TEC Alloy Reservoir Shocks – Analysis Update

with 26 Comments
The TEC Piston on the left, the RFY Model 1 middle, and the RFY Model 2 right.
The TEC Piston on the left, the RFY Model 1 middle, and the RFY Model 2 right.

A while back I reviewed the TEC Alloy shock and spring package. Overall impression were good, though I never broke the shock down to inspect individual parts and pieces. Recently I got that chance.

The TEC rod and piston on the left, compared to the RFY setup on the right.
The TEC rod and piston on the left, compared to the RFY setup on the right.

Just as I mentioned in my previous article, these TEC Alloy Reservoir shocks are indeed very similar to an RFY. The similarities don’t stop at the outside either. Comparing the internals side by side, an untrained eye would struggle to tell the difference between the two makes. That said, differences do exist. Notably, the top out spring, or lack there of, is a rubber bumper on the TEC shock. Looking closely revealed that the TEC shock rod is a touch shorter than the RFY variant. This likely scales the rod to the shorter top out bumper. In contrast, the RFY needs a little longer shock rod to accommodate the taller top out spring. The TEC would also benefit from top out spring replacement, though not so dramatically as the RFY does. Additionally, preload reduction would also help riders who are lighter or have very light machines. The supplied coil spring is a little long even at maximum perch height and resultantly there is a fair amount of built in preload.

The TEC internals are decent looking components. The TEC shocks I tore down had some miles on them, but all parts looked clean and wear free. Again, it’s surprising just how similar these parts are to the RFYs, yet they are not identical. The pistons for example are interchangeable. That is to say, I could put RFY internals in the TEC shock body or visa versa. Yet, the RFY Model 1 Piston has 12 small holes radially in the piston whereas the TEC has 6 larger holes positioned radially. The TEC Alloy shock features shim stacks in various combinations top and bottom of the piston, again similar to the RFY. It’s impossible to make any conclusions on the difference in damping properties based on these observations. A shock dyno would be required to truly tell the difference. By hand however, I’d say the TEC is damped a little less than an RFY with the same shock oil.

Overall, it’s clear the the TEC Alloy comes assembled better than the RFY. There was significantly less air in the system than I would see in a new RFY, that said, the TEC Alloys certainly benefited from a proper rebuild. Even with moderate pressure in the canister the shock rod was slow to return to full extension. After my rebuild, the shock rod would return to full extension with about 45psi in the canister. My biggest complaint about the TEC Alloy is the substandard Schrader valve threading. Rather than using the a standard Schrader valve external thread, the TEC uses something else, and that means I can’t use the standard shock tool that works on every other set of shocks in the world.

Edit: March 26, 2015 (edited for my XS650 visitors)

Here is the most current spring rate graph I have regarding the TEC shock package. Based on some calculations, the TEC HD spring is likely about 20 lbs./inch stiffer than the standard spring that is shown in yellow below.

Spring Rate Graph
Spring Rate Graph

26 Responses

  1. Avatar
    Kevin
    | Reply

    So how did you set the pressure on the TEC shock? Could a guy replace the sub-standard valve with a regular one easily?
    Thanks for the post, your work is much appreciated. -Kevin

    • Chris
      Chris
      | Reply

      Hi Kevin,

      I used a small digital tire gauge. It certainly wasn’t the best, but it worked, sort of… Changing to a classic Schrader valve is certainly possible.

  2. Avatar
    Maciej
    | Reply

    Great work and report,

    I have the TECs (reservoir and adjustable damping) on a Triumph Bonneville. I find the standard spring rate too hard. Although I am 170lbs, the bike is converted into a brat bike and so the rear carries less weight ( I would suspect about 20 lbs less). With the preload set on minimum I get a max of 15mm sag… I would love to send my shocks for you to work on, however I am in Europe and quite far away. Expensive shipping. What spring would you recommend for the TECs. Is it possible to use the springs from the stock shock? Still got those. Thanks

    • Chris
      Chris
      | Reply

      Thanks!

      It sounds like that spring is definitely too stiff. One thing you can do is to reduce preload. Generally, there is a fair amount of preload built into the spring as a result of the dimensions of the shock. Doing this can be tricky, I do it successfully on a lot of the shocks I build, but it requires special tools and knowledge of the shocks etc.

      I don’t believe the stock springs will fit the TEC shocks, but since I can’t measure the two setups side by side I can’t be totally sure.

      • Avatar
        Maciej
        | Reply

        Thank you for your insight. Right now (according to TEC) I have a 18/25/33 kg progressive rate spring ( exact quote from TEC), there is a softer option of a 15/21/28 kg rated spring. I know that it is not that simple, but with simple math it should mean they will be about 15% softer. Is there a way to calculate this exactly in relation to rider sag? 15mm with harder spring will give me about …. with the softer one. Any idea?

