Sticky Sherman S suspension

[supercurio]

The Suspension of my Sherman S unit that just arrived is pretty sticky and nowhere near what I expected from the review hype.

Out of the box it's kind of comparable to original S22 sliders - although not as bad. Nowhere near the smoothness of a S22 with CNC sliders rolling on POM wheels provides with virtually zero perceivable stiction.

I'm puzzled and wondering what do do with this wheel. Are all the Sherman S like that? Is that one defective (shocks, misalignment, something rubbing)

Could you show me yours doing the same test?

 

[supercurio]

Cataloging replies or additional tests so far:

Jonathan Lachapelle

Quote

Mine is brand new never ridden yet, and zero sticking when I pressed the suspension gradually by hand.

OneRoll Lou

Quote

Mine does the same thing but when riding it’s still smooth

[video of another test]

Steve Evans

Quote

just tested mine and it does not do that (mine has smooth travel). i have 300 miles on my wheel so perhaps it just needs use to loosen up?

Quote

i did not do that test when i first got the wheel. but the wheel seems to ride the same with no change in suspension from new that i can detect.

 

Edit:

Someone copied and re-uploaded my video on Facebook with a negative tone, but there's a bunch of feedback in the comments with multiple riders confirming that their unit "comes down and up like its nobody's business smooth like butter" or "there is absolutely no stiction."

Edited February 3, 2023 by supercurio

[Finn Bjerke]

Clever test very interesting ... Thx you good people

[Planemo]

5 hours ago, supercurio said:

The Suspension of my Sherman S unit that just arrived is pretty sticky and nowhere near what I expected from the review hype.

Yeah that doesn't look great.

Funnily enough I stripped down a brand new pair of Rockshox Domain MTB forks recently purely to carry out some stiction tests. I think I ended up with about a 6lb load to break stiction which by all accounts is pretty good especially for an air fork with the added seals for the air chamber which don't exist on a coil. No idea what load you are applying to that Sherman with your hands though.

[supercurio]

@Planemo I was thinking about how to measure the load necessary to break stiction in that case, since I can't remove the spring.

I'll give it a shot tomorrow, taking an average to break from stiction at the (inaccurate as a result) sag point of the suspension under the wheel's weight.

Regarding temperatures since it was a common question, the result appears identical at room temps 6h later as it was at approximately freezing temp earlier.

Edited February 1, 2023 by supercurio

[MrMonoWheel]

I have noticed my batch  1 SS has some stiction but its not noticable when riding. 

[supercurio]

@MrMonoWheel thanks for the the addition data point 🙏 Would you be able to record a demo of it, slowly pushing it down then letting it back up to give a point of comparison?

Also, did it evolve over time in any way?

Edited February 2, 2023 by supercurio

[Planemo]

57 minutes ago, supercurio said:

@Planemo I was thinking about how to measure the load necessary to break stiction in that case

Yes I was thinking about that. It's a lot easier on MTB forks as I just used a common baggage/suitcase scale which has an attached strap. I just wrapped it around the steerer tube then I could just easily pull down and the highest poundage is recorded on the screen. Not sure how you would do it with the sherman - probably need to have it elevated and supported under the pedals on a bench, tie a piece of rope across the top and down either side of the wheel then attach the scale to the string under the tyre somewhere.

I tested my forks with/without the dust seals and oil sponges. It was really a test to see how tight the internal bushings are (which is the main culprit in most forks). Many forks come with bushes far too tight which causes havoc with stiction. Mine were actually OK though, in fact really good - without seals the stanchions dropped under their own weight which is ideal (as long as theres no play either!)

Also critical is the axle width - my forks unfitted with a wheel were 109.5mm. The wheel hub was pretty much bang on at 110.02mm (should be 110mm). Tests with and without the wheel fitted made a big difference to stiction so even a 0.5mm difference on the axle is a big deal when it comes to the tiny tolerances we are talking about regarding the bushing clearances inside the forks. The Sherman may suffer even more with this during riding because I'm not convinced that the forks are as solidly locked together (apart from the axle) as they are on an MTB.

[Planemo]

18 minutes ago, MrMonoWheel said:

I have noticed my batch  1 SS has some stiction but its not noticable when riding. 

Stiction is stiction. It doesn't go away when riding, it may just be less noticeable than when pushing on the wheel static. But it's still there.

You can't really get a feel for how much stiction is there until you try something with minimal stiction. The difference can be extreme.

