K75 Shock choice

Yeah, Gail; that's a Works shock much the same as mine (getting rusty and corroded around the joints).

They run 250psi of nitrogen in them; I'd suggest having a shop check the pressure and maybe top it up before going for a full rebuild (although with that many miles it sounds like it's time anyway).

Ugh, I need a shock too Still rolling on the original stock one.

Don't bother looking for a new Ohlins. I called and was told the K75 version has been discontinued.

yup, that is a Works Performance. It is due for a rebuild. Any competent wrench/shop that knows how to rebuild a shock should be able to handle it. you might want to call WP and see what they can tell you about it.
good shock, as long as their limited spring selections are correct for your weight. I was dead in the middle between 2 spring choices, and could not get full range from either of the ones available.
start off by reducing the preload- that looks to be set at "full load". the ramp should be settled in the uppermost slot of the adjuster)

when i got a WP for my K11, i could go with either their 600lb spring or their 900 lb one. The 600 forced me to run on setting 2 for preload, meaning i only had 2 more beyond that, and not enough for full touring mode. if i went with the 900, 1 was too stiff, and i could not get proper sag setting established without adding wieght to the bike.
too soft or too hard, and no option for the Goldilocks "just right".
(if still unclear, you need to do some reading on basic shock operations and terminology. Google is your friend, or try the Ohlins link i posted earlier)

bikerfish1100 said:

start off by reducing the preload- that looks to be set at "full load". the ramp should be settled in the uppermost slot of the adjuster)

Click to expand...

Actually that shock does not have a "preload" adjustment. They only had a "preload" adjuster on their Paralever shocks.

The adjuster is their ARS (adjustable rate suspension) adjuster. The adjuster changes how soon the spring stack transitions from the soft white spring below the cup to the stiffer blue spring. It acts similar to a preload adjuster without the initial stiffness or change in ride height.

Gail's is set on full soft (more travel before the lever hits the cup and transitions into the blue spring). With a low gas charge or a heavy load, that could lead to a jarring ride. Works specifies 250psi nitrogen charge. Any dirt bike shop or sport bike shop should be able to check the charge for free.





From Works:

CAUTION: This shock is pressurized to 250 psi nitrogen. This pressure is not an adjustable feature of the shock. Unless
there is a leak, the shock should not normally lose pressure. If the shock damping becomes soft or mushy (after an
extended period of time or number of miles) the shock may need to be serviced which includes shock oil and a nitrogen
charge. In this situation, re-pressurizing the shock alone may not
improve the action of the shock. (BUT IT MAY)

MULTI-RATE SPRINGS AND THE ARS SYSTEM
Depending on each application, either dual-rate or triple-rate springs are available. Dual-rate springs are just that-- a
spring set with two separate rates. This is done with a short spring stacked on a longer spring. As both springs collapse
they produce a soft, or initial, rate. The spring set will maintain this initial rate until the short spring stops compressing. At
that point, the spring rate "crosses over" to the stiffer, or final, rate. This multi-rate system allows a soft initial rate for
comfort on small bumps, but has the capability of soaking up the big pot-holes
and other road hazards.
ARS stands for Adjustable Rate Suspension. ARS is standard equipment on most
BMW K-series shocks. The ARS system allows the rider to increase or decrease
the load-carrying capacity of the shocks without changing the preload of the
springs. Depending on the application and spring set, the rider can increase the
load capacity of the shocks up to 50 percent. This allows the shocks to be correct
for solo riding, but still be able to handle the increased weight of a passenger and/
or baggage. ARS can also be employed during solo riding to stiffen the rates for
aggressive riding, or for riding on rough, broken pavement.
The ARS system consists of an indexing lever and a stepped cup that contains
the short spring of the dual-rate. The position of the lever in relation to the steps in
the cup determines how long the spring set remains on the soft, or initial, spring
rate. On most ARS applications, four positions can be selected from full stiff to full
soft. Indexing is done in a matter of seconds by rotating the lever or the cup by
hand. Indexing the cup to the lever is usually preferable to avoid interference with
passenger or bags. Adjustment of the ARS system should only be made while the
motorcycle is on the center stand to reduce the load on the springs.
Note: It is important to make sure that a step in the cup is positioned directly over the tang on the lever. This will prevent
damage to the cup and/or lever that can be caused by making partial contact between the tang and a step.
TUNING TIPS—The “softest” setting on the ARS does not mean that the ride will be the most comfortable at that setting.
It means that this is the softest spring setting which would be employed on smooth roads and with a solo rider.
Excessive suspension bottoming caused by rough roads or by the addition of a passenger or bags will cause a harsh
ride when the shock is adjusted to this setting. To eliminate this bottoming, adjust the ARS to the stiffer positions for a
more comfortable ride. Hence, sometimes “stiffer is softer.”
PRELOAD ADJUSTMENT—On the Works shocks for Paralever-equipped BMWs, a threaded preload is standard. (See
Fig. 3.) This allows the adjustment of the ride height of the motorcycle. The preload is changed by turning a threaded nut
up (higher ride height) or down (lower ride height) on a threaded part of the shock.The nut is a right-hand thread. It is
used primarily to set the ride height for solo riding, as the ARS should be employed when adding a passenger or extra
weight.

