I have not seen a coilover set up available for first gen RX7s that is not a modified OEM strut.
I did these coilovers as a budget set up. I'm happy with how they work, but there are much better options if you're willing to spend more. I had not seen anyone who had re used the original damper insert, in my experience it works well so don't rush to buy an aftermarket insert.
What you will need:
Front:
Weld on perch
Threaded coilover sleeve and upper mount
2.25in race spring
Damper fluid
Rear:
1.9 in coilover unit. Mk1/2 Escort coilover, Mustang/Camaro etc have been used.
1.9in race spring
For the weld on perch I had a top hat piece machined to locate my spring perches nicely, but the perch can be a simple flat steel perch. You can buy one from techno toy tuning for $10 but could be made with basic tools. https://technotoytuning.com/mazda/fb/we ... ut-casings
For the coilover sleeves I bought mine from rally design. They’re universal but commonly used for Mk2 escorts with 2” strut tubes. They came with upper spring perches too, which I drilled out to match the damper rod. These cost £55. You can get these from techno toy tuning too or ground control.
I bought 2.25in 7” springs 350ib for the front. Depending on what you want from your car you may want different rates and lengths. A pair of springs are around £50, maybe cheaper.
I used motul expert synthetic for oil 10W for my damper fluid. This stiffened up the damping quite a bit and matched the spring rates I had selected well. I tried other weights before this. If you’re running lower spring rates then 7.5W may suit. I paid less than £10 for a litre of this stuff which is way more than you need. From memory each strut takes about 450ml. http://www.opieoils.co.uk/p-942-motul-m ... xpert.aspx
For the rear coilover unit my car has had the strut towers modified which allowed me to use an off the shelf mk2 escort AVO adjustable 2.25in coilover unit. For the rear of an unmodified car AVO will do a 1.9in dia unit with a post mount which will fit in the stock strut towers. You can get these in steel or aluminium body, single or double adjustable. Gaz also offers similar units with their coilover conversions, and similar units are available from techno toy tuning, or units designed for fox body mustangs, Camaros etc. The AVO and Gaz units are both £215, there may be cheaper options.
For the rear springs use a 9” 175ib 1.9in race spring. I used 2.25in but for un modified turrets you need 1.9in. I actually got 180ib rates, but that was because it was the closest available. Again a pair of springs were around £50.
Method
For the front conversion you will need to remove the front struts from the car and strip them. To remove the damper from the strut tube I used a pipe wrench to undo the gland nut, then put the tube in a vice (do not over tighten as you will crush the tube) and yank the damper internals out. Drain out all the old fluid.
You then need to grind the old spring perch off the tube. Clean up the tube so that you can slide the perch over easily.
The perch then needs welding to the tube. To find out what position to weld it, I mocked up the coilover sleeve with a gap between the top of the sleeve and the top of the strut tube.
The sleeves I used are quite long, so if you’re using ground control sleeves then you will need to have a much longer gap between the top of the sleeve and the top of the tube. The height of the perch is not critical, but aim to get the spring perch in the middle of its adjustment at the desired ride height. The perch needs to be welded securely, I had mine tig welded professionally.
Once the perch is welded on, paint the strut tube. Before assembling the coilover unit inspect the seals in the dampers and the gland nut.
Half fill the damper tube with the new fluid, then carefully install the damper internals top up the fluid with the damper installed. The fluid shouldn’t fill the tube, leave an inch or so to the top of the strut, this is to allow of the expansion of the oil as it get hot. Fit the gland nut and stroke the damper several times, and turn the strut upside down and stroke several times to bleed any air out the valves. Turn the right way up again, remove the gland nut and check the fluid level. Re install the gland nut and torque it down. To check the damper is functioning try to suddenly push it in or out. If it resists sudden movements, the damper is working. If not you have air in the valves.
Now to assemble the rest of the coilover. The coilover sleeve is likely a loose fit over the strut tube. This clearance needs to be reduced so the sleeve is a tight fit. You can either find some O rings to put over the strut tube to take up the slack (ground control sleeves often come with a selection of O rings), or do what I did and wrap the tube with electrical or duct tape until the sleeve is a tight fit. This may seem a weird thing to do, but it’s only to locate the sleeve.
The aluminium upper spring perch included in the rally design sleeve kit is thicker than the original steel upper spring perch. I had a recess machined into the bottom of the spring perch so that the spring perch sat lower on the damper rod and the upper bearing top mount located well on the damper rod. Because of this the spring seat was closer to the bump stop, so I cut my rubber bump stops in half. You need to run Bump stops to prevent the damper from being damaged if the suspension bottoms out. It’s important to check that the bump stops function with your upper spring seat, and the damper doesn’t bottom out.
Fit your bump stop, then install the lower spring perch and locking adjuster, slide the spring on, and install the upper spring seat, the bearing top mount and the retaining nut.
For the rears, remove the springs, bump stops and dampers. Install the new springs on the coilover unit, fit the coilover at the top into the tower. To install my escort rear coilovers I had to drill out the hole in the lower damper bracket on the axle to ½” to match the bush in the coilover. I bought a high tensile ½” bolt, nyloc nut and some washers. Line up the damper in the lower bracket, use washers to keep the damper bush central in the bracket and then push the bolt through and tighten up.
You may find that the spring hits the turrets on the back of the car. To correct this a bracket extension may need to be fabricated, or alternatively techno toy tuning sells a bracket which they supply with their rear coilover conversion. I did not need to use one with my modified towers.
Total spend
Perches - £8
Coilover sleeves - £55
4x springs - £100
Damper fluid - £9
Rear coilover - £215
Lower bolts - £10
Total - £397
I paid £50 to have fronts welded and some machining of the upper spring perch. The more you do yourself the cheaper it will be!
And pics of how my car sits. It will go quite a bit lower too.