[MrMonoWheel]

21 minutes ago, Planemo said:

Stiction is stiction. It doesn't go away when riding, it may just be less noticeable than when pushing on the wheel static. But it's still there.

You can't really get a feel for how much stiction is there until you try something with minimal stiction. The difference can be extreme.

Oh yeah I know. Everything from my $15k motorcycle to my V11 has stiction of some sort, its also impossible to avoid. But I agree, excessive stiction is no bueno. I would say mine is minimal (for now).

 

30 minutes ago, supercurio said:

@MrMonoWheel thanks for the the addition data point 🙏 Would you be able to record a demo of it, slowly pushing it down then letting it back up to give a point of comparison?

Also, did it evolve over time in any way?

I will try to get a video, its hard to show but I will do my best. It definitely wasnt there when I first got the wheel and occured as time went on, but it doesnt seem like its gotten any worse than the first time I noticed it. 

 

Edit: now that I have taken the video, I would say the stiction is actually pretty decent. I will post it here when it uploads.

Edited February 2, 2023 by MrMonoWheel

[supercurio]

Thanks @Planemo for this perfect introduction into how to approach this 🙏

8 minutes ago, Planemo said:

Yes I was thinking about that. It's a lot easier on MTB forks as I just used a common baggage/suitcase scale which has an attached strap. I just wrapped it around the steerer tube then I could just easily pull down and the highest poundage is recorded on the screen. Not sure how you would do it with the sherman - probably need to have it elevated and supported under the pedals on a bench, tie a piece of rope across the top and down either side of the wheel then attach the scale to the string under the tyre somewhere.

From your description it seems the method can be adapter with:

• placing a scale on top of the wheel
• and measuring how much weight is needed to break the stiction

That seems straightforward enough!

8 minutes ago, Planemo said:

I tested my forks with/without the dust seals and oil sponges. It was really a test to see how tight the internal bushings are (which is the main culprit in most forks). Many forks come with bushes far too tight which causes havoc with stiction. Mine were actually OK though, in fact really good - without seals the stanchions dropped under their own weight which is ideal (as long as theres no play either!)

Okay so that's inside the shocks.
If that's the culprit, would extracting the shocks and compressing them manually out of the wheel be a conclusive test?
I'm not sure if external forces like the ones coming from misalignment would play a role here or not, if we're looking at the effects of a bushing that's too tight.

8 minutes ago, Planemo said:

Also critical is the axle width - my forks unfitted with a wheel were 109.5mm. The wheel hub was pretty much bang on at 110.02mm (should be 110mm). Tests with and without the wheel fitted made a big difference to stiction so even a 0.5mm difference on the axle is a big deal when it comes to the tiny tolerances we are talking about regarding the bushing clearances inside the forks. The Sherman may suffer even more with this during riding because I'm not convinced that the forks are as solidly locked together (apart from the axle) as they are on an MTB.

That's why I am weary of accepting that wheel and not attempting to get a replacement right away.

What if the root cause is bad tolerances of the the motor shaft or other parts securing the shocks in place, making perfectly fine shocks perform poorly?
I'm open to suggestions on method to identify which is the root cause, even if it's a rough idea in order to get a starting point in the discussion with the dealer tomorrow.

I mentioned bad tolerances on the motor shaft since axle tolerances were known to cause major issues on the S18 sliders where both wouldn't be parallel.

 

17 minutes ago, Planemo said:

Stiction is stiction. It doesn't go away when riding, it may just be less noticeable than when pushing on the wheel static. But it's still there.
You can't really get a feel for how much stiction is there until you try something with minimal stiction. The difference can be extreme.

I'm sure many riders can get used to stiction in a way that they've learned to accept it as how the suspension behave.
Like you said, now I already have a reference of suspension wheel with virtually no stiction at all. It started with Nylon wheels on S22 3D printed sliders, and I have CNC rollers and POM wheels to upgrade it now. The difference, seemingly small between some stiction and no stiction is much greater than anticipated - once riding.

Despite the S22 rocky start, I think that our Russian friends invented a uniquely smooth suspension design with the POM rollers mod, which probably surpasses conventional approaches in various ways.

 

14 minutes ago, MrMonoWheel said:

Oh yeah I know. Everything from my $15k motorcycle to my V11 has stiction of some sort, its also impossible to avoid. But I agree, excessive stiction is no bueno. I would say mine is minimal (for now).

Good to know, now I'm even more curious to see it.

I also really wonder how many Sherman S received units with sub-par suspension like mine, but didn't dare to say anything or dismissed their own impressions since all reviews describe it as the best suspension out here.

