R100GS forks
 

Hello. Lots of questions today. On my '89R100GS/PD, the stock forks and brakes are, in my mind anyway, quite abysmal! Even with progressive springs, i find them acting horrible on gravel and washboard. I also feel i need to cary an ancor with me if i need to stop in time, and i haven't even loaded the bike yet!you can get valved spring sets from HPN and custom brakes and rotors from various sources, but there must be an easier way. Has anyone ever swaped the complete front end with,say a japanese heavy dirt-bike front-end? I know this can be tricky, with changes in fork-axel to steering head length greatly effecting the handling characteristics of the bike. Maybe you can fit a great set of forks with awesome brakes at the same time, killing 2 birds with 1 stone. Am i dreaming? I hate to settle with what i have right now.
Thanx!

Note: No birds were stoned in the posting of this message http://www.horizonsunlimited.com/ubb/wink.gif

Ron,

Follow the thread to a good link re: upgrading the GS brakes, although I think you may have already seen it(?)

http://www.advrider.com/forums/showt...6&page=2&pp=15

Heavier oil in the forks & a revalve kit i such a thing is available?

Steve

hi ron
glad to hear from you again if you want to go for a full on rally raid bike then 50 mm forks from hpn (www.hpn.de)
I would still get the hpn rear brake thu and then brace the frame don,t want it to snap like chris bright's in brazil or just slow down a bit

take care nobby

The brakes are not great but if they are really bad there has to be something wrong. It also depends on what tires you use on the bike. On my bike I use MT21 and there is no problem to lock the front wheel in 120 km/h, even when I drive with luggage. I’ve also used TKC80, Avon Gripster and it gives the same result. With a more street oriented tires it might be different.
This winter I changed to a metal braided hose and the feel really improved. Off course I still have to use force on the brakes but that’s not a problem as long as I know what’s happening and I know that you can lock the wheel if I have to.

When it comes to the forks I also rebuild them this winter. After a lot of thoughts I decided to keep the bike “low” and keep the original fork-legs, mainly because I didn’t want to lift the rear and stress the shaft. So I mounted inlets (the same as HPN sells but Q-tech are cheaper, BMW also sell them).
There is still a lot of snow on the gravel roads around here so I have mostly tested them on tarmac but they feel good. It should be interesting to test them further, to try other springs, adjust them and play with the oil-level.

Rebuilding the forks is not an easy task, and the first thing to do is to know how you would like the forks to handle. All springs are different and IMHO you are lucky if you buy something without research and it fits your need…. The same applies for the hydraulic.
If you have a PD tank it will probably come in conflict with a 50mm setup. The same goes for indicators, dashboard and so on…

IMHO it’s not necessary to strengthen the frame if you don’t change the suspension to much.

BTW a friend of mine has mounted a shortened Magnum-fork on his old G/S and increased the ride height a bit in the rear. It will be interesting to see how it works when he has finished the bike.

Hi Ron, If you do swap your forks I'd be interested in buying your old ones for a Project I have.I'm in Revelstoke B.C.
Cheers, Peter

P.S.Have you checked out UK Gsers site, there is some good info there.

Hello. Thanx for all the responces, you're all a great help http://www.horizonsunlimited.com/ubb/smile.gifAliBaba, what are the inlets that you talk about??... After long consideration, which also means a lack of "disposible income" i've decided to become cheap and creative. I'll keep the forks, but re-build them and toy around until i'm happy. As for the brakes, i'm used to doing stoppies with 2 fingers on my R-6, so my expectations will have to lighten-up!I'm looking for a 2-3 pot left caliper from some racebike with radial brakes on e-bay, something i can adapt to the fork with an aluminum plate. can anyone tell me where i can get a good 320mm. front disk for less than $300us???

Mr. Ron,
As to the Brakes, I am mid-way into the modification you are speaking of:
I just had an aluminium adapter machined to go from the stock R100GS hub to a 320mm GSXR Rotor (without the stock, dished rotor carrier). I picked the rotor up at a bike wrecker for $115, it was hardly used. So far so good, but I haven't finished the project yet, so still lots to work out. I haven't settled on an appropriate caliper yet either - I'm trying to find a nice 4-pot unit that still has dust seals on the pistons, otherwise I might just stick with the stock caliper. It can be done, but requires lots of messing about. MAP engineering makes a really nice setup which I have heard good things about. I would have gone that route if I wasn't missing the rotor carrier already.

Dude, we should meet for a beer! Between the two of us we should come up with a more than adequate braking system for the GS. Just got back tonight from a road-trip to Prince George and back. I never thought of machining an adapter plate for the rotor also...Brilliant! Why not try the GSX/R caliper also? I read in another forum about a guy who connected the calliper to the master cyl., placing it on the rotor and clamping it on. Tie the brake lever back, then make a template of the adapter plate to the fork.


