Technically the offset is the distance between the center line of a wheel (any size rim) and the mating surface of the wheel/hub/rotor. The width of the rim is not relevant. If you are talking about the variation of the distance between the edge rim (not tire) and the mating surface, then you have 1/4" for the extra. As far as the tire extra clearance needs is just 5mm (each side) from 295 to 305. But that matters not when it comes to OFFSET discussion. The wheel center line and the tire center line are one and the same, so the only difference is 5mm on each side for the tire and 1/4" for the rim (they do not combine). In effect the only possible wheel movement is that fixed 5mm plus or minus the offset (ET)

 

Think about it: Both sides of the wheel will be extended by 1/4" (~6mm) on 1/2" wider rim. Therefore if the positive offset is reduced by 10mm, the total additional extension is 16mm. The illustrations show this. Use the tire rim calculator in the Tools tab above and that will corroborate this.

 

BOTH SIDES of the wheel is correct, I agreed with that. The nominal tire width change is 10mm, so from the centerline, the tire extends an extra 5mm on each side.

11" is 279.4mm (still less than the 305mm of a 305 tire)
Add 5mm. of aluminum on each side where the bead sits, you are at 289.4mm, still less than the 305mm of the tire so interference of the wheel itself is not a concern.

What I think you are trying to say is that with a 10mm. offset change plus the 5mm of the tire, you are pushing out the wheel face by 10mm. but because of the tire swap, the tire's edge itself will be 15mm. more outward than an OEM 295 using the stock 38mm offset.

You cannot possibly think that because the tire beads sit further apart, the 305 will be wider. The tire is always wider than the wheel it mounts on (except for the stupid looking lowrider stuff).

 

I was not factoring tire size into the equation. I was simply calculating the location of the outside wheel face relative to the hub face. Since the 305 is about 1/2" wider than the 295, the 305 will not extend beyond the 11" wide wheel face any more than the tread of the 295 will on a 10.5" wide rim.

 

Unhingd - I think you must be right - the SVR rear axle is wider than the R hub-to-hub, which is why the maelstroms are so tucked in when they are fit to an R.

I found the following statement in an early article explaining differences between the SVR and other F Types:

"Anti-roll bars are five per cent softer front and five per cent stiffer rear, all-new (and very trick looking) rear suspension knuckles permitting larger, stiffer rear wheel bearings and significant increases in toe and camber stiffness."

Perhaps the rear axle is the same length, but the wheel bearings are thicker (and stiffer) on the SVR. If I'm not mistaken, this would have the same effect as fitting a spacer/adapter?

 

 

If you search back, I had a new set of SVR wheels but never mounted them and asked if I could sell them to somebody with an R. I received a number of replies that the offset was the same. I sold the wheels and the person with the R was very satisfied. I think we should check the rear track dimension perhaps

 

Agreed. We need to know this.

 

Track on sample V6S AWD is 64.9"
Track on SVR - 63.4"
Odd to say the least but now undesrstandable.
Track is affected by wheel offset as it's measured between the centerline of the rear wheels.IN theory it's the distance of everything between the two rear mating faces of the rotors + or - the offset.

1.6" difference = 40.64mm difference

 

To add confusion apparently the rear track on the 2019 R is 64.1 so it lands right in between those two (also depends on actual wheels). What's interesting is that the more powerful drive trains have more narrow rear tracks.

 

I will go check if the axles are the same part #

 

For purposes of the wheel discussion we were having, the measurement we really need for the cars is from hub face to hub face, not track.

 

Track is hub face to hub face + or - 2X offset... Since offset is under discussion

 

Of course you do know the rear wheels are different from the front. I have a 2017 SVR and have the same wheels.

 

Just note that this thread is almost 4 years old...So likely not going to get responses or discussion on the topic. Been dead for a while...

DC