GS 1000 ST : the weave is back

[Kiwi Canuck]

Matched tires and grip levels

I have heard that the new grippier tires can cause the frame to flex more as they exert more stress and forces on the frame than the original tires, which could cause the symptoms described.

When I was racing the GS1000's we pretty much only played with tire pressures, shock and fork settings. Never really had an issue as I recall with the bike weaving but I didn't know any better, just rode it as hard as I needed to.
But I do remember spending a lot of time with the mechanics going over tire pressures and trying various combinations when we needed to gain some speed or it was an important race.

[Sandy]

It took me quite a while to dial in the handling on my '79 GS1000N. The setup I found that works for me is Progressive springs up front with no air, 15W fork oil, 100/90x19 Dunlop GT501 at 34 lbs. and a Tarozzi fork brace. The rear still has, believe it or not, the stock shocks (it's a low mileage survivor) with the spring set on firm, damping all the way up and a 120/90x18 GT501 at 38 lbs. The rear works great for solo riding but that's it, no adjustment left. I'm a believer that suspension set too stiff can be as big or bigger problem than suspension set too soft. Reason being if it's too stiff on these old bikes it transfers too much stress to the frame/swingarm and can induce flexing. Suspension has to be able to work to do it's job. That said the damping has to match the spring rate that has to match overall weight and riding style and also be balanced front to rear ...sigh. Can be a lot of fiddling, change one thing then you most liking have to revisit the rest. Case in point was when I installed my fork brace the bike felt better even at low speed but when I first pushed it hard it developed a fast oscillation that wasn't there before, turns out the front steering head bearing needed a minor retorque and all was well. You mentioned low speed weave. Generally low speed weave is a symptom of something not right in the rear and higher speed oscillation is something in the front. For an old bike it handles extremely well. It doesn't feel like it's on rails like the modern stuff but you have to be riding on the edge and encounter some good road irregularities to make it wiggle much. Sounds like you got it mostly sorted, hope it stays that way.

[bonanzadave]

Can be a lot of fiddling.

Im getting tired of fiddling.....

With everything mentioned in this thread and more my bike feels just like it did with old suspension and tires. Stock (35k miles) shocks and worn out Dunlop Elites. Now its got new Progressives and Avons, AllBalls in the head and new swing arm bearings and fork bushings. Same weave.

The head is adjusted just tight enough so it wont wander going slow. One click tighter and you can feel it at 5mph. Backing it off causes the high speed weave to go nearly tank slapper.

Im running the Avons at 35 psi cold and all suspension pre-load and dampening is about in the middle.

Strange .

[John Kat]

It took me quite a while to dial in the handling on my '79 GS1000N. The setup I found that works for me is Progressive springs up front with no air, 15W fork oil, 100/90x19 Dunlop GT501 at 34 lbs. and a Tarozzi fork brace. The rear still has, believe it or not, the stock shocks (it's a low mileage survivor) with the spring set on firm, damping all the way up and a 120/90x18 GT501 at 38 lbs. The rear works great for solo riding but that's it, no adjustment left. I'm a believer that suspension set too stiff can be as big or bigger problem than suspension set too soft. Reason being if it's too stiff on these old bikes it transfers too much stress to the frame/swingarm and can induce flexing. Suspension has to be able to work to do it's job. That said the damping has to match the spring rate that has to match overall weight and riding style and also be balanced front to rear ...sigh. Can be a lot of fiddling, change one thing then you most liking have to revisit the rest. Case in point was when I installed my fork brace the bike felt better even at low speed but when I first pushed it hard it developed a fast oscillation that wasn't there before, turns out the front steering head bearing needed a minor retorque and all was well. You mentioned low speed weave. Generally low speed weave is a symptom of something not right in the rear and higher speed oscillation is something in the front. For an old bike it handles extremely well. It doesn't feel like it's on rails like the modern stuff but you have to be riding on the edge and encounter some good road irregularities to make it wiggle much. Sounds like you got it mostly sorted, hope it stays that way.

Fully agree with what you say: the suspension must be allowed to do it's job.
I personally use the second preload at the rear with the 2nd damping level.
It suits my 73 kg weight nicely and keeps me away from the chiropractor as there are many poor roads around here
The GT 501s are also good tires that appear to have much stiffer sidewalls than the ContiGo. My GS 1000 EC is shod with a pair of these but in 130/90*17 at the rear. Never a hint of weave on that bike!

[John Kat]

I have heard that the new grippier tires can cause the frame to flex more as they exert more stress and forces on the frame than the original tires, which could cause the symptoms described.

