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Discussion Starter #1
Hey Fellers... Still trying to sort out my Penske 8975 shock.
I'm a big fat body at 275 lbs... and the bike just won't sag enough out back.
There doesn't seem to be anything wrong with the shock. I had Penske rebuild it when I first bought it (used), and even asked them to keep it "soft" as I wouldnt be seeing much racetrack use...just spirited Sport Touring.
I first had a 475lb Hyperco spring on it.. and it was exceptionally stiff. Then I changed to a 400 lb spring... significantly better, but even with the preload almost all the way out, I still don't have enough sag.. (no number available at present, but it's in the neighborhood of say 20mm). Certainly I can feel the stiffness, and I do believe this is the cause of my previously-whined-about skittishness at highway speeds.

Any thoughts or derision graciously accepted. Should I go to a yet-lighter spring?
 

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Hmm, something wrong here. For your weight I think a spring well over 500# would be required.
First thought, could your linkage be stuck or binding?
If not your linkage, maybe there is indeed something wrong with your shock.
 

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Discussion Starter #3
Hard to think that the linkage is malfunctioning; the bike is reasonably stable and compliant. I would guess any real linkage problem would be fairly obvious... still, I've got new tires coming in this week, so maybe I'll do some rooting around in there while the wheel is off; make sure everything is in order.

I'm beginning to wonder if indeed that shock could be faulty. I DID send it to Penske for a complete work-over/rebuild when I initially bought it some years ago; but for some reason I have never had a warm feeling about the handling ever since. One issue has been a weird imprecision at highway speeds, which seemed to be reduced when I backed off the rear rebound even more (it's about all the way out).
Some here know I have a venerable Bandit 1200 (150K miles and still awesome)... and I can throw that bike around with utter confidence. The SV -- I've always had to dance lightly with it, feeling oddly, slightly unstable.

I no longer have my stock shock... maybe I'll pick one up cheap off FleaBay ,,,try it for comparison's sake
 

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Hey Greg!:) I run that same shock and same 400# (Eibach) spring (mine came with 525# which was stiff as heck) and was unable to get the 'recommended' sag either. Getting anywhere near it and the spring was loose on the shock when the bike was lifted...so something wasn't right. Took off the shock to double-check that the pressure wasn't too high...it was fine. Reassembled with about 1/4" preload (now have 6 threads showing above the adjuster ring) and the bike rode much better.

Got to thinking about the rising rate linkage and tried going the other way...less sag to get up as far into the softest mechanical advantage region and this worked very nicely. My static sag now is almost non-existent...just a tiny amount and when I climb aboard it sags a wee bit...but nothing like an inch...and the bike rails turns and handles bumps SO much better than before.

When I had the swingarm off a few years back to service/inspect the bearings it was amazing how much drag all the seals created once I put it back together. Considerable drag trying to move it which is like having a shock set 50/50 with no shock present. Adjusting the Penske to minimum on both compression and rebound helped the ride a bunch too...then had to put back a bit of rebound until it settled down in the corners but again WAY less than most would think was normal.

Just for fun....please try lifting the rear via preload until your static sag is nearly (or totally) gone...then see how it feels, I'm betting you'll see that this is moving in the right direction. Back off the compression all the way then add rebound until it's well controlled in bumpy turns and see how you like it. The forks might need to be adjusted to accommodate the raised rear end but that should be straightforward for you. Best of luck!
 

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Discussion Starter #5
Just for fun....please try lifting the rear via preload until your static sag is nearly (or totally) gone...then see how it feels, I'm betting you'll see that this is moving in the right direction. Back off the compression all the way then add rebound until it's well controlled in bumpy turns and see how you like it. The forks might need to be adjusted to accommodate the raised rear end but that should be straightforward for you. Best of luck!
WHO I ask ... is more awesome than RECOIL ROB, folks??
(y)(y)(y)
Yesss... a few threads from the top... 'tis where I am right now. It's about as stable as I've been able to make it... but it still just doesn't inspire me to throw it into corners like my B12. It's STEADY...but just...Off somehow. Too stiff or something, not "forgiving". I don't know. It SHOULD be more planted. Can't explain it ..just yet!

Right now I have the wheel off the back (just got a fresh set of skins today). So I can "F" with it some... but I think I'm adjusted just about to where you're discussing now. I was seriously considering pulling everything apart (lower fairing, exhaust, linkage, shock), to see if I could find anything "OFF". I really just want to slap the new Dunlops on it and GO.

As I back off the preload more and more, the bike has generally become more friendly... but I'm up against that limit, and it's still quirky. How weird; I'ma big blob not overly far from 300 pounds.. running a 400 spring... and the thing is too stiff.
Is this a PENSKE problem? Valving too stiff? I've called them before and ...I can't recall any concrete solutions from them.
 

