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One Less Harley 02-09-2009 03:05 PM

320mm Brake upgrade for G/S
OK after hashing out whether to ad another disc, or some other method of upgrading brake I decided to go w/ a 320mm brake upgrade. I think stock is 260mm. As Of now I cannot comment on the improvements as you can see I have no front tire.

This uses the stock caliper and just relocates the calipers outbound a bit, comes with a spacer for the rotor and needed bolt to mount the caliper and disc. I got this from Seinbenrock. It is suggested to get another brake line but the old one will work.

One thing I don't like and has nothing to do w/ function is that the bracket which mounts to the fork needs to have the mounting bolts recessed into the bracket. I may have this done later.

johno 02-09-2009 06:53 PM

Thats a strange looking disc:huh
Looks like a floater, but its not.

Should definately work better though.

One Less Harley 02-10-2009 04:10 PM

It's a solid disc which have been laser cut at a few locations to take care of heat expansion and probably help keep it from warping.

I had the aluminum countersunk for the mounting bolts. A much neater look.

woodgrain 02-10-2009 07:14 PM

How much for the Siebenrock kit?


One Less Harley 02-11-2009 05:39 AM

USD Cost- $311.98 plus $41.40 shipping from Germany.

Probably cheaper to get someone to make another bracket for a four pot caliper, but might have to change brake lines and possibly the MC. The stock brakes aren't that bad w/ standard tank and unloaded...not great but adequate.

StephenB 02-11-2009 09:24 AM

Or, for a lot less, you can use a 2000 or so K1200R (re-badged Brembo) 4-pot caliper (34/32mm) on a stock disc with great stopping power:

Use a left caliper with bracket for the G/S location behind the fork leg.

England-Kev 02-11-2009 10:09 AM

Are there any options for four potting an ST front end?

Caddy82rats 02-12-2009 03:29 AM

The ST use the same calipier so the 4 pots conversion would work

Gimmeslack 02-12-2009 03:37 AM

Anybody have a link to more info on this mod? e.g. does stock bracket work? Shims...? Does master cyl need to be re-thought? etc...


Originally Posted by StephenB
Or, for a lot less, you can use a 2000 or so K1200R (re-badged Brembo) 4-pot caliper (34/32mm) on a stock disc with great stopping power:

Use a left caliper with bracket for the G/S location behind the fork leg.

StephenB 02-12-2009 04:34 AM

On a stock GS you only have to shave a bit (4mm) off the mounting brackets of the caliper, otherwise it is plug 'n play. I made no changes to the m/c. I think mine is stock GS 12mm.

Dunno about doing the mod on a G/S but I assume you need a custom bracket.

One Less Harley 02-12-2009 03:26 PM

Took the bike out for a test ride w/ the 320mm rotor, don't know what pads are on the stock caliper, but getting the front wheel to chatter and lock up is not a problem now. First ride and I like it so far. Nice upgrade w/ no fuss on installation.

One Less Harley 02-12-2009 03:28 PM

For stephnb's conversion notice it's for a GS no a G/S, but the principles of the conversion are the same.

jellycow 02-13-2009 11:29 AM

I've had the same HE disk on my former r100gs. Combined it with a 4 pot calliper. The shear stoppingpower (well, for 2v-alikes :lol3) Used the left side calliper from a r100r and just had to take about 5,5mm off the spacer. Easy fix, good result.
Now, by the time the disk on my G/S is worn and the 2 reserves after that I'll have saved enough money to buy the HE for G/S and so it'll be done.

BTW: it is just about floating, the lasercuts are in such locations that there is some room for the disk to move, just as on a really floating disk.

Solo Lobo 02-13-2009 06:15 PM


Originally Posted by Caddy82rats
The ST use the same calipier so the 4 pots conversion would work

Nope, the BMW 4-piston caliper does not work on a G/S nor ST.... I can tell you that for sure.

Boxerworks sells a machined adapter to do this mod, but the caliper ends up almost below the wheel and looks to be in a bad place for off-road riding.

One Less Harley 02-13-2009 07:10 PM

Solo, that conversion looks hoaky as hell....hope it's not your bike. Yeah I knew the four pot wasn't plug and play even with shaving the caliper as the spacing for the mounts are different.

I really am enjoying the 320 disc, it's been fun today hearing the front tire squeal and locking it up. Never could do on the R1150RS. If I could only get the wobble taken care of, still fighting with that, along with a wheel hop, dyan beads didn't fix that. I'll try and get the wheel spin ballanced tomorrow. Gotta fix the wheel hop and wobble. But Not ready for buying a rear shock, cann't affoard it right now.

I've got some calipers coming from an early RT (117mm spacing for the mounting bolts, like the G/S) and will still look closer at the spacing, but I'm thinking even w/ the shallow rotors some spacers will need to be made, then have to make sure the calipers don't hit the spokes. Carrier spacers wouldn't be any big deal to make.

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