Front end rebuild project

[Bill K.]

The rebuild of my '73 wagon front end is going well. The bronze idler arm bushing is in and the centerlink end pin bushings are underway. Next up is control arm bushings. Web site in progress -> Click Here

[ubercrap]

Sweet, looks good. Thanks for the part number on the bushing! My bronze bushing was slightly shorter too, allowing the arm to clunk around a bit. After trying a half-assed solution, Ray convinced me to shim it up and luckily I found a stack of ultra-thin shims that I believe came out of a disassembled strut insert that was in the front trunk of one of my cars. I was able to stack up the shims until there was no longer any play, but the arm still turned freely. I'll try to take some pictures when I get back to Missouri to bring the wagon out to Atlanta (soon I hope).

[vwbill]

Great pics! Thanks for the post! I dont get that whole idler arm bushing and arm! The bronze bushing seems a better pivot for the bolt but shouldn't the inner sleeve move like in a cased bearing? What is the arm riding on the bolt and the top of the bushing? So is the cotrol arm bushing just rubber and you now need to heat the arm and press in or do you just burn up the bushing again?
Are the inner dia. the same for the different arm bushings?
Does there need to be the rubber in the bushing points or can bronze be used everywhere? Can you use a combo of harden case end bearings and bronze centers by cutting a standard bronze bushing? Would that be a better pivot connection or weaker? bill

[Bill K.]

Bronze idler bushing ---
Lucky find on the shims. Thanks for the tip on taking out the play. I've chamfered the ID on the head side of the fitted bolt so the head seats completely and I'll see if I can shorten the shoulder of the bolt to remove the slop.

[Bill K.]

vwbill --
Idler arm: The bronze bushing is shorter than the T4 inner sleeve, so shims or shortening of the fitted bolt shoulder is recommended to avoid vertical slop. The head of the fitted bolt rides on the non-flanged end of the bronze bushing (top) while the face of the idler arm rides on the flanged end of the bronze bushing. No inner sleeve, just bolt and bronze bushing.

Control arm:
After removing the flange ends on the rabbit bushings and removing the type 4 outer sleeves, the bushings should just press in with some dish soap. All the T4 control arm eyes appear to be the same diameter and approximate width, so the rabbit bushings could work for the rear too . The width of the rabbit inner crush sleeve is shorter than the span between the T4 frame mounts, so spacers of about .080" per side will be needed (like grade 8 washers). Also, the width of the rabbit bushing is narrower than the control arm eye, so another spacer is needed to keep the control arm centered.

Another option for control arm bushings, besides urethane, is glass-filled delrin. Here's the Porsche 944 version (although the diameter may fit, the flanges are probably to wide like those on the Rabbit bushing -- both use same rubber bushing for front -- and would not fit between the T4 frame mounts)
http://www.paragon-products.com/product_p/mc-2501.htm
...not to mention it would cost $300 to do the whole car front/rear . Two feet of 1.5" glass-filled delrin is about $50...

i've seen bronze outer shells with urethane cores, but not all bronze. I'll probably go with custom delrin front/rear.

Bill

[raygreenwood]

Yes, the solid delrin or glass filled delrin will work great on the front and rear arm bushings. In fact...I got the idea from Audi. On their S-4's...they used delrin control arm bushings.

Steel would be too hard. There must be some vibration control and a smal;l amount of flex. Hard Urethane....two part with steel center bushing and thick bronze washers on teh outer faces against the metal attaching points would probably be best....but are not as easy to machine as delrin.
I now have a new contact at seal jet. I am pricing bushing sets right now.

The control arm bushing problem is this:....The original bushings bonded rubber is just too soft. It deflects sideways when you corner. Not only does it start wearing the rubber and seperating it from teh center bushing....it causes misalignment of teh arm and thus the centerlink. The centerlink cannot stand any misalignment....so that helps wear out the centerlink. The is actually no need for any anti-vibration bushing at the idler arm. Even if vibration travels through the idler arm and steering box...through the centerlink.....it is damped by tehsteering donut in the steering column. The solid idler bushing also gets rid of part of teh shimmies.

