Factory spacers on the GTS

[aajami]

Sorry if this isn't news to most, but...

Thanks to a little bit of research from Ralf (Checkcaptain), Ian (alpina527), and Byron (beedub) it's been determined that that GTS wears 5mm spacers on the front wheels (no spacers on the rears) in order to clear the front springs. Based on previous posts by Tom @ EAS and rldzhao, I've been under the impression that the minimum spacer size that will fit our hubs is 12mm. Any idea how BMW was able to fit a spacer so small on this car? The GTS also has a stud conversion from the factory -- is this the answer?

Would love a bit of clarity from our resident suspension experts.

[808E90]

I've ran 5mm spacer on my stock hub ... No problems.

[aajami]

Here's the thread that from LMBM3 (I miss him) where he explains where anything less than 10-12mm spacer is not recommended for our cars:

http://www.m3post.com/forums/showthread.php?t=307901

[808E90]

Those spacer that are pictured next to the hub centric spacer look like universal ones ...

The problem with running universal spacers is that they do not sit tight around the hub. The reason you want to go with a 10-12mm spacer is because it will extend the hub (where the wheels sits on).

For those that want to run a 5-8mm spacer and are concerned about the amount of area (hub) that the wheel will sit on you can always get these:
http://www.turnermotorsport.com/p-21...ders-pair.aspx

[tom @ eas]

Originally Posted by 808E90

Those spacer that are pictured next to the hub centric spacer look like universal ones ...

The problem with running universal spacers is that they do not sit tight around the hub. The reason you want to go with a 10-12mm spacer is because it will extend the hub (where the wheels sits on).

For those that want to run a 5-8mm spacer and are concerned about the amount of area (hub) that the wheel will sit on you can always get these:
http://www.turnermotorsport.com/p-21...ders-pair.aspx

The hub extenders will not fit the e9x M3 hub since they have a tapered ID.

Originally Posted by aajami

Sorry if this isn't news to most, but...

Thanks to a little bit of research from Ralf (Checkcaptain), Ian (alpina527), and Byron (beedub) it's been determined that that GTS wears 5mm spacers on the front wheels (no spacers on the rears) in order to clear the front springs. Based on previous posts by Tom @ EAS and rldzhao, I've been under the impression that the minimum spacer size that will fit our hubs is 12mm. Any idea how BMW was able to fit a spacer so small on this car? The GTS also has a stud conversion from the factory -- is this the answer?

Would love a bit of clarity from our resident suspension experts.

There might be a tiny bit of confusion.

Spacers 10mm or larger should be hubcentric. Most 3mm & 5mm spacers do not need to be hubcentric since the stock lip (11mm) has enough to protrude the wheel centerbore. Most 10mm, 15mm 18mm and 20mm are hubcentric, allowing the wheel to properly center itself to the hub and prevent vibration.

Stud conversions simply allow easy wheel removal at the track as well as eliminating the need for specific lengths for different spacer thicknesses.

[alpina527]

Originally Posted by tom @ eas

The hub extenders will not fit the e9x M3 hub since they have a tapered ID.



There might be a tiny bit of confusion.

Spacers 10mm or larger should be hubcentric. Most 3mm & 5mm spacers do not need to be hubcentric since the stock lip (11mm) has enough to protrude the wheel centerbore. Most 10mm, 15mm 18mm and 20mm are hubcentric, allowing the wheel to properly center itself to the hub and prevent vibration.

Stud conversions simply allow easy wheel removal at the track as well as eliminating the need for specific lengths for different spacer thicknesses.

The stock hub is 10.6mm long with a .8mm chamfer on the end which gives 9.8mm of location diameter (72.5mm)

BMW wheels have a 6mm x 30 degree lead chamfer which means anything over a 3.8mm spacer has no location on the wheel spigot.

[Eddy@ApexWheels]

5mm spacers are fine in most cases as they can keep the car 100% hub-centric. It seems there is a LOT of misinformation about what hub centric really means, and how spacers effect a hub centric fitment.

Just because 5mm spacers do not have an extended hub, does not make the wheel assembly non-hub centric. As long as hub material is making contact with the center bore, the assembly will remain hub centric, and in most cases a 5mm spacer works as there is enough of the factory hub sticking through, that everything remains centered.



Hub centric means the hub keeps the wheels centered. The lugs hold the wheels to the car. This is important to understand, because the hub itself holds very little load on it's own. It's simply a guide to keep the assembly centered as there is a lot of slop and play with BMW lugs. Many cars on the other hand are lug centric. Meaning the hub is meaningless and the lugs don't have the same slop. They can center the wheels on their own. Two different designs, both work. BMW chose one.

