Shaving pounds to add performance, ? on component weight

[postman_pat]

At first when I read this I said no way, the fronts are tankers as well. I read another report of the front rotor weights, and apparently the 275 or 276mm dual rotors are the 4 lb rotors, the single disc 295/296mm that I am replacing is actually 5.2lbs! I'll be updating my weight stats again.


Although I am considering using the CAD drawings that a fellow member has made up to have a machinist make a rotor hub adapter and caliper adapter to use an 02 Yamaha rear rotor and Brembo caliper, I am still considering other options as the custom milling and CNC work will cost a small fortune. I did just stumble across this when looking for similar diameter rotors with the correct PCD and offset, wondering if they have the correct height of surface area for the old calipers, and if any newer GSX calipers will bolt to the old style GS brake bracket?:

Front Brake Disc for GSX 1100 F EF GS 1150 EF EF2 EG ES3 ESE ESG 83 86 88 93 97

Outside Diameter: 276mm Inside Diameter: 56mm
Bolt Hole Circumference: 78mm
Bolt Hole Qty: 6
Bolt Hole Size: 10.5mm
Thickness: 5mm
Offset: 21.5mm
Biding Discs will fit for:
SUZUKI GSX 1100 F FJ,FK,FL,FM,FN,FP 1988-1993
SUZUKI GSX 1100 F Katana FJ,FL,FM,FN,FR,FS 1988-1997
SUZUKI GS 1150 EF 1985
SUZUKI GS 1150 EF2 1985
SUZUKI GS 1150 EG 1986
SUZUKI GS 1150 ES3 1983
SUZUKI GS 1150 ESE 1984
SUZUKI GS 1150 ESF 1985
SUZUKI GS 1150 ESG 1986
SUZUKI GSX 1100 EF EFE,EFF,ESE 1984-1986

Round Front Brake Disc Rotor Suzuki GSX 1100 F 88-93 GS 1150 GSX 1100 EF 84-86


GSX 1100 F FJ,FK,FL,FM,FN,FP 1988-1993
GSX 1100 F Katana FJ,FL,FM,FN,FR,FS 1988-1997
GS 1150 EF 1985
GS 1150 EF2 1985
GS 1150 EG 1986
GS 1150 ES3 1983
GS 1150 ESE 1984
GS 1150 ESF 1985
GS 1150 ESG 1986
GSX 1100 EF EFE,EFF,ESE 1984-1986
GSX 1100 EF 1986-

Model: 140N-B
Disc Outer Diameter: 275 mm
Disc Inside Diameter: 56 mm
Disc Thickness: 5 mm
Number of Holes: 6
Bolt hole Diameter: 10.4 mm
Boltpattern Diameter: 78 mm
Offset: 21.5 mm

On my GS750 I have the following rear brake set-up:

1984 GS550E front right brake disc (260mm - 5mm thick) - bolts on to the standard GS750 rear wheel, same offset, and is MUCH lighter than the 296mm solid rotor of the GS750.

1982 GS650G rear brake caliper - a lighter design caliper than the original GS750 but develops the same stopping forces.

GS700E rear caliper mount - the GS700E had a 260mm rear disc hence this choice. Axle hole has to be bored out from 17mm to 20mm.

I can't give you any accurate figures for weight savings, but I would guess somewhere in the vicinity of 3lbs (?). I think that's not too bad for 3 parts, and I have no complaints about stopping power. Apart from the GS700 caliper mount, all these parts fit perfectly without modification.

BTW, get an RF900R rear axle to replace the GS750s, as I did. 20mm diam., hollow, and it's the perfect length to fit into a GS1100 swing-arm. Maybe another 0.5 lbs there as well.

Update: sorted through my parts bin for some weights. Those 4 parts I mentioned will give you a weight saving of 1.625kg (just over 3.5lbs)- and all off the un-sprung mass, which is good. Something for you to consider.

[Chuck78]

On my GS750 I have the following rear brake set-up:

1984 GS550E front right brake disc (260mm - 5mm thick) - bolts on to the standard GS750 rear wheel, same offset, and is MUCH lighter than the 296mm solid rotor of the GS750.

1982 GS650G rear brake caliper - a lighter design caliper than the original GS750 but develops the same stopping forces.

GS700E rear caliper mount - the GS700E had a 260mm rear disc hence this choice. Axle hole has to be bored out from 17mm to 20mm.

BTW, get an RF900R rear axle to replace the GS750s, as I did. 20mm diam., hollow, and it's the perfect length to fit into a GS1100 swing-arm. Maybe another 0.5 lbs there as well.

Those 4 parts I mentioned will give you a weight saving of just over 3.5lbs - and all off the un-sprung mass, which is good.

WOW, THANKS FOR THE TIPS! I had no idea that the 700E used a smaller diameter rear disc. I would imagine maybe a few other mid-80's bikes would use the same setup as well. I'll have to look at see what I can dig up!

