[steve]

It's time to start thinking rear suspension. I was surprised to read in another thread that traction bars are uncool. Besides the traction bars the only rear upgrade my car has is newer shocks...

What's the current formula for a nice relatively inexpensive upgrade to a better hooking rear ? Lose the traction bars ? Drag shocks ? Is it more about the geometry with the rear or the parts ? New leafs ? Is there a better than oem rear leaf ?

I know if I am serious there is unlimited possibility. I am just looking for the easy bolt on upgrades for now.

[screamingchief]

It's not about any of that,it's about the knowledge level of the guy that's working on the rear suspension.

In the right hands,a decent "old school" traction bar is more than enough to get the job done.

In the wrong hands,even the best Cal-Trac rear suspension set-up will be virtually worthless.

I've seen old school traction bar equipped cars that'll run deep in the 8's and hit the 60' clocks in the high 1.20's range (with the back wheels),so who cares if they're "cool" or not,they absolutely can work if a fella knows what he's doing,so dont dismiss them too quickly.

Just remember,there is a "science" to everything car related,and that includes this deal as well.

Problem is,there is a lot of "monkey see/monkey do" out there to deal with.

And most "newer" enthusiasts just dont understand the background and basic fundamentals of those "old school" traction devices.

Are there some things that are universal in all this,yeah sure.

Solid subframe bushings & good subframe connectors are pretty much SOP.

And you'll almost certainly need to deal with & adjust the rear pinion angle.

And you absolutely wanna be very observant & concerned with the shock travel.

And dont overlook the rear spring bushings either.

But yeah,many choices will affect other choices,so it's kinda hard to get too specific w/o knowing what you have in mind.

But what really matters is understanding the fundamentals.

Grasp those,and you can get it to hook without "traction bars" of any sort.

Fail to understand the fundamentals,and even the best rear suspension probably wont bail you out.

Lots of info out there on the web concerning this topic.

FWIW

Bret P.

[ta man]

Good tires.

[steve]

ok. i guess i have some studying to do. ill put the wallet away for now and do some reading !

[PONTIAC DUDE]

Nothing wrong with slapper bars. Ran them into the 10's and Southside bars into the mid 9's.

It's all about what type of surface you are running and torque/converter.

[Silver Judge]

Still related but off topic, what is the difference between the rear suspension on a pontiac Fbody with a factory v8 vs. a pontiac Fbody with the 6-cylinder ?

[screamingchief]

Originally Posted by Silver Judge

Still related but off topic, what is the difference between the rear suspension on a pontiac Fbody with a factory v8 vs. a pontiac Fbody with the 6-cylinder ?

You must be talking about the first gens...

In '67 it's known that the base model 6 cyl. cars only had the RH/passenger side bars.
(less spring wrap-up)

And IIRC the sprint 6 & V-8 cars got the bars on both sides.
(more pronounced spring wrap-up due to the added hp required the added bar)

The '67 F-bodies only needed the traction bars because the mono-leafs had spring wrap-up and wheel-hop related issues.

And for '68 ^ the traction bars were dropped entirely when they went to multi leaf rear springs and staggered shocks as SOP.

I dunno,just dont quote me on any of that,as I'm not a rabid first gen guy myself,even though I have a '67 shell that I'm gonna build a race car outta someday,but that one does'nt have any bars under it right now,as someone jammed a second gen 8.5 rear underneath it,so the OE rear & hardware is long since gone.

FWIW

Bret P.

[HWYSTR455]

First thing is to check the box for multi-leaf springs. If you don't have multis, it will be hard to deal with wrap/hop, etc.

Slappers do work, though tuning them can be a challenge. Have a handful of extra snubber bumpers.

90/10 front shocks for drag, and have someone video your launches. Then start trimming those bumpers!

A nice set of aftermarket leafs work best IMO, and you can have the second leaf extended to where it goes up to or even partially wraps the front eye, providing further control.

If you're going for drag-only, you can switch to sliders in the back instead of shackles, but then you WILL be dealing with pinion angle adjustments. That can be a challenge when using shims, because you can run out of room pretty quick.

Replacing the spring isolator pads with polys helps, but the hot ticket is to use mono-leaf perches with multi-leafs, and no pads. That obviously requires welding. My suggestion would be to remove the rear and have someone weld the tubes and check for square for starters.

