New TEC Rear Shocks. Metal Inserts?

[Iflybikes]

Just received my suspension kit from Tecbikepartsusa. The rear OEM shock eyelets on the 2021-22 and supporting structure are much larger than the eyelets on the TEC parts and the OEM shocks have a MUCH larger METAL bushing than older Bonnies. (at least the ones I've been looking at on YouTube videos from Delboys and other posters). The TEC shocks have a lot smaller profile and have NO metal inserts at all. But TEC assures me that none are needed. Just the plastic bushings.I don't have enough experience to argue that but it seems to me that a metal insert should be there. I've included a photo of the two shocks side by side for a comparison. I can't imagine the plastic bushings alone being adequate for that purpose. Anybody have experience with a newer Bonnie using these shocks as recommended by TEC? I'm very skeptical.

Mike Matthews 2021-22 Red/Silver t120

 

[Iflybikes]

Photo did not upload. Don't know what I did wrong.

 

[Greyfell]

Photo did not upload. Don't know what I did wrong.

It could be the file size of the original image. Try downsizing a little, and trying to upload again.

 

[Iflybikes]

It could be the file size of the original image. Try downsizing a little, and trying to upload again.

Copy that, I’ll try it.

 

[Iflybikes]

Copy that, OEM on top TEC bottom. Fat metal insert, no metal insert at all. Hmmmm?

 

[Vector]

If they fit correctly I'd suggest they are fine as is.

 

[Iflybikes]

Well, thank you for that assurance. If someone has some actual, insight or experience, I think that would would be more on point and/or helpful.

 

[Greyfell]

Well, thank you for that assurance. If someone has some actual, insight or experience, I think that would would be more on point and/or helpful.

Vector has a lot of experience, but you are free to get a second opinion.

 

[sikatri]

It’s still a bushing just a different design. If the manufacturer has given you their assurance then I would take them at their word. If it fails they’ll back it up and it won’t go anywhere any more than the original design since a nut is holding it in place. It’s just a simpler design. Agree with Vector and Greyfell. I don’t have any experience with that product, but have turned a wrench for 45 years. I even got paid for it way back.

 

[Vector]

Well, thank you for that assurance. If someone has some actual, insight or experience, I think that would would be more on point and/or helpful.

Put em on and let us know how it worked out. I hope it gives you and better handling bike.

 

[sikatri]

Put em on and let us know how it worked out. I hope it gives you and better handling bike.

Agree. One of the other options is to return them for refund, but that really wouldn’t get you any better handling. I’d go with Vector’s advice, put them on and see how they ride.

 

[Iflybikes]

Well, I apologize for my sarcastic response. I’m extremely skeptical of a plastic bushing replacing what has been a product evolution covering many decades and that as I looked at and researched other shocks, not a single one, including earlier versions of this shock did not have a metal bushing as its primary wear surface. Not one. The existing removed shock eyelets seem to be at least a degree of magnitude(or two) more robust than the TEC shocks which have the plastic bushings of a much smaller diameter and inherent strength. My heart (and whatever engineering sense I may or may not have) just tells me they cannot hold up to the pounding of a 500 lb bike plus me and my wife and luggage. Do I trust them as I cross the lonesome highways in Wyoming? Etc. I’m a flight instructor(8000+ hrs)and do quite a bit of the work on my plane(s) and am familiar with wear surfaces and the appropriate materials required for long term and reliable(read safe) service. I’ve also been riding(without a single accident) for 60yrs. I am no neophyte.
OK, I’ll do the experiment. I’ll ride these for a 1000 miles and then see what wear has occurred. I’m very, very skeptical. If I’m wrong, I will certainly admit it. Actually, I hope I am.

 

[aj7840]

It never ceases to amaze me, that after several years of engineering studies at a major University an engineer selects a material for an application it is not designed for. Plastic bushings are designed rotatory motion. In this particular application there is minimal rotation with an impact load. The bushing now becomes an expendable/wear item with a replacement schedule, rather than just a spacer a steel bushing would be. Depending on the plastic chosen, it could be 1,000 miles or 10,000 miles. BMW does it too, I had to replace the front shock on a Telelever suspension because they did not supply replacement plastic bushings.

