Bending a tubular sway bar?

[69427]

Just curious. I've got a lightweight C4 tubular sway bar (24mm?) sitting on the shelf. I noticed it's very close to the basic length of a C3 sway bar, but too wide at the link attachment points due to the different bend angle.



I've got a C4 suspension under the car, but it's narrowed, so a C4 bar won't work as is. As this is a tubular bar, is it possible to (cold) bend it inward a touch, (and probably bend the endlink area the opposite direction to maintain its perpendicular direction)?

Comments? Opinions?

 

[mrvette]

I got my stock C3 rear sway bar without stock links....but noticed the ends looked VERY familiar....so heated orange/yellow with propane torch and twisted 90* and used common parts house... sway bar fittings for 20 bux

if I can do that, I can't see why that bar shouldn't work with similar treatment techniques....but you need get it glowing good and proper, obviously....

 

[JeffP1167]

isn't the sway bar heat treated though and by taking a torch too it it will weaken it?

 

[mrvette]

isn't the sway bar heat treated though and by taking a torch too it it will weaken it?

I remember reading from a good source, on a vette group, that no, it does not affect the treating....I dunno why....

at least not anything we likely to notice....

 

[69427]

I changed directions. Instead of bending the bar to match the C3 width, I'm in the process of making some custom links to attach the wider C4 bar to the lower A-arms. It's a little more work, but I'm just curious about this bar.
I'm currently running a 1.125 C3 bar on the front, and the thing understeers like a pig. The amusing part is that, with the C4 suspension under the car, I'm running basically the same wheel (spring) rates f&r and front bar size as I had with the C3 suspension, but the balance is completely different. Perhaps the C4 rear is just biting more than the old C3 geometry would allow.
So, I need to reduce the front roll stiffness. I'm using this bar as it's left over from when I bought the C4 suspension at a swap meet years ago.
This bar is 24mm in diameter, and apparently '96 was the only year it was offered. It's a little small for my taste, but it's darn lightweight (5.5 pounds versus the 11.5 pound 1 1/8 inch bar) and at first glance it will reduce the front roll stiffness too much. One thing in its favor is that the torsion part is similar length to a C3 bar, but the arms are 13% wider (43' versus 38"), attaching further out on the lower A-arm. This should, if I'm correct, mean that the bar will twist more for the same amount of wheel travel, mimicing a stiffer bar.
Depending on the amount of front roll stiffness I lose, I have two other avenues I'm exploring to recover some of it back. Pre-'96 model C4s offered a 26mm bar, so I could try to find one of them down the road (I haven't done the math yet to see what the rate difference would be), or I could step up the front (coilover) spring rate, which I've been mulling around for quite a while. I've got 375# springs on them, and if my calculations are correct, these give me roughly the same wheel rate at the 550# springs in my original C3 suspension.

 

[JeffP1167]

A stock IROC-Z 3rd gen f-body hollow front sway bar more closely resembles your stock bar. I think the are larger then the vettes though.

 

[69427]

A stock IROC-Z 3rd gen f-body hollow front sway bar more closely resembles your stock bar. I think the are larger then the vettes though.

Thanks! I'm not a Camaro expert. Which years were 3rd generation?

 

[JeffP1167]

A stock IROC-Z 3rd gen f-body hollow front sway bar more closely resembles your stock bar. I think the are larger then the vettes though.

Thanks! I'm not a Camaro expert. Which years were 3rd generation?

I think the fbodies started with that hollow bar about 87-88 and used it till like 92

firebird ws-6 of that era also good.

 

[69427]

A stock IROC-Z 3rd gen f-body hollow front sway bar more closely resembles your stock bar. I think the are larger then the vettes though.

Thanks! I'm not a Camaro expert. Which years were 3rd generation?

I think the fbodies started with that hollow bar about 87-88 and used it till like 92

firebird ws-6 of that era also good.

Anybody have a Camaro/Firebird of this vintage to give me an idea of the shape/length of the front bar?

Thanks.

 

[Twin_Turbo]

I've got a couple The Camaro bars are anywhere from 32 to 36mm thick. This is a 36 mm one, don't have measurements though (could measure next weekend or so)

 

[JeffP1167]

I've got a couple The Camaro bars are anywhere from 32 to 36mm thick. This is a 36 mm one, don't have measurements though (could measure next weekend or so)

thats the same setup joops trans am has on it. the hollow sway bar, wonderbar & power steering cooler.

