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  #1  
Old 21 Sep 2003
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Suspension - airhead

The suspension on my R80GS Basic (150.000km) is not very god so I’m slowly planning to do something with it.

Front:
I have the standard Marzocchi setup. No modifications except thicker oil. The system has never been perfect, now it’s worse and it looks like the springs have worn out, it used to be much harder to compress the cover and put the “end-cover” on :-)
The springs get compressed a lot more then they used to do when I sit on the bike and when I break or hit a bump the bike dives a lot but it rarely bottoms out. It might sound strange but it feels like the springs compress suddenly, when I break they don’t compress in the beginning but suddenly they compress a lot.

I have found several options:

-Insert stiffer/progressive springs
I tried a bike like mine with springs from Wirth. It was a lot better and it’s cheap but I’m looking for something better.

-Change inserts and springs
HPN had a set where you can insert an adjustable insert which should give you the “advanced damping technology of the Marz Magnum”. Has anyone tried this setup?
The setup could be found on: http://www.hpn.de/pdf/hpn13.pdf

-Change the fork
I didn’t consider this in the start because it’s far to expensive but now it looks like I can get some kind of “cheap” setup from WP. The setup has a diameter of 50mm and I think it has a travel of 300mm. That probably means that they are a bit longer and they might need strengthening of the frame, views?
I’m sure it needs some fabrication to make them fit :-)

Rear:
I have a WP shock which will be overhauled and fitted with a stiffer spring. Any ideas how much stiffer it should be? Otherwise I think the shock will be okay.
Today the spring is adjusted to max but it still compress to much on a loaded bike.
I was thinking of shortening the strut that goes from the frame to the rear wheel drive It will straighten out the driveline and give maybe 10 mm in height and the propeller shaft might get a better chance to survive, it has done 150.000 km by now.
With the modifications above and a Pirelli MT21 I guess the height in the rear will be increased by 50 mm (to keep up the better front).

Any comments or better ideas?

The bike is used for everything, road-riding (with or without luggage), gravel-racing and offroad touring with luggage. Mostly solo-riding and I prefer to drive a bit sporty. I carry all my luggage in the rear (no tankbag) and a 33 liter tank (might be replaced with a bigger plastic-tank).
I will give priority to the offroad-touring use and I don’t want a bike which is to stiff.
The bike will probably be a bit higher, which looks necessary if you look at my bash-plates, but the main issue is to get a better suspension.

Thanks for reading all this stuff, and even more thanks if you comment it.
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Old 22 Sep 2003
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Ha! for a taste of how good your forks are try going back to the ones on the old G/S...... I'm in the process of putting your generation of fork on my older bike, and looking forward to the improvement!

But seriously, Given what you have said, I am inclined to think that there is something wrong with your fork. Have a look at your manual, or talk with a good machanic. I recall that Marzocchi forks do have some wear out parts in the dampening arrangement. There is mention in the Haynes manual that I have about re-setting the alignment of the tubes if stiffness is incountered. I would think they could do with new springs and a good rebuild - might make all the difference and will be far cheaper then your other options. I have not heard anything about the upgrade sold by HPN, but it could be an inexpensive improvement as well. Was the fork ever to your liking?

I would be careful about drastically raising the ride height of the forks without changing the rear. The older Monolevers can be extended to balance out the effects of a longer travel fork at the front, but yours is a Paralever so no go unless you want to swap. I have heard that just putting on a 300mm travel fork (without lowering it) changes the handling to the evil side, so tread carefully there. With HPN, many of their modifications are designed to work with each other in a complete package, and may not improve things on their own. Look around on the internet - others have gone the route you are condidering with varying success.

[This message has been edited by Timo (edited 22 September 2003).]
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Old 22 Sep 2003
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Hehe, I can understand that you would like to upgrade your suspension on your G/S to next generation, I’m hoping for an upgrade to a newer generation :-)

I have never been 100% satisfied with the suspension on my bike but it has been “okay”. Now I have to do something because it’s really bad and I’m not sure how much I should do. Changing the springs is easy, but when I tried a bike with other springs and a shorter mileage (only 30kkm) it was not that god as I hoped but it was much better than mine. Maybe some of the other parts need attention, my servicemanual (from BMW) only covers how to assemble and disassemble the fork (no tolerances or hints).
Anyway, if I have to change parts inside the fork it might cost as much as changing the inlet with a new inlet from HPN. That’s why I hoped someone had experience with the unit. I tried to find some information on internet but I couldn’t find anything.
The fork looks okay inside but I’m not sure what to look for, there is no obvious signs of wear but I guess after 150kkm (including a double trans-africa trip) it must be something…?

If I change to a fork with 300mm travel (I’ll only do it if I get a very good deal) I guess the new fork will be 75 mm longer (the old one has a travel of 225?). The rear will probably be 50mm higher when I change the rear spring, shorten the strut under the cardan and use MT21 (130/90-17). This probably means the difference will be 25 mm. If that is to bad it’s easy to lower them with 25mm or so. Hopefully I can lower them without decreasing the travel.
A higher front is not a big issue, because if the front is to high it will, as you say, changes the handling. It would be nice to get the bike as high in front as possible without disturbing the handling but to get a good suspension is what I’m looking for.
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Old 22 Sep 2003
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OK.....
My manual has the following to say about your forks
"apart from their greater travel and different appearance, the Marzocchi forks fitted to these models feature bushes which can be renewed separately to compensate for wear"
Looking at the diagram, there are bushes on the bottom of the dampener rods and at the top of the lower fork legs.
Your bike does have a considerable milage on it, so it would make sense that some work is required to get back to a stock condition. I would gamble that modern, stout(50mm) forks will be stiffer, offer more adjustment, and improve ride quality if set up in a way that does not change the steering geometry much. If you go with a longer travel fork and lower it's height by raising the tubes in the triple clamps, make sure that the tire cannot contact the rest of the bike in any way at maximum compression. Let us know how it goes either way.
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