4-link Spyder rear

550AUS, here's some photo's of what is going in my Spyder at Vintage Motorcars (VMC). I'm using a Suby EJ25 2.6 ltr. engine and Suby 5 speed trans from a Forester.

This part was designed and built by a guy who builds formula car frames and suspensions in Santa Ana California.  Perhaps these photos will get you off on the right foot for your design..........Bruce

The tricky part will be getting the IRS axle's and CV joints in there.  It can be done but it will be tight and necessary to allow room for geometry adjustments.  Exhaust system routing in a Suby Spyder can be a little difficult.  Some have gone over the top. We are striving to go  under.   Tiger @ A-1 will do it  and I think he said it can go under with all stainless and I think 4 small mufflers that are like "Y" connectors.  I've seen one done and it's really clean with the big oval exhaust tip exiting right in the center.  Tiger's the man when it comes to this kind of fabrication.  I'm always amazed when I visit his shop.  He does all sorts of exhaust systems.

I won't be using Wide Five wheels and brakes as shown but they obviously will fit as shown in my photos...........Bruce

@aircooled posted:

The tricky part will be getting the IRS axle's and CV joints in there.  It can be done but it will be tight and necessary to allow room for geometry adjustments.  Exhaust system routing in a Suby Spyder can be a little difficult.  Some have gone over the top. We are striving to go  under.   Tiger @ A-1 will do it  and I think he said it can go under with all stainless and I think 4 small mufflers that are like "Y" connectors.  I've seen one done and it's really clean with the big oval exhaust tip exiting right in the center.  Tiger's the man when it comes to this kind of fabrication.  I'm always amazed when I visit his shop.  He does all sorts of exhaust systems.

I won't be using Wide Five wheels and brakes as shown but they obviously will fit as shown in my photos...........Bruce

Thanks Bruce, some excellent photos and information, much appreciated. I'm not at the stage where I'm ready to start fabrication, but I like to do a bit of research and have some idea of where I'm headed.

I'm assuming those lower frame rails were moved and the bracing added. I see you've also added a support bracket to the transaxle blocking plate 👍

Thanks again, I'm sure I'll be using these pics for inspiration going forward.

Cheers Paul

Paul.....Yes the frame rails are moved in for a Suby install.  Yes, nicely cross-braced as well.  This is to  support the stress created by the suspension when it was  moved from the old torsion bar system / swing plates to this coil-over-shock arrangement.  Moving in the frame rails also allows room for the lateral arm attachments, space for the drive shafts/CV joints/brake assembly and more choices for the exhaust plumbing.

Mind you, I am only trying to explain what I think I learned from talking to Greg and seeing it done on my car.  He knows his stuff !  If he doesn't know he'll find out. If he needs outside help, he gets it.  That kind of guy............Bruce

Sounds like a good guy to have working on your car 👍

Your description and the logic behind the changes made perfect sense, so you must be learning by osmosis 😄

I'm assuming that's a VMC frame? I'm starting off with a Kitman frame, so there'll be a bit to add, and a bit to change as well

Thanks for those pictures, Bruce.

Your rear suspension is actually a 3 link. There is a single trailing arm and one pivot point up front. This is pretty similar to what Chevrolet did on the first Vette suspension, although they used a transverse leaf spring. This is actually the design I came up with to modify my existing Vintage Spyder(but I have decided NOT to change it at this time).

I think I could fit this into an existing Vintage chassis and still use the same under-slung exhaust, although it is VERY tight in there. I drew it up on paper anyway. Of course, I'd stay with a VW 4 speed and aircooled type1. But it absolutely could be accomplished.

Add a tunable rear anti-sway bar and you'd have an excellent rear suspension. Get the front suspension re-designed as well and we'd have a world-class chassis.

It is excellent that Greg got this done for the future of the cars. The ability to use IRS in the rear really opens up engine and transmission choices.

For my needs and desires, the juice wasn't worth the squeeze. The rear swing axle can work VERY well with travel-limiting straps to keep the rear camber negative. Reigning in the jacking effect makes the rear end stick while maintaining predictability.

i'm already jealous about bruce's car....it is going to be NEXT LEVEL!!..and make all our plastic cars obsolete!!!...still can't wait to see it..bummer i dont even fit in the passenger side for a ride

Thanks for your positive comments Danny.  I am mindful of a lot of things that I want to do to the car when I get it.  Sway bars are at the top of the list   "Tunable" you said.   I see that as one with turn buckles for the iinks connecting the bar to the suspension.  Is that what you mean ?  Yes limiting straps are on the list too.  I am disappointed that I didn't get a good suspension in the front.  Lord knows Greg tried but as you know, that would probably require a whole new design and fabrication of the front frame and the body. So what I ended up with is a std VW front ball joint system .  However, the steering will be an equal length tie-rod, Rack and Pinion steering box. That will be an improvement.  In the next few months I will be communicating with John @ OUTFRONT  about upgrading my Stinger ECU to something better.

