more front suspenion building

[bradey bunch]

Hello.
I have been working on part one of two for my front suspension (part two involves big brakes and new balljoints...)
My previous setup was simply chopped bmw springs with NOS strut inserts. Worked OK, and seemed to be an improvement handling wise over the stock cut springs in place from the previous owner. The issues with this setup were stiffness (as reported from my passengers, I dont mind a harsh ride), and the fact that the spring was too short resulting in the spring unseating in the perches when jacked up.

Anyways, I decided to build my front suspension mainly because I was lazy in letting the car down one say and the spring came half out of one of the perches, giving symptoms of a seized strut mount.

I used rabbit strut inserts by bilstein,

Sport Series (P30-0032-M1) Front (34-184530)

with this (slightly modified) strut mount : http://www.klaindustries.net/strtmnt/strtmnt.htm

and some spacers I had machined.

Spacers, you can also see the large nut that I had to have bored for the larger piston of the bilsteins. I also had the rabbit retaining nut that came with the struts machined to fit inside the strut tube so the 412 retainer would clamp on it.


Difference in the top of the struts and length


Mounts after first mods, right one is modified so aluminum is on bottom, to clear the spring seat. This lifts the car ~1"


Mounts ground to fit shock towers and studs installed in 412 bolt pattern


rabbit retainer with seal, machined so it fits inside the strut tube



Anyways, I used the chopped 412 front spring, and it was just long enough that with the rabbit insert (that is a bit shorter than the stock rabbit insert due to it being bileteins "sport" version) the spring was compressed about 1". The last guy cut from the stiffer side of the progressive spring, and so did I. I cut one additional coil but forgot to count how many were left :/

Then came the strut tower mods... 4 notches to clear the nuts on top of the strut mount. It is not a 100% bolt in, however I can still go back to stock.

So, dispite the solid mounts and high pressure monotube struts, the ride was much improved over the last setup. Alot is probably due to the fact that I was close to riding the bumpstops before, and none are required with bilsteins because they have build in bump stops.

My ride height is ~ .25" lower than with the bmw springs in the front. I estimate a 4-5" drop over stock 412 but its hard to say as I took a ROUGH measured against one of my parts cars. (and the 5" would include the drop due to slightly smaller tires on the front). It now rubs a bit on the fender over bumps on full lock. Ill get smaller tires once these wear out to fix that.
Also, I accidentally tested it against bottoming out at night in a construction zone. Hitting the equivalent of a 4" tall soft curb did not cause any bottoming out at about 55km/h.


Thanks for reading my rant, if anyone has any questions feel free to ask.

[raygreenwood]

Nice work...but a glutton for punishment you are!
The rabbit insert is the same diemsnion as the Audi 4000s...in every respect except that the Audi cartridge has better valving for a 412 application. The machined stubs for under the cartridges are the exact thing to do and what I do with the audi cartridge....in the stock 411/412 strut tube. The other difference is that the audi cartridge fits in the $12 strut tube with existing centering rings...no machining.

This is right at about 200% better rate control on compression and rebound using the stock spring and allowing about 1" of lowering average and about 2" max if you machine the upper stub slightly different.
This handles extremely well with no excessive roughness (because the valving on the Audi struts is correct for the weight and spring rate). This uses 205/60-15's for tires for no rubbing or contact anywhere at any speed.
To use all of this with the stock strut bushing you just need to machine a stub for the top of the audi or rabbit strut. If you need a blueprint of that stub I will PM you one.

For more than a few reasons I do not recomend lowering the front of a 411/412 more than 2".

(1) Other than for looks...it has no other use. 2" lowering along with appropriate mods...is quite low on these cars and looks lower than it really is....and handles fanstatstic. Excessive lowering does not increase this. It actualy adds to lift at high speeds. Been there...done that. This also leaves you with a hair over 5" clearance at lowest point of the chassis.

(2) Lowreing more than about 2" max...by using shorter strut tubes causes the angle of the control arms to be down near maximum level where they would normally be when the suspension bottoms out. This causes ...because of the angle at the end of the radius arms where they join the "eyes" in the rear center of the "T" subframe...excessive leverage....when you over rotate on excessively lowered suspension. It will sooner or later crack one or both of the eye sockets. They are not readily weldable.