I will look into that axle as well, as I am adding some unsprung weight with a much larger rear tire, and swapping steel rims for wider alloy rims doesn't cancel out the 110 to 140 tire weight gain, so the hollow axle will definitely help out A LOT as well. THANKS!

[postman_pat]

WOW, THANKS FOR THE TIPS! I had no idea that the 700E used a smaller diameter rear disc. I would imagine maybe a few other mid-80's bikes would use the same setup as well. I'll have to look at see what I can dig up!

I will look into that axle as well, as I am adding some unsprung weight with a much larger rear tire, and swapping steel rims for wider alloy rims doesn't cancel out the 110 to 140 tire weight gain, so the hollow axle will definitely help out A LOT as well. THANKS!

You're welcome.

While you're rummaging around there at the back wheel, why not machine up some new axle spacers from aluminum alloy. I recommend 2024 or any of the 7000-series alloys. They're widely available, and those grades have sufficient strength for this application. My K7 GSX-R1000 has aluminum spacers as factory standard fitment, so Suzuki thinks so too.

If you're going to replace all the rear axle spacers with aluminum then you should also consider replacing the large bearing on the sprocket drum. Standard fitment is a 25x62x17 - too heavy! I replaced mine with a 35x62x14, and then machined new spacers (from aluminum, of course) to suit the changed dimensions. New oil seal required as well - I went with a 45x62x7. There also exists a 40x62x12 bearing size as well, if you want to consider that.

Aluminum spacers and new bearing - easily over 0.5 lb there as well. Bit by bit, simple things like these add up to significant weight savings.

[Chuck78]

I don't know if I want to go as far as changing the bearing size, but I am unsure if my new rear hub is off of a GS 1150, if it is I need to have different axle spacers made anyway as they are offset 4mm from the rest of the spoked wheel hubs. I didn't realize those were made out of steel in stock form!

Are the rest of the GS 700 rear brake components not as light as the 2 that you selected?

The two links above for mid to late eighty's GS 1100 front rotors are quite costly new rotors but they are the floating rotor design are much lighter, usually 4mm thick, so that may be a viable alternative while still retaining my stock caliper hanger, although the GS 700 hanger and 550 front rotor would probably be much cheaper. I have always disliked how over powered the rear brake is as far as ease of locking up the rear wheel, but I was hoping that a 1mm smaller diameter GSXR rearset master cylinder would help desensitize that. Food for thought.

If I could find the earlier snowflake pattern rotor hub on that 550 rotor with the later 260mm diameter, it would match my CBR 900 RR front rotors that I am using for the Tokico Kawasaki Ninja twinpots front brake setup mod nicely, almost identical design!

[Chuck78]

Oh, and according to the EBC brakes catalog, the 85 gs700's and certain 83 gs750 models shared the same rotor specs, ebc # md3029 if memory serves me correct from looking it up last night. So those bikes should have the same caliper hanger as well, but the 750 model may have the correct diameter axle hole diameter for my bike already. I have not seen the snowflake pattern on that year rotor however. I will have to do more cross referencing tonight to check part numbers between the older and newer rotors.

Ebay EBC #md3029 rotor:
This item fits the following models:
1985Suzuki GS700E
1985Suzuki GS700ES
1983Suzuki GS750E
1983Suzuki GS750ES

[postman_pat]

Are the rest of the GS 700 rear brake components not as light as the 2 that you selected?

A standard GS700E rear brake rotor is 7mm thick. The GS550E's front rotor is 5mm thick. Although it is thinner, it works just as well. As for the caliper, they're both the same design, so you can substitute the GS700 caliper for my choice of the GS650G.

If I could find the earlier snowflake pattern rotor hub on that 550 rotor with the later 260mm diameter, it would match my CBR 900 RR front rotors that I am using for the Tokico Kawasaki Ninja twinpots front brake setup mod nicely, almost identical design!

That "snowflake" pattern disc does exist in that size, but from my personal experience I would strongly advise against using it. It is not rigid enough, and the two-piston caliper at the rear tends to deform it - which equals close to zero braking power. Those "snowflake" pattern discs are only suitable for use with rigid single-piston calipers.

The '84 GS550E has twin piston calipers at the front, so consequently, it has the more rigid two-piece design (VERY rigid aluminum centre riveted to a steel rotor). That's why you should use it on the rear, matched to the two-piston caliper.

If anybody has some experience with making a snowflake pattern work at the rear, I'd be eager to hear it, because it didn't work for me.

[Chuck78]

Okay, so I found that the 83-86 GS550ED/ESD/ES3/ES/EF/ESF/ESG used a really cool updated version of the Tokico rear caliper, with lightened up hanger bracket and presumably caliper. Unfortunately this combo only used 250mm rotors, which had a large PCD (bolt circle diameter) that bolted directly to the hub with zero offset. I was really wanting that style, but the only way seems to be to have a 16.5mm thick/offset 78mm PCD to 150mm PCD or so adapter made to bolt on a Kawasaki ZRX/GPZ rotor or the stock 250mm GS rear rotor, and I am not sure that the caliper and bracket will be in the correct offset location even, if using an adapter to make the appropriate 250mm GS rotor or the GPZ unit fit with the 21.5 or 22mm offset typical of the GS brakes.

