AST 4150 Monotube Coilover Struts and Shocks BMW E90 E92xi
The venerable 4000 Series damper stands as AST's entry level, adjustable damper. Using the same internal technology found in the 5000 Series competition sets, the 4000 Series creates near-budget level single adjustable and double adjustable dampers for the track and amateur road racing market.
- Monotube dampers that use 22mm shafts for struts and 14mm shafts for shocks
- Nitrogen charged to 175 psi for 22mm shaft shocks and 265 psi for 14mm shaft shocks
- Utilizes AST's Load Bearing Piston (LBP) for all strut designs (AST is the only coilover in this price range to use this feature)
- Steel bodied struts and shocks all use European KTL coating which is stronger and more weather resistant than powder coat or wet paint found on most shocks
- Utilizes design principles required for grueling TUV testing including withstanding 1 million cycles with 1100 pounds of side load on the strut
- Available as Rebound-only adjustable (4100)
- Fully rebuildable and revalvable
- Shortened appropriately for lowered performance cars
- The 4000 series have been tested at events including SCCA Nationals, NASA Nationals, 25 Hours of Thunderhill and Grand Am races
- Valved for a comfortable, agressive street ride that performs great at the track
- 2 Front AST 4100 Single Adjustable (12 adj, Rebound only) Monotube Struts designed specifically for the xi chassis only
- 2 Rear AST 4100 Single Adjustable (12 adj, Rebound only) Monotube Shocks
- AST Front Spring Perches for 60mm springs and your OEM upper strut mounts (removed when bought with camber plates)
- AST Tool Kit
AST coilovers are monotube, high pressure nitrogen shock absorbers. Why do you care? Most other products on the market are twin tube designs and are not pressurized, or only have 1-2 atmospheres of Nitrogen in a little bag inside. Monotube shocks offer the biggest pistons for more control. High Nitrogen gas pressurization in Monotubes (8-12 atmospheres) means the oil will never cavitate around the piston. This is particularly important in environments where the vehicle makes rapid changes in direction such as autocross and road racing. Monotubes also allow for a wider damping range and can more easily provide a better ride with stiffer spring rates - we usually start with 3X the stock rates and often go to 6-7X the stock spring rates, even on street driven cars. This is the same technology used on $7,000-10,000 shocks packaged here in a competitively priced kit.
Tuning Assistance and Installation
At Lang Racing Development we race all of our cars on AST suspension, that includes our BMW race cars, our Porsche rally cars, and our daily driven/weekend track vehicles. That means we know how to install your suspension right and how to suggest any other changes you might want to consider at the same time, get the most out of your AST suspension by having us professionally install it and get the initial settings configured.
We can also help you dial in your suspension with the easy to adjust AST dampers. We can also provide you with spring recommendations based on your car and particular application. As as Swift and Hyperoil spring distributor we can get your car set up with the perfect spring to match your AST dampers. Whether you are road racing, rally racing, or have a dual duty track day/daily driver, we can help you get the perfect setup. To get started tuning your AST suspension we suggest reading through the AST Tuning Guide.
AST-USA is setup to offer custom valving services to its customers, including dyno services on their Roehrig 2VS shock dyno; they can even rate your old springs if you are curious (fees apply). There's no need to find a third party company to get your custom valving applied - Just send them back to us and we will work with AST to get your shocks revalved to your exact specifications.
CAMBER PLATES : We highly recommend AST camber plates be used with AST strut kits, but the shocks can be used with the OEM upper strut mount for racers on an extreme budget and/or where class rules do not allow an upper camber plate (such as SCCA Stock Class). Easily adjust camber track side with camber/caster plates. Over-sized spherical bearings are designed to withstand the rigors of street and track abuse. All components are plated for maximum corrosion resistance and long life. Please see the product entries on this website for more information about the camber plates and perches. Ordering this option includes the associated upper spring perches made to work with these plates, 60mm springs and AST struts.
SPRING RATES : While AST-USA provides you with the shocks only, Lang Racing Develoment offers the unique option for racers to pick their own front and rear spring rates at a reduced cost. These options will included new Hyperco/Swift springs from our recommended packages, AST rear ride height adjusters, and nylon rear spring alignment platforms. The spring options listed include our GT package for daily driven cars, the GTS package for street cars that are also used in autocross and/or track events and the GTR package for race cars that predominantly see track use. If you would like to order custom rates not listed here, please give us a call.
All Hyperco springs are measured in inch lengths and rate is in pounds of force per inch of travel (lbs/in). To convert to metric length multiply inches x 25.4. To convert to Newtons/mm for rate you need to divide the lbs/in number by 5.7. To convert rate to Kg/cm divide the lbs/in rate by 57.
- 2 Front 60mm HYPERCO Coilover Springs, 178mm (7") Long
- 2 Rear 60mm SWIFT Coilover Springs, 228mm (9") Long
- AST E82/E9x 60mm Rear Ride Height Adjusters
- 2 Rubber Rear Spring Alignment Platforms