Maxton GP20

[robsoup]

Hey did you end up getting the Maxton suspension? What did you think of it. I'm currently weighing up K-Tech and Maxton...

Not yet sadly, I'm kinda iffy about the lack of adjustable compression damping to be honest. Still weighing my options, no rush since the riding season is about to end here in Sweden anyway.

Apparently from my enquries they are happy to give you all the adjustment you want in the cartridge kit (rebound, compression, preload), but they advise that having the compression adjuster at the top of the fork will result in a harsh ride, so better to have the compression at the bottom of the fork (however this would require drilling the wheel spindle to allow adjustment of the compression damping without removing the wheel spindle). 

[rick]

Well, it might be a bit of a pita to get the compression set/fine tuned, but once set. f the valving is done properly for your weight/riding style to begin with, I suspect you'd rarely, maybe even never touch it again. imo, that inconvenience would take a back seat to having it work properly. 4 valves will always work better than 2 when the cartridge is this small in diameter.

[robsoup]

Yep and I that basis I think I will be going with the Maxton kit. Just need to decide on the level of adjustment I'm willing to pay for now...

[twf]

Not yet sadly, I'm kinda iffy about the lack of adjustable compression damping to be honest. Still weighing my options, no rush since the riding season is about to end here in Sweden anyway.

Apparently from my enquries they are happy to give you all the adjustment you want in the cartridge kit (rebound, compression, preload), but they advise that having the compression adjuster at the top of the fork will result in a harsh ride, so better to have the compression at the bottom of the fork (however this would require drilling the wheel spindle to allow adjustment of the compression damping without removing the wheel spindle).

What difference does location of adjuster make? Sounds like they don't know how to make it work correct. AK20 has adjuster on top, no harsh ride.
My kit has it same way, no harsh ride.
Many bikes have it that way stock from factory. 

[twotone]

^^Agree, Maxton produce some nice work, but spend little time in the unusual applications, eg; some forks that would require special attention to make both legs to work hydraulically, only get the functioning side modified, even though others have modded both legs. Save time and money.

[robsoup]

This is the brief email I have from Richard at Maxton:
 
 

The compression damping adjusters on the GP20 cartridges that are adjustable for compression damping are located down the centre of the bottom cartridge bolt that holds the cartridge in place. Some customers cross drill the wheel spindle to allow them to adjust the compression damping without removing the wheel spindle. In our opinion this is the only place to put the compression damping adjuster and still give a ‘plush’ ride. If you separate the rebound and compression damping and put the compression damping adjuster on one of the fork tops then the ride will always be ‘harsh’

This was in reply in reply to my email where I said I don't want harsh compression issues like the other kits (discussed in detail on here), and also enquiring about what level of adjustment they offer with the kits.
 
They still offer fork top adjustment for compression for customers who want ease of access.
 

[pattonme]

Is there a price difference between 'top side' and 'bottom' options? because it sounds like 'bottom' is a traditional cartridge config while the 'top side' either reverts to the simplified config and/or they haven't done the R&D to figure out how to get the mid-valve to flow sufficiently and still have a shim stack on it.
 

[twotone]

@robsoup
 
Sounds messy and expensive, by the time you pay for top dollar cartridge set, get Maxton to make you a set of compression adjusters, drill the front axle......
 
@twf recommendation you could go the Traxxion route and save yourself a lot of trouble

[rick]

Not sure I like the idea of drilling the axle. Do you guys really think there's a need to access that compression adjustment all that often. My thinking is that once a good feel has been met, you'll never touch it.

[twf]

You could say same for rebound. You either want adjusters or not

[pattonme]

by far most of my customers almost never change comp. Some try this or that the first couple of weeks of ownership and then find the setting they like and never bother to mess with it again. They have to pull the axle to get at it. Would I drill? No.
 
Rebound on the other hand IS useful 'day to day' (temps, road condition, street vs track) and easy access is a must very nice to have.

[rick]

True enough i guess - but.
 
After a few rides back in 2003, I set the rebound adjusters on my Aprilia to where I was pretty happy with the ride and haven't really changed them since. The compression in those Showa legs is not adjustable - and so what.
 
Might come in handy going from street to track - i think then I'd want to be able to fiddle some more. But for the street, I don't even change rebound or preload in the front when riding a passenger. The shock gets a bunch more preload but only one click more rebound. Set it and forget it.

[pattonme]

@robsoup just buy a known entity with top-side controls - Andreani, Matris, NIX-22, AK20, with or without their respective updates. (I'll make you a deal on the the NIX-22 I have on the shelf) or buy the Maxton and send it to me or to tear apart and simulate/test their 'top side' config, see what I would propose to improve it, and then live happily ever after.
 
