BMW R1200RT/R1250RT Forum

Hi, chaps. Whilst the weather is +1c i thought i would change the oil in my forks.
Questions i have are.
1. What is the standard fork oil weight?
2. Is it worth putting a higher weight in them?
3. How much oil do i need?
4. Can i use normal off the shelf oil or does have to be from BM.
The seals are OK but am going to change them anyway. Give me something to do between Xmas and New Year's day.

The Haynes manual gives the following:

1. Fork oil type: BMW telescopic fork oil (10W)

3. Fork oil capacity: R1200RT: 0.62 litre

2. Unlike conventional forks, the Telelever forks contain neither damping mechanism nor springs, only oil to lubricate the friction surfaces. The swingarm and shock absorber provide suspension control. For these reasons, can't see the point in changing the fork oil viscosity.

4. I would have thought that any good quality 10W fork oil would do the job but then again, some folks would only use OEM oils.

Fork oil eh! theres a whole discussion in itself

the "weight" is not what you go by its by the centistokes (cSt)

Most oils can be the same weight but different centistokes which means they will all behave differently

have a google if you're interested about it all

little chart here with a little info on!
http://mahonkin.com/~milktree/motorcycle/fork-oil.html

But if @David. is right in that it provides no damping affect at all then probably any 10w fork oil would be fine

Best just buy the OEM specified oil, then there is no doubt it's correct and ask what the quantity required is too.

David. wrote: ↑Thu Dec 15, 2022 9:24 pm3. Fork oil capacity: R1200RT: 0.62 litre

This capacity may not be correct, https://www.bmwsporttouring.com/topic/4 ... il-volume/

I'd suggest the OEM oil as you want to ensure it has the correct additives in it, whilst oils are listed as being this weight and that standard etc, its best to ensure that have all the bases covered in regard to corrosion protection (this would also be electrolytic cell) and seal life by ensuring it gets into the gaps in the chrome and provides a good lubricated sliding surface and of course is compatible with the seals and other materials inside the fork legs. No doubt you already know all this judging your comments on your previous life.

For a 2007 RT, Max BMW (31429062158) and RealOEM (81220432697) give different part nos. for the fork oil.
BMW seem to offer at least 4 different types and do have a habit of changing part nos.

If the Max BMW part no. is to be believed, Motorworks sell it and suggest 2 alternatives, Hyperpro & Silkolene, https://www.motorworks.co.uk/workshop-s ... forks.html

I'd ring the BMW dealer, give them the VIN (last 7 digits) to ensure the correct oil is purchased. Then ask the workshop guys what quantity is required.

Although the forks on an RT don't provide conventional spring & valve suspension, the fact that Motorworks offer alternative oils may indicate that there is nothing fancy about the BMW OEM oil.

Found this video:



Although not exactly the same as an RT, it gives a good idea of the procedure required.
In bold text, the Haynes manual says, "Note: Do not loosen the bolt in the bottom of the slider - it is not a drain plug."

I thought it was interesting to see how the fork tube and slider are not connected together other than via the top & bottom yokes.

David. wrote: ↑Fri Dec 16, 2022 10:05 am Found this video:



Although not exactly the same as an RT, it gives a good idea of the procedure required.
In bold text, the Haynes manual says, "Note: Do not loosen the bolt in the bottom of the slider - it is not a drain plug."

I thought it was interesting to see how the fork tube and slider are not connected together other than via the top & bottom yokes.

Seen that video. From what ive seen from a GS owner on YT, The tubes can be removed without removing the legs.

Doctor T wrote: ↑Fri Dec 16, 2022 6:36 pmThe tubes can be removed without removing the legs.

Interesting but the fork oil or seals weren't replaced.

Making use of the air bleed screw would have helped when removing (vacuum) and replacing (pressure) the fork tube in the slider.

That's in PT2 here

Doctor T wrote: ↑Fri Dec 16, 2022 8:41 pmThat's in PT2 here.

Looks less messy to remove the forks from the bike. Interesting that ~650ml of oil is added which is far too much and goes over the top. This was also the case as posted above in the link to the BMWSportTouring RT thread. I see that on this occasion, the air bleed screw is used. It also shows that there is only one bush being lubricated between the fork tube and slider.

Perhaps because the GS has longer forks they do require 650ml compared to 450ml on an RT. Luckily ive found 2 sealed bottles of 10W Hyperpro in the garage. Must have been left over from a project that my son was working on.
This may sound stupid but these sealed bottles have been laying about for about 4/5 years. Never having to store oil over a long period before, would the temperature in the garage deteriorate in the oil?.
Researching the forks i did find an article from a Turkish shop that said that even thou the forks have no springs, the oil does give slight compression to the suspension. Also found out that the 310 range has only one spring in the forks. The left side has just oil. This is used for compression. Never heard of this on "normal" forks before.
Ordered a fork kit but the shop can't guarantee delivery before or between the Xmax /New year time. No problem as i can give the bike an annual service in that time.

Doctor T wrote: ↑Sat Dec 17, 2022 11:05 amPerhaps the GS having longer forks they do require 650ml compared to 460ml on a RT.

In the PT2 video, at 10:45 the guy tries to put 500ml of oil in, at this point it's too much and overflows.

In the R1200GS.info forum, it states 650ml for the forks but look elsewhere they say 500ml. Gets confusing the more you search

Doctor T wrote: ↑Sat Dec 17, 2022 11:05 amThis may sound stupid but these sealed bottles have been laying about for about 4/5 years.
Never having to store oil over a long period before, would the temperature in the garage deteriorate the oil.

IMO, the oil is likely to be just fine. How long has the oil been open in the forks.

However, if there is any doubt, why not purchase some new for ~£10 to £15.

Hyperpro, https://www.motorworks.co.uk/fork-oil-oia00012-1.html

Smith and Allan, https://www.ebay.co.uk/itm/300871185373 ... Swrg5cwEFB now we know you use their oils.

If this is the correct BMW OEM oil, it's not a bad price, https://www.motorworks.co.uk/bmw-fork-o ... 158-1.html