Staggered

[Outie Essex]

Part A:
So let me tell the reason behind what I am about to tell you. I had stock wheels on my car when I bought it. I hit a nasty pot hole a few weeks ago and had to get a new front tire. Since there aren't many places that stock 255/35/20 Michelin PS A/S 3+ tires, I looked for a nice used one. Well I found a set of 2 that still had about 90% tread left. Replaced the driver front tire and kept the other as a spare. I now realize I should have replaced both front tires to have even wear side to side, but still it did not change the comfort of the ride. Still ran smooth as ever.
Part B:
Well then I decided to buy some wheels from Vossen, 20x9ET25 fronts and 20x10.5ET42 rears. So since they were staggered I needed to either fit a 295/30/20 rear to match the 255/35/20 fronts or 245/35/20 fronts and 285/30/20 rears. The issue I ran into was that Michelin didn't make a 295/30/20 in the MPSAS3+, and I figured since I want to keep the exact same type of tire, MPSAS3+, I would need to go with the 245/35/20 F and 285/30/20 R. Those sizes have a 0.5mm total diameter difference and only a 2mm total circumference difference. Well the issue is that I thought since I just got these newer 255/35/20s I would keep those on the front and put my brand new 285/30/20s on the rear. These have an 8mm difference in total diameter and a 24mm difference in total circumference. I have read many places that say to stay within 1% front to back. Well those 2 sizes are 1.1% while the 245/35 and 285/30 are 0.1%. I assumed that since the 1.1% was close enough to 1% that it wouldn't matter too much. I WAS WRONG! It rides like shit, with a shuddering feeling. I am thinking this is because the quattro isn't happy.
Part C:
I just dropped my car off at Tire Kingdom to have brand new 245/35s put on the front. I tell the guy my situation and he begins to give me crap that they may not be able to put them on my car because it isn't a OEM size tire. Stating that I could possibly sew them if handling was the cause of a wreck after the tires are installed. That and said it would void the warranty. Well I don't have a warranty anymore so that's a moot point. But the fact that he said he may not install them because its a different size than OEM baffles me. My understanding of the issue with tire size and quattro is that as long as the overall diameter and circumference are the same on all four wheels, it doesn't matter what size they all are. Like if I decided to put 205/50/15s on all four corners it would look stupid as hell but it would not affect the quattro since it is essentially a square setup. And the fact that 245/35 fronts and 285/30 rears have damn near identical diameter and circumference, I should be fine, right?

[MacFady]

...the fact that 245/35 fronts and 285/30 rears have damn near identical diameter and circumference, I should be fine, right?

Yes. Many who run staggered set-ups actually aim for within 3%, whether you agree with that number or not (I'm guessing not given the experience you mention) I would have no hesitation running 245/35F & 285/30R.

[Outie Essex]

Yes. Many who run staggered set-ups actually aim for within 3%, whether you agree with that number or not I would have no hesitation running 245/35F & 285/30 rear.

I couldn't imagine having a 3% difference. This 1.1% is an insanely rough ride.The quattro is fighting itself every step of the way.

[15 Phantom S6]

The shop should stick to putting tires on wheels and leave it at that.

If they are scarred of liability, all they have to do is put a note or disclaimer on the invoice that states customer is on the hook for the sizing and they are on the hook for proper installation.. If they won't do it, go somewhere else.

I understand where the shop is coming from, but since this is not a set-up they recommend and they relayed this to you, they can't be on the hook if you insist on a particular setup you want.. They just need to document it..

Now if the size of the tire is too skinny or too fat for the wheel itself, then I totally agree with them on not doing the work, they have to ensure their work is safe.

I'm not a fan of staggered wheels on AWD cars but regardless, I agree with you that a 0.1% difference in rolling diameter should be fine for the Quattro system, but I have no experience to back it up, it just sounds logical to me..

[Turbavanttro]

I don't think the rough ride has anything to do with the 1.1% difference in circumference between your front and rear tires. The quattro system can handle up to around 3% difference.

The rough ride is likely caused by an issue with one or both of the used tires (flat spot, improper balance, torn belt, etc.) or another cause unrelated to the size of the tire.