I believe the Maxton came to light only because the OP was in UK and wanted to try something local since international shipping for my Showa kit or the AK20 was perceived to be too much.
 
As a little side-job I'm rebuilding a set of '67 Velocette Thruxton forks. I'm hoping I can put modern cartridges into them. Otherwise I will just make a one-off piston and clean up some of the poorly machined bits.
 
 

[twotone]

 
 
 
I'm still running 10cSt fluid ion the compression side and the more normal 16cxSt on the "rebound"/base compression side. I have the left fork's "compression" adjuster still full out and the rebound 3 of 4 turns out. The front is now still fairly firm, but big bump compression is far better than it was straight from Andreani and that was far, far better than OE.
 

 
You still using 10cst fluid?
Adjusters 4 turns out, and fully opened?
 
Your shim stacks are way out man.
 
What Spring rate are you using?
OEM is .87 kg/mm, prolly still too heavy for a light rider.
 
 
 

[rick]

 
I'm still running 10cSt fluid ion the compression side and the more normal 16cxSt on the "rebound"/base compression side. I have the left fork's "compression" adjuster still full out and the rebound 3 of 4 turns out. The front is now still fairly firm, but big bump compression is far better than it was straight from Andreani and that was far, far better than OE.
 

You still using 10cst fluid? Adjusters 4 turns out, and fully opened?
 
Your shim stacks are way out man.
 
What Spring rate are you using?
OEM is .87 kg/mm, prolly still too heavy for a light rider.
 
 

Well, that's what winds up happening with the Andreani cartridges.  The lighter fluid was a trick I saw on both Triumph and FZ09 forums. You'll have to talk to Matt about the compression shim stacks as they are his.  
think he'll blame this more on the shape of the needles than the stack to the point that he's recommended I add another 0.5 or 1 turn of adjustment to the system. That's easy enough to do with how these cartridges are built. 
 
That the relative number is high compared to a Showa (rebound is at 1.5 on my Futura) set is not an issue to me as long as it works reasonably well. And that's pretty close. .
 
Spring rate was suppose to have been tailored to my weight and ride preference from the guy who was selling them at the time. But i think it is .8 something.  I checked sag and it's OK w/o dialing in any preload from the adjusters.
 
Before I swapped the C piston and put that base valve in the R side, I had a lot of stiction. With All-Balls seals, that's now pretty much gone. Next time I open it up - and i will to just to put clean fluid in - i might just go to those really slick SKF seals. 
 
 
 
    

[pattonme]

Your shim stacks are way out man.

 
Not necessarily - the C leg in a modified Andreani is biased toward a high speed comp setting. The needle has a very slight taper to it - 4 turns out and it's still impinging 1/2 the diameter of the hole. I'm sure there is room for improvement on the stack but also people like different degrees of firmness and trying to suss out feedback over email isn't always productive.

[rick]

Firmness - The sit up and beg ride position this bike puts us in a really comfy on long hauls, but it puts a lot of weight on butts instead of sharing with hands and legs - it's really easy to post up a bit to get one's arse off the seat when going over a big frost heave at speed on my Futura - not so much on this little bike. You just have to take it. I suspect a more forward ride position would take some firmness impressions away as more weight is placed on bars. Then that "firmness" just feels like good control.
 
I've never liked the angle of the OE bars - too flat imo, that puts my elbows up in the breeze. Don't really want the clip-on experience - just getting a bit old to assume the position and the 12" of hardware in my left hip reminds me every day - I think I'd like something between the OE bars and the Woodcraft w/1.5" in the up position. Some more experimenting for next season.
 
Meanwhile, the little FZ kept up reasonably well a couple weeks ago with a crowd of experienced track guys all riding bikes all on top line suspension bits and costing/making HP, 2-3x bigger, . Yeah, i had to do some WFO throttle thrashing and on a more open road they would have left me wondering where the f--- they went as the speeds probaby would have gotten stupid fast, but the bike is now pretty darn competent - even if I'm still pretty darn slow.
 
 
 
.

[twotone]

Yeah I agree that riding position has an influence
Nevertheless if you are going to open the fork again have a think about a softer setting, as pattonme will tell you lighter fluid is just a bandaid.
You're invested in this with time and $$$ so it would be good to achieve an equal return.

[rick]

Yeah I agree that riding position has an influence Nevertheless if you are going to open the fork again have a think about a softer setting, as pattonme will tell you lighter fluid is just a bandaid.
You're invested in this with time and $$$ so it would be good to achieve an equal return.

Possible that a lighter spring would help. I am pretty light weight on the scale of averages.  Not sure it's even possible to source though. I have that spring's kg number written down somewhere .  
Did about 75 miles today on mostly bumpy (smooth is actually harder to find around here sometimes) secondary and smaller roads. 90% of the time, the suspension is pretty darn good. It's that last 10% - over really big frost heaves or sloppy asphalt repairs at speed - where it could use some help. 
 
