Hi everybody,
I am French, excuse me for my not very good english.
I have a 1987 BMW K100 LT since 2 years.
Some days ago, I wanted to renew the front fork oil.
But, to my surprise, it seems I have a suspension from a K75 S.
Indeed, inside the stanchion, there are 2 suspensions springs instead one (for K100 LT) of about 20 cm length (I looked to the Haynes technical revue)

Do you think it is dangerous to ride with this kind of suspension or is it possible to change suspension from a K75 S to a K100LT?
And an other question: what is the difference between these 2 kinds of suspensions (I mean: softer, harder...)?

Thank you very much for your help, I am going to wait you answer before refitting the forks. Perhaps have I to find original K100LT forks?
Thanks again.
Olivier

Bonjour Olivier,

I am certain you know the saying - "If it ain't broke - don't fix it."

If you have been entirely happy with your ride for the past 2 years, why change now?

Dangerous - no............Different - yes..................join the club.

Just be certain to replace the correct amount of oil for the forks you have - and not the forks you thought you had!

By the way - yor English is a damn sight better than my French - bravo.

TJ

Hi Beachcomber.
Thanks for your answer.
So, I will not change these forks, but for sure, I will have to check the amount of oil...it's not the same with K75 and K100...

Merci beaucoup
Olivier

OK, you want to learn French, read this or jump to the English section in the second part of my answer.

Olivier,

Il faut savoir quelle sorte de fourche tu as.
Il y a 2 types pour les K75. La premiere generation avait un debattement de 185mm. A partir de 1990, la fourche a etee remplacee par une nouvelle avec un debattement de seulement 135mm et la quantite d'huile est differente pour les 2 fourches. Les fourreaux de 185mm prennent 330cm3 de SAE5 et ceux de 135 prennent seulement 280cm3.
Your English is great and I don't know why I replied in French

English:
As I am riding a K75 too, I know some of the differences between the K100 and K75.
The first generation of K75 had a set of forks with a travel of 185mm. The last generation has only 135mm travel and the hydraulic dampening is only installed in the left fork.
The 185mm takes 330 cubic centimeters of oil when the 135mm take only 280 cubic centimeters.

Beachcomber, I wanted to reply in German, but I was reading on another forum that your German is only limited to 200 words . I am the same (forgot my 3 years of German taken at High School), but if we ever talk about party, we will be able to converse together.

Bert.

Your forks may be K100. My 1986 K100RT had 2 springs in each fork leg, with a plastic spacer between them. As far as I know they are original K100 type forks. I replaced the springs with stronger ones from Motorworks ( one each side ) because the originals were too soft and the bike wallowed and weaved alarmingly on bumpy bends. That improved things a lot, but I'm still careful over bumps. Its fine on smoother roads.

I've fitted K75S front suspension onto my 1987 K100RS. The ride is much firmer. One clue that your forks are of the 'S' variety is that the top retainer (where the oil fill screw goes) has a small 'S' clearly marked into the aluminium. If you've had the forks apart you'll note that there is a much longer aluminium spacer at the bottom of the fork sliders as compared to the non-sport forks. It's item 17 in this ETK illustration.

What is really interesting with the "S" forks is that only the left side has a hydraulic dampening valve (part # 13,14,15)

If water somehow got into the forks then it truly would be a dampening valve...
Otherwise the valves are just doing the best they can at damping down there in the forks.

Sorry, I couldn't resist! It's a really common mistake most people make when talking about suspension. If we are talking about water we'd use dampening, like throwing a wet blanket over a fire to smother it, and if we are talking specifically about suspension action and controlling the amplitude of oscillation we should use the word damping.

English truly can be a puzzling language at times. Do French and German also have those peculiarities of near spelling similarities with totally different meanings? I reckon it's our bastardised language which has historically glommed onto any other language for the really good words we don't have. In the end we understand what is meant.

The professor is now ready for a drink. Cheers! Prost! A Votre Sante!

Two Wheels Better wrote:Sorry, I couldn't resist! It's a really common mistake most people make when talking about suspension. If we are talking about water we'd use dampening, like throwing a wet blanket over a fire to smother it, and if we are talking specifically about suspension action and controlling the amplitude of oscillation we should use the word damping.

English truly can be a puzzling language at times. Do French and German also have those peculiarities of near spelling similarities with totally different meanings? I reckon it's our bastardised language which has historically glommed onto any other language for the really good words we don't have. In the end we understand what is meant.

The professor is now ready for a drink. Cheers! Prost! A Votre Sante!

Hey nothing is wrong to correct a mistake. I basically learned English on the street, and yes sometimes I am still using Frenglish.
I would take this opportunity to acknowledge the fact that for some of the forum members English is not their mother tongue and they make a real effort to communicate with us.

Yes, the French language has the same near spelling similarities. French are also using a lot of homonyms (words with same spelling and same pronunciation but with different meanings).


Thanks for the correction and hope you enjoyed your drink.

Bert

I was once touring in Quebec, sitting by the roadside near a small lake eating a sandwich. My old /5 Airhead was ticking away next to me as it cooled down from the hard ride. It was a beautiful, sunny Summer day. A pretty, older than me, slender woman came up the road slowly towards me with her hands clasped behind her back. She was out taking a walk and enjoying the day. 'Bonjour' she said to me with a smile. 'Bonjour' I replied with a stammer, as French is not even close to my native 'Strine. Perhaps my bonjour sounded authentic to her ear since she then spoke to me in a full sentence something about the beauty of the day, and swept her hand round in an arc to highlight her statement. I replied to her in an apologetic but very rudimentary French, that I was sorry that I did not speak French well enough to understand her. I forget now the words I used exactly, this was 25 years ago. She merely smiled, nodded knowingly and said in nearly perfect English, but with a distinct and lovely Quebecois accent, 'But what a pity, you should, you should'. I watched her pass by and disappear round the bend, then returned to my sandwich, smiling to myself and thinking of missed opportunities, of those things that I 'should do'.