wheel spacer advice (2 Viewers)

[GLTHFJ60]

I don't think that the slip on spacers are much of a problem, it's the spacers that have studs in them. I don't run any myself, but I would think that as long as you checked the torque on the nuts, you're fine.

Then again, who knows. Adding another failure point in a critical system of a vehicle is never a good thing.

 

[ntsqd]

ya when you put it like that it is scary, though in most (keyword "most") driving situations i think it is more of a shear force, as the wheel is pushing directly upwards.

Having said that, sliding sideways on pavement is something that can happen i.e., winter driving and sliding off ice to dry pavement etc. and would probally be a good example of when youll find out exactly how well a spacer will hold up to "cantilevered loading". Which is probally the exact moment when whoever is driving on a set of spacers will wonder, did I pay the extra few bucks for the high end alloy spacers, and how much are they worth to me right now?

It starts out as a Shear force in supporting the weight, but with bending, tension, and compression forces added when cornering. With the offset stud spacers installed they turn it into a bigger complex of forces. The original stresses are still there, but now both at the original studs and then again at the new studs. Since the spacer moves the wheel mounting surface outward it introduces some more bending into the situation. That bending translates into tension and compression plus bending within the spacer. The required shape of the spacer can not help but have some nasty stress risers built into it.

If the wheel back-space combined with the spacer's thickness puts the center of the tire in the stock position then those loads are probably reasonable, though still present.

If the back-space combined with the spacer moves the tire center outwards then the loads and stresses can get ugly pretty fast.

I wouldn't and don't run this type of spacer. I do have a problem with others running them, but not from the "Oh my gawd, yer gonna kill everybody and their grandmother in Minnesota!" Chicken Little point of view. More from the standpoint that the decision was made with information about the downsides lacking. In science all it takes is one exception to ruin a perfectly good theory. I see this the same way. Most of those running them say they're fine (self delusion?), but who wants to be the one who proves that they are not? I'd like to see those making them post the results from an Engineering Analysis, preferably an FEA picture, from an independent & expert source.

With the thin type of spacer that fits between the wheel and the mounting flange the only real problem comes from running alloy wheels that are thick where the wheel stud holes are. Those can reduce the amount of thread engagement to less than the minimum acceptable.
FWIW search out these that are made from steel or are not cast aluminum. Like cast aluminum pinion wedges they will break. Steel or aluminum sheet and plate stock are what is best. They also tend to be both flatter and have their side be more parallel than the castings.
There is a guy local to me who can cut out such spacers on his small CNC plasma table. He has a $60 minimum and I'll bet that you could have several different thickness' made for that $60 Look around, I'll bet that such a service is available in most of the U.S. They may be water-jet cut too.

 

[cody c]

It starts out as a Shear force in supporting the weight, but with bending, tension, and compression forces added when cornering. With the offset stud spacers installed they turn it into a bigger complex of forces. The original stresses are still there, but now both at the original studs and then again at the new studs. Since the spacer moves the wheel mounting surface outward it introduces some more bending into the situation. That bending translates into tension and compression plus bending within the spacer. The required shape of the spacer can not help but have some nasty stress risers built into it.

If the wheel back-space combined with the spacer's thickness puts the center of the tire in the stock position then those loads are probably reasonable, though still present.

If the back-space combined with the spacer moves the tire center outwards then the loads and stresses can get ugly pretty fast.

I wouldn't and don't run this type of spacer. I do have a problem with others running them, but not from the "Oh my gawd, yer gonna kill everybody and their grandmother in Minnesota!" Chicken Little point of view. More from the standpoint that the decision was made with information about the downsides lacking. In science all it takes is one exception to ruin a perfectly good theory. I see this the same way. Most of those running them say they're fine (self delusion?), but who wants to be the one who proves that they are not? I'd like to see those making them post the results from an Engineering Analysis, preferably an FEA picture, from an independent & expert source.

With the thin type of spacer that fits between the wheel and the mounting flange the only real problem comes from running alloy wheels that are thick where the wheel stud holes are. Those can reduce the amount of thread engagement to less than the minimum acceptable.
FWIW search out these that are made from steel or are not cast aluminum. Like cast aluminum pinion wedges they will break. Steel or aluminum sheet and plate stock are what is best. They also tend to be both flatter and have their side be more parallel than the castings.
There is a guy local to me who can cut out such spacers on his small CNC plasma table. He has a $60 minimum and I'll bet that you could have several different thickness' made for that $60 Look around, I'll bet that such a service is available in most of the U.S. They may be water-jet cut too.

i think your logic is about the same as mine, i would like to note that you have to take in consideration the efeects of a wider tire, and where the forces are being applied because of that.

