EvaResto Premium IRS Rear Air Kit install Guide



Thank you for purchasing an EvaResto Air Suspension kit. This guide should tell you everything you need to know about fitting and operating your kit, but if you have any questions or are unsure  of anything, feel free to email or call us and we’ll assist as soon as possible!

This kit is designed as an easy to fit, well performing and highly practical air ride system for IRS Type rear suspension on all years T1 cars (standard on '68- US Spec, semi automatic, 1302 and 1303 cars).

This is an ’independent’ kit and necessitates the removal of the original torsion bars in full.

Care must be taken out at every point to ensure the kit is installed correctly. Once it is in place, no ‘servicing’ of parts is required, but it is recommended that you check on the system periodically to make sure everything remains in top order.

Installation is simple with the use of this guide, however we do strongly  recommend installation by qualified technicians familiar with Air Suspension systems and Aircooled Vehicles!

Please note: This kit is designed for use with independent management types (4-way), and will perform it’s best if used as so. 2-way systems will operate it sufficiently, however wont allow for the best performance
+ ride levelling available.


Parts list

Our kits are comprehensive and come with everything you need for proper installation.

We Recommend you take some time, familiarise yourself with the components and make sure you have everything present before you start the install.

Parts supplied:

  • 2x Top Mount Halves (handed)
  • 2x FreeRoll Air Ride spring plates (handed)
  • 1x Cross-Brace Bar 
  • 2x Lower bag mount brackets (Handed) 
  • 2x Lower bag mount bracket mount plates (Handed)
  • 2x Framehorn clamp assemblies
  • 2x ‘Stiffener Bar’ turnbuckle assemblies
  • 2x Airlift 2-Bellow Air Springs/Bags
  • 2x Rear Shock Absorbers
  • 2x 1/8” NPT to 1/4“ PTC Air Fittings
  • 1x Complete Fastener kit

Fastener kit:

All Necessary fixings are packed together.
Metric tools are required for install.

  • 2x ‘U’ Bolts with Nyloc m8 nuts & Washers
  • 8x 3/8” x 3/4" Bolts (Airlift bag fitment)
  • 2x M12x140 Bolts
  • 2x M12x90 Bolts
  • 20x M12x35 Bolts
  • 8x M12x25 Bolts
  • 8xx M10 Washers
  • 52x M12 Washers
  • 32x M12 Nyloc Nuts



Get yourself and the car ready for the job.
Ensure vehice is safely lifted and supported, using safe and correctly graded equipment. Wheels off, tools at the ready.

Note: Your kit may differ slightly in visual
design to the kit depicted in this fitting guide. The kit shown in this guide was powdercoated Cream as per customers request!

Car Preparation

 Your original suspension system must be almost entirely removed for the new kit to be installed. Don’t worry though, there’s no cutting or fab work needed,
and the full kit is only bolt-on. Parts that will need removing entirely are:

  • Shock Absorbers
  • Spring Plates
  • Torsion Bars
  • Z Bar’/Rear anti roll bar assembly (if fitted)
  • Rubber Bump stops
  • Heat exhangers & tubes - Replace with J

With all of your existing setup removed, you should be left with something like this:

 Now is a good time to talk about slight Permissible Modifications, to get the car slightly lower than purely bolt-on. If these are something you'd like more info on, please see the last step, then return to this position before install. 

These slight modifications to the trailing arms are not necessary at all, but are easier to take out at this point rtather than after the install.

Now for the install guide! 

Step 1

Installing the upper mounts. These upper mounts are handed, and provide a mounting point for the Air bag. They fix to the shock towers, Torsion tube and each other. 

First up, offer up the shock absorber and slide through the M12x140 Bolt and washer. 

Next, slip one of the M8 U-Bolts into loose position over the torsion bar tube like pictured below

Then, offer the top mount half into position and push the bolt through the mount fully, securing by hand with a M12 Nyloc nut and washer.

Now, move the supporting leg of the top mount into position, and fit the M8 U-Bolt in place loosely by hand with the M8 Nyloc nuts and washers

Repeat this process for the other side.

Step 2

Tighten both top-mounts into position fully. The support leg must be located over the factory seam weld in the torsion tube, then tightened down in place fully. 