Go to the track and see what's working for others. Note 60' times and launches, talk to people there. That's easy to do, and fun. You really don't need to drill down in rocket-science fashion, common sense goes a long way.

There's a chassis book by chris alston that has some really good basic info, and the read is straight forward. I can lend it to you when I bring the intake up!

Lastly, you can back-half, which is the best for a drag car. No fun on turns though (in general), so you'll be limiting where you can use the car.

.

.

[HWYSTR455]

Some stuff to ponder:

http://www.cachassisworks.com/cac_gBar.html

http://www.cachassisworks.com/c-121-...o-touring.aspx

http://www.competitionengineering.co...s/chassis2.asp

http://detroitspeed.com/productpages...uadra_prod.htm

http://www.landrumspring.com/pages/l...7&pagenumber=1

http://www.landrumspring.com/pages/l...4&pagenumber=1



.

[screamingchief]

Depending on what traction device you end up choosing to use,the spring choice may (or may not) be an issue.

I say that as some traction devices work just fine with the mono leafs.

For Cal-Tracs their "split" mono's are actually prefered over other options...

And there are also lots & lots of cars out there with Cal-Tracs on the GM mono's as well.

And with the really serious cars using leaf springs w/ladder bars & floaters,often the mono's are prefered as well.

Now with the slapper bars or the SSM type lift bars,the multi's probably have an edge with those.

So that deal can vary somewhat based on the choice of traction device to be used,so I would'nt dismiss the mono's without having good reason.

Just be careful of making assumptions when dealing with leaf springs,for instance those Landrum drag multi-leafs,they dont really need extra traction devices,if you've ever seen a set you'd know exactly what I'm talking about,they're made like they're meant for a tank,the leafs are at least twice as thick as the OE leafs are,and the spring clamps are massive,they're much like the Tri-city drag springs that are all based on the old Mopar drag springs.

Those things aint gonna wrap up,even without a traction bar to help them.

But there is a tradeoff to that,they ride like $#!t on the street,as they're stiff as he!!,so dont jump into a set of those too lightly,understand that for every choice there will be consequences.

And understand that a spring like those Landrum drag leafs are much heavier too.

At least twice as heavy as the OE leafs are.

I know because I've BTDT,as I had a set of the 250 lb Landrum drag multi's in my '73 & '74 venturas,one with SSM lift bars,and the other with Cal-Tracs.

Sliders or shackles,I dont see room for massive improvement there,the only real difference is gonna be the sliders keep the back of the springs from moving side to side a bit more than a shackle will,but so would a set of bushings like the global west stuff.

Sliders will be a whole lot more trouble to install for sure,and as stated for a minimal gain,and for all but a max effort ride,they're pretty much overkill.

And no matter what you end up with,you will be dealing with the pinion angle,no if's,and's,or but's about it.

I dont use the isolator pads at all anymore,and in my experience,the poly isolators are even worse than the rubber ones are,the poly isolators are more "slippery" and they really dont like to stay put,they like to "squeeze out" of place on you,so I would plan on solid mounting the rear from the get-go on this.

And as soon as you start messing with the pinion angle,your gonna toss the spring isolators anyways,and remember what I said about the pinion angle earlier,you will need to adjust that no matter what.

The "hot ticket" for perches is to lose the GM style spring perches completely,and going to the ford/chrysler style aftermarket perches,I think that's what HWYSTR455 was refering to when he mentioned those needing welding.

But the GM perches can indeed be made to work regardless of whether they are mono or multi,all it takes is the proper hardware and assembly pieces.

But absolutely the GM style spring perches will need to be braced some,as they are know to fail otherwise on high hp cars,and yeah the axle tubes should indeed be welded to the center section as well,IMHO that should always be done with the rear disassembled and on a rear end jig to ensure the rear stays straight after that process.

And 1/2" U bolts and hardware will be mandatory as well,no 7/16" stuff or OE "T" bolts or such.

That stuff is mostly "nuts & bolts" sorta stuff,like I said,many choices will affect the subsequent choices,so the first order of business is to decide do you wanna do this the "old school" way,or are you gonna go @ it from the "state of the art" approach,or maybe something between those two extremes.

