Single v double front discs

[Guest]

in 78/79 suzuki offered the gs 1000 and the gs 750 with either single (wire wheels) or double ( mag wheels) front disc brake versions.
Wonder if at that time any of the cycle magazines did a stoping length test comparing the 2 different models.
I think the most important factors for hard hard braking are.
1. Operator skill
2.tire grip/ road condition
3. Brake condition
4. Number of front discs

i know that-when I used to rode race 80-83 (I was a squid) everything was the front brake.
i think that for riding on the road, skill and anticipation of other people?s manuvers are indispensable.
Jim

 

[Steve]

I don't remember if there were any specific comparisons, but I think the single discs were slightly larger diameter, giving them a bit more leverage. The smaller double discs do promise a bit more braking power, but they are also heavier, which means more unsprung weight. The less weight there is in a wheel assembly, the better it can react to bumps and dips in the road, giving a better ride and better control. It's always a compromise.

.

 

[Chuck78]

the single disc 295mm is barely enough to stop a 500lb GS750 with a fairly aggressive rider blazing through some great twisties... add fresh modern pads and stainless line and it would probably be acceptable, but you will really also need to add a Tarozzi or similar fork brace, as the single disc especially is prone to twisting the stock fork legs and 15mm axle. The fork brace really helps with the spindly axles and adds more rigidity to the front end in general for aggressive cornering.
Dual discs can benefit from the fork brace as well, but the single disc is exceptionally bad with fork slider twist.

As far as stopping power, the duals with good modern pads and stainless lines will be perfectly acceptable in terms of stopping power, but WOW are those old rotors HEAVY!!!!

The single disc twinpot mod with a 310mm rotor and early EX500 caliper (I think the early ones are the correct side, the later ones are on the opposite side as the GS, or possibly I have that backwards) and stainless lines and new pads and a GS500, bandit 400, or EX500 master cylinder will REALLY improve your braking, but still really needs a fork brace added. That is all the brakes the average rider of average weight on an average weight bike needs, but for really aggressive riding,mountain riding, big rugged hills riding, the dual disc shines as they fade less. The twinpot mod uses substantially lighter rotors. I wouldn't be surprised if the dual disc setup of that weighs the same as the stock single disc setup...

 

[Nessism]

As I recall Cycle noted that the wire wheel and single disc GS1000 was a fair bit lighter than the 1000E. I don't see anything wrong with going that way unless you are planning to ride the bike hard in which place the dual discs will help with fade and overall power.

 

[GSXR7ED]

Before I did MC/Brake rebuild the single disc did not have my confidence. After the upgrade to braided line and a serious cleaning, the single disc was much more responsive. The fork brace adds that ridgidity and more confidence in my bike.


Ed

 

[Old Colt]

Way back in time when I was young and my GS550 was new, I road raced it. The bike was well prepped but still had the original single front brake, the round puck caliper that the '79 came with.
On the race track the bike would carry the rear wheel in the air every turn for 18 minutes at which point the pads were taperworn to the point the lever was interfering with the throttle control.
At this point the turn in style changed and using some rear brake and I would rotate the bike to scrub off speed on corner entry.
Interesting thing with this bike, it has a custom made 5.5 gallon tank which would allow full hard riding for two + hours, one refill for a 4 hour endurance.
Issue was, we only had 18 min of front brake so we would strategize if we would use the brake hard early or late in the event.
We spent allot less time in the pits which offset our weaker turn entry through much of a longer race, we were always competitive.

So to me the early single disc front brake is plenty fine for road or sporting use. With today's grippy tires one should be able to carry the rear wheel as we always did with race rubber on.
I do not feel the original dual brake is any true improvement over the single other than the pads will last longer, Not sure how many people actually wear out brake pads, BUT every modern brake is allot better in most every way.

 

[limeex2]

Imo, being an ex racer also you would never be happy with a single disc even if it was up graded. After my up grade with HH pads and some break-in time, I was surprised on how well they work. Ive went to standard race tricks, reducing weight, braces ect. Wire wheels and HD spokes work and look great. I used a 18" front wheel and turn in was much better and high speed stability is not an issue. Ex race bikes on the street are a blast and unlike the current cafe craze you wont see many of them. Im running my old race bike and have basically added 1 mirror, a license plate and lights that work. Glad I never sold it.

How do you like your GS550ES? My race buddy had one and in the production class he kicked GPZ's, 550 Seca's arses. Very under rated bike at that time. GPZ's got all the attention

 

[Old Colt]

For me my only complaint with single disc was your turn in was different each direction. My recent trackdays have been on a BMW 450X, impressively fast little bike, easily runs with the 750s and litre bikes. Those guys do not ride into turns with the rear wheel up, is it just me? I can not say I noticed the standup or drop in we had under braking decades ago with the single disc on it, Might just be me though, probably not as sensitive now being in my 60s.

The 550ES was impressive early in it's life. The rear shock faded away to early and I never replaced it back then. I guess with starting a business I let life get in the way so my toys got put away.
Recently I have been doing the swap on the ES which I like the way it is coming out but have not yet fired the 1052 motor up. Just reworked the rear suspension shock and linkage and feel I might have it close to right now.

 

[limeex2]

Rear wheel up as in Stopies? Isn't it kinda hard to turn on 1 wheel? A 1052 GSXR motor in a 550 would be a riot.

 

[Chuck78]

As I recall Cycle noted that the wire wheel and single disc GS1000 was a fair bit lighter than the 1000E. I don't see anything wrong with going that way unless you are planning to ride the bike hard in which place the dual discs will help with fade and overall power.

Yes, the difference is around 34lbs! Heavier mags, twice as much weight in front brakes...

Another reason why I always try and push to run all my bikes with wire spoke wheels (primarily it was due to the classic looks).

A budget build coming up may have a 17x2.50 rear GS mag, however... and I've been contemplating the CBR600F2/F3 mags and a similar version on some SV650's, as they are the only modern mags that I have seen that look remotely acceptable on a vintage bike. The CBR250 wheels that I have spotted internationally on eBay for non-us models would be the ultimate though, as they aren't as substantially wide and don't require a 170 or 180 rear tire. 130 to 160 is the maximum for a GS depending on which model we are talking about.

 

[Old Colt]

Rear wheel up as in Stopies? Isn't it kinda hard to turn on 1 wheel? A 1052 GSXR motor in a 550 would be a riot.

Yes but the rear is not up high as in a show stopie, the tire is just skimming to a noticeable amount up. Being that one feathers off the brake as you turn in, the rear starts to come around but sets down during the initial rotation.
Since I have very rarely ever used the clutch once I have gotten into 2nd gear or above having the rear up makes the downshifts much easier especially when the brake lever is starting to clamp onto you throttle fingers where you are restricted from getting the blip in for the gear change.

I am looking forward to ride this 1052 swap but I am flat out with customer work till late July and not able to get much time in on my toys. So lord knows when it will run.