[Eric_UK]

Thanks mowmow, it's good to know there might be a solution out there (I too have the 255/45R20 rims). Unfortunately I've only recently changed all four of my tyres to Goodyear Eagle F1 SUV - they also claim to feature foam inserts to reduce cavity resonance but it hasn't helped in my case. It may be that the Michelins are more effective in this respect. I'll just have to try and retain my sanity until it's time to change them again.

 

[mowmow]

Eric_UK,

I wonder if you got the tires that you think you did. In looking at Goodyear's website, it appears that they are doing the same thing that Michelin is doing: Making similarly named tires with and without this technology.

Here is a link to Goodyear's Eagle® F1 Asymmetric SUV AT in the US, which might be what you have:
=> Goodyear Eagle F1 Asymmetric SUV AT Tires | Goodyear Tires

And here is a link to their Eagle® F1 Asymmetric 3 SoundComfort Technology™
=> Eagle® F1 Asymmetric 3 SoundComfort Technology™ Tires | Goodyear Tires

I wasn't able to find an"SUV" tire with SoundComfort Technology, which does indeed include the foam liner.

Maybe you can get an exchange if you were misled by a salesman...

Update: I do see a page that states there is an SUV version, but it's curious that the above page doesn't mention the technology - and it's MUCH cheaper - suggesting it may not have it. Given the confusion I experienced, I made it a point to see my actual tires before installation to make sure they were the real deal. Might be worth checking into.

 

[Eric_UK]

mowmow - I think you're right. Goodyear appear to print a logo on the side of their tyres which feature the Sound Comfort Technology and mine don't have it. I'll see if I have the receipt and I'll then pursue this with my dealer. Thanks for noting that.

 

[Eric_UK]

SO... I went back to the tyre dealer (Kwik-fit, UK) and, after checking, they confirmed they they had in fact fitted the wrong tyre (the Eagle F1 but without the 'Tyre Comfort Technology' designed to reduce cavity resonance). To their great credit they agreed to fit the correct tyres free of charge. I drove the car with the new tyres for the first time today and it is a VAST improvement, to the extent that, had these tyres been fitted to the car when I bought it, I would probably have never noticed the droning sound. Now that I'm aware of what to listen for I can still hear it (mostly at high speed on poor road surfaces) but it is significantly reduced and entirely acceptable. Many thanks to mowmow and all for your contributions. I'm now entirely happy with my Q5 and can cease the therapy!!

 

[mowmow]

Great to hear, Eric_UK - so glad it worked out for you!

Might I suggest that you try varying the pressure to see if it makes a difference. In engineering terms, I see Goodyear's Sound Comfort and Michelin Acoustic Technology as "notch" filters that are targeted to the tire/wheel's resonant frequency, while the lower and higher frequencies are managed largely by other/older car and tire technologies. A tire pressure change could move the notch and resonance closer into alignment, which is what you want.

I recently increased my tire pressure from the car's recommendation of 33PSI to 38PSI (tire is rated to 50PSI), as I've been getting a slight vibration for the first 10 miles or so due to flat spotting while parked. My fear was that this might bring the resonance back a bit, but if anything it's now completely gone. It also reduced the flat spotting. I'm also very happy with the ride. My only concern is this thing seems to coast forever now and I'm going to go through brake pads quicker LOL.

 

[Eric_UK]

Hey mowmow - what you lose on the brake pads you'll gain on fuel efficiency (Every cloud...). It's an interesting point that you make regarding tyre pressure and I'll certainly try that. I've yet to check what pressure the tyre dealer applied when they were fitted. Prior to getting the tyres replaced, I was running the previous Eagle F1's at 38 PSI - they're high load tyres (105) so that's well within their range. In addition, I found the fuel efficiency took a significant hit if I ran them much lower (they have quite a high rolling resistance). Prior to your observation (increased pressure = reduced noise) I'd also assumed that higher pressures would exacerbate the problem - this was based on my own experience and that of others who seem to have relieved the issue by running lower (albeit without noise reducing tyres). I guess intuitively I think of it like flicking a balloon, which is more inclined to resonate when full than when half inflated. However I get your point about the noise reduction technology working as a notch filter and there's no doubt an optimum operating mode (related to air density, internal volume etc.) which could well be at the higher end of the pressure range. Just as a side note, when I was trying to understand the nature of the resonance, I recorded the noise and subjected it to a spectral analysis which showed it was occurring around 200Hz. Changing the tyre pressure didn't seem to change the fundamental frequency, which I thought odd, given that I would have expected cavity resonance to be significantly dependent on the internal volume of the resonant space. I can only assume that the internal volume doesn't actually change that much or that air pressure and other factors work to cancel the effects of greater volume (though I wouldn't pretend to understand the physics involved). Anyway the good news is, thanks to your help, I can now enjoy the driving experience again. Any further improvements I can achieve will just be a bonus.

 

[mowmow]

Could not agree more on the mileage. That and cornering is what I was really aiming for with the pressure increase. The resonance was so low at the lower pressure that my fear is it would come back a bit at the higher pressure. I cannot say for sure that it DECREASED with the higher pressure with my new tires - it's just not there, and maybe it wasn't there before, though I thought maybe there was a hint initially. Maybe the foam liner changes a little over the first miles and the pressure is unrelated. What I did notice with my old tires was that the resonant frequency did shift upward slightly as I increased vehicle speed. I attributed that to guitar string behavior and centrifugal force increasing tension along the tire's outer perimeter and thus shifting resonance upward. It might follow that increased tire pressure would have a similar effect.

In any case I think there is a real chance that I will finally forget about all this, which up until recently, I was convinced would not be the case. Is the technology worth the extra several hundred bucks? On this vehicle, ABSOLUTELY.