TOO Much Wallow in sweepers

[posplayr]

I'm going to do that this afternoon, i have the steps saved as a favorite.

The front isn't too stiff and has good movement, it's actually a little softer that i like.

The front end is stable, and the reason for the 20wt oil was that I had the stock springs and it was WAY TOO soft and had too much sag.

I Thought you had changed to progresssive springs up front. Do that if you have not.

I checked the tire chart for the tire I just ordered and the manufacturer states that the tire will work fine on rims from 3" to 4" my rim is 3.75" So this shouldn't be a problem.

Wow if your rim is 3.75" then go with that new tire.

I've already raised the forks in the trees by 10MM, should i go more ?

I was thinking the opposite, if you lower the rear axle, then lowering the front triple woudl keep the bike at the same rake.

So, to me the most logical and simple answer was the tire, of course when i got the dunlops i didn't have anyway to check what size rims these would properly work on, the front size is stock.

I was concerned because you need to get your springs right and doing some sag measurements is first on the list.

Is there a chance I might need to cut my springs and install a spacer ?

Yes you can spacer adds preload, if you wack off 3-4" then that increases spring rate.

Thats just what i plan to do, I'll post my result's tonight for the sag measurements front and rear to see what you think.

The lower profile tire will be a good idea if your wheel is that wide already. I just would not want you to mask the real problems (side wall stiffness improvement) until you can solve that. Then the stiffer tire will make it even better.

I will do all of the other stuff you have listed above before going to the different tire, I will see if i can cancel the order before it ships out today.

Good as mentioned the tire would work well once you sort your springs out.

 

[gixerbike1]

forks springs

forks springs

Pos,

I did install the new springs, i put the 20wt oil in when i replaced the seals and i still had the old springs at the time.

At that time the front end was extremely soft, now it's better but still too soft for me, if i cut the springs and add spacers will that stiffen the front end up some more ?

I cancelled the new tire and i'm going to check the sag measurements after work to see where i am.

I'll let you know what i get once i get them.

Then i'll try whatever you advise me to once i post the sag measurements.

Tommy

 

[gixerbike1]

gixxers.? Where??

gixxers.? Where??

Are you riding this GS after owning a modern sportbike? Just wondered (with your handle and sig graphic)...they do feel different, esp. whilst cornering. The older GSs while not unsafe, are nowhere as confidence-inspiring as the modern bikes, and may well feel 'flexy' when pushed in the corners, compared to a Gixxer....an altogether animal, in terms of the tires, chassis, and geometry.
Tony.

Indeed i am, I've owned 3 gixxer 750's a CBR600 a KZ700 and a CX500 and now a GS650E.

I'm diverse :lol:

 

[salty_monk]

I tried higher tyre pressures for a while but find it better on the freeway with slightly softer than 36-42. (I am only 160lb ish).

I ride with about 32-36 now if it's just me on there.

Dan

 

[posplayr]

Indeed i am, I've owned 3 gixxer 750's a CBR600 a KZ700 and a CX500 and now a GS650E.

I'm diverse :lol:

Well then don't expect any miraculous changes. The differences between radial and bias ply tiers is very significant.

I'd say my on my GS750EX which is basically stock but with Progressives and fork brace up front, with Hagon shock in the rear with Avons all around I dont like to do any heavy cornering beyond maybe 60 mph. It runs fine at 85 mph on the straights.

With my 83 1100ED, with stock 37mm forks, racetech emulators, progressive and fork brace on front with Ohlins piggybacks on the rear and Sprort Demons all around heavy corner at above 85 mph are a little scary, goes as high as you want to go straight till the wind knocks you off.

With 18" GSXR conversion 43mm forks (braces, progressive springs, emulators) and radials 170/60-18 back, 110/80-18 front (Dunlop/Avons modern stuff) with SU-145's now much more stable at 85-95 cornering. A little wollering going on and that is likely frame flex starting to have an effect.

I'm now closer to a modern bike but not there when you compare modern 180/55-17 and 120/70-17 with a real stiff frame.

Anyway, with a GS you can get a thrill at 1/2, 2/3 or 3/4 speed of a modern bike depending upon what you do to it.

