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Old 07-25-2010, 11:55 AM   #1
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F800GS - RXV Shiver'ed Fork Conversion

Hi,
So in reading this thread:
http://www.advrider.com/forums/showthread.php?t=524147

I decided to take on the fork conversion. Turns out -W- was thinking the same thing I was a while back except I had planned to use some KYB forks off a YZ250F. After the debacle of going to Aftershocks at TriValley Moto only to find out Phil and TriValley split ways the night before I showed up with my forks in hand, ugh.... I decided to go this route.

I am starting this thread because a few of us have been asking questions of -W- and this will give us our own thread to communicate in. I'm going to quote the important posts from the above thread here so we'll have the info in one easy to reference place.

The short version is this: You can easily convert the front forks on the BMW F800GS. I used a set of Marzocchi forks from an Aprilia RXV450.

Here is the order of things:
Find used forks with simialr diamater (marzocchi Shiver45 forks are the same as ours but a much upgraded version of their fork)
Take them apart
Take the bottom foot adjuster from the donor forks
Take it to a local machine shop along with the bottom part of each F800GS fork
The machine shop can machine the bottom of the stock forks to fit the donor bottom (compression) adjuster
Take the internals from the donor forks + the fork tubes from your stock forks + fork caps from the donor forks
Bring it to a local and good dirt bike or dualsport suspension shop (I used McCoy's Offroad in Carson City, NV)
They will put it together for you
Be sure the add a spacer to reduce the travel on the donor forks (info is below in this thread)
Put it back to gether
Put forks back on
Ride and smile a LOT!
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Old 07-25-2010, 11:57 AM   #2
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Here is where -w- started + a few posts along the way....

Quote:
Originally Posted by -W-
I just bought new set of these to be fitted to my F800GS when I have time to do the conversion at some point in the future (probably next fall). We will see how it goes, but basically should be relative easy thing to do when using parts of these ones and some parts of original beemer ones: http://www.marzocchi.co.uk/moto/45legsend.html

Biggest problem is to get 30mm more travel to the rear suspension also to keep the suspension in balance..
Quote:
Originally Posted by mousitsas
Contact hyperpro. They do custom things. You need a shock with 10mm (or so) longer suspension stroke than stock.
Quote:
Originally Posted by -W-
Both forks have been taken to peaces and it looks quite promising. Aluminum part of F800GS´s lower legs has to be machined to fit compression valve/adjuster of Shivers, but otherwise quite straight forward.

At the moment I have also decided not to put Shivers to F800GS as they are, but instead of that swap all the inner parts from Shivers to F800GS fork and make them as 230mm Shivers with full compression & rebound adjustments (bike was getting a bit too high to me with 265mm Shivers).

Currently I am traveling, so it it will take some time to proceed with this project, but I have already ordered new linear Öhlins springs (55Nm instead of original 44Nm) which I will put to these "Shivered" F800GS forks.
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Old 07-25-2010, 12:01 PM   #3
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Next....

Quote:
Originally Posted by -W-
Physical conversion done + first rides. Next things is to valve whole thing to mach the bike and use. But even at this moment... wow!







Stroke is at the moment 250mm (but I have also parts for 230mm stroke) and therefore forks are so high at the triples. I will lower them when the matching longer stroke rear shock is ready.

Springs are Öhlins linear springs (5.5N/mm) and they have currently 14-15mm preload which is almost half the preload original forks have (they have too much preload and too soft springs for my taste). And that is propably the thing why this setup is actually more plush/responsive than the original ones, even if the Shiver inner parts have still factory "motocross" valving.

And under hard braking.. No more huge nose dive and unstableness - completely different feeling & trust to bike than with the original fork. Still needs to be valved (and fine tune the oil level) by professional guy, but even at this point it feels really good... But you have to remember that I'm not expert in any way what comes to motorcycle forks & suspension things. I'm more used to set up downhill & mountain bike's suspension! ;) But I like it a lot and I quess that is good thing..?


And then the maching longer stroke rear shock..
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Old 07-25-2010, 12:02 PM   #4
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Quote:
Originally Posted by -W-
No you wouldn't. All necessarely parts straight from Marzocchi would cost at least 4xmore than whole forks from ebay. Only the one cardridge unit without base valve and top cap is 310e and you can buy whole new forks from ebay less than that.

