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255/40R20 tires

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Old 08-15-2014, 06:36 AM   #1
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Default 255/40R20 tires

Has anyone put 255/40R20 tires on the Audi A6 20 inch rims? Standard size is 255/35R20. I know it shouldnt be an issue and will give more tire thickness and protection.
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Old 08-15-2014, 07:08 AM   #2
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I don't have 255/40/20 tires but if you are upsizing the tire size to 255/40 from factory recommended 255/35, be aware that your speedo will be off by nearly 4%. (If you are driving at 100mph, you will actually be going at 104mph) Same goes for your mpg usage on DIS, you will see or "feel" that your gas mileage has gone worse. In general, I think it's wise not to go over the +/- 3% mark diff.

The overall diameter will also be 1 inch higher than stock so if you are lowered or plan on lowering later on, depending on the specs of the wheels of course but you might have rubbing issues against the fenders or the fender liner.

If you really had to upsize, I'd rather go for maybe a 265/35 which will be only 1% off or even 275/35 which will be like 2% off but I don't know how the width of the tire will clear inside the fenders.

Maybe it's just me but I'd stick with 255/35 since 255/40 won't give you any noticeable added protection and 255/40s probably cost way more than 255/35s since they're not a popular size of a tire.

On one of my previous car, the stock recommended size was 225/35 but I went 225/40 thinking that it will add more protection for the expensive wheels i had but I ended up having nothing but problems and regrets... (rubbing like crazy on bumps and turns, and 2 speeding tickets for ~5mph over 65 limit when I set my cruise control at around 65.)
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Old 08-15-2014, 08:22 AM   #3
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I too have considered going to 255/40 20's because of the increase in wall height and therefore a less jolting ride.

4% error in diameter should fix the error in the speedometer from stock and the DIS MPG can be modified to compensate.

There are plenty of tires out there in that size including the Michelin PSS so I too am interested in feedback regarding the OP.
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Old 08-15-2014, 06:49 PM   #4
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Quote:
Originally Posted by yoonskim View Post
I don't have 255/40/20 tires but if you are upsizing the tire size to 255/40 from factory recommended 255/35, be aware that your speedo will be off by nearly 4%. (If you are driving at 100mph, you will actually be going at 104mph) Same goes for your mpg usage on DIS, you will see or "feel" that your gas mileage has gone worse. In general, I think it's wise not to go over the +/- 3% mark diff.

The overall diameter will also be 1 inch higher than stock so if you are lowered or plan on lowering later on, depending on the specs of the wheels of course but you might have rubbing issues against the fenders or the fender liner.

If you really had to upsize, I'd rather go for maybe a 265/35 which will be only 1% off or even 275/35 which will be like 2% off but I don't know how the width of the tire will clear inside the fenders.

Maybe it's just me but I'd stick with 255/35 since 255/40 won't give you any noticeable added protection and 255/40s probably cost way more than 255/35s since they're not a popular size of a tire.

On one of my previous car, the stock recommended size was 225/35 but I went 225/40 thinking that it will add more protection for the expensive wheels i had but I ended up having nothing but problems and regrets... (rubbing like crazy on bumps and turns, and 2 speeding tickets for ~5mph over 65 limit when I set my cruise control at around 65.)
Thank you for your excellent points. I have used a size up before on a Lexus GS and it was a 3% speedo error but the issue was the rubbing when full turn in the parking lot when the tires were new up to about 10k miles then it stopped. I won't be lowering the Audi A6. It already has the black optic package with the sports suspension.

Since the A7 comes with the same rim size but 255/40R20 tires, I thought it shouldn't be an issue on the A6 since its a similar chassis. But now I am not sure. The size 265/35R20 doesn't come with the Michelin Pilot Sport A/s tires.
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Old 08-15-2014, 07:27 PM   #5
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I have not run that particular size but have run PSS 275/35 20 which have a diameter of 27.6" vs 28" for the 255/40 20. The only issue I had, which was minor, was a little rubbing of the rear fender inner liner when going over bumps. My car is lowered about an 1" to 1.25" from the stock sport suspension height. With my PSS installed they corrected the speedo error to were the error was at most off by 0.5 mph based on a GPS based comparison. In my opinion using a 255/40 20 tire really should be no problem except may be under certain lowered suspension conditions.
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Old 08-16-2014, 03:55 PM   #6
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Quote:
Originally Posted by jr'sAudiA6 View Post
I have not run that particular size but have run PSS 275/35 20 which have a diameter of 27.6" vs 28" for the 255/40 20. The only issue I had, which was minor, was a little rubbing of the rear fender inner liner when going over bumps. My car is lowered about an 1" to 1.25" from the stock sport suspension height. With my PSS installed they corrected the speedo error to were the error was at most off by 0.5 mph based on a GPS based comparison. In my opinion using a 255/40 20 tire really should be no problem except may be under certain lowered suspension conditions.
You ran 275 series tire on the stock rim (as pictured in your signature)?
A bit of a stretch no?
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Old 08-16-2014, 04:57 PM   #7
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Originally Posted by Baloo588 View Post
The size 265/35R20 doesn't come with the Michelin Pilot Sport A/s tires.
Ding! 255/35-20 seems to be about the most popular size in this range. That's actually why I got the 20" wheels on my S6 - because the goofy 255/40-19 size has a lot fewer tires offered in it.

I'd like a taller sidewall, no doubt about it, but I suggest playing around with inflation pressures before going to an oddball tire size. See if you can find a balance between uneven wear and ride comfort. With that said, also consider that sidewalls are very different among different tire brands and models, so perhaps try to find a 255/35-20 which better matches your wants/needs?
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Old 08-17-2014, 12:16 PM   #8
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Quote:
Originally Posted by Superfly_A6 View Post
You ran 275 series tire on the stock rim (as pictured in your signature)?
A bit of a stretch no?
No, what is shown in the picture are stock rims with 255/35 20 tires. The photo that is my avatar has the A7 wheels with the 275/35 20 PSS tires.
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Old 08-17-2014, 03:07 PM   #9
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Did any of you have any issues with the 20 inch rims and potholes? I am not opting for the tire/wheel insurance for 1,600 for 5 years. Too much and I won't even break even.

I am considering the 275/35R20 tires in Michelin Pilot Sport A/S 3. Thank you jr'saudia6!
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Old 08-18-2014, 07:46 AM   #10
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I ran 255/45R20s and they would rub on the fender bolt, I imagine 40s should be fine.
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