Just some thoughts. Nice job though....just think really hard about the geometry of your front end. 411's and 412's are unforgiving in the front end for wearing parts out and breaking things of the geometry is wrong. Ray

[bradey bunch]

I could have used the stock strut mounts with this setup, but the other issue i had before was a shimmy, and now with the aluminum mounts there is no shimmy (the rest of my front end is immaculate, including the original center link).

The reason I chose the rabbit insert was that it seems to be the strut insert of choice for super beetles (and iirc top line parts uses the rabbit insert, they are supposed to be experts), which i figured was a comparable chassis. Also, should I later decide to change the valving, bilstein offers this service fairly cheap.

If I did make an extension for the strut, this setup may start to bottom out because the spacer would be pushing the piston further into the strut when the car is at rest because my springs are so much shorter than stock.

Also, I agree that lowering it to this degree is just for looks.

I am looking into raising the subframe and/or getting control arms made or something along those lines to change the camber and the camber on compression. this would also deal with the possibility of cracking the subframe.

Thanks for the input Ray,

Braden

[raygreenwood]

I could have used the stock strut mounts with this setup, but the other issue i had before was a shimmy, and now with the aluminum mounts there is no shimmy (the rest of my front end is immaculate, including the original center link).

Typically the stock strut mounts are only one of the causes of shimmy…but not the major one. Using asymmetrical late 412 mounts takes care of this. If they ever shimmy, they simply need a new rubber insert…cheap. But I agree…a solid mount is nice.
You should rebuild the center link if you plan to continue using it with upgraded suspension. It is the cause of about 85% of all shimmies in the 411/412 front end. They were all defective…100% of them… even brand new ones. It is a material defective. Wrong nylon on the inside.

The reason I chose the rabbit insert was that it seems to be the strut insert of choice for super beetles (and iirc top line parts uses the rabbit insert, they are supposed to be experts), which i figured was a comparable chassis. Also, should I later decide to change the valving, bilstein offers this service fairly cheap.

The rabbit strut is the strut of choice for super beetles…..but…that has virtually no relation whatsoever to the 411/412 except for very basic configuration of the front suspensions. Different weight, different spacing, totally different control arm leverage and length…different inertia…different springs and valving inside of the strut cartridge.
I’m not going to badmouth Topline…because they offer usable answers for Super beetle folks ….when no one else does. However I’m not really impressed with the result of their product. Quality yes…result…no. I have ridden in a handful of Topline super beetle set-ups and was not impressed at the choppiness and oscillation of the front end. It’s not that it was bad…it’s just that the upgrade to handling was only moderate. To have that level of feedback….it should have been a serious handling upgrade. That’s a sure sign of incorrect valving for spring rate and weight. They had to start somewhere….and they found an existing strut cartridge that they could make fit….but the valving is a bit far off what is really needed for a super….for what you can tune for with spring only.
No actually…it could be QUITE expensive for Bilstein to help you….because it may take multiple episodes unless you have a recipe or a strut insert you can bring to them to have them match.

I didn’t start by looking at the Audi cartridge. I went through about 50+ cartridges from a wide range of makes looking for one with compression and rebound valving very close to what stock is. It just so happened…that the KYB GR-2…had that valving. The oil version and the Gas-a-just version do not. This is what people do not realize. It’s what I did not realize either at the time. Valving is set for an application…..a vehicle weight, layout and spring rate combo. Then it is tweaked or adjusted to match the fluid type used. The oil filled Audi 4000 strut was fantastic on the rebound. But not enough on the compression stroke though…because our springs are different from the Audi spring it was set up for. It bottomed out too easily. I actually tried a set. The Gas-a-just was far too stiff. It broke a ball joint. I actually just got lucky that KYB makes the Gr-2…a low pressure gas cartridge. That combination along with the valving which was similar to the stock cartridge….is a HUGE handling improvement. But if you change that combo too much (excessive spring compression, new springs etc.)…you will need to find something else again.
I did a lot of experimentation and testing….but also during that I got very lucky to find the cartridge I did. I try to save people the 2 years or so of anguish and testing I did.

If I did make an extension for the strut, this setup may start to bottom out because the spacer would be pushing the piston further into the strut when the car is at rest because my springs are so much shorter than stock.

