Tire load capacity and load ratings

[Luke@tirerack]

The Facts:

A P-Metric tires max load is achieved at 35 psi and a Euro metric tires max load is achieved at 36 psi adding more air pressure will not increase the tires load capacity but, lowering it will reduce the load carrying ablility. When increasing pressure all you are accomplishing is a lower rolling resistance, quicker steering response, stiffer ride and contact patch reduction which in turn gives you more tread element squirm if the tires are new.

Based on a RS6:
the OE tire is a 255/40-18 99Y
max load capacity is 1709 lbs.
load capacity at recommended pressure (which we will call PLC for placard load capacity at 36psi) = 1709 lbs.

so the minimum load capacity for a RS6 is 1709 lbs. according to the PLC

now if you look at the optional tire "OK'd" by Audi
255/35-19 96y
max load is 1565
PLC = 1565

so in reality the minimum load capacity is 1565 lbs.

now lets consider the idea of running a capacity that is too low .... what happens:
the tire is put into a condition where it can support the car at a static rest point but, when driven aggressively the sidewalls are so over worked they can not properly control the contact patch of the tire allowing for excessive sidewall roll-over, irregular wear tread block and contact patch flex which robs the tires performance ability and grip. also the added flexing of the tire will increase the heat it generates which can make a tire feel really slippery. Also, the added heat can cause a tire to fail ....

A good way to understand this is: let's say I just put a 100lb. back pack on you .... you can stand there for quite a while (that's your car sitting in a parking lot) now go run up and down some stairs with that back pack .... that's normal driving and you can't do that very well, nearly as fast or for very long before your legs give out .... after you've recovered enough to walk (let the car rest once you arrive at the venue for your autoX or track day), take a 500 meter sprint through deep sand, that's your autoX and you will most likely not make it to the finish without falling atleast once if you can finish at all.

load capacity does matter

I hope this info helps !!!

[Erik]

Welcome to RS6.com! Tires are very important and we all like to know more!

Please study the forum rules: http://www.rs6.com/forum/showthread.php?s=&threadid=2505&highlight=rules Thanks!



Learning by doing... :)

http://www.rs6.com/forum/showthread.php?s=&threadid=4112&highlight=n%FCrburgring

http://www.rs6.com/forum/showthread.php?s=&threadid=3859&perpage=17&highlight=nürburgring&pagenumber=1

http://www.rs6.com/forum/attachment.php?s=&postid=25231

[MarkeRS6]

Luke,

Your post indicates no issue with the following setup on my RS6:

RS6 19x9 ET35s wheels with Goodyear Eagle F1 GS-D3 255/35/R19 96Ys installed

Recommended time pressure?

Thanks!

[Luke@tirerack]

Originally posted by Erik
Welcome to RS6.com! Tires are very important and we all like to know more!

Please study the forum rules: http://www.rs6.com/forum/showthread.php?s=&threadid=2505&highlight=rules Thanks!

why did I break any of them ... I was just trying to help out

[Luke@tirerack]

Originally posted by MarkeRS6
Luke,

Your post indicates no issue with the following setup on my RS6:

RS6 19x9 ET35s wheels with Goodyear Eagle F1 GS-D3 255/35/R19 96Ys installed

Recommended time pressure?

Thanks!


what's "time pressure" ?????


if you mean tire pressure well, that's based on vehicle weight and your car still weighs the same doesn't it ??? if so , go with 36 psi and if you want to run on a track raise the fronts to about 40 - 42

[gmbh6]

I like this thread...bump. :incar:

[GmbHouse]

Luke - Can we infer, by Audi's alternate tire recommendation, that running an 18 inch tire with a PLC of 1565 lbs is OK too? Or does the fact that the 19 inch tire has a shorter sidewall allow it to run a lower PLC compared to an 18 inch tire?

[Luke@tirerack]

infer away ......

here's basically the way it looks from the tire sizes through a my eyes

it's easier to look at the service descrition for this explanation

while Audi was looking for a 26" diameter tire with a 255 width to match the engineered suspension geometry (automotive engineers rarely think of the little things like tires in advance) they came upon the three tires with a 1709 load capacity even though they knew they only needed a 1565 load capacity but, all of the other 255/40-18 tires have a load capacity of 1521 or lower

so, yes 1565 is the lowest acceptable load capacity for a summer / performance tire ....