From tests already completed, I'm expecting a pretty large amount of variation.
Damn, if it's many and it catches on, LeaperKim will become the next OEM to wish they never heard about me.

 

14 minutes ago, MrMonoWheel said:

I will try to get a video, its hard to show but I will do my best. It definitely wasnt there when I first got the wheel and occured as time went on, but it doesnt seem like its gotten any worse than the first time I noticed it. 

Super interesting that you can tell that it evolved over time. It makes me wonder if some maintenance (cleaning the dirt in seals) could help in that case.

[MrMonoWheel]

7 minutes ago, supercurio said:

Super interesting that you can tell that it evolved over time. It makes me wonder if some maintenance (cleaning the dirt in seals) could help in that case.

I dont believe it to be caused by any dirt ingress, as when I disassembled my wheel there were no signs of dirt around the stanchions. Usually if there is enough dirt that it gets into the seals, there will be a dirt ring around the polished section of the fork. It just seems to be internal. One hypothesis was that there is not enough fork oil in there which causes upper bushings to become drier and sticky vs the well lubricated lower bushings that are submerged in oil. I would be interested to open up one of the forks and see how much fork fluid is actually inside, then perhaps add more and see how it changes the suspension.

[MrMonoWheel]

 

[supercurio]

About the same as mine @MrMonoWheel! I can also count 3 steps in my demo, plus one if I pull it up.
Thanks a lot for the perfect demo.

Not that they really are "steps" at fixed anchored position, but more how it works out when jumping up and down by releasing the energy accumulated by the stiction I suppose.
Okay so there's definitely a problem identified here. This is not at all how the suspension is supposed to perform.
This doesn't look much better if any than stock S22 sliders. Plenty of people tolerated them even though they were bad, as long as it was all there was - but still not good enough IMO.

Your mention of the motor misalignment is not innocuous IMO. It has to apply undesirable forces on the stanchions.

Damn, if I knew this was what I signed for I would have cancelled the order long ago.

Edited February 2, 2023 by supercurio

[Planemo]

8 minutes ago, supercurio said:

Thanks @Planemo for this perfect introduction into how to approach this 🙏

From your description it seems the method can be adapter with:

• placing a scale on top of the wheel
• and measuring how much weight is needed to break the stiction

That seems straightforward enough!

For sure that would work great, as long as you can get some scales that are relatively accurate and have a 'peak hold' function as when that stiction breaks it's too quick to get a decent reading by eye.

8 minutes ago, supercurio said:

Okay so that's inside the shocks.
If that's the culprit, would extracting the shocks and compressing them manually out of the wheel be a conclusive test?

It depends on how far into the rabbit hole you want to go! Identifying the cause of stiction is simply a matter of elimination. Often it's a combination of several factors. For example on any MTB fork I always swop out stock dust seals for SKF manufactured ones as my tests show they are far better. But basically any sliding component needs testing individually - bushings are usually my start point, that means the entire fork stripped down to nothing except stanchions. Then I re-test with sponges and dust seals fitted, then I check the damper and air pistons and finally the axle width. The best fork in the world can be buggered by an incorrect axle width so if it's not right it means either machining down or adding spacers to the hub. Manufacturers should be reaming bushes with a dummy hub of the correct width fitted but like anything how accurate is their hub? How good is the reamer? Lower end forks don't even get reamed - the bushings are fitted and they hope for the best. Some come out a bit tight, some a bit ovalized, some a bit loose. This is why some forks even from the same manufacturer feel completely different.

All in all, as MrMonoWheel rightly says, there will always be stiction. But I hate it with a passion so I will do whatever I can to minimise it. Reaming tools are bloody expensive though!

 

8 minutes ago, supercurio said:

What if the root cause is bad tolerances of the the motor shaft or other parts securing the shocks in place, making perfectly fine shocks perform poorly?

And thats exactly the possibility you can get. But without testing at different stages of disassembly theres no way of knowing which part of the system is the problem

8 minutes ago, supercurio said:

I also really wonder how many Sherman S received units with sub-par suspension like mine, but didn't dare to say anything or dismissed their own impressions since all reviews describe it as the best suspension out here.

This is exactly what we have with EUC's unfortunately. Very few riders have experience with MTB suspension and even fewer have the knowledge to say 'hmm this isn't right, I'll strip this bugger right down' and instead simply ride on blissfully unaware. Unless it's shockingly bad of course. But on the flip side I guess many folk would consider even poor suspension better than no suspension so there is that.

