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Last Post 17 Mar 2013 06:32 PM by  Paul V
AST 4150 Shocks Have Arrived At Vorshlag
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03 Dec 2012 08:56 PM

    All New AST 4150 Damper is here!

    After discussing these shocks last December, testing pre-production 4150 sets from July until now, and working with AST-USA on valving since 2011, the all new AST 4150 coilover monotube dampers have finally been built and are in the USA. The first pallet of 4150s shipped out of the Netherlands to the USA in late November and it has arrived in Dallas. The entire allotment was of BMW E36 and S197 Mustang 4150s, and all of it was purchased by Vorshlag. We are extremely happy that they have finally been produced and have arrived here!!!

    We have been testing with these from early on and we believe fundamentally that the AST brand is an excellent racing/street damper, so Vorshlag bought the entire 2012 production allotment of 4150 coilover kits. We should start seeing more shipments early next year, as all of the development and initial tooling and manufacturing delays seem to finally be solved on about a dozen models. On the S197 Mustang kits, we make and include some custom parts with each order, like this rear ride height adjuster platform and modified OEM upper rear shock mounts. These make the 4150 install easier and make them work with the unique rear shock arrangement we insisted on (for maximum stroke travel).

    What is the 4150?

    There is a huge list of updates to the outgoing 4100 model that were incorporated into the new AST 4150 design. This new model basically builds on the basic architecture and market success of the AST 4100 series monotube single adjustable damper, and brings experience learned in the GRAND-AM Continental Tire Sports Car Challenge, including new technology developed specifically for GRAND-AM racing teams. There is also some technology sharing from proven Moton Suspension dampers that have made their way into this strut. I have written at length about the various updates that the 4150 addresses, and you can read them in this thread post.

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    Two of the Vorshlag test mules used in 4150 development and testing.

    After initially developing the 4100 model from a previous Sportline I shock in 2006, AST-USA has worked hand-in-hand with AST Holland for the past seven years tweaking the 4100. In 2010, they decided to make a substantial number of updates and the 4150 was born, which itself has been in development for about two years. We here at Vorshlag helped a little with fitment and valving feedback since early 2011. Two of our shop cars were used in 4150 development, including with our 2011 Mustang GT and 2001 BMW 330Ci.

    Above is the exploded view picture of the revised 4150 strut, which points out many of the updates over the outgoing 4100 design. All of these upgrades and new parts have been tested on various race and street cars, including the DDP pistons, low drag seals, and new top and bottom guides. About a dozen pre-production 4150 models were built and tested on various street and race cars as well. This shock is ready.

    The biggest update that you can feel is the valving and piston. AST's extremely digressive "DDP" piston was developed for GRAND-AM racing and gives drivers and race engineers the best of both worlds. Drivers love the low speed damping response and body control, while race engineers love the “blow off” (the knee point digression, shown in the dyno plot below), with a tapering off of the rebound forces at high shaft velocities. An unintended benefit of this piston was exceptional ride quality at high bypass settings (softer rebound knob adjustment).

    When the rebound adjustment is set to soft, the damper curve looks similar to an OEM street shock profile. When the rebound adjustment is set to firmer settings, the damper curve looks like a race shock. The most critical portion of the dyno plot area is affected the most - the portion at low shaft speeds. So much in racing happens at 0-3 inches per second shaft velocities, and that's where these pistons really step up the damping forces, when adjusted firmer. The graph of shock dyno plots for typical compression and rebound curves from the 4150 are shown above. The changes are from adjustments to the rebound knob every two clicks (of twelve), and you can see the digressive nature of the plot. Basically, the super-digressive curve for the rebound that these new DDP pistons can achieve makes for a “Jekyll and Hyde” shock - one that offers a soft street ride and firm race car track performance in ONE shock - all with the turn of a knob.

    Vorshlag's 2011 Mustang GT track testing with DDP pistons and 4150 valving at the bumpiest track in Texas (ECR).

    I can tell you from first hand experience on multiple 4150 equipped cars - it works. Adjusting the knobs on the prototype AST's in our 2011 Mustang with the DDP pistons made a night and day difference - with more adjustment potential and valving change than I've ever seen in any shock. We were driving it at one of the bumpiest tracks around earlier this year on the 4150s and were able to get the track set-up dialed in quickly, still soaking up the bumps but with sharp turn-in and controlled braking. When turned down to full soft for the drive home from the track, it rode like stock. We have taken a number of people for rides in the car on the street at full soft and they think it is the OEM suspension. Riding in a car with 4150s will make you a believer.

    We have since switched to Moton remote reservoir double adjustable race shocks (that cost 2.5 times as much as the 4150s) on our '11 GT. While it is a tick faster on track with the full-tilt-boogie race dampers, even with everything turned down to full soft the street ride on the Motons doesn't even come close to the 4150s - with the exact same spring rates.