[Outie Essex]

I don't think the rough ride has anything to do with the 1.1% difference in circumference between your front and rear tires. The quattro system can handle up to around 3% difference.

The rough ride is likely caused by an issue with one or both of the used tires (flat spot, improper balance, torn belt, etc.) or another cause unrelated to the size of the tire.

I know one of the used tires is fine, but the other was never installed until now. That very well could be the problem, but the rough ride isn't 100% of the time. It is exacerbated by acceleration. Once at speed, either slow or fast, the ride tends to smooth out a tad. This is why I don't really think its a bad tire.

- - - Updated - - -

The shop should stick to putting tires on wheels and leave it at that.

If they are scarred of liability, all they have to do is put a note or disclaimer on the invoice that states customer is on the hook for the sizing and they are on the hook for proper installation.. If they won't do it, go somewhere else.

I understand where the shop is coming from, but since this is not a set-up they recommend and they relayed this to you, they can't be on the hook if you insist on a particular setup you want.. They just need to document it..

Now if the size of the tire is too skinny or too fat for the wheel itself, then I totally agree with them on not doing the work, they have to ensure their work is safe.

I'm not a fan of staggered wheels on AWD cars but regardless, I agree with you that a 0.1% difference in rolling diameter should be fine for the Quattro system, but I have no experience to back it up, it just sounds logical to me..

I agree 100% with you. If its a safety hazard then the shop has every rite to say no, but if its a mechanical issue I think they should install what the customer wants.

[Arn560]

Did you try adjusting the tire pressures, you might be running too high a pressure.

[Outie Essex]

Did you try adjusting the tire pressures, you might be running too high a pressure.

So the recommended tire pressure on the door panel is 46lbs front and 48lbs rear. When I got the car home after they install the wheels there was 48lbs front and 36 lbs rear. So I adjusted the fronts to 46 and pumped up the rears to 46 as well. Still the same ride.

[Outie Essex]

UPDATE: I just received a call from Tire KingDUMB saying they can only install tires that match what the car's tag says. I think its complete BS but I can't make them install my tires. Guess I will be going to a different store.

[gk1]

IIRC TireRack suggests not having any more than 4/32" tread depth difference. If they are correct that's 6.35mm max diameter difference, and you are at 8mm. Could be as simple as that.

There are a few other things to consider:

-The ABS and all the electronic traction systems. ASR ESP etc.
From my understanding they are calibrated to OE sizes and could be unhappy if you change that by too much. That being said, I think you are within the range where they should not be affected, but don't know for sure.

-Tire pressure
The US door sticker is solely for stock size tires and fully loaded car. (people and trunk) You are outside both those parameters so you will need to invent new pressures for your setup.
A 245/35/20 on a 9" wheel will not have the same stiffness rate as a 285/30/20 on a 10.5" when inflated the same. (Front at 44 and rear at 39 might be close, you'll have to play around with pressures.)

-Dynamic tire size
While the online calculators say they are close as you stated within 1.1%, I'm unable to tell the difference in diameters as you get up to speed. I can assume they are close since steel radial tires don't grow much, but perhaps they grow at different rates exacerbating your issue. Not 100% on that one

-Load rating
The stock 255/35/20 is a 97 XL load rating. The 245/35/20 is only a 95XL...in reality probably still enough, but most shops will not risk putting a lower load rated tire on than stock.

-Scrub radius (nothing to do with tire radius)
Maybe not your issue right now, but it may affect handling too, even if you get the shutter sorted out. A 20mm increase in scrub radius for those front turning tires is rather large. Not insane, but still can affect how the car "feels" on the road...ie. tracks straight on highway or feels awkward/"fights you" when turning.

-Sport Diff
I can't recall if that was standard on the '13's, but technical details regarding the sport diff do seem to be somewhat of a mystery. In theory it should only be affected by side-to-side rear diameter differences in tires, but the sport diff coupled with electronic traction aids etc may be another story. Again not 100% on that one either, just a thought.

If it were me, before I do anything, I assume you still have the other two 255/35/20 mounted on stock rims correct?...I'd put them on the back in place of the 285's and first make sure that sets everything back to normal and check for any rubbing back there.