550AUS......Keep track of Danny on here.  He is, in my opinion, the resident expert on all things Replica Spyder and a very capable technician, builder and craftsman.  He has earned the respect of many worthy people on this site.  He could walk on water but I'd bet his preference would be something like battery acid !  Ha Ha ! Thanks again Danny.

Bruce

He’s also a pretty good guy to have a beer (or several) with.  Don’t tell him I said that though, or he’ll get a big head.

Thanks Bruce!

Thanks Lane: See you in a few weeks!

@aircooled posted:

Thanks for your positive comments Danny.  I am mindful of a lot of things that I want to do to the car when I get it.  Sway bars are at the top of the list   "Tunable" you said.   I see that as one with turn buckles for the iinks connecting the bar to the suspension.  Is that what you mean ?  Yes limiting straps are on the list too.  I am disappointed that I didn't get a good suspension in the front.  Lord knows Greg tried but as you know, that would probably require a whole new design and fabrication of the front frame and the body. So what I ended up with is a std VW front ball joint system .  However, the steering will be an equal length tie-rod, Rack and Pinion steering box. That will be an improvement.  In the next few months I will be communicating with John @ OUTFRONT  about upgrading my Stinger ECU to something better.

Bruce: What is wrong with the Stinger?

Also, you know that I sent Greg the rack and pinion kit that he is using to set your car up? I sold that to LI Rick.

You shouldn't need limiting straps, they are really only needed for swing axle cars.

Your IRS rear suspension should work nicely.

Custom anti-roll bars front AND rear would be great. If you could adjust the length of the torque arms on the bars that would be an added bonus to change the spring rate, effectively making the bar any rate you want. Changing the length of the end links is only needed for initial adjustment.

Danny......Yeah, I thought about the limiting straps after I hit send button.  I have seen a sway bar with splined ends like the rear torsion bars on a VW.  Maybe on here.  It looked to be what I wanted.  Hopefully it's available in various lengths. Probably have to find someone to broach some splines in the end levers.

Rick and I have been comparing notes for a while now.  I saw the box installed on my car for mock-up.  It will work nicely.  Perhaps a little gas tank mod due to the radiator going in up there bur Greg said he may be able to work around that.  Lots of things to encounter when prototyping.  You know, change one thing and need to adjust 10 others !

The Stinger, I am told, doesn't have a warm-up cycle in cold start. This means that at start-up, the engine runs rough like a modified VW engine.  I can put up with that just like I always have with any VW's I've owned....... but since I'm going away from carburetor style fuel induction to a supposedly smoother and more sophisticated system,  I think it shouldn't have a cold start rough idle. I understand there are a couple things that need to be installed in the fuel system on the engine as well.  If all this takes a ridiculous more amount of money,  I'll live with the rough idle on cold start.............Bruce

Bruce, since I did the Speeduino EFI on my car, I'm kinda familiar with injection. I have yet to get mine programmed for cold start. I even bought a stepper IAC from a Chrysler and installed the stepper driver on my ECU board. Mike Pickett was a MASSIVE help to me with tuning.

I don't know what model the Stinger ECU is, but ALL aftermarket ECUs I've heard of have some form of cold start enrichment along with a method of adding extra air. More likely, Outfront just doesn't deal with it as it isn't a major deal.

There are many ways to add both extra fuel before start(a couple squirts before cranking) and ASE(after start enrichment). Most are coupled to your temp sensor(in your case screwed into the head or block water jacket). Extra air can be a simple solenoid-controlled calibrated air leak, a PWM frequency valve, or an IAC(as previously mentioned).

In any case, it isn't a major hassle without it and runs slow/rough for about a minute then smooths out. After that, it drives just like any modern EFI car. Smooth and tractable, all the way. Dude, you live in California. It will take about 15-30 seconds.

As far as custom swaybars, Lenny had square ends machined on his front bar and custom arms with square holes. I think he had roll pins to keep it together.

On mine, I just Tig welded the torque arms onto my old early-911 round bar. Mine is mounted with removable brackets and split bushings. I welded a couple flat plates with nuts welded on the backside right to the beam.

