Volkswagen Trailing Arms

 

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Volkswagen Trailing Arms

 

 

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Lengthened Trailing Arms

These are used to increase the tire track (width) and move the tires back for more clearance as well as increased suspension travel, which is desirable for absorbing the shock of landings after jumps and allow for greater articulation over uneven terrain - such as when driving over rocks.

 

6x6 Trailing Arms

 

This can get pricey and will often necessitate longer axle rods, upgraded CV joints and sometimes an upgrade to a bus transaxle to handle the stresses you plan on subjecting your driveling to.

 

 

Arm Sizing

Lengthened arms are generally described by the amount they are widened and lengthened.  A 4x6 lengthened arm is 4 inches wider and 5 inches longer than stock.

 

 

Notching Spring Plates

This is a common practice to gain just a little bit more lift and downward travel.  It is only recommended that you notch your stock spring plates a maximum of 0.24 inches.  Notching them more than this will stress your CV joints and cause undesirable camber, even in an IRS VW.

 

 

CV Joint

The CV joints allow you to run your axles at various angles and allows the axles to piston in and out.  Without them, the axles would not be able to articulate and you would be able to run a drive suspension.  If you increase your suspension travel, you will need to account for driveling angles and consider which CV you would like to use.

 

CV Max Angle Splines
Type 1 12 33
Type 2 17 33
Type 4 22 33
930 25 28

 

Type 4 CVs joints include - Porsche 924,944 and VW-181 Thing and they all share the same flanges and stub axle.  This stub will fit into the stock Type 1 trailing arm bearing carrier to allow you to run both Type 2 and Type 4 CVs.

 

Type 2 CV joints can be used in a Type 1 if you use Type 181 (Thing) flanges and stub axles.

 

If you would like to use 930/935 Porsche Turbo CV joints and axles, it will cost you.  Besides the spendy CV joints X 4, and axles, you will need specially fabricated axle shafts and stub axles.

 

Ref:

CV joint 101

 

 

High Angle Drive Axles

These use high angle U-joints and can get pretty spending.  There is concern that they don't give like regular axles and will destroy a VW transmission.

 

 

Ref:

Highangledriveline

never seen these before, are they better that cv's?

 

 

Axles

According to Blind Chicken and others:

Size Axle Length Transmission From
Stock 15.625" Converted to IRS  
Stock 16.25" Stock IRS  
Stock 18.75" Bus, 5.75" Rear Section  
2x3 18.75"   early IRS bus 
3" longer 17.25" Bus  
3x3 19.25" Bus Trans, Stock Rear  
4x5 20.5"   Vanagon automatic transmission left side axles
5x5 21.5"   Vanagon five speed axles - most common
6x6 22.5"   Vanagon automatic transmission right side - rarer

 

Here is a listing of Sway-Away Axles used in VW applications for planning purposes.

 

Sway-Away VW  33 Tooth Axles, 2 3/8" Long Spline, Type I, II, III

Description Length Part # MSRP
Conversion, IRS Bug Trans In Bug Chassis 15 5/8" 2015 $210.00
Replaces Stock Axles In Bug Chassis 16 1/4" 2016 $210.00
Racing Applications 16 3/4" 2016-7 $219.00
Bus Trans With 3" Longer Trailing Arms 17 1/4" 2017 $219.00
Bug Trans, Stock Length Arms, 5 3/4" Rear Section 18 3/4" 2018 $219.00
Bus Trans, 3" Longer By 3" Wider Arms, Stock Rear 19 1/4" 2019 $248.00
Racing Applications 20 1/4" 2020 $248.00
Racing Applications 22" 2022 $248.00
Spiroloc Circlip, For 33 Spline VW Axles, Each NA 2410 $1.40

 

Sway-Away VW/Porsche 356 Swing Axle Applications

Length Year/Model Description Part  No. MSRP
26 11/16" 61-66 Bug Short Spline 2260 $295.00
23 11/16" Drag Cars, 3" Shorter Than Stock Short Spline 2261 $390.00
21 11/16" Drag Cars, 5" shorter Than Stock Short Spline 2262 $390.00
27 11/16" 1967 Bug Short Spline 2265 $295.00
28 7/16" 1968 Bug & Type III Long Spline 2270 $310.00

 