 

[Billy Ricks]

Hate to burst your bubble but I really doubt you have a 3.75" wheel. You might have a 3.75" wide tire as stock, but the bike I see when I click on your link isn't wearing a 3.75" wheel. Wheel really means rim when you hear us talk wheels. If you look around the rim portion of the wheel you'll see the width cast into the wheel. I'm betting yours is 2.5" or less. My '85 700 only had a 2.5" wheel stock. The last 1150's only had a 3.5" wheel. Beyond 2.5" wheels they get bigger in .5" increments from what I've seen.

Going lower profile only makes the problem worse when running wider than stock tires. The sidewall gets pinched even more since it's shorter than with a higher profile tire. You're probably starting to screw up the seating area of the bead too. The more you pinch a tire the weirder the handling gets.

 

[posplayr]

Hate to burst your bubble but I really doubt you have a 3.75" wheel. You might have a 3.75" wide tire as stock, but the bike I see when I click on your link isn't wearing a 3.75" wheel. Wheel really means rim when you hear us talk wheels. If you look around the rim portion of the wheel you'll see the width cast into the wheel. I'm betting yours is 2.5" or less. My '85 700 only had a 2.%" wheel stock. The last 1150's only had a 3.5" wheel. Beyond 2.5" wheels they get bigger in .5" increments from what I've seen.

Going lower profile only makes the problem worse when running wider than stock tires. The sidewall gets pinched even more since it's shorter than with a higher profile tire. You're probably starting to screw up the seating area of the bead too. The more you pinch a tire the weirder the handling gets.

Thanks Billy, I was wondering about a 3.5" wide GS wheel. Anyway if you watch the video in the link you will see some sport bikes riding, but at 4:23-4:30 min into the video you will see a big full dresser trying to take some fast corners and you can see the side wall flex creating wobbling motion when he hits some slight bumps.

heavy weight on the rear with bumps causes sidewall flex induced wobble like what is seen in the video. The rear tire is slipping out a little due to higher than normal side slip angle and when it does the bike does a little lowside maneuver till the tires grabs again and sucks under the ride doing a small highside.

My theory is if the side wall did not flex as much the tire would just bite the road, when the extra weight comes down in back due to the bump, the tire would not slip out.

Of course the springs should be setup so that the front and rear stay level through this type of bump and so the exhibit more similar slip patterns and there is so lowside tendency (at least not as much).

I'm guessing any combination of mismatch would result in the same thing, but soft rear is probably worse.

http://www.thegsresources.com/_forum/showpost.php?p=1196489&postcount=1

 

[Billy Ricks]

Yours is good advice Jim as far as setting up sag to match at both ends. That's something he can do now to see how it helps, which it will. I think the tire needs to be correct before too much other assessment takes place. Just looking at the photo of his bike I'd say it's a 2.5" or less rim width.

 

[posplayr]

Yours is good advice Jim as far as setting up sag to match at both ends. I just think the tire needs to be correct before too much other assessment takes place. Just looking at the photo of his bike I'd say it's a 2.5" or less rim width.

I agree if the wheel normally takes a 110/90, i would not stick a 130/70 on it.

And yes I suggested going back to stock and setup the sag before any tire changes.

I was more throwing out what wollow really is as far as a dynamic; sort of a low amplitude low side, high side oscillation. It is a natual dynamic . I just watched a guy setting close to a track record at Isle of Mann and I see the same motion albeit at 200+ MPH.

http://www.gixxer.com/forums/showthread.php?t=263771

 

[Billy Ricks]

I agree if the wheel normally takes a 110/90, i would not stick a 130/70 on it.

And yes I suggested going back to stock and setup the sag before any tire changes.

I was more throwing out what wollow really is as far as a dynamic; sort of a low amplitude low side, high side oscillation. It is a natual dynamic . I just watched a guy setting close to a track record at Isle of Mann and I see the same motion albeit at 200+ MPH.

http://www.gixxer.com/forums/showthread.php?t=263771

I watched the TT too. Those guys are amazing. You see how out of shape the bikes get and they stay cool and let the bike settle down. That takes some balls to ride that island the way they do.

I think the OP is seeing a couple of things with the 130 on the rear. Triangular tire shape from being pinched leads to both. This makes the rear resist leaning over and when it does it wants to flop down off the center of the tire. When the bike comes back upright it's more abrupt than it should be out back and the suspension gets unsettled.

Then not only is the sidewall flexing but the contact area while leaned over almost becomes an extension of the sidewall from being misshapen by being pinched too much. The contact area while leaned loses it's rounded profile and gets a little flat compared to what it should be. The transition from tread area to sidewall is flatter, for want of a better word, than it should be. You lose some of the definition between the sidewall and the edge of the tire. Hope you get what I mean here.