Also, I'm not recommending this but then you could play mix and match with the tires and get the ones you want the 245's on off the car so you could take them over to a tire place to mount the tires...They usually give no issues if you give them just tires to mount on wheels not on a car.

Unfortunately my opinion is a square setup would have still been mechanically best, but I understand aesthetically not what you were looking for. Since you have already decided to travel down the staggered road I only want to help the best I can.

[Outie Essex]

IIRC TireRack suggests not having any more than 4/32" tread depth difference. If they are correct that's 6.35mm max diameter difference, and you are at 8mm. Could be as simple as that.

I am hoping this as well.

There are a few other things to consider:

-The ABS and all the electronic traction systems. ASR ESP etc.
From my understanding they are calibrated to OE sizes and could be unhappy if you change that by too much. That being said, I think you are within the range where they should not be affected, but don't know for sure.

Are you referring to changing from lets say a 500mm total diameter to a 508mm or 492mm total diameter?

-Tire pressure
The US door sticker is solely for stock size tires and fully loaded car. (people and trunk) You are outside both those parameters so you will need to invent new pressures for your setup.
A 245/35/20 on a 9" wheel will not have the same stiffness rate as a 285/30/20 on a 10.5" when inflated the same. (Front at 44 and rear at 39 might be close, you'll have to play around with pressures.)

Ok I can understand that. I will do some playing around when I get the shuddering to go away.

-Dynamic tire size
While the online calculators say they are close as you stated within 1.1%, I'm unable to tell the difference in diameters as you get up to speed. I can assume they are close since steel radial tires don't grow much, but perhaps they grow at different rates exacerbating your issue. Not 100% on that one

Not sure about this either but I do drive between 90-100mph quite often.

-Load rating
The stock 255/35/20 is a 97 XL load rating. The 245/35/20 is only a 95XL...in reality probably still enough, but most shops will not risk putting a lower load rated tire on than stock.

Once again I'm not sure about this either.

-Scrub radius (nothing to do with tire radius)
Maybe not your issue right now, but it may affect handling too, even if you get the shutter sorted out. A 20mm increase in scrub radius for those front turning tires is rather large. Not insane, but still can affect how the car "feels" on the road...ie. tracks straight on highway or feels awkward/"fights you" when turning.

So the scrub radius in the rears is negligible, while the fronts appear to be 20mm. But there is more to this than simply adding or subtracting the offset I believe. From what I understand, the lower the offset the deeper the concavity of the wheel will be, and the higher the offset the flatter it will be. But this is not true with Vossen wheels. The ET25s that I have are flat face and the ET42s that I have are deep concave. Not sure why that is.

-Sport Diff
I can't recall if that was standard on the '13's, but technical details regarding the sport diff do seem to be somewhat of a mystery. In theory it should only be affected by side-to-side rear diameter differences in tires, but the sport diff coupled with electronic traction aids etc may be another story. Again not 100% on that one either, just a thought.

It does have the sport diff but like you, I have no idea if it is affected by this.

If it were me, before I do anything, I assume you still have the other two 255/35/20 mounted on stock rims correct?...I'd put them on the back in place of the 285's and first make sure that sets everything back to normal and check for any rubbing back there.

This was my thought as well, I plan to swap the OEM fronts back onto the car and take the new front Vossens to get the new 245/35s put on. This will allow me to see if the 2 used tires I bought after my blowout had 1 good tire and 1 bad tire.

Also, I'm not recommending this but then you could play mix and match with the tires and get the ones you want the 245's on off the car so you could take them over to a tire place to mount the tires...They usually give no issues if you give them just tires to mount on wheels not on a car.

This was another troubleshooting thought of mine. It will take some time but I can put the OEM 255/35s on the rears and see if the problem goes away. I can do this before I do the front swaps.

Unfortunately my opinion is a square setup would have still been mechanically best, but I understand aesthetically not what you were looking for. Since you have already decided to travel down the staggered road I only want to help the best I can.

I completely agree that a square setup is best but I got a steal of a deal on these new wheels and wanted a deep concave so I had to go staggered since I didn't want to put 20x10.5s on the fronts.

