Hi
I have a 2014 Audi a4 s-line with tire size 255/35 r19, now my question is;
Can I fit 255/40 r19 tires without damaging the engine or the vehicle?
Any advice, comments would be appreciated thanks!

Using tires with a higher sidewall profile will mean that the overall diameter of the tire is a bit bigger than stock - in this case by about one inch - so your speedometer will read a bit low. Assuming you have not lowered the car from its stock ride height - it should be OK. No issues with the engine or quattro system, as long as all four tires are the same. However, there are some excellent on-line forums where you can post this question and get feedback from a larger audience of Audi enthusiasts. I suggest you check out the A4 forums in Audizine.com, AudiWorld.com, and Quattroworld.com.

The higher sidewall raises the vehicle's center of gravity, which will affect handling, acceleration, and odometer/speedometer readings. That should be about it.

Just to clarify the effect on speedometer and odomter readings - the 255/40R19 tires are about 3.8% larger in diameter than are the stock 255/35R19's, so your speedo and odo will both read 3.9% low. For example: if the speedometer says you are going 60 MPH you may actuially be going about 62.3 MPH. Just be aware of this in case you are pushing the speed limit.

Ok, so what do you guys suggest I should do,.
Should I leave them on or take them off?
Should they be fine without taking them off?

I would only use the 255/35 R19 tires.

I would agree with TxGreaseMonkey - I wouldn't deviate from stock without very good reason. This is a new car, so why are you changing out the tires?

If you have already done the tire change then you adjust your expectations for gas consumption, and drive accordingly. Back in my day we tricked our vehicles out with all kinds of rims and tires, and the young kids still do. This is no different and you shouldn't trip out over it either. I doubt the tire dealer takes them back for free anyway, so unless you have money to burn on another set of tires, just chill.

Why did you ask for a larger tire than was on there in the first place? Who needs new tires on a new car? What made it necessary in the first place? I would not have made such a change to a new car in the first place, just because of the unnecessary expense of doing so.

Why did you?

These are winter tires originally from an Audi a5 so I figured they will fit my Audi a4,. so what do you guys think? On or off? :)

Are you sure of the size? The A5 should have had the same tire size as your 2014 A4 - 255/35R19. For winter tires you should consider slightly skinnier tires, such as 235/40R19, which is the size of winter tire I use on my S5. I have to ask - are you sure that the tires you are considering are 255/40R19, and not 235/40R19?

The tires are already installed and yes they are 255/40 r19

The A5 and current generation A4 share the same chassis and drive train (called the "B8" platform in Audi-speak). So given the fact that someone used them on an A5, supposedly without issue, you should have no problem using them on your A4 (other than the speedo and odometer issues already mentioned). Winter tires and quattro are a super combination - when the snow and slush hit you'll be able to drive circles around all those big 4-wheel drive SUVs on all-season tires. Getting a little off topic here, but attached is a picture of my car on a frozen lake in Wisconsin, during an ice-driving school (courtesy of the Wisconsin Badger Audi Club). The difference in control between those cars that had proper winter tires versus those with mere all-seasons was eye-opening.

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