Getting a GS 1000 S to handle

[John Kat]

I like your theory about the flexibility of the rear tire !
Like you I have a modified GS 1000 with GSX R 1100 K wheels and suspension and NO problem at all in handling.
In fact, your theory could be validated if the rate of weave could be correlated with the speed at which the rear wheel rotates.
In other words if the weave happens once per second at a given speed the wheel should go round one full turn in the same period.
Given a diameter of 65 cm the bike travels about 2 meters every second in the above example or 72 KM/H.
In my experience the weave develops typically above 120 km/h meaning that the weave occurs faster than once per second?
Why not?

[posplayr]

I like your theory about the flexibility of the rear tire !
Like you I have a modified GS 1000 with GSX R 1100 K wheels and suspension and NO problem at all in handling.
In fact, your theory could be validated if the rate of weave could be correlated with the speed at which the rear wheel rotates.
In other words if the weave happens once per second at a given speed the wheel should go round one full turn in the same period.
Given a diameter of 65 cm the bike travels about 2 meters every second in the above example or 72 KM/H.
In my experience the weave develops typically above 120 km/h meaning that the weave occurs faster than once per second?
Why not?

It could be somewhat speed related but more to do with the natural frequency of the rear spring mass system. As I recall with that particular road undulation, the weave was closer to every 2 seconds and was stable but unsettling.

Basically the rear was squatting more than the front. On a straight there would be no weave. But since I was banked, it would cause the roll motion in the same direction as the turn and in direct synchronism with the rear compression. Nothing really to do with the wheel motion.

The only thing I could figure to couple with the rear compression was rear wheel slip angle when banked.

[John Kat]

I just came back from yet another test ride!
This time I went back to the OEM rear shocks of my GS 1000 ST.
The configuration is 100% stock except the rear swingarm from an 1100 Katana and the rear wheel from a GS 1100 with the corresponding disk and caliper.
This is a major breakthrough in roadholding!
The bike feels much more planted and the wobbles have almost disappeared.
As the speeds are rising it's important to avoid "hanging" on the bars to keep the bike steady but apart from that I believe that for a 30 year old bike it's pretty good.
My personal preference would be to have a somewhat larger handlebar to hold the bike in "the just in case" situation...
Why is the roadholding better now?
The OEM springs are softer than the Koni's rated at 100/185 lbs/inch.
This leads to both a little more trail for increased stability and a better use of the shock absorber's travel that in turn puts less disruption on the front end.
Here's a picture of the set-up

[gmansyz]

Damping

Seems they works better as the springs are softer, yes? Maybe the Konis didn't have enough rebound damping? So the spring extends too quickly. This causes a lot of weaving. My '83 1100 Katana would do that. I was only 21 and weighed 12olbs. Heavier frinds would ride it without problems. I upped the rebound to the third and that solved it. The bolt on fairing to the forks changes loads fed into the frame. My adventure with this was a large, red, semi-clear windshield mounted to the 750 forks on my '81 GS750 with a 1200 engine. Right at 120, it would go into a weave then as I tried to power through it, it turned into a wobble and a nasty tank slapper. Luckily, I held on tight as it really did try to throw me off. It even bounced back and forth accross two lanes one the freeway until I slowed down. I think this was the Los Angeles freeway? I think running from LA to Santa Monica. Later, I found some funny, black "strings" hanging from the V&H collector. Figure out what those were?
Anyway, the load change dramatically and if raising the front end allows the weaving to disappear, then maybe the head angle is too steep for the combination or the trail is not enough. Maybe you could experiment with teh triple clamps from a gS11 with leading axle forks. This would give more trail. These old pencil forks are rather flexy as well. Even the 41mm GSXR. I would watch them on my Katana and see the axle moving up and down very little but moving front to back up to an inch. Think of what the frame does?
Okay, probably no helps but a little "fun".
Laters
G

[posplayr]

did you ever measure your sag before and after the shock change? Was there a length change?

http://www.thegsresources.com/_forum/showpost.php?p=1198228&postcount=38

[John Kat]

did you ever measure your sag before and after the shock change? Was there a length change?

