TEC Alloy Reservoir Shocks – Analysis

with 11 Comments
TEC-Alloy Shock with reservoir.
TEC-Alloy Shock with reservoir.

This past week I got my hands on a set of TEC Alloy Reservoir shocks. User SaltCityCafe from the DoTheTon.com forum sent me a pair and in the name of science I gave them look over.

For this analysis I first wanted to compare the shock to the RFY unit. Since both shocks are inexpensive designs with very similar appearances comparing the two seemed natural. For this analysis I wanted to measure the spring rate of the coils that come on the TEC dampers. Secondly, I wanted to qualitatively check the damper for air as well as the the effectiveness of the reservoir. I decided before hand that since the dampers were brand new that I wouldn’t take them completely apart if I didn’t find any glaring issues.

First I removed the spring from the damper and got setup to measure the spring rate. To measure spring rate I use a Longacre racing scale to measure the force on the spring. I place the spring and scale inside a hydraulic press as to depress the spring. I measure the distance that the spring is depressed with a 2 inch dial indicator. I record the weight registered on the scale every .25 of an inch. The spring rate worked out to be 125lbs/inch and is one of the stiffer springs I’ve encountered. This however could be a result of the Honda CB model requiring stiffer springs. See the graph on the right for comparisons, the TEC spring is denoted by the yellow line.

Once the spring was off I was able to look the damper over closely. The damper body itself appears very similar to the RFY. In fact, the preload collars and threaded body may be the same. I did not measure to verify, but the TEC and RFY appear identical in this respect. The eyelet, body cap, and reservoir on the TEC however are different from that of the RFY. The castings are visually different and the machine work on the reservoir is a slight departure from the RFY. Overall quality appears to be pretty good for a budget unit and the fit and finish is fair to good.

Spring rates of assorted motorcycle springs.
Spring rates of assorted motorcycle springs.

While checking the reservoir it seems that Schrader Valve appeared to be metric. This meant that my shock charging tool would not screw onto the valve stem. As a result I had to resort to other options for checking the charge on the damper. Luckily I had a small but high precision tire gauge on hand to check the pressure. It’s important to note that the volume of a shock reservoir is so small that using a tire gauge will result poor measurement. Initial measurements gave me around 40psi for both shocks. Again, I can’t stress enough that even with this precision tire gauge that measurement is not particularly accurate with this method.

Next I manually worked the shock rod through its travel. I did this by hand and did so as to simulate both heave and rebound events. This method is effective at identifying air space within the shock. You can physically feel the shock plunge without much resistance when air space is encountered. I was able to identify minor air space inside the shock. The air space was minor enough that a rebuild was not immediately necessary. For comparison, I have had used RFY shocks come through my work shop with a full inch of plunge. The TEC had less than .125 of an inch in my best estimation. Ideally the shock would be purged completely, but given the low amount of plunge it’s likely to be unnoticeable during a ride.

The final test was to check shaft return. When the shock rod is forced into the damper body oil is displaced into the reservoir equal to the volume of the shock rod. The bladder allows this to happen by collapsing. The greater the pressure inside the bladder the more resistance there is to the compression of the shock rod into the shock body. My initial tests revealed that the approximate 40Psi. reservoir pressure wasn’t enough to return the shaft to full extension. I increased bladder pressure to 80Psi. and immediately the shock shaft returned to full extension on it’s own. This shows that the reservoir system was working effectively.

Unfortunately during this analysis I never opened the damper itself. Doing so would have given me access to the piston and shim stack. Without this information I still have some questions. This in mind, the assembly of this shock is better than the RFY model. I emphasize assembly, as the outward appearance differs, I’m not too sure that they aren’t the same internally. While the construction is a slight departure from the RFY, the final effect is much the same. You pay a slight premium to get better final assembly than that of the RFY. Asides from this, the major advantage of the TEC Alloy shock is that they advertise for Honda CB model bikes. This likely means that they have appropriate spring rates and proper eyelets and clevises for those bikes, though I do not have access to a CB to verify. If you have a CB, these might be a good package. Finally, the damper does appear to be fully rebuildable, meaning that if the rider should require different damping properties its plausible to do so. This analysis was done off the bike. Final conclusions should be made via testing in the real world on a real bike.

