Rear Shock 1100GS question regarding original

[Bikergary]

There has been much talk about Ohlins and such, but have to say I can't get on with it, When i first bought the shock second hand, it didn't seem to work properly, had it rebuilt with stiffer spring (£180) and still can't get on with it (not enough damping it feels like at low speed - there's 2 damping settings though neither can be altered by rider/owner) so I am thinking of another solution instead of chassing around with my cheque book.

Has anyone replaced their old original Shock with a new BMW Shock? if so how did it compare. I have been quoted £335 +vat for a new replacement rear shock.

 

[Possu]

Gary,

You're not that big, not sure you needed a stiffer spring?

Adjust Preload & damping to minimum,

Increase Preload so reduce Static Sag - not sure of the figure, I tend to go by feel on the road.

Set Damping to 1/3 the number of clicks & increase setting if it wallows on corners.

If the springs too stiff for your weight, the rear will kick up even on minimal preload.

 

[Bikergary]

thanks... Problem is finding a happy medium, I'm 17st, but ride either solo, with passenger, luggage or all 3, so it was recomeneded to get heavyier spring.

"If the springs too stiff for your weight, the rear will kick up even on minimal "
what causes this how can it prevented?

Gary,

You're not that big, not sure you needed a stiffer spring?

Adjust Preload & damping to minimum,

Increase Preload so reduce Static Sag - not sure of the figure, I tend to go by feel on the road.

Set Damping to 1/3 the number of clicks & increase setting if it wallows on corners.

If the springs too stiff for your weight, the rear will kick up even on minimal preload.

 

[Alex]

"If the springs too stiff for your weight, the rear will kick up even on minimal "
what causes this how can it prevented?

Physics. It is a spring. The spring after being compressed will tend to retain its original shape. If you are not heavy enough it will do so in a violent manner, thus kicking up the rear of the bike. If you are heavier, your weight resists the springs force and thus the spring returns to its original shape in a slower more controlled manner.
The preload adjuster in BMWs is so that you can adjust the spring stiffness according and the payload of the bike.

In my old 1100 I never replaced the rear shock, although after 9 years and 70000 miles it's performance was marginally sufficient. New BMW shocks are usually up to scratch, but you have to remember that suspension settings are very much a matter of circumstances and personal taste.

 

[Bikergary]

Physics. It is a spring. The spring after being compressed will tend to retain its original shape. If you are not heavy enough it will do so in a violent manner, thus kicking up the rear of the bike. If you are heavier, your weight resists the springs force and thus the spring returns to its original shape in a slower more controlled manner.

Isn't this controlled by the rebound Damping?

The preload adjuster in BMWs is so that you can adjust the spring stiffness according and the payload of the bike.

But I take it, all it does is adjust the spring, and not the damping as well, like on my old TDM.

In my old 1100 I never replaced the rear shock, although after 9 years and 70000 miles it's performance was marginally sufficient. New BMW shocks are usually up to scratch, but you have to remember that suspension settings are very much a matter of circumstances and personal taste.

I guess I havn't riden a GS with a Standard Shock that wasn't all ready tired. I liked my original, the only reason I changed mine was it had done 45k when I bought the bike, and it couldn't support me, passenger and camping kit, the back sagged.

 

[Alex]

Sorry double post

 

[Alex]

Isn't this controlled by the rebound Damping?

You're right, it is. I was only trying to simplify thing by leaving rebound damping out of this. The two factors involved are rebound damping and your weight. Assuming you can or will not modify rebound damping, then the only factor is weight.

But I take it, all it does is adjust the spring, and not the damping as well, like on my old TDM.

You're right here as well. It only adjusts the preload of the spring.

I guess I havn't riden a GS with a Standard Shock that wasn't all ready tired. I liked my original, the only reason I changed mine was it had done 45k when I bought the bike, and it couldn't support me, passenger and camping kit, the back sagged.

New BMW shocks tend to be fairly stiff. The one on my adventure is on the standard preload setting and feels stiff enough when riding solo. On the hard setting it is ok two up with panniers. Not great but ok.

Ohlins shocks usually are much stiffer than BMW ones even when new. Maybe the Ohlins you bought had been rebuilt by the previous owner, modifying its internals to make it softer and thus provide less rebound damping. Maybe the spring is not the culprit but the shock itself is.

 

[Possu]

Stiffer spring needs more weight/force to compress it. If you've got the bike set up permanently for your weight, pillion & luggage, it's going to be too stiff when riding alone with no luggage.

Hit a bump & the springs to stiff to compress. The rear will kick up as if you're riding a hard tailed bike.

