Important Q7 tire information from Luke at the TireRack
03-31-2010, 09:48 AM
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Important Q7 tire information from Luke at the TireRack
I'm cross-posting this from the Wheel and Tire Forum on QuattroWorld (where I originally posted this) in the hopes that I can save somebody from having to learn the hard way like I did...
My original post:
"Background: Typically I am absolutely meticulous when it comes to monitoring my tire pressures and tire wear but when I had to give up my modded S4 for a stock Q7 I got a little lazy. This is a CPO 2007 Q7 3.6 with 20" wheels. I set the tire pressures according to the sticker on the door-jam (44psi front, 49psi rear) and just maintained them there. Ruined a brand new set of all-seasons and then a set of snows (all due to excessive wear in the center of the tire), and finally decided to do some research.
Turns out the sticker on the door jam lists the pressures to run for maximum load capacity and there's a table in the owner's manual explaining that the range of recommended tire pressures goes from 35-44psi for the front and 35-49psi for the rear, depending on load. Well, 95% of the time I have 1-3 passengers with no baggage or anything for which the manual recommends 35psi for both front and rear, yet I was running 44/49. I was never really happy with the feel of the handling of the vehicle nor the snow traction I was getting, but knowing that I was at the manufacturer's recommended tire pressures I chalked it up to oversensitivity on my part in going from the S4 (with coilovers, etc) to the Q7.
Anyway, I've brought my tire pressures down to 38psi all around right now and that feels pretty good. But I still need new tires, so was doing some research on the TireRack website and I come across a note that says: 'Important Notes: This size requires XL/RF tires. It also requires tire pressure levels of 42psi for proper load.'
I knew about the XL load rating and would only use tires with that rating, but I'm confused about the 42psi recommendation since the manual says 35psi is fine for light load. I realize I'm running non-OEM tires, but the TireRack warning was for all 20" tires, near as I could tell.
QUESTION: Can you give me any input on tire pressures for 20" tires on the Q7?"
And here is the reply from Luke at the TireRack:
"Why would Audi have a door placard listing 44/49 psi? Well it's a combination of things...
The Transportation Recall Enhancement, Accountability and Documentation (or TREAD) Act is a United States federal law enacted in the fall of 2000. This law intends to increase consumer safety through mandates assigned to the National Highway Traffic Safety Administration (NHTSA). It was drafted in response to fatalities related to Ford Explorers fitted with Firestone tires, and was influenced by automobile and tire manufacturers as well as consumer safety advocates. After congressional hearings were held in September 2000, Congress in only an 18 hour span passed the TREAD Act in October 2000. The Act was signed into law by President Clinton on November 1, 2000, and has been incorporated into the existing National Traffic and Motor Vehicle Safety Act of 1966.
One of the provisions eliminates multiple pressure recommendations on vehicle placards which were previously listed based on usage.
In order to comply with that provision vehicle manufacturers started just putting the recommended pressure for the most extreme use the vehicle may see. In your case this would be; fully loaded with people and stuff running at extreme high speeds.
Now think about where your Q7 was born ... why? you ask ... it's Germany and they have the Autobahn ... The Autobahn's unlimited speed opportunities explain why many German vehicles identify alternate tire inflation pressures, which used to be on the placard but are now found in the owners manual,to accommodate higher than North American highway speeds and heavier than typical two-passenger loads.
Driving at high speeds the tires will be subjected to tremendous stresses. Then add in the weight on the tires, which will cause the sidewalls to bulge and the tread to flatten as they roll into contact with the road. This results in dimensional difference between the tire's "unloaded" radius (i.e., between the center of the axle and the top of the tire) and its "loaded" radius (between the center of the axle and the road). The engineer's call the difference between the two radii "deflection." Increasing vehicle speed will cause the tires to deflect quicker and increasing vehicle load will cause the tires to deflect farther (if tire pressure isn't increased).
The European Tyre and Rim Technical Organization (ETRTO) establishes the standards for tires sold in Europe, and recognizes that the tire's deflection must be minimized and controlled in order to surpass high speed driving stresses. In order to accomplish this, the tire inflation pressure recommendations and the tire's rated load capacities are customized when speeds exceed 160 km/h (99 mph) for all tires up to and including a V-speed rating, and when speeds exceed 190 km/h (118 mph) for all tires that are Z-speed rated and above.
