Post by ES_97Sport on Dec 2, 2015 19:15:58 GMT -5
Maybe i got lucky with a quality version coupled with proper care and no heavy weight stressers... plus bird is not a v-8... just a high tq 3.4 v6
BD is correct. There are not a 'few' choices in aluminum, there are dozens. And, yes, they all have their own characteristics. Typically the stronger it is, the more expensive it is, which means builders have incentive to use cheaper materials.
The issue that occurs with spacers is the same issue that you run into when changing backspacing (offset). The further out you go, the longer the lever, the more force applied to the hubs, bearings, studs, spindle, etc. Even to the control arms and ball joints.
redraif, you are not working on a car. What works on your 'Bird is not automatically transferable to a truck. ESPECIALLY NOT a vehicle that will be taken off road.
I have 15"x10"s on my '68 'Bird with 255s. Total wheel weight is about 30 lbs. A 15"x8" RIM on the big Sport weights 28 lbs - almost as much as the combined weight of the tire and rim on my 'Bird. Total wheel weight for the big Sport is about 90 lbs.; keeping in mind that I run a lighter than typical 6x3 ply tire. That is 3X the weight of my 'Bird tire/rim.
Ignore the illustration on the left.
The 'load' is your tire and rim which I'll just call the 'wheel'. In real life this is anything hanging off the spindle. The 'fulcrum' is the center point between the wheel bearings in the hub.
Simply, the way a lever works is this ... Moving the fulcrum to the left in the illustration lengthens the 'effort arm', decreasing the amount of 'effort' or force necessary to lift the 'load'. Moving the fulcrum to the right shortens the 'effort arm', increasing the amount of 'effort' or force necessary to lift the 'load'.
How this works with your suspension ... If you draw a vertical line through the two ball joints and a horizontal line through the center of the spindle, the end of the 'effort arm' (where the finger is) would be where the two lines intersect. Unlike in the illustration, this is a stationary point that does not change.
The 'effort arm' is very short and does not change. The length of the 'effort arm' is the distance between the 'fulcrum' and the stationary point described in the previous paragraph.
The 'load arm' length changes. This is the variable that changes when you change rim offset and/or install a wheel spacer between the rim and hub. Negative rim off set and/or the installation of a spacer increases the 'load arm' length.
Very (very) simplified ... In the illustration, the 'fulcrum' is in the middle (center) of the arm. To lift 1 lb of weight it takes 1 lb of downward force. Moving the 'fulcrum' to the left half way again (shortening the 'load arm'), means it takes .3 lb of downward force to lift 1 lb. Moving the 'fulcrum' the opposite direction by half (lengthening the 'load arm'), would mean it takes 3 lbs of downward force to lift 1 lb. Since the 'effort arm' is fixed, any changes in length are always made on the 'load arm'.
This is a great and wonderful example of how a lever works, except for one tiny little detail ...
"... the end of the 'effort arm' (where the finger is) would be where the two lines intersect. Unlike in the illustration, this is a stationary point that does not change."
Remember this? Yea, this is the part that sucks. Because the end of the 'effort arm' is fixed, any force that's applied to the end of the 'force arm' is transmitted into the 'lever' itself. If the lever isn't sufficiently strong, it will bend and/or break.
Think of this as the guy jumping on a diving board, and the diving board snaps. The more the guy jumping weighs, the stronger the diving board (and associated parts and pieces) has to be. That is also true if the length of the diving board is increased.
In this case, we're talking about doing both. The diving board is being lengthened - moving the wheel out, further from the OEM wheel flange - and we're increasing the weight of the guy - increasing the weight of the wheel.
Now, if you've ever seen a diving board break because it was 'overloaded', you'll probably notice that the break is at the 'fulcrum' - that little cross-bar under the board at the edge of the pool. That's because that's where the load is being focused. The 'fulcrum' in our application, as noted above, is the wheel bearings. This is the most obvious point of failure which is why its also the first one anyone brings up when talking about rim offset or wheel spacers.
The 'strength' of the lever in our case is made up of the wheel studs, rim, spacer & studs, hub, etc. Any and all of these have to be strong enough deal with the force applied and they're all subject to the force multiplication of changing offset and/or adding a wheel spacer.
What many overlook at this point is that there's more than one lever involved here ...
"If you draw a vertical line through the two ball joints and a horizontal line through the center of the spindle, the end of the 'effort arm' (where the finger is) would be where the two lines intersect."
That line through the ball joints is another lever. While it is a different type of lever, it is a lever none the less and it still multiplies force. In this case it is not a matter of lengthening the 'load arm' or 'effort arm', it a matter of lengthening the entire arm by changing rim offset and/or adding a spacer.
Ball joints are strongest and last the longest when the force applied is vertical - through the vertical center line of the joint - and it is compression force. The 'ball' of the joint is being forced against the 'cup' of the joint. The 'cup' is the part attached to the a-arm, and the 'ball' is the part attached to the knuckle or spindle. The joint is weakest when the reverse is the case. In the middle is when force is being applied horizontally to the joint - where the 'cup' is being forced in one direction while the 'ball is being forced in the opposite direction. This is what happens under normal operations, but changing offsets and/or a adding wheel spacer multiplies the force applied to the joints.
This is extremely simplified and I left some stuff out to not muddy things too much, but this is the general idea. What would be nice to illustrate is the actual math and forces involved. That's not really possible except at a very high level without a good bit of measuring and introducing a lot more variables.
What i can tell you from experience is that moving the wheel out by 1.5-2.5" using offset, a spacer or both and then running a 80+ lb tire/rim combination is going to put a lot of stress on a lot of parts. I can also say, and there are plenty of people who have tried this that would back me up, that spacers and heavy wheels don't play well together; even less so if the vehicle is used off road where its subject to a lot more abuse than would normally be seen on the street.
Edward