Lighter tire with a higher load capacity?

[geekster]

This probably is a dumb question, so sorry. Looking at tires for the wifes Acura and was on Treaddepot and was comparing the CS5 to the RT43. It shows in the comparison this

RT43
Load Rating 1,654 lbs
Maximum PSI 51
Section Width 9.20"
Weight 21.20 lbs

CS5

Load Rating 1,477 lbs
Maximum PSI 44
Section Width 9.20"
Weight 26.90 lbs

I honestly don't know if this matters at all. It just struck me as odd. Is there a benefit to a lighter tire with higher load capacity? Or, is it better the other way around?

 

[Quattro Pete]

What size?

Is the RT43 XL-rated?

I would say higher load rating will give you more security blanket and is less likely to overheat under load, but as long as the load rating is as least as high as required for your vehicle, it probably doesn't really matter. However, typically the higher load rating is achieved by having extra reinforced sidewalls, which may or may not negatively impact ride quality.

As far as weight, I would say less weight is better. It is unsprung weight positioned in the outer perimeter of the wheel, so it impacts acceleration and stopping distances. But of course stopping distances are also greatly affected by the actual rubber and tread pattern used.

 

[geekster]

Sorry size listed for each on the site are

225/50R17 ALTIMAX RT43 98V

225/50R17 CS5 ULTRA TOUR 94V BLK

I don't know on the XL part.

Also per the interwebs the load cap on the oem Michelin Pilot HX MXM4 is 1433lbs

 

[Eddie]

Load difference is reflected in the maximum pressure difference. Ed

 

[Quattro Pete]

Originally Posted By: geekster
225/50R17 ALTIMAX RT43 98V

225/50R17 CS5 ULTRA TOUR 94V BLK

I don't know on the XL part.

Yup, the General is XL rated, and that's why it has load rating of 98 as opposed to 94 for the Cooper.

 

[leeharvey418]

As Ed noted, the big tipoff is in the maximum inflation pressure.

If you look at the full service description for each tire, you'll note the '98V XL' on the General and the '94V' (with no additional qualifier) on the Cooper.

 

[Quattro Pete]

Originally Posted By: leeharvey418
As Ed noted, the big tipoff is in the maximum inflation pressure.

But it's also worth noting that max load capacity is not measured at max inflation pressure.

For standard euro-metric tires, max load capacity is measured at 36 PSI.
For XL euro-metric tires, max load capacity is measured at 42 PSI.

 

[rslifkin]

Originally Posted By: Quattro Pete
Originally Posted By: leeharvey418
As Ed noted, the big tipoff is in the maximum inflation pressure.

But it's also worth noting that max load capacity is not measured at max inflation pressure.

For standard euro-metric tires, max load capacity is measured at 36 PSI.
For XL euro-metric tires, max load capacity is measured at 42 PSI.


Interesting... I wonder why there are so many cases of non-XL tires being rated for high pressures when it doesn't increase their weight carrying ability. The summers on my Jeep are rated for 51 psi max, the winters for 47 (neither are XL rated).

 

[geekster]

Originally Posted By: Quattro Pete
Originally Posted By: leeharvey418
As Ed noted, the big tipoff is in the maximum inflation pressure.

But it's also worth noting that max load capacity is not measured at max inflation pressure.

For standard euro-metric tires, max load capacity is measured at 36 PSI.
For XL euro-metric tires, max load capacity is measured at 42 PSI.


So I usually run the Michelin's at 36psi on her car. If I were to run the same 36psi on either General or Cooper the load cap wouldn't change?

 

[Quattro Pete]

Originally Posted By: rslifkin
Interesting... I wonder why there are so many cases of non-XL tires being rated for high pressures when it doesn't increase their weight carrying ability.

According to TireRack, "This is done to accommodate the vehicle manufacturers desire to tune the tires' high-speed capability, handling qualities and/or rolling resistance to better suit the vehicle."

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=21

 

[Quattro Pete]

Originally Posted By: geekster
So I usually run the Michelin's at 36psi on her car. If I were to run the same 36psi on either General or Cooper the load cap wouldn't change?

Can't really tell since we don't know what the General's load carrying capacity would be at 36 PSI. We only know what it is at 42 PSI. Maybe there is some formula/guide to estimate it though...

 

[leeharvey418]

Originally Posted By: Quattro Pete
But it's also worth noting that max load capacity is not measured at max inflation pressure.

That's why I said it was a tipoff... not the end of the discussion.

 

[rslifkin]

Originally Posted By: Quattro Pete
Originally Posted By: geekster
So I usually run the Michelin's at 36psi on her car. If I were to run the same 36psi on either General or Cooper the load cap wouldn't change?

Can't really tell since we don't know what the General's load carrying capacity would be at 36 PSI. We only know what it is at 42 PSI. Maybe there is some formula/guide to estimate it though...


Some manufacturers release a load capacity vs pressure chart for their tires.

 

[geekster]

So I guess in the end it really doesn't matter as long as it meets or exceeds oem specs..? Probably end up with the CS5 as they are in stock. Thanks for the info everyone!

 

[CapriRacer]

Originally Posted By: Eddie
Load difference is reflected in the maximum pressure difference. Ed


Sorry, that is not correct. In passenger car tires, the maximum inflation is relative independent and arbitrary. I go into that in more detail here: Barry's Tire tech - Load Tables The pertinent passage is about 1/3 of the way down: Notes on page 1-34.

And, yes, the General is an XL (Extra Load) and the Cooper is an SL (Standard Load) - and that's why the load carrying capacities are different - and while those capacities occur at different inflation pressures, that difference is NOT reflected in the maximum pressures.

And relative to the differences in weight: They are more a reflection of:

1) The ability of the tire designer to minimize the amount to material needed to do the job.

2) The ability of the tire manufacturer to consistently meet the specs as written by the tire designer.

Assuming we are talking about apples to apples comparisons.

And lastly, the difference in construction to get that added load carrying capacity is so small that other things will cause larger weight differences.