My forks springs are sagged out and could do with some new ones. What fork springs have forum members fitted to their bikes?

Before you go pulling it apart, have you changed the fork oil in recent times? I know that the Bricks have a reputation for the front end being soft, but I changed my fork oil...won't tell you what sort of stuff came squirting out, and it made quite a difference.
Sean.

I had a similar experience to Sean. If you do need springs Works performance in USA have a good name

If I was going to do my 85 RT, I would use Progressive Suspension fork kit 11-1126.
http://www.progressivesuspension.com/


If you do not know when last changed, do the fork oil first.
I just changed mine again (yearly) with Belray 10wt fork oil



Dale

O.K. will try changing the oil first and see if that makes a difference. I have some 10wt Motul fork oil I can try, if that is too firm will try some 7.5wt. Will let you know how it goes.

I have the K75 'S' fork option retrofitted to my K100RS which use short, firm springs and a much-reduced fork oil capacity compared to the other models, of only 280cc per leg. I have experimented (thick glasses, lab coat, pocket protector) and now only use 5W fork oil and change it at least once a year. The oil absorbs all manner of detritus over a short time and is asked to do a Very Big Job, when you think of it. But one thing to try, assuming your springs are actually in good nick, is to very slightly increase the amount of oil over the recommended level in each leg, which will increase the firm 'feel' of the front end. Conversely, reducing the amount of oil will tend to make it 'pogo' a bit. It's quick and easy to do and draining it out into a clean container for measurement and potential re-use is a cinch if it doesn't work as you'd hoped and/or like.

Something that confuses things a bit is that the previous owner lowered the bike, but only slightly about 3/8" to 1/2" In the Haynes manual that came with the bike someone has handwritten that the oil capacity is 300ml. It says in the manual that the length of the springs should be between 395-401mm. I believe some of the early forks have two separate springs but surely they don't measure 400mm each in length, that must be the measurement of the overall length of the two springs together? At the moment the forks are getting the full 7 1/4" of travel as you can see the witness marks left by the dust seals about a 1/4" under the bottom of the triple clamp.

Nothing but the best up here in the bush: I used auto transmission fluid last time. Its about 10 weight I suppose. Seems to work fine with a sidecar.

G'day Steve1959 , In my 87 KRS I'm currently using OHLINS springs , they are a one piece linear spring , they had been in for maybe 15 years , after much experimenting with oil ( different weights not volume ) and at my Mechanics suggestion I'm using ARAL 0-40 wt , the OHLINS give quite a firm ride which may work for you with the heavier RT , having said all that I'm thinking of trying a set of WILBURS which are progressive , they are available locally too !

JR

Melbourne Australia

I have pulled one fork out and dis-assembled it, drained just over 200ml of oil out which is a hell of a lot less than the 360ml in the workshop manual or the 300ml handwritten in the book. There is only one spring and it measures 515mm long and has been cut off at one end with a side grinder. Looks like someone in the past has put in some springs they had out of who knows what, so a combination of bodgey springs and lack of fork oil is responsible for the strange feeling in the front end. Not too sure where to go from here. One good thing is the forks were easy enough to pull apart.

That is real nice to do that, sometimes I think a bit of retrospective abortion would be a good thing. be a bit wary of what you try to get as there are a few different types of forks and slightly different diameters.
There was a post here about it but I cant find it.
I would just put new springs in as with used ones you dont really know what you are getting.

Since your spring did measure 515 mm, it seems like the distance pieces are thrown away, have that in mind if looking for new springs.

About different diameters: All Fichtel & Sachs which is used on the K100 (eccept 4V) and early K75`s have the same diameter (41,3 mm).

Later K75`s got Showa (41,0 mm), all 4V`s got Marzocchi (41,7 mm).

The forks have been lowered, so the next thing I will look for are the spacers to see by how much. I think you are right about the springs Rick G and the Works springs look like the go, I like the idea of the two straight wound springs of different rates. I will see what it has been lowered by and check if they do lowered springs to suit. The forks are the early Sachs type.

Steve you can borrow mine if you want, could be some time before i need them. 1984 K100rt forks complete.

see albyalbatross about his sagged out fork springs ...and what he has done .....some good advice to be followed there ...

from memmory his were sagged about 40 mm (after one of our workshop day expeditions )

he has replaced them with verry positive results ....also ask about his spring choices and fluid preference after

i recently installed 7.5 weight oil but found the ride too soft for my liking ..so removed about 100 mm of 7.5 and installed the difference with 10 weight ...giving me something in between ...i notice that it doesnt dive so much entering corners but isnt too harsh on the forearms along a really potholed / country road surface as the 10 weight only was ....(10 weight is totally cool for good "town"road surfaces giving good feedback , but a pain in neck on long distance runs ) but we all have our preferences ...huh ?

note this is an rt with the sitchel type forks so weight balence differences apply to an rs and or later models

charlie99 wrote:note this is an rt with the sitchel type forks

This made me curious........what is a sitchel type fork, Charlie?
Did you mean Fichtel & Sachs.......?

you got it inge ...too tired and words running together ....sigh ,,,,yawwwn ..thanks for the correction mate

That`s OK, Charlie........it`s much easier for me.......
it`s in the middle of the day in Norway.