The important thing to remember about the above is that the hub on a BMW only has to keep things centered, which is not a complex task. To do that, it only needs a few millimeters of contact with the wheel. Most BMW hubs have about 10mm of hub extension. If that sticks into a wheel 10mm, then you can use a flat spacer so long as there is still a few millimeters of material making contact with the wheels center bore.

Some wheels have a chamfered edge on their center bore, while others don't, and that chamfer can very in depth as well. That has an impact on how deep the hub has to reach to make proper contact with the center bore. In most cases a 5mm spacer will still have a few millimeters of center bore contact even on a wheel with a chamfered center bore.

An 8mm spacer on the other hand would not leave enough hub to keep the wheel centered since most wheels have a chamfered edge that is a few millimeters deep, that would make it impossible for the remaining factory hub material to make contact with the wheel. Because an 8mm spacer is flat (no attached hub extention) people tend to pool them all together and make generalizations.

The spacers shown in that thread above are NOT a universal spacer. They are still a bmw specific spacer as they are 5x120. It doesn't need an extended hub, as the factory hub does that work, and it would be impossible to create 5mm spacer with an attached hub.

In Summary:

The chamfer of your wheels are the determining factor of whether or not a 5mm spacer will work.

[signes]

Great write-up.

[Beedub]

great post paintpro......

[alpina527]

Originally Posted by Beedub

great post paintpro......

Yes great write up, but the 359m wheel in question has a 6mm deep chamfer.

The stock GTS spigot has 9.8mm of effective location. Add a 5mm spacer and the wheel isn't locating properly. In fact it's 1.2mm short of getting any location at all.

That is why we are trying to work out how the 5mm GTS spacer is working

[Eddy@ApexWheels]

Originally Posted by alpina527

Yes great write up, but the 359m wheel in question has a 6mm deep chamfer.

The stock GTS spigot has 9.8mm of effective location. Add a 5mm spacer and the wheel isn't locating properly. In fact it's 1.2mm short of getting any location at all.

That is why we are trying to work out how the 5mm GTS spacer is working

I didn't read your earlier post before I put mine up. Where did those numbers come from? We'd really need measurements from a GTS with the actual wheels and spacers mounted since the factory was willing to do it, and I'm not hearing about vibration issues. I wonder if something is slightly different.

[alpina527]

Originally Posted by paintpro21

I didn't read your earlier post before I put mine up. Where did those numbers come from? We'd really need measurements from a GTS with the actual wheels and spacers mounted since the factory was willing to do it, and I'm not hearing about vibration issues. I wonder if something is slightly different.

Yes, that's what we are trying to find out. We are assuming the hubs are regular M3 and the spacers are 5mm and only fitted to the front which isn't a good idea with 359m's on a stock hub without additional location.

It would be great to get some actual photo's of the GTS spacer setup to see what's going on in there. Can you help?

[Ant Man]

It does have a small spacer up front







Top pic not great. I'll try and take another tomorrow.

[aajami]

So is it safe to assume that BMW eschewed bolts on the GTS in favor of a lug-centric setup in order to allow the use of a spacer with a 359M?

[Technic]

Originally Posted by paintpro21

I didn't read your earlier post before I put mine up. Where did those numbers come from? We'd really need measurements from a GTS with the actual wheels and spacers mounted since the factory was willing to do it, and I'm not hearing about vibration issues. I wonder if something is slightly different.

Yes.

If the factory is using 5mm spacers with the 359M then the logical conclusion should be either the GTS hub is not 9.8mm or this GTS 359M center bore does not have a .8mm chamfer.

I think that the factory knows a little bit more than any of us combined.

[enricob]

i have H&R 10mm spacers like the right one



are they ok ???

[alpina527]

Originally Posted by enricob

i have H&R 10mm spacers like the right one



are they ok ???

No, they are definitely wrong. You need some like the ones on the left

[ADV.1 Matt]

Good info in here guys. I'm very surprised that the GTS would be wearing spacers.

[enricob]

Originally Posted by alpina527

No, they are definitely wrong. You need some like the ones on the left

[aus]

Originally Posted by ADV.1 Matt

Good info in here guys. I'm very surprised that the GTS would be wearing spacers.

Apparently, the wheels are a motorsport wheel they already had available and they didn't want to make a new wheel for a few hundred cars.

[ADV.1 Matt]

Originally Posted by aus

Apparently, the wheels are a motorsport wheel they already had available and they didn't want to make a new wheel for a few hundred cars.

Yea, understandable.

[aajami]

Originally Posted by ADV.1 Matt

Yea, understandable.

Apparently the 1M Moto GP pace car is also wearing 5mm spacers on the fronts as well.