Does the Load rating matter when buying new tires?
#1
04-10-2009, 04:40 PM
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#2
04-10-2009, 05:22 PM
The load rating basically tells you how stiff the sidewall is. If one tire has a load rating of 94 and the other 100, the 100 will be a little stiffer, can carry more total vehicle weight, and will have a slightly harsher ride. But it will also be a little tighter in the turns, and usually a little more expensive (just a few $$ per tire).
In general, if the width goes up but the aspect ratio stays the same (235/45 to 245/45), the wider tire will be stiffer, i.e. have a higher load rating. If the width stays the same but the aspect ratio goes down (235/45 to 235/40), the shorter tire will be softer, i.e. have a lower load rating. But it's not universal, just a guideline. The speed rating also comes into play. If identical tires have different speed ratings (V vs. W), the higher speed tire will usually have a higher load rating. A manufacturer may also make a "regular" version with a 93 or 94, and an XL version that's 100. I couldn't find a specific example of this, but I've seen it. Here are some General Exclaim UHP specs:
215/45-18 = 93 (XL)
225/45-18 = 91
235/45-18 = 94
245/45-18 = 100 (XL)
255/45-18 = 99
235/40-18 = 91
235/45-18 = 94
235/50-18 = 97
235/55-18 = 100
As far as what was stock/OEM, I don't know for sure, but my guess would be in the mid-90's, 94 or 96. The 89 seems a little low for a stock/OEM G35 tire unless it's a 16". An 89 would be found on a smaller tire that isn't expected to carry as much weight, like a 205/55-16.
In general, if the width goes up but the aspect ratio stays the same (235/45 to 245/45), the wider tire will be stiffer, i.e. have a higher load rating. If the width stays the same but the aspect ratio goes down (235/45 to 235/40), the shorter tire will be softer, i.e. have a lower load rating. But it's not universal, just a guideline. The speed rating also comes into play. If identical tires have different speed ratings (V vs. W), the higher speed tire will usually have a higher load rating. A manufacturer may also make a "regular" version with a 93 or 94, and an XL version that's 100. I couldn't find a specific example of this, but I've seen it. Here are some General Exclaim UHP specs:
215/45-18 = 93 (XL)
225/45-18 = 91
235/45-18 = 94
245/45-18 = 100 (XL)
255/45-18 = 99
235/40-18 = 91
235/45-18 = 94
235/50-18 = 97
235/55-18 = 100
As far as what was stock/OEM, I don't know for sure, but my guess would be in the mid-90's, 94 or 96. The 89 seems a little low for a stock/OEM G35 tire unless it's a 16". An 89 would be found on a smaller tire that isn't expected to carry as much weight, like a 205/55-16.
Last edited by BuckeyeInMI; 04-10-2009 at 05:44 PM.
#3
04-12-2009, 09:50 AM
The load index tells you how much weight the tire will support before EXPLODING after the intial safety reserve is used up.
Different brands have different safety reserve.
Don't confuse static load with panic braking or 0.9G turning loads which can add 300+ pounds to the weight on a tire. Also remember the tires are not inflated to 44/51 psi where the load is specified.
Test by Michelin show when you upgrade the oem load index the tires last ~ 2/3 the % upgrade. A 10% stronger tire should last 7% longer at minimum.
Different brands have different safety reserve.
Don't confuse static load with panic braking or 0.9G turning loads which can add 300+ pounds to the weight on a tire. Also remember the tires are not inflated to 44/51 psi where the load is specified.
Test by Michelin show when you upgrade the oem load index the tires last ~ 2/3 the % upgrade. A 10% stronger tire should last 7% longer at minimum.
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