Tire Load Rating...how important is it really??

[db12]

I track my S4 several times per year and have been running the Michelin Sport Cup 2's. Primarily because they meet the load rating and have R compound. However Im wanting to switch to a more affordable option. The majority of other recommended track tires for our cars do not meet the load rating index. How important is that measure really?

[dls11b8]

In my experience, very. My last set of tires I had installed soon after purchasing my car(it was sold with winters on) were not load rated XL, and the ride was terrible, the sidewalls were always bulged like they were overloaded... I got about 10k out of the set before they were completely shot, and as soon as I switched, the ride was instantly 100x better. no more speed wobble, shimmys, shakes, or tread pinching. And before you guys blame alignment, thats what I thought it was too. Had it in 3 times in 4 months for alignment, and finally a tire switch was what fixed it.

[theweebabyseamus]

Not usually something you want to mess with, if you had a failure it could be a big deal. On the street you might be ok but on the track is a different story.

[db12]

Not usually something you want to mess with, if you had a failure it could be a big deal. On the street you might be ok but on the track is a different story.

Im shocked by how many guys at the track run tires not xl rated. Hence me wondering if I should make the switch as well

[JD S4]

Not usually something you want to mess with, if you had a failure it could be a big deal. On the street you might be ok but on the track is a different story.

lol.. so you can crash into innocent people..


just buy the right tires.

[jprice]

Most people have lack of understanding what load rating is, and how to calculate the minimum load index you should get. So take all replies with a grain of salt. ;)

[ebarberena]

Taking only load rating into account, you do not need XL tires on a S4 B8. You do need at least a 89 load index tire.

An S4 B8 can weight up to 2,300kg loaded (1800 kg for the car, 400kg for 5 x 80kg passengers, 100kg for 4 x 25kg language) or 575kg/tire (with the car loaded this way I would estimate a 50/50 weight distribution).

So we need tires with at least 89 load index (580kg). Most tires that fit our cars have a load index of 92 (630kg) or higher.

As reference, my OEM tires were 245/40-18 93Y

That said, a lot of people believe (me included, but I don't have any facts to prove this belief) that sidewall stiffness is related to (but not only determined by) load rating. The higher the load rating, the higher the sidewall stiffness for a given tire design/size/aspect ratio.

Here is a little info about XL nomenclature on tires http://blog.tirerack.com/blog/bens-b...s-xl-stand-for . You can also look up your GAWR (my car is none US spec so I don’t have GAWR on my door placard) to double check.

By the way, 1kg=2.2lb.

[Spenceratc7]

Just a personal story that will back up everyone else here. I went to a local shop down here and threw on 20's for my S4, and with my ignorance and lack of knowledge in this area
I had tires put on with them that were quite a bit under the Load specifications (and the shop did take a bit advantage of me by only making sure there was no rubbing) Needless to say I am lucky that nothing serious happened, but after 4,000 miles of daily driving I had the metal sheet coming through the tire. I am very lucky I did not have a serious problem. If safety doesn't concern you then financially you will throw your money away elsewhere. Tires will have to be replaced more frequently. It will have a major impact on all of your suspension components, not to mention the quality and performance of your ride will be greatly diminished.

[JohnEnglish]

I'll never get people who buy "nice" cars and then try to cut corners in maintaining them.

[wt219200]

I'll never get people who buy "nice" cars and then try to cut corners in maintaining them.

Yeah because wasting money on something that isn't necessary is definitely the way to go..

I don't read this as trying to cut corners just making sure they're not wasting money.

[jprice]

Just a personal story that will back up everyone else here. I went to a local shop down here and threw on 20's for my S4, and with my ignorance and lack of knowledge in this area
I had tires put on with them that were quite a bit under the Load specifications (and the shop did take a bit advantage of me by only making sure there was no rubbing) Needless to say I am lucky that nothing serious happened, but after 4,000 miles of daily driving I had the metal sheet coming through the tire. I am very lucky I did not have a serious problem. If safety doesn't concern you then financially you will throw your money away elsewhere. Tires will have to be replaced more frequently. It will have a major impact on all of your suspension components, not to mention the quality and performance of your ride will be greatly diminished.

Ok. What was the load index of the tires you got, and what load index is required for our cars? Do you know the load index was too low? Are you sure that's the reason for the tire wearing out so quickly?

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Taking only load rating into account, you do not need XL tires on a S4 B8. You do need at least a 89 load index tire.

An S4 B8 can weight up to 2,300kg loaded (1800 kg for the car, 400kg for 5 x 80kg passengers, 100kg for 4 x 25kg language) or 575kg/tire (with the car loaded this way I would estimate a 50/50 weight distribution).