When I was racing the GS1000's we pretty much only played with tire pressures, shock and fork settings. Never really had an issue as I recall with the bike weaving but I didn't know any better, just rode it as hard as I needed to.
But I do remember spending a lot of time with the mechanics going over tire pressures and trying various combinations when we needed to gain some speed or it was an important race.

You most probably used racing slicks with a much lower profile than the /90 used on the street bike.
John Ulrich wrote in a Cycle World test of the Yoshimura GS 1000 "When I rode the Suzuki at Riverside it wobbled fiercely, yet at Willow the handling was faultless"
A strange machine the GS 1000 S but what a pleasure when you get it right

[tatu]

Chris, what tyres and pressures are you running?

Tyres are Avon Roadriders
Front: 110-80-17 22psi
Rear: 150-70-17 20psi
Since I dropped the pressures the weave has gone and hasn't returned, though I have always been ready for it to come back but so far so good.

Mine was a very strange effect where if you were leaning into a turn and the road undulated such that the rear spring compressed more than the front the bike would lay down into the turn but come back up as the spring rebounded.

So high speed turns above 60-70 mph could be a little spooky at times. Below that there was not the same rear spring compression that seemed to manifest the feeling.

I theorised it was rear sidewall flex exceeding front side wall flex due to the banked turn while compressing the rear more.

I had all new bearings,alignments everything so it had to do with springs and tries and nothing else.

The weaves the S,es have develop even in a straight line, over the years a couple of really scary tank slappers with a couple of utter terrifiers when cranked over at flat chat.
I found out on the first day I ever rode my first 'S that trying to throttle through it makes it worse. When it got paniky bad the way I ironed it out was to sit bolt upright catch as much wind as possible and ease off the throttle till it was back under control, you could then wind it back open and not a hint of weave.
Thinking about it now, I have never experienced a weave two up.

[Kiwi Canuck]

Tyres are Avon Roadriders
Front: 110-80-17 22psi
Rear: 150-70-17 20psi
Since I dropped the pressures the weave has gone and hasn't returned, though I have always been ready for it to come back but so far so good.

Wow those pressures seem low, but if that's what works then who's to argue.

I am running the stock rims and went with stock 3.25 19 and 4.00 - 18 Avon Road Riders, they are 100% profile as you probably know.

I'm running 28 PSI front and 30 PSI rear, so I will try lowering them to see what changes it makes.
Mind you I don't ride fast enough these days to induce a big tank slapper or get into much trouble on the big corners.
Also I love my "S" too much to risk laying it down, I rather have chicken strips on my tires, than road rash on my Cooley.

[Frank Z.]

Ah yes, the nauseous weave wobble. Have had some relief from lower tyre pressures (thanks tatu), and went back with a fork brace. Still comes on when wringing her neck, esp. through the power band when the front end lightens. Will also get twitchy approaching 100mph... then i move my arse back about 6", light touch on the bars, and push it through. Never a rosy feeling, but working at the moment.

So, i've adopted two types of riding: around town high on the tank, and the Hailwood tuck for fast flights.

[Kiwi Canuck]

You most probably used racing slicks with a much lower profile than the /90 used on the street bike.
John Ulrich wrote in a Cycle World test of the Yoshimura GS 1000 "When I rode the Suzuki at Riverside it wobbled fiercely, yet at Willow the handling was faultless"
A strange machine the GS 1000 S but what a pleasure when you get it right

John, I was production racing on the "S" so we ran DOT tires and they were likely stock sizes, with 100% profile.



I do remember one time during open class practise, David Hiscock came flying by at the end of the front straight at Ruapuna on a GS1000S Yoshimura special and immediately got into a big tank slapper right beside me, that was pretty exciting for me and I'm sure he had big eyes for a while.

[John Kat]

John, I was production racing on the "S" so we ran DOT tires and they were likely stock sizes, with 100% profile.



I do remember one time during open class practise, David Hiscock came flying by at the end of the front straight at Ruapuna on a GS1000S Yoshimura special and immediately got into a big tank slapper right beside me, that was pretty exciting for me and I'm sure he had big eyes for a while.

It reminds me of me racing a Honda 750 Daytona in the 70's with Dunlop K81s
The bike was like a truck but when you unloaded the throttle going downhill in a 100 mph corner, it would start a slow weave until...you opened the throttle again to stabilize the machine
Jarno Saarinen was there in the GP category on a Yamaha TZ 350 and his machine also went into a belly dance in the same corner but...just a little faster