four bar brackets

[Lizardracing]

Whats a center to center hole measurement on for bar brackets using 5/8 holes?

[dirtracerl77]

Every brand of car is different. Also most newer cars have a ton of holes.

[Lizardracing]

I'm not interested in making tons of holes. I think too many isn't a good thing. I'm just trying to find a measurement that allows some feel for the changes but not so fine that strenght becomes and issue. I'm thinking 5/8ths holes on 1" centers but I was hoping for confirmation and/or other ideas

[billetbirdcage]

I'm not interested in making tons of holes. I think too many isn't a good thing. I'm just trying to find a measurement that allows some feel for the changes but not so fine that strenght becomes and issue. I'm thinking 5/8ths holes on 1" centers but I was hoping for confirmation and/or other ideas

It varies a bunch some maybe as close as 3/4" centers but that only leaves an 1/8" of material between the holes so some depends on the thickness of the bracket and the design. Typically I try to limit the hole to 3 degree's max and usually do 2.5 degree adjustments, but that will depend on your length of bars. Doing a 15" bar with half inch holes your limited to 3 degrees or so as they get to close together and don't leave material between the holes.

Tell me your upper and lower bar lengths and I can tell you distance to get a certain degree change per hole.

[rrrrick]

to start with the hole center to center you want to know on the length of your bar and how much angle do you want to move the bar with each hole.

Then you decide what is your minimum bar angle and your max bar angle you think you want and that works out your hole pattern.

[Lizardracing]

My new bars are 15"/17" on a 110" WB car. My old ones were 15 1/8" top and bottom with some real crappy brackets so I cut them off and going with 15"/17" to see if I like that better on the small tracks I've been running on lately. I guess my question should have been how much change is a appreciable change for an okayish driver like me? Is that the 2.5 degree Billet mentioned?
My plan so far is the bottom bars range from 5' downhill to the frame to 30' uphill on the frame. The tops bar will be 0'-45' uphill to the frame. All figured with the car blocked and RH. Also using BSB 7320 cages and 0' indexing or level across the bottom.
Almost forgot. 3/16" steel is the plan set 2" apart for clearance. I have my templet made up already. I guess I could post a picture if it's helpful at all.

[billetbirdcage]

My new bars are 15"/17" on a 110" WB car. My old ones were 15 1/8" top and bottom with some real crappy brackets so I cut them off and going with 15"/17" to see if I like that better on the small tracks I've been running on lately. I guess my question should have been how much change is a appreciable change for an okayish driver like me? Is that the 2.5 degree Billet mentioned?
My plan so far is the bottom bars range from 5' downhill to the frame to 30' uphill on the frame. The tops bar will be 0'-45' uphill to the frame. All figured with the car blocked and RH. Also using BSB 7320 cages and 0' indexing or level across the bottom.
Almost forgot. 3/16" steel is the plan set 2" apart for clearance. I have my templet made up already. I guess I could post a picture if it's helpful at all.

Here is the center to center spacing between .625 holes to get a certain degree change:

15" long bar

degree change / material left between holes /center to center of holes
2.5 / .029 / .654 (obviously to close)
3.0 / .160 / .785
3.5 / .291 / .916

17" long bar
degree change / material left between holes /center to center of holes
2.5 / .116 / .741
3.0 / .265 / .980
3.5 / .413 / 1.038

[billetbirdcage]

You can do less material between the holes if you only using one set of holes (bar lengths), but if you have say 3 sets of holes for 3 lengths of bars then you have to be careful. If you have 14, 15, 16" holes for the lower and your in the 14" set of holes then you can fold the bracket (15 or 16" hole area) if the holes are too close together due to leverage. Unless you do something like a stiffener or bend at the top and bottom.

On a LM typically you holes will range from this: To avoid having unnecessary holes and weakening the bracket

LRU 17.5 to 27.5
LRL 5.0 to 15.0
RRU 12.5 to 22.5
RRL -5.0 to 7.5

That's just an average range, opinions will vary

IMO, you should use 1/2" holes and just make some spacers out of 3/4" steering shaft with the ends turned down to .625 so they stay in the 5/8" rod ends. This allows for the smallest adjustments and easiest way to make spacers if you want to do it yourself. Using spacers that don't go into the rod end are a pain to move the bar as they fall out and are harder to get 3 things aligned when moving a bar especially on the LR. Typically I shoot for 2.5 degree changes on uppers as it's easy to keep track of the angle your at (20.0 / 22.5 / 25.0 and etc) and 2.5 on the lower unless your have shorter bars then 15" then you may need to go to 3.0 degrees.

Again several ways to do thing neither is right or wrong just different.

[Lizardracing]

I'll be using one set of holes in the 15"/17" variety.
In the past I've used oilite bronze and turned it down to a .005 press fit into the Hiem joint. I did this in case the Heim binds up it's still rides on the bronze. It's also doesn't gall up the bolt. I welded the spacer to the inside of the brackets so no fumbling around with those either. I also used Pins instead of bolts because our tracks like randomly dragging out the water truck and grater so changing bars without tools in the staging lanes has advantages.

I like your idea though with the spacers. I plenty of 7020 aluminum so I'll use that and machine them on the lathe. I could make them from 1" stock and put a 45' bevel for the Heim and the part that goes into the heim will go half way through on both sides for maximum support. I could also use a shaping tool and trim away excess for looks and to save the 1/10 pound. :/ I might just leave it .020 shy of touching inside the adjoining spacer to make sure they stay tight. I'll just face it and see what works out.

Using angles are nice when comparing chassis to chassis and all that. I have one car and I've got my crew trained to go by hole numbers. I usually have three that go but only one of those goes with us every night. They know that the first race the set up sheet says hole #4 on the RR and the on the second race the bar goes in the #3 hole. It's just easy to read and keep track off. If I want something different I just give them a different sheet to go by.

Thanks Billet and everyone for the advice. Always concise and useful.