So since the earlier Tokico calipers are really huge (banjo/line connection angles out the back upwards, newer style angles downward and the top photo bolts the banjo straight in the side) I will probably go with the more standard 81-83 GS650 etc Tokico rear caliper, but I am unsure and curious as to whether the two calipers will interchange as long as you stick with the correct hanger bracket for the rotor diameter you are using??? I'm tempted to buy the one in the top photo AND the one that I know will fit, and compare their dimensions and weight. Can anyone help me with any info that could save me the financial loss of buying both???

[limeex2]

shaving pounds to add performace

Postman_Pat, seems my last post didn't go through. What year gs750 do you own? I have a 79 gs1000 with a gs1100 swingarm. If its a 2 valver it sounds like a good set up. Chuck78, I seen that 550 brkt on ebay looks sweet but sounds like a lot of work.

[Chuck78]

INTERESTING... That 83-86 GS550E caliper is the same as 89-02 GS500 calipers, and the 03-? GS500 calipers look like an exact copy of them but minus the Tokico logo and add AJP logo. I am going to bet that all these calipers will bolt to the same hanger brackets. I am also going to bet that the GS550E/GS500 calipers are lighter than the caliper that I was previously hunting down. This with the 260mm front right rotor will be my rear brake setup now I am thinking!

[Chuck78]

Chuck78, I seen that 550 brkt on ebay looks sweet but sounds like a lot of work.

I think I will take one of the 260mm rotor brackets and drill/dremel it out to look like that one on the GS550E setup. Also going to give all the axle spacers to my machinist and have him duplicate them in 7000 series aluminum and go with one of those hollow axles that Pat pointed out. Holding my GS1100E axle setup, it weighs QUITE A LOT!

[postman_pat]

Postman_Pat, seems my last post didn't go through. What year gs750 do you own? I have a 79 gs1000 with a gs1100 swingarm. If its a 2 valver it sounds like a good set up. Chuck78, I seen that 550 brkt on ebay looks sweet but sounds like a lot of work.

Mine is a '78 model GS750.

Chuck78, I have all those parts you mentioned in my parts bin. I'll try to get a mock-up happening for you this weekend, and report on whether it works.

[Steve]

When you get near the end of your project, don't forget the finishing touch.


Fill the tires with HELIUM to take off that last 1/2 ounce.

.

[Chuck78]

Chuck78, I have all those parts you mentioned in my parts bin. I'll try to get a mock-up happening for you this weekend, and report on whether it works.

AWESOME! I think these calipers & either the 260mm front rotor or the 275 mm gsx1100 83-89?/91 gsxr front floating rotor will now turn into the go to setup for the best brakes to use on a stock GS rear wheel! The GS 500 calipers are very plentiful as well.

Please keep me posted as to your findings.

[John Kat]

I don't know if someone mentionned this but I believe it's possible to use a CBR 600 rotor on the rear wheel of a GS 1000.
Great weight saving for sure
To me the ultimate weight saving program is to use 1st generation GSXR 750/1100 wheels/disks/calipers.
Here are some weights I measured for the front wheel with tire but no disks:
GSXR 750 86/87 ( 18*2.5") 8.6 kg
GSXR 1100 89/90 ( 17*3.5") 9.8 kg
GS 1000 spoked wheel 9.9 kg
GS 1000 crossed spoke 10 kg
GS 1100 SD Katana 10.9 kg
The differences are even greater for the rear wheels.
The worst beeing the classic spoke wheel
No wonder most of the bikes competing in "classic" races use the 3 times 2 spoke wheels.
Here's the front wheel

[Chuck78]

Lightening up the rear brakes!

I don't know if someone mentionned this but I believe it's possible to use a CBR 600 rotor on the rear wheel of a GS 1000.

I spent a ton of time searching for CBR600 rotors, and the F2 rotors are the 276mm diameter that we'd need, but no offset and very large bolt circle. The F3 style are the 296mm rotors that work with the Salty_Monk twinpot mod.



These rotors are the only lightweight front rotors that are a direct fit onto the rears of our bikes that I can find:


fits 84-86 GS1150, 84-93 GSX1100. these are an exact fit, down to the 56mm center hub opening. 275mm 21.5mm offset 78mm pcd etc

to rehash, 83 GS750E_ and 85 GS700E_ front right rotors are a good lightweight 260mm swap for the rear rotor using the rear caliper hanger bracket from those two exact year/models, and the front right rotors off of 83-86 GS550E__ models are the same as well, but the rear rotor and caliper hanger are not compatible.


I also JUST found that these guys have several rotors of interest, including the exact EXACT fit snowflake style in 260mm AND 275mm:


They also have THIS exact fit (but 275.5mm?) lightweight floating rotor $beauty that I would love to have on mine... I am amazed at their selection of 3 or more rotors in the correct offset, PCD, EXACT hub opening diameter, etc. wow: