S18 Suspension Overhaul

[Feynman]

If anyone else is thinking custom bushings, I measured the depth of the bearing pockets.  See pic for reference.  FYI - the depth wasn't consistent for any pocket so these are the minimum values I measured.  I took 5 samples per pocket.   I'm going to measure the other two arms now just to see if they're consistent.  If not, I'll post those measurements here as well...

A.) 10.2mm (0.405")

B.) 7.9mm (0.311")

C.) 10.0mm (0.395")

D.) 9.8mm (0.385")

 

I know this will come as a shock to everyone, but the depth of the pockets in the other side arms aren't quite the same.  Again, these are the minimum measurements.  The holes weren't drilled quite perpendicular (I think), so the measurements vary at different spots around the pocket.  Obviously, if you want a flush or slightly sunken fit, I'd measure your pockets, because I guarantee you they won't be the same as mine

 

A. 9.1mm (0.360")

B. 7.3mm (0.286")

C. 9.1mm (0.357")

D. 9.8mm (0.386")

Edited August 28, 2020 by Feynman
Other arms

[FinRider]

I have been pondering the setup of the positive vs negative chambers. I am not convinced the KS method with using the block is the right way, so I spent some time today watching and reading how the mountain bike guys do this as they have had many years of experience with rear shocks like the one used on the KS18. This is the advice that I saw frequently referred to:

Set your sag with the main chamber, and then adjust your negative until you get the feel that you want. 
they also recommend to set up the sag to 25% of the total travel of the shock. Our shock appears to have a 50mm stroke, so if we follow the same analogy, then the correct sag should be 12,5mm.

in other words, one should add positive pressure until the desired sag is achieved, then start to add negative chamber pressure until the suspension feels comfortable for the desired purpose (road, off-road, trails, jumps, etc).

I’m gonna go play around with it now... I just need to buy another shock pump and elbows for the valves so I can monitor the pressures during the setup& sag tests...

[Zwheeler]

How I fixed my S18

I'd like to show how I fixed the suspension problems on my S18. After the initial planning, the work itself took less than an hour. The parts did cost less than 20€.

 

But, please remember that this was only my wheel - yours may be different

My S18 had quite stiff suspension, and the problem seemed to be in two places:

• The suspension tubes were practically stuck, and
• The central pivot was assembled in a wrong way, making lots of friction to the suspension system

 

Part 1 was easy to fix: just remove the blocks under the pedal hanger, as described elsewhere. Then just lube the tubes with suitable oil. That fixed it.

Part 2 was a bit harder. There were two main problems:

• The central pivot was immobilised by adding a 10x19(?) washer under this screw. It scrapes against metal and creates lots of friction.
• The pivot arms (or whatever they are called) were scraping to each other - metal to metal. Friction here also
• There was also a bearing missing on the left hand side

 

First I removed opened the bolt that keeps the lower end of the shock in place.  That gives you some room and makes the assembly easier.

 

 

You can also see the 10x19 washer under the bolt. That keeps the suspension securely fastened The solution is just to remove this washer. You don't need it

 

Next, I opened the bolt at the  central pivot. The rest of the  suspension seemed to work just OK. There was very little friction while moving the arms. So, I did not bother to open the suspension system any more. Your situation may be different, however

 

 

While opening the central pivot I noticed that there was a bearing missing. Luckily only one. The rest seemed to be in place

 

 

I had visited a RC- car shop and bought a 10x19x5mm (6800- class) bearing. It took some effort to push it onto place, but there it went, anyway. I didn't bother to remove the other bearing. It seemed to be just OK

 

 

Now to the washers. I installed a 10x15 washer under the pivot, because the bearing was a bit deep.  I also installed two similar washers under the screw keeping things together. And last but not least, I installed a PTFE (Teflon) washer between the bearing arms. No more metal scraping against metal!

 

 

And, of course the same job on the other side.

 

After I had re-fastened the screws, I tried if there was any friction in the central pivot. To my great relief, there was just about none. Please note that the pivot bolt was tightly fastened while I tried this

 

 

EDIT: Just an illustration: Here is the original pivot bolt wiht the big washer that scrapes metal and creates friction; And then the new setup, where the small washer is on top the bearing, and does not interfere with the pivot arms. The scraping marks are still visible on the pivot arm

 

 

 

 

 

 

 

 

 

 

And finally, this shows how the suspension works with an empty shock:

 

After pumping some 200 PSI to the upper chamber and 50 to the lower chamber I did a test drive and everything seemed to me just fine.

I have no experience from other people's suspension wheels, and I don't know how they should feel, but at least I am happy now for my for my wheel

Now I can spend the rest of my life to figure out the optimal pressure on upper and lower chamber. And of course the proper amount of clicks on the damper

EDIT: Suspension still works pretty nice after almost two years. This is me driving on a normal gravel road:

 

-Z-

Edited June 5, 2022 by Zwheeler
even more pics

[Feynman]

I've decided to make some custom bushings for my suspension.  Waiting on 3/4" PTFE (teflon) mechanical grade rod to come it.  Have some 18mm thrust bearings I'm going to use on the connections between the two arms.   

[Zwheeler]

2 hours ago, FinRider said:

I’m gonna go play around with it now... I just need to buy another shock pump and elbows for the valves so I can monitor the pressures during the setup& sag tests...

I totally agree. After I bought an elbow for the upper chamber, I have been driving with the pump in my pocket. I like to have fairly big sag, because I consider the outward movement pretty important, too

And the negative chamber seems to follow the rule: Low pressure - a pogo stick; High pressure - smoothes the big pumps, but does not handle those small cobblestone- type bumps

But yes: it pays to try different pressures and drive. And if the need arises, you can just put the block in and check the "official" pressure 

-Z-

[UniVehje]

3 hours ago, FinRider said:

in other words, one should add positive pressure until the desired sag is achieved, then start to add negative chamber pressure until the suspension feels comfortable for the desired purpose (road, off-road, trails, jumps, etc).

This video might be helpful for setting up the rebound:

 

[Finn Bjerke]

This bearing  was missing in a KIngsong s18, making the suspension stiff? 


Im glad we can learn from you  Zwheeler of Finland, I hope Kingsong learns too.  It  could be interesting to find out how many have had  suspension stiffness problems? Others from Finland have fixed smiliar problems in other ways if I remember correctly from the "marathon thread"  about Kingsong s18. Ironicly I have read somewhere that ppl are adding washers not removing them?  " washers added on the central pivot, where yuo just removed that oversized one on the picture, others added one more in order to reduce friction in some way.  ( Ill find the text in a bit)    It seems to me Kingsong have poor quality control  maybe the safe and sane thing to do is to buy Inmotion V11 or wait for Kingsong to wake up, and get some quality control on the suspension system? This is early days. Im not a techie but I need to learn from you guys since Kingsong are too childish to have proper quality control, there has been trouble before I gather?  If my batch 2 s18 wheel gets here in 5-6 weeks time  ---- Ill start with a diagnostic check of  the wheels suspension system it seems.  I dont feel good about that at all really.  Also I prob need to order some spareparts before I ride it ?  Not riding it one day 1  requires more "sisu" than you expect from a Dane.  Thx to you constructive ppl.   Maybe it would be a good idea to Inform KS about wheel # something had errors? Maybe they dont give a toss about that ? 

Edited August 31, 2020 by Finn Bjerke

[Finn Bjerke]

Also from Finland the stiff suspension problem have been adressed in a differenct way: 

https://forum.electricunicycle.org/topic/17867-king-song-s18-discussion/page/111/?fbclid=IwAR2t2zLud9W4eoXhVlsefxFuZsyuy2-iP-79fCGcggq3_X1cj10lEp3dJBQ

Edited August 31, 2020 by Finn Bjerke
correction

[FinRider]

55 minutes ago, Finn Bjerke said:

Also from Finland the stiff suspension problem have been adressed in a differenct way: 

https://forum.electricunicycle.org/topic/17867-king-song-s18-discussion/page/111/?fbclid=IwAR2t2zLud9W4eoXhVlsefxFuZsyuy2-iP-79fCGcggq3_X1cj10lEp3dJBQ

Similar issue... Z and I have been chatting and discussing the mods that we are doing.

