Slabside shock for drag strip

[TiZiK]

Looking for shock options for slabby 1100.  Built for drag racing.  Running appx 68" wheelbase.  Bike has a turbo as well.

What are some shock options that work well for the strip?

I know some R1 and R6 shocks are pretty much direct swaps.  Any other options?

 

[Gixer1460]

Forget using std. OEM shocks if it is a 'single purpose bike' A dragbike shock needs a stiffer spring, a decent amount of compression damping and loads of rebound damping . . . . . . the last requirement is where all OEM shocks fail!

Just phone Hagon - tell them what you have, what application, weights and arm length etc. and they'll build you a shock that will be 80 - 90% spot on!

[Arttu]

Pretty much as said above. It's very ulikely that any OEM shock just thrown in would work even half decent way.

Long swingarm means that you will need stiffer spring just to compensate linkage ratio change. Then in drag racing rebound of the shock needs to be very slow compared to any other usage. So combined with stiffer spring this means you need really stiff rebound damping. Compression damping probably can be quite normal.

So I would say you have basically two options:

• Get some shock that is specifically made for drag racing. Like Penske or M2. These are either built to your specs like weight, swingarm length etc. or they have wide enough adjustments to cater most of the cases.
• Get some rebuildable and adjustable "normal" shock like Öhlins, WP etc. Then find some shock specialist that understands what is needed in this application and can rebuild the valving to get suitable damping.

[TiZiK]

Thanks Gents.  I was afraid of that  Mainly for cost purposes but we all know going fast is not cheap.

As it stands, the bike currently has a Fox Racing shock.  I picked it up years ago in a parts lot.  Not sure what bike its originally from but I think I recall it being a 750 shock.  I'm trying to get model info but the net is scarce on info regarding older Fox shocks.  It has a blue adjustor ring just above the bottom mount.  I'm guessing thats rebound and it has a red dial on the remote canister, compression I'm assuming.  

If I can get some info on this thing, I'll dis-assemble and revalve the rebound shim stack to slow it down some.

My R6 streetfighter has a Penske Rear shock as well, if thats a viable option, I'll swap that out for the stock unit as it doesn't see the street much anymore.

[Arttu]

If you can do rebuild and revalve I guess you can get it quite good after a couple of trial-and-error rounds. That's always one option if you want go fast without spending much money

For reference here is one quite good video that should give you some idea what you want to achieve with the rear shock.

 

[TiZiK]

Thanks Arttu for that link.  It was actually really helpful.

So I did a quick test on the fox shock.  I pulled all preload off the spring, backed off the compression and turned rebound to max.  Well, I think this shock is more than adequate.  At those settings, It takes almost a full minute to revert back to its original height.  Took a few turns out of the rebound and it currently rebounds at the same rate as the s1000rr in Brocks video.  About 3 seconds to revert to original position.  As I'm all of 160 lbs, I think I will need a lighter spring as I can only get it to squat around 2 inches (measured from the swingarm to the very back tip of the subframe)

I guess the best thing to take away is that the valving is up to the task.

Thanks again Gents for the replies.  Sometimes I just need to talk it out with others who can offer a different point of view.

 

Cheers!

George  

[Nik]

What's your rider sag? Note that preload doesn't change the stiffness, but only raises or lowers the rear (unleas you put on excessive preload so all rider sag is gone). 

[Arttu]

7 hours ago, TiZiK said:

Thanks Arttu for that link.  It was actually really helpful.

So I did a quick test on the fox shock.  I pulled all preload off the spring, backed off the compression and turned rebound to max.  Well, I think this shock is more than adequate.  At those settings, It takes almost a full minute to revert back to its original height.  Took a few turns out of the rebound and it currently rebounds at the same rate as the s1000rr in Brocks video.  About 3 seconds to revert to original position.  As I'm all of 160 lbs, I think I will need a lighter spring as I can only get it to squat around 2 inches (measured from the swingarm to the very back tip of the subframe)

I guess the best thing to take away is that the valving is up to the task.

Thanks again Gents for the replies.  Sometimes I just need to talk it out with others who can offer a different point of view.

It's actually pretty much best info about drag shock adjusting that I have found on the net. And lines up quite well with my personal experience.

Sounds like you can at least start testing with that shock. Finding a correct spring may require some experimenting too since it's slightly different game than for a road bike. For example amount of power and how quick you are going affects to selection too.

If you have a data logging system I highly recommend getting a shock travel sensor. That helps a lot for finding working setup. Without logging you can try to be creative For example install some pointer showing the shock position and put a GoPro filming it during a run. Or at minimum get a friend to film your launches so you can see how the back end reacts.

[Gixer1460]

I think you'll be surprised how stiff the shock / spring has to be! I've seen bikes so stiff that they hardly moved doing the seat bump test but on launch, they squatted so much that the tyre rubbed and the chain looked like it had 10 extra links in the lower run! Just think, Brock Davidson was the first guy in the 7's on a 'streetbike' in the 90's, so he has shedloads of experience and by his own admission, it took a year of making hits to get the shock right - that's maybe 5 - 10 passes / day, 3 or 4 times a week ! ! ! Its a long arduous task, so get the engine and clutch how you want them first, then don't touch them as changes there will affect how the bike launches - if you need to concentrate on the shock, you need repeatability from everything else - just IMHO!