All of that said I would be running about 36 psi if it was my Q7.
As far as the "load" requirement warning ... it's legal speak to let you know that if your Q7 fully loaded and you will be running at high speed you need to increase the tire pressure."
Original thread at QuattroWorld:
http://forums.quattroworld.com/wheel/msgs/2106.phtml
My original post:
"Background: Typically I am absolutely meticulous when it comes to monitoring my tire pressures and tire wear but when I had to give up my modded S4 for a stock Q7 I got a little lazy. This is a CPO 2007 Q7 3.6 with 20" wheels. I set the tire pressures according to the sticker on the door-jam (44psi front, 49psi rear) and just maintained them there. Ruined a brand new set of all-seasons and then a set of snows (all due to excessive wear in the center of the tire), and finally decided to do some research.
Turns out the sticker on the door jam lists the pressures to run for maximum load capacity and there's a table in the owner's manual explaining that the range of recommended tire pressures goes from 35-44psi for the front and 35-49psi for the rear, depending on load. Well, 95% of the time I have 1-3 passengers with no baggage or anything for which the manual recommends 35psi for both front and rear, yet I was running 44/49. I was never really happy with the feel of the handling of the vehicle nor the snow traction I was getting, but knowing that I was at the manufacturer's recommended tire pressures I chalked it up to oversensitivity on my part in going from the S4 (with coilovers, etc) to the Q7.
Anyway, I've brought my tire pressures down to 38psi all around right now and that feels pretty good. But I still need new tires, so was doing some research on the TireRack website and I come across a note that says: 'Important Notes: This size requires XL/RF tires. It also requires tire pressure levels of 42psi for proper load.'
I knew about the XL load rating and would only use tires with that rating, but I'm confused about the 42psi recommendation since the manual says 35psi is fine for light load. I realize I'm running non-OEM tires, but the TireRack warning was for all 20" tires, near as I could tell.
QUESTION: Can you give me any input on tire pressures for 20" tires on the Q7?"
And here is the reply from Luke at the TireRack:
"Why would Audi have a door placard listing 44/49 psi? Well it's a combination of things...
The Transportation Recall Enhancement, Accountability and Documentation (or TREAD) Act is a United States federal law enacted in the fall of 2000. This law intends to increase consumer safety through mandates assigned to the National Highway Traffic Safety Administration (NHTSA). It was drafted in response to fatalities related to Ford Explorers fitted with Firestone tires, and was influenced by automobile and tire manufacturers as well as consumer safety advocates. After congressional hearings were held in September 2000, Congress in only an 18 hour span passed the TREAD Act in October 2000. The Act was signed into law by President Clinton on November 1, 2000, and has been incorporated into the existing National Traffic and Motor Vehicle Safety Act of 1966.
One of the provisions eliminates multiple pressure recommendations on vehicle placards which were previously listed based on usage.
In order to comply with that provision vehicle manufacturers started just putting the recommended pressure for the most extreme use the vehicle may see. In your case this would be; fully loaded with people and stuff running at extreme high speeds.
Now think about where your Q7 was born ... why? you ask ... it's Germany and they have the Autobahn ... The Autobahn's unlimited speed opportunities explain why many German vehicles identify alternate tire inflation pressures, which used to be on the placard but are now found in the owners manual,to accommodate higher than North American highway speeds and heavier than typical two-passenger loads.
Driving at high speeds the tires will be subjected to tremendous stresses. Then add in the weight on the tires, which will cause the sidewalls to bulge and the tread to flatten as they roll into contact with the road. This results in dimensional difference between the tire's "unloaded" radius (i.e., between the center of the axle and the top of the tire) and its "loaded" radius (between the center of the axle and the road). The engineer's call the difference between the two radii "deflection." Increasing vehicle speed will cause the tires to deflect quicker and increasing vehicle load will cause the tires to deflect farther (if tire pressure isn't increased).
The European Tyre and Rim Technical Organization (ETRTO) establishes the standards for tires sold in Europe, and recognizes that the tire's deflection must be minimized and controlled in order to surpass high speed driving stresses. In order to accomplish this, the tire inflation pressure recommendations and the tire's rated load capacities are customized when speeds exceed 160 km/h (99 mph) for all tires up to and including a V-speed rating, and when speeds exceed 190 km/h (118 mph) for all tires that are Z-speed rated and above.
