rear suspension mod's

Following the previous thread on coilover shocks,, has got me thinking about my desire to adjust my IRS. I would like to lower it about 2 inches (which is about 1 outer spline, I understand). But I also wonder about the other approaches, that I have read about. One is putting a steel spacer into the springplate keeper,, which would limit the rear up travel, and increase the torsion spring preload at the same time. Thus the rear suspension should become firmer,, which would provide a stiffer ride,, but that might be desireable in light of the reduced available travel. The same effect could be achieved with the use of a travel limiting strap. But I can see where fine adjustment could be tricky.

I am also considering an empi 5/8" or 3/4" rear sway bar, to keep her flat in in the sweepers.

Thanks for the opinions and insights,,
regards,
Alan

Alan,
One route for you might be the adjustable spring plates. I'm not sure what they do for the travel but they are used specifically for adjusting ride heights. I know CB Performance makes them and I'm sure many others do as well.
By reading your post I'm not completely clear, are you trying to limit upward travel or is it an issue you're concerned about?
Oh, and the sway bar - I put one on the front and rear and there is a noticable difference. You also may want to consider the front supports that attach from the frame head to the beam. They are a nice, cheap addition that makes the front end a little more solid.

Thanks, Mickey,,

Actually,, I currently don't have any travel problems. I just want the car to sit 2" lower on the back,, and adjustable springplates would definitely do that. They would also maintain the current travel and current spring rates and ride quality. That is probably the smartest way to go.

Also, it occurs that I should lower the car first,, and then retest the roll rate. It should improve just as a result of the lower CG.

Alan

Let's talk about anti-sway bars. They have their place and, along with allowing less body roll, they can also severely affect handling. If the rear bar is too stiff, it will cause over steer, if it's too soft, it will cause understeer.

If the front bar is too stiff, it will cause the front to understeer and if it's too soft it can cause the rear to oversteer.

The best method is to buy at a minimum, one adjustable bar.

If all you can find is an adjustible rear bar then do the following:

Go to a vacant parking lot and turn tight high speed circles. If the front is understeering (plowing) then tighten the rear bar by moving the adjuster towards the center of the bar.

If the rear is oversteering (fishtailing) then soften the rear bar by moving the adjuster towards the end of the bar.

In summary, if you make an anti-sway bar stiffer, it limits the amount of lateral tire roll (body roll) and thus, less adhesion. If you loosen the bar, it allows more body roll thus more lateral adhesion

Too much rear lateral adhesion will cause understeer, too little rear lateral adhesion will cause oversteer.

I hope this helps.

Alan:

Larry brings up some good points, but I've also found that many people are only looking for a minimal change in handling (usually less body roll in corners) and have neither the time, patience or technical savvy to fine-tune an adjustable rear bar (although the way Larry explains it, I think that anyone could do it!)

Anyway, before you start tearing into your car's suspension in search of the "Holy Grail" of handling, please take the time to read this article. It's the best basic resource I've yet seen on getting your pan-based car (or tube-frame-based either, for that matter) to handle the way you would like. Once you understand what is going on, it makes it easier to decide what will give you the desired result:

http://www.aircooled.net/gnrlsite/resource/articles/handling.htm

Remember, too, that the tires you use, their width and stance (outward dish) will also greatly affect how the car ultimately handles.

BTW: Adjustable spring plates are not one of those "Holy Grail" gizmos. All they do is allow you to fine-tune your ride height after the course adjustment has been set with the torsion bar splines.

If you're going to all the effort of removing your existing spring plates to install the adjustable ones, you could have just set your regular plates to the right height in the first place. See my article on rear ride height under "knowledge".