Next, Tighten the M12x140 fixings fully, pulling everything in position.

Repeat this process again for the other side. 

Step 3

Fitting the X-bar. 

Fit the X-bar in position between the two top mount halves, using the M12x25 Bolts, with M12 Nyloc nut and washer on either side. 

Once in place, tighten the fixings down fully.

Step 4

Installing the Air Fittings and bags into the kit. 

Each air bag has mounting points and a single 1/8" NPT air port. The supplied air fittings need to be fitted into these and tightened down before the bag is installed into the top mount. 

Use a thread sealant like Loctite 565 or a light amount of PTFE tape on the threads of the fitting, then thread it until hand tight into the port.

Once hand tight, tighten further with an open ended spanner by 1 full turn. The thread type is tapered, and does not need to be sent fully home to seal correctly.

Next, lift the bag into position on the top mount and secure it with 2x 3/8" screws and m10 washers. Just set this hand tight for now, so adjustments can be made.


Step 5

Fixing the lower bag mounts in place. The lower mounts are made of two parts, and are both handed. 

One part secures to the arm and lower shock mount, the other wraps around the arm and helps clamp the assembly into position.

First, lift the trailing arm upwards so the shock absorber can be fixed loosely in place in the lower mount with an M12x90 Bolt and washer.

Then, the main part of the lower bag mount can be fitted up into position.

Fit a M12 Nyloc nut and washer in place on the lower shock mount by hand

Then next, offer the remaining part of the lower mount into position, 

It should easily fit into position like shown, with the holes lining up so that M12x35 Bolts, Nyloc nuts and washers can be fitted. 

Fit all of these fixings loosely like shown. Then tighten fully, working in opposite pattern, like when fitting up a sump strainer plate back to your engine, or tightening up a road wheel.

Once these are tightened fully, tighten down the M12x90 Lower shock mount fixing fully.

Repeat process for opposite side.

Step 6

Fitting the Spring plates. These plates ae designed as an air-ride only style plate, to use stock size bushings. If your original bushes are good, re-use them and lubricate with proper grease. We recommend red rubber grease here, as other types of grease can dry out quickly leading to noisy operation. Urethane replacements are our personal preference to use here, with the correct grease again.

Lubticate the iniside of the bushes only, and re-install into the car with the original coverplate and fixings.

Secure the plate to the trailing arm with the M12x35 Fixings, washers and Nyloc nuts.

The bolts should be fitted facing outwards as shown. 

The bolt-pattern may be different from shown on your trailing arms. Different years/models of car can have slightly differing mounting holes. Our spring plates are designed to work with all years and will always have one mounting hole 'spare'. Do not worry, as long as 3x bolts can be fitted here between the plate and trailing arm, it is safe and proper.

The toe adjustment is made here, by use of the slots in the spring plate. Set the adjustment around mid-way and tighten the fixings down fully. 

Step 7

Fitting the chassis clamps. There are two full chassis clamp assemblies, one for each individual frame horn. They fit around the frame horn and give a rigid mounting point for the top mount stiffener bars. Install each one by hand first over the frame horn with 2x M12x25 Bolts, washers and Nyloc nuts 

Install these centrally (use the lightning bolt cut-out to assist), and as close to the gearbox cradle as possible. 

Tighten down fully, ensuring that they stay central and straight.


Step 8

Fitting the Stiffener bar assemblies. The stiffener bars help pre-load the top
mount assembly, making it as rigid as possible and helping to spread the suspension weight safely through the shock mounts, frame horns and torsion tube.

Bolt each stiffener bar in place using M12x 35 Bolts, washers (only needed on one side of lower mounting) and Nyloc nut. Adjust the bars by twisting, to allow for no pre load either way, then fully tighten down the M12 fixings.


In order to pre-load the top mount assembly, the stiffener bars must be tightened down (made shorter) by hand, and then turned 1/2 a turn further with an open ended spanner. Use the spanner flats machined into the rod, and once achieved, lock the assembly in place with the Jam nuts. 


The top Mount is now fully installed.

Step 9

Now the bags can be fixed in place finally. Lift the axle up so that the bag just contacts the lower mount. Use the 3/8" fixings and m10 washers to fix the bags in place. 