So we need tires with at least 89 load index (580kg). Most tires that fit our cars have a load index of 92 (630kg) or higher.

As reference, my OEM tires were 245/40-18 93Y

That said, a lot of people believe (me included, but I don't have any facts to prove this belief) that sidewall stiffness is related to (but not only determined by) load rating. The higher the load rating, the higher the sidewall stiffness for a given tire design/size/aspect ratio.

Here is a little info about XL nomenclature on tires http://blog.tirerack.com/blog/bens-b...s-xl-stand-for . You can also look up your GAWR (my car is none US spec so I don’t have GAWR on my door placard) to double check.

By the way, 1kg=2.2lb.

Finally someone replied with some good info :)

[JohnEnglish]

Yeah because wasting money on something that isn't necessary is definitely the way to go..

I don't read this as trying to cut corners just making sure they're not wasting money.

When the manufacturer recommends something (especially something as important as tires) meet a certain specification, trying to save money by buying products that don't meet that specification generally isn't a good idea. If they want to save money, maybe don't go to the track as often.

[jprice]

When the manufacturer recommends something (especially something as important as tires) meet a certain specification, trying to save money by buying products that don't meet that specification generally isn't a good idea. If they want to save money, maybe don't go to the track as often.

Do you know what the manufacturer recommended minimum load index is?

[JohnEnglish]

Yup and it doesn't change what Audi recommends; especially considering on a track where the vehicle weight is going to shifting from tire to tire.

[onlyaudis]

"Finally someone replied with some good info "


Or not. stick to what the manufacturer recommended --they do actually test these things you know. I personally know people who have catastrophically overloaded under rated tries during emergency maneuvers. just becasue someone sometimes gets away with doing something potentially dangerous doesn't make it the hot set up.

[db12]

I'll never get people who buy "nice" cars and then try to cut corners in maintaining them.

Nothing to do with cutting corners. I buy the tires solely as dedicated track tires. The Michelin's I have been using have not been holding up and others who track their s4's regularly are using other brands not xl rated. Hence my post. If I can find another tire brand the performs as well or better (while maintaining safety) there is no sense in over spending.

[jjprices]

Yup and it doesn't change what Audi recommends; especially considering on a track where the vehicle weight is going to shifting from tire to tire.

So what's the minimum tire load indeed recommended by Audi for the B8 S4? If you know what it is, please share.

[jjprices]

"Finally someone replied with some good info "


Or not. stick to what the manufacturer recommended --they do actually test these things you know. I personally know people who have catastrophically overloaded under rated tries during emergency maneuvers. just becasue someone sometimes gets away with doing something potentially dangerous doesn't make it the hot set up.

I feel like people don't understand load index. It's based on vehicle gvwr. Why would Audi have a recommended minimum load index, when by simply producing a vehicle of a certain weight dictates the minimum load index?

So what is the minimum load index Audi recommends for the B8 S4? Do you actually know?

[JohnEnglish]

So what's the minimum tire load indeed recommended by Audi for the B8 S4? If you know what it is, please share.

Why knowing or not knowing the precise number matter other than showing you can memorize numbers? That is why Audi provides us with a minimum load rating so consumers don't need to worry about doing the math every time they buy tires. You buy tires that meet the vehicle's design specifications.

[jprice]

Why knowing or not knowing the precise number matter other than showing you can memorize numbers? That is why Audi provides us with a minimum load rating so consumers don't need to worry about doing the math every time they buy tires. You buy tires that meet the vehicle's design specifications.

I'm not sure how I can ask this differently. What is the minimum load rating Audi provided us? It's being referred to a lot, and I don't think anyone knows what they're referring to.

[Chris@EPL]

4938 for a B8.5 S5 from the door.

[JohnEnglish]

I'm not sure how I can ask this differently. What is the minimum load rating Audi provided us? It's being referred to a lot, and I don't think anyone knows what they're referring to.

Right and my question is the same. What does knowing what it is prove?

[theweebabyseamus]

I'm not sure how I can ask this differently. What is the minimum load rating Audi provided us? It's being referred to a lot, and I don't think anyone knows what they're referring to.

96

[jprice]

Right and my question is the same. What does knowing what it is prove?

Not sure if you're purposefully being obtuse??

How can someone make sure they're buying a tire load index high enough if they don't know what the requirement is? If Audi has given us a specific recommendation, what is it? If you were buying a tire for a B8, what is the load index that you're going to make sure you're at or above?

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4938 for a B8.5 S5 from the door.