Gordon,
Ride height has always been something of interest to me. The originals usually are much lower than ours (the top of the rear well comes down over the rim by an inch in some cases). I'm always trying to get it to look right without sacrificing ride comfort. When I first got my car it sat too high so I adjusted the read torison setting to get it lower. From there it looked great but never quite rode as smooth as I'd like (too stiff in the back and seemed to not like bumps very much). Now, since redoing the rear arms in my car, the car sits a smidge too high for my liking (I raised the rear height up again when I changed the arms). It's hard for me to really give accurate assessment of things because I've been dealing with a bunch of different things over the years (frame flex, lowered front beam and rear torsion, raised front beam and torsion, ect...) but now that I think I've got the rear shock thing figured out in my car, and I'm eventually going to get the subframe supports welded in along the rockers, I'm going to start to do some "testing" as per Larry's suggestion.
So to my point(s) - Being that these cars are based on VW chassis' but don't have the weight and metal body and/or top they were designed for, how is one to know what the cause and effect are for our cars based on VW Beetle specs? Why are the rear torsion bars adjustable in the first place?
I'm pretty convinced at this point that my current set up (adjustable front beam and IRS) has it's limits and if I want my car to handle like a "sports car" it's time for a completely custom A arm suspenion chassis requiring a frame off "hoopty-iation". Someday, someday. ;)
Right now what I'm looking for is a smooth riding car that allows me to enjoy a bit of "pushing it" when the mood strikes me.
What is the recommended setting for the rear torsion bars with stock shocks on our cars? Wouldn't it be better to set the torsion bars to where they're supposed to be (original VW setting) and then adjust with the spring plates? I saw a set of lowered spring plates on the Red 9 Design site (they come in 1", 1.5", 2"), what affect would those have on the quality of the ride versus ride height?

I'm probably NOT the best person to ask about some of this, but I'll take a stab and then sit aside to let others give their opinions, too.

First, I have a good friend from Fall River, MA, (Bob DiCorpo) who owns an original '56 Speedster. He pays others to take very good care of his car mechanically, and I believe it to be stock and "up to snuff" in all ways. I've parked next to his a number of times and often noticed that Pearl sits lower than his car, when measured at the door sill and the top of the door. I've got Pearl about as low as I care to take her, because any lower and the rear wheels will rub on the inside of the body going over bumps.

I've also noticed that other original Speedsters, besides ALWAYS being much quieter than our cars are also sitting a tad higher. The "wheel well lip covering the tire" thing could well be that their bodies have a lower wheel well top lip than ours do (especially the flared replicas that have round rear wheel wells, not flattened tops like the classics). I don't know about this, just offering it for thought.

"Why are the rear torsion bars adjustable in the first place?"

Because they come from Volkswagen pans that were used for sedans, Things and buses. They could be set to different heights as needed but the same torsion bars could be used. Nice cost savings. Also, as the car aged and sagged in the rear, they could easily be brought back to spec when the rear spring plate bushings were replaced by using different spline combinations.

Bear in mind, too, that raising or lowering the car (at least early VW's bugs) does not affect the spring rate. All it does is raise or lower the car.


"I'm pretty convinced at this point that my current set up (adjustable front beam and IRS) has it's limits and if I want my car to handle like a "sports car" it's time for a completely custom A arm suspenion chassis requiring a frame off "hoopty-iation"

Perhaps, but what is your definition of "handle like a Sports Car"? Compared to an original 356A, many replicas can out-handle the original. Compared to a Miata, they come up lacking, especially their unique ability to make the rear come around to the front!

Then there are massive handling differences between a classic, stock tired, 5.5" wide wheeled, swing arm Speedster and a flared, 7" wide wheeled, anti-sway-barred, wide-tired, IRS, slammed Speedster, both having a pan frame. Will the latter handle like a Miata? Probably better (mine handles better than a Cobra in corners). Will it handle like a Go-Kart? Nope. Will it out handle the former Speedster Replica or an original 356A? Absolutely.

"Right now what I'm looking for is a smooth riding car that allows me to enjoy a bit of "pushing it" when the mood strikes me.
What is the recommended setting for the rear torsion bars with stock shocks on our cars?"

