2014 Q5 - humming noise at 60+MPH
09-22-2013, 04:33 PM
#22
AudiWorld Member
Thread Starter
Half joking, but half not. We know the ride height change was gutted to conform it as a light truck for US stds. We also know from the parts listings there is no roll bar or similar tweak. From some recent posts the air pressure difference came up, but not for any obvious good reason on an SQ like weight/load. If you want to challenge the weight issue as any rationale BTW, realize either the TDI or the Hybrid are heavier. But those Q5 versions don't have the tires pumped up when fit w/ 20's of the identical size. Seems like they spec'ed the air pressure either as a mistake or some goofy way to try to stiffen up ride and maybe steering feel.
As it were, seems like the air has been kind of let out of the sport tuned suspension hawked by Audi USA marketing, and now literally so given it seems to generate excessive noise.
As it were, seems like the air has been kind of let out of the sport tuned suspension hawked by Audi USA marketing, and now literally so given it seems to generate excessive noise.
Did some digging for UK-spec SQ5 TDI recommended tire (tyre) pressures. Found data here (if readers have UK-spec data from their owners manual, please reply): http://www.rezulteo-tyres.co.uk/tyre.../3.0-bitdi-313 Of course, the UK-spec SQ5 has a different suspension setup than the US model.
2.3 bars for the front (~33PSI) and 2.0 bars rear (29PSI) - nowhere near the 40PSI they are recommending for US-spec SQ5's.
In the meantime, I'm going to give it a go running the tires at 31PSI (average of the recommended pressures in the manual for the 20" tires on the S-Line Q5's) vs. the recommended 40 for the SQ5 and get on with the enjoyment of my SQ5.
Thanks to everyone for their advice and suggestions. It'll be interesting if more reports of this crop up as time goes on.
Last edited by TonySCV; 09-22-2013 at 04:41 PM.
09-22-2013, 08:45 PM
#23
AudiWorld Super User
Old info that might help on U.S. tire pressure oddities
First, notice the tire pressure sticker on the driver's door pillar. On Audi's commonly still on the road (through 2006 and maybe even early 2007's built in 2006) they tend to be either on the fuel filler door or on the passenger side rear door/fender area if the tank lid was already stickered up. But, the Ford Explorer rollover fiasco changed all that.
As of 2007, the U.S. sticker became mandated, in all of location, content and even color--hence the white background (Audi used silver normally), and the black, red and yellow colors, all painfully spelled out in regulatory legalese. The stickers now also have to be specific for what is fit to the vehicle, as BMW/Mini found in an embarrassing low volume "they couldn't even get the sticker right" recall. TPMS systems also got mandated too, with a more gradual phase in IIRC. Along the way those kind of got dumbed down by the cheaper current ABS overlapping systems that originally seemed dubious about whether they were as good in scenarios with quick pressure drops or where all the tires were actually simultaneously low.
Shortly after this stickering change happened, I remember in parallel a post on an obscure VW forum dealing with the Phaeton (or Passat W8??). I was only was looking at it as a vague cousin to my Audi A8 W12. The guys on the board were posting about tire pressures, where an argument suddenly broke out along the lines of, "you idiot, read the sticker." Well guess what, on the identical car with the identical motor, the identical wheels and the identical tire sizing, the U.S. vs. European stickers owned by various respective posters (where the internet knows no easy boundaries) were indeed different in what they recommended. In particular, the European ones had lower (and rational) pressures for the given tire/aspect ratio, while the U.S. ones seemed high. The European specs typically have a range too, while the U.S. ones have a specific number. The owner's manuals have more leeway, and as you can see in this thread, the manual states a range. I haven't read it first person in the regs or anything, but I think the sticker has to show the pressure capable of taking the maximum load--a classic problem from the Explorer fiasco where Ford ended up with low pressures on the sticker for ride plushness, but it was way short of the mark at fully loaded. And that was exacerbated by a high center of gravity and way big sidewall aspect ratios on fairly small wheels. These are not mistakes the stereotypical German ultra spec design think would usually make, especially when coupled with everything has to be rated for the max speed the vehicle can go given the Autobahn scenarios.
