Horizons Unlimited - The HUBB

Horizons Unlimited - The HUBB (http://www.horizonsunlimited.com/hubb/)
-   BMW Tech (http://www.horizonsunlimited.com/hubb/bmw-tech/)
-   -   R80G/S front forks (http://www.horizonsunlimited.com/hubb/bmw-tech/r80g-s-front-forks-8209)

vincent danna 9 Apr 2005 01:20

R80G/S front forks
 
hello,
i saw the interesting messages on r80g/s rear shock.
i wonder how to make the r80g/s front forks better, if possible to change them ?
i ve heard we can put wp springs which is a good start, put r100gs front forks which are much better than the r80g/s original ones.
what else is possible ? wp ohlins etc ... ? any ideas, experience ?
cheers
happy trails ?



Grant Johnson 9 Apr 2005 01:28

You can significantly improve the stock forks with good springs, ND use 7.5 w quality fork oil.

Next step is R100GS forks, bolts straight in BUT you must also change the front wheel. Not a bad thing, you get a tubeless front tire then. Again use good springs, and oil, and you can also put an upgraded valving in, which makes a big difference I'm told - haven't tried it myself. I think it's a worthwhle upgrade. Note the stock G/S forks are weak, and have been known to snap just below the lower fork yoke. Exciting... http://www.horizonsunlimited.com/ubb/frown.gif
The stock fork legs should never be straightened if bent, just replaced.

Next step is WP or almost any dirt bike fork - BUT you then should lengthen the swing arm and rear shock to balance the ends. For long distance travel not worth it. For turning a G/S into a desert bike, that's the way HPN went with the BMW Dakar bikes. If that's what you want, go for it!

Timo 9 Apr 2005 01:38

Scroll down the previous posts, as there has been lots of discussion about improving the front forks. R100GS forks are an easy and decent upgrade: both Grant and I (and several others) have gone that route with good results.

Lots of different forks can be added, with varying amounts of work required to make them fit and operate properly. HPN fits bolt on WP forks that feature longer travel. I have also heard of someone who used a Showa fork off a Suzuki RM 125 that bolted on with minimal work (of course he had to change the brakes, and springs).

I have heard of poor results adding a long travel motorcross fork without increasing the rear suspension. HPN lengthens the rear swing arm/ drive shaft to achieve this (now you have a tall bike!).

Personally, I think the R100GS forks offer a decent upgrade that will(coupled with a good quality rear shock) raise the handling ability to the limits of the rest of the stock chassis. If you want to go further then you might want to think about sending your bike to HPN for a fully integrated upgrade to the frame and suspension.

As a word of advise, if you do look for a R100 fork, try to get the front wheel, axle, and brake setup as well. This makes it an easy bolt on otherwise you are in for lots of work converting the old wheel to the new forks.

Good luck!

Timo 9 Apr 2005 01:39

I think Grant and I must have been typing at the same time!

[This message has been edited by Timo (edited 08 April 2005).]

omar mansour 10 Apr 2005 05:10

thanks alot vencint fot your info
can you tell me do you still have the rear susp.for the g/s???
or any where i can buy used susp.in france??
thanks alot ,i did coverd most of the places in fracne on bike few times ,its great ,if no rains

vincent danna 10 Apr 2005 16:20

omar, i replied to you on the r80g/s rear shock forum

vincent danna 10 Apr 2005 16:31

Thanx for your replies.
I ve heard about changing oil (put a thicker one) and putting stronger springs like WP ones : that s what i did actually with my R100 GS PD when i was travelling around. And you do feel the difference.
Now about my R80G/S : the easiest would be to put R100 GS front forks, change oil and put stronger springs. What are the brands, models, lengths, diameters of the R100 GS and the R80G/S forks ?
A friend of mine (I met him in India : pictures on http://vincent.danna.free.fr/surlaro...decembre.html) is driving now a full HPN : he gave his R80G/S, ordered, waited for 2 years at HPN, he paid a big bill to get it transformed into a HPN: he has now a 300 mm Marzocchi M1 front forks, the rear swing arm was transformed (made longer).
Those top end forks, like Marzocchi, WP, Ohlins can be found second end quite cheap, when they come from KTM bikes or other cross/enduro bikes, which can be really exciting. But to put them on a R80G/S, as you wrote, there are a lot of modifications to be done (wheel, brakes, bearings, …) and when they are much longer than the original BMW forks, you need to make the spring arm longer to balance the bike and avoid damaging the gearbox, driveshaft and final drive. Also, I have the feeling that only a specialist or professional can do this.
I d like to know if there could be an alternative with short (like the original BMW length or just a bit longer) top end forks, like Marzocchi, WP, Ohlins : which models could be used ?
If anyone has done this before, any experience to share …
Thanx
Happy trails