At whatever ride height you prefer.

"Wouldn't it be better to set the torsion bars to where they're supposed to be (original VW setting) and then adjust with the spring plates? I saw a set of lowered spring plates on the Red 9 Design site (they come in 1", 1.5", 2"), what affect would those have on the quality of the ride versus ride height?"

IMHO: Adjustable spring plates can affect the ride height in the rear ONLY. They're very handy to "fine tune" ride height or balance left to right, but that's after you get them basically set in the first place.
You can soften the ride in the front by varying the amount of "height" on each torsion bar separately (which overloads one and underloads the other), but I've not played with that sort of thing - I just know you can do it.
On the rear, you only have one torsion bar on each side so all you can do is alter the height of the rear (left and right independently, but it's still just height).

The adjustable anti-sway bar that Larry talks about would be interesting to install and then play with, but I would have to be seriously autocrossing to justify all that work. It would be fun, though, to set one up and then terrorize originals in the SCCA under 2,000cc autocrosses.

;>)

Gordon,
While at West Coast Holiday in Lake Tahoe last year, I noticed quite a variance in the rear wheel opening heights among the Speedsters.
It seems the early models had lower openings by as much as 2-3".
I have not found documentation to corroborate this.
But here's a couple photos to illustrate.

Duh! Why didn't I figure out that VW used the same chassis for different cars? Now that you mention it Gordon it's obvious.

By "sports car" I was referring to something more along the Miata. But again, as you obviously point out the engine location and weight balance is the main issue when it comes to handling. Our cars are again limited by that dynamic.

I wonder how my car will be now that I have the shock thing figured out (fingers crossed). I've only been able to run it up and down the street while sitting on a phone book which is NOT the time to test things out. As soon as I get my seats back from the upholsterer I can bolt one in and go for a scoot to see how it feels. As I said, it's never felt quite right to me. After reading what you said about the torsion settings I have to wonder if when it was originally lowered if it was done properly being that the ride always felt too harsh.
I really like the lowered look and that's why I asking all these questions. The picture of Mr. Cool in his ride (below) and the red car that Terry posted shows what I was talking about. You can see how low that rear well goes over the wheel. I guess I could always "create it" with a little fiberglass down the road.
That said I have a pic (a 356 Carrera GT on the back cover of one of my porsche books), one of the inspirations for my Carrera, that shows the car sitting higher, actually right around where my car sits now. I prefer a lower look because, well, it just looks cool (again, see pic below) and I imagine it helps with handling aka Cobra Killer Nichols.

Damn! Dean had a white Speedstah, too??

And I gave away a set of Pegassi stickers at last year's Raffle!!!!!

I'm with Terry. I believe that the originals had that rear fender lip a lot lower than what we see on our replicas (although I think IM's are lower than the rest of the replicas), and because some people are going for the same, original look but with higher fender lips in the first place, they end up with their cars REALLY low (like weed beaters) which then causes other problems (usually related to handling.....)

Another thing to consider is the wheel diameter; If Dean's car had 16" wheels (he's got wide-5's on there - I just don't know what size they might be) and the replica is running 15" diameter (or the other way around), THAT will affect things, too.

Now if I could only get the same power from my Berg Extractors with the whisper-quiet of an original muffler.......

Naaaah....

Then it would sound like every other VW Beetle out there.

;>)

I would think (and you can ask others on here who've done it already) that the easiest thing to do to improve overall handling with only a small increase in ride harshness would be to install a 19mm (3/4") rear anti-sway bar on your IRS Speedster. A front one would work well, but IMHO a rear one would work better for you (if you just add one - I have both F&R and it's probably vast overkill for most driving but I'm too lazy to remove one - besides it's SOOOO much fun at the track!)

\/ Here's my 56-yr-old James Dean pose (he should look so good at 56...)

