275 on 10.5"
- Thread starter chefwong
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Ah......NO!!!!!!!!
It's a bit more complicated then that!
You have to consider the whole size.
A P275/35R20 will fit on a 9 to 11 rim, but a P275/70R16 fits on a 7 to 9 rim.
So unless the aspect ratio is 45 or lower, a 10" wide rim is too wide.
Why do you ask??
It's a bit more complicated then that!
You have to consider the whole size.
A P275/35R20 will fit on a 9 to 11 rim, but a P275/70R16 fits on a 7 to 9 rim.
So unless the aspect ratio is 45 or lower, a 10" wide rim is too wide.
Why do you ask??
Without giving complete sizes this is all gobbley-gook.
Bob
Bob
Originally Posted By: chefwong
There was both a 275/40/20 and 275/55/20
Do you realize that those two sizes will give you a 3.4 inch different diameter and a 11.3% difference in gearing and speedometer reading? What is the stock size for this car?
I highly recommend you run the stock and proposed sizes through a tire size calculator like the one at http://www.miata.net/garage/tirecalc.html before you do something bad to your car. There is more to tire size than getting it to fit on the wheel.
There was both a 275/40/20 and 275/55/20
Do you realize that those two sizes will give you a 3.4 inch different diameter and a 11.3% difference in gearing and speedometer reading? What is the stock size for this car?
I highly recommend you run the stock and proposed sizes through a tire size calculator like the one at http://www.miata.net/garage/tirecalc.html before you do something bad to your car. There is more to tire size than getting it to fit on the wheel.
Those are some serious oem sizes. What kind of car is this?
Originally Posted By: chefwong
You're right. I decided to go with a 275/40/
With a 55 sidewall, why would it not fit a 10.5" rim.
Any insight would be great.
Basically it's this:
If you consider a tire to be a circular toroid:
The taller the sidewall, the more the tire resembles a circle - and the less the part of the bottom is cut off.
However, tires aren't actually circular toroids, but the basic principle applies.
You're right. I decided to go with a 275/40/
With a 55 sidewall, why would it not fit a 10.5" rim.
Any insight would be great.
Basically it's this:
If you consider a tire to be a circular toroid:
The taller the sidewall, the more the tire resembles a circle - and the less the part of the bottom is cut off.
However, tires aren't actually circular toroids, but the basic principle applies.
Patman
Staff member
My Corvette's back rims are 18x9.5 and they have 275-40-18s on them, so 275s will easily fit on a 10.5" rim.
Originally Posted By: Patman
My Corvette's back rims are 18x9.5 and they have 275-40-18s on them, so 275s will easily fit on a 10.5" rim.
Like I said, it's more complicated than that.
Every tire size has an acceptable ranges of values for rim width - the nominal size rim (commonly called the "measuring rim") and an allowable deviation from that. Anything different from the measuring rim will change the footprint pressure distribution and this affects not only wear, but also handling characteristics. Staying within the rim width range will assure that the rim will not appreciably alter the tread arch - and therefore the footprint.
Please note: It is physically possible to mount a tire on rims outside the acceptable rim width range. "Stretching" is a common term used to describe using a rim width that is wider. For practical purposes, this takes sidewall flexing out of the picture and while it looks "Cool", it really hurts the ride qualities.
Using a rim that is too narrow tends to arch the tire tread and you may experience a kind of stability problem - the vehicle would seem sensitive to bumps and road crown.
Using the Corvette as an example: It came with P275/40R18's on the rear with 9.5" rims for the 1997 thru the 2004 model years. The "Measuring Rim" for a P275/40R18 is 9.5" with an allowable range of 9" to 11".
So in this case the vehicle is equipped with rims at the nominal rim width, but this isn't always the case. I have seen many vehicles where the OE rim width is the absolute minimum for the tire size.
Hope this helps.
My Corvette's back rims are 18x9.5 and they have 275-40-18s on them, so 275s will easily fit on a 10.5" rim.
Like I said, it's more complicated than that.
Every tire size has an acceptable ranges of values for rim width - the nominal size rim (commonly called the "measuring rim") and an allowable deviation from that. Anything different from the measuring rim will change the footprint pressure distribution and this affects not only wear, but also handling characteristics. Staying within the rim width range will assure that the rim will not appreciably alter the tread arch - and therefore the footprint.
Please note: It is physically possible to mount a tire on rims outside the acceptable rim width range. "Stretching" is a common term used to describe using a rim width that is wider. For practical purposes, this takes sidewall flexing out of the picture and while it looks "Cool", it really hurts the ride qualities.
Using a rim that is too narrow tends to arch the tire tread and you may experience a kind of stability problem - the vehicle would seem sensitive to bumps and road crown.
Using the Corvette as an example: It came with P275/40R18's on the rear with 9.5" rims for the 1997 thru the 2004 model years. The "Measuring Rim" for a P275/40R18 is 9.5" with an allowable range of 9" to 11".
So in this case the vehicle is equipped with rims at the nominal rim width, but this isn't always the case. I have seen many vehicles where the OE rim width is the absolute minimum for the tire size.
Hope this helps.