In worn out bushings...I usually pressout the center bushing and it tears teh rubber. Then I insert a hacksaw and score the side of teh metal surrounding tube. Bewnd the edge with a punch and drive it out with the bracket in a soft jawed vise.

The bronze bushing is just a hair shorter. Thats no problem. Just put a thick boronze washer on top to keep the bolot head from wearing on teh aluminum bracket. Ray

[Bill K.]

Okay, it's been a long time, but this is still underway...

Inspired by Walter to get after the brakes again, I did some machining this weekend with the goal to fit vented disk brakes to the front of the 412 Coupe.

Instead of creating custom inserts for the 944 hubs to hold VW bearings, I decided to use a 412 front brake rotor for the insert. The 412 rotor was machined down to create a perfect fitting bearing insert and the 944 hub was bored out to accept the insert. The width of the insert is the same as the original 412 rotor. The 944 hub width was not modified from stock either. The parts were made for a .002" interferance fit. Heating the hub and cooling the insert resulted in a slip together fit which locked up on cooling.

Inboard side showing insert flush with hub:


Outboard side with recessed outer bearing seat compared to 944 (the slot in the hub will get extended inboard to remove the VW bearing cap):


Original VW bearing bores:


Inboard bearing and seal installed:


Seal raised off inboard surface just like VW setup:


Perfect spacing with 411 spindle (no mounting offset like 412 spindle), 944 rotor (282mm x 20mm), 911 "M" caliper (48mm pistons, 3" mount hole spacing):




This hub setup increases the wheel mounting offset about 8mm per side compared to stock. This is perfect for Porsche Cayenne 17x7.5 ET 55 wheels with 205/45/17 tires. See this linkfor a comparison to stock setup where the Cayenne offset is decreased to 47 to account for the increased offset of the 944 hub. Compared to stock, this combo is 25mm wider inboard and 15mm wider outboard.

My car with 165R15's on stock wheels has about 30mm inboard clearance and 25mm outboard clearance. This combo will result in about 5mm clearance between tire and strut tube (inboard clearance) and about 10mm (outboard) clearance between tire and fender lip. The car should stop good too

[raygreenwood]

So...let me get this straight. Its not quite clear from the photos what you did to the 412 rotor or where it is stilled used.
(a) you machined down the support ring around the center hub section of the 412 rotor so it could slip into center bore of the aluminum wheel spacer yes/no? Then (b) you machined that wheel spacer shown in your pictures to make sure it fit around the now modified 412 rotor hub. yes/no?
So....(c) did you end up machining completely away ....the original 412 rotor (just leaving the center hub so you could use the inner wheel bearing bore) yes/no? and finally....(d) this allowed you to sandwich the new vented rotor between the wheel adaptor and the now modified and rotorless 412 center hub? Thats the way it looks. Ray

[Bill K.]

So...let me get this straight. Its not quite clear from the photos what you did to the 412 rotor or where it is stilled used.
(a) you machined down the support ring around the center hub section of the 412 rotor so it could slip into center bore of the aluminum wheel spacer yes/no?

Yes, but it's not a wheel spacer, its a Porsche 944 NA front wheel hub with bearing bores removed for fitting the 412 bearing insert.

Then (b) you machined that wheel spacer shown in your pictures to make sure it fit around the now modified 412 rotor hub. yes/no?

Yes, but as stated, its a 944 hub.

So....(c) did you end up machining completely away ....the original 412 rotor (just leaving the center hub so you could use the inner wheel bearing bore) yes/no?

Yes, the 412 rotor was turned to about 2.375" OD full length and shrink-fit to bored out 944 hub.

and finally....(d) this allowed you to sandwich the new vented rotor between the wheel adaptor and the now modified and rotorless 412 center hub? Thats the way it looks. Ray

No, the rotor is mounted to the 944 hub just like Porsche OEM (see last picture where one bolt is holding rotor to hub). The "412 center hub" is flush with the inboard end of the 944 hub (see first picture), so it's not "sandwiched" with the rotor.