thanks for the specifics Lee.
i had their shock on my K11 for about 100 miles, and could not get it right due to limited spring choices (tried 2, and no in-between option available), so recall could be a bit fuzzy.
(fwiw- i ended up getting a used Ohlins, which worked really well)

Gail,
I had Works rebuild my shock in March. Total bill was $140 including the shipping. They replace all seals and recharge with gas for about $100. They suggested that the shaft be replaced for an extra $40 so I went for that also.

It feels like I'm riding on a new shock.

After looking at the Works website and application document the ARS system isn't available anymore for the K75 unless it's a custom option. If the spring rates are good for you, and after reading about the ARS system then it's a no brainer to have it recharged or rebuilt. Wish my K75 had one installed.

I really appreciate all the detail, and I've learned a lot.
I love my mechanic, but apparently shocks are not his thing, he did not identify that I had one I could send out.
Sounds like a project for the fall, when all riding switches to the GT.

Call around and find a dirt bike or sport bike shop that can recharge the shock with nitrogen to 250psi. Ride the bike to them. They can charge it in 10 minutes on the bike.
Should cost less than $25. Probably less if you smile nice at them. Hell, I've gotten it done for free and I'm old, fat, ugly, and a guy.

It might correct the problem. It might fix it for a while. Or you might learn that, yes you really do need to send it in to get it rebuilt. But it would be worth the little bit of effort and money to find out.

gawga_boy said:

After looking at the Works website and application document the ARS system isn't available anymore for the K75 ....

Click to expand...

My bad. it's still available for the K75 but at $500 the recharge/rebuild is still a no brainer.

http://cgi.ebay.com/ebaymotors/BMW-...2796312QQptZMotorcyclesQ5fPartsQ5fAccessories

I have a Works shock with ARS on a '92 K75S, so I'm really interested in this thread. That said, tell me if I'm off topic with the following and TIA for any insightful replies......

I am having trouble getting my head around the Works explanation regarding the adjustments to avoid bottoming. Doesn't bottoming occur when the stiffer spring is fully compressed? If so, how would one end up with more bottoming with the softest setting? As Lee says, the adjuster changes how soon the transition occurs. In the extreme case of the load completely compressing the soft spring, isn't that the same as adjusting the stack to full hard?

Maybe I need to go find and review the explanation Don E gave me when I was looking for fork springs. At that time I understood his logic for dual rate springs vs progressive rate springs.

In the meantime I have my Works shock set at full soft and it works great. I haven't been able to identify a situation when I've been on the stiffer spring.

Again, TIA. This is a terrific thread by many knowledgeable folks.
Dave in Iowa

98lee said:

Actually that shock does not have a "preload" adjustment. They only had a "preload" adjuster on their Paralever shocks.

The adjuster is their ARS (adjustable rate suspension) adjuster. The adjuster changes how soon the spring stack transitions from the soft white spring below the cup to the stiffer blue spring. It acts similar to a preload adjuster without the initial stiffness or change in ride height.

...SNIP...

From Works:
...SNIP....

MULTI-RATE SPRINGS AND THE ARS SYSTEM
.......SNIP.....
TUNING TIPSÔÇöThe ÔÇ£softestÔÇØ setting on the ARS does not mean that the ride will be the most comfortable at that setting.
It means that this is the softest spring setting which would be employed on smooth roads and with a solo rider.
Excessive suspension bottoming caused by rough roads or by the addition of a passenger or bags will cause a harsh ride when the shock is adjusted to this setting. To eliminate this bottoming, adjust the ARS to the stiffer positions for a
more comfortable ride. Hence, sometimes ÔÇ£stiffer is softer.ÔÇØ

....SNIP....

