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I'm in exactly the same spot. Major motivation for the Kepspeed is my loathing of the stock chain adjusters, and the fact that bronze bearings + better chain adjusters would cost more than the Kepseed, which improves both and then some. I originally planned to go with the lightest Kepseed, but after seeing a competing aluminum swinger (probably a Spyker?) with a catastrophically cracked weld, I'm leaning toward the under-braced version to distribute load a little better. Looks are of the least concern to me, weight reduction would be nice but not a priority.
I found no reported failures for the Kepspeeed swingarm

Here is the thread about the failed takegawa weld:




86908



Here is the spyker failure:


86909
 

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I have the Kepspeed and plan to replace it with another one if the swingarm bearings go bad. Not sure how I would even notice they were going bad though. The pivot bolt is supported by a bushing for 50% of the bolt travel through the swingarm on both sides. The bearings are only on the outside portion of each arm. I doubt I could tell the difference if the bearings seized up. They would just act like bushings at that point.

If you are really worried about the quality of the welds, take the swingarm to a reputable welder to get it inspected before an installation. I may do that to put my mind at ease. I do inspect the welds every time I lube the chain. A failure would lead to a crash no doubt. Those welds need to take a massive load, and I am not qualified to determine if they are sufficient. No way to see what is going on inside the structure either.

The stock swingarm is so much heavier than the Kepspeed, it does make you wonder if the engineers who designed it knew something we don't. It is an engineered piece, maybe that level of robustness is critical.

MNNTHBX bushings and OTB adjusters are probably the smart choice, but I went with passion for the Kepspeed. Probably not that smart.
Are you saying the pivot bolt is supported by bushings where it passes through the frame?

If so, I would imagine that the pivot bolt generally stays stationary and the swingarm rotates on the lower resistance needle bearings only. I agree, it might not be obvious when those bearing do go bad. If the shock was removed and you cycled the suspension by hand, then you would likely know for sure.

I’ve owned seven Cannondale Lefty mountain bike forks and countless Cannondale Headshocks. The older versions were sealed with a rubber boot. If water got past the boot, over time, it would keep cycling through the “88” needle bearings, as the fork compressed and rebounded, until the grease broke down, then the fork could get pretty locked up.

Yeah, Honda’s engineers know what they are doing, but lots of motorcycles use aluminum for swing arms and frames I believe, so it can be done safely.

In the bicycle world, I’ve seen people ride aluminum frames with small cracks in welds for thousands of miles. Not advisable, but it didn’t fail catastrophically. It could have though. I’ve seen a steel frame fail catastrophically
and carbon fiber too.

Whether the a Kepspeed is heavy duty enough for the demands of a Grom, plus rider and potential passenger, I’m not sure. A lot of it depends on the owner/rider. Bigger, heavier guys are better off riding stronger stuff. Period. It’s just physics.

All materials have their limitations. Manufacturers can’t control how the end user will misuse/abuse a product either. They usually try to design in a safety margin, but some people seem to think that there are no limitations to how much abuse a product can take.

I’m torn whether to just skip it and get the MNNTHBX bushings instead.
 

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I found no reported failures for the Kepspeeed swingarm

Here is the thread about the failed takegawa weld:




View attachment 86908


Here is the spyker failure:


View attachment 86909
Yep, that is the Takegawa failure I saw on here.

That Spyker failure is terrifying. That could have ended badly.

Aluminum can be welded safely. I’ve ridden lightweight aluminum bicycles since 1988. I’ve never broken an aluminum frame. I have had a carbon fiber frame and crank, both develop what looked like hairline cracks. The manufacturer replaced them in both cases.

From what I understand, Cannondale used kind of a hybrid mig/tig weld process, to weld their AL6061 frames. The welds were then ground down smooth to reduce stress risers where the smooth aluminum tube, met the jagged weld. That is where it usually breaks.

The bicycle frame was then heat treated to realign the grain structure of the metal where it was weakened from the weld process. I believe this extra step is an expensive process and requires expertise to get it right.