HTH

Bret P.

[bnorris_74]

As usual SC and others offer sage advice.

The part about the leaf spring bushings and welding the axle tubes especially.

I put the Jegster lift bars on my Firebird because of severe wheel hop. They tamed it down but after installing new poly bushings in my springs fore and aft plus poly perch rubbers, no more wheel hop. First auto I've ever owned that had wheel hop. It would jump so bad that the ash tray would empty itself. LOL

I have a set of solid bushings and sub frame connectors to install yet. Then I need to weld those axle tubes.

I've also heard that if you set up your pinion snubber correctly, you can almost eliminate the need for traction bars.

[guccieng]

global west L-2's need no traction bars, and i've never had wheel hop with 400hp on the ground, 3500 stall converter and drag radials.

[HWYSTR455]

I run a 9", and used the ford style perches before. The problem with the f-body (2nd gen for sure) is that the lower 'plate' also incorporates the lower shock mount, and there's no support for it when you use the ford perch. It will 'turn' some, and eventually make the shock body hit the tire (or spring, depending on which side, they are staggered). My solution was to use the mono leaf bracket from Moser, which is made out of thicker metal, and not use the upper isolator. (sorry the pics are old, during a brake mock-up). I also modified the lower plate to be able to use U-bolts on both sides.

One thing to note is the leaf center pin, which when ordering the spring, should request longer ones.

I use the GW CAT5 springs, which have the solid bushings, and are the type with longer second (and third) leafs that go forward, which as guccieng states eliminates the need for slappers. For my app, these springs were the perfect compromise. (without having to back half)

.

[steve]

Ok. Now I'm sorry I asked ! You guys are going way over my head here. I guess maybe it takes a little more than a " bolt on " solution to get it right. I like to do as much as I can myself but I don't know about modifying spring perches and shock mounts. The rear is on the list for next summer. After some safety upgrades and money permitting. I will have to revisit this project when I am closer to it's reality. I will have many questions for sure. Thanks for all the input.

[screamingchief]

The second gen perches on the rear end use a completely different locating scheme from the first gen perches,thus the perches on the second gen rear end are different as well.

The first gens have the standard "round hole" in the perch that corresponds to the round locating pin that is on the spring.

The second gens have a "hump" like ridge deal for locating the springs in the perch on the housing.

I dont care for the second gen method of locating the rear on the springs at all,the perch on the rear end needs to be modified as SOP,that,or they need to be converted to a different style of perch,as the OE perches wont easily allow for any sorta pinion angle adjustments.

But he should'nt have to worry about that with the first gen rear,so his OE perches can be made to work here,but I still strongly recommend bracing the OE perch,and welding the tubes to the center section in the proper manner,those should be considered SOP no matter what.

The only real catch with his OE perches is he'll need to find/make a small "bushing" for the locator pin if he's gonna solid mount the rear end to the springs,as the hole in the perch is a bigger OD than the locating pin uses,as the ID of the locating hole is designed to let both the locating pin and the rubber isolator fit in that hole,and without the isolator,there is a "gap" in there.

And when you get into adjusting the pinion angle,he may need a longer locating pin/bushing to account for the adjusting "wedges" that are used for that deal.

But that's NBD really,it's just how that gets done.

And the shock mounts typically wont need to be modified at all,unless one wants to do that for more tire clearance or such (as the shock is typically the first thing one will "hit" as an obstacle with wider wheels/tires).

Most of the time the lower shock mount is incorporated into any of the traction devices one may be using.

And those usually use the OE upper shock mounts as SOP.

The only time one really changes any of that is when they choose to move the shocks inboard of the frame rails for tire clearance,and then it's strictly DIY time,as the hardware for that is almost non-existant,and what is available is'nt always all that great in terms of quality,that is typically best done by an experienced chassis shop or builder.

And if one chooses to go the no traction device route,then there may indeed be some work to do on the lower shock mounting plates,but fear not as there is plenty of hardware out there for that deal,and most anything can be dealt with without too much trouble,the trick is knowing what you need,and where to get that.

There are all sorts of ways to tackle this sorta thing,from fairly easy bolt-ons to 100% custom fabricated.

But no matter what,it'll be a learning experince for sure!

Bret P.