Plan on running 225 tires in the front and 245 in the rear..

[romansoldier100]

I was under the impression that that was not recomended. The wheels I bought have an offset problem. So I bought a set of 4 new Bridgestone S03 that were 245 35 19, and I have rubbing in the front when I go over bumps.

I spent 900 on these new tires, so I do not want to get 225 all around right away.

I called the dealer and he said that it would be ok to run 225 in the front and 245 in the rear as long as they were both the right diamator.

I have located some new Bridgestones that are 225 35 19 but before I buy them, I just wanted to make sure that I am not being pulled around by the dealer.

I thought about it this way, it is the same thing as someone running a 20mm spacer on the rear.. should be ok right?

[wayneB7]

I thought about it this way, it is the same thing as someone running a 20mm spacer on the rear.. should be ok right?

You are forgetting one thing. There is a bigger contact patch with the wider rears so there would be a difference in friction between the fronts and rears.

This definitely would not be a problem with a FWD A4, but with a Quattro, I am not so sure. What is your car?

[Glassnpowder98]

You are most likely going to need like a 225/40/19 or 225/45/19 to match up with the 245/35/19's. I don't really feel like doing the research or math right now, but know that the middle number is a percentage sidewall dimension of the first number (width). Therefore, overall diameters and sidewall sizes are going to be different between a 245/35/19 and 225/35/19. The overall diameter is what you need to worry about so you don't do any damage to your quattro system.

[Alky]

You are most likely going to need like a 225/40/19 or 225/45/19 to match up with the 245/35/19's. I don't really feel like doing the research or math right now, but know that the middle number is a percentage sidewall dimension of the first number (width). Therefore, overall diameters and sidewall sizes are going to be different between a 245/35/19 and 225/35/19. The overall diameter is what you need to worry about so you don't do any damage to your quattro system.

Interesting, I never knew that.

http://www.tirerack.com/tires/tirete....jsp?techid=46

Sidewall Aspect Ratio
Typically following the three digits identifying the tire's Section Width in millimeters is a two-digit number that identifies the tire's profile or aspect ratio.

P225/50R16 91S

The 50 indicates that this tire size's sidewall height (from rim to tread) is 50% of its section width. The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm. By converting the 225mm to inches (225 / 25.4 = 8.86") and multiplying it by 50% (.50) we confirm that this tire size results in a tire section height of 4.43". If this tire were a P225/70R16 size, our calculation would confirm that the size would result in a section height of 6.20", approximately a 1.8-inch taller sidewall.

[9Hooker]

also, remember. now with 2 different tire sizes one half of the car will be moving faster than the other, quite possibly enough to make your center diff start biasing torque... all the time.

[Glassnpowder98]

also, remember. now with 2 different tire sizes one half of the car will be moving faster than the other, quite possibly enough to make your center diff start biasing torque... all the time.

Yeah, it's not just going to bias torque, it's going to cause damage to the quattro system because the fronts are going to be moving faster than the backs and that's not too great for a mechanical system that is supposed to be moving at the same speed. I did a quick little search for "rolling diameter" and found that Audi recommends your tires don't deviate by more than 3%. I also found this link...

http://www.1010tires.com/TireSizeCal...?action=submit

I plugged in the numbers and it looks like you should be good with a 225/40/19. You might want to check my math just to be on the safe side.

[Jer]

As long as the outside rolling diameter is the same you will be fine accept for under hard launches but this is what the system was designed for. Under normal motion though the car will not know a difference as long as the outside rolling diameter is the same regardless of width especially when you're talking about such small differences.

Can it be done? Sure. Should it be done? Why?

I guess you are going for a certain look but let me tell you that one of the great things about AWD is uniform tire/wheel sizes at all four corners. RWD cars need big meats on the rear for traction and even then putting the power down is an art form. AWD is great because you can more common (and less expensive) tire sizes at all four corners and get even better traction than the RWD with HUGE tires on the rear. Where this also comes into play as far as the financial aspect is tire rotation. You can do a full four corner tire rotation which also lengthens the life of the tires. I had 255's on teh front of my Supra and 295's on the rear and hated it because not only were the rears substantially more expensive but they didn't last long not only from losing traction but also from the fact that you can only swap from left to right during rotations.

So, if you do the math on it it can be done but what I'm saying is that it's really not worth it.

[mingamells]

Even if you get exactly the same diameter, the narrower tires will wear faster because you'll have more psi (same weight, smaller area) between the tire and road. So the narrower tire will lose its diameter faster than the wider tire.

I personally wouldn't risk my quattro system like that. Just my opinion of course.

[Jer]

Even if you get exactly the same diameter, the narrower tires will wear faster because you'll have more psi (same weight, smaller area) between the tire and road. So the narrower tire will lose its diameter faster than the wider tire.

I personally wouldn't risk my quattro system like that. Just my opinion of course.

Where do you get your information?

[mingamells]

Where do you get your information?

It's just basic physics. The narrower tire has less surface area in contact with the road. So assuming the tires wear at the same rate (mass/rotation), then the narrower tire will wear its tread out faster. Imagine filing the pointy tip off of a nail. It happens fast. You can take material away quickly. If you try to file that nail along its entire shaft length, it will take a long time to file away the same depth you filed away on the tip.

But I dunno, the difference could be small enough to make it a non-issue. Maybe the quattro system can handle it easily.

[craymond5]

Use the tire calculator and keep the difference within 3 percent and you will be fine. I as well as many others have run staggered tires on quattro with no differential issues at all. Even Audi will tell you it is ok within 3 percent. You probably won't even notice the difference in performance unless you are tracking the car but you will however notice the tire rubbing every time you hit a bump.

[Jer]

But I dunno, the difference could be small enough to make it a non-issue.

Bingo.