I work for EPM Performance which sells Hyperpro Springs. I have a set in my K1100 but they do carry them for the K100 also. It is a progressive spring. I would give them a look before you decide.

Inge K. wrote:That`s OK, Charlie........it`s much easier for me.......
it`s in the middle of the day in Norway.

It is the midnight sun at the moment so Inge doesn't sleep till August

Rick G wrote:It is the midnight sun at the moment

In the middle of the day.............................always.

Thanks for the offer of a loan of your fork springs Keith, I had forgotten that you had a set. I have decided to try a set of Wilbers springs and they should be here in a day or two. Greg, the guy at A.S.R. says Wilbers advise the use of 15wt in the forks if they are RT forks which mine are as opposed to using 10wt if they are standard K100 forks. 15wt sounds a bit heavy to me but will try it and see how it feels, they also give the fluid height as 170mm. He said the rebound circuit hole drilled in the damper rod is a different size on the K100 standard compared to the RT/LT. Does anybody have a set of forks from a standard K100 so they can measure the difference? I think the hole he refers to is the small one near the top of the damper rod. The hole diameter is 4mm in my RT forks. Will report back how it all works out and thanks to everyone for their advice.

G'day Steve1959 , very interested in how the WILBURS go , as I said earlier I'm thinking of trying a set , I'm looking for a more compliant ride than the firm OHLINS that I have now .

Ciao

JR

Melbourne Australia

Hi J.R. I eventually went with the Wilbers because they are supposed to be specifically made to suit a certain application. I am like you, I want a compliant ride as I have problems with arthritic hands. But I want good handling as well, so hopefully with the new springs we can find a happy balance. There are two progressively wound springs available and I have gone for the heavier of the two on the recommendation of Greg at A.S.R. I have heard Ohlins springs tend to be a bit on the firm side. I have a Ohlins shock on the back and am gradually dialing it in to suit me.

fluid height at 170 mm ,,,what the ?

never heard of that expression before ....in almost everything i have read or seen the fluid was a quantity measurement .

i dont supose he gave you a special technique to measure that height steve ?

there are many threads on recomendations for fork fluid and volumes in the forum .

G'day Charlie , when I spoke with ASR about the WILBURS springs they said that the way they determine the correct volume was to set the fluid height by fully compressing the fork without the spring inplace then measuring down from the top of the fork tube to the oil level , he gave me a figure but I forgot the actual number , it's all in the install instructions supplied with the springs .

JR

Melbourne Australia

well thats kinda different jr ...this method would assume that there might be some differences between lower fork tube bodies , dampers etc ..i guess and the height mesurement allows for compensation for that ...it would be kinda interesting to see how much was collected (drained out ) after this method was employed . it certainly might allow for things like the differnt manufacturers ...fitschel % ...and the other later types

thanks for the update

Hi Charlie, I have a photo of the tool you use to set the fluid height but can't get the hosting thing to work. Have hosted photos before but it will not work now for some reason. The tool has a collar which sits on top of the fork tube in which slides a pipe which is 5mm in diameter, 300mm long and adjustable Attached to the pipe by a short plastic hose is a syringe. You set the tube so it is 170mm (or what the fluid height is) from the end of the tube to the underneath of the collar and then place the tool on the top of the fork tube which is fully inside the fork lower. You just siphon off the excess fork oil with the syringe which will give you the correct fluid height. This makes sure the fluid is exactly the same in both forks.

cool steve ....always learning ///but my question still remains, does that coincide with the recommended and documented volumes of fork oil ---per the bmw workshop manual .for both fitshel and sachs ...or the showa ...in any case it certainly would be a good method for confirming measurements ...or at least equall amounts ...that make it to the fork lowers ...

It does coincide. I have done the same and had to drain them once. Early K-RT and I got 360 ml IIRC. Also 170 mm from the top of the stanchion. Part of the working of the suspension is by compressing the air 'pocket' on top of the oil. I guess they determined that the 170 mm is the right quantity of air. I don't think my progressive springs are Wilbers, but it also said to use 15W oil.

Steve you can expect the forks to be matched to the faired RT weight so with yours being naked you're running lighter in the front than they expect so their weights will be stronger on your bike at present, could result in a harsher ride till the fairing is countered

aye !! the fairing / screen does give some down force at speed .

when i had broken my screen off , i noticed the front end was verry "light " and sat a little higher than normal ....or thats what it felt like .

thanks for the update rene !!! good to know

Hi Keith, the springs that I am getting are to suit a K100 naked model which is a different part number to the RT/LT spring. Wilbers also make a spring with another different part number to suit the K100RS. It appears that with the original two spring set-up that the forks had originally, all models had the same springs the only thing that seems to be different was the pre-load spacer to compensate for the extra weights and down force of the fairings. Have a look at www.asr.com.au

STEVE1959 wrote: the only thing that seems to be different was the pre-load spacer to compensate for the extra weights and down force of the fairings.

