There are a few different thoughts on this subject but for the most part they all agree on a few basic things. The panhard bars job is to locate the axle from side to side. When the axle moves up or down from normal ride height, the panhard bar will swing with the axle. Since it's located at one point on the frame, which we'll consider stationary, the other end will move in an arc with the center of rotation being the rod end on the frame. When the panhard bar is horizontal at ride height and you move it up 3 inches and down 3 inches you can see that the side to side deviation is minimal. Now try that with the panhard bar starting out while on a 45 degree downward angle. (It's an exaggeration, but you'll get the point). You'll see that the side to side movement is much greater, resulting in tire rub. You could move the ladder bars to the top position to lower the car, but it's generally meant to alter your instant center. Seldom with a ladder bar setup do you change it once you establish the right instant center for your car. With a 4 link setup it's critical to dial it in with changing track conditions, etc. The ladder bar is easier to set up, but you lack the ability to really fine tune it for racing like you can with a 4 bar. The basic rule of thumb for a ladder bar setup is to start with the lower bar parallel to the ground. The pinion angle is another topic that people have different opinions on. Typically you'll have about 2-3 degrees of angle on the rear end, meaning it's pinion is pointed up slightly. But.... that all depends on the angle of your engine/transmission. You pretty much want the engine/transmission and rear pinion parallel to each other, meaning that if your engine is pointed 2 degrees down in the rear, your rear pinion should be 2 degrees up. You'll have a slight adjust-ability with the ladder bars for pinion angle, but not a whole bunch. You want to try to figure most of it out now before it's too late. Just keep in mind that some people will say the the pinion angle is relative to the ground when in fact it's only relative the the engine/trans and rear pinion. When I built my last drag car, (the GSX) I drew all of it out on CAD before I started building. That really helps take the guess work out of it. That car always launches super straight! As far as the wheels and backspacing goes, I always have my wheels and tires of choice on hand before I start cutting. That way I can get them fairly close to the fenders, (the way I prefer them) without going to custom backspacing. Now that you have the shortened axle already, you'll need to work backwards and figure out what wheel width and backspacing will work best in your application. That becomes a little more difficult and has more room for error. Just remember to be a little bias when it comes to fender clearance. For the street you can always space the wheels out a little with axle/wheel spacers, but you can never go the other way if they're too close to the fender..... short of re-cutting the axle tubes. Hope this helps a little!! Steve
If that is per spring thats way too much. Half that would way better, depends how much fuel you will have in the back. Rick
I just can't understand why you spend all that money and don't go 4 link with 12 bolt. I have never seen a Buick explode a 12 bolt. And to have the adjustability of the 4 link. I will be using a 10 bolt in the Regal and will try to break it. Then I will go with 12 bolt.
It looks like those bars come up pretty high. I don't know I have never done it but want to on my 72 but still run 10.5 tire until it won't hold anymore. Then go to big tire. I would love to run with those 10.5 class with a Buick!
Well made a big push and trial fit the frame. All body mounts lined up and everything went smooth. As of right now im pretty happy but do have some concerns. Steve, does my axle look a little towards the rear? I don't have the lower ladder bars connected but I don't see that changing it much. I think it came out a little further towards the back then I thought. What do you think? If you look in the last pic where the frame comes up, it is only centimeters from touching the body. So I couldn't of really set it any further back without cutting that part of the floor out, and S&W doesn't show that cut. Actually you know what the top ladder bar hem joint at the front I have both turned out so 4-5 threads are showing, so if I brought them all the way in then technically that would bring the axle closer foreward right?
Steve would know more but I would have measured the wheel base from side to side before and after. That's what I did besides scaleling the chassis when all was done. Not 100% sure but thought it is 112" or more like 112.5". Looking awesome...good thread!
Haha yeah im learning as I go. I already have a few things I would have done different but hey that's how you learn. How is that 112" measured on a stock car? Is it from the center of the spindle to the center of the axle tube? If it is then I could measure now and see what I come up with. Its possible its fine and maybe ive just been staring too much. Its hard to tell because the frame has been off the body for months so its been a long time since ive seen it stock. When it was stock I was also used to seeing a 10 bolt with drums under there and not a narrowed naked 9" housing like now.
It appears that your wheel base is long, but start by measuring it. It is like you described... from center to center. Should be 112" but like I said earlier, you'll have more tire room if you move it out to maybe 113" or so. Running a large diameter tire will hit the front edge of the wheel opening first. Steve
Ok I measured both sides and I have 113" driver side and a tad over 113" passenger...so my eyes didn't deceive me haha.
Good deal. By memory I think I went 112.5 for tire clearance. But I also pied and cut the front part of the rear quarter up to the length of the rocker molding to make a bigger tire fit...it really isn't noticeable. I kind of "cheated" the molding more to the front. Where not talking a lot, just a half inch or inch.
This will probably be the only time that I miscalculated and had it turn out positive! What size tire/wheel/backspacing are you running? Do you have any pics of your inside trunk tub work you would be willing to share?
Well I enlarged and cleaned up the two holes I had to cut out of the floor for the back half cross member. I had a driver side repo rear floor pan I cut down to size and screwed around with. By the time I beat it down so it can fit over the cross member hump it looks like crap. I want it to look nice from underneath...even though the car will be so low to the ground you probably wont see it anyways. Im thinking instead of fighting with repo floor pans I might just buy some thinner sheet metal that is more bendable and just massage it squarely over the hole. Should look a lot cleaner from underneath. Inside will be obvious but with carpet you wont see anything.
Steve, now that the body is back on and I can see where everything sits should I do anymore bracing on the frame? I didn't want to get carried away because I didn't quite know how deep the floor sits back down on it. My rear bracing is centimeters from touching the floor so that worked out great, any higher would have been a oh sh*t moment. That pic is what I had done. Its boxed up to that body mount because I didn't want to lose that cross member. Just thinking if anymore is needed while keeping that crossmember.
Sorry, I don't recall if you plan on a cage or not? Either way it looks pretty good from what I can see. Without a cage you'll sacrifice a little chassis rigidity, but it would still be OK for normal/hotrod street use. If you plan on racing it or hooking up with sticky tires I would consider adding a roll bar with side and rear bars to keep it rigid. Slicks or sticky tires and some serious HP can tear things apart in a hurry. There's always a weak link... the key is to never find it! Looks nice!! Steve