Net, if I want to use the pressures the factory designers and engineers thought were really best, I would use the Euro ones on my own vehicle as the guideline. And, that's backed up for my own comfort that as the people who know the vehicle better than anyone, they have concluded their Euro advice checks out on the Autobahn at 130mph (or 155 for some performance Audis). That's a big delta from the U.S. even with Arizona type desert extremes, and actually even more so in low speed limit and dense population Japan. If I wanted to go with the safety nannies and lowest common denominator belt, suspenders, duct and red tape, the U.S. ones are my ticket to ride. And BTW, since they do have this pretty unexplainable mismatch between the Q5 in a variety of motor flavors and weights with an identical wheel and tire fitment to the SQ5 (255/45-20's), it would not surprise me given the prior Mini ding (which happened as between S's and JCW's and wrong diameter wheels actually on the car IIRC) if Audi eventually gets the dubious honor of another "they couldn't get the sticker right" recall as Mini did. Here though, since the tire pressures are arguably meaningfully high, it may still pass the Ford Explorer fiasco remedy low water mark of sticker cures, since way low pressures were an Explorer Achilles heel.
As of 2007, the U.S. sticker became mandated, in all of location, content and even color--hence the white background (Audi used silver normally), and the black, red and yellow colors, all painfully spelled out in regulatory legalese. The stickers now also have to be specific for what is fit to the vehicle, as BMW/Mini found in an embarrassing low volume "they couldn't even get the sticker right" recall. TPMS systems also got mandated too, with a more gradual phase in IIRC. Along the way those kind of got dumbed down by the cheaper current ABS overlapping systems that originally seemed dubious about whether they were as good in scenarios with quick pressure drops or where all the tires were actually simultaneously low.
Shortly after this stickering change happened, I remember in parallel a post on an obscure VW forum dealing with the Phaeton (or Passat W8??). I was only was looking at it as a vague cousin to my Audi A8 W12. The guys on the board were posting about tire pressures, where an argument suddenly broke out along the lines of, "you idiot, read the sticker." Well guess what, on the identical car with the identical motor, the identical wheels and the identical tire sizing, the U.S. vs. European stickers owned by various respective posters (where the internet knows no easy boundaries) were indeed different in what they recommended. In particular, the European ones had lower (and rational) pressures for the given tire/aspect ratio, while the U.S. ones seemed high. The European specs typically have a range too, while the U.S. ones have a specific number. The owner's manuals have more leeway, and as you can see in this thread, the manual states a range. I haven't read it first person in the regs or anything, but I think the sticker has to show the pressure capable of taking the maximum load--a classic problem from the Explorer fiasco where Ford ended up with low pressures on the sticker for ride plushness, but it was way short of the mark at fully loaded. And that was exacerbated by a high center of gravity and way big sidewall aspect ratios on fairly small wheels. These are not mistakes the stereotypical German ultra spec design think would usually make, especially when coupled with everything has to be rated for the max speed the vehicle can go given the Autobahn scenarios.
Net, if I want to use the pressures the factory designers and engineers thought were really best, I would use the Euro ones on my own vehicle as the guideline. And, that's backed up for my own comfort that as the people who know the vehicle better than anyone, they have concluded their Euro advice checks out on the Autobahn at 130mph (or 155 for some performance Audis). That's a big delta from the U.S. even with Arizona type desert extremes, and actually even more so in low speed limit and dense population Japan. If I wanted to go with the safety nannies and lowest common denominator belt, suspenders, duct and red tape, the U.S. ones are my ticket to ride. And BTW, since they do have this pretty unexplainable mismatch between the Q5 in a variety of motor flavors and weights with an identical wheel and tire fitment to the SQ5 (255/45-20's), it would not surprise me given the prior Mini ding (which happened as between S's and JCW's and wrong diameter wheels actually on the car IIRC) if Audi eventually gets the dubious honor of another "they couldn't get the sticker right" recall as Mini did. Here though, since the tire pressures are arguably meaningfully high, it may still pass the Ford Explorer fiasco remedy low water mark of sticker cures, since way low pressures were an Explorer Achilles heel.
Last edited by MP4.2+6.0; 09-23-2013 at 08:47 AM.
09-23-2013, 04:05 AM
#24
AudiWorld Super User
Interesting thread....
I have a 3 week old Q5 TDI P+ with the 19" 235/55's. I'm researching 20" rim/tire combinations, reason being the limited availability of any performance AS tires (maybe an oxymoron?). I been driving S4's since 2000 and I like more response than an H-rated tire gives.
This thread answered a questions I had about tire pressures from the Q to the SQ.
ps I'm S4-less for the first time in 13 yrs and it is not easy.
This thread answered a questions I had about tire pressures from the Q to the SQ.
ps I'm S4-less for the first time in 13 yrs and it is not easy.
Last edited by bpp; 09-23-2013 at 05:25 AM.
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