Hi all,
Rookie question here, will the JAGUAR XE 19 " Star Wheels fit the XJ X351, 11 plate, 3.0 diesel, was thinking on buying a set for winter and I quite like the 5 double spoke shape of this alloys.

The XE 19' alloys are:

• front: 7.5J ET45
• rear: 8.5J ET55

The XJ 19' alloys are:

• front: 9J ET49
• rear: 10J ET46

Or so I believe.
And if you reckon they will fit will they look alright or quite silly. Thank you!

 

Nope, bad idea

 

Bcrd13, the fronts would probably be ok, it is the rears that will give you the biggest grief. The 10mm difference in the offset can lead to issues with bearing wear. I personally would not run those rims as they are too narrow for the XJ and would lead to handling issues due to lack of traction.

 

 

Langstraat, actually for winter tires, you want something more narrow. A narrower tire is going to apply more pressure per unit of area. Therefore, when you are driving through snow, you are going to compress it more, giving the car more bite. You can liken this to wearing boots and snow shoes. With boots, your feet sink to something solid. With the snow shoes, you float on top of the snow. The only reason that snow shoes are preferred for people walking is that there is minimal power to force the snow shoes around and down into the snow.

 

Why would the extra 10mm be an issue. People regularly put 10-15mm spacers on these cars with no issues. Isn't it geometrically the same?

Also (surprisingly) the XE and XJ are similar in weight - the bigger engined XE is around 3800lbs and the XJ runs from 3800-4150lbs

The 5.0 V8 might have traction challenges but I'd have thought a mid powered diesel wouldn't need that

Not saying it's a good idea. Just wanted to better understand the concern

 

All I can add to this is that anytime I have been at my dealership and in the service area and heard really loud banging is when they where changing wheel bearings on XJs that had non OEM wheels that didn't have the correct offset. The techs have said this was the only times they have had blown wheel bearings.
Front wheel Offset 20” - 9J, 49 offset
Rear Wheel Offset 20” - 10J, 46 offset --XJR 44 offset

 

When it comes to offset, this is a fixed value that is desired based on how the car was built. In short, offset is a reference number between the surface of the hub and the centerline of the bearing (on the car side). to the best of my knowledge, no one changes these parts on their car. In an ideal world, you want the center of the rim in line with the center of the bearing. This ensures that there is minimal side load on the bearing. The bearings on a car are based around handling up and down forces (ie, hitting potholes and the weight of the vehicle) and not so much on the side forces (like what a tire experiences when making a hard turn, the car is physically trying to twist the tire under the car). By getting the offset wrong, you are constantly keeping a side load on the bearing. You can see this first hand by taking a screw driver (the longer the better) and say a 5 pound weight. For the sake of doing this, your hand is the bearing, the weight is the weight of the vehicle as seen at the center of the rim (side to side), and the screw driver is the forces that the car is seeing. If you tie a string thru the weight and slide it on to the handle of the screw driver and you center the weight under your hand, all the force that your hand has to overcome is that of the weight. Now, put your hand on the handle, but, move the weight to the end of the handle (so the string is at the edge of your hand). Feel how the screw driver is trying to twist out of our hand now. The further down the screw driver you go, the more twisting that your hand has to overcome because your hand is not in line with the weight. This is what the bearing experiences. A bearing is only designed to handle so much twisting. Kinda like your hand will only allow you to slide the weight down the screw driver but so far before you can't prevent the screwdriver from twisting and letting the weight slide off the end. Now imagine if I was standing there as you were holding the weight with it not directly under the center of your hand and then I take a metal bar (representing a pot hole) and start tapping weight. The twisting becomes that much more. If I was to do the same thing but with the weight centered under your hand, it would be much easier to control.

In the case of spacers, this can make things better, it can make things worse. It all depends on how the rim was built and what is needed for the car. First, keep in mind that offset is the distance between the face of the rim that touches the car hub and the centerline of the rim (side to side). If the face of the hub is more towards the outside edge of the rim (in relation to the center of the rim), then this would be a positive offset. If it was more towards the inside edge of the rim, then this would be a negative offset. So, if you had a rim that had a +60 offset on the front rim and then added a 10mm spacer, you would have effectively made the hub surface at +50mm, which is almost ideal (ie, the spacer moved the surface where the "rim" would touch the car now be at 50 mm from the center of the rim). Where if you can a rim that had a +40 offset and then added the same 10mm spacer, this would then make the offset effectively +30mm, pushing it further from the ideal offset, making the stresses become even worse.

Please note that tire width does not play into this as the tire will center itself on the rim, putting the center of the tire in line with the center of the rim.

Hopefully this helps explain what is going on when it comes to potential problems with changing the offset that the factory rims have and the reason why getting too far from stock can have negative effects.

 

Thermo, Very well explained!