[MrMonoWheel]

11 minutes ago, supercurio said:

About the same as mine @MrMonoWheel! I can also count 3 steps in my demo, plus one if I pull it up.
Thanks a lot for the perfect demo.

Not that they really are "steps" at fixed anchored position, but more how it works out when jumping up and down by releasing the energy accumulated by the stiction I suppose.
Okay so there's definitely a problem identified here. This is not at all how the suspension is supposed to perform.
This doesn't look much better if any than stock S22 sliders. Plenty of people tolerated them even though they were bad, as long as it was all there was - but still not good enough IMO.

Your mention of the motor misalignment is not innocuous IMO. It has to apply undesirable forces on the stanchions.

Damn, if I knew this was what I signed for I would have cancelled the order long ago.

When I get the new bearings I will make an effort to keep the wheel aligned as I reassemble and will see if that removes some of the stiction. Honestly until now I didn't even notice the stiction and tbh it doesn't bother me. Riding this wheel still feels like I am on a cloud and I can't expect the suspension to be as top tier as the stuff I find in my motorcycles. These wheels are made in the hundreds vs motorcycles that are made in the thousands. Furthermore, this is the first suspension of this kind made for an EUC whereas they have been doing it for decades for motorcycles and bicycles. Idk, maybe I just had my expectations much lower than everyone else since I paid close to $1k less for my wheel, but aside from the bearings shitting out I am a happy camper. 

[supercurio]

Glad you're having a blast with your wheel @MrMonoWheel regardless, and that you're happy thanks to a start from low expectations.

It's probably because I already spent months experimenting tuning suspension through 3D printed S22 sliders project materials research, and reach excellent results that it became my baseline, setting the level of expectation here after I learned what an EUC suspension is capable of. Same as you.. reversed 😆

Essentially, anything that performs significantly worse while I was expecting even better is a bummer. I tend to prefer no suspension to sticky suspension, I feel like it gets in a way of the road feel and give an inconsistent experience.

 

18 minutes ago, Planemo said:

For sure that would work great, as long as you can get some scales that are relatively accurate and have a 'peak hold' function as when that stiction breaks it's too quick to get a decent reading by eye.

I'll use video to capture the peak. For now the scale I have can only do 2kg, maybe that'll be enough, but then it would be only little compared to the 6lbs on the fork you mentioned ave.

21 minutes ago, Planemo said:

It depends on how far into the rabbit hole you want to go! Identifying the cause of stiction is simply a matter of elimination.

I really don't want to but it seems I started anyway  🙈

If the root cause is the shaft then I absolutely want to return and exchange it. AliExpress seller tho, that would be tough negotiation and I would need solid evidence.

23 minutes ago, Planemo said:

and instead simply ride on blissfully unaware

Blissful ignorance, sometimes I wish.

[Planemo]

37 minutes ago, supercurio said:

I'll use video to capture the peak. For now the scale I have can only do 2kg, maybe that'll be enough, but then it would be only little compared to the 6lbs on the fork you mentioned ave.

It is quite surprising how much force is required when you actually put a number to it. Using hands I didn't think the totally stock forks were too bad but they measured a lot more than it felt! If you are bored and fancy a (very long) read on bushing info, theres an excellent thread here: Tight Bushings = Harshness | Mountain Bike Reviews Forum (mtbr.com)

It discusses MTB forks but I am quite confident that the same bushing design is used on the Sherman. As I say though, bushings are only one part of the jigsaw.

[Planemo]

1 hour ago, MrMonoWheel said:

When I get the new bearings I will make an effort to keep the wheel aligned as I reassemble and will see if that removes some of the stiction.

The only real way of finding the 'sweet spot' regarding the width of the legs is to first take poundage readings with an unmounted wheel to give a baseline, then make an adjustable 'axle' using threaded bar and some nuts/washers. You can then either expand or contract the legs whilst taking further readings to see if stiction goes up or down. As I say my forks were 109.5mm without a wheel and my wheel hub measured 110.02. I took poundage measurements at 109.5 and 110.5 and stiction on both was increased compared to the best being at 110, so 110 was indeed the sweet spot and given my wheel was only + .02mm on that I got lucky and didn't have to machine/shim the hub. I would say that anything more than 0.3mm at the axle would benefit from working on the hub because at 0.5mm the stiction was definitely escalating.

