home made chassis stiffener vs rear anti sway bar

[manoa matt]

Does anybody have a chasis stiffener or tried to make one?

Here is one made for Alfas: http://www.centerlinealfa.com/cgi-local ... ?E+scstore

Shouldn't be too hard to make.

I'm looking to either make a chassis stiffener similar to the one pictured, or buy an aftermarket rear anti-sway bar.

I think I could make the chassis stiffener for under $50 on a Saturday afternoon, but I don't know if a $200 rear sway bar would be a better investment

I would like to hear peoples' suggestions on tightening up the frame flex.

Matt

[So Cal Mark]

put in a roll bar

[mdrburchette]

I'd be interested in hearing from anyone running a rear swaybar and how it affected the handling and if they're using the bigger front swaybar with it.

[So Cal Mark]

the two are really different subjects; chassis stiffener vs rear sway bar. Sort of like saying, shall I eat lunch or paint the house?

[mbouse]

i am getting ready to install a 5/8" rear anti-sway bar on the '78 after having done so to the '80 a year ago.

$200.00 is too high of a price to pay, though i see where you came up with that number (IAP). Look elsewhere if you insist on NEW, and i promise a substantial savings.

You should be able to obtain a quality used rear anti-sway bar & bushings for under $100, delivered, if you give yourself a couple of months at the forums in earnest searching. my set up cost me $75 last year.

the last one i obtained this year july, i traded a '74 Spider tranny for (the tranny needed rebuilding). the guy gave up the rear bar for a larger front anti-sway bar. he is now happily running a 1" front bar and no rear bar. Denise....check with engineerted at Mira.

Spirited driving (fling it around turns) is what I am all about in my '80. Doing so while not causing gutteral sounds from the navigator, or hearing the tires squeal was what I accomplished by adding the rear bar. i changed nothing in my driving style, but added the rear bar.

No, i did not change the front bar. I have heard that going to a larger front bar accomplishes the same, or better, performance enhancement as adding the 5/8" rear bar. Some even profess that adding the front bar eliminates the need for the rear bar.

[mdrburchette]

Mike, I'm runing the 1" bar in the front. I didn't know if anyone installed both and could tell me how the car performed.
Were you getting squalling front tires or rear tires before you installed your rear bar? I'm just trying to wrap my feeble brain around this...


Like Mark says we're talking about two separate things. The chassis stiffener will keep the body from twisting. The sway bars affect how the tires contact the pavement.

[racydave]

Sway bars deal with body roll, and stiffeners deal with chassis flexing. The same ( almost ) as a roll bar to stiffen the chassis corner to corner. You can actually lift a front wheel with to much swaybars.It would be neat to have all these options and a set of Konis to dial in the perfect set up! I need my car set up for the city streets, as Ive been drivin her daily. I need to travel bumpy roads and keep my teeth. Ive also heard of mounts breaking on front larger dia bars. Maybee Ive just spent to many years in big cars?

[mbouse]

I honestly do not remember, but logic says it should have been the front tires that were doing the most complaining. front heavy vehicles should lose traction up front first as they dive for the corner.

and, yeah. I have read about guys recently that have issues with their front mounts after going to a larger bar....

i know of no one that has both a larger front bar and a rear bar.

[Danno]

I'll have to check my book again to see if there are some good hints in there for lightweight, front-engine, rwd cars. (see here) but if you really want to know the ins and outs of understeer, oversteer, and suspension basics, check this book out. One thing is for sure, those who are interested in Solo Racing, autocross, etc, NEED this book as a place to start. It's VERY VERY good, IMO.

[Jim DeShon]

You change front or rear bars to solve opposite problems. If the car tends to push [front end goes off line first] add a stiffer front bar. If the rear comes around too quickly [oversteer] add more roll stiffness in the rear. Neither one should make the car ride much stiffer. It will just decrease body roll. I plan to add a stiffer front bar to mine if I ever get it back on the road. It was my opinion that these cars push a little too much for my liking. J.D.

[BluEyes]

Jim, you've got that backwards there. A larger front swaybar will increase understeer/pushing and adding a rear swaybar will increase oversteer/looseness. The only place this doesn't hold true is if your car has just sooo much body roll (and a solid rear axle) that the contact patch of the front tires is rolling off the pavement. In that case, a front swaybar can actually decrease understeer by keeping the tires on the road.

Personally, my vote is for a chassis stiffener. These cars lack structure in the area of the rear footwells that really could use reinforcement. Trying to tune a chassis when the front and rear suspension mountings don't stay in the same relative position can just lead to you chasing your tail. As you stiffen the suspension, it will just make the chassis flex more and the suspension geometry change more as you go through the turn. It is pretty common for a car to handle quite differently after stiffening, changing what you would want to do to improve the handling.

[ishtvan47]

manoa matt - I'd love to know what you came up with in terms of a chassis stiffener. I've seen the same one you mentioned for Alfas, but haven't come across one for Fiats. I definitely felt some body roll/flex this last weekend when I took my '80 out for a drive on the Snowball Rally.

Looking forward to any suggestions on dimensions, materials, mounts, etc.

[azruss]

havent messed with this stuff much other than reading suspension and chassis books and taking a lot of physics classes. The big advantage of a stiff chassis is it allows you to run softer springs to get better cornering. A softer spring along with less unsprung weight will keep the tires in contact with the ground better, especially on a rough surface. bigger anti-sway bars reduce the amount of independent suspension. with a spider and a solid rear axle, you have no rear independent suspension, but the tire remains nearly vertical in a corner. Also a very stiff chassis helps reduce suspension modulations from broadcasting to the other 3 tires. I high flex chassis is a handful to drive because of the ever-changing suspension inputs. Looking at the Alfa add-on, i dont see how it would help much. would need to be modified with support pieces to connect to the floor pan or door sills. seems to make more sense, if you are running a roll bar, to put some extensions on the front to gusset the rear end of the door sill tunnels. The sill tunnels seem pretty strong to me. their only limitation is they are pretty low to make it convenient to get in and out of the car. I always thought a stronger tranny tunnel carried to the back of the trunk bulkhead would give you alot of bang for the buck.

[djape1977]

if your spider's body is solid(not rotten) than you don't really need any chasis stiffner.
get yourself a set of KYB two way gas shocks and a set of soft compound tyres.
if you're a pilot that's just lost your licence and want to compensate for the thrill of flying by scaring yourself trough the corners, add a rear sway bar.

[happybeachgoerm]

I Plan on Adding a(Building My Own) Roll bar and tieing ittowards the front somehow. are there any guys who know where i should tie it into?