K75: add shock pre-load spacer

[stryder]

Has anybody here added a spacer/collar to his rear shock so more pre-load can be dialed in than stock settings?

I added an approx. 13 mm wide, abs plumbing spacer/collar between the stepped pre-load ramp, and the washer at the top of the spring, with the shock mounted, to try and add some ride height and extend service life as opposed to spending large on a new shock as the damping still seems okay.

Haven't had it on the road yet to evaluate, but this type of thing has worked in the past with other bikes I've had. Just wondering if anybody else here has done that and if so, what were your results.

[johnny]

greetings stryder...

welcome to motobrick.com...

i wanna make sure i understand... the value of the well being of your passenger is the cost of a 13mm wide collar made from abs rigged to your 27 year old shock...

j o

[stryder]

greetings stryder...

welcome to motobrick.com...

i wanna make sure i understand... the value of the well being of your passenger is the cost of a 13mm wide collar made from abs rigged to your 27 year old shock...

j o

LOL...hahaha..different forum, same question. 

Same answer: has anybody else done this, and if so, what were the results?

I think it may be a quick and inexpensive way, if not a creative and ingenious way, to help breath some life into a worn spring. I don't see a safety issue here. Additonal preload spacers are not uncommon. I just came up with a way of adding one to a K 75 shock, that apparently are unrebuildable. I'd rather see how this works than spend a grand on a new shock.

(By the way, since you're all up for safety, and who isn't?, stay away from the Progressive Suspension K75 replacment shock. The one I had blew a seal..2 up...at speed. Good thing I'm an experienced rider and could feel the difference in handling and didn't lean into the exit ramp. Cleaned up the huge mess, and rode home in limp mode...hence, I'm looking to keep what I have...the original shock, rather than put my passenger in harms way with another aftermarket shock. :2thumbup:)

[TimTyler]

The cheapo Progressive 412 K75 shock is a almost a POS and is still probably a step-up from the K75 OEM shock from what I've read.

I eventually upgraded from a 412 to a Progressive 465 and it performs much better, for less than half of "a grand".

Modifying a rear shock with a plastic spacer sounds like a recipe for disaster to me.

[F14CRAZY]

I got thinking of posting and asking about the stock shock today...not exactly about a spacer but the stock shock I'm running (replacing a leaking Progressive 412...hey it was $25) does seem to be a bit worn. I have it set for max preloaded but it's bottomed out a few times on Michigan roads (that probably explains it). Its just been me (144 lbs), the fiance (like 115 lbs), and the LT top case and Integral side cases (all pretty much empty). Don't know how a pair of 200 lbs riders w/ luggage would manage

[johnny]

rear shock bottoming out aints good... it stresses the entire shock mechanism and will eventually cause the shock to snap...

works performance has been very good to us... our rs motobricks completely loaded 2up rolls across the truck scales at 1280 pounds...

so... ours were a special build... as they all should be... and neither have never bottomed out... even when they should had...

we donts mess around with cheep tiors and we donts mess around with cheep suspension...

without proper tiors and suspension... nothing else much matters...

j o

[Scott_]

......Don't know how a pair of 200 lbs riders w/ luggage would manage......

I would think that a K75 would be a little underpowered .......

[johnny]

the k75 is a capable 2up moto... just gotts to keep the revs high...

we 2uped the brickus turkus through the socal mountains faster and smoother than on the 1100rs... its was freaking rad... on bias ply tiors butts a new rear shock...

that 93 k75s carving canyons was like riding a magic carpet... may eat drive shafts and final drives 2up loaded... butts what the hay...

j o

[F14CRAZY]

......Don't know how a pair of 200 lbs riders w/ luggage would manage......

I would think that a K75 would be a little underpowered .......

Didn't people tour the country on like, R60's with big azz Windjammer fairings and Krauser luggage? I mean they made it there and back just fine

[stryder]

The cheapo Progressive 412 K75 shock is a almost a POS and is still probably a step-up from the K75 OEM shock from what I've read.

I eventually upgraded from a 412 to a Progressive 465 and it performs much better, for less than half of "a grand".

Modifying a rear shock with a plastic spacer sounds like a recipe for disaster to me.

Well I was thinking when I finally do replace it, it would be with another, stock shock, and that's gonna cost me.

The stock shock has lasted a good long time. More than that POS Progressive Shock, but it must have been the cheaper model, not the one you're talking about.

Well, it may be that no one else has tried to ramp up the "pre-load-ability" of the stock shock, so I'm going to try that bad boy modification and report back. If there's a safety concern I have it's with the front geometry changes and the possibility, perhaps the very remote possibility for wobbles/tank slappers, weird turn in etc. I'm not worried about the mod itself coming apart/off. It's in there pretty good, but you never know until you try. The bike's not due back on the road until Sept 1st, at which time I'll ride it down my "suspension set up road", i.e 5 miles of undulating pavement with many high speed compression hits, and that'll  give me great feed back right away.

This mod has been on my mind for quite some time, so I had to scratch the itch. 12 years ago I had a then new, sport touring bike that's still being made and still very popular today. One criticism about the "first gen" models was the supposedly weak shock, as in it needed a stiffer spring. One rider went out and bought a Wibur's or an Ohlins, I forget which, super duper shock for a boat load of money. Great shock, for sure. However, shortly thereafter, other riders were modifying their stock shock by adding a spacer/washer under the spring, for a total cost of about 5.00 plus their time/labour. Buddy with the super duper shock reported, he tried the mod on his stock unit, and...it performed as good as the super duper shock. True story.     