That is physically impossible. This is also why I tell people to really explore hard…...the geometry of the front end of their 411/412. With the stock strut…with that huge long rod….the car could NEVER EVER use more than about 1/3 of that total rod before reaching nearly coil bind on the springs. The control arms will bottom out on the body before you ever even approach even using half the rod length. The 411/412 control arm geometry is physically incapable of using more than about 5”-6” of total rod stroke. On the Audi/rabbit cartridge (same basic length dimensions)..you cannot bottom these out either …even with a full trunk going over speed bumps at 50 mph.

Again…explore the geometry. With the Audi/Rabbit strut rod length….you are starting with a significantly shorter rod….even so…the length of this shorter rod is longer when fully extended that the suspension is capable of compressing. All the stub extension does…is extend the length of that short rod so it can reach upward and connect with the strut bushing. The object is not make the combined short rabbit/Audi strut rod….the exact same length as the original 411/412 strut rod. To bring the front end level…we make it about 1” shorter than stock. With the front end now perfectly level…we now also have 1” more pre-load on the spring (in the ride control zone area of the spring)….the makes it even harder for the strut rod to bottom out (even if it were possible). If you want to go a little further…you can make the stud and strut rod combination be a total of 2” shorter than the stock 411/412 strut rod…which gives the car a slight forward rake…..and is slightly nicer in the wind….but makes it handle worse in braking into a corner….unless you do work on the rear outer links to take away inertia diving.

Also, I agree that lowering it to this degree is just for looks.

Nothing wrong with that. Just be careful because you can break this front end really easily.

I am looking into raising the subframe and/or getting control arms made or something along those lines to change the camber and the camber on compression. this would also deal with the possibility of cracking the subframe.

I don’t understand what you mean by the raising of the subframe idea. Camber adjustment can be added for $20 and an hour of time. Very simple. Simply scribe an elongated hole pattern at the control arm bushing bolt hole....just like that on your rear trailing arm mount. Clearance it with a die grinder into a slot shape. Then install eccentric bolts identical to those used on the rear trailing wishbones. Install an 8mm bolt about 17mm from the slot center for the cam on the eccentric bolt to bear against when adjusting. Done. You now have full camber adjustment. This used to be installed at dealers upon request.
Castor adjustment is simpler but you need to remove the subframe to have some light machine work done. This vehicle already has provision for camber adjustment but only allows you to split the difference from side to side. It affects camber when you do this so even if you did not want MORE castor…you should install the camber eccentrics bolts.
The way this works is that the two front 19mm bolts for the subframe…one on each side….screw into captive nuts in grooves inside of the chassis. If you loosen both bolts and the pivot bolt in the rear…the entire subframe can slide about 19mm to either side…pivoting on the rearward bolt. There is a slot/hole near each bolt in the front…specifically so you can slip in a pry bar to adjust this when the car is on the rack. Oddly…the rear pivot bolt is also screwed into a captive sliding nut in the chassis…but its slot moves fore and aft.
So take the subframe and have the two forward holes machined into slots toward the rear. Now the subframe can slide forward about 5/8” giving you about 3° castor…which is ideal. You can do this on a drill press if you have a good vise.

Ray,

[bradey bunch]

We will have to agree to disagree with alot of what you just wrote, and thats ok. I have read many of your posts about front ends. i agree with alot of what you said about spring rates and valving etc, but i disagree about how the length of the strut affects height. (even if i DID extend the strut, the springs would come unseated when i jacked the car up). On top of that, I am using high pressure gas struts, so the valving would be off even if I did use audi 4000 struts. But I do not want to argue much about what we do not see eye to eye on.

As to raising the subframe, on macpherson strut cars, once the lower control arm rises above the horizontal (parallel to the ground), the more you compress the suspension the more positive the camber becomes. raising the subframe allows more suspension travel before the control arms are at that angle. (the angle of the control arms is closer to stock, despite a lowered car) and makes it easier on the whole front end (balljoints!).
(its actually once the control arm is pointing upwards at an angle equal to the steering axis inclination, making a 90 degree angle with the strut tube, that this begins to happen, about 8* on these cars IIRC, but its just easier to visualize and explain a horizontal control arm).
I still like the idea of slotting the subframe.
I hope I was clear and I understand its hard to lose the meaning on a rant like this.

[raygreenwood]

(even if i DID extend the strut, the springs would come unseated when i jacked the car up). On top of that, I am using high pressure gas struts, so the valving would be off even if I did use audi 4000 struts. But I do not want to argue much about what we do not see eye to eye on.