Most smaller manufacturers would weld their frames from AL7075, which was pretty strong even after welding and then skip the heat treatment process. Most of them had no ability to heat treat their frames. I was told that heat treated AL6061 was stronger than non heat treated AL7075 after welding.
 

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Are you saying the pivot bolt is supported by bushings where it passes through the frame?

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The Kepspeed swingarm has needle bearing towards the outside of each side, and bushings on the inside of each arm. The weight of the bike through the pivot bolt likely rides on both the bearing inner ring and the portion of the arm attachment which is bushing. The bearing may not take the full load as it does on a set of wheel bearings. Not sure why it was designed this way.

Here is a pic from this thread:



86913
 

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Well, interesting. Are you sure the bushing portion is definitely making contact with the pivot bolt?

I appreciate the photos and additional information you have provided about the Kepspeed swingarm.
 

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Watch the below video about needle bearings in a big bike swingarm.

That design has full length bearings with bushings, thrust bearings, and seals.

I am trying to wrap my brain around how it works with the kepspeed arm. The pivot bolt once compressed is pushing against the edge of the needle bearing without any thrust washer between, or bushing spacers isolating the bearing. What is actually moving against what?



 

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Watch the below video about needle bearings in a big bike swingarm.

That design has full length bearings with bushings, thrust bearings, and seals.

I am trying to wrap my brain around how it works with the kepspeed arm. The pivot bolt once compressed is pushing against the edge of the needle bearing without any thrust washer between, or bushing spacers isolating the bearing. What is actually moving against what?
Yeah, I’m not sure what is going on either. Without thrust bearings and spacers, it looks like the needle bearings would be getting side loaded or compressed, binding things up. I guess I really need to see one in person.

Does the Kepspeed seem to move freely once it is tightened up?

Phoenix, I looked up those NDC chain adjusters. I’ve never seen those before. They look nice. Any idea how they compare to the OTB adjusters?
 

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Phoenix, I looked up those NDC chain adjusters. I’ve never seen those before. They look nice. Any idea how they compare to the OTB adjusters?
I’m not sure how they compare to be honest. I just went with the NDC because they were cheaper haha. I like them a lot though. Huge improvement over the stock BS.
 

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Yeah, I’m not sure what is going on either. Without thrust bearings and spacers, it looks like the needle bearings would be getting side loaded or compressed, binding things up. I guess I really need to see one in person.

Does the Kepspeed seem to move freely once it is tightened up?

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Yes, the swingarm moves freely when tightened up in place, but I cannot figure out what in the swingarm passthrough is rotating. The bolt and outside washers are of course stationary, and the swingarm moves easily.
 

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Now, according to their home page, MotorKit has disabled their shopping cart and stopped accepting new orders. I guess they have a bunch of orders piled up they need to work through first.

So it might be a while before that is re-enabled and they start shipping to the United States again. It will give me more time to decide if I want one or not.

MNNTHBX bushings and those NDC chain adjusters would make for a nice, strong setup.
 

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I had a set of the NDC chain adjusters, I'm not a fan of them at all. The design of them is not ideal, c-clip that retains the adjustment bolt will eventually get mangled and just not end up working. The OTB chain adjuster is a much better design, so I'd recommend spending a bit more and going with them.
 

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I had a set of the NDC chain adjusters, I'm not a fan of them at all. The design of them is not ideal, c-clip that retains the adjustment bolt will eventually get mangled and just not end up working. The OTB chain adjuster is a much better design, so I'd recommend spending a bit more and going with them.
Haven't had an issue with mine yet BUT I haven't had to make a lot of adjustments either. I guess time will tell. To be fair I was on a tight budget at the time I bought the NDC's and I hated the stock adjusters. If it had been today I would've went with the OTB's.
 

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Good to know about the chain adjusters. Looks like MotorKit is accepting orders again, but still not shipping to the United States.

I noticed that the chain slider/protector is pretty small on the Kepspeed swingarm. I realize keeping your chain adjusted properly is key, but are any of you concerned about the chain slapping the underside of the swingarm? Has it happened to anyone? Too bad they weren’t a little more generous with the size of the slider. It probably couldn’t hurt to have a little more protection I guess.
 

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Well Gromers, I guess I’ve now joined the Kepspeed club too. MotorKit started shipping to the United States again. I ordered a silver swingarm, unbraced, standard length.

We’ll see how I like it. I can always sell it if I don’t like it. I’m pretty sure it will be great though. They look really nice in the photos.

It was 111.57 Euros after the VAT taxes were removed, then shipping was 28.91 Euros, for a total of 140.48 Euros.

That is about $152.94 USD. Not sure if my bank will gouge me with a foreign transaction fee. I’m sure they will, because why not? Right?

My biggest concern with the Kepspeed swingarm is the tiny chain slider, like I mentioned previously. Hopefully with proper chain adjustment, it won’t be an issue.
 

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Yeah, I’m not sure what is going on either. Without thrust bearings and spacers, it looks like the needle bearings would be getting side loaded or compressed, binding things up. I guess I really need to see one in person.

Does the Kepspeed seem to move freely once it is tightened up?

Phoenix, I looked up those NDC chain adjusters. I’ve never seen those before. They look nice. Any idea how they compare to the OTB adjusters?
There are reducing spacer sleeves placed inside the needle bearing to hold the swingarm bolt. These sleeves stick out just enough to brace against the frame and existing washer giving enough slack for the swingwarm move freely on the sleeve/bearing combo.
 

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Lots of good information here, I think this thread has become the most comprehensive resource on the Kepspeed available. I'm again tempted to place an order, I don't ride hard or race, and I am a lightweight rider, but I do always wear full gear, often commute with a backpack, and occasionally hop a curb or hit a pothole.

The end piece of the Kepspeed seems to be welded to the arm with an end-to-end joint, where most factory aluminum swingarms I see are a small piece sleeved into a larger channel and then welded at the seam, in which case most of the load is not transferred through the weld. It looks like they tried something like this on the failed Spyker in the pics above, but the inserted length was too shallow to make any difference, and the weld was too superficial to make a strong connection with the insert.

I have seen other forums claim that the Kepspeed is a "direct copy" of the Takegawa, which is untrue; The unbraced Takegawa has a weld that runs at an angle, which makes it unlikely to shear in the case of a sharp impact, the weld on the Kepspeed, G-Craft, Spyker, and others is vertical, making them much more susceptible to damage in a sharp impact such as a bottom-out.

The under-braced Takegawa is braced behind the weld (under the end piece), the braced Kepspeed has its brace welded to the main body of the arm, leaving the axle mount attached only by the vertical weld. With the Takegawa, there is a near-zero chance of catastrophic failure - it's still possible to crack a weld, but the under-brace would keep the parts from separating.

The ability of the Kepspeed weld to carry the weight on the day-to-day is not in question, but how it holds up in a worst case scenario, like an unexpected pavement buckle at 50+mph, is more my concern. I'm still considering it, might reach out to Kepspeed directly for a little more information on the construction.
 

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I wonder if the Kepspeed has anything sleeved and inserted into the arm at the axle piece?

Aluminum bicycle frames are often just mitered tubes that are tig welded together with nothing inserted. I realize that we are talking about different amounts of stress, but I’ve seen plenty of big guys doing 10 to 12 foot drops on aluminum bicycles. The stress has to be pretty large. It is impressive when you consider how lightweight some bicycle frames are.

You make good points though. It would be interesting to see if Kepspeed could provide more information. I think the quality of the weld plays a big role here.

Whenever I see something broken, I have to wonder how the person was using the product. Sometimes stuff just fails, when it shouldn’t. I’ve had $1000 cranksets fail. Twice. My cycling weight has fluctuated been between about 138-158 pounds over decades of cycling.

In the bicycle world, cycling shops joke about all of the stories that begin with JRA (Just Riding Along). “I was just riding along when (fill in the blank) happened out of nowhere”. Often times you later learn that the person was abusing the crap out of the product, exceeding its design limits.

When I see YouTube videos of how some guys abuse these Groms, I shake my head in disbelief. I’m surprised they can take as much abuse as they do.
 
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