NB : this friend with the HPN told me about other companies that can prepare/change your bike :
http://www.wuedo.de/menu_main/menu_main.html
http://www.witec-motorsport.de/
and SCHECK : but couldn t find the website

Bradd 1 Jun 2005 16:38

Im also very curious to hear about the above question, as here in Dubai I'll find motocross forks mutch easier than R100G/S forks. Id like a taller bike but am woried about the complications/cost of raising the rear.

vincent danna 1 Jun 2005 17:57

the best would be to find a bike already equiped :-)

otherwise, the most reasonable would be to put r100gs forks, but then you need to change the front wheel, the front brakes : so already pricy.

for the famous front forks like marzocchi (magnum model), ohlins (couldn t find which model ?)and wp (couldn t find which model ?) :
- amazingly pricy (something like 3 000 euros even more with wheel, brake, all the accessories !) unless you find a good second hand one
- because they are longer than the original, you need to make the swing arm / driveshaft longer, otherwise bike balance / driving problems, if you don t you damage the rear (final drive, driveshaft, gearbox).

so, for an old bike like a r80g/s (worth around 3 000 euros let's say), it s a lot of money for those improvements + then after you ll may want to improve all the "weak" rest : chassis, etc ...
it s like putting a ferrari engine in a citroen 2cv car :-)



BCK_973 5 Jun 2005 00:35

Vincent
I had in Germany a G/S 84 build.After a few months decided to upgrade my bike.Put a Acerbis 43l Tank,Whithe Power shock, and removed the useless fork!
Baugth a newer GS forkbridge and installed a DR 650 wheel and fork with the complete brake.
It was easy installed and worked perfect for many years.I sold the bike with 280.000!
The parts where used ones!
Bye
KH

vincent danna 5 Jun 2005 02:10

thanx for your post, good to hear about alternatives, adaptations, creativity :-)
other working doable experiences ?

Timo 11 Jun 2005 09:43

As I mentioned before, there was a post about this a year or so back....
I believe that someone had put a late model RM125/ RM250 (Showa?) inverted fork on a G/S. This was a bolt on modification, or close to it, with the major work being a change to heavier fork springs (due to the extra weight), and of course wheels and brake.

Again, I would follow Grant's suggestion that substantial front end and rear end modifications be done as a package. going to 300mm of travel on the front end while keeping the stock rear shock and swing arm setup could really upset your bikes handling. HPN sells a longer monolever for this setup.


[This message has been edited by Timo (edited 11 June 2005).]

vincent danna 11 Jun 2005 15:16

sorry, for being lazy and not searching in the past posts :-(
as usual, there s a lot on the hubb and it s worth doing a quick search before posting :-)

i found this, among other posts (20 all together) :
http://www.horizonsunlimited.com/ubb...ML/000057.html
http://www.horizonsunlimited.com/ubb...ML/000203.html
http://www.horizonsunlimited.com/ubb...ML/000158.html

definitely, if you put a 300 mm top end forks for on a r80g/s, you ll have a kind of "chopper" riding style, which is not what you want when travelling around especially, if you don t modify the rear (make the swing arm longer, put a longer shock absorber etc ...), hpn style.

would it make sense to put a 300 mm top end forks (if you find a cheap one!) and install it (if possible ?) with the same length as the r80g/s forks, meaning that the tubes of this 300 mm top end forks would top or go beyond the upper t plate (because they are much longer than the original ones) ?

also, is there a length difference between the r80g/s forks and a r100gs forks ?
for the moment, i ve read :
r80g/s : wheel axel diameter = 17mm, forks tubes diameter = 36 mm, brake disk diameter = 260 mm
r100gs : wheel axel diameter = 25mm, forks tubes diameter = 40 mm, brake disk diameter = 285 mm
therefore if you put a r100gs forks on a r80g/s, you need to change also the front wheel and the front brake system

thanx

vincent danna 11 Jun 2005 16:42

would it make sense to put a 300 mm top end forks (if you find a cheap one!) and install it (if possible ?) with the same length as the r80g/s forks, meaning that the tubes of this 300 mm top end forks would top or go beyond the upper t plate (because they are much longer than the original ones) ?

impossible : just took a look at the bike, there s not enough space because of the handlebars.

BCK_973 11 Jun 2005 23:47

To avoid the "Chopper" style i modified in a simple way the rear frame.As they come bolted to the main frame i bend a bit the upper plates where the bolts are located and added some 5 cm to the lower part of the frame and drilled new holes to the added material.In this way you correct this effect.
Bye
KH


All times are GMT +1. The time now is 01:37.


vB.Sponsors