Also in the circumstance of my 80, i bought 37" tires on 17" fjcruiser wheels from someone on mud, who had them mounted on the same vehicle. Unfortunately the PO forgot to mention that the BS was too little and there is huge problems because of this unless you use spacers. I didnt want to run spacers if I could avoid it but i find myself in the same situation. Althugh I will probally experience more leverage on them with 37's, and a cummins+winch+bumper. I dont like driving highway if I can avoid it, which for the most part I can, as I know of a few stories about people losing tires and I know there is more potential there, so I am more cautious of speeds and enviroment and any feedback/vibrations through the vehicle.

 

[ntsqd]

Wider tires usually make things worse because they can't go in, the inside tire sidewall is pretty much in a fixed location if you're going to be able to steer etc.

But, you understand the issues in using the spacers and have made an informed decision. That is the most that I could hope for.

 

[cody c]

Wider tires usually make things worse because they can't go in, the inside tire sidewall is pretty much in a fixed location if you're going to be able to steer etc.

But, you understand the issues in using the spacers and have made an informed decision. That is the most that I could hope for.

exactly, as they are wider with more backspace they will still cover ground on the inside of the tire where the original tire had contact, but at the outside they will be further away from the original location applying more leverage.

 

[GLTHFJ60]

Now my question is how do large 1 or 2 ton trucks get away with having the wheel mounting surface so far away from the middle of the hub? Is it because they run such a large positive backspace, there negating the effect?
As shown by the front axle on this ford.

 

[Elbert]

I have spacers....just took the easy way out... maybe one day I'll get in there and grind the calipers a little bit. I did see a pic somewhere here it showed where a wheel spacer completely sheared off.. I run the 1.5 inch type (one ones I could find at the time...with the built in studs). I've checked the torque a few times and so far no problem, I find them a necessary "evil" for now as I could never find any 15*8 black steel wheels that clear the front... But I do think with a little grinding on teh calipers I could possible clear....very close though.

For now I guess it's wait and see. I'm not running huge tires ...33*12.5*15 is about as large as I'm going... I do have some285 70 17 tires on 17 inch FJ cruiser wheels I've not tired out yet but I suspect they too will need spacers on the front.

 

[Mace]

Now my question is how do large 1 or 2 ton trucks get away with having the wheel mounting surface so far away from the middle of the hub? Is it because they run such a large positive backspace, there negating the effect?
As shown by the front axle on this ford.

That individual truck is designed that way.

However, a lot of the older ford dullys used a spacer to get the dually width.
They were steel and not aluminum though. Some were even REALLY wide and shaped like an hourglass.

As long as the studs stay tight, I do not have an issue with the AL spacers. IMHO, to see any failure, the studs would have to loosen first..

 

[ntsqd]

Loose nuts or studs is just one of the reasonably possible failure modes.

With those spacers used on the 2 ton the WMS could be in the next lane over and not make much difference so long as the center of the tire is in the right place. The big, very big difference is the geometry of the spacer. Those used on the medium duty trucks are a totally different shape than these aluminum jobs used around here. That difference in shape is the critical difference. Doesn't hurt, either, that those spacers are made from a metal that doesn't have a fatigue life when inside it's elastic yield strength.

With aluminum there is a finite fatigue life even when the stresses are below the elastic limit of the metal. With mild steel there isn't any fatigue life limit until the elastic range is exceeded. Basically if you bend it and it snaps back then with mild steel the fatigue life is infinite, but doing the same to aluminum does fatigue it.

 

[Mace]

What difference in geometry?

One of the sets I had was a Dognut shaped piece of steel, just like the AL ones.

And I agree with you on the fatigue life of AL, but it can't be ANY worse than the design of some of the rims out there...

 

[ntsqd]

What difference in geometry?

One of the sets I had was a Dognut shaped piece of steel, just like the AL ones.

And I agree with you on the fatigue life of AL, but it can't be ANY worse than the design of some of the rims out there...

The 1 ton+ spacer generically looks like the first, the common off road spacer looks like the second. Notice how the necessary pockets for the studs and lug nuts in the off road spacer results in a zig-zag load path, and that the load has to go around sharp corners. That is NFG, but within the space available there really isn't a better way to do it. If the spacer is aluminum and it cyclically bends even the slightest you're into a fatigue life question. Shrinking the 1ton's design isn't going to fit until the spacer's length gets quite large. I'd say on the plus side of 2 inches.

No argument that some wheels out there are pretty iffy, but all of them have reasonable bulk at the bolt pattern. The closer to the center of the wheel the more leverage that the load has and the greater the stresses involved. So even with an iffy wheel it isn't out of the reasonable range of possibilities that the off road spacer would still be the weak link.

 

[Mace]

I had a stock dually spacer that was exactly like the second pic (made out of steel with 5/8" lug nuts). They were not as common, but they did exist. I'll try to find a pic.

 

[ntsqd]

Steel would be good. A big part of the problem is the choice of aluminum. Those front spacers on the tow truck most likely are cast steel.