Rockster Shock

[riceburner]

Has ANYONE looked at the Rockster rear shock in comparison with an R1150R shock???



I've today taken delivery of a new rear shock (from Martin Conquest), that is from an R1150R - BUT I'll be fitting it to a Rockster.

I've tried, in vain, to get information from BMW about these two items, (length, spring rates etc), but ALL they can tell me is "They're a different part number". BMW apparantly refuses to give out any further details. I've tried to look up aftermarket shock details, but the only website with online information I can find is the Ohlins site - which doesn't appear to list a rear shock for the Rockster. It DOES appear that the bikes do NOT share a front shock though.... Ohlins lists two different shocks for the two bikes: Rockster : p/n BM350, R1150R : p/n BM 050, with different stroke lengths.

So - unless anyone can categorically state that the Rockster shock is substantially different I will go ahead with my swap this weekend and become the only person in the world (outside of BMW) who actually knows the difference.

[zax1150]

hi riceburner, having fun yet again I see

If you have the rockster sport shock ...then, yes, difference ......the roadster (R1150R) std has a shorter length shock.....so handy if your having trouble reaching the ground
you can however use the Ohlins BM350 on the front & BM349 on the rear that's Ohlins rockster shocks

And yes you will strike a brick wall with BMW they don't like giving out info (very closed shop attitude ).............usually you'll get very generic info

after all the rockster is a blend of the late model R1100S (1130cc) & the Roadster (R1150R)...basically the better bits
without the fall to bits rear subframe, the pipe would have been nice tho'

[Biff's R]

riceburner,
I could tell a big difference between my old shock, and my shock from Martin Conquest. It was a great improvement for a little $.

[sweatmark]

Burner-

I'd betcha a dime to a dollar (or penny to a pound Sterling, forget the Euro) that the only difference between Roadster and Rockster rear shocks is the color of the spring, hence the different BMW part numbers. Would pull the rear shocks out of our Roadster and Rockster to prove my theory, but it's 10pm and I'm fat and lazy.

Better to just argue the following point:

The R1150R bikes share common transmission, rear subframe, Paralever parts (including the lower "strut" or arm, which I recently measured as same length on our Roadster & Rockster), wheel size, tire rolling circumference (just a SWAG on my part), and wet weight. Add all those factors up, and you get:

(1) identical geometry for the Paralever and rear shock/spring mounting points; and
(2) identical applied load on the rear springs.

With rear preload being a variable we can tinker with as mood strikes, and no rear ride height adjustment available, I'll bet the rear shock's free length and factory sag setting are identical. As for springs and damping?

OK - just measured the spring coil diameter of the bikes, not precise but best I could with a digital caliper:

Roadster lower coil dia. = 13.2mm (silver paint)
Rockster lower coil dia. = 13.7mm (white powdercoat)

I can't see far enough along the spring lengths to count coils.

Will be interested in your comparison results.

[riceburner]

Cheers guys.

Well - I "faced" the new shock up alongisde the bike last night (very inaccurate and unscientific) and it looks like it might be about 3/4" shorter - then I realised that the preload on the new shock was at minimum so wound it up and gained about 1/3" in length (unweighted obviously) so I'm thinking the new shock IS shorter, but not by a lot.

Will place them side-by-side and take piccies on the weekend.

Given that I have a GS length Paralever arm (shorter than standard), I'm hoping this new shock won't make too much difference.

Biff - I'm expecting a BIG improvement in handling yes, even though the current shock is only about 15-20,000 miles old (it was replaced early last year).


Zax - I thought the R1100S was never bored out to 1130? (1130 is the actual capacity of the 1150 bikes).

[zax1150]

God I luv meetings

Hiya riceburner

Another little dose of missdirection from the factory

BTW try looking in the Ohlins ref manual that'll give you the info you need

[zax1150]

argh!
should have mentioned that ohlins have discontinued the rear Rockster shock...
so unless old stock can be found or a friendly dealer will make one from spares....

as an alternative there's always wilbers (U.T.Y really)

[sweatmark]

should have mentioned that ohlins have discontinued the rear Rockster shock...

Strange that the Ohlins site should indicate this situation. The front and rear Ohlins shocks for Roadster have not changed specification.... perhaps it's an oversight, or they -like us- cannot get a definative answer from BMW regarding differences between Roadster and Rockster suspension components.