1985 K100RS aftermarket rear shock.

I'm in the process of selecting a replacement rear shock. Ted Porter has told me that their "go-to" replacement for the older K-bikes is the YSS Z series. While I don't want to unnecessarily spend money on a high-end shock that I don't need, I also don't want to waste money on something inferior. So, has anyone here put a YSS on their K-bike?

Thanks,
Tom

Found these threads, mostly for the K75:

https://forums.bmwmoa.org/showthread.php?33252-YSS-Shock-on-a-K75S

https://forums.bmwmoa.org/showthread.php?25275-K75-Shock-choice

https://forums.bmwmoa.org/showthread.php?86606-95-K75S-Shock-options

https://forums.bmwmoa.org/showthread.php?21045-K100RS-Aftermarket-Gear-Recommendations

Also check out the threads in the Similar Threads pane below.

20774 said:

Found these threads, mostly for the K75:

https://forums.bmwmoa.org/showthread.php?33252-YSS-Shock-on-a-K75S

https://forums.bmwmoa.org/showthread.php?25275-K75-Shock-choice

https://forums.bmwmoa.org/showthread.php?86606-95-K75S-Shock-options

https://forums.bmwmoa.org/showthread.php?21045-K100RS-Aftermarket-Gear-Recommendations

Also check out the threads in the Similar Threads pane below.

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Good stuff in there. Thank you.

mcmlcccvrs said:

I'm in the process of selecting a replacement rear shock. Ted Porter has told me that their "go-to" replacement for the older K-bikes is the YSS Z series. While I don't want to unnecessarily spend money on a high-end shock that I don't need, I also don't want to waste money on something inferior. So, has anyone here put a YSS on their K-bike?

Thanks,
Tom

Click to expand...

I bought a YSS from Tom Cutter for my K75S a number of years ago when YSS was relatively new to the US market. It was a great improvement over the stock shock (most anything is in my opinion) and really improved handling and comfort. Tom had it dialed in for compression/rebound and pre-load settings, and I would buy one again without hesitation.

I bought a YSS by the way from Ted Porter.

You can still get Progressive Shocks that fit the rear of your bike. They have two different length models and then one heavy duty one. Depending on your use, either of the normal ones would be fine. If you are inseam challenged then the lower model would work. If you check Bob's BMW they show them available, and they are on Ebay and a few other places.

For info purposes I use the Progressive Heavy Duty model on my 1995 R100RT mono with a sidecar and it is really stiff. Works well in that application but unless you where a very heavy individual with a load, then the normal ones would work better on your RS. Not knocking YSS or any other higher end shocks but a lot of us don't need that level of shock, especially on a 35 yr old bike.

mcmlcccvrs said:

I'm in the process of selecting a replacement rear shock. Ted Porter has told me that their "go-to" replacement for the older K-bikes is the YSS Z series. While I don't want to unnecessarily spend money on a high-end shock that I don't need, I also don't want to waste money on something inferior. So, has anyone here put a YSS on their K-bike?

Thanks,
Tom

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I went with IKON on my 1995 K75. Very happy.

+1 on the Progressive shock


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FWIW, I have Progressive shocks (rebound and preload adjustable, heavy springs) on one of my air heads- I like them pretty well, and have had them rebuilt once previously. I have them set up to my riding needs, and worked with them to get what I needed. I'm 6 ft, 200lbs.

I also have a Progressive shock on my K75; I don't like it at all. It's the short shock installed by the prior owner, preload adjustable only, and relatively new (less than 10K miles). I find it doesn't match my needs well. It has too little travel for my taste and too little adjustability within that range of travel. At the softest rebound setting, it bottoms routinely and at the highest setting (the only one where it doesn't bottom) it is very harsh. Replacing it will be the next purchase I make for that bike.

My point is that regardless of what shock you purchase, I think you are doing well by working with a vendor (Ted Porter) that will help you with sizing and set-up so you are pleased with the result. Any good vendor will help you find a brand that fits your budget and need (they want you back as a customer). I recommend Ted Porter based on my experience, but there are a number of good vendors noted on the forum that would serve you well. I'm sure if that YSS is what he's recommending, it is a good quality product and value.

cycleman2 said:

You can still get Progressive Shocks that fit the rear of your bike. They have two different length models and then one heavy duty one. Depending on your use, either of the normal ones would be fine. If you are inseam challenged then the lower model would work. If you check Bob's BMW they show them available, and they are on Ebay and a few other places.

For info purposes I use the Progressive Heavy Duty model on my 1995 R100RT mono with a sidecar and it is really stiff. Works well in that application but unless you where a very heavy individual with a load, then the normal ones would work better on your RS. Not knocking YSS or any other higher end shocks but a lot of us don't need that level of shock, especially on a 35 yr old bike.