Thanks to all, for the information and photos, it's all going into the memory bank for future reference 👍

I was looking through an old kitcar magazine last night and found an article on the merger between ACI and Vintage Speedsters.

They had a photo of one of their offerings, an "ACI Vintage Spec Series Racer (VSSR) 550". It's got custom IRS from the factory.  Did many of these get made, or has anyone seen this car since?

The issue I see with the ACI suspension is the links are equal length.  When the suspension droops, the camber will go positive.  This is the same issue as a swing axle suspension.  The new Vintage Motorcars design has unequal length links, so the suspension will stay neutral or go a little negative camber, which helps handling.

@LI-Rick posted:

The issue I see with the ACI suspension is the links are equal length.  When the suspension droops, the camber will go positive.  This is the same issue as a swing axle suspension.  The new Vintage Motorcars design has unequal length links, so the suspension will stay neutral or go a little negative camber, which helps handling.

I've been absorbing as much as I can on suspension fundamentals lately, but you might have to explain that issue for me, or point me in the direction of some reading material. I was under the impression that keeping the top and bottom bars the same length kept the (in this case) camber uniform through the wheel's travel?

Equal length arms make for a straight up and down wheel travel parallel to the center of the chassis and perpendicular to the ground. That's nice, but when the top of the chassis rolls out during cornering, so too the top of the wheel rolls into positive camber with equal length arms (its a parallelogram).  If the top arm is shorter the travel could be kept perpendicular to the ground (no camber) during roll, or by shortening the top arm further the camber can be made to go negative (top in) during roll. Because tires flex you need some negative camber to keep the tread flat on the road. And we haven't even added the positioning of the pivot points to our design yet!

If you picture it in your head you can see why a swing axle should, and does, work very well on the outside tire which bears most of the load. As the car rolls the tire goes into negative camber keeping that tire planted. Travel limiting straps and a camber compensator work to control the unloaded tire and keep it from tucking under during rapid transitions, the dreaded jacking. The irs set-up makes control of both tire easier, plus the amount of camber gained during roll can be independent of the length of the axle.  But even with all that when done right a swing axle can be made to handle quite well indeed. Ask Danny. He can drive rings around irs cars in a properly set up swing axle car. Everything has compromises. Choose wisely!

Just as an aside modern cars use multilink suspensions with low profile tires in order to move the flex (that we see in the tires of our beasts) into the bushings of the many links of the suspension. The flex can be more tightly controlled there and more predictably tuned by the ride engineers to reduce some of those compromises. Still can't remove all of them, though!

Excellent, thanks mate. That makes perfect sense now.

Calculating the required difference in arm length should be simple 😬😀

Hello everyone.  Been off line for a few days.   I am in Loreto Mexico now.  900 miles South of Arcadia. Enjoyed all these comments and they were helpful to me.

Danny...you say you welded the right angle arms onto your round 911 anti-roll bar. I guess you weren't concerned about dis-tempering the steel bar at the ends and obviously it hasn't broken yet.  I could do the square end mill job and matching right angle arms but your idea is certainly cheaper and more expedient. What was your logic in trying it that way ?

Hot down here. It's  in the hundreds.  Ocean temp is 88 F.  Perfect for diving with no wet suit.  Just a tank, regulator and 8 lbs of lead on my belt.  I really feel naked when I jump in !  The surface has been glassy calm every morning until about noon.  You can see the cloud formations mirrored on the water for miles into infinity.  Dorado, Black Marlin and Dolphins can be seen as we skim across the water at 3800rpm. The twin 115 hp counter-rotating Yamaha's just hum in a resonant tone that's easy on the ears as we fly over the clear, deep blue,  water. .............LG. !   (Life is Good)

@aircooled posted:

Danny...you say you welded the right angle arms onto your round 911 anti-roll bar. I guess you weren't concerned about dis-tempering the steel bar at the ends and obviously it hasn't broken yet.  I could do the square end mill job and matching right angle arms but your idea is certainly cheaper and more expedient. What was your logic in trying it that way ?

I bought some 3/4" steel rod and drilled a 16mm hole in it. Then the rod/tube was welded to the torque arms. The sway bar slid into the tubes and was welded on the end and in a circle around the end of the tube at the junction with the bar.

Expediency and cheaper buttons both pushed.

It was TiG welded, a little at a time with PLENTY of cooling time so the temper wasn't ruined. It just took time and patience. I MiG-weld(most people use TiG) transmission 3-4 gears to the synchro hubs too. As does everyone else in the VW world. Sometimes, welding is the way.

Anyway, the twisting takes place along the whole length of the bar, not just at the ends. It works fine, and hasn't broken yet after 4 years of hooning.

