Rebuilds are crazy expensive. My 5100s are due for a refresh and last I talked to Vorshlag they said they can do a normal rebuild in a few days but if I need any other parts it could be a long time as they were having a hard time getting parts after AST-USA went away. The best auto-x of our season is in a few weeks and then they're getting rebuilt.

In other news a local auto-x guy just bought some FA 510s for his STi so I'm looking forward to his thoughts on the CFD with his 10k springs.

 

The 510 seems legit and rebuilds are relatively cheap. I just couldn't budget for them at this time.

 

anyone with FA wants a cheap set of FA500 shock bodies as spares, i have a set for sale

https://www.evolutionm.net/forums/sa...-1k-miles.html

 

I'm running a older set of 4100s with the steel body. I am running 11k/12k spring rates on the stock valving and helper springs. I'm happy with them so far and don't have many complaints beside the adjustable for the ride height.

 

Just to add some more fuel to the fire, my take on the AST models in general, and for EVOs specifically.

The 4100 had some teething issues on some models, but not for the EVO which was built to the right lengths from the start. The consumable parts are all generic, so they can be rebuilt without having to deal with AST, and often better quality than stock parts can be used. The pistons can be upgraded to double-digressive, which allows some very high slow speed compression forces, but a hard knee point to allow more compliance over curbs on the track or potholes on the road.

The 4150 fixed all the sins of the 4100 for other models, but stepped up the bar for entry level on the EVO. Better top guides for longer rebuild intervals, standard with double-digressive pistons and a slightly better adjuster raised the price a little, but added more performance. Rebuilds are still easy, but other than a revalve there aren't many upgrades.

The 5100 is the heavy duty inverted. These are one of the best bang for the buck if you can find a set. The rebount adjuster is on the bottom, which is inconvenient, but these can take a huge hit, run on the widest slicks, or even entry level rally without failure. Rebuilds are still easy. These can be upgraded with the double-digressive pistons.

The 5200 is as strong as the 5100 and was made in two different versions. The standard version has the hose for the compression canister remote exiting through the top of the pin. It has to be disassembled to install a top mount, which is a pain. Rebuilds are easy, but you have to send your camber plates with them and should have the plates rebuilt at the same time. The other version was made for World Challenge cars and the hose exits below the top mount on the side of the shaft. Springs and top mounts can be swapped easier, but you lose some stack height. Easy rebuilds.

 

^^^

i just got the basic 4100. my "race car" plan are on hold, so i don't need anything too crazy at the moment. these have one adjustment, so the learning curve isn't too steep LOL. so far, so good.

would you mind sharing info on rebuild parts? personally, i've never rebuilt a set and wouldn't know how.. but if i can buy the parts and send them to a builder...

how in the heck to people add the nitrogen after a rebuild???

 

The 510s look real interesting, especially the price for doubles. From my limited research ive heard they look good on a shock dyno but the forces are slow to respond to speed changes. Would love to hear from more that have used them as this year I could really feel the need for separate compression and rebound.

 

That's what I was thinking when deciding between the two.
I don't know that they will perform like the more popular options...But I'm hopeful.