Yes, the OEM spring on the 2nd level of preload (as tested) gave :
No load: 325 mm
Bike only: 315 mm
Bike+rider: 300 mm

The Koni spring at minimum preload gave:
No load: 325 mm
Bike only: 323 mm
Bike+rider: 308 mm

Clearly the Koni has too much preload while the initial travel is the same for both with the rider ( 73 kg) on board.
The Koni gets much harder thereafter as it is progressive...

[posplayr]

Yes, the OEM spring on the 2nd level of preload (as tested) gave :
No load: 325 mm
Bike only: 315 mm
Bike+rider: 300 mm

The Koni spring at minimum preload gave:
No load: 325 mm
Bike only: 323 mm
Bike+rider: 308 mm

Clearly the Koni has too much preload while the initial travel is the same for both with the rider ( 73 kg) on board.
The Koni gets much harder thereafter as it is progressive...

You are apparently way to stiff in the rear with the Koni shocks.
How about the front?

I think this is about balance between front and back so they front and rear act in unison. Part of what contributed to mine was an excessively stiff front. Yours is perhaps the opposite but also giving you undesirable effects.

Ohlins suggests:

-------------F-------------R------
Static-----15-30--------10-20----mm
Laden-----35-50--------25-40----mm

Your Koni's are:

-------------F-------------R------
Static-------????----------2-----mm
Laden-------????----------17-----mm

Your OEM springs seem just at the stiff extreme side of the Ohlins recommended range.

-------------F-------------R------
Static-------????----------10-----mm
Laden-------????----------25-----mm

[John Kat]

Ohlins suggests:

-------------F-------------R------
Static-----15-30--------10-20----mm
Laden-----35-50--------25-40----mm

I measured the front aswell and the results are:

Static------43----------10------mm
Laden------66-----------25------mm

If I decrese the preload to minimum at the rear I get

Static------43----------13------mm
Laden------66-----------25------mm

Clearly there is not enough air in the front suspension and the rear spring rate is too high for my weight.
What's amazing is that Cycle magazine tested the GS 1000 in March 78 and Cook Neilson used the hardest preset value for the rear shocks on the track with very good results.
I suppose the springs were upgraded after this test?
As I have some original GS 1000 EC shocks I compared them to the original GS 1000 ST shocks.
The wire diameter is the same at 7.5mm but the S version has 13 turns while the EC has only 12 turns so clearly Suzuki had already decided to soften the springs on the S model!

[posplayr]

I measured the front aswell and the results are:

Static------43----------10------mm
Laden------66-----------25------mm

If I decrese the preload to minimum at the rear I get

Static------43----------13------mm
Laden------66-----------25------mm

Clearly there is not enough air in the front suspension and the rear spring rate is too high for my weight.
What's amazing is that Cycle magazine tested the GS 1000 in March 78 and Cook Neilson used the hardest preset value for the rear shocks on the track with very good results.
I suppose the springs were upgraded after this test?
As I have some original GS 1000 EC shocks I compared them to the original GS 1000 ST shocks.
The wire diameter is the same at 7.5mm but the S version has 13 turns while the EC has only 12 turns so clearly Suzuki had already decided to soften the springs on the S model!

I was wondering about the front springs ; maybe if you get some progressive springs for the front (to stiffin it up), and lay off the preload with your OE shocks you will get into the proper range.

The other way is to cut off about 3"-5" and add a spacer if you want to go cheap.

[Sandy]

I was wondering about the front springs ; maybe if you get some progressive springs for the front (to stiffin it up), and lay off the preload with your OE shocks you will get into the proper range.

The other way is to cut off about 3"-5" and add a spacer if you want to go cheap.

