F800GS Bitubo Fork Kit

[bxr140]

Originally Posted by M N B

Why make a high end, adjustable cartridge and leave out the most critical part of suspension.

Because spring rate and damping rate are dependent...and since the bitubo kit has fixed damping, there's really no point in changing the spring rate.

That kit is going to work (...well, one hopes) for the designed rider weight (~180-200 pounds), but outside that range its probably not worth spending the dosh.

Originally Posted by The Griz

If you want a system that is exactly tuned to you, then you'll be paying $2000 for a custom design instead of $525 for this Bitubo kit.

I'm not exactly sure what you're trying to say, but:

A. Having a suspension shop rework your forks will not cost $2000. Porbably more like $200, and they will be "exactly tuned to you", and will perform nearly as well as anything else for the vast majority of riders.

B. Buying full cartridge internals and having them reworked will not cost $2000. Probably more like $500-600. Potentially the best option for "exactly tuned to you" if you're tiny or huge, but not worth it if you're in the bell curve of rider weights--the bitubo kit is likely the best choice.

C. A swap to any of the various modern MX forks that will slide into the GS's triple clamps will not cost $2000. "Exactly tuned to you" plus more travel, with fairly minor cutomization. Probably $1000 when all is said and done.

D. I don't think you actually meant it, but your statement implies that the bitubo kit is "exactly tuned to you"...which is only the case if you happen to fit the weight range to which they are tuned.

[M N B]

Originally Posted by Desert Dave

What critical part is left out?

The ability to choose the spring rate in the spring. LIke you can do with any Ohlins (for $1200) or Wilbers (for $700 - $1200).

Originally Posted by bxr140

"exactly tuned to you"...which is only the case if you happen to fit the weight range to which they are tuned.

Ding, ding! I don't see the point in getting the bitubo if it only works well for someone in the weight range the bike was designed for.

Seems a better deal to buy proper springs and have them installed and setup by a competent shop. Unless you're 185lbs +/-

[DockingPilot]

The cartdriges in this kit at nitrogeon filled. It uses oil and the gas to dampen I guess. I did refer to my weight and ride style when ordering them dont know if that mattered though. i dont know if you guys know Drew Smith, but he is a multi time ISDE rider and mager of the team. He also has a suspension shop. He will not use progressive springs feeling they throw off the bike or make it suspend differently at different times in the stroke. I dont kmow if there is any truth to that though. But that is his opinion and he will not install them.
I might go ahead and install these tomorrow and it seems very easy according to the instructions. Ill post all pics if I do.

[DockingPilot]

Dave,
Well, I guess I was expecting worse like on my Husky. Man, that was like having no front suspension ! And I was trying to be positive and not trash the stock forks so much. But yea, they are harsh, no doubt and can be improved. I think the oil gets locked initally and cant move, causing that harshness. But Im no expert here on that.

Originally Posted by Desert Dave

Really? Everytime I do that I hit the front so hard I think I'm going to bend a rim.

How about some more info on the enduro....did I miss the ride report?

[DockingPilot]

Also Dave, it wasnt an enduro ! GOD FORBID. Those days are over for me now and the 800 wouldnt make it 3 miles into any half assed enduro ! I went to a Dual Sport / Advenutre event, riding a bit of both course. 230 miles worth over 2 days. The terrain was rocky, mountainous and muddy at times. The bike performed admirbly I must say. I was very happy with it indeed. These fork units should make me even more happy.

[johngil]

Originally Posted by The Griz

No, and they are linear rate springs. But that is also why they have a preload adjustment. To suit a wide range of weights.

I have run straight rate and progressive springs on my bikes. The valving is what is important and that it works w/ the springs. So straight rate doesn't bother me. If a spring rate can't be specified, I won't order these cartridges.
After racing KTM's in the desert and having my suspension sprung and valved to my liking, I am picky.
Adjustable pre load on the forks means nothing to me. Pre load won't cure a poor setup.

I believe the next option will be w/ trailtrick and his Marzocchi internals. I'm pretty sure I'll get compression and rebound clickers. I need to give him a call.

[bxr140]

Originally Posted by DockingPilot

He will not use progressive springs feeling they throw off the bike or make it suspend differently at different times in the stroke. I dont kmow if there is any truth to that though.

There's a lot of truth to that. Most suspension tuners will not use progressive rate springs--they're really just a holdover from old school damping rod designs, where it was difficult if not impossible to get something to damp correctly at all speeds. In the olden days it was near impossible to get the damping right, so you had to make due changing the only thing that could really be changed.