At least this guy gets that it's based on the GVWR :D

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96

Awesome.. thanks! :) Where did you get that number from?

[JohnEnglish]

Not sure if you're purposefully being obtuse??

How can someone make sure they're buying a tire load index high enough if they don't know what the requirement is? If Audi has given us a specific recommendation, what is it? If you were buying a tire for a B8, what is the load index that you're going to make sure you're at or above?

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At least this guy gets that it's based on the GVWR :D

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Awesome.. thanks! :) Where did you get that number from?

The point is if you use a place like tirerack or whatever, you don't need to worry about that. Once you specify your vehicle tires meet the requirement are shown to you. Sure us enthusiasts love to know all the minutiae of our vehicles but for the average person it's not necessary.

[jprice]

The point is if you use a place like tirerack or whatever, you don't need to worry about that. Once you specify your vehicle tires meet the requirement are shown to you. Sure us enthusiasts love to know all the minutiae of our vehicles but for the average person it's not necessary.

So to summarize, you have no idea what the minimum load index is, but just trust the tire shop to know for you. That's fine.. just trying to get to the bottom of this "Audi Recommended" load index that people keep talking about. If there is one, it has a specific value.

[db12]

Well LOL, I answered my own post. After seeing all the debate from my original question I downloaded the Audi manual. Turns out there are "2 Load Ratings" for the S4

If you running 18's = 93 Load index (speed ratings vary based on type of tire h or y etc)

If you running 19's = XL load index (speed rating y)

I run 18's at the track so guess Im good to go.

[JohnEnglish]

It's almost like the Audi engineers who designed the car know what's best for it.

[jprice]

Well LOL, I answered my own post. After seeing all the debate from my original question I downloaded the Audi manual. Turns out there are "2 Load Ratings" for the S4

If you running 18's = 93 Load index (speed ratings vary based on type of tire h or y etc)

If you running 19's = XL load index (speed rating y)

I run 18's at the track so guess Im good to go.

Good job! :) Glad you went to the source instead glazing over the topic like most do. Now you know an actual number. :D

[jprice]

It's almost like the Audi engineers who designed the car know what's best for it.

You mean it's like they know the gross vehicle weight at each corner and know how to reference a load index chart? ;)

[JohnEnglish]

Well I'd assume it'd be dome in their modelling program but yeah.

[switchedstance]

Have put 15k miles and counting on a set of 255/35/19 PSS 92Y (non-XL) in NYC including 2 autox days and tons of spirited driving with no issues. 92y = 1389lbs per tire, total load of 5556lbs. Thats 600lbs over our GVWR, I rarely load my car or have more than 1 passenger, so it has been a non-issue for me. I understand I'm running tires below the manufacturer's specs, but I'd argue tire stretching is way more dangerous.

[jprice]

Have put 15k miles and counting on a set of PSS 92Y (non-XL) in NYC including 2 autox days and tons of spirited driving with no issues. 92y = 1389lbs per tire, total load of 5556lbs. Thats 600lbs over our GVWR, I rarely load my car or have more than 1 passenger, so it has been a non-issue for me. I understand I'm running tires below the manufacturer's specs, but I'd argue tire stretching is way more dangerous.

You don't auto-x with 4 passengers and your trunk filled up as much as possible with heavy luggage? Huh. ;)

Glad to see someone else who understand what gvwr and load index is :) Props.

[switchedstance]

You don't auto-x with 4 passengers and your trunk filled up as much as possible with heavy luggage? Huh. ;)

My competitors probably wish I did. These s4's own stock class.

[karlaudi]

Moving away from load rating calculations and toward the OP's question about cheaper track tires - I too went through a couple sets of sport cup 2's and have now tried out a 'budget' track tire, federal 595 rs-rr in a 255/35/19 (96W XL) and they held up great for the first event, very even wear.
They don't stick as well as the sport cups, but are pretty darn good for a 200 treadwear tire (just behind the rs71) and are $160 a pop.


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[db12]

Moving away from load rating calculations and toward the OP's question about cheaper track tires - I too went through a couple sets of sport cup 2's and have now tried out a 'budget' track tire, federal 595 rs-rr in a 255/35/19 (96W XL) and they held up great for the first event, very even wear.
They don't stick as well as the sport cups, but are pretty darn good for a 200 treadwear tire (just behind the rs71) and are $160 a pop.


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Might give the Nitto NT01's a try as they seem to have a good rep

[karlaudi]

Might give the Nitto NT01's a try as they seem to have a good rep

Nittos are great. My only problem is tire size, I run a 19" rim to get around 380 stoptechs and I've only found a 235 or 285 in 19".


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