What are the thoughts of the brains trust on this setup? It's an older modified Beck chassis, running a Porsche 5 speed (I think)

To my eye, it looks simple but effective, but I'd be interested in hearing opinions either way.

Would the upper link running diagonally to the rear provide some anti-squat functionality?

Are the swing plates still in there ?..........Bruce

No, Bruce, I don't see any swing plates. The pictures show a suspension with a lower control arm with a provision for toe adjustment, and two upper control arms/links that also have the ability to be adjusted for length. It's hard to imagine that the arc of a swing plate could coexist happily with those. Those coilovers also make it look like there's no more torsion bars.

@550aus It's possible that the upper control links are helping give an anti-squat geometry, but we'd need a drawing or the ability to look at it in person to figure out what the path of the rear wheel actually is with that set-up. Alternatively if we had square views from the side, both at full droop and full compression, we could figure out the approximate angle of instance from the wheel/axle path.

Here's a LINK to a youtube vid that explains anti squat really well including how you can calculate it for an existing vehicle.

@JMM (Michael) posted:

No, Bruce, I don't see any swing plates. The pictures show a suspension with a lower control arm with a provision for toe adjustment, and two upper control arms/links that also have the ability to be adjusted for length. It's hard to imagine that the arc of a swing plate could coexist happily with those. Those coilovers also make it look like there's no more torsion bars.

@550aus It's possible that the upper control links are helping give an anti-squat geometry, but we'd need a drawing or the ability to look at it in person to figure out what the path of the rear wheel actually is with that set-up. Alternatively if we had square views from the side, both at full droop and full compression, we could figure out the approximate angle of instance from the wheel/axle path.

Here's a LINK to a youtube vid that explains anti squat really well including how you can calculate it for an existing vehicle.

Thanks mate, I've watched that video a few times now 😄 . All of his videos are quite good actually.

I've spent the last few months watching video tutorials and reading a couple of books on suspension and chassis design generally.

That suspension in the photos seems to tick a few boxes, but like you said, without better photos it's hard to see what angles are at work there. I mentioned that top diagonal link, as it "seems" to be angled downwards to the rear, whereas the bottom links are all in the same plane.

I don't think the top rearward link is angled downwards. It looks to me to be on the same plane as the top of the knuckle/upright.

The upper links are shorter than the lowers, giving negative camber in compression and droop in relation to whatever camber is at ride height.

@DannyP posted:

I don't think the top rearward link is angled downwards. It looks to me to be on the same plane as the top of the knuckle/upright.

The upper links are shorter than the lowers, giving negative camber in compression and droop in relation to whatever camber is at ride height.

You're probably right, it's hard to say from the photos, if there is any downward angle on that link, it's not much at all. I only asked as a lot of custom independent rear suspension designs use trailing arms of some description, whereas this relies purely on something closer to wishbones in theory?

..and yes, the length of the upper and lower links seem to be correctly designed for camber 👍

Wishbones=racecar!

@DannyP posted:

Wishbones=racecar!

What are your thoughts on the design in those photos?

The only principle I can think of that it seems to lack is the anti-squat geometry. I'm not even sure how important that is on a mid-engined car as light and as low as a Spyder? I suppose the builder in this instance is relying on the shocks to take care of that.

OK, honesty time.

You are using a VW beam in the front, yes? If so, nobody has any idea what effect this particular IRS would have when combined with a VW beam. Nobody(except the owner of the modified Beck in the pictures above) knows. IDK what front suspension that car uses, either.

We could tell you a bunch of information if you were asking about a swing axle rear in combination with the beam in a mid-engine Spyder.

Some guys(not me) could tell you about VW IRS and a beam, but probably NOT in a mid-engine configuration.

You might try and get in touch with one of your fellow countrymen who has a McRae Spyder.

I guess I'll just have to find out after it's built 😄

If I build enough adjustability into the IRS it should be doable.

All of the McRae Spyders I know of are running a conventional vw beam and swing axles.

Interesting. I know some had Suby engines and I thought they all used a Suby 5 speed and custom CV axles.

But I may be mistaken, it's been at least 15 years since I saw pictures of one.

Spyderclub.com was the place to be, we had thousands of members there back in the 2000s years.

Interesting. I'll have to dig a bit deeper. I only know of three or four, and they're all vw tech.

I don't mind that this thing I'm building has a VW front end, with all it's limitations. I think having to design and build a front suspension from scratch would push me over the edge. Even adapting an off-the-shelf solution seems to be problematic from what I've read.

I agree. It's tight up front no matter what way you go.