Not using them on more modern designs (not that the GS is THAT much more modern in design ) comes back to the fact that damping and spring rates are dependent. The range of spring rate is simply too large with progressive springs to achieve proper damping across the full range of fork speeds.

[DockingPilot]

Thanks for the info bxr. Yea, Drew Smith is a prety well known guy in the enduro / ISDE curcuit. He owns Works Enduro Rider as well.
Anyway, I dont pretend to know the first thing on the mechanics of suspension. "Just make it work for me and Ill ride the heck out of it, just dont ask me how it works or to adjust it"
Here's what I dont get here with these and maybe someone can explain it. The cartdridges are gas filled, yet I will still pour the Silkilene 2 wt. fork oil in the tubes. Whats the oil do ? Just lubricate or are they also helping to dampen ?

[Desert Dave]

Originally Posted by M N B

The ability to choose the spring rate in the spring.

O.k, I did misread your post.

But then I did accuse DockingPilot of riding an enduro when he clearly said it was a dualsport event, only a few posts later.

Maybe I got to much thin air in the high country yesterday Sorry guys.



So back on topic, the kit consists of linear springs which I agree are the way to go when matched with dampning valves, and if rider weight/style is taken into account (as DockingPilot noted) sounds like each kit is built to order, or at least within a range which puts these guys right back there with any quality builder. I would like to get that verified for certain, I suppose that'll be easy when I order.

C'mon DP , install them, we're all waiting

[DockingPilot]

Im installing them now and will take pics.
As far as custom spring rates, I can tell you my answer was somewhat vague (Italian), so Im a little suspect, but I am 180lbs fully geared up, so I should be within the normal spec.

[The Griz]

Originally Posted by DockingPilot

Im installing them now and will take pics.
As far as custom spring rates, I can tell you my answer was somewhat vague (Italian), so Im a little suspect, but I am 180lbs fully geared up, so I should be within the normal spec.

Yep, given you're within weight design spec of the bike, I'd say you're in for a pleasant surprise with these Bitubo springs that come with this kit! "The hydraulic unit is in a sealed and nitrogen pressurised cartridge, with oversize pistons and laminar packs studied for the perfect control of damping." <---I trust this to be true when you're within weight spec of 187lbs +\- a few.

[DockingPilot]

INSTALLED AND TESTED........sorta.

These are stupid easy to install fellas and the directions are spot on. The only blank you'll draw is tightening the cartdrige units to the sliders. They of course will spin. Use (lightly) an impact wrench. Done.

You can see there is a great difference between the way the stock Zokes dampen and the gas charged Bitubos.

Stock


And here they are installed



Honestly, you do not need a pictorial to install these. Its rediculously easy.
Now the ride results. Let me 1st say I only had time for a half hour on the bike. I was able to ride dirt road and abandoned railbed as well as pavement. So my opinion is still in a holding pattern. And my opinion is just that, mine, and may be worth to you what you paid for it. But I have ridden offroad all my life and owned many different bikes. Opps, almost forgot, Drew Smith measure the old and new springs for those guys wondering about spring rate.
Stock rate 4.8
Bitubo rate 6.0
Yea, that seems strong, but Drew has reworked some big 1200 GS bikes and they have been sprung with 7 something-8.0 springs. So I kept an open mind before going out on it.
In a nutshell: Huge, significant difference. Do you guys know when your riding and you see a pothole in the pavement ot a rock embedded in the soil and you know your going to hit it in a second and you sorta brace for the feeling you'll get from the stock forks ? Or sometimes under your helmet you go "ah" when you hit it ? Thats gone.
I rode over heaved pavement sections, and hunted potholes. I was amazed that I no longer felt them at all. On the dirt roads, the embeded rocks were sucked up with no steering upset. I went down a local abandoned railbed that has a small layer of RR gravel sitting on top of hardpan. At 40-50mph, if I closed my eyes, you could have told me I was on pavement and I wouldnt have the difference. Also, no more huge brake dive. Just normal like it should be.
Again, this is prelimanary. I still need to ride her for a week to see how well I like them. But, so far they are 80% better than stock. And for the price, and the fact you can install them in your own garage without sending your forks away, they just may be the cats ass.

[PackMule]

[jeffchri]

DockingPilot - do you have stock rear shocks? And do you ride it with high preload?

Where did you set the preload on the Bitubos?

[DockingPilot]

I havent tried even setting them yet as my Hyper Pro shock is here but not installed yet. The, Ill set the sag.