Ps. and Marzocchi's spare parts policity sucks big time - they don't sell any individual parts to forks (except seals, sliders & shims). For example if your pistonring is damaged you have to buy whole cartridge unit to have the pistonring!

I actually did a bit of research on this and it is possible to order directly from Marzocchi USA. They get the parts from Italy and it would cost a lot. Good thing is replacement parts are available.
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Old 07-25-2010, 12:10 PM   #5
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I decided to do this conversion. Thanks -W-!!!!!!

The sought after forks are a pair of Marzocchi Shiver 45's. They are used on a few different dirt bikes including the Aprilia RXV 450(confirmed) & 550(maybe?), Husky WR250, and possibly GASGASS.

I found a set off an Aprilia RXV 450 that had the stiffer springs. The Aprilia has 3 spring options. Light, reg, stiff. Info is available out there on the interwebz on this. Anyway, I put up a post on a aprilia forum and had 3 set offered to me. One from Santa Cruz and two from Europe. Seems not too hard to find.

Quote:
Originally Posted by -W-


Aprilia RXV, BMW G450X, Husqvarna, GasGas, & Beta have these Shiver 45 forks at least. Remember to buy model which has also compression adjustment at the lower leg (some husky's don't have it even if the forks are called "Shivers")

That Shiver Factory 45 which I used was offered as an Marzocchi's "aftermarket racing fork" to some KTM, Honda and Yamaha models. I think it is basically same fork than normal Shiver 45. It just has that black special coating at the lower legs, but you don't do anything with those lower legs anyway..

My original idea was to swap the whole Shiver fork as it is to F8GS. Reason why I didn't do it was the thing that F8GS has taller upper legs than Shiver 45 has. This basically means that tubes are more inside of others in F8GS than they would be in Shiver 45 if you would use them (=more stiffer). Also if you would reduce the travel of Shiver 45's to something like 230-250mm the over all height of the fork would be too low for F8GS.
I have my forks apart and at the machinist now. I will be posting up pics and info once I get the quoted posts moved over. Anyway, once I get the feet machined locally the revalve work will be done by Ed McCoy at McCoy's off road center in Carson City, NV. It is close to me and he is a well recommneded shop. He does a lot of pro dirt bike riders forks and seems to know his stuff. Also a Race Tech Cetner for the NV/CA so good source for parts, etc.

I had the same question as -W- above. Will ask Ed when I drop off all the parts. I am planning to reduce the travel on my "RXV Shiver'd" forks to the stock travel of 230mm. Once I talk to ed we'll see which upper tubes I choose to use. My guess is that I will stick with the stock BMW's since they are basically the same. Love to have the silver ones.... pics later.


Quote:
Originally Posted by -W-
But remember that you need to have your "Shivered" the forks revalved by some professional since the damping isn't enough for the much stiffer springs that you will also need (and maybe some of you want to have really "plush" suspension damping too) . But the good thing is that they can be completely revalved and after that they should be really nice..

And I personally like the thing that after that you can also service and change the shims by your self as you like and that they are "conventional" cardridges without any gas pressure (=more durable and easier to service in my book).

I didn't take any pictures from fork internals when I did the modification, but I can take some when I am taking them apart for the revalving if needed.
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Old 07-25-2010, 12:12 PM   #6
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Quote:
Originally Posted by -W-
Forks have been now revalved by professional guy and.... jeesus they are sweet!


Shock dyno (not my fork at the picture like you see;).

Now you can blast through rock gardens with unbeleavable speed since front end tracks really well - doesn't bottom out or bounce from the rocks. Couldn't be more happier! Revalving made a huge different like was excpected - best euros ever used on a bike!

Currently I am running with 240mm stroke at the front (+10mm to normal) since I also took one spacer away from original rear shock (about +10mm more stroke there too - now 225mm). I will go back to 250mm stroke at the end when I have my new rear shock ready. I also swapped all the Shiver Factory 45 inner parts away and installed all the inner parts from Aprlia RXV's Shivers because one of the Factory 45's inner tubes was damaged (already from the factory production line) and it would have cost more than the whole Aprilia forks!

BUT the good thing with those RXV forks is that they have spring plates more lower than Factory 45's are having -> no need to cut the tube and relocate the spring plate like you have to do with the Factory 45's!