        • Chris
          Chris
          | Reply

          Yes, you can calculate this directly. In fact, I have measured the two different TEC springs in real life. The factor that I have not considered is the amount of prelaod built into the spring as the shocks come from the factory.

          The spring rate estimator can be found here.

          The two available TEC springs can are already available on the calculator. I ran your number by hand and then redid them on my estimator and arrived at the same numebrs both times. I confirmed that you would gain around 3mm of sag by going to the softer spring. You will also gain a bit softer ride an use more of the available travel in general. This change shouldn’t be scoffed at, it is significant.

          Make sure you go and plug your numbers in yourself and see what you find. You will have to use imperial units, sorry about that. Perhaps I will make a metric form soon.

          • Avatar
            Maciej
            |

            Wow, you are the Man! Thanks again for helping me figure this out. I checked your calculator and used it to approximate the weight that my bike puts on the rear shocks (my current sag was the benchmark). I know that this will not be exactly accurate, but still it showed that with the softer spring I might go from 17mm sag to about 22 maybe 23. As you said it is not much, but even more than sag I am looking for a plusher ride. Right now when I sit on the bike and “pump” the rear shocks they go down and then stop firmly (a bit like bottoming out which they are not of course) instead of giving back some of the energy by a little push up.
            Thank you again for your time and knowledge. Wish It were easier to send you those shocks to work on 😉

          • Chris
            Chris
            |

            Good luck!

  3. Avatar
    Maciej
    | Reply

    I will let you know how it goes 😉

  4. Avatar
    john s
    | Reply

    hi chris, thanks for posting this. i’m going to try the tec shocks for my 72 honda cb350. hopefully they are decent shocks.

    • Chris
      Chris
      | Reply

      Good luck, John!

  5. Avatar
    Maciej
    | Reply

    Hi, Its me again…

    Any chance for a quick tip guide for a noob on how to change the springs on these Tec shocks?
    Much appreciated 🙂

    • Chris
      Chris
      | Reply

      You just need a spring compressor and some wrenches. It’s pretty straight forward.

    • Avatar
      Jonathan
      | Reply

      Hey Maciej,

      There is a step by step here: https://youtu.be/mQnx-ZbAD7o

      • Avatar
        Patrick
        | Reply

        Purchased a set of TEc shocks for 1979kz 1000 Ltd Do I need to put air pressure in and how much

        • Chris
          Chris
          | Reply

          Hi Pat,

          It is impossible for me to tell if you need to add bladder pressure. I do not have the shocks in my possession to measure the pressure.

          Generally, 125psi is a good start.

          Regards,
          CL

  6. Avatar
    Andre
    | Reply

    Hi, Chris! I have a pair of TEC in my Thruxton 2014, but they seem to have come with some problem. I can’t properly regulate them, and it seems they are leaking. I will not send them back, and I’ll try to fix them on my own. Do you have specs for them? Gas type, pressure, oil, etc? They are the model with adjustable damping. I have looked everywhere for these specs…

    • Chris
      Chris
      | Reply

      Hi Andre,

      I don’t have any manufacturer specs. From experience though, Nitrogen, 150psi, 7 weight or 10 weight. That will get you close.

      Regards,
      Chris

  7. Avatar
    Andre
    | Reply

    Thanks a lot, man!

  8. Avatar
    Oskar
    | Reply

    Hi,
    Thank you for a very interesting article! I just bought a pair of TEC shock with piggy back and was thinking about mounting them “upside down” with the reservoir downwards, if you see what I mean? Would this affect handling/performance in any way? The internet seems to give me different answers when I google.
    Thank you!

    • Chris
      Chris
      | Reply

      Hi Oskar,

      It increases the unsprung weight, as result that mounting is the less preferred method. That said, it was common for old Hammerhead shocks and other types to mount this way. It has no effect on the damper function at all, they can be oriented in any direction.

      Regards,
      Chris

  9. Avatar
    Oskar
    | Reply

    Hi Chris,
    Thank you for your reply! Since I drive an old Triumph Thruxton I don’t think the little gain in unsprung mass will effect it too much. Have to fit them upside down for sidemounting the licensplate.
    Oskar

  10. Avatar
    Darrell
    | Reply

    hello got a set in nz for my scrambler,had ….0 psi nitrogen in them lol! wondered why it was triing to buck me off.
    I had 80psi put into them,based on your earlier investigation,but do you think 150psi is more where i need to be?
    Any help appreciated.

    rgds,
    Darrell.
    Nelson NZ.

    • Chris
      Chris
      | Reply

      You can run 150 or even 200, but if they aren’t filled with oil they probably won’t perform great even then.

  11. Avatar
    Mario
    | Reply

    hi , how do i remove the bushing, up or down

    • Chris
      Chris
      | Reply

      Hi Mario,
      I’m honestly not sure how to help you.
      Regards,
      CL

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