I was thinking today about how terrible the system for tire sizing is. There is no good reason to use section width and aspect ratio instead of overall diameter and section width when labeling tires. Also, it is a mix of metric and Imperial units. I've heard the argument that it makes plus one sizing easier because you can go one step down in aspect ratio as you step up an inch in tire size. However, it is even easier using a system of overall diameter and section width. Light Truck High Floatation tires already use this common sense system. Even if you wanted to keep metric units for O.D. and width it would be better than what we have now. Do you agree or disagree? Anyone know why we use the system we do today?
Stupidity of ISO Metric Tire Sizing System
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Originally Posted By: 440Magnum
All I can say is please don't change now, I finally got P-metric figured out!
Originally Posted By: 440Magnum
All I can say is please don't change now, I finally got P-metric figured out!
What he said.
All I can say is please don't change now, I finally got P-metric figured out!
Originally Posted By: 440Magnum
All I can say is please don't change now, I finally got P-metric figured out!
What he said.
Originally Posted By: 440Magnum
All I can say is please don't change now, I finally got P-metric figured out!
Just think how nice it would be to have a tire labeled 27 x 8.5 R15 instead of 215/70R15. Embrace the change
Originally Posted By: NHGUY
Whatever happened to G78-15? E70-14? etc...
Not going to work with today's low profile tires!
All I can say is please don't change now, I finally got P-metric figured out!
Just think how nice it would be to have a tire labeled 27 x 8.5 R15 instead of 215/70R15. Embrace the change
Originally Posted By: NHGUY
Whatever happened to G78-15? E70-14? etc...
Not going to work with today's low profile tires!
It probably makes something easier! And you can;t switch now, because other numbering systems were taken by Michelin for their stupid special tires.
TRX 240/55-390 (width, ratio, wheel diameter in mm) Still the ratio, but all metric rather than mixed.
PAX 235/710-460 (width, sidewall height, and wheel diameter, all in mm)
Originally Posted By: NHGUY
Whatever happened to G78-15? E70-14? etc...
That system is even worse! The letters are the load index, so a G78-15 is taller and narrower than a G60-15. They can carry the same weight, but probably can't be mounted on the same wheels.
TRX 240/55-390 (width, ratio, wheel diameter in mm) Still the ratio, but all metric rather than mixed.
PAX 235/710-460 (width, sidewall height, and wheel diameter, all in mm)
Originally Posted By: NHGUY
Whatever happened to G78-15? E70-14? etc...
That system is even worse! The letters are the load index, so a G78-15 is taller and narrower than a G60-15. They can carry the same weight, but probably can't be mounted on the same wheels.
First, there have been many sizing systems used for tires:
http://barrystiretech.com/tiresizing.html
If you look carefully, you only need three numbers to describe the physical dimensions - and the only number that is ALWAYS used is the wheel diameter.
To complicate matters further: Even the numbers aren't precise. Let's take Fsharp's suggestion - which is used for Flotation tires: 31X10.50R15LT.
You would think the diameter is 31.00". Nope, It's 30.52". And the 15" wheel diameter? It's actually 14.968"!
No matter what system is used, there are quirks. My suggestion is get used to it.
http://barrystiretech.com/tiresizing.html
If you look carefully, you only need three numbers to describe the physical dimensions - and the only number that is ALWAYS used is the wheel diameter.
To complicate matters further: Even the numbers aren't precise. Let's take Fsharp's suggestion - which is used for Flotation tires: 31X10.50R15LT.
You would think the diameter is 31.00". Nope, It's 30.52". And the 15" wheel diameter? It's actually 14.968"!
No matter what system is used, there are quirks. My suggestion is get used to it.
Bicycle tire size conventions are even worse.
Originally Posted By: Nate1979
Imagine you were the guy who just invented the tire and now needed to describe the size. Who in their right mind would think to use the current system of aspect ratio instead of actual dimensions?
Aspect ratio is much easier to understand than actual dimension in mm or inch.
One example is if I like to +0 my tire from 225/45-17 then I need to increase the width by 30 mm and reduce ratio by 5 to keep the same overall diameter.
The other one is +1: change tire/wheel from 235/45-17 then the similar diameter is either 255/35-18 or 235/40-18.
With actual dimension in mm:
235/106-17(235/45-17)
255/89-18(255/35-18)
235/94-18(235/40-18)
Imagine you were the guy who just invented the tire and now needed to describe the size. Who in their right mind would think to use the current system of aspect ratio instead of actual dimensions?
Aspect ratio is much easier to understand than actual dimension in mm or inch.
One example is if I like to +0 my tire from 225/45-17 then I need to increase the width by 30 mm and reduce ratio by 5 to keep the same overall diameter.
The other one is +1: change tire/wheel from 235/45-17 then the similar diameter is either 255/35-18 or 235/40-18.
With actual dimension in mm:
235/106-17(235/45-17)
255/89-18(255/35-18)
235/94-18(235/40-18)
Originally Posted By: HTSS_TR
Aspect ratio is much easier to understand than actual dimension in mm or inch.
One example is if I like to +0 my tire from 225/45-17 then I need to increase the width by 30 mm and reduce ratio by 5 to keep the same overall diameter.
Not really sure it's easier. How does a typical person know that if he adds 30mm to the width, then he should drop the ratio by 5? You still have to calculate the overall diameter to see how close you are to the original.
This will also vary depending on the original tire width. For example, if your original tire was 185/65/15, then a +0 would require increasing the width by only 20mm and dropping the ratio by 5.
Aspect ratio is much easier to understand than actual dimension in mm or inch.
One example is if I like to +0 my tire from 225/45-17 then I need to increase the width by 30 mm and reduce ratio by 5 to keep the same overall diameter.
