Narrowed I.R.S. Trailing arms

The guy who first narrowed IRS trailing arms lives in Burnaby and goes by the name of Bruce on the Samba. I am going to be talking to him soon (about the same thing) and I believe he was doing it for a lot less than $700. The first sets Bruce did were narrowed 26mm and used type 3 automatic axles (1 side is 1" shorter than type 1 axles).

I'd be very interested in a set. 

Is Bruce the same fellow who rebuilds (not sure if he still does) VW transmissions?

I'm looking for someone who has a 3.44 R&P for sale (preferably USA made) and someone to install it in my tranny.

Ron

Yes Ron, he's the guy. I've never met him, but from the posts I've seen on various VW forums, he's very knowledgable.

holy crap that's a lot of $$.

do you know how to weld?  if so, make your own.  i did, and built in my own camber/caster based on my desired ride height. (yaaaahhh)

physically cutting them is not hard, take weld a pivot point, then use a magnetic angle finder and do camber, tack another weld, double check, then do caster.  i highly recommend the tacking process.  i ran a bead first and that was stoopid on my part.  it pulled the metal too much (it doesn't take a lot to be out 1-2 degrees) and i had to recut / reprep.

also - you do need the T3 auto axles.  IIRC - only one side too.  i think it is the passengers side (the axles are no the same length)

$700 dollars …, WOW      Alright, I’ll get involved and hold your hand!

Looking at those IRS arms somebody forgot the principle of Keep It Simple. Anyway, If you just need to narrow your IRS trailing arm a 1.25” or less, I’ll share with you the easy way of doing this to a stock arm that may have you wondering, “Why didn’t I think of that”.

We’ll be narrowing the trailing arm at the INSIDE PIVOT and not at the axle assembly. So when finished if the hole is a little eccentric, the urethane / rubber bushing well take that up! So if you don’t want to take the axle out of you trailing arm, don’t.

-- First, take the arms off your car. Now assuming you’d like to narrow this arm the max, cut 1.5” off the inside pivot face of your trailing arm, obviously perpendicular to the hole and as neat as possible.

-- Now fabricate a plate 0.25” thick to weld onto the inside edge of what you’ve just cut off. Now weld this up…, obviously with a hole for the bushing.

-- Last, weld a tube the same dia. back to the other side to make up the difference that you cut off – and I shouldn’t have to tell you, but obviously brace this well.

Now, when bolting this back on your car, your TRAILING arm spring plate, is now going to be on the inside edge of your TORISON arm spring plate. I recommend the single torsion plate style for this.

The outer face of the trailing arm plate is going to be about 0.5” farther INSET than the torsion arm spring plate and this well require a shim or washers to take up this distance – This requires longer bolts and additionally use a pan head allen wrench bolt for the front bolt of the three that bolt your trailing assembly together for addition tire clearance.

I’ve included a picture of another modification that has a tubular trailing arm in the back ground with a hose clamp on the end that indicates where it’s to be cut and rewelded to the other side. Tomorrow I’ll post a clipped section (BIGGER PIC) of a PDF that’s posted in my pics showing the IRS rear end and how this is done.

David    /    dd-ardvark

Thanks David.  I'm just learning how to weld (never too old to learn something new), but I know someone who is quite good at it.

Ron

David- Interesting approach; I've never heard of anyone modifying the pivot end....

me neither.  i'd think that would be noisey.  lots of rattles / metal on metal sounds.

it's easy to cut off the wheel end.  two cuts with a sawzall and it's done.  the hard part is getting the geometry right. 

i used the spring plate mount flange as the baseline for figuring out camber/caster.

i had an extra set of trailing arms to get the geometry from (you don't need an extra set - just measure before you cut - unlike what i did ).  then i added caster and reduced camber (~2 degrees)

ALB Quote:  Interesting approach; I've never heard of anyone modifying the pivot end....

I tried this on my 1.5” Narrowed Trailing Arms for my Speedster a few years back and it worked perfectly. I ended up with 2.25” inset from stock.

MangoSmoothie Quote: me neither.  i'd think that would be noisey. lots of rattles / metal on metal sounds.

Ok…, noisy, Ummmm my description did mention that the rubber bushings would be put back into the pivot ends as is stock.

MangoSmoothie Quote: it's easy to cut off the wheel end.  two cuts with a sawzall and it's done.  the hard part is getting the geometry right. 

Stick a wooden dowel thru the pivot hole, same size as the hole. Put your new tube on the wooden dowel and welded it. The geometry per say is not being changed.

- Yes, it well make the arm longer by 0.25” +/-

- Yes, you may have to clearance your trailing arm spring plate at the shock tower.

- Yes, you may have to cut part of the shock snubber off, dependant on your tire width and ride height.

Here’s that promised picture.

David   /   dd-ardvark

ohhhh - i see what you are doing.  interesting design. 

what size tires are you running in the rear? 

nice drawing BTW.

Ummmm let’s see, 205/60/15’ all around on 7” wide wheels.

I did post a recent pic from inside my garage with a set of 195/55’s on 6” rims just as a spoof shot showing the car 2” off the floor under - Oliver356’s “New Project” title.

David   /   dd-ardvark

https://www.speedsterowners.com...ent/2135445019614866

how did i miss all those updates in that thread!

LOVE your stance David.  you car is turning out very very nice

I'm putting the picture in here cause i'm an internet guy and i'm missing stuff in this new layout/forum software...

if you lived close to me, i'd be knocking on your garage door with a sixer of beer to play fabrication.

sweet, Ok, where is the narrowing swing axle thread?

It's fairly involved; you start by narrowing the torsion housing, and then cutting down the axle tubes. I believe Sway A Way makes 3" shorter swing axles.

911-style roll center adjusters. Very nice.

Thought about that on mine but didn't want to do all the extra fab work on the inner pivots. Went with an altered pickup point on the outer end instead.

JacksHereR ALB, to your Swing Axle statement: Cory Drake has posted some super helpful info with many pictures documenting the process involved in shortening Swing axle rear ends in his. . .   . . . . . . .  .. . . .  . . . . . . . . . . . . .,  File.            (I hear the song of frog’s churping)

Justinh, to the adjustable pivot statement: At the time (2006) Porsches Chamber adjuster / Inside Adjustable pivots were about $575 and you had to remove the frame horns to use them. So I closed the garage door and created these with a blind nut that doesn’t fall off inside your frame horn.

You’re the first person to ever notice and make comment on these.

David   /   dd-ardvark