Damping controls the speed of the springs movement i.e it damps it.

Sounds as if you need a spring that is fine for you when on the lowest preload setting (when riding alone with no luggage). You can then wind up the preload to cater for pillion and/or luggage.

I've seen a couple of aftermarket shocks where the uncompressed spring protruded past the top of the preload threads on the shock body by 1" or more. This meant that a spring compressor was needed to compress the spring just to be able to get the preload rings onto the threads. This resulted in a shock that even when set to minimal preload, was already subject to a reasonable amount of preload & this could not be reduced. If this is the case with yours, get a suitably shorter spring. Don't go too short on the spring or it will be coil bound on maximum travel & will result in that hard tailed kicking up feeling.

To stiff a spring or too much preload will also lead to increased tyre wear & make the rear tyre prone to sliding out from under you if riding hard in the wet.

If you need a hand. let me know, I'm only in Oxford.

 

[Strand-Wolf]

I fitted another OE BMW shock. Cheaper than anything else and perfectly ok. doddle to fit and adjust.

 

[Bikergary]

I fitted another OE BMW shock. Cheaper than anything else and perfectly ok. doddle to fit and adjust.

Did you fit a new one or second hand?

 

[Bikergary]

Steve: Don't have a problem about compressing the spring, it is stiffer than the old, but it always seems to be on the move, so i guess it's the damping, maybe too soft, which of course can't adjust.

It has been to Ohlins for a service recently, which is when they put a heavier spring, and I did say I wanted the damping stiffer as i seem to be able to push the back down with one finger, but I also mentioned I prefered a softer ride, now wheather that means they have done something very strange with the Settings, I know the old one was pretty knackered. and with all these settings, I either want one that you can adjust both preload, rebound and damping or one that is bog standard that I can adjust preload when I have passengers.

I guess I just havn'e tried this bike on a standard, good condition shock so have nothing to compare as such.

 

[sproggy]

...i guess it's the damping, maybe too soft, which of course can't adjust...

The 46DRS, Ohlins' recommendation for both 1100 and 1150, does have rebound damping adjustment (the large black plastic 'nut' at the bottom of the unit) so unless you've got the wrong unit fitted or are talking about the front rather than rear of the bike you can adjust the rebound damping easily.

Kicking off bumps sounds like excessive preload or an excessively stiff spring as Steve said, otherwise (less likely) excesive compression damping could cause the same thing and on a DRS it's not adjustable by the owner, only during build/rebuild. If your compression damping is excessive you should take the unit back to whoever rebuilt it and ask them to change it.

 

[Bikergary]

The 46DRS, Ohlins' recommendation for both 1100 and 1150, does have rebound damping adjustment (the large black plastic 'nut' at the bottom of the unit) so unless you've got the wrong unit fitted or are talking about the front rather than rear of the bike you can adjust the rebound damping easily.

It is the 46DRS, it's the Damping i was refering to that you can't adjust, the rebound I been adjusting to stop the wallowing

Kicking off bumps sounds like excessive preload or an excessively stiff spring as Steve said, otherwise (less likely) excesive compression damping could cause the same thing and on a DRS it's not adjustable by the owner, only during build/rebuild. If your compression damping is excessive you should take the unit back to whoever rebuilt it and ask them to change it.

Preload is about half way for me (16stonne ish) I'll take my willing passenger out and use her as a guiney pig again see if it kicks up when she is on it, saying that I did manage to bottom it out on a dip with her on it with preload set half way which all makes me think the compression damping is too soft, and the spring is too hard. Is it possible to swap the springs yourself (as i have the original spring still)?

 

[sproggy]

It is the 46DRS, it's the Damping i was refering to that you can't adjust, the rebound I been adjusting to stop the wallowing

I think there's a communication problem here! 'Damping' is either of the rebound or compression variety. You have been adjusting rebound damping, compression damping can't be adjusted on the bike. There isn't a general 'damping' adjustment.

Preload is about half way for me (16stonne ish) I'll take my willing passenger out and use her as a guiney pig again see if it kicks up when she is on it, saying that I did manage to bottom it out on a dip with her on it with preload set half way which all makes me think the compression damping is too soft, and the spring is too hard.

I don't think so. If the spring is capable of bottoming out at all then either you have too light a spring or you have the preload set too low (probably the a latter) - the spring can't possibly be too hard if this happens. If it doesn't 'kick' when you ride solo but it does when you have a pillion (and given your other comments) then the kicking is likely to be the shock bottoming out and nothing to do with damping at all. Up the preload significantly and try again.

Compression damping (as someone else said) controls the rate at which the spring compresses, not the amount it compresses.