Basically, it's a 944 hub and rotor with 412 bearings.

It took a long time to machine the 412 rotor, but at least I didn't have to make precision outer bearing race bores in custom inserts for the 944 hub.

[raygreenwood]

Ah! Got the picture now. So basically the 412 hub with bearing bores was all that remains of the 412 rotor. That 412 hub with bearing bores (both inner and outer bearing bores)...just slips or presses into the 944 wheel hub...which in turn bolts directly to the vented rotor.

What car is the vented rotor from.....and...did you modify the front 412 calipers to fit (which can be done by simply inserting the caliper spacers from many types of BMW and a few other vehicles)...or are those other calipers?

The caliper spacers I am speaking of are basically thin slices (about 8-10mm)....or caliper....that Teves used on a great many brake calipers from the factory to make then "tunable" in thickness for many cars.

For example, a few years back I found cars ranging from what looked like 320i's, maybe some 325's, for sure some old 330's etc.....that had what are vritually identical calipers to the 412.
Same piston, same casting, same flange mount bolt spacing. But....they also had sandwiched between both halves of the caliper...a thin slice or spacer that had bores for the fluid to pass. In essence, it made these calipers three piece when disassembled. So they had two sets of donut/0-ring seals inside to seal the caliper halves to each other instead of the usual one set.
I kept the shim plates. I have them somewhere. By using those parts it would easily allow a stock 412 caliper to be expanded for use with a thicker ventilated rotor.
Problem is as you know, that this shim plate also moves the outer caliper half closer to the wheel so you would need deeper wheels to use even the stock caliper with....the stock caliper mounting point on the stock steering knuckle.
I also found a few four piston calipers here and there that could probably be bolted right up....again...with the need for a different rotor and spacing and new wheels to boot.

The biggest issue with 412 front brakes...in my opinion.....is the solid rotor. For as light as the car is, the swept area is decently adequate. The piston area....is pretty adequate....and much better than many stock cars of the era. But...when I finally cross drilled and chamfered my front rotors and got a much, much better pad than stock (plusa few more little adjustments).....I foun MUCH better braking. So....I am sure that a ventilated rotor would be much better.
At what point moving to a four piston caliper would be worth the effort?...hard to say. But...if you are already doing the machining to use a thicker rotor and deeper wheels....you are already there and should probably move to a four piston.....and upgrade to a 21mm master cylinder in the trunk. Cool stuff! nice work. Ray

[Bill K.]

The vented rotor is from 944 Porsche 83-86 (p/n 477-405-083A-M359). These were used on 911's and 924's also.

The beauty of this combo is that the caliper, rotor, and spindle dont need modification. Just need 411 spindles and a modified 944/412 hub.

The calipers are Porsche "M" calipers, used on early 911's and all 914-6's. They have the caliper spacers you speak of and the 3" mounting hole spacing of the 412 spindle. The M calipers have 48mm pistons which is same as the 320i caliper, but with the caliper spacers, allow for 20mm vented rotors.

The 412 brakes are great for stock size tires as they can lock the wheels when maintained properly. I'm upgrading the brakes proportional to the planned increase in tire width so traction and braking distance both improve. I think these brake/tire upgrades will be overkill for my 120hp engine. Some braking overkill is fine as long as the effort and cost is modest. This 911/944 combo fits my needs.

Going to 4-pots would require more modifications and cost and result in extra overkill. However, putting 4-pot calipers on would be great justification for getting more motor

[raygreenwood]

I have 205/60-15's. The stock brakes even with just cross drilled rotors are excellent. But...that is also with an increased volume master cylinder, stainless teflon lines and very agressive pads. The cross drilling and pads alone greatly shortened stopping distance. Ray