[johnny]

shock snap... down... ambalance...





j o

[pdg]

If there's a safety concern I have it's with the front geometry changes and the possibility, perhaps the very remote possibility for wobbles/tank slappers, weird turn in etc. I'm not worried about the mod itself coming apart/off. It's in there pretty good, but you never know until you try.

The rear of my 75 sits over an inch higher than it did with the stock shock on full extension, which makes the forks steeper than original. Means reduced trail etc.

Also, my fluidbloc doesn't.... It's on the list 'to be looked at' sometime.

Overall, handling is much improved to my mind. Faster turn-in and easier to get round tight turns - no loss of straight line stability at any speed I've seen on any surface. If anything, stability is actually better because it's lost some of the 'laziness'.

As for the fate of my stock shock? It puked all it's oil all over the rear tyre and brake, which was nice. Once it lost any semblance of damping it felt better for the last 10 miles I did on it before putting it on the 'to be weighed in' pile. If your original shock has done enough work for the spring to sag I'd say the seals are on borrowed time.

[stryder]

shock snap... down... ambalance...


j o

Ouch, that truly sucks. :-( What's the story behind that special K crash? I see the shock shaft snapped, but was that as a result of the crash, I see another bike down, or the reason for the crash, and if so, what caused the snap? Bottomed out? I see the tire has separated. 

The mod I effected should keep the bike/shock from bottoming out, but I won't know about topping out until I ride it. I figure of the approx 13mms added preload, maybe 1/2-1/3 of that is to make up for the spring sag and the rest is the added amount, i.e. maybe 5-7mms which shouldn't produce top outs IMO but I'll have to find out when riding it.

[stryder]

If there's a safety concern I have it's with the front geometry changes and the possibility, perhaps the very remote possibility for wobbles/tank slappers, weird turn in etc. I'm not worried about the mod itself coming apart/off. It's in there pretty good, but you never know until you try.

The rear of my 75 sits over an inch higher than it did with the stock shock on full extension, which makes the forks steeper than original. Means reduced trail etc.

Also, my fluidbloc doesn't.... It's on the list 'to be looked at' sometime.

Overall, handling is much improved to my mind. Faster turn-in and easier to get round tight turns - no loss of straight line stability at any speed I've seen on any surface. If anything, stability is actually better because it's lost some of the 'laziness'.

As for the fate of my stock shock? It puked all it's oil all over the rear tyre and brake, which was nice. Once it lost any semblance of damping it felt better for the last 10 miles I did on it before putting it on the 'to be weighed in' pile. If your original shock has done enough work for the spring to sag I'd say the seals are on borrowed time.

That's great feedback thanks.  :2thumbup:

 

[johnny]

the shaft snapped 2up... that took out the tior and everything else...

j o

[TimTyler]

The pre-load adjustment screws on that pictured, snapped shock are all the way in the OFF position, which seems odd for a 2-up config.

[stryder]

The pre-load adjustment screws on that pictured, snapped shock are all the way in the OFF position, which seems odd for a 2-up config.

No, as in zero preload, riding 2 up, (really?) may have caused the shaft to snap as something's gotta give if/when the shock bottoms out for *who knows how many times*. (I read a report about an expert as in national racing champ, rider who continued to ride at high speed, 2 up, even when bottoming out his shock 6-7 times, causing major engine damage) Looks like the weakest point, the give, was the top of the shaft *if* that was the case. 

That's a shame. But, really, we are all at risk of a catastrophic shock failure/collapse. I've read enough stories like mine about blown seals while riding. The new R1200rt shock recall fiasco only drives the point home. What may have happened if that defect didn't show up until much later? Peeps would have felt 100% safe on their new bike, only to perhaps have sufferred a catastrohic faiulure. MG had something like that a while back too IIRC. So even though I appreciate that pic being posted and the good will behind it, we all take our chances that our equipment won't kill us, regardless of how new it might be, every time we throw a leg over.   

[subforry]

Increasing the spring pre-load is kind of, but not quite, like increasing the spring rate.  The problem with increasing the spring rate is that the dampening and rebound valving is not stiff enough to match the spring.  Of course this doesn't matter because at 18 years+ age of our K bikes the stock shock has since leaked oil and lost pressure thus the valving is doing nothing.

If you are really attached to the stock shock then you could just buy a stiffer spring.
http://eibach.com/america/en/

[F14CRAZY]

Would you rather ride on a questionable rear shock or trailbrake and whack the throttle on exit, because if you aints slidin you aints ridin?

[Motorhobo]

Would you rather ride on a questionable rear shock or trailbrake and whack the throttle on exit, because if you aints slidin you aints ridin?

Oh crap -- it's contagious.

[johnny]

the more i think about it the more im thinking car shock and car tiors...

 



johnny

[stryder]

And so I rode the bike several times with the 13mm thick spacer and it was too much pre-load even on the lowest ramp setting...harsh ride. So I swapped it out for a 7mm spacer cut from a metal plumbing tube, and that works much better, more compliant on the lowest setting, but firmer than the highest setting without spacer, which is what I was after so I consider the mod a success re getting a few more miles out of a worn shock until I can get some extra scratch together for a good quality new unit.  :riding: