them with plenty of tread so I decided to leave them on and I've been quite impressed!

 

[Tom Champagne]

Getting new tires this spring and was wondering if 265-50-20 would give a better ride than 255-50-20? It’s within the 3% of tire size variance.

 

[peterk9]

Hi Tom. I moved your thread here which is about the same size you are looking at.
I believe it is the sidewall height that affects the ride more than anything. The higher the sidewall the more flex or cushioning there will be. A wider tire will give you a little more grip but will also increase rolling resistance and be more prone to hydroplaning and will not perform as well in deep snow compared to a narrower one.

Peter

 

[Tom Champagne]

Hi Tom. I moved your thread here which is about the same size you are looking at.
I believe it is the sidewall height that affects the ride more than anything. The higher the sidewall the more flex or cushioning there will be. A wider tire will give you a little more grip but will also increase rolling resistance and be more prone to hydroplaning and will not perform as well in deep snow compared to a narrower one.

Peter

Thanks. I believe I’ll get a better ride with any tire except the OEM Hankooks. I’ve hated them from day one but it’s my wife’s vehicle so I don’t drive it much. Probably go with the Bridgestone Dueler Alenzas.

 

[KayGee]

I'm going to put this here for those that wish to educate themselves further. SAME SIZE BUT DIFFERENT DIMENSIONS - Tire Business


How can tires of the same nominal size designation vary in diameter by as much as an inch or more? One reason is that the Tire & Rim Association's voluntary guidelines, which most manufacturers follow, afford designers considerable latitude in determining tire section width and outer diameter—provided the sum of these two dimensions meets or exceeds the ``minimum size factor'' established by the TRA.

Put another way, when a tire's section width is added to its outer diameter, the total must exceed the number listed for that size under the ``minimum size factor'' column in the TRA yearbook.

In the case of the ill-matched General Ameri. way and Michelin XH4 tires cited in the accompanying article, the inflated Ameri.way's section width measured 7.77 inches, which, when added to the tire's 27.11-inch outer diameter, totals 34.88 inches—a sum comfortably above the 34.55-inch minimum size factor established for size P205/75R15.

The XH4's 8.30-inch section width, when added together with its 26.49-inch diameter, yields a total of 34.79—which likewise exceeds the TRA's minimum size factor for that designation.

Thus, the dimensions of both tires were well within industry guidelines even if they varied enough in circumference to damage a four-wheel-drive vehicle's transfer case.

At the extreme, a tire designer could come up with a P205/75R15 tire as large as 27.3 inches in diameter or as small as 26.22, said a tire engineer who asked not to be identified.

That amounts to more than an inch of difference when the tires are new. It doesn't take into account the additional size difference that will accrue if one tire is brand new and the other is worn.

``That's why vehicle and tire manufacturers are constantly making recommendations to replace a set of tires as opposed to replacing individual ones,'' he said.

The website everyone around here likes to reference only provides an estimate, not the actual diameter of the tire you have or want to replace it with. If your current tire is on the smaller end of the spec and the new tire is on the larger end of spec, you may find yourself outside of what that site recommends. Conversely, the website may tell you that you are outside its recommendation, but if you measure the actual installed tires, you may find the opposite. Same with the section width. It is not an exact science. Depending on the actual tire and the rim it is mounted on, the section width can vary. Tires of a given width are typically optimized for a rim near the maximum width range specified by their manufacturer. In other words, if you had an 8" wide rim and are looking at a tire spec'd for 6.5-8" wide rims and another spec'd for 7.5-9" wide rims, you'd be better served choosing the first tire over the second.

 

[peterk9]

This site provides actual sizes; 255/50-R20 vs 235/65-R18 Tire Comparison - Tire Size Calculator | Tacoma World

Peter

 

[KayGee]

This site provides actual sizes; 255/50-R20 vs 235/65-R18 Tire Comparison - Tire Size Calculator | Tacoma World

Peter

The site provides actual sizes of what? All the user does is key in some generic sizing info into that website and it makes some rough calculations based on those entries. It doesn't know the actual dimensions of any tires, otherwise it would require the user to pick specific brands and models of tires in addition to entering the generic p-metric sizing, and the width of rims they will be installed on.

