MAGK944

You've almost concluded that regular hubcentric spacers rather than the bolt-on type are the way to go and I agree. The longer studs will not be under any more stress on a hubcentric spacer. This is the method Porsche used when they added factory spacers to our cars.

Edit: forgot to mention, you will probably have to machine the lip on any spacers you get in order to clear the grease cap, it's a common condition.

ian

Just a point of reference the factory used 28mm spacers, on 72mm studs. Would they have gone all the way to 40mm? Hard to say, would be interesting to know the discussions that went into the spacer decision in Stuttgart back in the day.


And I agree, only worrying about torquing 20 lugs per car, is better than worrying about 40 (especially when it is difficult to check half of them).

tspangle

Thanks, folks. I think I know what I'm going to do now. I'm not going to try to go 40mm, at least for now. If I'm somewhere between 25 and 30mm, that should at least fix my strut clearance issue. If I need to add more from there, I'll consider it then.

MistaX

I'm going to change some words here...
We'll have Bolt on Type wheel spacers, and Washer type wheel spacers...

Both types can be hubcentric, and hubcentric is superior to lugcentric in every sense so lugcentric is not even worth discussing.

The load on a washer-type spacer with long studs has a lot of leverage on the ends of the studs, with the spacer counter acting that leverage on the opposite studs along with the hub. They can shear (or just bend, let's not be too drastic all the time) based on that leverage. Some of the load goes to the hub though, which is why hubcentric is already superior to lugcentric, nevermind all the balancing issues.
Quality and strength of the long studs will be important, along with torquing the lugs correctly. Over-torquing is going to stretch the lugs and make them even weaker. The bigger the spacer, the longer the studs, the worse this issue gets.

A bolt on type doesn't have that leverage issue, but the spacer itself is subjected to force, so a weak or poorly machined material would crack or outright break. A second consideration is the quality of the studs installed in the spacer. Crappy studs will shear no matter what, and there's no way to really say they're any good in any given spacer until they fail, or they don't.
Torquing lugs still important, but the spacer to hub studs are going to be "once and done" so as long as you get that right it'll last until you need wheel bearings next week. The second set of studs, assuming they're OEM quality, would act like OEM studs. Overall certainly heavier because there's just more material and more stuff going on.

There's also a matter of balancing and machining precision for both types... and they both will wreck wheel bearings for the same reasons. Leverage. Bolt on probably more because of more weight.
It's safer not to run spacers at all, but if you have to pick one there's no silver bullet answer. There's plenty of stories of both types failing, but the common theme is over-torquing.

At least that's my understanding of it and I could be completely wrong.

MAGK944

I cannot understand your argument as there is no shear force on lug bolts. The lug bolts, regardless of their length, act only to hold the wheel to the hub. It's the hub that takes all the force in a hubcentric arrangement.

As for spacers, what you are calling "washer" spacers are regular spacers. The bolt-on type are really adapters as that type was first made to adapt say a four bolt wheel to a five bolt wheel and buy design also created a spacer. These days they use the adapter types as a lazy method of fitting a spacer without changing the lug bolts, no car manufacturer does it that way, they all use regular spacers.

MistaX

Only in static weight bearing. That's completely not true in any kind of lateral load situation. For example, you can remove all your lugs and your wheels stay on until you attempt to turn. Not that I recommend trying it.

MAGK944

Sorry but you have lost me completely with your reasoning. There is absolutely no shear force on wheel lugs both statically or dynamically.

MistaX

Then how or why do they break?

Bottom line is either way is going to work, there's a ton of people running spacers, they're relatively safe, treat them with respect and don't air gun your wheels on and you're fine no matter which way you choose to go. The forces it takes to actually rip the studs apart are certainly higher than you're going to hit with an NA 944 on street tires. I just think those forces are lower with super long studs than a high quality bolt on spacer.

But you'll still need wheel bearings more often.

V2Rocket

you never know...yesterday i took off from a light so hard, that the center speaker grille popped out of the dash and ended up in the back seat

JustinL

I've got a pair of 50mm spacers if you want them for $100+shipping.

tspangle

Thanks for the offer, but I ordered some 72mm studs and 1" spacers this morning.

edfishjr

The new BFGoodrich Rival S 1.5 in 225/45-15 is, in my opinion, the best tire you could possibly put on the car on 15/7 wheels. I'm an autocrosser, but I'd use them for the street too, because huge grip and response and not loud like the Bridgestone.

There's also a 245/40 which would work well on 8" wide wheels.

Of course, it's a summer tire.