Product Test: Progressive 412 Series Shock Absorbers

Most people I’ve spoken to are happy with their Progressive Suspension products. If you went by damping action alone I would be, too. The problem I had with the two sets of Progressive 412 shocks I’ve bought is that the damn things leak. When I say leak I mean like after a couple thousand miles of off road riding. Conversely, some of my riding buddies have the same exact shocks and report no leakage after several years.

Godzilla, my 1971 Yamaha RT-1B 360cc endure, has about 4 inches of rear wheel travel. When new, the Progressive shocks did a fantastic job damping that short distance. The bike would bottom out if you hit big ruts at speed but the rear end stayed in line and didn’t swap places with the front. It was a great boost to my confidence. I was able to gain some serious speed across open desert while the Progressives swallowed up big holes and bumps without spitting me off. I’m not saying it was a smooth ride, but it was controlled.

The shocks were great on hills. They helped the rear knobby tire follow the contours of the earth and allowed Godzilla to climb some really steep inclines. If I accidentally spun the wheel by feeding in too much power I could close the throttle and then bog the motor, taking advantage of the big two-stroke Yamaha’s grunt at low RPM without stalling the engine. It was a traction seeking beast, I tell you. I’ve replaced the 412’s with a cheap set of remote reservoir shocks and the difference in performance is huge.

The first set of Progressives lasted about 10,000 miles before one of them sprung a leak. I chalked it up to the rough trails Hunter leads me on. Since I liked the Progressive action so much I sucked it up and bought another set. The new set was just as good, except they started leaking after only 2,000 miles. The second set of Progressives failed dramatically: Both shocks went bad simultaneously and projectile vomited hydraulic oil all over the rear of the bike. I thought the engine crankcase had broken.

To give the shocks their due I was riding an extremely rough trail with lots of boulders and steep drop offs. The rear suspension was bottoming on the big stuff but I felt conditions were no worse than normal.

The leaking wouldn’t be a big deal if the shocks were rebuildable. Progressive 412 shocks are not. They roll the shock body over the upper shaft guide and seal. It’s a machine process that is difficult to replicate in the average home shop. Even if you did manage to un-roll the shock body, the seals are made by NOK and are proprietary to Progressive (and Progressive won’t sell the seal). The shocks are made in Mexico so I doubt they have any to sell. In my correspondence with Progressive the only solution offered was to buy yet another set of shocks.

At $250 a pair this was getting expensive, you know? Since I had so many leaking Progressive shocks I decided to cut one open to see if there was any way to modify the seal area to take a seal that is available. It looks doable. I will need to get my South Bend lathe up and running to spin out a new top bushing with an O-ring on the outer part to replace the crimped end. To keep the top bushing from popping out on full extension I’ll need a few screws around the circumference of the shock body. Any nitrogen charging will have to be replaced with air from a simple Schrader fitting.

I’ll do another blog on the seal/bushing refit but don’t hold your breath. None of this is going to happen in time for October’s Yamaha Enduro Fest held in Flagstaff this year. The remote reservoir shocks are so bad I’ve got a cheap set of Red Line shocks coming from Ebay to tide me over. For those of you keeping count, I’ve had the original shocks, two sets of Progressives, the remotes and now the Red Lines. Hopefully these last two won’t leak.

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