Spacers: what are the mechanical drawbacks?

[SamS]

Hello,

I asked this on the eas - Macht Schnell wheel spacer reference thread but realized it is probably best left to its own discussion. I'd love to get some feedback from those of you here that are really careful about the engineering and geometry of the stock M3.

What are the drawbacks, from a pure engineering/mechanical standpoint of adding spacers?

Obviously, there is some additional weight, but that has to be minor. By moving the fulcrum of the wheel/suspension point out ~15mm, what else are you impacting? I have to think that camber angle becomes more aggressive with spacers.

What about EDC settings? I always assumed EDC is finely tuned for the factory geometry. The spacers would almost certainly impact that in some way.

If you're only the occasional track user, or are concerned about the long-term effects on the stock suspension, is this all too much thinking about nothing?

[M14]

Theoretically, it affects everything. But realistically, a 15mm spacer is not going to have any measurable impact on anything except wheel/tire fitment.

[SamS]

So, can we assume any negative mechanical effects are offset by the (supposed?) improved handling due to increased track?

If so, spacers would be a pure cosmetic upgrade?

[alpina527]

They are mainly cosmetic, but it does give a wider track which helps handling in theory. They also make the springs slightly softer

The main use in racing is to enable wheels to clear big brakes.

[tom @ eas]

Originally Posted by SamS

Hello,

I asked this on the eas - Macht Schnell wheel spacer reference thread but realized it is probably best left to its own discussion. I'd love to get some feedback from those of you here that are really careful about the engineering and geometry of the stock M3.

What are the drawbacks, from a pure engineering/mechanical standpoint of adding spacers?

Obviously, there is some additional weight, but that has to be minor. By moving the fulcrum of the wheel/suspension point out ~15mm, what else are you impacting? I have to think that camber angle becomes more aggressive with spacers.

What about EDC settings? I always assumed EDC is finely tuned for the factory geometry. The spacers would almost certainly impact that in some way.

If you're only the occasional track user, or are concerned about the long-term effects on the stock suspension, is this all too much thinking about nothing?

The M3 needs to satisfy a wide audience. Tuning (whether it be engine, suspension or braking) is performed to suit one's needs.

The GT4 for instance, uses spacers and offers them as a BMW Performance part through authorized dealers (fixed widths for the BBS).

Spacers have no effect on EDC. Whether it be pulling the wheel a bit from coilover adjustment collars or a BBK, or those looking to bring the wheels flush to the fenders for a more aggressive stance, these are a quick way to chance the appearance of your M3 in under an hour.

BMWs are not the only vehicles to utilize spacers, they are very popular in the Porsche and Ferrari applications in gaining extra track width (some as much as 80mm total). With the minimal amounts we're discussing about on M3 applications, I doubt this is even an issue to really be concerned about.

[kitw]

Scrub radius. This is the biggest negative, you end up changing steering feel and possibly adding bumpsteer and additional feedback from bumps.

There will be an additional load on the lug bolts/hubs, but VERY small.

[SamS]

Thanks for all the responses so far.

This is the first I've heard of scrub radius. It is obvious that spacers will add positive scrub radius, but is it enough to make the M3 scrub radius > 0? These are things I don't know.

http://en.wikipedia.org/wiki/Scrub_radius

[kitw]

The M3 has zero scrub radius, stock, and spacers on a MacPherson strut will usually give you exactly that amount of positive scrub radius.

[SamS]

Very interesting!

[Tonifyd]

I've heard dealers voiding warranties b/c of spacers. True/False?
Are you confident with spacers that you would track your cars with them as well?

[tom @ eas]

Originally Posted by Tonifyd

I've heard dealers voiding warranties b/c of spacers. True/False?
Are you confident with spacers that you would track your cars with them as well?

I haven't seen once case of any warranty disputes with spacers to date. Stick with a quality brand and you should be fine.

[drburton]

I warped my front rotors and they were replaced under warranty by my dealer. However, the SA said that this was a one time deal and pointed to the spacers as voiding the brake warranty. Ultimately, if I have additional brake issues I'm not sure if that argument would hold up but that is what they told me. In my mind the spacers had nothing to do with the problem, just the dealer using any excuse to not cover the brakes going forward.

[Tonifyd]

how hard would it be to remove the spacers before a dealer visit?

[takashin]

Originally Posted by Tonifyd

how hard would it be to remove the spacers before a dealer visit?

If you can work a jack and take off a tire it takes about that long.