Not Matrix II related - FW4 bug causes wobbles

This thread started about problems with wobbles at speed and I thought the trucks were the root. But it’s a bug in the FW4.0 and 4.1.

That’s what I’m talking about

Jump to post#49 for the solution no more wobbles

Original post:

I have some weird problems with the oil-slick Matrix II trucks and can’t find any solution.

First of all they look great :grin:

The biggest issue is that I get crazy speed wobbles on the rear truck

  • with orange shock blocks (medium) at about 28-35km/h (17-22mph) depending on pre-tension

  • with slightly compressed´red red shock blocks at 40km/h (25mph)

  • with compressed red shock blocks at 42km/h (26mph)

The top speed of this board is 54km/h (33.5mph)

On the MBS DWII deck I also use black Matrix II trucks with cranked down orange shock blocks and have zero problems with speed wobbles (top speed 40km/h | 25mph). So what is happening here?

The obvious difference is that the MBS deck is very stiff and has concave and the Trampa is flexy, flat and can twist. But on the other hand I’m not the only one with this trucks on a Trampa deck.

I am 90% sure it’s a problem with this (set of) trucks but also thinking about other possibilities. The thing is that I also switched to new motors and FW4.01. After the last ride I checked and compared all settings of both vescs to get sure it’s not a restricting or strange setting somewhere. I know that if one vesc cuts power (e.g. if one motor is too hot) it also feels a bit like a speed wobble. But the motors were just warm and also unweighted I could accelerate to full speed.

All speed wobbles occured during (normal to) hard acceleration. I could test what happens if I just roll down a hill without or just a little bit acceleration above 40km/h (25mph). That’s the only idea for now so please share your thoughts if you have something in your mind.

Thanks :grin:


Does it look slighty bent?

  1. Check if the king pin sits correctly with no play.
  2. Double check if your shock blocks are tighted equally, or if there are any asymmetries.
  3. You need to get used to the deck and trucks.

I ride yellow/yellow blocks and have no wobbles or whatsoever at over 60km/h.


The MBS dw2 deck has a different angle as well, doesn’t it?

Maybe get some etoxx angle riser to get the angle down done a bit


Does your kingpin come loose after riding for a while? Sometimes I can hear the washer rattling around after riding hard.

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No it’s straight but the profile of the oil-slick hanger is askew. I’m not joking when I say it took me 2 weeks to solve this problem (including depressed breaks). My black Matrix II hangers have a much better profile, maybe it’s the oil-slick or just these hangers.

Askew in all ways with mounted motor mount.

My short solution was to make it straight with different tapes, that process took a while.

But one mount shifted a bit already after 30km (19miles) :rage:

I answer the other questions later at work, need to leave now…


My kingpin also loosened itself during my last ride and I’ve also almost lost my patience when setting up my motor mounts, since the oil-slick hangers seemed bigger than the original. I had to go to a garage shop so that they could use a hydraulic press to make the truck clamp fit…


I’m worried about the coating affecting my clamps as well. Might be a one time installation.

I’m either adding some blue loctite to the end of my kingpin or another nylon nut if it’ll fit.

Mine might just be getting old as well.

@mbs could you provide the matrix 2 kingpin bolt and nut specs for reference?

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I’m starting to wish Matrix Oil’s were not my first channel trucks - looking at mine hopefully right now lol


You sure it’s not the wheels being out of balance?
Weird issue. Hope you track it down. :+1::grin:


:crazy_face: you must be light-weight, that sounds dangerous. But it seems my problem are not the shock blocks

Kingpin is tight without any play and shock blocks compressed symmetric. I ride the Trampa deck since 3 years and I also know the Matrix II trucks from my other MTB, just not in this combination.

True it’s 30° and the Trampa 35°, I have angled risers from E-Toxx but this would decrease the turning radius further. The main reason why I switched to Matrix II trucks is because they are carvy. But with cranked down red shock blocks on 35° it’s not that carvy anymore. The other reason was that Matrix II trucks need no machining for gear drive (in theory). I killed 6 Trampa trucks within the last 2 years and need to save some money.

