How to: Installing front coilover dampening adjuster extenders

SUMMARY
You can install coilover dampening adjuster extenders to the front of a Gen III prius to allow easy adjustment of strut dampening without disassembling the car. You need to drill 1" holes about the adjusters. The attach and route the extenders with easy bends while avoiding an obstacles

BACKGROUND
So you have installed new coilovers on your car. If you have adjustable dampening, you will soon learn that adjustment of the fronts is difficult because the adjustment sits under the windshield cowl and there is barely enough room to slide a finger in to rotate the knob. If you have a strut bar installed, it is near impossible to adjust without removing the wipers and cowl. While you don’t often need to make adjustments to dampening, it is helpful to have access when you are initially setting up the car or need to tune on the fly (e.g. tighten up before heading into some nice twisties, or soften up on road trips with the family).

While adjuster extenders exist, they need some degree of clearance above the adjustment knob. This is to allow for the extender to mount to the knob. Additionally the extender cable can’t be bent at too tight of a radius to allow it to smoothly operate. With the cowl sitting roughly an inch above the adjustment knob, we don’t have enough clearance as a simple bolt on so routing becomes a challenge.

After agonizing over different possible solutions such as a home brew fabricated right-angle adjuster I decided to take a gamble and buy the manufacturer’s adjuster extender and see if I can make it work.

WHAT ARE ADJUSTMENT EXTENDERS?
Part of my problem is that there isn’t a lot of information on these things. It seems that most coilover distributers (I hesitate to call them manufacturers) offer some version of an extender. Since I have Megan Racing coilovers, I ordered Megan Racing extenders. It’s possible that they are somewhat universal, but I wasn’t going to invest in trying it out.

The Megan Racing extenders work by mounting onto the existing adjustment knob. It has a cup that slips over the top and is held in place by a set screw. A flexible metal shaft is attached to the mounting cup with another set screw. The flexible metal shaft sits in a fairly tough tube (Teflon?) to allow the shaft to rotate freely if you are tying it down and so it doesn’t rub against the car. On the other end is a knob which, again, attaches to the shaft with a set screw. The nice thing about the design is that you can shorten it by cutting down the shaft and sleeve.



I’m not sure why, but Megan offers three different lengths (my business hat says to offer one to improve cost and inventory turns). Not knowing how it would route, I bought the largest size (250mm). I’m glad I did as I needed the whole length. If Megan Racing is reading (you can send me a free product in lieu of my typical consulting fee), one improvement I would like to see is for the extender to replace the knob altogether. It would make the product a bit more compact and solid. I do have some fear that the set screw will come loose and I’ll have to tear everything back apart.

HOW TO INSTALL THE EXTENDERS ON THE PRIUS
Okay now for the good stuff…

What you will need:
· 14mm and 10mm socket / wrench
· ~250mm Coilover Adjuster Extenders
· Poster/mounting putty
· Center punch
· Large metal drill bit (~ 1”) – Note I used a step drill bit from Harbor Freight
· Paint (I used a can semi-gloss black spray paint to closely match cowl color that I had on the shelf)
· Zip ties
· Some way to seal up hole (Optional – see step 9 below)

Steps
1. Remove wipers, cowl cover, wiper motor assembly and cowl shield.

2. Separate extender mounting cup from shaft by loosening top set screw.

3. Transfer the location of the extender to our cowl to mark the drilling location.

a. Place the mounting cup on top of existing coilover existing knob with a small sphere of the mounting putty on top.



b. Place cowl back in car, trying to not disturb mounting cup /putty during installation. Once the cowl is in position, gently press down on top of knob to affix putty to cowl (mounting cup may attach as well).

c. Remove cowl and attached putty from car.

d. If still attached, gently remove the mounting cup from the putty/cowl

e. There will be a little “nipple” in the putty. That should be about the center of the knob. Using your center punch, push it through the putty and strike a mark in the cowl. Note, I used a silver Sharpie to highlight the mark so I wouldn’t lose it.​

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4. Drill ~1” hole through cowl, centered on your mark. Note, I would start with a smaller hole first and perform a test fit to see if you have actually centered on the adjuster (don’t ask how I know). If the hole isn’t centered, adjust accordingly.

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5. Clean-up holes and surrounding areas to remove burrs and dirt using file, sandpaper and cleaner of choice.

6. Paint over hole edges to prevent rust.

7. Reassemble extender and mount to the top of the existing adjustment knobs.

8. Reinstall cowl while feeding extenders through your newly drilled holes.

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9. Seal up hole around extender. This step is optional, but I wanted to lower the chance of water coming down on top of the coilover.

a. I used a piece of closed cell foam cut slightly larger than the cowl hole. A hole was cut in the center of the foam the diameter of the extender tube with a couple of ¾” slits to allow the foam to slip over the extender.​

b. The foam was then affixed to the cowl using some butyl rubber windshield sealant I had. The butyl allows removal later, and also provides somewhat of a dam for bulk water events.​

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10. Install wiper motor assembly, routing driver side extender to the front of the right mount “pillar” and to the left towards the fender. Using a longer zip tie, loosely attach extender to the mount “pillar” on the right. You just want to pull the extender far enough away so it doesn’t have a chance to interfere with the moving assembly. Fish another zip tie through one of the holes in the front of the cowl towards the fender and tie down the extender there.

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11. Using a zip tie, tie down the passenger side extender to the windshield wiper wiring harness where the harness crosses the cowl. Note, I removed the front zip tie in the picture later for clearance.

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12. Test to make sure your adjusters work somewhat well and adjust your mounting if needed. If there is a lot of resistance, you may have too sharp a bend, or the mounting cup is rubbing something.

13. Replace cowl cover and wipers.

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14. Comment and let me know if this works for you, or if you found a better idea!

 

Thanks. Hopefully someone can benefit!

The ride is definitely more of a sport ride as it is much firmer. However it isn't too bad. I'm still dialing in the dampening and tire pressure a bit for kid and WAF, so this mod is certainly helping with that.

At some point, I may think about swapping out the springs for some Swift units. I had Megan Racing coilovers on for maybe a year originally before I took them off. I was a little disappointed that the paint on the rear springs had flaked off and they were beginning to rust. The big question I have is whether to change spring rates. The MR is 4 kg/mm front and 3.8 kg/mm rear. I think I would keep the fronts at 4 kg but not sure whether to increase the rear to 5 kg.

 

The finger squeeze method works fine until you mount a front strut bar. After that, there's no easy way in.

I didn't do anything for the rears as it's pretty easy to pop off the little panel and reinsert the adjuster. You probably could use a longer allen key, but I would be worried about it getting bumped.