IRS Coil-Over Auto-X and Drag setups....

[bubblehead93]

So I had started to post some of this under a Steeda K-member thread I started for a reason that only made sense to me at the time and somehow I can't remember the reason...

As a result it did not have much traffic and also it would rob someone the ability to do a search for IRS coil-over drag racing setups and find it...

I have hesitated for a long time to go coil-over for auto-x because I dual purpose the car drag racing as well and wanted to be competitive at both and I could not find a lot of details on good IRS coil-over drag race setups, or at least not in the realm of "buy this kit and your done." Spent some time running H&R race springs and swapping my MM race rear shocks for Viking B225 DA shocks when I went drag racing. So I had a setup that was neither ideal for auto-x or for drag racing, too many compromises, disappointed with the results.

So I decided to go figure it out...

First I converted my MM MM2 race dampers to coil-over with front 425# and rear 650# springs...

Front...


Rear...


While I was at it I installed new bushings in the upper and lower control arms and converted the rear upper shock mount to the MM upper race shock mount with a KB rear shock tower brace...





This was complicated by the poor fit of the KB shock tower brace, there is a considerable gap between the brace bolt holes and the shock tower which the picture does not do justice to, so I ended up modifying it to work better with the MM rear upper shock mounts...

I'll post again soon with the modifications required... of note, though the poor fitment of the KB brace drove me initially towards modifying the brace, I discovered along that journey that no matter the rear shock tower brace, if you want to use it with the MM rear upper shock mounts, some modification and fab work will be required for optimum installation of the upper shock mounts...

to be continued...

 

[bubblehead93]

the MM upper shock mounts eliminate all compliance in the upper shock mount without reducing your available shock travel like some kits which install a clevis in which the upper shock eye (typically a spherical bearing for most coil-overs) which costs you a couple inches...

the kit looks like this (clipped from ebay, forgot to take any pictures of the kit before installation, note, the actual mounts are anodized black vice blue)...



From my previous post you can see that the shock tower brace is sandwiched between the top of the shock tower and the upper bushing for the shock, so if installed with a brace the MM shock mount would be on top of the brace, another 1/8" higher up than intended... no big deal if your going to run the MM rear coil-overs, a 2.25" ID spring/spring cups, no interference issues...

When you go to a conventional 2.5" ID coil-over set-up, moving the upper mount north by an 1/8" exacerbates some already tight tolerances... bottomline, the 2.5" spring/spring cups pushes the limits of what can fit in the stock shock mount pockets. As a result I pushed the MM upper shock mounts as far outboard as I could, flush with the wheel tub and slightly forward which gives more clearance inside the shock pocket. In reality this moves the CL of the shock about a 1/4" outboard and a 1/8" or so forward... this plus some trimming which I show below generates enough clearance to mount the shock in its stock location.

This caused me to modify the KB brace...



by removing the hashed out material, it allowed the brace to dove-tail into the top of the shock tower, so that the MM upper shock mount did not have to stack on top of the brace, this dropped the brace down another 1/8" and fixed much of the fit issues (well that and a little notching, hammering, and re-welding)...



apologize for the gloss black paint, realized now you can't see much as a result due to the flash...

Now for the drag racing part of the story... picked up this QA1 setup from Summit... (Summit P/N HAL-HD601S-14150 w/14" 150# springs for the front and HAL -DD701 w/10" 400# springs) plus a kit to convert the upper spherical bearing on the rear shocks into a stock style stud setup to fit the MM upper shock mount as well as 5/8" lower spherical bearings (also for the rear shocks, they come with 1/2" bearing installed, I will need to bush the 5/8" bearings to fit snug on the factory lower shock bolt in the rear)...



to be continued...

 

[bubblehead93]

The front shocks go in pretty easy, though getting the right spacer combo for the MM CC plates was a bit of a chore (to give enough stand-off between the upper spring cup and the inside of the top of the shock tower). When all done, it looks like this...



However, the rears require a little trimming of the rear of the pocket...



Then the rear coil-overs fit snug but have sufficient clearance all the way around...



I have not gotten to the track yet with the drag race setup due to a separate material issue on the car. Hopefully wrap that up soon and see if it makes a difference.

 

[SVT_Troy]

so your solution is to swap out coil overs? Your using the MM coilovers for raod racing and the QA1's for the drag strip? I assume you do your own alignments and suspension tuning?

 

[bubblehead93]

so your solution is to swap out coil overs? Your using the MM coilovers for raod racing and the QA1's for the drag strip? I assume you do your own alignments and suspension tuning?

sorry, had to do a little business travel, was out of comms...

yeah I do swap them, I do my own alignments, have a home-made setup similar to the "smart-string" set-up and some FasTrax camber/caster gages... the drag racing DA strut/shock piece is new for me, but I'm an engineer by training, I think I'm up for trying to sort it out...

 

[bleedingfordblu]

interesting set up, but cool

 

[bubblehead93]

interesting set up, but cool

I have not yet been able to take the QA1 DA coil-over setup to the track... could not ship my trailer out here to Guam when I got moved and my front/rear drag tire/rim setup won't fit in the car... normally the family is the pit crew but they flew back to the mainland for the summer...

however, been auto-x'ing a few times on the coil-over setup... simply awesome... the difference between this setup with coil-overs versus my old h&r race springs is wide... the car is so nimble, the suspension works much better... placed 4 of 17... but not due to the car, those three guys ahead of me are amazing drivers... but trashing the balance of the field of various all-wheel drive turbo imports, priceless...

r/
Andy

 

[bubblehead93]

resurrecting from the dead....

a little run with my favorite co-pilot... placed second, this is that run, behind a right-hand drive Skyline...

track is at Guam International Raceway... they have a shallow bowl of a track adjacent to their motocross and enduro tracks, results in some dry dust across the racing surface, limits how much you can use the "go" pedal...

https://www.youtube.com/watch?v=lVqVDF1AhrU

r/
Andy

 

[bubblehead93]

just for the record since some folks have commented on my daughter covering her eyes during the run... she never covers her eyes, she is using her hands to help keep her head up straight with a helmet as we whip around the u-turns on the course...

 

[bubblehead93]

another resurrection, rain permitting, I finally get to take my drag IRS setup to the track... rain, work, and occasionally family have kept me from the track for months now... the auto-x setup is money (though I am going to add MM forward offset front lower control arms and the low profile front bolts so I can set the steering rack a little further back... hopefully the drag setup works just as well...

for those not familiar (which is probably most)... the track...

http://www.guamraceway.com/

perhaps one of the worse racing surfaces I have experienced, BUT, the people are great, it is cheap, and you can make a lot of passes, and a pullied Eaton COBRA is just about king of the hill no matter how bad you run... less you break... lol

r/
Andy