QA1 Rear Coilovers- Shorter shock option? w/ Some Koni Front Insert Talk Too

Suspension, including wheel, tire and brake.
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demo243
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QA1 Rear Coilovers- Shorter shock option? w/ Some Koni Front Insert Talk Too

Post by demo243 » 23 Jun 2020 12:14

Decided its time to swap to a rear coilover on the car. My cut Eibach springs have been working fine from a ride standpoint... but being that there is a good amount a free play at droop they are continuously not seating right after jacking up the back end - which requires then jacking it back up messing around with it and dropping it again- not the end of the world... but annoying. Also I am pretty sure by Bilstein shocks back there have seen better days anyway- so might as well upgrade the whole set up at once and get some adjustability.

Onto the QA1's

I have been doing a bunch of searching, reading and research - and there is some discussion on this setup, and seemingly a fair number of people running it, but very few part numbers and photos. It seems like the general consensus is to use the current DS602 Proma Star body - 18.75" extended 12.5" compressed with a 14" coil spring and the upper mounting adapters.

In my reading and talking with a couple people I have come across a few comments about wishing they had gone with a shorter shock - both of the main comments came from people running very low cars. Given that I am headed in that direction - main use of this car is AutoX and Trackdays (although arguably haven't been doing much of either recently...) I thought this might be worth looking into.

QA1 does offer the DS502 - which moves to a 17" extended length and 11.625" compressed. An I am wondering if this might be a better option for a low car, despite having less travel in the shock.

Basically my thought is- If the car is sitting so deep in its suspension travel you are essentially losing out on the additional 1.5" of travel the longer body provides - similar to why we shorten the front struts - so does it make sense to have the car sit closer to mid travel on the shock when resting even if its a shorter travel shock. Case in point - on my front T3 coilovers with 280z(? Tokico HZ3015) insert at full droop there is 2.5" of shaft exposed above the coil and top hat before you hit the bottom of the camber plate- which in theory means I would be better suited by a shorter travel shock (I have recently ordered some helper springs to take up that slack at full droop just for peace of mind)

Hoping to get out there and take some measurements tonight, but figured I would throw it out to the board to see what the consensus is.

Any photos of your current QA1 set up would be appreciated - Also curious on spring lengths.

For reference- here is how the car sits now on 15x7 +20 wheels with 205/50 Falken Azenis, hoping to drop the front a little bit more, likely leave the rear where it is at.
ImageUntitled by D M, on Flickr
Last edited by demo243 on 23 Jun 2020 20:05, edited 2 times in total.
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Re: QA1 Rear Coilovers- Shorter shock option?

Post by demo243 » 23 Jun 2020 15:25

To add some more food for thought.

I am currently running 350lb front springs and ~1300lb rears in the stock location. Will plan to run 350s on the QA1s.

Just checked my bilsteins and they still have some life left... but might be headed toward a suspension overhaul anyway... measured my spare front struts and they are shorter then the ones I currently have on the car. So might swap those over too since the car is lower now.

Got a few measurements taken tonight I’ll post up in a bit. Unfortunately was not able to get the rear spring out so didn’t get to measure as much as I’d hoped.
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demo243
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Re: QA1 Rear Coilovers- Shorter shock option?

Post by demo243 » 23 Jun 2020 18:07

OK-

Here are some rough measurements
ImageUntitled by D M, on Flickr

Since this is really about the rears I'll focus there---

Rear Bilstein Measured ~ 21 extended, 13.5" Compressed which leaves about 7.5" of travel. Found a number on them, but it doesnt seem to be a part number so maybe a serial number...

While the car was up I took a measurement from the lower edge of the wheel lip (easy to hook the tape measure there) up to the lower edge of the fender right at the seam. At Full Droop the gap was 8". Once down at ride height the gap was 3". So Of the ~7" of travel I used 3 of it just getting/compressing the springs to ride height. This would leave ~ 2 of shock travel--- actual travel to bumpstops I believe is about an1" roughly... those are trimmed but not miniscule.

With those measurements in mind--- the DS502 might actually suit the car better. No matter what shock with a~350 spring at my ride height there is only going to be ~ 2" of compression left so the 5.375" would be enough and the much shorter length would eliminate unneeded droop from the system.

Thoughts???


The next question turns to front options--- I have two sets of shortened 510 struts. One set on the car and one set off. The set on the car measures ~16.5" from the bottom of the complete assembly to the top of the threads. The set off the car comes in at 15.25". The tube itself on the set off the car measures 13" exactly which rough math puts the set on the car ~ 14.25".

Since I am redoing the rears, it probalby makes sense to swap the front strut inserts as well --- struts will be off the car anyway to add helper springs --- so the next question is which set would be better. I have always felt that the Tokico insert in there wasnt up to the 350 spring rate anyway so its a good time to upgrade.