Not really sure it's easier. How does a typical person know that if he adds 30mm to the width, then he should drop the ratio by 5? You still have to calculate the overall diameter to see how close you are to the original.
This will also vary depending on the original tire width. For example, if your original tire was 185/65/15, then a +0 would require increasing the width by only 20mm and dropping the ratio by 5.
Like Quattro Pete said, plus sizing using the actual dimensions would be easier. A 225/45r17 is about a 25X9R17. To go to a wider tire you would not do any calculations simply add an inch, or whatever, to the width. So a 25X9R17 would be a 25x10R17. To go to an 18 inch wheel simply go from a 25X9R17 to 25X9R18. It can't be easier than that.
Originally Posted By: HTSS_TR
Originally Posted By: Nate1979
Imagine you were the guy who just invented the tire and now needed to describe the size. Who in their right mind would think to use the current system of aspect ratio instead of actual dimensions?
Aspect ratio is much easier to understand than actual dimension in mm or inch.
One example is if I like to +0 my tire from 225/45-17 then I need to increase the width by 30 mm and reduce ratio by 5 to keep the same overall diameter.
The other one is +1: change tire/wheel from 235/45-17 then the similar diameter is either 255/35-18 or 235/40-18.
With actual dimension in mm:
235/106-17(235/45-17)
255/89-18(255/35-18)
235/94-18(235/40-18)
99.9% of people on the street would not understand what you just said nor ever face the situation you just describe. Even if someone wanted to change tire size they would just ask the tire shop what their options are.
Originally Posted By: Nate1979
Imagine you were the guy who just invented the tire and now needed to describe the size. Who in their right mind would think to use the current system of aspect ratio instead of actual dimensions?
Aspect ratio is much easier to understand than actual dimension in mm or inch.
One example is if I like to +0 my tire from 225/45-17 then I need to increase the width by 30 mm and reduce ratio by 5 to keep the same overall diameter.
The other one is +1: change tire/wheel from 235/45-17 then the similar diameter is either 255/35-18 or 235/40-18.
With actual dimension in mm:
235/106-17(235/45-17)
255/89-18(255/35-18)
235/94-18(235/40-18)
99.9% of people on the street would not understand what you just said nor ever face the situation you just describe. Even if someone wanted to change tire size they would just ask the tire shop what their options are.
Use a tire size calculator. You can even put the app on your phone. Good way to kill time. Comparing dimensions of different size tires.
The best system is commonly used for race tires. Michelin commonly uses this system referring to their race tires.
It is labelled as follows. Tread Width/Inflated Diameter (tire height) - Rim Diameter in centimeters
For Example
20/65-18. This tire has approximately 20cm (200mm) tread width, 65cm (650mm) inflated diameter and 18" rim mounting diameter
17/65-15 has approximately 17cm (170mm) tread width, 65cm (650mm) inflated diameter and 15" rim mounting diameter.
Now if only they could switch over to the metric system for wheels as well......
It is labelled as follows. Tread Width/Inflated Diameter (tire height) - Rim Diameter in centimeters
For Example
20/65-18. This tire has approximately 20cm (200mm) tread width, 65cm (650mm) inflated diameter and 18" rim mounting diameter
17/65-15 has approximately 17cm (170mm) tread width, 65cm (650mm) inflated diameter and 15" rim mounting diameter.
Now if only they could switch over to the metric system for wheels as well......
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Just an FYI:
There isn't a common sizing system for racing tires. I've seen them using the regular street tire system (eg 275/45R17), a system using mm's and diameter (eg 600/255R13), the same system using centimeters, the same using inches - each of which would constitute a different system.
And as far as switching to a metric wheel system: It could be done, but that means that all the old inch based wheels would gradually not have tires available. Yes, that is somewhat what is going on with 13" and 14" now, but we are talking a HUGE!!! change. It's just not going to happen. (and, NO!, you can't just restate a 17" wheel as a 431.8 mm, besides the 17" is really a 16.948" which is 430.5 mm. Confusing, huh!)
There isn't a common sizing system for racing tires. I've seen them using the regular street tire system (eg 275/45R17), a system using mm's and diameter (eg 600/255R13), the same system using centimeters, the same using inches - each of which would constitute a different system.
And as far as switching to a metric wheel system: It could be done, but that means that all the old inch based wheels would gradually not have tires available. Yes, that is somewhat what is going on with 13" and 14" now, but we are talking a HUGE!!! change. It's just not going to happen. (and, NO!, you can't just restate a 17" wheel as a 431.8 mm, besides the 17" is really a 16.948" which is 430.5 mm. Confusing, huh!)
The current sizing system is very good and it had been in use for more than 30-40 years. If it was stupid and/or confusing system it wouldn't adopted long time ago.
Originally Posted By: HTSS_TR
The current sizing system is very good and it had been in use for more than 30-40 years. If it was stupid and/or confusing system it wouldn't adopted long time ago.
Ha! Same can be said about imperial system. Why do we still have it when there is metric?
I guess if you use something long enough, you get used to it and making a radical change would be too disruptive.
I too agree that once you understand it, the current tire sizing system works OK. Is there a better system out there? Possibly, but I don't find the current system bothersome to such a degree that would have me seeking something different.
The current sizing system is very good and it had been in use for more than 30-40 years. If it was stupid and/or confusing system it wouldn't adopted long time ago.
Ha! Same can be said about imperial system. Why do we still have it when there is metric?
I guess if you use something long enough, you get used to it and making a radical change would be too disruptive.
I too agree that once you understand it, the current tire sizing system works OK. Is there a better system out there? Possibly, but I don't find the current system bothersome to such a degree that would have me seeking something different.
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