Wheel offset Vs Bearing load

[30psi 4agte]

At what point does the offset of your wheels effect the bearing load on your diff ?

IE how far can you space / offset your wheels out (towards guard) before you will be changing bearings due to excessive loading ?

I did abit of googling to find some info specifically aimed at the E sieries falcon diffs but didnt find much..

I found mention of a bearing load calculator but no calculator

Any ideas....

[IN 05 NT]

very interested to hear this too!

[roadsailing]

as far as i know, both from research and logic, bearing load is never a problem due to offset on live axle suspension. if you thnk about the way an axle sits inside the diff, it is fairly easy to see why. a front wheel will have to counter the extra torque over a small distance (cantilever attached to the spindle) but a rear axle is very long by comparison, so wont be affected too much.

this is why oldish racing cars would run high neg offset wheels on the rear and regularish ones on the front.

[CrUZida]

Have a look at all the jap VIP cars running -20 offset rims, they are all designed for +50 rims.
I doubt they have many issues with bearing loads.

However, the standard setup will probably quite easily do half a million km's if not more when looked after properly.
I doubt many of the VIP cars have done more than 100k kms though, so longevity is hard to measure.

I guess what I'm getting at is that yes, the bearing load is changed, and yes the bearing life will be shortened, but by how much I don't know.
I'd say that with new bearings it'd be highly unlikely for them to fail within a few years (unless you are a taxi).

And as Shiny pointed out, the affect on a solid axle would be much much less than the affect on IRS.

[EldarO]

so would it be safe to say that an evenly spaced wheel (0 offset) would (making an assumption) be evenly loaded and thus give the greatest life?

or would it be the higher offset that gives longer life (all in theory of course), having the majority of the wheel behind/underneath the mounting face?

[roadsailing]

so would it be safe to say that an evenly spaced wheel (0 offset) would (making an assumption) be evenly loaded and thus give the greatest life?

or would it be the higher offset that gives longer life (all in theory of course), having the majority of the wheel behind/underneath the mounting face?

no, lowest load would be when the wheel centreline is in line with the centre of the bearings, with zero camber on a flat road. zero offset with respect to the bearings, yes but zero with respect to the hub face, no.

depends on a lot of things

[CrUZida]

The greatest life will be given by using the offset that the hub was designed for.

For instance, older Falcons were designed for a +6 offset. So a +6 offset will give the greatest life.
Commodores were designed for a +40 offset (could be wrong, but its around that), so that offset will give the greatest life.

[Joshstix]

The worry with a basic live axle setup isn't really about bearing load from my understanding, more about snapping the axle at the bearing. Since you're increasing the lever operating against the axle where it is supported at the bearing.

[roadsailing]

^^^^^

yeah what he said too, more -ive offset will definately increase bending load on the axle flange and tension on wheelstuds etc

[CrUZida]

I've had a passing comment from my engineer regarding that scenario, and he said he did some calcs and it was only a small % increase in load on the bearing.
However, I don't know what increase in offset he did the calcs for.

[MR 1JZ]

*wonders how much his 9" wide +5 wheels and 4.5 degrees of neg camber will affect wheel bearings*

lol

[Rex_Kelway]

Rex believes also in the idea of:

"It will shorten the life, Yes. But by any CONSIDERABLE amount?"

IE if your car was going to do 500,000km on the stock bearings, who cares if it does 'only' 100000km on a set of new bearings...

Also, remember if you buy new quality bearings, the manufactring processes and materials quality have also improved markedly over your stock items if they were manfactured last ice-age.

Basically get new wicked bearings and replace them at the first sign of trouble, like a responsible dog-boner.

As a more technical answer: The old "How to make your shitbox drive good" by Fred Phun suggests that only at about 25mm less offset than standard will bearing life/safety suffer by any considerable amount. This book was first written about 30 years ago, so His idea of bearing quality stands...


Oh and, Mr1G

How Nissansilvia.com that post was...

[Draven]

I just had a great visual of you taking a dog from behind.. thanks Rex

[Hiro]

It'll probably also come down to how over-engineered the stock bearings are. When I was designing the hubs and axles for the 2005 UN FSAE car, the design of my hubs meant that I had roughly a safety factor of 5 on all my bearing loads. They were so ridiculously over-strong for their application, but that was due to the size required (we didn't have an axle, just a hollow hub, with the bearings on the outside of the hub). However, there was only a safety factor of 1.5 or so on the speed rating, but that was fine since it was highly unlikely the wheel speed could get over 180km/h (gearing took care of that)

[30psi 4agte]

Well my rims are -7mm 0ffset + imlooking at running 25mm spacers so thats -33mm

Some Offset !

I guess like what has been stated : IT will shorten bearing life ....but to what extent who knows. If i get 100,000 km out of em ill be more than happy.

P.S No talk about spacers and running excessive loads just on the studs > I know better
Im making some fancy spacers.