Click to expand...

rx35285 said:

Maybe I need to go find and review the explanation Don E gave me when I was looking for fork springs. At that time I understood his logic for dual rate springs vs progressive rate springs.
This is a terrific thread by many knowledgeable folks.

Click to expand...

Ditto on being a terrific thread.

My K75C has the original OEM shock and I know I'll be replacing it at some point and I'll do the fork springs as well. So all this info is just what I need to make an informed decision and purchase the first time.

Dave when you find info from Don E be sure to point it here as well.

Frank

gawga_boy said:

Ditto on being a terrific thread.

My K75C has the original OEM shock and I know I'll be replacing it at some point and I'll do the fork springs as well. So all this info is just what I need to make an informed decision and purchase the first time.

Dave when you find info from Don E be sure to point it here as well.

Frank

Click to expand...

the sooner you do that replacement, the happier you will be. that shock has been "dead" for quite some time (unless the bike has just not been ridden at all, in which case there are other issues of concern), and a new, upgraded shock will substantially transform the handling of the bike.

bikerfish1100 said:

the sooner you do that replacement, the happier you will be. that shock has been "dead" for quite some time (unless the bike has just not been ridden at all, in which case there are other issues of concern), and a new, upgraded shock will substantially transform the handling of the bike.

Click to expand...

Yep. It might be dead from age since the bike is a '86 but surely not from use. It only has 15K miles on it and 12.7K when I got it last November.

My 94 K75 is running the original shock too. I am taking a cross-country trip in 8 weeks and really really want to replace it with something better. Unfortunately I don't have $500 to spend on a Works shock (let alone $1,100 on an Ohlins). At the same time, though, I don't want to go cheap. What to do, what to do!

rx35285 said:

I am having trouble getting my head around the Works explanation regarding the adjustments to avoid bottoming. Doesn't bottoming occur when the stiffer spring is fully compressed? If so, how would one end up with more bottoming with the softest setting? As Lee says, the adjuster changes how soon the transition occurs. In the extreme case of the load completely compressing the soft spring, isn't that the same as adjusting the stack to full hard?


Dave in Iowa

Click to expand...

Bottoming is not coil bind of the spring. It is internal bottoming of the shock.

A typical K-bike shock has about 3 1/2" of travel. Around 1" of that travel is used supporting the weight of the bike and rider. That leaves around 2 1/2" to absorb bumps.

For explanation purposes, let's assume two springs as opposed to the Works 3 spring system.
250 in/lb. soft spring with 1" of travel to coil bind left after the weight of bike and rider are on it and a 350 in/lb heavy spring. Spring rates are for explanation purposes only, but are in the ballpark. Progressive 412s use 270/345.

With the ARS on full soft, it will take a bump force of 775 lb. to bottom the shock (250lb=1" + 350lb=1" +175=1/2" total=2 1/2").

With the ARS on full hard (soft spring locked out), it would take a force of 875lb to bottom the shock (305lb=1" +350lb=1" +175=1/2" total=2 1/2").

The Works shock actually has 3 springs, a soft spring that can be adjusted or locked out, a stiff spring, and another soft spring, above the adjuster, that cannot be locked out so that even on full hard you get some soft spring to absorb the little stuff.

The transition is pretty seamless. You really shouldn't notice.

toddlamp said:

My 94 K75 is running the original shock too. I am taking a cross-country trip in 8 weeks and really really want to replace it with something better. Unfortunately I don't have $500 to spend on a Works shock (let alone $1,100 on an Ohlins). At the same time, though, I don't want to go cheap. What to do, what to do!

Click to expand...

Aside from Works, Ohlins and Wilbers...there is YSS....about $3-400.

I bought one several years back while travelling, and have nothing but good things to say.

You can pick one up from Tom Cutter's place....
http://rubberchickenracinggarage.com/suspension.html

Or from Klaus himself...
http://www.epmperf.com/

They both know their stuff...and stand behind what they sell and service.

motoedde said:

Aside from Works, Ohlins and Wilbers...there is YSS....about $3-400.

I bought one several years back while travelling, and have nothing but good things to say.

You can pick one up from Tom Cutter's place....
http://rubberchickenracinggarage.com/suspension.html

Or from Klaus himself...
http://www.epmperf.com/

They both know their stuff...and stand behind what they sell and service.

Click to expand...

Hey Edde

I'm shocked this thread is still ticking. I sold my K75 a few months ago, but the YSS mono (that replaced the Koni that replaced the OEM) was the business. And Klaus was great to deal with.