Tire load index - 91 or 94 XL?

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13 February 2013
nordwulf

Tire load index - 91 or 94 XL?

Saab recommends tires with a load index of 94 XL for my 9-5. The new tires I want to get have a load index of 91.

The weight of the Saab 9-5 with full fuel tank and other fluids is 3460 - 3780 lbs or 1570 - 1715 kg
Gross vehicle weight is 4390 - 4710 lbs or 1990 - 2135 kg

I don't know the exact front/rear weight distribution for the 9-5 but let's be safe and say it is 60/40 front/rear. So the max GVW for the front wheels is 2826 lbs / 2 = 1413 lbs. Wet weight max of the 9-5 comes to 1134 lbs per tire.

Maximum load for a 91 tire is 1356 lbs. The 94 XL is 1477 lbs.

I will never have a load of 1000 lbs in my Saab and reach the max GVW. I also used the max weight numbers so actual weights are most likely less. So it seems tires with a load index of 91 should be fine, right? Or shouldn't you mess with this and get the 94? I have had tires with a load index of 91 on a Saab 9-5 wagon before and all seemed fine.

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13 February 2013
Dave T

I know of someone with a Saab that said he needs tires with a load index of 97 and the tire shop will not sell him a 94 rated tire.

I think that part of the rationale for the tire index is to decrease the probability of tire failure. A blow out is inconvenient, sometimes catastrophic. Wheel well damage and even death has happened. If a tire performances exactly to the specification of the load index, then most people will probably be fine with a tire that has a load index of 3 too low. If the tire has low air pressure, it won't support a load as well. In the late 1990's, there were a series of deaths in Ford Explorers from tire problems. That resulted in Ford recommending that tires not be older than six years old. I think Ford also increased the recommended tire pressure.

The bottom line is that you will probably be fine but a 91 tire would reduce the safety margin to some unknown extent (unknown to me but statisticians probably have an idea).

Snow tires often have a higher load index. My 9-3 requires a 93 but my snow tires are 97. My summer tires used to be 97 but now I am driving on 94's. I think, but am not certain, that some early 9-3's specified 91 and 9-3 Sport Combis specify 97.

I pondered the load index question because I bought a spare wheel to use as a full sized spare. A regular tire almost fits in a 9-3. I put a rubber spacer, which came with the car as packing for the springs, in the trunk so the floor rests on that, not the full sized spare. I did consider a narrower tire with about the same diameter but such tire had a reduced load index, possibly 89. At the end, I did not buy an odd sized tire.
13 February 2013
Burnsside42

I never pay too much attention to it honestly - but I know the XL is a very good thing. It means the tire is a step above the norm.
13 February 2013
Shazam

Quote:

Originally Posted by Burnsside42

I never pay too much attention to it honestly - but I know the XL is a very good thing. It means the tire is a step above the norm.

So what is the difference in a 94 vs a 94XL. Do they both exist?
13 February 2013
Dave T

Quote:

Originally Posted by Shazam

So what is the difference in a 94 vs a 94XL. Do they both exist?

Yes. A tire like 215/55R16 94H would be a usual tire. If it had a high load index, it could be 97H XL. A 94 XL tire is probably a smaller tire with a 94 load index. That's the practical answer.

The legalese answer is that it is a standard load tire but you can increase the tire pressure and increase the load slightly to 94.