R100R forks onto 1991 R100RT Mono

[Pento]

Has anyone done this conversion? My RT forks are sticking and stancions and sliders are scored. Is upgrade to R100R 41mm forks feasible? Any pics/photos? Would like to keep Y spoke wheel. What brakes will work? Apologies, no German and relying on Google: D

[Alfons]

Hi Pento,

welcome to the asylum! Here it is customary to start with a short introduction about oneself, so it would be very kind of you to tell us something about the rider and the bike.
As regards your question, I can tell you that this conversion is almost a "plug and play" one:

The R 100R forks can be used without any problems: The steering head bearings are the same size, the Y-spoke front wheel can be used along with the R100R brake discs and the R 100R four-pot calipers. For the brakes a 15mm master cylinder is required, but you cannot use the one from an R 100R (different design of the handlebar mount).
You might want to try different front mudguards as the R 100R type does not look particularly elegant.
Along with that you will have to find a solution to mount the instrument cluster as the R 100R top yoke does not accommodate the Monolever-type instrument bracket.

Does this help?

best wishes

Alfons

[Pento]

Hi Alfonso, forgive my bad manners. I'm a 56 yr old father of four, engineering manager, into old Mercedes, music ,song writing, education and mediation. I got the RT in San Diego CA when over for work in 1997. Have not used it much but after the forks seals leaked I refurbished the existing forks but they started sticking. Could be my setup but I observed a lot of scoring on the end of the stancions and inside the sliders which did not look right. I suspect the forks are not original. I have some time now to get it right and found a set of forks in West Cork ,R100R, from a project that was cancelled. I'm undecided whether I should keep the RT standard and replace the forks with good second-hand ones or go for the upgrade to the 41mm R100R. Would like to hear from anyone who has done this conversion and what was involved or opinions to stay original.The R100R forks do not have brakes with them. I also have to refurbish the 32mm Bing carbs as needles and jets are corroded from hummed up petrol. Thanks for any advice.
Best regards

Mark (suitable case for treatment...)

[Alfons]

Hello Mark,

the sliders and stanchions on the original Monolever fork may well be worn out due to the inevitable wear and tear, but also due to damage, neglect and bad servicing by previous owners. These forks were designed an manufactured in the 1980s. They still work sufficiently if maintained properly, but the Paralever forks from the 1990s are superior in every aspect: The damping system is supposed to be much more sensitive, the stanchions are 41mm and they do not wear out the sliders.

I am currently working on a Monolever which has received such an R 100R fork, but the bike has not been launched yet (still waiting for the body parts to be painted). In a few weeks I will be able to provide first-hand information .

What I can tell you right now is that

- the Y-spoke wheel and the Monolever front axle fit perfectly

- the Monolever brake calipers fit perfectly (However, my bike has the R 100R brake disks, so you have to check whether the Monolever brake disks have the necessary offset

- you can also use the R100R four-pot calipers (along with a 15mm master cylinder)

If you are not keen on riding a bike that is 100% original, I would suggest using the R 100R forks.

best wishes

Alfons

[dreiradbertl]

Hi,

Keep in mind the R forks are longer (approx. 15 - 18 mm), and offer less travel than the RT's. Even if you could slide the stanchions upwards, the handlebars are in its way.

So R forks are perfect for Scramblers (where you love to rise the bike a bit) or cofferacers and the use of clip-ons.

Brake discs are identical, but the hub (aka the width between the flanges) is the Y cast wheel 2mm less than the R spoke hub, which can be equalized by the use of that stainless left side cover on the GS single disc setup.

Herbert