I would not attribute the stiffness of the suspension to poor quality or poor quality control by KS. It is more a general lack of understanding how suspension works, in other words it is an inherent design issue teamed up with poor execution in the assembly. Here are my key findings, all have been easy to identify and remedy:

• slider bars not paralell. Caused by the extra spacer block between the pipes that put undue pressure on the pipes at the bottom. This is also the far end from the connection point of the bars, so easy to push them out of alignment. We were told the block was put in place to prevent overtightening the pedal hangers. Solution was simple, just remove the block and lube the slider pipes.
• pivot arms. There are several problems here.
  • The pivot arms have no spacer between them, causing metal to rub on metal when they move independently. My solution was to put a PTFE spacer in between the pivot arms to create a point of contact with less friction. I also lube it regularly.
  • the outside washer on the outer pivot arm. The washer clamps the axle rod to the pivot arm, which is definitely not the intention as this prevents the pivot arms from moving, basically making the bearings obsolete. For now i have added a washer the puts pressure on the inner race of the bearing only and left the axle nut sligthly loose, i used blue loctite to secure the bolt to the ”axle”. And again, used lube. I have ordered some thrust bearings that i will use in its place, but need to wait a month or so before they arrive.
  • lube the shock fastening points
  • Then there are still the other connection points of the pivot arms that need to be addressed. The wheel needs to be dis-assembled to get access to these locations so I have not identified if I have a problem in this area but others have had torn bearings from the spring washer that is used here. I will know more once I have opened up the wheel what the status is for my S18 and how I will attempt to rectify this. I feel a thrust bearing could do the trick if I can fit it in there. From the looks of it, it should fit as the spring washer takes up some space and the thrust bearings I found are only 2mm thick.

all in all, it just needs some minor tweaks and TLC to spring to life (pun intended).

[Finn Bjerke]

Impressive mate. I am very greatfull for this info. Im seriously considering not to buy S18 now. Your info is very important also ita Also very technical, some pix would help me understand better. I get my S18 in 4 weeks or so. First things is diagnosing  not pumping and riding? .....  So far my conclusion is:
This wheel is made by retarded engineers - suspension is not a new idea they bloody well should know better. "a general lack of understanding how suspension works" is just not good enough, the wheel after all is very expensive.  Im notsure I have the patientce to search the globe for alternative spareparts .... But Im happy some other folks find em for me... Really its Kingsongs jiob is it not? 

Digression: Off roading 
The most wonderfull lass lives in Turku, Finland  - we used to like certain types of  friction together and we didnt bloody lube very often.  When the rubber hits the road I want the wheel to be the same way.  My understanding of friction and lube is very primitive I admit that but I cant dis-assemble the wheel in order to check all contact points, I did not do that to the Turku lass either.   So as you can tell in familiar with TLC even in your country but dis-assembling is not for me at least not a "minor tweak"  its a major head ache really. 

 

Edited August 31, 2020 by Finn Bjerke

[Finn Bjerke]

Some interesting dis-assembling here: 

 

[Finn Bjerke]

Any guarantee left now? 
 

[FinRider]

3 minutes ago, Finn Bjerke said:

Impressive mate. I am very greatfull for this info. Im seriously considering not to buy S18 now. Your info is very important also ita Also very technical, some pix would help me understand better. I get my S18 in 4 weeks or so. First things is diagnosing  not pumping and riding? .....  So far my conclusion is:
This wheel is made by retarded engineers - suspension is not a new idea they bloody well should know better. "a general lack of understanding how suspension works" is just not good enough, the wheel after all is very expensive.  Im notsure I have the patientce to search the globe for alternative spareparts .... But Im happy some other folks find em for me... Really its Kingsongs jiob is it not? 

Digression: Off roading 
The most wonderfull lass lives in Turku, Finland  - we used to like certain types of  friction together and we didnt bloody lube very often.  When the rubber hits the road I want the wheel to be the same way.  My understanding of friction and lube is very primitive I admit that but I cant dis-assemble the wheel in order to check all contact points, I did not do that to the Turku lass either.   So as you can tell in familiar with TLC even in your country but dis-assembling is not for me at least not a "minor tweak"  its a major head ache really. 

 

I hear you loud and clear. In all honesty though, all the required ”fixes” that I have had to do was completed with a size 5 allen key... well, actually 2 of them as that is needed to get the pivot joint axel nut thingy out to put the nylon washer in between the pivot arms. And lube is your friend  so while you are at the hardware store to get your washers, pick up a can of teflon lubricant. 
 

now getting to the other bearings on the pivot arm will be more challenging, although anyone buying an ”early batch” EUC should be prepared to do some reverse engineering, fixing, modding, hot rodding, whatever you wanna call it. After all, we are dealing with chinese designed and assembled products here and they are not really known for their quality workmanship... if you are afraid to get your hands dirty, then stick to a more mature wheel for a while until the suspension wheels have been around for a while... it seems to take a year or so for the kinks to get worked out at the factory.