[gk1]

-The ABS and all the electronic traction systems. ASR ESP etc.
From my understanding they are calibrated to OE sizes and could be unhappy if you change that by too much. That being said, I think you are within the range where they should not be affected, but don't know for sure.

Are you referring to changing from lets say a 500mm total diameter to a 508mm or 492mm total diameter?

Yes, or in your example with a 205/50/15. The ABS is not setup for something that small. Would running too small or large a tire on a square setup show a problem like you are seeing. I don't know for sure. The ABS would probably have issues though. What exactly that limit is I'm not sure either, but stock size tires for the S6 range from:
255/35/20 or 255/40/19 = 687 mm to 265/30/21 or OE winter setup 235/45/19 = 692-694 mm. Something with a 680mm diameter like you might be within spec, but much smaller could be an issue.

-Scrub radius (nothing to do with tire radius)
Maybe not your issue right now, but it may affect handling too, even if you get the shutter sorted out. A 20mm increase in scrub radius for those front turning tires is rather large. Not insane, but still can affect how the car "feels" on the road...ie. tracks straight on highway or feels awkward/"fights you" when turning.

So the scrub radius in the rears is negligible, while the fronts appear to be 20mm. But there is more to this than simply adding or subtracting the offset I believe. From what I understand, the lower the offset the deeper the concavity of the wheel will be, and the higher the offset the flatter it will be. But this is not true with Vossen wheels. The ET25s that I have are flat face and the ET42s that I have are deep concave. Not sure why that is.

Yep, that is kind of perplexing to me too I can only think concavity has more to do with the design and the wheel width.
Your fronts are 9"= 229 mm wide offset 25mm from center so you say it has 139mm backspace or the "spokes" have to travel 90mm from the face to get to the hub. Your rear is 10.5" = 267 mm wide offset 42mm from center = 175mm backspace so the spokes only travel 2 more mm or 92mm to the hub, but it looks so much more concave in your case.
Here is a guy with VFS6 20x10.5 ET30 that look quite concave on the car, but not so much leaning against the garage.
https://www.audiworld.com/forums/par.../#post25024121
I honestly don't know much about concavity...perhaps 1-2 mm difference in face-to-hub difference IS all it takes to make a somewhat dramatically different concave look or does Vossen actually manufacture the spokes differently between different sizes & offsets to achieve that look?

Not sure about this either but I do drive between 90-100mph quite often.

If you often drive those speeds then you may want to lean towards higher inflation pressures.

[Outie Essex]

Ok I can understand the total diameter issue. Like you said 687mm is my standard size wince I had the 255/35/20s. Now that diameter will be 679mm. Is there something I can edit using VCDS to make the car use the new diameter?

I am on my work computer so the pictures on that post didn't show up, but I understand what you are saying. The problem is that the front 20x9 are truly flat faced and the 20x10.5 are truly concave. I ran into the same illusion problem of wheels looking flat vs concave, but even the Vossen site says the ET25 are a flat face while the ET42 are deep concave.

I do tend to inflate my tires to 46-48lbs. Thats why I usually pump my tires when they are at operating temps, not cold. This ensures they are not over-inflated while driving.

[Outie Essex]

This could ALL have been avoided if Michelin made the PS A/S 3+ in 295/30/20!!

[gk1]

Ok I can understand the total diameter issue. Like you said 687mm is my standard size wince I had the 255/35/20s. Now that diameter will be 679mm. Is there something I can edit using VCDS to make the car use the new diameter?

I am on my work computer so the pictures on that post didn't show up, but I understand what you are saying. The problem is that the front 20x9 are truly flat faced and the 20x10.5 are truly concave. I ran into the same illusion problem of wheels looking flat vs concave, but even the Vossen site says the ET25 are a flat face while the ET42 are deep concave.

I do tend to inflate my tires to 46-48lbs. Thats why I usually pump my tires when they are at operating temps, not cold. This ensures they are not over-inflated while driving.