These mounts are adjustable. Set the adjustment around mid-way and tighten down fully. 

Go back up to the top mount, and now fully tighten down these fixings also

Do this both sides, and now the air bags are fully installed.

Step 10

Air line routing. Each air bag will need to be connected into the vehicles management system. These lines need to be connected into the air fittings in the top of the air bag, and then routed carefully and safely into the vehicle. Ensure the air lines will not chafe, rub or come into contact with any heat. Treat them like you would a brake or fuel line. 

Step 11

Final Bolt Check and Brake bleed (if lines have been disconnected at all). Bleed the brakes as you usually would when replacing a small section of line. Once done, have a final check over all the parts fitted, ensuring everything is properly tightened down, adjusted correctly and clearing. If you’re unsure of anything, please contact us! 

Step 12

Set-up. Re-fit your wheels and pre-inflate the rear bags to around 70psi. lower the car off of the supports and ensure you’re clear of any obstructions underneath the car. Roll the car back and forwards slightly to allow things to settle. Now let the suspension down fully, allowing the bags to completely deflate and the car to reach maximum drop. There should be no hang-ups, and the car should sit level side-to-side and of course, look great.

Re-Inflate the bags to maximum (100psi) and support the car with a stand or chock (as for the next part you need to get underneath)

Get under the car as best you can (making sure if course the car is otherwise supported) and inspect the bags and the area around them. 100psi in the bags is the maximum they can take to be driven on, and at this pressure, you should expect a near-standard looking ride height. Look at the bags in relation to the mounting brackets. All clear with no clearance issues? Brilliant. Otherwise, if it looks a little close for comfort, jack the car back up, deflate the bags, and adjust them on the slotted mountings.

This part is super important! It might be a pain to have to adjust the bags again, but they must never contact or rub anything under their complete operating range! A Rub-free bag is one that will last for years to come. 

Step 13

Selecting a good ride height. With the bags checked and adjusted for clearance if necessary, it's time to start operating the kit normally.
This kit is designed to be driven low, high, and everything in-between. A good starting point would be around 70psi in each bag. This should give around 3-4” of lift, great ride quality and ground clearance. You will need up to 10psi difference side-to-side to offset the weight of a single driver and no
passengers in order to maintain a level ride height, but this depends mainly on driver weight! 

The kit should start to lift at around 35psi and can be driven low. But as a general rule with all air suspension systems, you should  not operate the kit in the upper or lower 10% of it’s limits, as this can cause damage to the brackets, the chassis of your car, and the shock absorbers! Get a feel for the kit, and
experiment with different pressures and ride heights, to find what suits your driving style best.

Step 14

Now it’s time to rack up some miles on your newly-bagged VW. We recommend after the first 10, and then 50 miles or so to check over a few things, make sure nothing looks off, or has come loose. Once you’ve completed this period, standard service intervals apply, and your kit won’t need any special treatment, replacement parts or extra servicing for a good many years and thousands of miles.
We always recommend keeping an eye on the underside of your (most likely) 50+ year old classic car, but that’s just common sense ;).

Thank you very much for choosing an EvaResto suspension kit! We hope you’re totally happy with your purchase, and of course, would love to see/hear how you got on with everything so drop us a line if you feel like it!


Permissible modifications.

As mentioned at the beginning of the guide, there is a few small modifications you can make to get the car a little lower without much work. This involves some cutting of stock parts, so isn't part of the usual install guide. 

The kit itself is designed to allow some extra compression of the air bags, so will happily allow some areas to be clearanced for better drop. 

The areas that we modify are as follows:

Bump stop mounts - complete removal

Spring plate mounting flange -  trim to match spring plate. 

First up, spring plate mounting flange. 


Offer this up like shown with the spring plate, and mark it alongside the top edge. This excess material can be trimmed away like shown below

Next, Bump stop mounts. These can be removed completely, as are no longer needed and can cause clearance issues. Trim them off like shown below

These are the areas that we would typically trim down if doing an install ourselves. 

We forbid modifications to our brackets or metalwork, or any other modifications besides shown above. Poorly thought out modifications can greatly effect the safety of your suspension system and vehicle in general.