 

[gixerbike1]

Uhm, I are an Id10T, well i feel like one anyway

Uhm, I are an Id10T, well i feel like one anyway

Well then don't expect any miraculous changes.

Pos, I really didn't expect any, just a decent ride. some flex is to be expected under a heavy load.

The differences between radial and bias ply tires is very significant.

Oh, I'm fully aware of that, I've had bike's in the past with Bias ply tires and they handled just fine.

I'd say my on my GS750EX which is basically stock but with Progressives and fork brace up front, with Hagon shock in the rear with Avons all around I dont like to do any heavy cornering beyond maybe 60 mph. It runs fine at 85 mph on the straights.

Yeah, I had mine buried past 85 in a straight with no problems.:-\\\

With my 83 1100ED, with stock 37mm forks, racetech emulators, progressive and fork brace on front with Ohlins piggybacks on the rear and Sport Demons all around heavy corner at above 85 mph are a little scary, goes as high as you want to go straight till the wind knocks you off.

With 18" GSXR conversion 43mm forks (braces, progressive springs, emulators) and radials 170/60-18 back, 110/80-18 front (Dunlop/Avons modern stuff) with SU-145's now much more stable at 85-95 cornering. A little wollering going on and that is likely frame flex starting to have an effect.

Awesome, Sounds like a stout bike to me, lots of love spent on that one I see.

I'm now closer to a modern bike but not there when you compare modern 180/55-17 and 120/70-17 with a real stiff frame.

Anyway, with a GS you can get a thrill at 1/2, 2/3 or 3/4 speed of a modern bike depending upon what you do to it.

And that's about all I really plan to do with it.

Now Let me tell you what i found this afternoon.

I decided to check the air pressure in the tires just for the heck of it, low and behold they had very little.

Now being used to mostly sportbikes where if your tire is low on air, you can dang well see it. Not so much on tires with tubes in them.

My bad all the way round, no pun intended.

Filled the rear to 42 and the front to 36.

OH, And My boy read the tire size off to me wrong, it's a 120/90-18, just one size up from stock. the rim is actually 2.75 inches, Sorry about that.

So, Next i checked the sag.

On the front with no weight on the forks they measure 6.5 inches from the top of the dust boot to the bottom triple tree clamp.

With just the bike itself there was 5.5 inches of fork showing, with me on the bike it dropped another 1/4 of an inch, so total sag was 1.3 inches on the front.

The rear was 22 and 5/8's of an inch from the bottom of the mud flap to the ground with no weight on the rear.

With just the bike it measured 22 and 1/4 inches. With me on the bike it measured out to an even 22 inches.

So, not being an expert on suspension setup is this good or bad ?

Let me know what you guys think about this.

Thanks again,

Tommy

 

[posplayr]

I watched the TT too. Those guys are amazing. You see how out of shape the bikes get and they stay cool and let the bike settle down. That takes some balls to ride that island the way they do.

I think the OP is seeing a couple of things with the 130 on the rear. Triangular tire shape from being pinched leads to both. This makes the rear resist leaning over and when it does it wants to flop down off the center of the tire. When the bike comes back upright it's more abrupt than it should be out back and the suspension gets unsettled.

Then not only is the sidewall flexing but the contact area while leaned over almost becomes an extension of the sidewall from being misshapen by being pinched too much. The contact area while leaned loses it's rounded profile and gets a little flat compared to what it should be. The transition from tread area to sidewall is flatter, for want of a better word, than it should be. You lose some of the definition between the sidewall and the edge of the tire. Hope you get what I mean here.

Yea, the rear tire/sidewall distortion is not good. The only way you tolerate it is when the front and the rear are doing the same thing but given the differences in profile and loading that is seldom exactly the same.

 

[Billy Ricks]

Were these measurements taken with the wheel off the ground at each end and suspension fully extended or was there weight on the wheels? The first measurement should be wheels off the ground and suspension fully extended. If you want a very firm, aggressive ride shoot for 1-1 1/4" of sag at both ends with the weight of the bike and you in the seat, wheels on the ground. If you want a firm, sporty ride use up about 1/4 of the full travel. For a plush, lazy ride use 1/3 of total travel for your sag.