Originally Posted By: CapriRacer
Originally Posted By: chefwong
You're right. I decided to go with a 275/40/
With a 55 sidewall, why would it not fit a 10.5" rim.
Any insight would be great.
Basically it's this:
If you consider a tire to be a circular toroid:
The taller the sidewall, the more the tire resembles a circle - and the less the part of the bottom is cut off.
However, tires aren't actually circular toroids, but the basic principle applies.
CapriRacer, that's good info, thanks.
Originally Posted By: chefwong
You're right. I decided to go with a 275/40/
With a 55 sidewall, why would it not fit a 10.5" rim.
Any insight would be great.
Basically it's this:
If you consider a tire to be a circular toroid:
The taller the sidewall, the more the tire resembles a circle - and the less the part of the bottom is cut off.
However, tires aren't actually circular toroids, but the basic principle applies.
CapriRacer, that's good info, thanks.
I'm still sort of curious what kind of car has OEM tires of front 275/40/20 and rear 315/35/20. Ar you sure those are the OEM sizes, or are they the sizes that happen to be on the car now?
Chef,
A P275/45R20 has a nominal rim width (also called measuring rim) of 9" with an allowable range 8 1/2 to 10.
So 10.5 would be "stretching".
Can you actually get it to work? Probably.
Is it a good idea? If you want the tire to do anything other than look good - No!
"Stretching" a tire (mounting a tire on a rim wider than the allowable range) effectively takes the sidewall out of the equation. That means the tire stifness will be incredible. It will corner instantaneously, but the tire will have the cusioning qualities of an anvil.
Not to mention wear.
But Chef!!!!
My book says BMW X5's have 10" rims on the front and 11" on the rear with the tire sizes 275/40R20 and 315/35R20.
A 275/45R20 will fit on the 10", but there is more to this than just being able to get a tire to mount on the rim.
1) Load carrying capacity. One of the necessary functions of a tire is to carry the load of the vehicle. Needless to say a car's weight isn't evenly distributed front to rear nor side to side.
A basic principle in engineering is that oversizing something is safer. (a better way to put would be underutilize).
In this case, BMW selected tires with 106 and 110 Load Index.
- and you should, too!
BTW, both of these are Extra Load tires.
The 275/45R20's I have looked up come in 106 (SL) and 110 (XL)
2) The physical dimensions of a tire aren't regulated. That means that tires of the same size from different manufacturers may have quite different diameters and widths. This makes changing tire sizes somewhat problematical.
Plus the physical space available in the fenderwells is something that has to be measured. It may look like there is plenty of space, but remember, the worst case is when the suspension is fully compressed and the steering wheel is fully turned. It is amazing how tight the space becomes when the steering wheel is fully turned. (Not to mention how much the tire distorts under cornering forces.)
Anyway!!!
I'm not sure what you are trying to accomplish, but I have a feeling you are headed into an area where there are landmines.
A P275/45R20 has a nominal rim width (also called measuring rim) of 9" with an allowable range 8 1/2 to 10.
So 10.5 would be "stretching".
Can you actually get it to work? Probably.
Is it a good idea? If you want the tire to do anything other than look good - No!
"Stretching" a tire (mounting a tire on a rim wider than the allowable range) effectively takes the sidewall out of the equation. That means the tire stifness will be incredible. It will corner instantaneously, but the tire will have the cusioning qualities of an anvil.
Not to mention wear.
But Chef!!!!
My book says BMW X5's have 10" rims on the front and 11" on the rear with the tire sizes 275/40R20 and 315/35R20.
A 275/45R20 will fit on the 10", but there is more to this than just being able to get a tire to mount on the rim.
1) Load carrying capacity. One of the necessary functions of a tire is to carry the load of the vehicle. Needless to say a car's weight isn't evenly distributed front to rear nor side to side.
A basic principle in engineering is that oversizing something is safer. (a better way to put would be underutilize).
In this case, BMW selected tires with 106 and 110 Load Index.
- and you should, too!
BTW, both of these are Extra Load tires.
The 275/45R20's I have looked up come in 106 (SL) and 110 (XL)
2) The physical dimensions of a tire aren't regulated. That means that tires of the same size from different manufacturers may have quite different diameters and widths. This makes changing tire sizes somewhat problematical.
Plus the physical space available in the fenderwells is something that has to be measured. It may look like there is plenty of space, but remember, the worst case is when the suspension is fully compressed and the steering wheel is fully turned. It is amazing how tight the space becomes when the steering wheel is fully turned. (Not to mention how much the tire distorts under cornering forces.)
Anyway!!!
I'm not sure what you are trying to accomplish, but I have a feeling you are headed into an area where there are landmines.
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Thanks for the informative post Capri. I'm debating how to utilize my stock OEM rims. OEM is 20x9.5 and 20x10.5.
Ultimately I guess I will order two 9.5 for the rear to utilize a working set of 275/40 which is a ++++ as I was thinking about it last night, cause it would allow me to rotate the tires as well - especially with the camber setup I have dialed in.
Ultimately I guess I will order two 9.5 for the rear to utilize a working set of 275/40 which is a ++++ as I was thinking about it last night, cause it would allow me to rotate the tires as well - especially with the camber setup I have dialed in.
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