For reference I am a mechanical engineer who majored in material science. A common misapplication of plastic bushings is to subject them to impact loads. They do work in the application but do not have a long life, plastically deforming. Plastic deformation is a process in which enough stress is placed on metal or plastic to cause the object to change its size or shape in a way that is not reversible. It just happens at lower loads with plastics compared to steel or brass.

 

[ManInTheJar]

The bushing now becomes an expendable/wear item with a replacement schedule, rather than just a spacer a steel bushing would be. Depending on the plastic chosen, it could be 1,000 miles or 10,000 miles. BMW does it too, I had to replace the front shock on a Telelever suspension because they did not supply replacement plastic bushings.

Before fitting them it might be worth asking TEC a couple of supplementary questions along the lines of: Is there a defined service life fir the plastic bushes? and Are the bushes available as service items?

 

[sikatri]

As ManInTheJar suggested ask a few more questions. If the responses are not to your liking ask for a refund and keep the originals. I understand your hesitation and acknowledge that new designs don’t always measure up to originals. Knowing what is the expected wear life should help you decide if it’s worth the trade or not. The manufacturer has stated its position and claims to stand by their product. Now if the expected use is significantly less than what you would expect with the original it might not be worth it to you. I didn’t ask before, but why were you replacing the originals?

 

[sikatri]

As a side note it baffles me the material choices by some engineers. I’ve gone through five intake manifolds, plastic, on my 1996 Ford Thunderbird. If there was a direct swap aluminum one I would have bought it long time ago. It was a design choice undoubtedly based on cost, not longevity. So I do understand the opening posters concern. My Triumph seems to have whatever type OEM suspension on it and it’s a 2005. I don’t know if they are original or replaced, but I’m not making any plans to change them. They appear to be durable and good quality to satisfy my needs. Material changes are not always based on longevity, many times material changes in modern vehicles are by design meant to wear out. I had never heard of single torque bolts when I first started wrenching, now many manufacturers use them. I suppose they have some reasoning, weight perhaps or whatever. All I know is, some things have a limited life use. I don’t replace something without a good reason. Like the OP, if possible with something better and longer lasting. I’ll tackle that car manifold one more time, when I do it will be aluminum. Why now and not before, emissions testing. Now it’s 25 years old and here I can mod it without worrying that it won’t pass inspection. There is no emissions testing in Texas for cars older than 25, so I could change the top parts without worry. Hope you get the answers you want from the manufacturer, if not, stick with the OEM. Good luck if you decide to test them for a bit.

 

[Gear1]

11000 miles so far with TecBikeParts shocks with plastic bushings. The bike is a 2018, but the principal is the same. I just grease the bushings before assembly to prevent fretting. I also use Plastic bushings in my BMW suspension for better handling; far greater loads imposed than the motorcycle. Very pleased with TecBikeParts.
Craig

 

[Iflybikes]

11000 miles so far with TecBikeParts shocks with plastic bushings. The bike is a 2018, but the principal is the same. I just grease the bushings before assembly to prevent fretting. I also use Plastic bushings in my BMW suspension for better handling; far greater loads imposed than the motorcycle. Very pleased with TecBikeParts.
Craig

Thanks Craig, This is what I was looking for. Someone with actual experience with the shocks. In my gut I just have my doubts about the use of plastic when it can't be that much more money(pennies) to use stronger materials(read metal). But you have the miles to back up the design and it will take me a while to run 11,000 miles on this bike so I'm feeling relieved that my worries are likely just from my own lack of experience. I did grease the bearings and install the all important washers as instructed. I took the bike out for a ride, but just around the block and am planning on putting in the front springs from TEC in tomorrow and if time allows (I work slow with a lot of double checking take her for a longer ride.

 

[Iflybikes]

Before fitting them it might be worth asking TEC a couple of supplementary questions along the lines of: Is there a defined service life fir the plastic bushes? and Are the bushes available as service items?

Good point!!

 

[Iflybikes]

Good point!!

I was told that I am uninformed about the shocks and the inserts: that the metal inserts will eventually seize to the mounting posts and the plastic surrounding will be wearing on metal anyway. So I guess the metal inserts on ALL of the other shock designs are just superfluous or will be rendered that way when they eventually seize due to poor maintenance and a lack of periodic lubrication? Let’s just skip a step and get the process going earlier?