Changing only two tires

[blame.latitude]

Hi all,

I've been wondering this and haven't been able to find a reputable answer.

My car needs new tires. I am considering replacing only the fronts at this time. I cannot see any reason why that wouldnt work but who knows what the Taycan computer thinks.

The fronts are at 15% and wearing unevenly. However the rears are at 50% and wearing very nicely. Now, in a typical awd car, you have to replace all four tires because there is a mechanical driveshaft which requires the tires to be very close in overall diameter to avoid catastrophic damage. However this doesn't exist in the Taycan.

bit of math: The overall diameter of a brand new 265/35R21 vs a 305/30R21 is very close, 712mm vs 709mm, about 0.04% different. However my current setup with near bald fronts and juicy rears definitely has much more variance than that.

I am not interested in arguments aligned to the basic idea of 'just replace them all to be safe' as that's an obvious answer. The question is whether or not I risk physical damage by replacing the fronts before the rears. Please let me know your thoughts

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[Mad Matter]

Depends on how you look at it but if you have the 21" PZero, the front already have larger rolling diameter than the rear.

I really doubt Porsche took this into account on their tire selections between available 19" 20" and 21" so there's already variable difference in rolling diameters between tires brands and different sizes.

So if you ask a non-expert like me, I think you'll be be fine.

 

[SergeyIndy]

My fronts wear out similar to yours, so I just replaced my fronts at 15k miles, and my rears will last me up to 30k miles. I do not see any issue replacing front and then rear as they wear.

 

[RodeoDrive]

From the Taycan user manual:
- allow no more than 30% thread depth diff on the same axle
- always switch both tires on the same axle
- handling behavior will be affected after changing tires on one axle only, don't be surprised by it

 

[Porsche-Guru]

This issue is not necessarily specific to the Taycan.
On many cars, tyres wear out at different rates and depend on driving style, general car dynamics, tyre types.

As an example, on my last 8 BMWs (a mix of RWD and AWD), the rears have always worn out a lot quicker than the fronts; and each time I have changed only the ones necessary.

The key is to keep tyres on the same axle (whether fronts or rears) with similar wear...

Specifically to my Taycan, I changed the rears way ahead of the fronts; and it is a Porsche dealership that changed them.
The original tyres were all Pirelli Centuratos. When the rears needed replacement - these were Michelin, and the fronts only got replaced after about 6/8 months with Michelins.
So, my car had Pirellis fronts and Michelin rears for a period of time; with different tread wear between fronts/rears - all done by the dealership.

Yes, most dealerships/ garages would love to change all 4 (makes them good money !) - but ask them the legality/ technicality of the decision; and then they likely concede to common sense.

 

[gnr3312]

In Texas the minimum tread is 2/32 of an inch before required replacement, and when I replaced all my tires I had 3 at 3/32 and one at 2/32. Have you officially measured yours with a tread gauge?

 

[Mad Matter]

So, my car had Pirellis fronts and Michelin rears for a period of time; with different tread wear between fronts/rears - all done by the dealership.

This I would advise against to most people unless youre specifically trying to induce a certain type of behavior from your car that you couldn't achieve via suspension settings, aero or weight balance changes.

When tires are mismatched they can cause that axle to behave differently the other.
They heat up at different rates, have different traction breaking points, or behave differently in rain of loose terrain.
Unless you are specifically and intentionally wanting to accomplish this it is really advisable to stick with the same model tire on all 4 corners.

 

[Murph7355]

As others have noted, as long as you change both on an axle you'll be fine.

 

[Speuk]

Hi all,

I've been wondering this and haven't been able to find a reputable answer.

My car needs new tires. I am considering replacing only the fronts at this time. I cannot see any reason why that wouldnt work but who knows what the Taycan computer thinks.

The fronts are at 15% and wearing unevenly. However the rears are at 50% and wearing very nicely. Now, in a typical awd car, you have to replace all four tires because there is a mechanical driveshaft which requires the tires to be very close in overall diameter to avoid catastrophic damage. However this doesn't exist in the Taycan.

bit of math: The overall diameter of a brand new 265/35R21 vs a 305/30R21 is very close, 712mm vs 709mm, about 0.04% different. However my current setup with near bald fronts and juicy rears definitely has much more variance than that.

I am not interested in arguments aligned to the basic idea of 'just replace them all to be safe' as that's an obvious answer. The question is whether or not I risk physical damage by replacing the fronts before the rears. Please let me know your thoughts

the manual is your guide... same axel no more than 30% difference in tread depth, different axels no restriction other than stating the obvious about behaviour with worn tyres.

I nearly always only need to change them in pairs and I have just changed one front tyre following a puncture, remaining tyre had 6mm so ridiculous to bin that.

 

[Flying ace]

Why do fronts wear quicker than rears on this car?

Just checked my tires that had 19k miles, and it has even wear (4/32ns front , 6/32nds rear)

 

[tophamn]

Why do fronts wear quicker than rears on this car?

Just checked my tires that had 19k miles, and it has even wear

The fronts work harder, especially with 'spirited driving'

 

[Breezy]

I have the RWD version and have replaced only the rears with no problems. Rears go faster on mine… no surprise.

 

[Mad Matter]

Why do fronts wear quicker than rears on this car?

On AWD, depending on the bias of the car, the fronts have three jobs, pull the car in acceleration, steer the car and do most of the braking so they tend to wear quicker or at a similar rate as the rear. On RWD cars tires usually work harder as it has to push the car at all times.

 

[Flying ace]

On AWD, depending on the bias of the car, the fronts have three jobs, pull the car in acceleration, steer the car and do most of the braking so they tend to wear quicker or at a similar rate as the rear. On RWD cars tires usually work harder as it has to push the car at all times.

interesting. So I've owned these AWD cars:

1. Lancer Evolution 8 (mechanical transfer case)
2. 2012 X5 (electromechanical transfer case
3. 2022 X5 (electromechanical transfer case)

in all cars, the Evo had the most even tire wear. The X5 had more rear tire wear.

This being a Porsche and knowing the 2022 updated the logic to turning off the front motor in cruising (i can confirm this by watching the diagram on my 2023), I would expect the car to have even or a slight rear bias in tire wear.

I did notice if you did ANYTHING other than straight constant speed cruise, the front motor would turn on.

 

[Mad Matter]

Most of the the tire wear occurs when you're breaking the coefficient of friction of the tire against the road, during coasting you have rolling resistance and the forces acting on the tire are lower than the forces needed to accelerate a car or stop it.

The weight of the car and alignment specs also play a part in comparison to your previous cars. the Taycan has pretty "aggressive road" alignment settings form factory.

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