the link is to the thread this is from...

The tire lists 44 cold as max inflation. Thats the only figure I have, and I dont have any direct communique from an Audi or Dunlop or BBS engineer telling me a different set of inflation numbers and that I shouldn't ignore them.

What kills me is that you assume (because you DO have a substantial amount of car-based knowledge) that you know what is right for my PREFERENCE and car set-up. But I have plenty of knowledge as well and what you left out is that I have played with all sorts of air pressure combos to find what is the right ride comfort/firmness/wear pattern/rollover avoidance and turn in that is good for me and my particular car/set-up. Your statement is similar to me saying "don't put a chip in your car because you may shorten the theoretical life of the engine yada yada yada" assuming that you haven't taken performance vs. longetivity into question.

It used to amaze me when people knew it all on the internet - but I've mellowed as well.

Oh yeah - so what the reccomended pressure for an 225/40/18 via Audi?? Its not on my gas cap sticker...maybe its on yours.<ul><li><a href="https://forums.audiworld.com/tt/msgs/409530.phtml">https://forums.audiworld.com/tt/msgs/409530.phtml</a</li></ul>

 

I'm running Pilot Sports 225/40/18's. 38/35 for xtreme canyon driving and 40/35 for track driving. Front tires lose a little compliance at 40 and are harsher but when the car is pushed to maximum they wear better and traction is excellent. For normal street cruising I could run 36/33 as a minimum setup for comfort.

The rears don't work very hard. I started them when new at 35, and they seem to work well in both situations above. Gum up nicely and wear pattern is good. Balance of the car drifting sliding is great and has not upset the neutral nature of the car. Mind you this is not a daily driver. I set it up for hard and sustained cornering and not cruising. It is harsher so lowering a few lbs. from the above should give a compliant and comfortable good all around ride. Eddie at Tire Rack thought best to start the 18's a couple of lbs. higher than the 17's for reference sake.

I've also run a Streets of Willow which is hard turns for 1.7 miles in the desert. Rough on tires because you are pushing/sliding the car a fair amount on street tires. Temps of my tire set at 38 cold were 48lbs when hot checked, right off the track. Sidewalls were getting scuffed a bit much. A couple of pounds more in the fronts helped and keeps the pressure/temp. from increasing too much when hot.

Remember these are 18's and Michelin's recs. are 36/33 from their website if I remember correctly.

Finally as far as wear....I rotated my tires before Sears and after Willow and they are wearing perfectly...no premature center wear. Realize though that every tire is unique and requires different pressures for the compounds it uses and it's construction. Use the Tire Manufacturer recs. first for the particular car and adjust to suit.

 

happy with 34F and 32R. This seems to work fine on my 180 Quattro for spirited street driving. John has more input and experience on a track setup. Found the 34/32 setup seems to work very well in the wet or rainy conditions for me. If it is hot I'll sometimes move the fronts up to 36 on the street. The rears seem to be happy staying at 32. From what I can tell the ride is the same as the stock 17's that I ran at 34F and 34R.

 

From TireRack:

"Maximum Inflation Pressure

A tire's maximum inflation pressure is the highest "cold" inflation pressure that the tire is designed to contain. However the tire's maximum inflation pressure should only be used when called for on the vehicle's tire placard or in the vehicle's owners manual. It is also important to remember that the vehicle's recommended tire inflation pressure is always to be measured and set when the tire is "cold". Cold conditions are defined as early in the morning before the day's ambient temperature, sun's radiant heat or the heat generated while driving have caused the tire pressure to temporarily increase.

For the reasons indicated above, It is also normal to experience "hot" tire pressures that are up to 5 to 6 psi above the tire's recommended "cold" pressure during the day if the vehicle is parked in the sun or has been extensively driven. Therefore, if the vehicle's recommended "cold" inflation pressures correspond with the tire's maximum inflation pressure, it will often appear that too much tire pressure is present. However, this extra "hot" tire pressure is temporary and should NOT be bled off to return the tire pressure to within the maximum inflation pressure value branded on the tire. If the "cold" tire pressure was correctly set initially, the temporary "hot" tire pressure will have returned to the tire's maximum inflation pressure when next measured in "cold" conditions.

A tire's "maximum inflation pressure" may be different that the assigned tire pressure used to rate the tire's "maximum load". For example, while a P-metric sized standard load tire's maximum load is rated at 35 psi, many P-metric sized standard load performance and touring tires are designed to contain up to 44 psi (and are branded on their sidewalls accordingly). This additional range of inflation pressure (in this case, between 36 and 44 psi) has been provided to accommodate any unique handling, high speed and/or rolling resistance requirements determined by the tire and vehicle manufacturers. These unique tire pressures will be identified on the vehicle placard in the vehicle's owner's manual.

The tire's maximum inflation pressure is indicated in relatively small-sized print branded near the tire's bead (adjacent to the wheel) indicating the appropriate value. Because tires are global products, their maximum inflation pressure is branded on the tire in kilopascals (kPa) and pounds per square inch (psi). These values can also be found in the industry's tire load & inflation charts."

TireRack's Tire Owner's Manual pg. 10-11 is also good. You can download from the link. Highly recommended.

FWIW: "As I said, an individual can do as he/she sees fit, and what I say won't change your mind. I just caution others that there are good reasons for sticking near the pressures recommended by the manufacturer."

I'm not trying to tell you what is right for you, just presenting some information that's generally available.

If you called or wrote to Audi for inflation recommendations for a 225/40-18 on a TT, they very probably would advise against using that size tire. That doesn't help, I know, but just changing the size from 225/45-17 to 225/40-18 doesn't change the recommended pressures much, if at all. Maybe adding 3 psi to the 33/30 like Audi does for full load would be a good start. Remember, however, that the original B/S RE040 and the P6000 in the OEM 225/45-17 TT size have MAX inflation presures of 51 psi, not 44 psi. per the 'Specs' section of TireRack.

Hey, all else being equal, overinflated is probably safer than underinflated.<ul><li><a href="http://www.tirerack.com/images/tr_ownersmanual.pdf">http://www.tirerack.com/images/tr_ownersmanual.pdf</a</li></ul>

 

I was running 38 all around to balance things out despite professional advice. ;-)

 

and no auto maker numbers - I am left to find an inflation pressure that is good for my car. I am running 40 up front - not the max of 44 and 38 in rear not the max of 44. Also - my gas cap changes the pressures upwards of 3 psi from 16 to 17 - going to 18 and adding 3 gets me to 39 front...maybe thats not what they would recommend - but they do sell 18's on the TT as a dealer installed option and on the S-line - so I'm curious if they do have a rec. spec. But then again its a rec. only...

bottom line its fine and rides/wears great

 

Change your fronts to 40 and live on the dark side...

 

I'm running the stock 17's now. 40 all around.

 

Going up 2 lbs front and rear for the change from 17's to 18's as a STARTING point. Tune from there for your best feel/suspension combo.....

 

O/T nice sig man!