Weird Spacer Problem

Got a very strange spacer problem on the front of my C4S and I feel like I've tried everything to sort it including taking them off! Basically I get a judder at 70-80 mph when they're fitted. Yeah I know - wheels need balancing but I've tried that. Absolutely nothing at all without them on but as soon as they're on it comes back. The spacers are perfectly flat and true, the faces of the wheel and disc are both clean and flat, the wheels are balanced, I've tried the spacers both ways round, swapped sides etc and I just can't work out what's causing the vibration. Anything I may have overlooked or anything I can try? It's one of those things that I'm not that bothered about having them on, but it is doing my head in what could be causing it... :?: Any ideas?

Difficult .. Your issue is the wheels cause a vibration ( steering shake ) at high speeds but only with the spacers fitted . With spacers you are moving the spinning mass further away from the center point .. a small imperfection will cause a larger vibration the further it is moved away as it in a sense becomes a larger mass . A small imperfection on a thin close in spinning mass is far worse the larger the mass becomes and the further out it is . Quickest option is obviously to remove the spacers . As to the issue .. a surface may seem flat but unless measured might not be .. You have the discs .. the spacers and the inner surface of the wheels , wheel balance ... you also have a sticking caliper but on Porsche that's a bit unusual . Wheel balance and there are two ways of doing it .. one relies on the inner surface being true .. the other doesn't .. you clamp the wheel from the outer side onto an inner cone and not a cone on the outside against a flat plate . If a wheel balance issue then i feel it would be present regardless of spacers fitted . You could try testing with just a single spacer fitted to each side in turn.. try to identify if its a single side that's causing the issue ... i suspect it is . You would need to check the suspension for play .. wiggle wheels top and bottom each side . I would also remove the discs and check the inner face .. this also needs to be flat . Best guess atm is a brake disc one side or suspension play .

Are they hub centric meaning they have a step that locates onto the hub and into the center bore of the wheel. If not and you're using the standard Porsche bolts which have a collar which can move slightly means the wheel can be mounted very slightly off center Mac

Also even if they are hub centric the spacer needs to be a tight fit on the hub and into the center bore of the wheel. Any side to side wobble can cause vibration. As already mentioned everything needs to be clean and flat. Sometimes tightening the bolts with the wheel in the air can help, have an assistant hold the brakes on. Sometimes even with perfect fitting spacers the new offset can cause vibration if the suspension bushes or joints are passed their best. I've seen hub centric spacers where the inner bore was 0.5 mm bigger than the hub and that was enough to cause vibration. I have a strange issue on my turbo. I run girodiscs on the front, the center bore of the disc is bigger than the hub so it's the two small countersunk Allen bolts which keep the disc central. I find over time the the braking forces makes the disc slip between the wheel and the hub and I start to get vibration, when I remove the Allen bolt I find they have bent. I replace with new and the vibration goes for a while. I'm sure this is not your problem but it does illustrate that things only need to be very slightly off center to get a vibration Mac

I had exactly the same thing a while ago. My old spacers were not hucentric they were flat. Changed them for hucentric and problem solved instantly. They are slightly off centre.

Thanks gents. They're only 5mm spacers so I wouldn't have thought they would push the wheel out enough to make that much of a difference to the offset - or is that totally wrong? Being 5mm they're not hubcentric and I've tried doing the bolts up with the car in the air, on the ground and halfway between (wheel touching the ground but weight of the car off the ground). I've tried absolutely winding the bolts in then backing them out one by one and torquing them like that. The one thing I was wondering could be the issue is the bolts - they came with the spacers and are the radius type with the spinning collar, could these be the issue? I have been tempted to stick the standard bolts in just for a quick road test just to see but not sure if that would have any effect?

The problem I had was with 5mm flat spacers. It's nothing to do with offset. They are just slightly off centre. Doesn't matter what you do, they will always cause vibration. Bin them.

Oh and no. It's not the bolts mate.

Do you get 5mm hubcentric spacers? I looked around before I bought these but never managed to find any...

I'm not sure mate. I just fitted 10mm hucentric at the time. Looked better and smooth as you like.

Any rubbing issues mate? I bought my 15mm rears off a guy that had had them on the front of his and had rubbing issues....

Depends on your offset mate. I'm on 997 rims on 996c2 so there is plenty of scope sometimes some tyres allow a bit more space under the arch.

If you use bolts without the spinning collar, and tighten them evenly with the wheel in the air then there's no reason the wheel shouldn't sit perfectly centrally with just the flat spacers. Lots of people on here run 5mm flat spacer without problems Mac

Ok I'll give the bolts a try and report back.

A 5mm spacer isnt large enough to push the wheel off the hub flanges, so shouldn't need to worry about hub-centric. Have you checked the bolt lengths? Are they actually 5mm longer than the standard bolts? What torque are you tightening the wheel bolts too?