    Fixes To Some 4100 Issues

    The history of the 4100 isn't all roses and snowflakes. The vast majority of 4100 users had little to no issues, but a small percentage of folks explored the limitations of these dampers. That data was used to make the 4150 better in every way. There was always constant quality improvement in the 4100 product line throughout the seven years of production, but several updates were found that required a fundamental redesign to the 4100 strut and shock bodies. Let's back up a bit...

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    The AST 4100 model sold extremely well since 2006 because it was a unique damper that it filled a niche that no other high end monotube shock makers bothered to cover. These 4100 coilovers were different in that they were only around $2000 per set, had rebound-only adjustment, were built in Holland with exceptional fit/finish/quality, but had several race-worthy monotube features - like the large pistons and large adjustment range, normally only seen in $5000+ racing shocks. The ride and spring rate/damping rate was well beyond what you could achieve in a twin tube shock of similar cost, but cost less than half of the lowest cost monotubes from JRZ, Moton, Ohlins and Penske. The 4100 was a near race-worthy coilover shock at a twin tube price.

    Since the introduction in 2006, AST-USA sold thousands of 4100 sets, and to compete in that segment there have been similar models developed and sold in the past two years or so by JRZ, Penske and Ohlins (and those are typically costing closer to $3000 or more), with nothing close to 4100 sales volumes. I am sure they are great products also, but I feel that the 4150 beats them all on a combination of price, coverage, quality, and support.

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    When you make thousands of shocks using racing style damper technology at a unique price, sometimes a segment of your users are unaccustomed to race-shock repair intervals or other characteristics. Like when a monotube shock loses Nitrogen pressure it is very noticeable. Unlike in a low (or no) Nitrogen pressure twin tube, where almost no performance or ride difference is obvious. So keeping all of the gas seals intact in a monotube becomes a huge design point, and with a serviceable monotube there has to be a place to refill/discharge this pressure, which is the first place it can leak. So the 4150 has addressed that with double-sealed nitrogen refill connections. There were also some issues that cropped up when users took these $2000 shocks way beyond their performance envelope, using them for long periods in W2W racing with big grippy Hoosiers and/or aero loads. So now the 4150 strut now has a stronger internal top guide and a more secure top cap assembly retention method that does not require inspection. There are also updates to the bypass adjusters, stabilizer bracket improvements, lower drag seals, and the whole "upgradeability" feature (where these 4150 singles can become doubles (remotes or internal, depending on application) at a future time).

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    All of these updates have been tested in race and street cars and should make for a more robust race shock as well as a street shock with longer service intervals.

    Lighter is Better

    Another major change that actually lowered costs on "shock only" sets was replacing all steel-bodied 4100 shocks and the more expensive aluminum bodied 5100s with fully threaded aluminum body 4150s at a much lower price point than the 5100. The weight going from steel to aluminum shocks is cut nearly in half, and in any form of racing, weight is crucial. Here's a comparison of a BMW's steel body AST 4100 rear shock vs the new aluminum body 4150 version:

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    Cost & Availability?

    Right now Vorshlag has BMW E36 an Mustang S197 4150s in stock, and we have additional BMW E46 models inbound. The 4150 pricing is close to $2200 on most kits, which is about 15% higher than the old retail price on the outgoing 4100 models. This accounts for normal inflation as well as the additional materials and higher end components that go into the 4150.

    If you have additional questions, feel free to call us at 972-422-7170 or visit us at www.vorshlag.com. Vorshlag is an AST and Moton dealer, a testing and engineering partner with AST-USA, and we were the first AST dealer in the USA. We are also the first to get the 4150 models in stock. Vorshlag continues to have excellent customer service and the highest sales of the full catalog of AST models in North America. Our facility is located 100 feet from AST-USA/Moton-USA HQ, which gives us unprecedented access to the new designs, data, and the minds behind this shock brand.

    So far there are only a few car models that have the 4150 design produced, but more are coming soon. To fill that gap Vorshlag also has a few remaining clearance 4100 sets in stock for the following cars:

    • BMW E30, with custom built, powder coated, shortened 4-lug strut housings
    • Subaru GD STi, 2005-2007
    • BMW E36, E46 and E82/E90
    • AST 4200s for BMW E36
    • BMW E46 M3 4100 set - "pre-owned" shocks with springs, camber plates and AST spherical RSMs

    Note - this 4100 clearance inventory can change at any time and once these are sold they will be replaced with 4150s. You can see what is still available in the 4100 models here. And before you ask, the all new double-adjustable AST variant (4250) is still in development and we don't expect any news on this model until Q2-2013. The 4150 can be upgraded to a 4250, at some future date.

