Zapata

ok so since our cars are heavy we need to be careful by not going to low on the load rating.

However, what if you have lightweight rims, headers(stainless steel v. cast iron)? Does the drop in weight give you a little more flexiblity??

Nashua_Night_Hawk

No... CLP needs 91 and CLS needs 93 my 18" nitto are 91...

Zapata

wha? you're post makes no sense

automatic:
CLP 3470 lbs
CLS 3510 lbs

louisn

LOad rating escapes me for our car? I couldn't get 1400 pounds in my car if I tried. Usually it's just me at 170 lbs. If I had 3 more passengers it still would't be more than 800lbs? I bought the sumotomos which are great but only have load rating of 91 while the OEM Mich's (suck bigtime) are rated 93. What's the deal?

Fabvsix

I have 91 rating SO3's on stock rims. If you plan on having (3) 500 lb women in your car and driving across the Arizona desert in the middle of August at 120 mph, then MOST likely you'll be just fine at 91......

Tom2

I'm not so sure that the rims would make a difference, since they're basically unsprung weight.

Zapata

Tom,
the entire mass of the car is reduced. How could it now make a difference??????

Tom2

Unsprung weight has a different effect....

But like I said, I'm not sure how it would affect load ratings.

mattg

my yoko's are reinforced, 93W

EricL

The difference in weight from headers, lightweight wheels is very, very small.

People keep bringing up the CLP/CLS issue. Yes, the CLP only requires a 91 rating.

However, the CLS requires a 93 rating.

Does it really matter? Who knows for sure.

However, do a little math:

Take 3600 lbs * 0.63 (take into account the front weight bias) and then divide by two to get the weight on each from wheel:

== 1134 lbs.

The 93-load rating is 1433 lbs.

That's a nice 300 lb margin.

When you drive, you are not only applying static loads to the car (its weight == mass * gravity), you are also applying dynamic forces and the car has a lot of weight on the front of it (the tires get to handle the steering loads, dynamic loads, and transmit the power to the road). Now imagine, you’re at high speed, and are making turns. The load on the front tires is higher that what a RWD vehicle’s fronts would see. Now add some passengers and high temps…

Go look at Michelin's site and look at the MXM4 that came with the car. In the .pdf file, there is a table that indicates how to increase the air pressure with increased speeds.

http://michelinman.com/assets/pdfs/doc_pilotmxm4.pdf

If you look carefully, the MXM4 (in the V rating), will only support 91 percent of its load rating at 149 MPH.

Now the 1433 turns into 1433 * 0.9 = 1298.0 max lbs. (and this requires the XL tires to be pumped up with an additional 5 PSI).

If you only drop 100 lbs off the car, you remove (100 * 0.63) / 2 = 31.5 lbs off each front tire (this makes certain assumptions about where the weight is lost).


So, if you plan on breaking the ACL top speed record, stick with high load rated, Z, W, Y tires.

IF you drop 100 lbs with performance parts, it's only good for change in rating to 92 (from 93). (

If you drive slow enough -- no freeway -- an 88 rated tire will do fine...

YMMV

EricL

Extreme city:

If the rims were 200 lbs vs. 50, that would be 150 lbs more weight (force) pushing down on the bottom of the tire that wasn't there before. (that's a load).

More "common" changes of stock wheel weight == 26 vs. forged == 13, the difference is small and would only be 13lbs less. However, it would make a difference (see #2).

AND

2. The increased mass of the wheels would increase the transient loading on the bottom of the tire when it hit small bumps, etc. Less mass == less loading (tires as spring + damper with wheels as mass)

The tires support the rims too...

lou_RENAMED

Eric nice explanation and I understand what your saying in my opinion a 93 load rating would be great but is it possible to have to high of a load rating. Wouldn't that also effect the driving impression cause the tires would have no give they will be like solid rocks. If the car calls for a 93 and you do some lighweight modifications that will only make the 93 perform better. My question is why would a 97 be better than lets say a 93 or 94 respectively.

EricL

IMO, It is impossible to have too high a load rating.

The load rating is not directly related to how the road feels. However, IT CAN have an impact -- it depends. The Toyo's have a 97W rating and have a reinforced casing. There are extra plies to strengthen the tire. I think it rides fine, but you won't see a bulge like you will with the stock MXM4s in the front.

Extra load rating is like insurance. Unless you need it, you're just paying extra money for nothing.

The tires I purchase just happened to have a 97W rating. I was going to get some RE-730s (1st) and they had a 91-93 rating (This was back in Aug 2000).

Ask other members on the forum about the Toyos in 235/45-17 (97W) and or the 225/45-17 (94W) and ask them how they ride.

Here is something that may help (something to consider).

A material can have very high burst strength, but be very flexible. Another material can be very stiff, but have a very low bust strength.

There are some "R" rated street/track (DOT approved R rubber) that have middle range load ratings (go look at Tire Rack), and they will knock the fillings out of your teeth.

IOW, load rating and stiff sidewall (harsh ride) have nothing to do with each other.

(Think of those big mushy truck tires with 101 load ratings that look like balloons).

RE: 97 better then 93, etc. I don’t know about that. It’s just added protection at high speeds, in the dessert, etc. I’m sure about 200 analogies could be though of that relate to insurance and/or protection.

Zapata

Eric,
Thanks a bunch! I didn't think it'd be huge difference since in the scheme of things the weight difference is huge like you illustrated in your exam in your post to Tom2.