All of that said I would be running about 36 psi if it was my Q7.
As far as the "load" requirement warning ... it's legal speak to let you know that if your Q7 fully loaded and you will be running at high speed you need to increase the tire pressure."
Original thread at QuattroWorld:
http://forums.quattroworld.com/wheel/msgs/2106.phtml
03-31-2010, 10:14 AM
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Interesting. I had figured that out a while back, but it is most definitely confusing. That said, I am still getting only about 18k out of my OEM Conti's. I could probably stretch it to 20-22k, but with tires, I tend to err on the side of caution - I don't run them much after the wear tabs start to just about plane out with the tread. The Conti's perform OK, but the tread life is pretty lame. I attribute it to the heavy weight of the Q7 (I have a 4.2). The fronts really wear out fast. (So do the brake pads).
What tires did you end up getting from TireRack? Unfortunately, I'm due again.
What tires did you end up getting from TireRack? Unfortunately, I'm due again.
03-31-2010, 10:37 AM
#3
On my 20's the Q7 came with Goodyear Eagle F1 (dealer error as I asked for all seasons). I got about 25,000 km on them running at -10% from max pressure (41 psi / 3.1 bar I think).
I replaced them with Hankook Ventus R6 and I am REALLY impressed. The car has done another 25,000 km on those and they are just half worn! I'll get at least 50,000 km form them at this rate.
I drive easy (100-120 kmh highway and stick to the limits on all other roads too - police over here are draconic now) so I guess that accounts for a good part of the mileage, but the Hankooks have WAY WAY more lifespan than the Goodyears. They are also quiet and have good all weather grip.
Also note the prices:
Goodyear Eagle F1 x 4 = 1200 Euro (last 25,000 km)
Hankook Ventus x 4 = 540 Euro (last at least 50,000 km).
Wild horses would not drag me back to Goodyear.
I replaced them with Hankook Ventus R6 and I am REALLY impressed. The car has done another 25,000 km on those and they are just half worn! I'll get at least 50,000 km form them at this rate.
I drive easy (100-120 kmh highway and stick to the limits on all other roads too - police over here are draconic now) so I guess that accounts for a good part of the mileage, but the Hankooks have WAY WAY more lifespan than the Goodyears. They are also quiet and have good all weather grip.
Also note the prices:
Goodyear Eagle F1 x 4 = 1200 Euro (last 25,000 km)
Hankook Ventus x 4 = 540 Euro (last at least 50,000 km).
Wild horses would not drag me back to Goodyear.
03-31-2010, 05:42 PM
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I haven't tried them in the winter though because I prefer to run dedicated winter tires. At the time, Pirelli Scorpion Ice and Snow were about the only winter tires available in 20" so I used those. They were good but they are very expensive. Now that I need a new set of winter tires, I am thinking of switching to Bridgestone Blizzak DM-V1. They're only R-rated for speed, but I never take the Q7 near 100mph (let alone 106mph which is the limit for that rating) and I'd like to try out the special multicell compound these use to see how much better traction they offer. And, they're much cheaper than the Pirelli snow tires.
03-31-2010, 05:46 PM
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I don't honestly know how much below the set point the pressure has to go before the warning pops up. I did have the warning go off once but that was due to a tire that had a nail and was going flat; so in that case the system worked well, but I don't know what the pressure was at the time.
04-02-2010, 04:57 AM
#7
Good info here, will have to look at ratings now. Running Parada Spec X also in size 295/45/20. Been messing with different pressures but not sure what to run. No vehicles I have had in the last 20 years have had the OEM tire size, and there isnt a definitive guide on PSI when switching to diff sizes. Techs at Tire Rack have been extrememly knowledgable.
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04-05-2010, 06:52 PM
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My understanding is that there is a minimum tread depth in mm that's just BARELY above the wear bars and that's what two out of the four tires on my CPO were when I bought it. In fact, I pointed out the worn tires to the sales guy and he pulled out the official CPO inspection that listed the tread depth they measured on all four tires, and he admitted they were at the absolute minimum that they could sell the car with.