Gotta go, hockey game's on!!

I'd be happy to meet up and show you what i have done so far. not a bad Idea about the caliper location - I haven't figured that out yet. Another bridge to cross! Originally I had intended to make my own adapter but time and tools (mainly tools!) did not permit. I ended up contacting a couple of biker/ machinists in Victoria who did a fine job based on what I told them. They still have the computer drawings if you like...... I paid them $300 total for their end and am please with the quality.

I do get to Vancouver once a week or so. send me an email off list and I will give you my number. Happy to talk over a beer some evening.

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Ron,

I think you're refering to a posting of mine on the ADR Riders site a couple of weeks ago?

Works every time for me. The only time I've spent money re-mounting calipers is to get 4 spacers machined on a lathe. I now have my own lathe.

The other way, that looks more profesional IMHO, is to use a 1"+ thick of aluminium & make a 3 dimensional carrier that requires no spacers but this requires a decent mill & operator, hence it can be expensive.

Re: template. I use thick cardboard (lever arch files are good) & make the template in two halves. One half bolted to the fork leg & the other half bolted to the caliper. Once I'm happy with the positioning of all parts, I tape or staple the two halves together. resulting in the two sets of mounting holes in alignment with each other. I trim the template to shape & make a temporary carrier out of thin aluminium sheet, just to confirm alignment. Once I'm doubly satisfied, I make the final version out of 1/2" thick ally sheet. No special tools used, only a good jigsaw, a drill (bench drill if possible) & files & sandpaper. Just need to get the spacers made after that.

Steve

Hmmm...I have access to a full fabricating shop and even some 1 1/2" billet titanium lying around. I'm shure that would make an adequate caliper adapter! Great idea Steve, and yes, i now recall it was your post i saw in another forum. My question for you is have you fully tested your adapter with spacers? It sounds like there could be lots of room for movement, flex and viberation when using spacers instead of milling the off-set from one solid piece. Also, in regard to using a sport-bike type calliper,these are mounted radially( behind the fork-leg). I would have to use the left one from a dual-calliper system and turn it around to mount it to the right front fork-leg on the GS. When the brakes are applied on radial systems, the callipers are under compression, applying the load directly to the fork-leg. When i flip the calliper around, the calliper is under tension when the brakes are applied. A calliper with very heavy castings and lots of material around the bolt-holes must be chosen so that it isn't torn apart under heavy braking (Verrrryyy Baaaddd!!) I post this only in theory not having tried this yet, what are your thoughts?

I always mount the caliper behind the fork legs because the bikes I've worked on have been designed that way.

I covered over 40,000 miles on my DR600 fitted with an FZR600 f/wheel, FZR1000 320mm disc & a Nissin 4-pot caliper from a GSX-R. There may well be a tiny degree of flex when using spacers but none that I've noticed. My pads wear evenly & don't jam in the caliper. I've nevernoticed any vibration. I also fitted ISR calipers to my GSX-R & 1100EFE calipers to a GSX750EF for a friend.

One thing to note that I learned from my DR experience: Where possible, use the matching caliper for the disc you're using. On my DR set up, I have to grind a slight bevel on the bottom of the pad material so that it clears the disc mounting buttons. At least check in advance that that the pad clears the buttons when aligned with the top edge of the disc, not a huge hurdle but a potentail problem you can eliminate at the design stage. I used a GSX-R caliper because that's what I had & I did not want to use the Sumitomo caliper as fitted to FZR's as they have no dust seals fitted.

Machining from a large billet is the way to go if you have the facilities (& skill - big power tools take no prisoners, as we say here in Oxford.....) It may be an idea to make a mock up first, using spacers etc to ensure alighment etc before proceeding with the final version?

Good luck

Steve

and what about the master cilinder, do you need to change it too with a four pistons caliper?

I'd stick with the current m/cylinder for the moment. Although the stock GS caliper only has two pistons, they're two large pistons opposed to 4 small ones.

I tried a 5/8" FZR1000 m/cyl on my DR & it was crap, no lever travel at all, like squeezing a piece of wood. Now use a Honda 1/2" m/cyl & it provides more travel & a lot more feel.

It's all about comparative surface areas of the respective pistons in the m/cylinder & the caliper itself.

I have manuals for both the GSX-R & the GS. I'll dig out the respective caliper piston sizes later & post them here for you to work on.

Steve

Be prepared to change master cylinders, although you MAY not need to.

When I installed a 4 piston caliper on my G/S, I had to change masters. Then when I installed a 6 piston caliper, I had to change again.

As Steve notes, if it's wrong it can be "wooden" - or if wrong the other way the lever just comes into the bar.

BMW has masters available in 1mm increments from I believe 11 to 16 mm. I now have 4 of them...

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Grant Johnson

Seek, and ye shall find.
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