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Everyone's tastes are different, but I wouldn't dismiss the handling potential of the classic K-bikes by dismissing them as "a 35 yr old bike." They surely are, but they are also a platform that was well ahead of it's time, and with a dose of modern suspension parts, brakes, and tires, can be both highly enjoyable and very competitive with many more modern bikes.

The K-series introduced the motor/transmission as a stressed member of a trellis-like frame for BMW, resulting in an extremely rigid system. Although the 2-valve models are limited to bias-ply tires, there are some very modern design tires available (Pilot Actives are one of my favorites). Combine those with modern brake pads (EBC HH for example) either with the stock rotors or something like the EBC semi floating rotors and steel braided brake lines for greatly improved stopping.

A quality rear shock is about 70% of a bike's suspension in my experience, and today there are some really good options (purpose of this thread). Although many will say they don't need, or can't tell the difference with, a higher end shock, my experience is that most people actually are the Princess and the Pea, and will and can tell the improvement. I have two K75s - one with the basic pre-load-only Progressive and one with a fully adjustable YSS - and they are night and day for comfort and handling, at least for me. The early BMW K-bike front forks are nothing to write home about, but with a good quality set of springs, set to the correct sag and with the right amount and viscosity of fork oil can perform very well, and with a decent shock will run circles around any Airhead for handling. Upgrade them with the Race Tech cartridge emulator kits for a dramatic improvement.

Naturally, this is all a matter of personal preference, but for myself, I've gotten a lot of bang for the buck on my 2-valve K's with moderate upgrades: suspension, brakes, and tires.

K100RS Shock Upgrade

Greg Feeler is spot on with his post, in my opinion. I rode an '85 K100RS for years and many many miles. It had the cartridge emulators in front forks and an Ohlins rear shock. That was the best thing I could have ever done for that bike. It changed it into something much better. Set up right it rode better, handled and was pretty fast. The handling was what really gave it "superpowers" and it could run the mountain twisties faster than folks think the K100RS can. Ran it in the Blue Ridge 500 one year with the other "hooligan" riders going for low times. Took it to some track days, including Road Atlanta. Great for touring and moto camping. Those bikes have many strong points but the suspension was not one of them. It needs the upgrade. That is a good move. I don't know much about the YSS but sounds like it should be good. Probably any really high-quality rear shock would help that bike a lot once set up right. However I strongly encourage you to also get the forks done with cartridge emulators.

So are you talking something along the lines of Race Tech fork emulators? I wrench my own bike. Is this something I can do?

mcmlcccvrs said:

So are you talking something along the lines of Race Tech fork emulators? I wrench my own bike. Is this something I can do?

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It looks like no one replied to your question. I think it would help you to read about how cartridge forks work vs. dampener rod forks. The key part is that cartridge forks (especially the Race Tech cartridge emulators) can provide velocity sensitive dampening whereas dampener rod forks have mostly fixed dampening. The very simplified installation in classic K-bike forks boils down to taking the forks apart, drilling out the dampener rod flow holes until they are so large that they have no effect. Then you reassemble the forks, drop in the cartridge emulators from the top and install the specifed Race Teck springs and oil. This is all documented on the Race Tech web site.

https://www.racetech.com/page/id/80

About 10 years ago I put a YSS shock (from Tom Cutter) on my 92 K75S. It is still there and works great. I've been two up around the US and ridden solo plenty of times.

robsryder said:

About 10 years ago I put a YSS shock (from Tom Cutter) on my 92 K75S. It is still there and works great. I've been two up around the US and ridden solo plenty of times.

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Ditto! Same shock for my K75S from Tom Cutter. I don't ride two-up on that bike, but the shock is still working great.

I have tried the shorter Progessive rear shock for the K100 and found that it just didn't work for me. With the stock adjuster ( 5 positions ) and short travel, coupled with my weight it wasn't possible to find the sweet spot. It's hard to believe that something with just 1/2-3/4 inch less travel could go from too soft to too hard with just one click. So I went for the Heavy Duty progressive, that is adjustable for rebound and has an adjustable spring and nitrogen valve. This is the same type of shock that I used on my airhead sidecar rig. I find it works much better and really firms up the rear of the bike.

One thing you can do with the front of the bike is to change the fork weight oil or add more oil to the forks. The range on the K100 series was 330 ml for the stock K100 no fairing and up to 360 ml for the K100RT. BMW kept the same spring rate etc in the front forks of those bikes and just put in more oil to compensate for the weight of the fairing.