No sir......its 100% physically impossible while using the stock spring to have it become unseated...especially since when you are using the extender stub on the Audi 4000 strut cartridge....the finished strut rod will be a full 1-2" shorter than the stock strut rod.
You DO realize that that would mean that the stock spring would be compressed a full 1-2" more...tighter...at full strut entension...right? Being that it was physically impossible for even the longer the STOCK strut cartridge to unseat the spring....being that it compresses a full 2.5" at full extension of the strut rod.....you DO realize this right? The reason why you do not...is because you needlessly cut the front springs. They would likely unseat even with shorter, tighter Audi strut rod.

Not trying to be a jerk...you are doing fantastic work....but it does not sound like you fully understand the geometry of the type 4 suspension at all.... or themodificatons I did to it.

As to raising the subframe, on macpherson strut cars, once the lower control arm rises above the horizontal (parallel to the ground), the more you compress the suspension the more positive the camber becomes.


Absolutely....but with a grand total of travel of less than 4" (in a stock car...lowered is even less)....its not a big deal. We are talking about 1-2*.....again....besides...for $20 and an hour of work you can simply install the camber adjusters like the factory didand put put the camber back to normal to offset what you lost by lowering. Since you will have even less travel due to to lowering....camber will never be an issue


raising the subframe allows more suspension travel before the control arms are at that angle. (the angle of the control arms is closer to stock, despite a lowered car) and makes it easier on the whole front end (balljoints!).


Unless you are offroading...you really don't need any more travel. If you do....then whatever struts and springs you are using are not working. I weigh about 220 (I,m fat right now)....and I can step up onto my front bumper and bounce...and the car moves less than an inch.
Have you had the subframe off yet. It does noty sound like you have. Raise it to WHERE? Its flat against the chassis in an area that just happens to be a crumple zone. Cutting and welding in this area make for a short life for this car....been there..done that. Besides....again.....geometry...geometry...geometry . These vehicles likely have the longest control arms known to man. The arc that changes by lowering out at the ball joint end.....is insignificant in terms of degrees of pivot. You didn't flatten the control arms very much. Its just really simpler to install camber adjusters

(its actually once the control arm is pointing upwards at an angle equal to the steering axis inclination, making a 90 degree angle with the strut tube, that this begins to happen, about 8* on these cars IIRC, but its just easier to visualize and explain a horizontal control arm).

Yes...I understand. what you are getting at.....but actually camber starts changing the second the arm starts to pivot (just like a swing axle). You need to remember that this is a single linkage point strut system. Its progressive and linearthrough the entire arc....unlike a modern multipoint system. There is nothing to counteract camber as you swing through the arc.
The important point that I think you were getting at....is that when the control arm becomes horizontal (90* to the strut tube as you mention).....it becomes EXCESSIVE camber....from the point of view of the geometry that was originally designed for the supension.

At the point when the control arm is horizontal....90* to the strut tube...the ball joint actually has the LEAST pressure on it.....however your radius arm bushings and eyes ...and control arm bushings....will have the most pressure on them at this point.


I still like the idea of slotting the subframe.

This one mod makes some of the largest wind handling improvement.


I hope I was clear and I understand its hard to lose the meaning on a rant like this.

Yes.....but I think you need to take a look at a couple of things before moving forward. I know you chopped the original springs in the quest for a lower font end. I think you would be far better off doing the Bill K method which is really a complete redesign around the BMW spring. As such from what I understand...it works quite well.

Mine is a repurpose built around the 411/412 spring....which actually is superb and has waaaaay more ability than the car is using. It can be compressed for better handling up to about 2.0-2.5".
I don't know how similar or different the Bilstein high pressure gas will be compared to KYB. I suspect its valving would be as different to any other. I would also suspect that if they are serving you at all and not breaking the springs in your balljoints....they are softer than the KIB high pressure units. Bilstein makes great stuff. Keep working at iT!
Either way these cars are a blast to work on.

Oh.....I have a modification you can do on a drill press that takes the pressure off of the radius arm bushings and flanges...and makes for MUCH smother operation. I can send you a sketch and some part #'s if you would like. It cost about $5 for parts...but will never wera out...is tighter than stock too. Ray

[bradey bunch]

Sure, if you could PM me that would be great!
Thanks again for the input Ray.

Braden

[raygreenwood]

Sorry for the delay i will try to get it out this evening. Ray