One other thing to remember is that the originals had higher profile tires than many of us run. My car sits with just 1/4 inch of the tire showing above the rim in the rear, but I am running 185's. If I lower the car any more, I'd have trouble with speed bumps. I already have trouble with some driveway - including my own. I compared the height of my spare (a 165) to my other wheels, and there was well over an inch difference.

Scroll through this (several pages) to the "transition" of 55-to-56 model years (pre-A to A models) I think that is where the wheel well changed shape. Checked all my bookmarked sites and can't seem to find the hard description of this body change...yet.
http://www.my356speedster.com/?contentid=15/

TPNuckles-See my last post; if the "rear wheel openings" you referred to were on replicas, then please disregard this and previous post; what I have posted obviously refers to original production steel-bodied vehicles. Just trying to be an extra set of eyeballs! The only thing I could add would be this:
http://www.porsche.com/usa/accessoriesandservices/classic/world/models/roadvehicles/

select model/year and you'll get a representative image

Mickey, adjustable rear spring plates also can do something very good: allow corner-balancing the car.

On my Spyder, I have coilovers in the rear and a standard ball-joint beam in the front with adjusters. You cannot adjust the front ride heights separately, unles I hack up the front, shorten the tosion leaves, and install two adjusters side-by-side. But if you adjust the rear separately, it affects the loading on the opposite corner. Think about it, if you crank into the adjuster on the LR, you are also increasing the loading or weight on the RF.

Ride height is important, but can't really be used to set up a car for totally balanced handling. What is important is weight, which is why pretty much ALL racers use scales to set their cars. If you are the same weight on the left and right sides and your alignment is good, then your car will handle exactly the same in a left or a right corner. On steel cars the fenders can be off 1/4" each side, one plus and one minus will get you a 1/2" difference! I don't even want to know how off my replica is, as the mold was taken from a repaired car and is not symmetrical. I have no idea if Speedsters are straight or not, but I wouldn't bet that they are.

Porsche 911 specs are no more than 44 lbs. difference left to right. If you can get it equal even better. I got my Spyder as close as I could, 394 lbs. each rear tire, 331 LF, 317 RF. I then added a Halon fire bottle in the RF, which brought the fronts within 10 lbs. of each other, and the back within 2 lbs. It takes time and patience, as after each tweak, you need to drive the car to settle the suspension and then drive it up onto all four scales, on a level floor. But I feel the results are worth it. Ask anyone who has driven my car(except Lane, who thinks ALL these cars have too much free play in the wheel!)

BTW, scales are coming to Carlisle. I'd rather not spend time wrenching, but if anyone wants to weigh their car they are welcome to, that's what they're there for!

Scott,
If you read my post you'll notice I referred to the West Coast Holiday, which is a yearly event for "real" 356s.
I was talking about the wheel openings for the originals.

Thanks Danny! I'm definitely in for a weight in. I've used scales for my go kart and I've gotten it about as good as possible within my limits. It makes a huge difference. By Carlisle most of the stuff I've been working on will be done so the balancing thing will be something new for me to obsess over. ;)

We could set up the scales on a trailer out on the show field and make sure it's level before getting the car up on there.....

Just a thought.

gn

Danny could make some extra coin selling scale time to some of the other car groups. Heck the dyno guys charge some unholy amount, maybe Danny could pay for his trip. Probably have to give the Carlisle folks a cut, tho'.

Though its not a Speedster this just may give out some ideas. It's the Ragonfly Project. Porsche 944 turbo swings coupled up to a BMW rearend.The engine is a mid chevy 2.8 V6 w/ a T5 trans

Gordon, I'm game if you are. Who has a trailer we could use?

Either that or some flat blacktop would be fine, the trailer would be good if someone needs an adjustment.

Should I also bring the camber gauge and toe plates?

Dan: Extra stuff is up to you. I'll have my open-deck trailer there anyway and can easily park the rig on the show field.

gn

Mickey, you're halfway to "hoopty-iation" already.
I'll ask Teresa to pack a Sawz-All.