Wheel Spacers - How Much Is Enough?

[Taso84]

really? i would have thought the mounting surface being closer to the centre of the wheel (where the load is spread more evenly each side) would have been beneficial.

2 points here, biggest cause of failure there is from harsh bumps in the road, not from cornering force, here the car sits static with almost always negative camber, this means staticly there is more force on the inside of the wheel, and when u hit a bump the suspension compresses, causing more dynamic negative camber, putting even more stress towards the inside of the wheel.

so if the stress here is put on the inside of the wheel, putting the mounting surface closer to the inside of the wheel, or at least closer to the middle, means the load is spread more evenly at the mounting surface, and there is less leverage.

Nisskid, agree with you that more stress may be caused by harsh bumps rather than cornering force since they are more dynamic and therefore require less force for failure - but not really sure since haven't measured it. Ive however heard of this type of failure happening more on the track (where u'd expect more cornering force) rather than on the street (where you'd expect more bumps) but could be wrong.

This failure is caused by the fact that putting an unsecured spacer on ur wheel changes the point at which the force hits the hub whilst not changing the point of bending. So where as the shear force is not larger, the bending moment will significantly increase and hence cause extra stress which will more likely result in shear failure. Here is the very rough diagram showing this:

Note the rectangles are the hubs not the wheels. The horizontal 5 lines are the wheel studs and the vertical line is where the wheel force is applied to the studs.

The letters in blue/red are forces and in black distances. Forces calculated assuming an applied force of x kN from the wheel.

Note that in this very rough sketch and i have approximated with the wheel load being a point load (x). As u increase the spacer size (from y to z) you get a linear increase in bending moment. In reality, this would be a distributed load, so the bending moment would really increase by a factor of the distance squared. ie if you x3 the distance, its x9 the bending moment.

Edited April 23, 2009 by Taso84

[nisskid]

i think i get what ur trying to say, but it looks like ur talking about slip ons, not bolt on spacers? but yes, slip ons do add more leverage to the sheer force placed on the studs.

but i think if u look at the original post by mid life crisis, he simply refers to pushing the wheel out further, no reference to spacers, so im assuming he meant simply lowering the offset/increasing the track.

i personally wouldnt reccomend slip-on spacers any bigger than a few mm, the hub ring usually protrudes around 5mm, so unless ur using hubcentric slip ons (fairly rare) u lose ur hub at anything from about 4mm and over, and ur wheel is no longer hubcentric, that placed with the extra load we were talking about before, ur asking for trouble.

[Spunky Munky]

Thanks fellas....I think I might just leave my rims as they are and get rims with a bigger offset when the time comes.

Thanks all.

[joeyjoejoejuniorshabadoo]

i think i get what ur trying to say, but it looks like ur talking about slip ons, not bolt on spacers? but yes, slip ons do add more leverage to the sheer force placed on the studs.

but i think if u look at the original post by mid life crisis, he simply refers to pushing the wheel out further, no reference to spacers, so im assuming he meant simply lowering the offset/increasing the track.

i personally wouldnt reccomend slip-on spacers any bigger than a few mm, the hub ring usually protrudes around 5mm, so unless ur using hubcentric slip ons (fairly rare) u lose ur hub at anything from about 4mm and over, and ur wheel is no longer hubcentric, that placed with the extra load we were talking about before, ur asking for trouble.

i run 3mm slip-on's to clear my breaks on the fronts...

i had custom spiggots machined up

[mitchy_]

this is a mates car... 18x9.5 +13, with 235/40R18 front and rear.

[joeyjoejoejuniorshabadoo]

^ and some camber...

rears look tough

[mitchy_]

has about -2 degrees.

[nisskid]

that's how it's done

[tets]

was gonna put it on the rear but i fail had a 255 on it

prob go 215 and throw it up the fronts. 9" rim

car is still sitting on jack in pic below

looks alright on fronts but tires are a bit to wide.

[mosoto]

has about -2 degrees.

And totally illegal in WA. I personally would not want to draw too much attention from the law but each to their own.

Edited May 2, 2009 by mosoto

[nisskid]

o no! it's illegal!!! now cops will defect my car unlike before where they just would have let me off!!

[Dal34]

^^ Rofl.