The actual tire you buy in whatever size may vary from brand to brand and model to model within a brand. The dimensions will also vary depending on what width rim they are installed on. It's theoretically possible that you could find a 255/55R20 and a 255/50R20, or a 255/50R20 and a 265/50R20, tire that actually measure out to the same circumference.

Some sites provide more detailed info on tires so you can get an idea of the circumference variance among tires that are marked as the same size. For example, in 255/55R20 size tires, the measured circumference could be as little as ~93" to as much as ~96" which would give a diameter of ~29.5-30.5". This roughly translates into the smallest tire requiring ~680 revolutions per mile whereas the largest one would only require ~660. At the end of the day, you really need to install the actual tires on your rims, inflate them, and measure them to confirm actual size.

For those that ascribe to the school of thought that AWD systems are very picky and require closely matched tires, then you should always measure your tires whenever replacing them, to make sure they are within whatever tolerance level you are comfortable with. Tires 101 on Tire Matching on All Wheel and Four Wheel Drive :: Souza's Tire Service

ETA - Peter, you may want to measure the actual circumference of your Blizzaks and then measure your 20s and see what they actually are. I believe the Blizzaks fall a little closer to the smaller side of specs (~91" circumference which should be ~29.1" diameter - compared to the 255/50R20s, I imagine they will be around an inch larger diameter and up to 3" more on circumference - depending on wear on both tires). I've had a few different winter tires that were the same way - actual measurements were further off than the calculations indicated.

 

[peterk9]

.........................ETA - Peter, you may want to measure the actual circumference of your Blizzaks and then measure your 20s and see what they actually are. I believe the Blizzaks fall a little closer to the smaller side of specs (~91" circumference which should be ~29.1" diameter - compared to the 255/50R20s, I imagine they will be around an inch larger diameter and up to 3" more on circumference - depending on wear on both tires). I've had a few different winter tires that were the same way - actual measurements were further off than the calculations indicated.

Thanks for the info. Measuring the circumference difference on my 2 sets would be a little difficult in my case in that I have the dealer stores the set I'm not using. Food for thought.

Peter

 

[KayGee]

Thanks for the info. Measuring the circumference difference on my 2 sets would be a little difficult in my case in that I have the dealer stores the set I'm not using. Food for thought.

Peter

I'm not all that hungry right now, but why would it be difficult in your case? All you have to do is measure the ones that are on the vehicle now and jot down the circumference, then measure the other set after they are switched and compare. The only difference is the time delay to get measurements from both sets, but the difficulty is no different than if you had both sets in your possession. If you time it right and bring a cloth/flexible tape measure with you when you get them switched over, you should be able to get both measurements at the same time.

 

[curlywurly]

You might want to read my thread from a few weeks ago, I've just done the opposite to you!
Notes on tire sizes

 

[SLail]

Hey everyone, I am about to change my tires but I have not been able to settle on what tire size to get. I know a large amount of you are using the 295/45/R20 for your wheel setups but I wanted to get everyone's opinion on whether I should go for the size of 285/50/R20 or 285/45/R20?

Please let me know

 

[peterk9]

The standard (OEM) size for the XLT is a 245/60R18. Of the sizes you mentioned, the best option to stay within the generally recommended 3% maximum diameter variance would be 285/45R20 with a variance of 1.8%. The 295/45R20 is right on the 3% and the 285/50R20 is way over at 5.6%.
245/60-R18 vs 285/45-R20 Tire Comparison - Tire Size Calculator | Tacoma World
FYI, I have OEM 20" on my Explorer and use the 18" wheels for Winter. I find that the 18" tires provide a slightly better ride and provide a little better protection from 'curb rash'.

Peter

 

[KayGee]

Rim width determines min/max tire width. A 295 width tire is recommended for ~10-12" rims. Do you have factory rims or aftermarket? What is the width of your rims?