There is an update to this top that can be found here.

11 Responses

  1. Kevin
    | Reply

    Chris, I’ve read your shock reviews about 5 times each, and I really appreciate your detective work. I have a set of TEC shocks showing up tomorrow and I’m putting them on an 82 GS1100E. TEC Bike USA suggested optional HD springs for an extra $19 and I ordered them with the set. They didn’t really answer the other 9 questions I had for them, so we’ll see when they show up. If you ever have a chance to tear down a set of these, I’d love to hear more. I have a feeling I’ll be opening mine up and checking at least the oil at some point. Hopefully I can find a local shop that can charge the Metric valve with Nitrogen. Thanks, Kevin

    • Chris
      Chris
      | Reply

      Hi Kevin,

      Lot’s of people report lax customer service from TEC USA. It seems they don’t have enough margin in their products to pay someone to do that.

      Good luck with your shocks though, I think they have potential. If you can, please report back with your experiences. I am working on a database to help people better chose when they look for budget shocks and your information would be greatly appreciated.

      Regards,
      Chris

  2. Kevin
    | Reply

    Chris,
    I got the shocks, did a little investigating, swapped the springs, and went for a test ride. My findings were pretty much identical to yours. I posted a review with pics on a forum:
    http://www.thegsresources.com/_forum/showpost.php?p=2023179&postcount=29

    I have to say that I’m probably going to just leave them installed and ride them. Even if they’re not perfectly set up, they’re doing 99% of the job I need them for, and unless they fail or start leaking, I probably won’t crack them open.

    $139 shocks + $19 HD springs + $19 shipping = $177 totally happy.

    -Kevin

    • Chris
      Chris
      | Reply

      Sounds, great Kevin. Your feed back is very similar to a lot of guys I talk to, the same goes for the rebuilt RFYs as well.

      If you get a chance, can you measure the wire diameter on both sets, the outside spring diameter, and give me a count on the number of coils. I just want to compare the HD to non-HD sets.

      Thanks for commenting,
      Chris

  3. Kevin
    | Reply

    7.75mm on both sets. Same free length. 11 coils on the stock springs, 10 on the “HD” set. My highly scientific method of pushing on them with my palms on the floor resulted in no appreciable difference in rate.

    I’ve used a ruler and a bath scale to measure fork spring rates, but I’m not sure how I can “shade tree” measure these…. Hummm. Maybe under the hitch of my truck with a jack and the same bath scale?

    Let me see if I can do this…

    -Kevin

    • Chris
      Chris
      | Reply

      I measured the rate directly in my shop on the non-HD model. I will just extrapolate the rate of the HD version using the appropriate math. I just need the outside diameter to get it right. Using guestimated number I extrapolate 140lbs/inch for the HD model.

      • Kevin
        | Reply

        Sorry I forgot that measurement. Whole spring OD 60mm (2-3/8ths).

        I performed a shade tree spring rate test, I think your math is probably more accurate than my test. If you check out my picture, you’ll see why I only measured whole inch increments.
        Here’s what I got:
        STK springs: 1″ = 122 lbs. 2″ = 247 lbs.
        HD springs: 1″ = 142 lbs. 2″ = 269 lbs.

        My scale sucks for this kind of measurements. It’s digital and locks on the weight if it doesn’t change.

        BTW, both springs are 8″ long free length.

        -Kevin

        Redneck Spring Rate Measurement:
        https://lh4.googleusercontent.com/-YGlTEt7Gf6Y/UzCTYU0ObLI/AAAAAAAAyfY/ffMkNDjxSpg/s912/20140324_094544.jpg

        • Chris
          Chris
          | Reply

          Wow! Great work, Kevin!

          Your information aligns exactly with my math. Thanks so much for your work!

          • Kevin
            |

            Please.

            Just happy to contribute a tiny bit to your outstanding knowledge base.

            I’m going to set my sag, add about 1″ of ride height, and do some test miles.

            Kevin in Portland, OR

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