[Check ID]

Another poster helpfully pointed out to me that the ID.4 has different tire/wheel sets front and rear, thus precluding ordinary tire rotation practices.

Specifically, from the specs buried in the bowels of VWs website:

Wheels :
20-in x 8J in front & 20-in x 9J in rear

Tires:
235/50 R20 104T XL in front 255/45 R20 105T XL in rear

The ID.4 is basically a rear-wheel drive vehicle. I would guess the AWD version, correct me if I'm wrong, will have a computer send power to the front motor as required for traction or power demands (the reverse of a Subaru or most other AWD cars).

I presume that the reason the rear tires are wider has to do the car's basic rear drive design.
(Haven't done the math, but I'd guess the actual sidewall heights are about the same.)

Still, I don't get it. Why would having slightly wider rear tires and wheels be worth disallowing wear saving tire rotations and the near certainty of having front and rear tires wear at different rates, possibly requiring annoying two-at-a-time tire replacements?
After all, we're not talking a monster power car here, like a Vette or a dragster or the like. This is a "family" car.

So what is the logic behind this set-up?
Are there any automotive engineers here who can 'splain?

 

[RocketVol]

I am not an automotive engineer, but I would bet it comes down to gaining every small efficiency they can. The narrower front tires have less rolling resistance than the wider rears and are more efficient from an efficiency standpoint, but less efficient from a getting power to the road point of view. Additionally, a narrower tire will have less aero resistance than a wider one. With all of that said, I believe all of these numbers are small, but they do add up and everything counts. Many high performance cars have a staggered setup, I just wish the ID.4 had the horsepower to be in that category too!

If the clearance allowed you could probably put 255's on the front, but you are above the limit of an 8" wheel with that tire, or buy 9" wheels for the front. A better compromise would be to just change to 245's all around, but make sure you keep the diameters the same as the stock.

 

[ixlr08]

Keep in mind that the rear wheels in addition to providing the push to make the car go, they also do a good deal of the braking. The rears may be wider to take into account the added wear from both modes of operation to even out the wear front/rear.

 

[TT97]

235s can hardly be considered "narrow" for less resistance (the i3 had 155s).

A VW engineer would need to explain their reasoning for the staggered set up but the most common reasons are to promote more understeer (and for looks). If you do want a square set-up, my recommendation is go with 235s in the rear with 10mm spacers. (255 would likely have issues in the front and 245s would either be too large (245/50) or too small (245/45)).

As AWD EVs have separate motors for the front and rear wheels, the ICE thinking of a RWD or FWD converted to AWD does not apply - there is no connection between the two axles. AWD EVs have the ability to send 100% of the power to either axle.

 

[dfox]

I just saw a kid's tricked out Honda Civic today. He had wider tires on the back. No doubt to put down all that power going to the rear wheels!🤣

 

[michael]

ID.4 also has a rearward weight bias, 47/53 F/R I believe. Wider rear tires help control oversteer. The most famous rear weight biased car, Porsche 911, has had staggered tires for decades for that reason.

 

[Huey52]

... and conversely the Audi RS3 (5-cycl.) has wider front tires to promote less understeer in that somewhat nose heavy platform.

The RS3 is AWD with rear bias (despite Haldex Quattro) so in this case the handling was considered more critical than more rear tire grip.

Let's keep in mind that the ID.4 is purported to handle somewhat similar to the GTI so there was design consideration there as well.

 

[Check ID]

Thanks very much for the replies - lots to think about.
If I get an ID.4, I think I'll pretend it's a 911!

 

[Huey52]

Understeer - you see the tree you're about to hit coming at you

Oversteer - you don't see the tree you're about to hit.

 

[BlueDH]

235s can hardly be considered "narrow" for less resistance (the i3 had 155s).

A VW engineer would need to explain their reasoning for the staggered set up but the most common reasons are to promote more understeer (and for looks). If you do want a square set-up, my recommendation is go with 235s in the rear with 10mm spacers. (255 would likely have issues in the front and 245s would either be too large (245/50) or too small (245/45)).

As AWD EVs have separate motors for the front and rear wheels, the ICE thinking of a RWD or FWD converted to AWD does not apply - there is no connection between the two axles. AWD EVs have the ability to send 100% of the power to either axle.

The I3 also has different size tires front to back. The FE tires are low rolling resistance but I agree narrower tires makes more sense to me. The FE was designed as a middle of the road SUV, not a drag car.
Maybe VW had an abundance of wider tires or wheels😉. Or maybe the narrow tires lost traction during braking.