So in the end if you end up doing this conversion with the right parts (like RXV forks) it is REALLY easy and straight forward process:

1. Machine basevalve housings to lower legs.
2. Machine spacer to the damper rod. If you use RXV forks you will need 40mm spacer to get stock 230mm travel, 30mm spacer to have 240mm travel etc.
3. Put all the Shiver inner parts to you stock forks. No need to modify anything if you don't want to change the placement of bottom out piston which stock F800GS forks doesn't even have. And of course you fork is already having new bushes and seals;).
4. Put new springs and cut the spacers to get decired sag etc. I would recommend to use linear spring if you really want to have good suspension. I have Öhlins 55kg springs, 14mm of preload and 100mm of oil level/air chamber height at the moment.
5. Take the forks to some suspension guru who knows what they are doing. This part is vital to get these forks work like they should since you have much stiffer springs that the Shiver inner parts are tuned from the factory. Also valving of the stock Shivers can be a bit hars sometimes.
6. Enjoy of you new suspension!

...and next thing for you will be rear suspension because now the front is "too good" compared to that..
.
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Old 04-24-2011, 08:31 AM   #7
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I just got a PM on another forum with a set of RXV forks for if anyone is interested I can pass along the info... :-D
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Old 04-24-2011, 08:41 AM   #8
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Quote:
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I just got a PM on another forum with a set of RXV forks for if anyone is interested I can pass along the info... :-D
PM sent.
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Old 04-24-2011, 10:52 AM   #9
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PM sent.
PM replied and email sent. :-)
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Old 04-27-2011, 11:40 AM   #10
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Many thanks to Gangplank! I've got a set of RXV forks on the way and will do the conversion sometime in the coming weeks.
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Old 04-27-2011, 03:25 PM   #11
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Quote:
Originally Posted by jscottyk View Post
Many thanks to Gangplank! I've got a set of RXV forks on the way and will do the conversion sometime in the coming weeks.
-w- did the original work. I just followed his postings from another thread and put it all together.

20/20 hindsight if I had it to do over again I'd look for a set of RXV forks. If I couldn't find a set at a good price I'd just get a any set of 45mm-46mm forks off any 450 dirtbike. Doesn't matter what they look like or even if they are slightly bent.

Take both sets of forks apart, take the insides out and bring it all to a local machine shop. Have them machine the BMW fork bottoms to accept the bottom adjuster for the donar fork. Have them machine the top caps to match the BMW forks top cap threads OR make a collar that would fit it OR have them machine the BMW top caps themselves to mate up with the donor forks internal springs & adjustment screw. All of this should be easy for any machine shop. Cost?

Donor forks - $150-250
Machine bottom feet - $150 tops
Machine top cap - $75 maybe

Then I'd take the my newly machined forks to a good suspention shop like McCoy's Offroad or Superplush in SF and have them put it back together for me, tune the shim stacks to what they think will work well for my weight and riding style, respring if needed. Oh and shorten the travel if needed. They have to be longer not shorter travel wise to start....

Suspension work - $150
new springs if needed - $110

Total of about $600 for top notch forks. Makes good cents to me.
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Old 05-14-2011, 08:21 AM   #12
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Quote:
Originally Posted by jscottyk View Post
Many thanks to Gangplank! I've got a set of RXV forks on the way and will do the conversion sometime in the coming weeks.
How's it coming along?
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Old 05-24-2011, 01:43 PM   #13
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Giant Loop's BMW F800GS - Shivered?

Hey! I've been looking at many options for the forks on Giant Loop's F800GS - Ohlins cartridges, RaceTech, etc., etc., etc.

This solution looks great! For hard off-road riding, is the RXV with longer travel going to be the best solution?

If you hear about forks available PM me!
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Old 05-24-2011, 03:01 PM   #14
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Quote:
Originally Posted by OlafofOregon View Post
Hey! I've been looking at many options for the forks on Giant Loop's F800GS - Ohlins cartridges, RaceTech, etc., etc., etc.

This solution looks great! For hard off-road riding, is the RXV with longer travel going to be the best solution?

If you hear about forks available PM me!
For my conversion I'll be keeping the travel the same as stock. That's a detail to consider along with you rear setup and your suspension pro.

I've got a lead on a set of forks. Check your PM.
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Old 05-24-2011, 03:01 PM   #15
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forks

OlafofOregon,

If you are who I think you are, we met and talked at SSBMW on Saturday. I talked about riding with Dave last summer in Redmond. Too bad I didn't know you were interested in the Shiver forks. My forks have been with the suspension guy for a week now. I bought them on Cafehusky.com for $50.
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