 

[SLail]

Rim width determines min/max tire width. A 295 width tire is recommended for ~10-12" rims. Do you have factory rims or aftermarket? What is the width of your rims?

Planning on putting on a set of 20 inch Velgen VMB7s on the vehicle

 

[SLail]

The standard (OEM) size for the XLT is a 245/60R18. Of the sizes you mentioned, the best option to stay within the generally recommended 3% maximum diameter variance would be 285/45R20 with a variance of 1.8%. The 295/45R20 is right on the 3% and the 285/50R20 is way over at 5.6%.
245/60-R18 vs 285/45-R20 Tire Comparison - Tire Size Calculator | Tacoma World
FYI, I have OEM 20" on my Explorer and use the 18" wheels for Winter. I find that the 18" tires provide a slightly better ride and provide a little better protection from 'curb rash'.

Peter

So this might sound stupid on my part but what exactly is the implication of a greater than 3% diameter variance? or diameter variance in general?

 

[peterk9]

So this might sound stupid on my part but what exactly is the implication of a greater than 3% diameter variance? or diameter variance in general?

Here is an excerpt from the linked article; It is generally felt that you can change sizes if the difference is kept within 3 per cent, but what you are proposing falls well outside that range - in excess of 8 per cent. The problem is that many functions of a modern vehicle are dependent on tire speed data, including not only the speedometer but ABS, stability control and others.
Changing tire size will throw many systems off
Oversized wheels and tires also add extra weight which can negatively affect the traction control system and put more strain on the brakes and suspension. Several tire comparison sites will have a pop-up message displayed when you exceed the 3% figure.
Tire size calculator: compare tires online

Peter

 

[KayGee]

If you want to keep using bringing up the 3% rule, at least use some semi-legit source material and not some Dear Abby equivalent article written for the globe and mail.

Years ago, several tire manufacturers recommended that plus-size fitments remain within 3% of the diameter of the OE tire specified on the placard. Since then, very few, if any, have continued to publish that guideline, but it still exists in the Tire Industry Association’s (TIA) Automotive Tire Service (ATS) Program and will remain there because it has been used in a number of legal cases. There have also been a number of tests in the past that showed exceeding the 3% guideline can have a negative effect on vehicle stability, electronic stability control, and other ride or braking systems.

Avoid the Lawsuit Blues: 5 Ways to Protect Yourself When Installing Custom Tires and Wheels - Retail - Modern Tire Dealer

The rule was essentially created as a "rule of thumb", but morphed into a CYA measure to deflect liability from the tire manufacturer down to the installer in the case of a lawsuit and remains because it has been used in lawsuits. The Tire Industry Association (TIA) is basically a non-profit lobbying group.

Here's a paper (The Impact of Plus-Sized Wheel/Tire
Fitment on Vehicle Stability ) written by PhD's and it seems light on specifics and conclusions, but please read it for yourself and draw your own conclusions -> https://pdfs.semanticscholar.org/d439/850a85e23041eb17c5a388c44fe007a8477b.pdf

Oldie, but a goodie: "However, it is widely accepted that a variance of 2% to 3% or less (depending on which tire or auto maker you talk to) should pose no adverse effects on ABS, traction control or vehicle stability control system operation." Tire/wheel plus-sizing: Changing the look also changes the performance - Retail - Modern Tire Dealer

So, 2% to 3% or less, is widely accepted as okay, depending on who you talk to...and should pose no adverse effects...real scientific statement there from modern tire dealer

Here's someone (That’s About the Size of It: Understanding Tire Size | Tire Recappers) that says up to 15% is okay for some SUVs and trucks - How do you choose the right tires? First of all, a tire needs to be able to carry the weight of your vehicle. Secondly, to ensure the accuracy of speed data through the car’s computer, it’s important to look at tire diameter. A good rule of thumb is to stay within a 3% diameter change (3/4 inch diameter change), though pick-ups and SUVs can often handle up to a 15% oversize tire.