Disc brake horror story question

[XL-erate]

Hi ya guys & gals!

Wanted to ask: I read a magazine test/review from quite some years back on the GS550, I think it was. They had some nice things to say but claimed that there was a real problem with applying front disc brake in a turn, that it caused front wheel to lift. Further comment as I recall was that the back disc was fairly ineffective, and overall the conclusion was lousy and dangerous brakes.

Somehow I have trouble believing that. Can't see how Suzuki would let such things out of the factory for starters. Also it seems to me, by the laws of physics, that applying any front brake on any vehicle in forward motion is going to cause downward force, not upward.

So, feedback? Thanks!

XL-erate

[Dogma]

Could that be an effect one of those anti-dive mechanisms that everyone hates?

[jknappsax]

front brake in a curve

If you apply the front brake too vigorously in a curve, the physics of the front wheel spinning would want to make the bike stand up more upright because of the gyroscopic effect, not cause the front wheel to lift off the ground. This could cause you to turn less and want to go straight, which in mid-curve, could cause you to go over the high side of the curve and off the road. All motorcycles exhibit this tendency, which is why you want to brake gently when in a curve, or stand the bike more upright if you can, then get on the front brake hard once more upright. The GS 550s don't do this more than other bikes, which is why a lot of people here set up 550s as cafe racers.

[Steve]

Could that be an effect one of those anti-dive mechanisms that everyone hates?

Any anti-dive system usually fitted to production bikes usually just increase the compression damping so the front of the bike does not pitch down as easily. There is no way that any of them will make the bike lift.

The only exception that I can think of would be Earle's leading link forks. When the brakes are applied with this system, they tend to rotate the leading link, which will then push up at the steering stem.

[Dogma]

The only exception that I can think of would be Earle's leading link forks. When the brakes are applied with this system, they tend to rotate the leading link, which will then push up at the steering stem.

Ok, been educated on the anti-dive... But wouldn't the leading link rig tend to lift the front of the bike, and not the wheel?

Anyhow, the article as quoted by XL-erate makes no sense to me. The only control I can see ever lifting the front wheel is the throttle. Perhaps "caused the front wheel to lift" is technical jargon I don't understand yet? Lifting the front wheel sounds to me like picking the wheel up off the pavement.

[Nessism]

I think the article is trying to say that the bike tends to stand up when leaned over in a corner if the brakes are applied. Not sure why the GS550 would do this any more than any other bike though.

From my experience the GS550 is a fine handling machine - far more so than an 850 which feels like the Queen Mary in comparison.

[Suzuki_Don]

I think this could be the article that is being spoken about as follows:

"The GS550's the safest way of going fast. Not only is the tough engine unlikely to seize up and cause a fight with the tarmac, but the chassis geometry instils the bike with fantastic stability. It never comes close to a speed wobble, doesn't even weave unless the suspension and bearings are really shot. Backing off the throttle in corners tightens up the line without inducing any back end traumas.
The only blight from the chassis occurs when the front discs are used with the GS banked into a slow speed turn. Then the bike flips back up to the vertical with a mind blowing violence that almost knocks the rider out of the saddle. The average 125 graduate will fall off. Avoidance takes merely a reliance on the back brake in such situations. Bear this in mind when going for a test ride."

Cheers
Don

[rkubik]

cool!

OK, now I'm going to have to try that out!

[Suzuki_Don]

OK, now I'm going to have to try that out!

Yeah, but you don't have a GS550 and it's a long way to come to have a loan of mine. HAHA

[XL-erate]

Thanks for the feedback, fellas, and thanks Don! That is indeed the article.

The thought of motoring through a slow speed turn as described, and then for whatever reason applying the brake only to have bike react so violently as to throw me off is a little hard to imagine!

To me, not from personal experience, the explanation by jknappsax is more understandable and plausible than the article's description.

[tkent02]

Sounds like BS to me...

[psyguy]

the article author must have done something silly on that bike that scared the s**t out of him and he must have felt better blaming it on the bike and writing about it than admitting his mistake :shock:

[earlfor]

I dont see how it is possible to cause the front wheel to rise off the pavement by applying front brake in a turn. I try not to be braking in turns, but I have used the front brake pretty darn aggressively in a turn when needed. All it does is to make the bike want to return to a more vertical position, but you can easily grab front brake and push the bike over even farther into the turn. Smaller, lighter bikes want to "pop" up quicker, but thats about all.
I think the guy is full of it. LOL

Earl

[Suzuki_Don]

Apparently it only applies to 550s, no other bikes were mentioned in the article.

[earlfor]

There are a couple of 550's for sale locally on Craigslist. Maybe I'll have to get one and overcook it into a turn so I can jump on the brakes for the experience. LOL

Earl

Apparently it only applies to 550s, no other bikes were mentioned in the article.