[Feynman]

I'm guessing they used the washer on the outsides of the middle arm connections to put the shear force on more area of the arm.  The lip holding the bearings in the out arm is about 2.3mm thick (Pocket A in pic), so any force along the bolt axis on this connection is on that small lip.  That said, I don't know how much force is to be expected here since the assembly is rigid and shouldn't twist much at all.

 

Also, I think that raised ring on 'D' below is meant to be a spacer of sorts.  I'm thinking of grinding this off to use a proper low-friction spacer. This raised ring is 1.45mm heigh.

Edited August 31, 2020 by Feynman
Added new thought

[FinRider]

3 minutes ago, Finn Bjerke said:

Any guarantee left now? 
 

I cant wait to get to this stage in tearing my wheel down. Just need to have a weekend with rain so that i am not tempted to go riding instead of tearing into the s18....

[eve]

Big thanks for that quickfix guide! @Zwheeler

I will probably do that and rework it fully after i get a fox shock on it. 

[Feynman]

Maybe this will help some people get their suspensions back together.  

The A -> D connection has a total of 4 bearings and that large washer on the outer arm.  Connections C has dual bearings. B has a single bearing.   Pocket D has a raised lip on the top to act as a spacer.  I'm going to grind this off.  

Edited August 31, 2020 by Feynman

[BFE Duke]

7 hours ago, Feynman said:

The A -> D connection has a total of 4 bearings and that large washer on the outer arm.  Connections C has dual bearings. B has a single bearing.   Pocket D has a raised lip on the top to act as a spacer.  I'm going to grind this off.  

Oh geez, looks like I misunderstood what you meant before when you said there were 2 bearings in each pocket. So there are 4 bearings total in that joint! Now what StuartL says makes sense, and I agree with him. Still, they could've done away one of those pockets on each side and it would work fine while eliminating the need for 4 extra bearings. I'm probably not gonna bother trying to size up some bushings and will just use the stock bearings. I wouldn't throw away that big washer on the outside though. It can serve as a shield against rocks or debris, since there is a very vulnerable rubber seal exposed. It just needs to be spaced out so that it's not scraping the outer pivot. 

[Feynman]

Here's one of the bushings I'm going to use in pocket 'A'.  It will extend 2mm into pocket D and protect the 18mm thrust bearing that will be between the two bushings here.  That's a render from Fusion360 btw, bushing will be made of PTFE.  I'm going to file down the raised lip around pocket D - the bushing will create the necessary space between the parts.

Edited September 1, 2020 by Feynman

[Finn Bjerke]

Fix thangs with a grinder ? guarantee is stonedead after that I guess? But who cares ?

[Feynman]

$843 quote for custom PTFE bushings.   Yeah, might be buying a lathe after all.  Or I could just drill out my PTFE rod with the drill press and live with less-sexy custom bushings.  

[Finn Bjerke]

Overhaul ?
If my wheel is not functional out of the box after pumping it up here and there  - Ill just bloddy return it ?  Ill buy the other suspension wheel instead ?  So what is the test of rigid suspension after åpumping the s18 here and there ? Is all this fixing really needed on a new batch 2 wheel?

Edited September 1, 2020 by Finn Bjerke

[Feynman]

1 minute ago, Finn Bjerke said:

Overhaul ?
If my wheel is not functional out of the box after pumping it up here and there  - Ill just bloddy return it ?  Ill buy the other suspension wheel instead ?  So what is the test of rigid suspension after åpumping the s18 here and there ?

Mine actually worked ok out of the box.  

[BFE Duke]

1 hour ago, Feynman said:

$843 quote for custom PTFE bushings.   Yeah, might be buying a lathe after all.  Or I could just drill out my PTFE rod with the drill press and live with less-sexy custom bushings.  

Drilling does not give you a clean enough hole for bushing purposes. You will want to drill undersized and then use a properly sized reamer. It's also kinda difficult to get the hole perfectly centered without a guide. It's really a job for a lathe...

Edited September 1, 2020 by BFE Duke

[Feynman]

Just now, BFE Duke said:

Drilling does not give you a clean enough hole for bushing purposes. You will want to drill undersized and then use a properly sized reamer. 

I'm sure you're right.  I'm thinking the bolt coupler axles will wear the teflon holes nice and smooth, though.