Really gotta do something with those bars. I have a lot of pressure on my thumbs as my elbows want to be in closer to my body and the angle of the bars gets in the way. I have a feeling I'd be happy with the angle of the Woodcraft bars. Just not sure I want the extra reach. Wonder if that entire unit could be spaced up some. 
 
 
 

[twotone]

Sonic springs will go down to .75, but I suspect the C piston may need an addition bleed oriface ie like oem have cross drill In one port.

[pattonme]

Rick's C piston already has a lot of bleed in it - the first shim is undersized, albeit a .15 instead of .1 so at slow shaft rates it doesn't completely give up, but on the big heaves it might be a touch much. Unless you have a 2-stage piston it's tough to serve 2 masters and get them both right. What I need is to go pay Rich a visit, ride his bike on his roads and then open up my bag of tricks and try a couple different configurations.
 
You let me know Rich, when you want the doctor to make his house call.
 

[rick]

Thanks for that - the doctor makes house calls, lol
 
Today's ride will be my last for a few weeks - have a wee vacation that'll keep me out of bike gear for a bit.
 
I need to let my buddy ride this thing and get his take. He's got far more experience with different set-ups/bikes - although sometimes i think it wouldn't matter if I shoed his wheels with red oak - he'd still go fast
 
I did some playing with the rebound side today and decided to increase the damping 1/4 turn at a pop from wherever it was. The front now really feels good - though the big hits are still not exactly plush. When I got home i counted turns in to see where it was - it started the day at 2.25 out. So at the end of the ride it was 1.5 turns out! Very Showa-like eh? Last fall with the unmodified kit, I'd been running the R side at 3 turns out! Clearly, it was way to of balance - or maybe it was just my impression as such.
 
I think that base compression valve you set up for me is just about perfect. I am curious to see how adding another turn to the C adjuster deals with the big hits. It might just do the trick. After seeing how dark the fluid was when I opened it up a couple weeks ago, I'm fully expecting that new piston to create some more grey stuff in that fluid
 
Anyway, i think it's now real close. Even the stroke is closer to what you'd expect. Think I picked up another 10 or 12mm of travel with these new compression valves - it's now about 95mm.
 
And people want more adjusters, lol.
 

[twotone]

Hey @Rick,
Just offering a view point here,
As riders interpretation can vary as to what really is going on in the forks.
 
Your feed back so far:
 
C leg.
10sct fluid
Bleed shim
Hi flow piston
Adj all out
95 mm usable travel? (This the odd man out)
Additional base valve in R leg.
Springs ~ .8
 
Based on this ^info the focus is to soften everything
The question is are you blowing through and getting to a hard spot too soon?
If so, I would consider higher visc fluid, and lower oil level, ie perhaps it needs to slow down in the mid velocity and still have ability to go beyond 95mm end.
Bear in mind on the SFF, a little change has a bigger effect (compared to DFF's)
Just a thought?

[rick]

Wish I could remember the number on the springs - it was mid 0.8 When I get back in there to put clean fluid in, I'll take some measurements on the springs.
 
Andreani calls for 120mm of air gap. This last time, I set it to 130mm, so I've already lowered the oil level.
 
The R leg has yer basic 16 cSt fluid.
 
Hmm, fluid dynamics - way over my head I'm afraid. Would have thought that base valve in the R leg would take care of the medium velocity stuff or is that just the slow speed stuff.
 
Yeah, travel used is getting limited - whether by fluid flow or something else like the spring being just too stiff for my weight. That spring might very well be an issue for my weight. I'd have to put some preload in to get sag right, but it would allow the wheel to move more freely w/o it moving me. My Futura's springs are .95s and that suspension is buttery smooth (preload/rebound only Showas), but that bike weighs a solid 100-120 lbs more. .85s might just be too much for me on this 400 lb bike.
 
I haven't really played with the compression adjuster since my 1st test ride with the unmodified Andreani. Just for grins, when I get back home I'll crank that in to see if that really makes things worse - or maybe not so much.
 
Anyway, all food for thought. Thanks for the input. I knew getting this right was gonna be a bit of a challenge. There's only so much these small diameter cartridges can do. Still, it's so much better than it was with the bits I tossed in the metal recycle bin, I'd not put it back.
 
 
 
.

[twotone]

No problem at all,
 
If I remember correctly Andeani carts have nylon rod/ spring buffers, these rob air/fluid space,
I would try 150mm gap, place a cable tie on a leg and monitor you fork travel in various conditions and also hard braking, and try higher visc in c leg if your mid speed is wanting. It is better to be bottoming out and then add the necessary amount of fluid to establish desired travel and safe reserve.