    Note to other AST and Moton dealers: Vorshlag is an AST and Moton dealer, competing with you for sales of these products. We ask for you to NOT steal our text, pictures and product entries. Don't just re-host our pictures and think that's OK, or take the pictures and block out our logo. If you want pictures of AST or Moton products, please either get them from AST/Moton or buy some shocks and take the pictures yourselves. Thank you.

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    If the AST 4150 sounds like what you need for street, competition, or a mixture of track and daily use - give us a call to inquire about a set. The BMW E36 AST 4150 product page is up, as is the S197 Mustang AST 4150 page. At this time, Vorshlag has the only AST 4150 coilover kits in the USA. We have the dampers, coilover springs, rear shock mounts and Vorshlag camber plates in stock for these models. We also have the first-hand racing and testing knowledge to help guide you to the proper spring rates and settings to help you win!


    Terry Fair @ Vorshlag
    Veteran Member
    Veteran Member

    03 Dec 2012 08:56 PM

    In this post I want to talk about some of the history behind one of the 4150 models we have in stock now, and the part we played in helping get them built the way they are.

    History of AST Dampers on the S197 Mustang

    The first iteration of AST coilovers that were tested on a 2006 Mustang GT back in 2008 are shown below. The S197 generation Mustang covers all models from 2005-2013. Vorshlag owns two S197 Mustangs and has worked on countless others. We know this chassis well and feel that the AST 4150 is the best shock option for the money, and provides the best combination of performance and ride quality in one package.

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    The four pictures above show the first set of 4200/4100 coilovers on AST-USA's first S197 test mule. We all learned a lot from this initial install, and went back and adjusted front strut lengths and learned that we needed to add a ride height adjuster and a different spring length out back. This set was tweaked a bit and works great, and is still being raced on this ESP classed '06 GT. We also tested the first iteration of the S197 Vorshlag camber/caster plate on this car, with two major changes made from what we learned.

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    On the next version of the 4100, shown in the next four pictures above, AST went with an inverted rear shock. This moved the rebound adjuster to the bottom of the shock instead of being in the trunk, but it also made for a bit less travel in the rear shock. With this set-up, we perfected the AST ride height adjuster and Vorshlag chassis adapter, and tweaked spring lengths to fit.

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    The third major round of changes are shown in the four pictures above. This was when Vorshlag took the above set of 4100s, went to AST-USA and found a new rear shock body/length/layout, and switched back to a "non-inverted" rear shock. This all new shock needed various adapter bushings to fit the chassis, but the non-inverted design made for easy access to the rebound knob once again and additional bump travel.

    AST Holland made the pre-production AST 4150 S197 shocks with an inverted rear shock, packaging it as a coilover only with the spring mounted to the rear shock. We did not order them this way, as it limits wheel room inboard, changes the motion ratio of the spring in roll, and applies full suspension/spring loads to the shock tower and upper shock mount. We feel that keeping the rear spring in the stock "divorced" location limits the loads to the shock tower (which was only ever designed to take damper loads, not suspension loading) and frees up room for bigger wheels out back. This is part of our solution to running an 18x12" rear in the back under unmodified stock fenders.

    Specific Changes to S197 Mustang AST 4150s

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    As we said above, Vorshlag has been playing with AST shocks on various S197 Mustangs since 2008, when we installed the first test set. We have worked with AST-USA to tweak the 4100/4200 shocks through several iterations of lengths, shock layout (inverted and non), and rear spring location (divorced and coilover). Now that the 4150 has arrived, Vorshlag asked AST to build them for us with a specific length rear shock in a non-inverted style. We use an AST ride height adjuster and our own chassis adapter. You can see our chassis adapter for the AST ride height platform being machined at Vorshlag, above.

    _DSC5978-S.jpg DSC_6519-S.jpg

    We keep the (replacement, coilover style, 2.25" inner diameter) rear spring in the stock location, use AST supplied adjustable rear spring height platforms, and machine our own Nylon adapters to make these platforms fit the S197 chassis. We're making these adapters in house and supplying them with each AST 4150 kit we sell at no additional cost. It is very unlikely you will see another AST dealer selling AST S197 shocks made to the Vorshlag spec.

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    Another extra step we take is providing new upper shock mount rubber, which would normally have to be cut/modified from the stock pieces. This way they come to you without needing modification and can just be bolted on the car with minimal fuss.

    That touches on the physical aspects that have changed from the first AST 4100 models made for the S197 Mustang to the latest AST 4150 version we sell here at Vorshlag. No other AST dealer customizes these coilovers to this extent, because no other dealer has the experience with AST's that we have here at Vorshlag.

    Thanks,Terry Fair @ Vorshlag
    Paul V
    New Member
    New Member

    17 Mar 2013 06:32 PM
    Any Idea when these will be available for the 2004 STi?
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