I thought I read there is a VCDS setting to change to alternate tire sizes within Audi's specific size categories, but not for individual specific diameters, but I never tried it. As discussed 1-2% (all 4 tires smaller or larger than stock) is within tolerance and plenty of people have run that without issue, but the percentage between axles and how it specifically affects ABS vs. quattro IDK like I mentioned before 6mm (compared to your 8mm currently) may be the absolute max.
Another thing you could try temporarily setting the pressures to like 44/54 that might make the overall rolling radius' closer. (Probably pretty close to max inflation pressure though.) Maybe 40/50 would be better.

I'd be careful inflating at operating temp. That goes against EVERY inflation recommendation from just about EVERY source. (except maybe racing)
I know you are in FL, but think about it this way "at operating temp" could mean you inflate to 46psi at 120ºF even if it is 50ºF outside, a swing of 7psi at least. AFAIK the tires are designed to be inflated to 46psi at the ambient(cold) 50º and can rise to 54+psi while operating as intended.

[Outie Essex]

I thought I read there is a VCDS setting to change to alternate tire sizes within Audi's specific size categories, but not for individual specific diameters, but I never tried it. As discussed 1-2% (all 4 tires smaller or larger than stock) is within tolerance and plenty of people have run that without issue, but the percentage between axles and how it specifically affects ABS vs. quattro IDK like I mentioned before 6mm (compared to your 8mm currently) may be the absolute max.
Another thing you could try temporarily setting the pressures to like 44/54 that might make the overall rolling radius' closer. (Probably pretty close to max inflation pressure though.) Maybe 40/50 would be better.

I'd be careful inflating at operating temp. That goes against EVERY inflation recommendation from just about EVERY source. (except maybe racing)
I know you are in FL, but think about it this way "at operating temp" could mean you inflate to 46psi at 120ºF even if it is 50ºF outside, a swing of 7psi at least. AFAIK the tires are designed to be inflated to 46psi at the ambient(cold) 50º and can rise to 54+psi while operating as intended.

Thanks for the heads up on tire inflation. I will switch back to doing it cold. And as for the VCDS modification, if anyone has experience with this please chime in. Thanks.

[Outie Essex]

So I just did some research and it turns out the 2014 S6 had a wheel/tire option of 235/45/19 on a 19x7.5. This overall diameter is 7mm more than my OEM 255/35/20. So I am going to go out on a limb and say that 8mm less is doable since a 7mm more is OEM. I understand its 2 different years, but how much really changed in that year.....

[gk1]

So I just did some research and it turns out the 2014 S6 had a wheel/tire option of 235/45/19 on a 19x7.5. This overall diameter is 7mm more than my OEM 255/35/20. So I am going to go out on a limb and say that 8mm less is doable since a 7mm more is OEM. I understand its 2 different years, but how much really changed in that year.....

Yes, I mention that above...that is the winter setup. I have them.
It is fine for all 4 tires, since you make them all 1.1% larger than stock (1-2% is usually fine) but you are currently 1.1% difference between axles....generally no bueno as you are seeing.

[Outie Essex]

Yes, I mention that above...that is the winter setup. I have them.
It is fine for all 4 tires, since you make them all 1.1% larger than stock (1-2% is usually fine) but you are currently 1.1% difference between axles....generally no bueno as you are seeing.

Yeah I found that out quick! Changing to a 1% difference for all of them when I get done with work. I have been reading up on some other forums that there is a procedure you can do with VCDS to correct the speedo error. Hoping it works. But even if it doesn't, its only a 0.6-0.7 mph difference at 60mph.

[gk1]

Yeah I found that out quick! Changing to a 1% difference for all of them when I get done with work. I have been reading up on some other forums that there is a procedure you can do with VCDS to correct the speedo error. Hoping it works. But even if it doesn't, its only a 0.6-0.7 mph difference at 60mph.

Cool.
Yeah I saw some of those VCDS threads too, but it was my understanding there were only pre-programmed selections like Tire 1, 2, 3 etc. and you couldn't account for such a small 1% difference since it was within tolerance anyway, and you see the stock vs. OE winter setup is 1% different anyway and Audi never re-calibrates for that. :)
But let us know what you find out.

