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Old 07-24-2012, 12:14 PM   #11
Vorshlag
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Member#: 305763
Join Date: Jan 2012
Location: Plano, TX
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(continued from above)


Suspension Upgrade Shaping Up

With only a couple of weeks notice before the event, and a tighter than normal budget, AST-USA worked with Vorshlag and Brianne to come up with a custom set of inverted AST dampers that will suit this unique Tarmac Rally setup for this car. A mix of track worthy AST 5100 inverted front struts (45mm shaft) was paired up with some inverted AST 6100 Rally (50mm shaft) rear struts, for a combination that has the proper bump travel and extreme droop travel necessary when attacking the one of a kind Pikes Peak asphalt course (and again, this year is unlike any other before, with a fully paved course). The old front struts had almost zero droop travel, which is obvious when you look at the comparison picture of the old TEINs, the AST 5100s, 4100s and 5100 Rally struts. More travel = mo better! There were many corners last year where the car had 6" of air under a rear tire. Not conducive to good corner exit acceleration when you have a driven tire in the air.

We tested with four different front struts on the car and ended up picking the off-the-shelf GD 5100 front struts after we found that they had the perfect amount of bump and droop travel. Ryan tweaked the mounting holes in the lower half-brackets on the strut bodies for maximum tire clearance. Then Erik and Stuart at AST-USA checked out and went though all of the struts in short order, and got them to us from start, to testing, to finished in under two days. It sure is handy being located next door to their shop! These struts look great and should be strong as hell on this car. Our standard Vorshlag GD front and rear camber plates will be on top of each strut, of course. To gain an extra 5mm of room for spring length our single row race radial bearingsare used in the front set - which we do on a lot of race cars. The GD rear plates/perches always use the single row radial bearings.



One way to pick custom damper and spring lengths is by checking the travel on the car. We start by removing the springs and installing the strut (or shock) + the final top mount onto the car while suspended on a lift. Then we lower the car onto the tires and allow the suspension to compress down and touch the bump stops, then raise it up to check maximum droop (we check for fender flare clearance the same way, too!)



We did this testing on both ends of the car with several dampers. Since we already had the wide body front flares completed in steel at this point, the front wheels we used were the custom-Vorshlag-run of 18x10" D-Force units, while the skinny stock wheels were tested inside the not-yet-flared rear fenders.

These tests + lots of calculations dictated the proper spring lengths and rates for the unique dual spring set-up Jason is developing for each corner of this car. The front flare is made to allow the wheel outboard enough so that a 10-12" long spring assembly can be used. In the rear, it is set up to use 11-12" of spring stack, all placed above the tire. One of Vorshlag's spring vendors, Swift Springs USA, stepped up and sponsored Brianne's PPIHC race effort this year with free set of eight springs! That was very cool and much appreciated. Jason ordered those + another twelve springs from Swift for tuning purposes next week as well as during the week of the Pikes Peak event.




Wide Body Flares - Part 1

I didn't show much flare work in my last post, but it was already well underway (we began on Day 1). I have been posting teaser pics on the Vorshlag Facebook page, which if you "like" will show you spoilers of most of our projects before they are formally written up in our various build threads (as well as new products, long-term project cars we are selling, and other news). Let's take a step-by-step look at how we're making this custom fabricated set of steel fender flares for this car. As usual, we show more behind the scenes steps than most folks are willing to share, and hold back nothing.


The factory box flares look great, but they have trouble covering more than a 255mm tire. Not good enough for Pike's Peak!

The factory 2005 Subaru STi fenders already have a modest little box flare, and instead of lopping those off and taking a short cut by welding on a new rounded flare section from a donor BMW fender flare section (like we have done on non-STI Subarus in the past), the VoMo team instead opted for an exaggerated factory box flare. This is an old fabricator's trick where you take an existing flare section or bodyline, slice open the upper section, and extend it. Seems easy, but the proper execution of this method is time consuming and tricky. We're burning 1.5 man days per corner, just in fab work.




(see part 3 below)
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Last edited by Vorshlag; 07-27-2012 at 04:59 PM.
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