colladacool

Hey Guys,

Would there be any problem running 245/40/19 on the standard 19inch 5 spoke rim given with the black optic pack instead of running 245/35/19. I have a friend who has a 2014 a4 with the same rims and he wants to get new ones and i will end up buying his for $200. They are in great condition and this way i keep the look of the wheels i will receive on my car when it arrives. Would there be any problem running these instead of buying 245/35/19 which are coming up more expensive than the 245/40/19. I am looking to buy the General tire gmax A S 05 as i have these on my other cars and they are great but not offered in the size 245/35/19 but instead offered as 245/40/19. Let me know guys, i don't feel like spending more on newer rims and tires if i could spend $200 on the these rims and get the new all season tires for about $600 at discount tire direct so total $800. Please let me know some options and please let me know if these would be a problem to run the 245/40/19 instead of 245/35/19.

Thanks

markcincinnati

I believe there is a formula (on Tire Rack, perhaps?) that allows you to enter your tire's dimensions and it will tell you the impact on the various "systems" (which may just be the speedo, but I doubt it) due to the distance you will travel for one revolution of the tire/wheel.

There may be an adjustment that can be made to compensate for any "errors" a given wheel/tire combo may evoke.

You could check with the dealer to see if there is an adjustment and you could also find out what could happen if you just do it. I assume the speedo would be off -- but any effect on the computer that controls, monitors, and causes the engine management to adapt is unknown (to me).

There is a technique called "Plus Sizing" -- most folks consider +1 sizing (some +2). But there is a type of sizing called Plus Zero sizing. Which makes me wonder if there isn't a type of sizing that we could call Minus Zero sizing.

For level setting purposes: When someone speaks of Plus 1 sizing and they have 19" wheels, they typically mean they need to know the tread width and aspect ratio that would be required if the wheel size was increased to 20".

When someone speaks of Plus Zero sizing, they do NOT change the diameter of the wheel. So, if the wheel is 18" and the tire size is 235 x 45 (I made this up, this is not for your Audi), a Plus Zero size strives to find the next widest tire and the aspect ratio require to maintain the circumference of the wheel/tire as it rolls on down the highway. This might, in my made-up example, mean 255 x 40 would be the correct size. When the wheel size is NOT increasing or decreasing Plus Zero is grossly calculated as follows:

235 x 45 = 105.75

It is typically said it is important to stay within 3% of this ratio.

265 x 40 =106 (winner, winner, chicken dinner)
255 x 40 = 102 (probably OK)
245 x 40 = 98 (too big of a difference)

Now in your case, you may want to do the following: Minus Zero Sizing

19" wheels assumed:

245 x 35 = 85.75 OEMs
245 x 40 = 98 (pretty big change, probably not gonna work)
235 x 40= 94 (still a pretty big change)
225 x 40 = 90 (might work)
215 x 40 = 86 (perfect size) AT THIS ASPECT RATIO

Now let's try our minus zero game using an aspect ratio of 45.

245 x 35 = 85.75
235 x 45 = 105.75 (too big)
225 x 45 = 101.25 (still too big)
215 x 45 = 96.75 (still too big)

Well hell, this isn't any fun, is it?

It seems we may need to try to go the other way.

245 x 35 = 85.75
255 x 30 = 76.5 (too small)
265 x 30 = 79.5 (still pushing it too small)
275 x 30 = 82.5 (probably OK) -- beware of pot holes and expansion joints

I do not know if a 275 tire will FIT, however.

Someone needs to tell you if 275 x 30 x 19" OR 215 x 40 x 19" tires are available and will fit.

These seem to be your most workable shoe sizes.

Of course, you have another option: Buy new wheels and tires or buy the exact size of tires that come with the thing but in another brand that comes in the 245 x 35 x 19" size.

Maybe someone else will come up with a workable and affordable option.

mplsbrian

That 40-section tire on the OEM wheel will throw your speedometer off by 3.5%. Your ride height will also increase by 11.75mm, and your arch gap will decrease by 11.75mm. Whether that is marginal enough to "fit" is uncertain; generally people just don't do that sort of thing around here. Assuming that they do fit, you might need to get an alignment due to the ride height change but beyond that I cannot tell you what other technical challenges you're likely to face with this setup. Again, generally speaking, nobody who buys a brand new S model Audi does this. Most of us who spec'd 19" summer wheels either just spent or are about to spend another $1800-3500 on a dedicated aftermarket 18" winter wheel & tire setup, with a select few who experience mild winters or live below the snow belt getting OEM-size performance all seasons.

Also, the 19" 5-spoke rotor style wheels that come on the B9 S4 w/ Black Optics package are not the same as the similar looking rotor wheels that came on some previous A4s. You will need to research to see if they fit but I suspect they will not due to an incompatible offset.

markcincinnati

I agree with the above thoughts -- hopefully the OP will see that his potential plan is risky, expensive and, unfortunately, not without some significant flaws.