The physical stress that takes place is increased due to the increase lever arm length that results from adding the spacers; the forces increases are great. You also get a decrease in strength of the connection the wheel makes with the hub. Most of what holds a wheel on is not the strength of the bolts that join the wheel to the hub; it is the friction that is created from pressing the two parts together tightly. Now you add a spacer and you get two friction planes with one of them ending up even farther away from the hubs center line. Add both numbers up and you get a much weaker assembly. Changing the width by only 15mms adds many thousands of pounds of force generated from the outside kinetic energy sources. All this increased load really stresses the lug bolts.

 

This is correct. OEM suspension designers (including myself in a previous life) cringe when people talk about spacers. That being said, almost every car has a hub system that is built to be much stronger than is necessary, so you'll be OK driving around town. However, I would not go racing on spacers for any reason.

 

I respectfully disagree. I'm also an engineer and if you look at the amount of metal there, there is no way you are straining anything. We're talking about 15mm not 15cm.

 

Not in one load cycle, but in 1 million, it adds up, even with the most fatigue-resistance hub materials.

 

Does Porsche not make spacers ? Heck I have even seen spacers upto 24 mm made by Porsche

May be Porsche makes those spacers either for museum cars or for street wussies like us

 

I'm sorry but I have a hard time believing this is any more than Internet folklore. The gt3 comes stock with 7mm spacers. I doubt Porsche would put that on an otherwise race ready car if it were not safe or reliable.

 

You mean like the centerlock hubs and lug nuts they sold that loosen in 5000 miles of street driving? Everybody makes mistakes...

The point I'm making is too subtle to come across here.

Your parts are going to be fine in all likelihood, with or without spacers, just as I wrote in the post at the top of this page. The theoretical comments that Engine Guy made are true, that's all I was trying to add.

 

The look is great. I also am not a fan of spacers on a track driven car. I do not have the technical knowledge to support one way or the other. Purchase the correct offset wheels has always been my belief. The look to me does not outweigh function. MK