Sway-Away Porsche 930 28 Tooth Axles, 3" Long Spline

Description Length Part # MSRP
Porsche 930 Axle Set, 15 5/8" Long 15 5/8" 2415 $285.00
Porsche 930 Axle Set, 16 1/4" Long 16 1/4" 2416 $285.00
Porsche 930 Axle Set, 16 3/4" Long (5-16 cars) 16 3/4" 2416-7 $305.00
Porsche 930 Axle Set, 17 1/2" Long 17 1/2" 2417 $305.00
Porsche 930 Axle Set, 18 3/4" Long 18 3/4" 2418 $305.00
Porsche 930 Axle Set, 19 1/4" Long 19 1/4" 2419 $305.00
Porsche 930 Axle Set, 20 1/4" Long 20 1/4" 2420 $305.00
Porsche 930 Axle Set, 21 3/8" Long 21 3/8" 2421 $310.00
Porsche 930 Axle Set, 22" Long 22" 2422 $310.00
Porsche 930 Axle Set, 22 1/2" Long 22 1/2" 2422.5 $310.00
Porsche 930 Axle Set, 23" Long 23" 2423 $310.00
Porsche 930 Axle Set, 24" Long 24" 2424 $320.00
Porsche 930 Axle Set, 25" Long 25" 2425 $320.00
Porsche 930 Axle Set, 26" Long 26" 2426 $320.00
Porsche 930 Axle Set, 27" Long 27" 2427 $320.00
Porsche 930 Axle Set, 28" Long 28" 2428 $350.00
Special Order Porsche Axle Set Special 2400 $625.00
Spiroloc Circlips For Porsche 930 Axles, Each   2411 $1.40

 

Sway-Away Porsche 930 28 Tooth, 3" Long Spline, Racing Axles
Description Length Part # MSRP
Racing Applications 16 9/16" 32416 $525.00
Racing Applications (5-16 cars) 16 3/4" 32416-7 $525.00
Bus Trans, 3" Longer By 3" Wider Arms, Stock Rear 19 1/4" 32419 $525.00
Racing Applications 20 1/4" 32420 $525.00
Racing Applications 21 3/8" 32421 $575.00
Racing Applications 22" 32422 $575.00
Racing Applications 23" 32423 $575.00
Racing Applications 24" 32424 $605.00
Racing Applications 25" 32425 $605.00
Racing Applications 26" 32426 $605.00
Racing Applications 27" 32427 $605.00
Racing Applications 28" 32428 $605.00
Racing Applications 29" 32429 $605.00
Racing Applications 29 1/2" 32429.5 $605.00
Special Order 28 Spline Axle Set, Racing Any 32400 $750.00
Cut Fee for Pair of Axles, Racing Applications   32401 $155.00
930  C.V. Porsche Axle Set with Bubble, 28 Tooth Any 32402 $770.00
Spiroloc Circlips For Porsche 930 Axles, Each   2411 $1.40

 

 

Finding Axle Shaft Angles

The easiest way to do this is with protractor on level ground and a little guesstemating.  But if it is raining out or if you don't have a protractor, then you can give a shot at computing it.  The geometry on the rear end of the VW is a little more complicated than one may first consider.  The axles don't just move straight up and down when you hit bumps or tweak your torsion bars.  The rear suspension in part moves in an arc around the center of the torsion bar.  On IRS models, it moves in less noticeable arc that changes the camber for the rear wheels and causes the axle shafts to piston in and out of the CV joints.  And on swing axles, the axle housings force the spring plates to twist as the axle pivots more so on the transmission.

 

Longer and wider trailing arms my decrease some of the arcing effects of the suspension as it articulates, but can also add other problems - like down right improper alignment, binding, etc.  Note that the following calculators simply calculate 2 point and 3 point vectors and may not reflect exact changes on your VW after you install your fancy lengthened trailing arms.

 

Two Dimensional Angle Calculator:

Horizontal Distance: Distance:

r = sqrt(x2 + y2)

 

Angle:

arc tan (y / x)

Vertical Distance:
 
  
Diagonal Distance:
Angle in degrees:

 

 

Three Dimensional Angle Calculator:

Trans/Out Distance:

Distance:

r = sqrt(x2 + y2 + z2)

 

Angles:

Vertical = arc tan (y / x)

Horizontal = arc tan (z / x)

Total = arc cos (x / r) (where vector 1,0,0 was used as comparison)

Up/Down Distance:
Forward/Back Distance:
 
  
Diagonal Distance:
Angle Up/Down:
Angle Front/Back:
Total Angle:

 

More on the math:

  1. The two vectors are represented by:

    f  =  (1, 0, 0)T

    g  =  (x, y, z)T

     

  2. The lengths are:

    | f |2  =  (1, 0, 0)T  (1, 0, 0)T =  1 + 0 + 0  =  1

    | g |2  =  (x, y, z)T (x, y, z)T  =  x2 + y2 + z2

     

  3. The normalized vectors are:

    fu  =   (1, 0, 0)T / √ 1

    gu  =   (x, y, z)T / √ x2 + y2 + z2

     

  4. The dot product is:

    fu  gu  =   (1, 0, 0)T (x, y, z)T / (√ 1 √ x2 + y2 + z2)

      =   (x + 0 + 0)/(√ x2 + y2 + z2) = x / r

     

  5. The angle is:

    cos θ =  x / r

    θ =  arc cos (x / r)

 

The final angle calculation seems to make sense as you are comparing the horizontal distance to the new hypotenuse, which should give you the new angle of your axles if it is dropped down y inches or CMs and back z inches or CMs.  But, it's been a long time since I had to do this in school.  If this math is incorrect, then the calculator above is programmed incorrectly.  Please let me know if you think this is the case, especially if you have a solution.

 

 

Aftermarket and Other Stuff

Ref:

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