[Outie Essex]

Cool.
Yeah I saw some of those VCDS threads too, but it was my understanding there were only pre-programmed selections like Tire 1, 2, 3 etc. and you couldn't account for such a small 1% difference since it was within tolerance anyway, and you see the stock vs. OE winter setup is 1% different anyway and Audi never re-calibrates for that. :)
But let us know what you find out.

Shall do. I'm hoping to get rid of the shuddering first and foremost. Then I will attack the speedo error when I get my buddy's ross-tech.

[Outie Essex]

So first thing I did when I got home was swap the rear wheels out for the OEM, which made my car square again. Took it for a stroll and it rode smooth as a baby's butt! So I can definitively say that the shitty ride was due to the staggered tire sizes.

[Litespeed72]

Strange they refused to mount them - although here in PA I have been told that non-stock sizes may not pass state inspection.

[Outie Essex]

Strange they refused to mount them - although here in PA I have been told that non-stock sizes may not pass state inspection.

That’s even weirder

[gk1]

So first thing I did when I got home was swap the rear wheels out for the OEM, which made my car square again. Took it for a stroll and it rode smooth as a baby's butt! So I can definitively say that the shitty ride was due to the staggered tire sizes.

Glad you found out, and it wasn't something worse.
To be clear for anyone else looking, so far you conclude the issue was was not due to the staggered widths but due to the 1.1% diameter difference between the front 255/35/20 and the rear 285/30/20, correct?
Do you still intend to get the 245/35/20 on the front and return the 285/30/20 to the rear? (only 0.1% difference)

[Outie Essex]

You are correct and yes that is my plan. I will have the 245/35 fronts and 285/30 rears on tomorrow and will report my findings.

[esemes]

wrong coast but if you were west I have someone that could at least search for alternate settings for you. Good luck!

[Outie Essex]

Thanks!

[esemes]

Thanks!

he's on here often and luckily lives close by to me!!

DRK319

[Outie Essex]

Well if he can chime in at some point I would be much appreciative.

[esemes]

Well if he can chime in at some point I would be much appreciative.

pm him bud.

[Outie Essex]

Just sent. Thanks.

[Arib7]

Had the same issue a month ago, long story short, i had to put 235/45/19 front and 245/40/18 rear for a day only, while i balanced the other two 19s, and the car rode like on train tracks for a mile only, and all possible warning lights came on and car went into limp mode. Luckily i have the OBD eleven and reset all errors. Barely drove the car home. Next day i put the other 19s on, everything went back to normal without any intervention from me, so i take it quattro doesn't take it well if all tires are not the same size

[Outie Essex]

I have been lucky so far not to get any lights. And I only need her to be good for 1 more day.

[Outie Essex]

Had the same issue a month ago, long story short, i had to put 235/45/19 front and 245/40/18 rear for a day only, while i balanced the other two 19s, and the car rode like on train tracks for a mile only, and all possible warning lights came on and car went into limp mode. Luckily i have the OBD eleven and reset all errors. Barely drove the car home. Next day i put the other 19s on, everything went back to normal without any intervention from me, so i take it quattro doesn't take it well if all tires are not the same size

I just put those numbers into wheel-size.com and OMG thats a huge difference. 6% front to rear. You are very lucky nothing broke.

[Outie Essex]

he's on here often and luckily lives close by to me!!

DRK319

Just got a reply back from DRK319 and he said he has no idea. Said he is new to the Audi scene and is still putting his car together. Is there someone else?

[Outie Essex]

Ok I just got the 245/35s put on and the ride is smooth again! So lesson learned, if you buy an AWD car that is supposed to have a nice ride, don't go fking it up with tires that don't match in diameter and circumference.

[Outie Essex]

Here are some pic to show poke, stretch, and protection. In case it isn't 100% clear, The entire wheel is protected by the tire front and back.
OEM is 255/35/20x8.5ET45 squared.
First 3 pics are front 245/35/20x9ET25.
Next 3 pics are rear 285/30/20x10.5ET42

[Arib7]

I just put those numbers into wheel-size.com and OMG thats a huge difference. 6% front to rear. You are very lucky nothing broke.

i know right, lesson learned the hard way...