Wheel Hub Spacers - anyone use them?

[wai]

I think its way too much of a generalisation to say spacers are dangerous. Spacers are not dangerous - but some spacers are cheaply made and may crack, and if you use spacers with incorrect bolts well you are asking for trouble.

People have been using spacers on the race track for eons, (where the loads are far higher than on the road) and some manufacturers have used crazy spacers (I'm looking at you Porsche!!!) on factory cars aswell.

As far as the engineering goes, a properly fitting spacer with appropriately long bolts is just as safe as anything else. (Trust me, Im a gingerbeer.... i mean engineer).

But yes its still illegal unless engineered.

There is a big difference between how a race car is maintained and how a normal road car is maintained. Road cars rarely have the bolt torque checked with a torque wrench or any type of mechanical bolt tightener. Also, while you may use longer bolts on the race track, and bolts of the correct grade, it does not follow that road cars will be afforded the same attention. A race car would not pass scrutineering if it was not inspected and seen to be done correctly. Road cars do not undergo the same inspection protocol.

Above all, as you have acknowledged, it is illegal unless properly designed and certified. I have worked on both sides of certification with the DMT approving or rejecting vehicle modifications, and then as a signatory issuing engineering certificates. I would not issue a certificate or accept one for a roadgoing car with spacers, simply because it is not inspected every time it is used. The other thing is that it will make any insurance (comprehensive or CTP) invalid, and this means not only is the modification illegal, but the car is being driven without valid insurance.

On this forum, there was someone who posted a message where the car they were driving had the front wheel part company with the hub because the adaptor had failed. This is about spacers, but the same goes for adaptors for the same reasons.

There will be people who will do what they want anyway. Just remember that it is not just you who can be affected by doing this.

[team_v]

I'm sorry what?

What set of wheels could you get for the price of 4 spacers? I think you've made a bit of a mistake there.

New set of wheels + spacers + longer bolts would be more expensive than just getting a set of new wheels in the correct offset that fits.

If the OP is just after more poke from the standard wheel then 10mm is going to make bugger all difference to performance to warrant the legal issues.

[brad]

The spacer puts additional bending loads on the studs/bolts. Your studs/bolts also need to be longer by at least the thickness of the spacer, otherwise you are not getting the same amount of thread engagement.

If the bolts extend beyond the threaded part of the hub in OEM config & with the spacers they are flush with the threaded part of the hub then the thread engagement remains the same.

If you buy spacers with a hub-centric lip then the bulk of the load is still carried by the hub.

5 or 10 mm might not seem much but the steering offset is generally +/- 25 mm (depending on whether you have a negative or positive offset. A 10 mm spacer can easily change that offset significantly and change the way it responds to steering input. You don't have steering offset issues on the rear, but you do have increased bending loads on studs/bolts.

The effect on steering offset is no different to changing the offset of the wheel either by maintaing the original ET number & varying the width of the rim or maintaining the original width & varying the ET number. VAG group vehicles even vary the offset between models with the same suspension components.

This is much like what Ford Escort and Capri owners would do to their cars. They used to use longer spring shackles for the rear leaf springs so that it gave the car a "nose down" appearance. It did that, but also took all the caster out of the steering. Not a problem at city driving speeds, but on the open highway, the car would be extremely unstable.

It's nothing like changing the caster

Having owned a 1972 Capri with a 40mm lowered front end (Kmac variable rate springs) & long rear shackles (that I fabricated myself) that raised it 50mm in the back I can vouch that there was a change in caster but it was minimal & remained in the positive (about +0.25 deg). It wasn't that hard to mod the strut towers to get it back to +1.5 deg (which was the max factory spec).

It was still better than so many of the pre-60s vehicles that had NEGATIVE caster to help lighten the steering.

If you want a wider track, then the way to do it is with wheels that have the appropriate offset.

But he's just bought wheels.

Mods should always be carried out considering the pros & cons. That's why Mysticality has asked the question. You make some valid points that he should consider but there are work-arounds to all those problems.

[Guest001]

The sad thing is if the questions get asked before buying the wrong thing the problem could be resolved quite easily and legally also

Far too many jump in and find they have done the wrong thing before asking.

[gldgti]

If you buy spacers with a hub-centric lip then the bulk of the load is still carried by the hub.

A digression - but this should never be the case.

The protruding section of the hub (or spacer, or whatever) is necessary only for concentric location of the wheel with the hub and 'ease of use'.

Once the bolts are torqued, the tension of the bolts pulls the mating faces of the hub and the wheel together with enormous force. The friction between the two faces being pressed together so hard is what keeps the wheel in place. This can be proven with mathematics. If you want me to I can do it but I wont unless its asked.

If the bolt tension is too low, then the hub will begin to carry some load because the loading will cause the wheel to move relative to the hub. This will never last for long, since the typical happening is that once the bolts are a tiny bit loose they get even looser and eventually you get a failure.

hope that helps!

[brad]

nice explanation. Makes perfect sense. thx