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Discussion Starter #6
Thanks again, Rob ... I know we've been through most of this before!
But now my thinking is: I started with a 475 spring... way too stiff... I'm down to a 400, which was an improvement... and you're having similar issues with stiffness and extreme preload setting results . . . .
MAYBE it's time for an even SOFTER spring, regardless of what other bikes and shocks might use. I mean, the 400 was BETTER... why wouldn't a, say, 350 or 375 be even better than that? Like you, I'm waaay out at the top of the preload; how nice it would be to have the shock running right in the center! Proper extension and valving?

Where can one acquire these ..springs.. that you speaketh of?
 

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Discussion Starter #7
I just got off the phone with an Eibach tech. He agrees with my assessment, to go even lower on the rate... says there may have been some mistake somewhere in the call-out. From what I told him he thinks there would be ample reason to drop the rate to say, 350.. or even less. That shock needs to live in the center of it's travel.

ROB--- (or anyone listening): Would you have dimensions for that (Penske-fit) spring, namely length and overall diameter?
 

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Greg....there's a couple of things mucking up the water here. First and foremost is the progressive linkage which is VERY progressive so things get a lot harder with just a little compression. Also the Penske is valved pretty aggressively so even with the compression adjustment all the way out there's a fair amount still at play.

My spring from Penske was '0500.225.525' which was way too stiff for me (even with the 4.25" swingarm stretch...which was amazing how it tamed the rear end) and seemed too short being that there was a lot of threads above the adjustment ring when the spring was at '0' compression, so I opted for '0600.225.400' which is on there now and working well. Eibach numerology is length. diameter. rate (lbs per inch) so the new spring is an inch longer and is why I have 6 threads left above the ring with a bit of spring compression holding the rear end up in the softest portion of the travel.

If you're running a 5" spring...there's NO way you can soften the preload enough while still holding the suspension in a favorable portion of the linkage rate. My 525 was rattling loose when I slacked it off anywhere near enough to get 25mm of sag...so I threw that out the window and went for the most suspension travel I could get which meant lifting the rear up as high as I could. I have NO static sag...or maybe 1/4" at most and it barely compresses at all when I get on in riding position. With the stretched arm and compression adjustment only in a few clicks it uses nearly all of the shock travel according to the tiny zip tie on the shaft....and this is over some really horrible roads catching air here and there. But set up like this the bike rides the best it's ever in my experience and can fly through some severe washboarded curves with good control. And with the stretch it won't stand up in 1st with WOT....will haze the tire and hold the front up maybe an inch or two...just about right. Very nice street combination IMHO.

If you haven't gotten a new spring yet....please try the 6" version as it'll give you a lot more adjustment range. Remember the spring just holds the bike up and the rate only determines how much preload is needed to hold it at a certain height. So long as you don't get into coil bind the lighter spring works just fine...and my 6"incher is nowhere near that so we're good. When the suspension compresses the linkage progression very dramatically increases effective rating so even a soft spring gets really hard once the rear end drops a bit. Longer spring, lifted rear works pretty well even though it's not a 'normal' setup. What have you got to lose?:) Good luck buddy.
 

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Wanted to add a link to an interesting article: Motorcycle Suspension - Leverage and Linkages I believe the SV's back when ours were made were VERY progressive, whilst the race bikes were more linear....which would be an easier job for the shock valving to handle. How do you valve a shock when the linkage mechanical ratios change dramatically through the stroke? I don't think you really can so you've got to 'choose your poison' where it's either way too soft at the top of travel and great down near the end...or visa versa.

Greg...at your weight unless you've got the spring preload really cranked up....you're going to be settled down where the rates are very high, and don't forget we've only got about 5" of total travel to play with. (I've got a bit more with the longer arm...all good) Every bit you settle when setting sag is travel you don't have left when you hit a big bump.

Suggest you look at your shock bump stop to see how much travel you're using then add preload to stay away from it bottoming. Betting you'll end up with minimal sag which might also help your cornering concerns.

Oh...hey, we've not covered your fork settings and adjustments...have we? It's also possible that something amiss in the front could be making the rear feel weird too, so once you've got the rear sorted it might be good to go over the front and see what's up. What spring rate/ make of springs? Fork fluid? Preload spacers (or distance from axle to bottom triple)? Fork protruding from top triple? Did the custom top triple duplicate the factory thicknesses and angles?
 

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Just throwing this out there. You can pick up a linear linkage kit for the 2nd gen SV. I have one on my track bike and I think it handles great.
 

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Discussion Starter #11
Thanks, Two- Blue! I'm running a K6 now...I think that is already a 2nd Gen. right?

So, Rob - I'm a bit SLOW on the higher details of the geometry in question.. But what I think you're saying is that the stock Suzuki linkage is partly to blame for this stiffness, yes? I mean, either that or the Penske shock has issues. Why should these things be working only at extreme-levels of (light) preload and Rebound settings? Something's off balance. You are running a +4 swingarm ..for SOME reason!