The spacer was similar on all models (except S fork) with Fichtel & Sachs fork,
the added weight of the fairing was taken care of by an increased oil volume.

Righto Steve seems you are across it, some people forget they're the windsock on what was once a loaded at speed bike.

I damaged one of the snap rings that hold the fork caps in. I rang the BMW dealer in Newcastle today and there aren't any in stock in Australia and it will be a three or four week wait for them to come from Europe. MotoBins don't list them and I googled the number and it seems as though it has been discontinued on the sites I looked at, although Brisans in Newcastle seem to think they are available. I have tried the local bearing service places and the answer is NO and the hydraulic and pneumatics places. Any suggestions where I might get one? The number is 31421450543 and it is to fit a 1985 K100RT. It is the only thing stopping me from getting the front forks back in the bike.

You can try the BM Shop in Brisvegas. As many have said here, they're not the cheapest place in town, but they DO have a lot of parts.

http://www.bmshop.com.au/home.aspx

Don't bother emailing them, as I'm still waiting for an answer to an email I sent them in 2007. Give the number a ring and speak to Trish or Chris.

Sean.

Hi Sean, thanks will give them a call tomorrow, Munich Motorcycles are probably worth ringing as well, a mate told me they are good if you really need parts in a hurry.

I've dealt with Trish a few times before and they post stuff very quickly. Just don't get it sent COD...costs an arm and a leg. Ask me how I know!

Hi Sean, right you are... the part I am after is only worth $4.95 and it will go into a ordinary envelope so here is hoping it doesn't get sent in some elaborate packaging and end up costing a arm and leg!

good to hear steve ....i bought a few fairing insulators(rubbers ) and fitted standoff type washers from trish a week or so ago ...weren't dear either (for bm parts anyhow)

Rang Trish at the BM shop and they don't have them. Have to go into Newcastle today so will try at a couple of other places.

No progress on the snap rings I'm afraid, have ordered two at Brisans but the guy said they will be three or four weeks wait to come from Germany. None of the other usual parts places seem to have them, or bearing services etc. Looking at the online microfiche it says that it is a discontinued part? I hope this doesn't end up being the case. I have a friend in the U.S.A who is going to inquire over there.

This could end up being a problem for a lot of people if the part is discontinued.

Very strange that the BM Shop don't have any! Even second hand ones!

Go to someone that make springs and get a bit of wire the right diameter, bend it around a cylindrical thingy and cut to suit it is not difficult. Even piano wire or stainless steel wire.
http://www.industrialsprings.com.au/wire.htm this mob has every size you could ever need

That's why I am on this forum. For the lateral thinking and practical advice.

Saxon7 wrote:That's why I am on this forum. For the lateral thinking and practical advice.

+1 Sean
88

Blakey, Trish at the BM Shop did say they may have some used but she would have to have a look, Munich Motorcycles have answered a e-mail and they have some used ones but better than I have just read my e-mail inbox and c75cster has come to the rescue with the offer of a loan of whatever I need. Great, thanks for that Keith, I will let everyone know when or if the snap rings arrive from BMW. I had considered getting one made but thought I would exhaust the other alternatives first.

An update on what has been happening. The Wilbers springs arrived from ASR after ordering them on the phone and it was agreed K100 standard springs were the ones to go for. They arrived two days later and it says K75RT on the box. I thought "what the hell" so I e-mailed Greg not very happy he had sent the wrong springs but he e-mailed back saying he thought the heavier rate springs from the K75RT would suit my weight better (95kgs). In the meantime k75cster helped out by loaning me some snap rings for the fork caps, thanks very much Keith. The bike had been lowered 30mm by the previous owner but the plastic spacers that had been fitted looked as though they had been just cut off with a hacksaw and weren't very square and therefore not the same length all around. So I had a mate with a lathe face them up so they are now 25mm long instead of 30mm. So in with the new seals from MotoBins, re-assembled the damper rods and put the forks back together. The fluid height recommended by Wilbers is 170mm from the top of the fork tubes with the tubes pushed fully home inside the lowers but because of the 25mm lowering spacers I took that back to 145mm. Wilbers also recommend 15wt fork oil but seeing on had 10wt on hand I tried that first, actually 10wt is recommended for the K100 springs so why the 15wt for the K75RT I am not sure maybe because of the fairing? It took quite a bit to compress the pre-load on the springs I would say more than the 40mm max that Wilbers recommend. Forks back in the bike with R series fork gaiters fitted from MotoBins. Pushed it of the stand and immediately noticed not a lot of static sag in the forks, probably 15mm or so. Out for a test ride and the first thing I noticed is the bike is a lot less ponderous at low speed and riding out of the yard you could feel a difference straight away. Overall on the road the bike feels a lot more secure, planted and stable and the steering has slowed a bit too not having the nose down so much, the 5mm off the spacers probably help a bit with that as well. The ride quality which was a top priority is also very good and reaction to sharp bumps is quite good, one reason I tried the 10wt first. All in all the effort has been worth it and I can definately recommend the Wilbers springs. Another thing with the lowered forks is that it cuts back the amount of travel so the overall movement is a touch over 6"