If we really go into the rabbit hole....it's worth noting that if the forks aren't parallel you might spend a lot of effort to get low stiction at your sag point (where most people test) but test them again at max travel and they start binding...as you would expect. It might be that had you not spent all the time you did on minimising stiction at sag only, the forks may well have been better 'overall' through the entire travel. You can end up chasing you tail but I guess the moral is, you really need to be taking readings at not only sag but also full compression.

Are the Sherman forks built and more importantly, supported well enough to maintain a max of 0.3~0.5mm out of parallel? I've no idea. I'm just throwing it out there because I have found it really doesn't take a lot to send stiction through the roof with even 'small' amounts of leg deflection. Bear in mind that the bushing clearance on most forks isn't a lot. Fox for example use minimum at 0.0015" (0.00381 mm) and max at 0.0090" (0.02286 mm).

Edited February 2, 2023 by Planemo

[MrMonoWheel]

5 hours ago, Planemo said:

The only real way of finding the 'sweet spot' regarding the width of the legs is to first take poundage readings with an unmounted wheel to give a baseline, then make an adjustable 'axle' using threaded bar and some nuts/washers. You can then either expand or contract the legs whilst taking further readings to see if stiction goes up or down. As I say my forks were 109.5mm without a wheel and my wheel hub measured 110.02. I took poundage measurements at 109.5 and 110.5 and stiction on both was increased compared to the best being at 110, so 110 was indeed the sweet spot and given my wheel was only + .02mm on that I got lucky and didn't have to machine/shim the hub. I would say that anything more than 0.3mm at the axle would benefit from working on the hub because at 0.5mm the stiction was definitely escalating.

If we really go into the rabbit hole....it's worth noting that if the forks aren't parallel you might spend a lot of effort to get low stiction at your sag point (where most people test) but test them again at max travel and they start binding...as you would expect. It might be that had you not spent all the time you did on minimising stiction at sag only, the forks may well have been better 'overall' through the entire travel. You can end up chasing you tail but I guess the moral is, you really need to be taking readings at not only sag but also full compression.

Are the Sherman forks built and more importantly, supported well enough to maintain a max of 0.3~0.5mm out of parallel? I've no idea. I'm just throwing it out there because I have found it really doesn't take a lot to send stiction through the roof with even 'small' amounts of leg deflection. Bear in mind that the bushing clearance on most forks isn't a lot. Fox for example use minimum at 0.0015" (0.00381 mm) and max at 0.0090" (0.02286 mm).

I'm just gonna wing it and hope for the best 

[Finn Bjerke]

Is this the reason ? forgive for being naive

More info here ecodrift   https://ecodrift-ru.translate.goog/2022/11/15/veteran-sherman-s-razbiraem/?_x_tr_sl=ru&_x_tr_tl=en&_x_tr_hl=da&_x_tr_pto=wapp

[Planemo]

Thats not a seal, simply a clamp to mount the forks to the motor. As you note though, the protruding bolt is not good at all. I would definitely be grinding the bolt head down but unfortunately at this point of full assembly the damage has already be done. It might be fine but the tubes are pretty thin and it wouldn't take much of a protrusion into the outer to affect the inner surface. I guess one bonus of them being coil is that the inner surface won't have an airseal but it may well have the damping piston running past it. Not as critical as an air piston though.

Edit: whilst that wheel is out I would deffo take the opportunity to do some stiction tests. Find out at what width the forks work best then measure the distance between the centre of the curved mounts on the motor. It would be a bummer if they were too narrow as machining a small amount off them would require some pretty fancy milling tools. If they were too big though, some thin shim stock might help a lot. 

Edited February 2, 2023 by Planemo

[Rawnei]

Would be interesting if someone who's got one with stiction and who says "I don't notice it when riding" got to compare it to one without stiction to see if they notice the difference. 😁

[Planemo]

It would all depend on the surface. Stiction really messes up small bump compliance but on heavy impacts it doesn't make nearly as much difference.

So for woodland trails (small stones/branches etc) or say bumpy pavements a reduction of stiction can really make a much nicer and more comfortable ride. some describe it like 'magic carpet ride'. Throw your wheels down stairs or MTB black runs though and not so much...

[supercurio]

1 hour ago, Rawnei said:

Would be interesting if someone who's got one with stiction and who says "I don't notice it when riding" got to compare it to one without stiction to see if they notice the difference. 😁

You can tell about the stiction as soon as you put your foot on one pedal to mount on the wheel.
Instead of going down gradually as you'd expect, it jerkily jumps down as you put your weight on it.

Agree with @Planemo, riding conditions that force the suspension to keep moving big would make stiction less obvious. But in order to ride, you have to get on the wheel first 😁