Author Topic: K1100 fork spring rates, mine seem stiff!  (Read 9271 times)

Offline KCinSB

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K1100 fork spring rates, mine seem stiff!
« on: June 22, 2011, 11:45:17 AM »
In my quest to smooth out the ride of this K1100, I have mounted a Works rear shock, (see below), and it seems to help, but still bumping. Now I am wondering if the fork might have extra stiff springs. The rear will move with my weight now, but the front seems stiff legged. Did BMW offer different fork spring ratings? I expect the after market likely does, but wondering if BMW did. It doesn't seem like the fork is absorbing the bumps, at least from what I can see without having a wreck!
Also, I think it has 5 wt oil in it at the moment, should I try something lighter?.     :P
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No good turn goes unpunished, but it's fun to keep trying.........
1993 K1100RS, with LT Rack&Case, some old BSAs and Triumphs,... some even run!! Recent Dark Side foray... '65 XLCH tractor.

Offline frankenduck

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Re: K1100 fork spring rates, mine seem stiff!
« Reply #1 on: June 22, 2011, 12:04:16 PM »
The K110s only had one set of stock progressively wound springs.  How much fork oil did you add to each?

With 5W they should be soft.
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
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Offline KCinSB

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Re: K1100 fork spring rates, mine seem stiff!
« Reply #2 on: June 23, 2011, 01:10:22 AM »
Well, I discovered today that the springs are not too stiff. The fact is that with me on the bike, the fork is so compressed that it can only move 1/4 - 1/2" more !  So the exact opposite is the problem. Looked at another K1100, and with me on it, the fork has room to move, and does.
SO, now I am thinking the springs are too weak!  I have no idea how that would happen.    ???
  • Santa Barbara, CA
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No good turn goes unpunished, but it's fun to keep trying.........
1993 K1100RS, with LT Rack&Case, some old BSAs and Triumphs,... some even run!! Recent Dark Side foray... '65 XLCH tractor.

Offline KCinSB

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Re: K1100 fork spring rates, mine seem stiff!
« Reply #3 on: July 03, 2011, 10:43:21 AM »
Well,.... so far, I'm kind of disappointed. After installing a set of Works Performance fork springs, the improvement is almost nill. To be fair, I need to explain that I probably do not understand the theory of the set-up options.
The Works springs come as a 2 spring set used in each leg, a long spring and a short 5" spring on top of that, separated by a steel washer. On top of the springs, is another washer, and a plastic spacer. Then the top cap etc.
Inside the top short spring, Works gives you 3 different lenth steel tubes that act as spacers inside the spring, captured between the 2 washers. So, when the short spring compresses to the point of hitting the steel spacer, the long spring under it takes over,............... I think.   :-\  I believe Works could do a big favor in explaining what is actually happening, so you would know how to proceed. The instructions tell me that the kit has dual rate springs, and various spacers etc, but I guess I am too thick to get the relationship of spacers and results. I assume the longer spacer gives a harder ride. For lack of knowledge, I picked the middle length spacer and re-assembled. This is a fairly straight forward job, but a bit tedious, and I'm not looking to do it 10 times to get it right! The result was that the Bump Bump Bump over my "test route" is about the same. Just to be sure I was not dreaming, I borrowed my buddies K75S again, and rode it over the same route yesterday. It is like riding a cloud compared to my K1100. He mentioned that his '93 K75S has the 2nd generation Showa forks, which is not what is on the '93 K1100RS. Maybe I'm chasing shadows, not sure.  Maybe I just need a K75S......      ::)
Has anyone out there used the Works springs to get a smoother ride on a K1100RS? If so, can you tell me which combination you settled on? At the moment, I am inclined to remove all spacers from the top spring, and allow the total spring set to react without stops. After the 4th weekend, I will call Works to ask for help.
  • Santa Barbara, CA
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No good turn goes unpunished, but it's fun to keep trying.........
1993 K1100RS, with LT Rack&Case, some old BSAs and Triumphs,... some even run!! Recent Dark Side foray... '65 XLCH tractor.

Offline frankenduck

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Re: K1100 fork spring rates, mine seem stiff!
« Reply #4 on: July 03, 2011, 11:42:14 AM »
How much fork oil are you putting in each fork?  If you only drained them then you should put 350cc in the left fork and 400cc in the right. 

FYI: On a K1100 only one of the forks has rebound damping so the left and right forks are different.
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
New to K bikes? Click here.
K Bike Maintenance & Mods: Click here.
Buy parts here.

Offline frankenduck

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Re: K1100 fork spring rates, mine seem stiff!
« Reply #5 on: July 03, 2011, 11:56:03 AM »
I have some of the Works springs that I plan to install in the near future.   I've talked to a couple of people who installed them and they used the middle crossover tube and things came out fine.  The springs I have came with three sets of metal crossover tubes.

Soft(short): 2 1/2"
Medium: a hair over 2 3/4"
Stiff(long): 3"

The plastic spacer is 2 7/16"

I've had good resutls using Honda SS-8 10W fork oil.
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
New to K bikes? Click here.
K Bike Maintenance & Mods: Click here.
Buy parts here.

Offline frankenduck

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Re: K1100 fork spring rates, mine seem stiff!
« Reply #6 on: July 03, 2011, 12:10:46 PM »
How the springs work:  When the shock is initially compressed both springs are being compressed - each based on it's spring rate and length and the amoujnt of force applied. When there is enough force to compress the upper spring to the length of the crossover tube then any additional force is borne only by the lower spring.
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
New to K bikes? Click here.
K Bike Maintenance & Mods: Click here.
Buy parts here.

Offline KCinSB

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Re: K1100 fork spring rates, mine seem stiff!
« Reply #7 on: July 03, 2011, 02:47:52 PM »
Thanks for the reply.  OK, that is how I figured the system must work, and, I did use the middle lenght cross-over tube. I did put 350 and 400 cc in the legs, followed the book on that, and used 5 wt oil.  I think I need to use the short tube, or maybe none at all, which is mentioned as a possible in the instructions, but didn't seem right at the moment.  Just rode that same route again this morning on that borrowed K75S, man that is a smooootthhh riding bike.    :D
  • Santa Barbara, CA
  • SOLD
No good turn goes unpunished, but it's fun to keep trying.........
1993 K1100RS, with LT Rack&Case, some old BSAs and Triumphs,... some even run!! Recent Dark Side foray... '65 XLCH tractor.

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