[eph94]

Are there any R compound tires that meet the extra load specs??

[avdh]

I don't want to start an argument with Luke who is supposed to be the the tyre Pro around here, however, 36 psi with 19' wheels is too low according to Audi.

They recommend 40 psi when using 255/35/19.

At the moment I have the Dunlop SP9000RS 255/35/19, which I am starting to really dislike and to get any sort of performance and and a bit of feedback through the steering, I use 43 or 44 psi (3.0 bar). That's the best (or rather the least worse) for this particular tyre.

Did anyone with SP9000's also found out that when cold they are quite slippery, more so as they wear out? and it is even worse at 40 psi than at 44 psi......

Luke, I have my eyes on the Michelin PS2 255/35/19, as a replacement.
Out of the 19' tyres you mentionned above, is the PS2 the one which will give me the best feedback on what the car is actually doing on the road?

In this department I loved the Bridgestone S-03's, however they are not available in the size I require.

As for the RE050 I understand it is a run flat. Isn't that tyre utterly uncomfortable?

[Bauer]

Did anyone with SP9000's also found out that when cold they are quite slippery, more so as they wear out? and it is even worse at 40 psi than at 44 psi......

I had them in the 18's and did not really like them. The would be fine for a mid level performance car but for the likes of the RS6 they are Inadequate. Mine were slippery when cold and when they heated up they were not that much better and when really pushed they would fall apart in chuncks. I had quarter sized pieces of rubber missing from them after on track event. I currently have SO2's (have not tracked) but I believe the sidewall strength is to low so I will not be taking them to the next track event. Probably end up with Pilot Sports or try the new PS2 and some have really liked the Rosso's. Not sure yet. One onther thing about the S02's, they are noisey as hell and they catch every grove but are very sticky.

Cheers,

[gregoryindiana]

I sent you a pm

[noushy]

Hello Andre,
I think we talked about the tires before but here goes again before I head to bed. I had the dunlops in 18 inch stock. I found them to be ok around town, but not great when they warmed up. In addition, they started to wear irregularly around the edges. Small pieces began to fall off. This is for a tire that was not abused, not tracked, and not raced at all. I drove it to work and back, occasionally at 90-110mph or so, but usually around 75mph to avoid the friendly constables. I now have the pirellis and I think they are much better tires. They are sharper to corner (although it is also a 19inch). They wear evenly, and ride quite nicely for a performance tire. I have heard the same thing form people with the pzero as stock tires in 18 inch. Go ahead and give them a try. I only have pixs that I took for the wheels (ricky and gnomik) but here is a fairly close shot.

Noushy

[Luke@tirerack]

Originally posted by avdh
I don't want to start an argument with Luke who is supposed to be the the tyre Pro around here, however, 36 psi with 19' wheels is too low according to Audi.

They recommend 40 psi when using 255/35/19.



true but you forgot this sentence from above

A P-Metric tires max load is achieved at 35 psi and a Euro metric tires max load is achieved at 36 psi adding more air pressure will not increase the tires load capacity



At the moment I have the Dunlop SP9000RS 255/35/19, which I am starting to really dislike and to get any sort of performance and and a bit of feedback through the steering, I use 43 or 44 psi (3.0 bar). That's the best (or rather the least worse) for this particular tyre.

Did anyone with SP9000's also found out that when cold they are quite slippery, more so as they wear out? and it is even worse at 40 psi than at 44 psi......

Luke, I have my eyes on the Michelin PS2 255/35/19, as a replacement.
Out of the 19' tyres you mentionned above, is the PS2 the one which will give me the best feedback on what the car is actually doing on the road?

In this department I loved the Bridgestone S-03's, however they are not available in the size I require.

you will love the PS2's then

As for the RE050 I understand it is a run flat. Isn't that tyre utterly uncomfortable?

it is available in both a runflat version and a non runflat version

[SpinEcho]

Originally posted by avdh
At the moment I have the Dunlop SP9000RS 255/35/19, which I am starting to really dislike

Andre, I agree. These were decent tires 5 or 6 years ago when they first came out, but the game has moved on. I am underwhelmed by the SP9K's on my RS6, just as I was underwhelmed with the set I had on my Corrado. I have yet to experience PZeros, but this will be my replacement tire for the Beast, based on what I've read.