Ultimately I guess the question is with the strut shorted to 16.5" (14.25" tube length) is there any chance of bottoming the strut out before I bottom the suspension out? --- seems like Koni 8610-1437 Race insert would be the best for my shorter struts.
Last edited by demo243 on 23 Jun 2020 20:07, edited 3 times in total.
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Re: QA1 Rear Coilovers- Shorter shock option? w/ Some Koni Front Insert Talk Too

Post by cartel » 23 Jun 2020 18:19

tokikos cant control over 250lb i believe--
i have koni race inserts - and im spacing the insert up about 1/2" (as i have a preset strut length ive been using for 30 years) and just space whatever insert to fit .
im running 300/ f/r - there are other factors as well- are you using heim tc rods- camber plates- heim lower control arms etc. no rear bar and 1" front bar on heim ends? my unflared car is this with 15x7 and 205-50-15s treadwear 100 tires..
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Re: QA1 Rear Coilovers- Shorter shock option? w/ Some Koni Front Insert Talk Too

Post by bertvorgon » 23 Jun 2020 18:41

We/I found 350 was just to firm for anything other than full road race. I tried them at Westwood, great when coming over Deers Leap at 130 MPH, but at the Solo, just were too solid and ridiculous on the street...at least for us.. Compliance AND control is the name of the game.

Personally, so much depends on what type of driving you really are doing, but, we found you need a good honest 2 3/4" of travel in bump to be safe.

As Mike said, it takes some custom valving to handle that and most shocks can't. I have custom valved racing Bilstiens to handle my 300's up front.
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Re: QA1 Rear Coilovers- Shorter shock option? w/ Some Koni Front Insert Talk Too

Post by demo243 » 23 Jun 2020 19:03

cartel wrote:
23 Jun 2020 18:19
tokikos cant control over 250lb i believe--
i have koni race inserts - and im spacing the insert up about 1/2" (as i have a preset strut length ive been using for 30 years) and just space whatever insert to fit .
im running 300/ f/r - there are other factors as well- are you using heim tc rods- camber plates- heim lower control arms etc. no rear bar and 1" front bar on heim ends? my unflared car is this with 15x7 and 205-50-15s treadwear 100 tires..
bertvorgon wrote:
23 Jun 2020 18:41
We/I found 350 was just to firm for anything other than full road race. I tried them at Westwood, great when coming over Deers Leap at 130 MPH, but at the Solo, just were too solid and ridiculous on the street...at least for us.. Compliance AND control is the name of the game.

Personally, so much depends on what type of driving you really are doing, but, we found you need a good honest 2 3/4" of travel in bump to be safe.

As Mike said, it takes some custom valving to handle that and most shocks can't. I have custom valved racing Bilstiens to handle my 300's up front.
350 was taken a bit from Duke, as well as to help with the additional weight of the KA. With how low the car is as well its also to help keep it from bottoming.

For other mods- right now stock LCAs and TC Rods - Camber plates set up to add a bit of caster (need to go dig up my alignment sheet) - Big front bar and rear bar which means I could actually step down in spring rate or remove the rear bar - next step will be to swap to an adjustable LCA and TC rod.

I actually dont mind the ride on the street, and with a bit more damping to slow the rebound down I think it could be pretty good. Its not a daily by any means so I dont mind a stiff ride. Once swapped to rear coilovers Ill trim the bumps or replace them with a something thinner for some more available travel.

The Koni Race inserts are more then I was hoping for $ wise, but since its all going to be apart... might as well try and balance it better
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Re: QA1 Rear Coilovers- Shorter shock option? w/ Some Koni Front Insert Talk Too

Post by Byron510 » 27 Jun 2020 00:46

I also tried 350 lbs springs with Spax racing gas inserts (VW Scirocco) and found them way to stiff. I would need to be on R compound tires and would have to load significantly at speed to make the springs work. I. Auto Xing, it was simply too stiff and resulted in excessive understeer under 50 mph. I run a Mac tiltin 1 1/8” front bar, on heim joint end links and hard compound poly bushes, 1100 lbs rear springs, no rear bar and CLSD @ 45 lbs breakaway then running 4.44 gears.

Stepping down to 300 and eventually settling on 275 lbs springs with slightly longer MR2 inserts worked well with the rest of the set up as it gave me some usable droop. On 13” tires (21” tall) , the car was crazy low. On 15’s now (23.5”), at least I’m not dragging the diff on man hole covers and I have a chance at clearing 80% of the driveway entry ramps...

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Re: QA1 Rear Coilovers- Shorter shock option? w/ Some Koni Front Insert Talk Too

Post by demo243 » 27 Jun 2020 13:19

My plan is to stick with the 350s for now- so far I have been happy with them, once I get a chance to really push it more I can fine tune it further and see about dropping to a 300. Either way even a 300 sounds like its a bit to heavy of a spring for a Koni sport inserts so I'll have to pony up for the race ones. I checked my spare struts and they are a bit shorter - 13.5" inside height which should fit the Koni adjustable race inserts nicely with a small spacer.

Also got the time today to tear about the driver side rear end and do some measuring - I assume this would apply to most any 510 running a stock rear cross member and trailing arms. Ultimately it seems like I was just over thinking everything... and the general consensus for the DS602 would be correct. Measurement from the underside of the shock mount to the center of the lower mount at full compression - trailing arm against the body is 13.5" - so no reason to go with a ds502 as I would just be leaving more travel unused. As it is the DS602 will have 6" of travel, but only 5 are usable as it is 1" shorter at full compression (12.5")

Also for anyone who is curious a 15x7 +25 w/ a 205/50 tire is a near perfect fit for the rear of a 4 door. I was able to almost fully compress the rear end ~5mm left with out any rubbing, at full compression with the trailing arm against the body there was just a slight rub somewhere, but not enough to stop the tire. Good to know.

Any way some photos for reference.

ImageUntitled by D M, on Flickr

ImageUntitled by D M, on Flickr

ImageUntitled by D M, on Flickr

Sounds- like a DS602 with a 12" spring is the way to go.
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