 

[Twin_Turbo]

Does it have a 36mm front bar too?

 

[JeffP1167]

I'm not sure of the size it came off about a 89 IROC-Z it makes the original bar look like a paperclip though. Also about 1/2 the weight of the original one.

 

[Twin_Turbo]

IROCs usually have either the 34 or 36 mm bar depending on the susp option (WS1, 2 or 6)

 

[69427]

Thanks, guys. I appreciate the help. I might hit up a junkyard this week to look around for a Camaro bar, or anything else that might fit. The arms on the Camaro bar look too long, but that part can be modified pretty easily. I've got several measurements of clearances, tolerances, and attachment points on the present frame/suspension, so we'll see what I can find.

 

[69427]

'93 Firebird bar has possibilities.

Spent some time at the junkyard yesterday looking for a hollow bar that might fit the '69. Happened upon a '93 Firebird with a bar that looked like it might work. (Firebird bar (1.185") on top, Corvette bar (1.125") on bottom.)



I cut the excess arm length off, as I'll be keeping the same arm length as the production C3 bar. The bar wall thickness was about .185".



I've got the shortened bar installed for a trial fit. I'm going to try to put the bar links at the point where the shock attaches to the A-arm, rather than where the original C4 link attached. I have a heim joint and long bolt positioned where the final link will reside. This outer position should effectively make the bar a bit stiffer in relation to wheel travel compared to the original position. I'm hoping to come up with a three hole bar attachment configuration that will allow me to move the links to a softer or firmer position.



I've done a few torsion calculations, and it looks like this bar should be very similar in performance as the 1.125" C3 bar, but several pounds lighter.

 

[69427]

Well, I finished welding the ends back on the shortened (F-car) bar arms the other week, and got the bar and links installed back on the car. Only had the chance to put about ten miles on it, but the roll stiffness still feels very good. I'm looking forward to some track time to see what the balance feels like at higher speeds and on some stickier tires.

While driving a pickup load of stuff to the house today and trying to focus on more interesting things (car stuff), it suddenly occurred to me that I've probably raised the c/g height of the '69 with all the changes I've made the past year. I've taken about 180 pounds off the car, but most all the weight reduction points (C4 suspension, tubular sway bar, aluminum lower radiator crossmember, etc) have been below the stock c/g height. I'm still digesting the secondary issues (new c/g height vs rollcenter height) that pop up from this change.

 

[mrvette]

Well, I finished welding the ends back on the shortened (F-car) bar arms the other week, and got the bar and links installed back on the car. Only had the chance to put about ten miles on it, but the roll stiffness still feels very good. I'm looking forward to some track time to see what the balance feels like at higher speeds and on some stickier tires.

While driving a pickup load of stuff to the house today and trying to focus on more interesting things (car stuff), it suddenly occurred to me that I've probably raised the c/g height of the '69 with all the changes I've made the past year. I've taken about 180 pounds off the car, but most all the weight reduction points (C4 suspension, tubular sway bar, aluminum lower radiator crossmember, etc) have been below the stock c/g height. I'm still digesting the secondary issues (new c/g height vs rollcenter height) that pop up from this change.

INteresting, but for all that weight difference, wouldn't dropping the ride height about 1/2 inch or so, make up for that??

 

[69427]

INteresting, but for all that weight difference, wouldn't dropping the ride height about 1/2 inch or so, make up for that??

It's already as low as I can get it without ripping off the exhaust when I hit a bump.

 

[TimAT]

As thick as that bar looks where you cut it, it almost seems like you could tap it and use heim joint ends.

 

[69427]

As thick as that bar looks where you cut it, it almost seems like you could tap it and use heim joint ends.

I agree. I'll admit I never thought about using a heim in that direction (horizontal, if I understand you correctly). I haven't looked up the load specs of a heim that size, but it would be operating in a shear type loading. To be honest, I spent more time than I liked just dealing with the linkage issue. I don't like short links due to the angularity issue when the suspension moves up or down, and most every dual vertical heim setup I tried ended up leaving the connecting link being very short, causing a lot of side force (shear) on the heim, rather than just compression/tension forces. I looked at the McMaster-Carr website while I was working on this, trying to find a compact heim type assembly, but didn't see anything that looked like it would work or be strong enough. So, currently I'm using a heim on the A-arm bracket and nylon bushings on the bar eyes, which gave an acceptable link length.
The present setup seems to work okay, but I might just look again at the M-C website and see what the shear specs are for a heim with about a 7/8" end threading.
Thanks for the idea, Tim!

