Thread: Nextel/NASCAR sway bar selection

Tweet

I set my 36 up for sway bars with splined ends and hid them in the spreader bar. I am absolutely baffled on material selection. I still havent found anyone with scales that I can borrow so I don't know the exact weight at each wheel. Should I wait until all is complete and weigh it, then order the correct material? Or can I just set it up with the lightest bar I have, 36.5"x1"x.095 wall with 14" arms and try it? How do these guys know the amount of weight needed at 5 degrees of turn at one wheel? Any guidance would be appreciated. I know I'm guessing at this time, but I was hoping to get myself in a ball park range so I don't have to make major changes on arm lengths and a-arm mounting points.

David

I assume it's a relation to weight of vehicle, amount of travel, and spring rate on suspension. This is giving me a headache folks. LOLs.

The bar you have in there should be good for a starting point. Much easier to do on the scales, but not essential. I'd suggest using the bar you have as a starting point, when the car is done and you drive it a bit you'll be able to tell if you want more or less.

Then there's the old eyeball method--with the car setting on all fours and at or near done weight, slide a jack under one of the corners with the end links of the bar unhooked. Measure how much the one corner will lift before the frame begins to lift. Let the jack down, connect the end links on the bar, lift the same corner with the jack in the same place and again measure how much the wheel lifts before the frame starts to rise. Compare the measurements. If you have other bars, switch to either a lighter or heavier bar and repeat the process. Comparing measurements from bar to bar will help you figure a baseline as to where you want to start. But yeah, it's a whole lot easier using a set of wheel scales on a done car...... Don't know if I explained the "eyeball" method very clear, but hopefully you get the idea. Might not hit the perfect bar, but at least when it's a done and driving car you'll have a reference for how much change different bars give the car.....

Yes Dave. That helps. The second part, what am I looking to achieve with the measured distance link unhooked and attached?
I have never studied how a suspension reacts with anti sway bars. It helps eliminate body roll by applying pressure to the opposing wheel? If the exact same pressure was applied the bar hasn't twisted under load which isn't what is wanted.....correct? Or, ?
Am I even on he right track? If I get the bar too thick with no give, will I damage the a-arms? Thanks Dave!

David

The measurement with the end links unhooked can be called the 'baseline'. Measurements taken at the same point with different sized bars and the links attached is just a reference measurement. When the car is done and driving, when you consider changing to a stiffer or softer bar you'll have a 'how much will it change?' reference....

Yup, the sway bar will transfer some of the weight to the opposite wheel....actually, you wouldn't believe how much weight is transferred by changing bar size!!!! Done a lot of messing around with various cars on the scales....oh yeah, if you're doing a left hand turn, as the left front suspension compresses, the weight not only transfers through the bar to the right front front, but to the left right rear, as well....

Too thick a bar takes all the movement out of the suspension and can break parts.... It also leads to a terrible push in the front end.

Someone please school me why use a race part requiring all that vs using a commonly available aftermarket bar??

Its not really necessary if you have some designed around your vehicle already and all it see's is street use. For me, since this vehicle didnt have any such option and it's odd track width, CG, and weight distribution, I imagined at the time that finding a OEM bar that would suit my needs would be a real headache. Plus, hiding it in the spreader bar (front) and support bar (rear) really cleans it up like what I did in the fifth picture on my garage link.

As far as cars like a (eg) 66 Chevelle, I imagine something could be gained by going with the after market options if you were serious into the Pro Tour cars and planned on actually spending time at a track. I doubt very many of these cars actually log any track time. Just for fancy conversation from what I've gathered at area car shows when I talk to these fellas. I'm a member at ProTouring and LateralG and a lot of those guys actually toss their cars through the turns on a regular basis. Some of them are pulling some serious numbers in the turns. Neat to watch a 65 El Camino running the same times as a Vette.

David

Originally Posted by 1gary

Someone please school me why use a race part requiring all that vs using a commonly available aftermarket bar??

I've tried to gather information from the sites mentioned above and all I can say is that they talk over my head just a bit. Thank you Dave. You've helped me out a lot. I'm going to go with the lightest bar (.095) and extend my arm to the rear side of the a arms (drill holes down the length) so I can play around with the arm lenght (longer lever carries less load) a little. If that bar is too light I can step up a size and do the same.

Originally Posted by Stovebolter

I've tried to gather information from the sites mentioned above and all I can say is that they talk over my head just a bit. Thank you Dave. You've helped me out a lot. I'm going to go with the lightest bar (.095) and extend my arm to the rear side of the a arms (drill holes down the length) so I can play around with the arm lenght (longer lever carries less load) a little. If that bar is too light I can step up a size and do the same.

Along with that, David, our good friend Mr. L (leverage) is also going to help with the chassis tune up as to the placement of the anti-roll bar arm on the lower A-arm, inboard to outboard mounting points on the lower control arm will also change the amount of leverage, therefore the bar rate can be different, too!!!!

Imagine a scene at your favorite parts store, "I would like a .750" bar with .083" wall for the back of my '57 Chevy with a 9" Ford rear end, housing floaters, and the dual AFCO shock option, please." Heck, I ordered a set of hole saws for cutting oval holes at Car Quest 2 years ago and they are STILL on backorder!!!!!!

Another thing I like to do on the anti-roll bar is to have a fixed mount with internal splines for one end on a sturdy upright (mine is a leg on my chassis table), then an adapter onto the other splined end with a nut welded on it---You can use a 1/2" drive torque wrench to 'measure' the bars, ie X degrees of movement on the bar = X ft. lbs. of torque on the torque wrench.....

I'm shooting for 1g lateral on the 'maro and the '57... gets the boys at the Sunday afternoon autocross really scratching their heads!!!!!!!

Originally Posted by Dave Severson

Another thing I like to do on the anti-roll bar is to have a fixed mount with internal splines for one end on a sturdy upright (mine is a leg on my chassis table), then an adapter onto the other splined end with a nut welded on it---You can use a 1/2" drive torque wrench to 'measure' the bars, ie X degrees of movement on the bar = X ft. lbs. of torque on the torque wrench.....

That makes perfect sense to me. Thanks Dave.

David

What's the length and spline count on the bars you're running, David??? Got a couple really good swap meets coming up this Spring usually loaded with late model parts--also been seeing a lot of bars and arms showing up on Racing Junk lately at some very reasonable prices......

I believe they were 1" hollows (.095 wall)x 36.5" long, 48 spline but I'll have to check next week when I can get out to the shop. On call this week.

David

Dave, I finally got to the shop. The front bar I ordered a 38.5x0.250x1.125 27 spline. Way to much for my truck. I'm limited to a 5" arm which will double the rate compared to a normal arm, so I'm stepping down to a 1"x.095x39 to get the lightest bar as a starting point. I thing they even make stepped bar in 3/4" with 1" ends.

The rear bar is no big deal. It's wider at 42" and I'm able to use 12" arms so I started at the 1.25x.095x42" giving me 200 lbs at 5 degrees of twist. I can step back to 1"x.095x42" and get down to 97 lbs.

At least I feel I have a decent starting point and I think found a set of used Long Acre corner scales close to me for $500. Then I can get my spring rates correct.

David

Good place to start with the bars! Good price on the scales, once you have a set you'll wonder how you got along without them!!!!

Still seems pricey for something that I may never use again. Then again I can always resell them.