Front brake Options for 1983 R80G/S

**Cameron** · #1 31 Jul 2004

Has anyone fitted late model 4piston sportbike brakes (nissin,tokico,etc) to the front of an 81-84 r80g/s...

Prices start at $900 U.S. and up for new caliper and rotor that still have to be machined to fit...seems a bit much. Thought some used sportbike brakes might be more practical. Cheers, Peter

**Grant Johnson** · #2 31 Jul 2004

Cameron, Timo and I were just looking at sport bike calipers for our R100GS front ends, and the R80G/S is actually easier to mount a sport bike caliper on. Basically find something that looks about right, get a big disk off a sportbike, machine an adapter for the disk to wheel, and make a plate to mount the caliper on.

I had a 4 piston Performance Machine caliper on my G/S forks, worked well. Easy install.

You will have to change the master cylinder as well. 14 mm works perfectly on my 6 piston caliper, probably good on most 4 piston as well.

I just happen to have a Tokico six piston laying around...

Note that it's 81-87 G/S then GS and a different front end.

------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

**Grant Johnson** · #3 31 Jul 2004

btw, I have a spare 15mm master cylinder which I had on the PM 4 piston brake you're welcome to borrow to try.

------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

**Mr. Ron** · #4 31 Jul 2004

Hello.
This topic has been brought-up a few times now and there's some great info in the hub. I thought i might mention, if you go with a sport-bike type calliper, you will most likely need the left one. This may sound odd at first, but remember the calipers on sport-bikes are mounted behind the fork. Yours will be mounted ahead of the fork. If you take the left caliper and swing it 180 degrees you can easily mount it on the right side ahead of your fork. i purchased a left front caliper from a 2001 Yamaha R1 and will be mounting it in the near future. Do a search and you'll come up with some great info

Good luck!!

**Grant Johnson** · #5 31 Jul 2004

Sorry Ron - on the G/S - the caliper is behind the leg, so Cameron needs a regular right hand caliper.

The G/S has a completely different front end to the GS.

Note on yours, (a GS with no /) if the pistons are different in size front to rear (called a differential caliper) then you will be running the differential backwards and you will get significant uneven pad wear - depending on how much difference there is in the bore size of the pistons.

The purpose of the differential is to even out pad wear - if you mount it backwards...

------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

[This message has been edited by Grant Johnson (edited 31 July 2004).]

**Mr. Ron** · #6 31 Jul 2004

OOPS!
Thanx for pointing that out Grant. I'll have to do more research before offering advice. I see your point with the diferential caliper, fortunately my pistons are all the same size so this shouldn't be a problem.
Thanx and good luck!

**Timo** · #7 2 Aug 2004

Mr Ron,

Are you certain that your R1 caliper is evenly sized? I have looked at quite a few and all the 4 piston calipers that I have seen are differential. You have to measure the pistons carefully, as often the outside housing is the same size, but bored to different diameter inside (i.e. 32mm/34mm). I was planning the same thing, but have gone back to the stock 48mm twin piston Brembo for lack of options (modern convention is to mount behind the legs, making our R100 forks unique). I think perhaps that the answer is to be found in a larger rotor and perhaps more aggressive pads.

Interesting to note, when I was looking into the various sizes of calipers (measuring piston surface area only) the 48mm was larger then the 4 piston Nissin, which was larger then the 6 piston Tokico! Of course, the pad length and surface area was greater for the muli-piston calipers, but mechanical leverage was similar.

Hopefully done the mounting tomorrow - I'll let you know how it works in a few weeks when the new Master cylinder arrives.

**Cameron** · #8 2 Aug 2004

Thanks Guys, I knew Grant had a few different brake setups on his bike. Those PM calipers are very nice and also expensive...
Thanks also for the info about differential brakes, I did not reailize that the pots could be different sizes.
I would like to try a 4 piston caliper first, for size and weight reasons.
Have also been told that the old Harley guys used to cut the mounting flanges off the fork leg and tig weld them back on where needed to fit different calipers...

The next step is to get to the wreckers and see what might fit...Cheers, Peter

**Grant Johnson** · #9 2 Aug 2004

Cutting and rewelding the mounting was probably ok on the old Harleys - in the days when the fork leg was a half inch thick, perhaps even steel - on modern super thin alloy legs a rock hit can total the leg. I'd expect severe problems with welding to a modern leg (even ones as relatively non-

modern as the R100GS)

Feel free to try and let me know how it goes.

------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

nb · #10 3 Aug 2004

Hi Ron,

An interesting alternative is to put a left caliper with a new/usable disk. I used a left Brembo caliper from a 1981 police R80 bike with a R60/7 disk. I've to put a suplement in the wheel hub, because the disk worked with an old Brembo or ATE caliper (I can't remember).
The twins disks works perfectly, real cheaper modification and a real noticiable brake power increase.

Saludos desde Argentina.
Nicolas.

nb · #11 3 Aug 2004

sorry, I forgot one thing: I change the master cilinder to 16mm.

saludos.
nicolas

**Timo** · #12 22 Sep 2004

Having just completed attaching a 320mm GSXR rotor onto my R100GS forks, I would say that the stock caliper is just fine in this configuration - no need to also mount a 4 or 6 piston caliper. I think it is easier to achieve better braking with a larger rotor then with more pad area. At first glance, it seems easy to just bolt on a different caliper. However, what you gain in length, you will lose some in width of the pad anyway as most multi-piston calipers as designed for a narrower running surface.

The 48mm brembo caliper I have on my GS front end is cutting into the rotor stems almost to the bobbins, as it was designed for a larger rotor surface area. Going the other way (say - 6 piston caliper on stock rotor) will likely mean you are not using all of the surface area of the rotor.

Lots to measure and think about!

[This message has been edited by Timo (edited 21 September 2004).]

**Mr. Ron** · #13 26 Sep 2004

Hello. I've noticed on E-Bay Tokico 6-piston Calipers from GSX-R 1000-1300 bikes are selling cheap! The last one, a lefty, for $68USD. I'm not sure but they apear to NOT be diferential calipers, unlike the R-1 caliper i purchased earlier

Anyone out there know for sure?

**Timo** · #14 27 Sep 2004

A quick phone call/ visit to your local Japanese parts house should reveal the answer to that one. Inquire about a caliper rebuild kit for the bike in question, and it should note different piston sizes. I'd be very surprised if it is not differential, but hey, you don't know til you research. I think stock parts off of modern sportbikes tend to be cheap, as lots of owners are 'upgrading' to keep their bike current in the performance world.

**Mr. Ron** · #15 27 Sep 2004

Hello. Good point...these types of bikes also have a very high crash rate compared to others, lots of parts available. So Timo, could you explain how you mated the GSX-R rotor to the carrier. Maybe a photo, could save a lot of typing. Your idea seems like the most logical aproach, after all i'm guessing in most places it would be easier to find parts from a modern Japanese racebike than an old airhead GS!