 

[BlueDH]

I just saw a kid's tricked out Honda Civic today. He had wider tires on the back. No doubt to put down all that power going to the rear wheels!🤣

Were the rear wheels skewed out (slammed).
Cvics are front wheel drive.
So, if a tricked out Civic is a ricer, is a tricked out Golf a krauter?

 

[NBCGLX]

Wider tires in the rear help quell oversteer, help with traction, and help with regen braking since all but the hardest braking doesn't use the friction brakes. Many RWD cars have staggered wheels/tires. Some even have different diameter wheels front/rear.

 

[Michael Higdon]

Another poster helpfully pointed out to me that the ID.4 has different tire/wheel sets front and rear, thus precluding ordinary tire rotation practices.

Specifically, from the specs buried in the bowels of VWs website:

Wheels :
20-in x 8J in front & 20-in x 9J in rear

Tires:
235/50 R20 104T XL in front 255/45 R20 105T XL in rear

The ID.4 is basically a rear-wheel drive vehicle. I would guess the AWD version, correct me if I'm wrong, will have a computer send power to the front motor as required for traction or power demands (the reverse of a Subaru or most other AWD cars).

I presume that the reason the rear tires are wider has to do the car's basic rear drive design.
(Haven't done the math, but I'd guess the actual sidewall heights are about the same.)

Still, I don't get it. Why would having slightly wider rear tires and wheels be worth disallowing wear saving tire rotations and the near certainty of having front and rear tires wear at different rates, possibly requiring annoying two-at-a-time tire replacements?
After all, we're not talking a monster power car here, like a Vette or a dragster or the like. This is a "family" car.

So what is the logic behind this set-up?
Are there any automotive engineers here who can 'splain?

Wider tires in the rear help quell oversteer, help with traction, and help with regen braking since all but the hardest braking doesn't use the friction brakes. Many RWD cars have staggered wheels/tires. Some even have different diameter wheels front/rear.

The 235 width front tires are 235mm wide at the tread; the -50 designation is the height of (a single) wall, meaning 50% of the tread width, or 117.5mm high. The rear tires are 255mm wide, by 45% wall height, or 114.7mm wall, a very slight bit less altitude. I'm sure that the car's suspension has been adjusted to enable level driving even with the differential in height, which would be only 5.6mm (less than 1/4") total shorter (including both walls) on the rear. I agree with the (very slight) potential reduction of over-steer but any driver worth holding a valid license should be able to control this; with the AWD version, it's a moot point. It seems a bit silly to design this condition which will eliminate the ability to rotate tires on separate axles. It may cause a worse problem when someone DOES rotate them normally and the car will not track properly.

 

[Huey52]

If the tires themselves are Not directional (?) then they may of course be rotated side to side. Of course that won't even out drive-traction/braking wear. We with RWD will likely be changing rears sooner anyways and as long as you change both on one axle at the same time no issues.

We'll have to be vigilant as to not letting some service advisor rotate them front-back.

... It may cause a worse problem when someone DOES rotate them normally and the car will not track properly.

 

[RocketVol]

The biggest thing to do to help this is to keep up with your alignment. I always buy a lifetime alignment when I get a new car and it pays for itself in the first year and it makes it easy to keep everything going in the right direction

 

[BlueDH]

Another poster helpfully pointed out to me that the ID.4 has different tire/wheel sets front and rear, thus precluding ordinary tire rotation practices.

Specifically, from the specs buried in the bowels of VWs website:

Wheels :
20-in x 8J in front & 20-in x 9J in rear

Tires:
235/50 R20 104T XL in front 255/45 R20 105T XL in rear

The ID.4 is basically a rear-wheel drive vehicle. I would guess the AWD version, correct me if I'm wrong, will have a computer send power to the front motor as required for traction or power demands (the reverse of a Subaru or most other AWD cars).

I presume that the reason the rear tires are wider has to do the car's basic rear drive design.
(Haven't done the math, but I'd guess the actual sidewall heights are about the same.)

Still, I don't get it. Why would having slightly wider rear tires and wheels be worth disallowing wear saving tire rotations and the near certainty of having front and rear tires wear at different rates, possibly requiring annoying two-at-a-time tire replacements?
After all, we're not talking a monster power car here, like a Vette or a dragster or the like. This is a "family" car.

So what is the logic behind this set-up?
Are there any automotive engineers here who can 'splain?

Does the AWD have different size wheels/tires front to back?

 

[ixlr08]

Does the AWD have different size wheels/tires front to back?

Yes