 

[gixerbike1]

awesome Video

awesome Video

Were these measurements taken with the wheel off the ground at each end and suspension fully extended or was there weight on the wheels? The first measurement should be wheels off the ground and suspension fully extended. If you want a very firm, aggressive ride shoot for 1-1 1/4" of sag at both ends with the weight of the bike and you in the seat, wheels on the ground. If you want a firm, sporty ride use up about 1/4 of the full travel. For a plush, lazy ride use 1/3 of total travel for your sag.

Hey Billy,

Those were with the wheels off the ground and no weight on them and the suspension was fully extended. I'm shooting for a sporty ride, kinda good all around.

Great Video by the way thanks :clap:

So, with about 5/8's to 1 inch in the rear and 1 and 1/4 up front what are your suggestions ?

Thanks,

Tommy

 

[Billy Ricks]

Hey Billy,

Those were with the wheels off the ground and no weight on them and the suspension was fully extended. I'm shooting for a sporty ride, kinda good all around.

Great Video by the way thanks :clap:

So, with about 5/8's to 1 inch in the rear and 1 and 1/4 up front what are your suggestions ?

Thanks,

Tommy

That was Jim's video.

The front measurement sounds good. Do you know what the travel is on the rear shocks? I would think probably about 4" at the shocks themselves. If you're unsure of that then take a measurement from somewhere straight above the axle to the axle itself. Take your sag measurement between the same two points. Again, with your weight in the seat. I'd set that up at about an inch as well as see how it feels. Run it as stiff as you can without introducing pogo effect after hitting bumps. I doubt you have damping adjustment so you won't be able to address that.

 

[Billy Ricks]

Once you get your sag set up for your weight then move to tire pressure. Go for a 10% rise in pressure cold vs hot. I think it's been talked about already in this thread. If not check your pressure on stone cold tires. Then go for a ride. You want to push the tires hard for at least 15 minutes. Check the pressure again. You want to see a 10% increase.

Once you get this done then you can start fine tuning the sag at both ends. Keep them proportional to each other. You're kind of stuck with spring rate and damping on the rear. Up front the spring rate and damping can be played with in a couple of ways if you find it doesn't suit you. I think what you've done to the forks will work pretty good for you with 1 1/4" of sag.

 

[Sandy]

A zip tie on each fork tube is a great way to see exactly what your suspension is doing. Set one at the top end of the travel where the suspension bottoms out and use the other to gauge how close you come to bottoming under different riding conditions. This one you will move around as you play with your settings and can also be used to help measure the sag. My personal preference is set the right hand one where the suspension bottoms and use the left one to see what's happening. This way on a naked bike you can actually move left one back down the fork tube while riding and not have to let go of the throttle. One critical thing to watch, and this is where the zip ties come in real handy, is to see how close to bottoming you get under extreme braking. You want to come close but not actually bottom out. Hope you don't get to confused with all this information overload, but once you start testing it will all make sense. It just takes some patience and a methodical approach and when you get close only do one adjustment at a time.

 

[posplayr]

http://www.thegsresources.com/_forum/showpost.php?p=994640&postcount=7

I dug up an old thread (only 1 year ago when I was struggling with same).

Ohlins suggests:

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

These need to be adjusted based on total stroke; the old GS's have longer stroke up front so make adjustments accordingly.

I used your numbers and here is what I get:

-------------F-------------R------
Static-----25.4--------9.5----mm
Laden-----32----------16-----mm

The other thing to do is make sure you bounce up and down a little to reduce "culomb friction" effect. But assuming your numbers are accurate. You can average the numbers (first6 on teh front and then on the back) measured by
a.) pushing down and letting up and
b.) lifting up and letting down to get a more accurate average.
c.) average there two numbers (for all 4 static/laden and front and rear)

From the numbers (Front laden) you have. The front is stiff but passable. If your springs are stock and not cut down then I think you need to remeasure that. Sprinsg are usually worn out and soft.

From the (Front static) you need more preload to drop that number a bit. Again check your meaurements with an average.

From the (rear laden) number your rear springs are too stiff.

From the (rear static) number the rear preload is high but passable.

That is at least what is indicated.

If you find your manual and check what the stroke is front and rear and then use Billy's numbers 1/4 full travel (for firm ride) F/B to recalculate to see what you need for laden sag.

Then use the Ohlins guide to get static sag or even just ride quality.

I'm starting to suspect (guessing a little here) you have a very stiff rear and need to bring the front more into line even if it ends up being a little harsh up front to get in balance with the stiff rear.