 

[69427]

Ran a track day at Putnam Park on Friday with a Porsche group out of Ohio. (I think I may have had the least expensive car there. :amused Anyway, the track has some decent higher speed corners, and with the Nitto tires on the '69 it just felt like I was getting a little roll in the corners. I currently have the F-car 30mm hollow bar on the car (with shortened arms) and I think I might try going up one size if I can find one in a junkyard this fall. The '69 was pretty neutral in handling, so I'm not thrilled about possibly causing a big understeer condition as a result of increasing the front bar size, but if so I've got a couple options to balance it out I suppose. I have the original rear bar from the '69 that I can transplant (or find a suitable shape rear bar off something at the junkyard), or finally install the '84 Z-51 rear spring I've got hanging on the wall in the shop. I currently have the base '84 rear spring on the car, and the Z-51 spring is about (IIRC) 20% stiffer.

 

[TimAT]

You know there are several places you can get good grade Heim joints around locally?

 

[69427]

You know there are several places you can get good grade Heim joints around locally?

I'm drawing a blank at the moment. Where's a few places to take a look at their selection?

 

[69427]

Got bored the other day and decided to install the '84 Z51 rear spring on the '69. As usual, I had to narrow the spring about two inches on each side to make it fit the narrowed '84 rear suspension on the car. As the Z51 spring is about 20% stiffer than the base '84 spring I had on it I decided to bump up the front (coilover) springs by 20% also (375# to 450#) to both keep from significantly upsetting the f/r balance, and to reduce the nose dive during hard braking. The next outing is just an autocross, but I'm hoping to get some feel for how the car responds with the spring change, and then I'll go from there making the necessary tweaks to get the balance where I want it.

 

[TimAT]

A couple of places come up first- Midwest Motorsports about 68th and State KCK, and Avparts- I-35 and Lamar, turn left- building right across the street from the stoplight at Merriam Drive.
You'll like Avparts- all sorts of surplus aircraft tooling- drills, milling bits, reamers, structural and sheet aluminum, AN hardware, and that's the short list.

 

[mrvette]

A couple of places come up first- Midwest Motorsports about 68th and State KCK, and Avparts- I-35 and Lamar, turn left- building right across the street from the stoplight at Merriam Drive.
You'll like Avparts- all sorts of surplus aircraft tooling- drills, milling bits, reamers, structural and sheet aluminum, AN hardware, and that's the short list.

I"m jealous, but there is a joint I ran across here in Jax...of a similar description, enough boltz to drive me nutz.....but it's back when building that BDSM gear....been a while....

:harhar:

 

[69427]

A couple of places come up first- Midwest Motorsports about 68th and State KCK, and Avparts- I-35 and Lamar, turn left- building right across the street from the stoplight at Merriam Drive.
You'll like Avparts- all sorts of surplus aircraft tooling- drills, milling bits, reamers, structural and sheet aluminum, AN hardware, and that's the short list.

I'm trying to remember if Midwest Motorsports is the place I went to that you recommended a while back. Pretty decent speed shop I recall.

Avparts sounds like an interesting place. I'll have to check it out.

Thanks.

 

[69427]

Got bored the other day and decided to install the '84 Z51 rear spring on the '69. As usual, I had to narrow the spring about two inches on each side to make it fit the narrowed '84 rear suspension on the car. As the Z51 spring is about 20% stiffer than the base '84 spring I had on it I decided to bump up the front (coilover) springs by 20% also (375# to 450#) to both keep from significantly upsetting the f/r balance, and to reduce the nose dive during hard braking. The next outing is just an autocross, but I'm hoping to get some feel for how the car responds with the spring change, and then I'll go from there making the necessary tweaks to get the balance where I want it.

Was back in Indiana last week visiting old friends, and ran an autocross while I was there. I had some concern about the roll stiffness balance after just making spring changes, but the car was reasonably predictable with the change (once I got the course memorized). Also, the front end dive was reduced enough where I didn't hear the spoiler scraping the pavement under hard braking. The car exhibited some oversteer on left hand turns (somewhat expected due to the rear spring change) but a bit of understeer on right hand turns (unexpected). I suspect that I have the corner weights off (misadjusted) on this first outing. Until I can find a great deal on wheel scales somewhere I'll just keep adjusting the springs at the next track day until the car feels a bit more similar in both left and right hand turns.