I've been following this for a bit to see where it's going and thought I'd jump in. My bike is a '79 GS1000N and at one time had a factory "S" fairing, brackets, mirrors, etc. '79 "S" was merely cosmetic so it should be equivalent to yours. Right now it hasn't got the fairing anymore (I broke it) but with or without it the handling didn't change. My setup is progressive springs up front w/no air and 15W fork oil and STOCK rear shocks set usually on the stiffest setting and damping set at max. I quite often push the handling capabities of my bike to the extreme and other than the occasional wobble or weave (a fork brace fixed some of that) it handles just fine. Maybe this can be used as a baseline to get yours sorted. I think as long is the stock shocks haven't developed any leaks they should work fine. The stock front springs are known to be downright awful though.

[posplayr]

I've been following this for a bit to see where it's going and thought I'd jump in. My bike is a '79 GS1000N and at one time had a factory "S" fairing, brackets, mirrors, etc. '79 "S" was merely cosmetic so it should be equivalent to yours. Right now it hasn't got the fairing anymore (I broke it) but with or without it the handling didn't change. My setup is progressive springs up front w/no air and 15W fork oil and STOCK rear shocks set usually on the stiffest setting and damping set at max. I quite often push the handling capabities of my bike to the extreme and other than the occasional wobble or weave (a fork brace fixed some of that) it handles just fine. Maybe this can be used as a baseline to get yours sorted. I think as long is the stock shocks haven't developed any leaks they should work fine. The stock front springs are known to be downright awful though.

The front and rear wobble and weave are coupled and it is difficult for most mortals to soth out the cause and effects, so I think what I'm finding out is when all else fails measure the sag first and go from there.

[John Kat]

The front and rear wobble and weave are coupled and it is difficult for most mortals to soth out the cause and effects, so I think what I'm finding out is when all else fails measure the sag first and go from there.

This was also confirmed by my local dealer who works a lot on off road bikes.
"Many riders complain about front end wiggle when in fact it's their rear suspension that's reaching maximum extension"
In the meantime I've ordered RaceTech springs for the front fork...
Wait and see ?

[voivod]

What's amazing is that Cycle magazine tested the GS 1000 in March 78 and Cook Neilson used the hardest preset value for the rear shocks on the track with very good results.
I suppose the springs were upgraded after this test?

Racers are a different breed to road riders.
member reading about 2 different racers..1 set his bike up plush ...plenty of supension travel. 1 had his rock hard...both were at the top of the proffession.
The hard supension masked the fact that the stock frames of the time weren't stiff enough...so the frame itself flexed . This gave some suspension too.
The other guys frame was welded up...so was stiff as a stiff thing.
Neither liked the others bike
Also remember racers dont need to worry about potholes and sh*t roads ..or passengers or luggage.
Everyone rides different so some like stuff some dont. I like a wee bit loose...probably gives my brain less to think about ..lol

[John Kat]

I finally got my RaceTech front springs rated at .9kg/mm.
To get the sag in spec, I cut a 65 mm spacer and installed the springs with no further modification.
The sag ended at 28 mm somewhat less than the previous std setting with 1kg/cm2 that I was using.
The result is a bit of good news bad news mix.
The good news is that the front end feels very reassuring in small to medium speed bends by providing good feedback from the front tyre grip.
The bad news is that the weaving is back in some special cases like my favorite downhill sweeper at 140 to 150 km/h...
Next step is to increase the sag by cutting the spacer down to 55mm.
Here's a picture of the three springs used so far:
Standard GS 1000 EC with long spacer, standard GS 1000 ST with short spacer and RaceTech.

[bonanzadave]

Nice work ! Keep us posted on your results. I have not read this thread in a while and cant remember all you have tried to fix the weave. Ive tried numerous avenues with mixed results. None have corrected my weave. My last adventure was with a couple guys on Gixers. We all entered a big sweeping rt hand freeway-on-ramp wheel to wheel to wheel. As we entered the freeway we all accelerated up to triple digits. By the time I thought about shifting to 5th the Bike started to feel loose and the Gixers were long gone...