I've had some luck with backing all the way out on shock Rebound... AND.. softening-up the front Compression which i backed-out a turn or so. It's noticeably more stable in the turns... but I wish there was more!
Today I JUST backed out another turn on the front Compression... to see what happens... and also a turn on the fork Rebound.
This all feels like I've been here before; goes to show how important it is to keep careful notes!
So I've probably gone as far as I can with the shock adjustments, only four or five threads showing, Rebound set all the way out. Let's see what today's fork adjustments accomplish.
PS - I'm running 1.00 kg/mm Sonic springs up front.. with a Gold Valve kit.
Thanks for all the help, Gents!
 

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Discussion Starter #12
Thanks, Two- Blue! I'm running a K6 now...I think that is already a 2nd Gen. right?

So, Rob - I'm a bit SLOW on the higher details of the geometry in question.. But what I think you're saying is that the stock Suzuki linkage is partly to blame for this stiffness, yes? I mean, either that or the Penske shock has issues. Why should these things be working only at extreme-levels of (light) preload and Rebound settings? Something's off balance. You are running a +4 swingarm ..for SOME reason!

I've had some luck with backing all the way out on shock Rebound... AND.. softening-up the front Compression which i backed-out a turn or so. It's noticeably more stable in the turns... but I wish there was more!
Today I JUST backed out another turn on the front Compression... to see what happens... and also a turn on the fork Rebound.
This all feels like I've been here before; goes to show how important it is to keep careful notes!
So I've probably gone as far as I can with the shock adjustments, only four or five threads showing, Rebound set all the way out. Let's see what today's fork adjustments accomplish.
PS - I'm running 1.00 kg/mm Sonic springs up front.. with a Gold Valve kit.
Thanks for all the help, Gents!
52854
 

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Greg.....my swingarm stretch was for wheelie control, but it DID also soften the rear end response to bumps and made the bike a lot nicer on horrible roads. Looking at your picture you could gain an inch more swingarm length by moving the wheel back but, of course, you'd have to change sprockets or add a link to the chain.

The stock suspension linkage IS partly responsible for the stiff rear end feel. It multiplies the force required to compress the shock as it moves....and the farther it moves the more effective spring (and compression) rate you get, which is why it's good to have the rear end riding up high in the travel for best ride quality.

Couple of questions: Are you running a 6" spring on the Penske? And....how did you get a Gold Valve kit in your K6 forks? They're for K3-4 only as far as I can see? Did you swap for the earlier forks?

Are you running with zip ties on the fork tubes to monitor your travel? Mine has two.....upper one placed on when the springs were out and forks allowed to drop to the stops. That shows were they bottom, then the lower one shows how much travel it's using and is real helpful when making adjustments.
 

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Greg. According to Racetech's website the stock spring on a SV1k is 450 lbs/in.
You should absolutely be able to get the correct sag.
How long is the spring on that shock when off the shock?
How are you measuring sag?
Does the bike feel too harsh on big bumps or on all bumps?
Recommend you verify that you're not hitting the bump stops and bottoming out your suspension. Look to see if the entire shock shaft is clean. There should be some dirt/grime/etc. on the shaft just above the bumpstop. If the shock seals are completely wiping the shaft clean, then you're using all of the available travel and hitting the stop, which will feel much harsher.
 

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Discussion Starter #15
OKAY! Great progress!
With the infor from R Rob and others, I have basically given-up my focus on the Penske out back.. left it near the top of the preload (soft) and backed-out all the way on the Rebound screw. Like the drug dealer said: It IS what it IS. The stock linkage seems weirdly stiff.. maybe the engineers were thinking to compete with the Ducati 996's. who knows... But that's all it's going to be. SCREW "sag" numbers.
BUT - I turned my focus towards the FORKS. I'd had some weird settings, all over the map from YEARS now of trying to get this thing stable in a corner without that dreaded WEAVE at highway speeds.
So I backed off the bottom fork leg screws..(uhmm.. Rebound?)... because they were all the way in.... AND softened-up the Preload a couple of turns....
PRESTO! A VAST improvement! I had the bike out for three hours this afternoon over varied terrain... MUCH much more stable. Of course, the new Dunlop Roadsmartt II's really help (almost as good as the Roadsmart III's, which I think are the best Sport Tour tires ever made now!).
SO... I seem to be on the right track; I heeled hard into a few fast corners today and it feels greatly more planted.
Still wants a little fine-tuning....but I think this is near to as good as it will get, in this config.
 

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hey, stupid thought.. but the knuckle linkage is asymmetrical.. is there any chance in installing you put it in backwards?
 

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Bottom screw on the fork is compression adjustment, rebound is on the top. Again.....you have Gold Valves in the forks? Can you give a measurement from axle to bottom of triple? (static) How much travel are you using?
 

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Discussion Starter #18
Yes. as far as I recall (it's been seven years), I installed a Gold Valve kit. It worked brilliantly in my Bandit 12.
I'll get you some more data on the weekend when I have more time.
As I said, currently the bike handles far better than it ever did - although I would consider it "GSXR-tight". I think that's probably what the original designers targeted, as the bike was an off-shoot of the TL-R, in an era when Ducati was kicking-ass in Superbike, and the V-Twin sportbike looked like it was gonna ossify the world.
More data soon.. thanks guys! (y)
 
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