Yes but not after a while, every 10-15 minutes the hanger is completely loose. But I solved that problem (I guess) by adding a second locknut (mounted with the locking side first). At least at my last ride I had no more problems with that.

Did you check if the hanger has some play when the kingpin is tightened? I had some troubles in the beginning but Joel (@MBS) posted a perfect answer/solution about correct position of the washer, here a screenshot of his post, could be helpful for others, too.

They are fine but I’m a bit out of balance :laughing:


But if you stable at 30 degrees on the dwII deck it’s worth a try I think. Maybe start with reduction in the back and see if it helps.

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100kg equipped :smiley: doesn’t feel so dangerous :stuck_out_tongue_closed_eyes:

I don’t think you go faster than 12mph in that whole video. not sure what it’s supposed to prove but it sure as shit don’t show that your board is set up to be stable at 60km/h.


Never claimed such a thing for that video and I don’t have to prove anything.

Try dewedging the rear to about 25°. I’m running a Comp 95 with yellows loose af up front, and oranges loose to medium tight on the rear dewedged -5°, so 30/25 split. That little change in the rear was huge. Feels way more stable up to 30mph+ (50kph), with no wobbles at all. Still feels quite maneuverable with loose trucks in the front, so with your 35° noise, you should still have good steering even with stiffer blocks. That’s assuming, of course, that your wheels & tires are balanced well. I originally got wobbles on the bench before balancing my wheels, and I’m sure that contributed to wobbles on the street. After balancing and dewedging, smooth and stable af, even that time I ran fully loose yellows in the rear and NO blocks up front :astonished:, you know, for science. Also, I’m around 80-90kg depending on whether I’m riding butt ass nekkid, or fully geared up, so I’m no lightweight. :kissing_heart:

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The Matrix II king pin is an 8mm x 80mm shoulder bolt. Note: Those are the dims of the shaft (not including the threads) - refer pic. The king pin thread spec (and associated nut spec) is M6.


Yeah, I can back this up. Decreasing back angle makes a huge difference. You can increase front angle to compensate. Wobbles primarily originate from back truck. You can get an equal turning radius with much less wobble but it does change the feel of the carve. Stiffer blocks in back is good too for the same reason (as others have said).

As for @rich’s wobble specifically, I’m perplexed. The Matrix IIs really are good in that department so I’m thinking it could be power related but that could just be old fashioned blame shifting. I’m interested to hear the results of the unpowered downhill speed test.

The askew mount too is weird too. Is it the same on both sides of the truck? Is the other truck the same (if that’s easy to test)?


I can try to decrease to 30° or even 25° and see if the speed wobbles still occur but first I’ll try a few other things. First I want to compress the red shock blocks further for science. Also riding downhill without power is interesting. I just hope the brakes are strong enough to stop the possible wobble :joy:. Or if there is no wobble it could start during braking :thinking:. Need to work on the weekend but gonna test it next week and report back.

Maybe I’ll try to film the speed wobble as well, wanna see how it looks.

Yeah it’s really strange especially because I don’t get speed wobbles on the DWII board with orange shock blocks. Also after further searching in the forum I found more post about people riding Matrixx II trucks with orange (or even yellow) shock blocks above 30mph.

The same but different askew. I can’t try it on the other truck now but I would guess it’s the same. I don’t know if it’s the batch or the oil-slick only but the shape is a tiny bit different to the black Matrix II trucks I have. That means when I push the motor mount against the hanger (without bolts) it wiggles on the oil-slick and stays put on the black hanger. For normal MTB it makes zero difference so there is nothing to blame but in combination with the motormount (or at least the one I use) it does.

I counter-balanced all wheels before filling in some green slime (it’s not possible afterwards), now they a bit out of balance but not dramatic. I can lift the rear and go full throttle without problems.

:joy: sounds like a good training for balance!

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Just out of curiosity, does this happen the moment you reach top speed when accelerating ?
I recently noticed some weird behaviour on my MTB where it feels that the motors do not top out at the same time.
This leads to a wobble exactly as it tops out. It is recoverable but not very pleasant. After that the board is stable as a rock.

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