rear shock angles

whats the deal with laying the shocks over?
seen this a few times, mostly on SANCTUARY bikes and older MORIWAKI superbikes.
The moriwaki bikes ran a REALLY LONG shock body that mounts UNDER the swingarm through a hole.
One of the sanctuary bikes (RCM-047) has a lot of work put into the shock mount area with triangulation,etc. Japs love their twin shocks.
I understand the longer shock bit.... better ability to transfer heat, better damping control,etc. but what is the significance of the extra included angle?

On my build the MACINTOSH swinger (from New Zealand) has 3 options for lower shock mount. I can't remember any real difference in use..was 20 years ago though.

We had a fairly lengthy discussion about this on a different forum (Mark may chime in). Laying the shock down by moving the top mounts forward allows increased wheel travel (for the same length shock) and makes shock compression more progressive so you can run a stiffer shock while retaining a softer initial feel. Moving the lower shock mount back would have the opposite effect and is more of a drag race modification.

they use this jig to make sure they are in the right place.




beyond that i am of no help. :whistle:

leon

As an example, on my KZ1000, I run a GS1100e swingarm that sets the lower mounts back about 1.5 inches.I use the stock upper mount. Hagon built me a set of HD shocks with GS lowere mounts and KZ uppers. As I occasionally run the bike at the strip, I was more concerned with rear wheel hop and chassis rigidity than I was ride.The bike rides a bit stiff,but hooks up great at the strip and corners well on the twisties.The stock KZ shock mounts are almost perpendicular while mine are about 75 degrees.The bike has about a 2 inch lower seat height as well.Rear wheel travel is more than adequate,even with 2 up.Hope this helps.bj

Thanks for the pics Leon, I am gearing up to do mine as soon as I have my box swingarm finished. I was going to make an alignment jig too but that thing is a monster, jeez... :laugh: I'm going to make a simple small jig that slips over the stock mounts with a drill guide for the new mounts.

What bj says confirms what I wrote previously, moving the lower mount rearwards makes a stock (soft) shock feel firmer and decreases ride height and wheel travel, the opposite of what you want for road racing.

Shock angle actually REDUCES spring rate.

It makes it more progressive because if the shock is angled over more, the swingarm leverage ratio actually changes (more) though the stroke of the suspension.

It is a way to get a more progressive suspension with a link-less suspension setup.

Yes but only if you move the shock mounts towards the fulcrum point not away from it, otherwise the decreased leverage on the shock will negate the reduction in spring rate.

Thanks guy, I searched Tony Foale,etc with no luck. some assbandit has stolen my phil irving book.
Just as i suspected, leverage angles and looking at the old 'arm the shock was bolted in the bottom rearmost position. I dragged the bike and i think the next owner had a go too. You can see the rim locks in rear rim...this bike used to hook up good with a 170/60 in back. has a tall 160 in at present.

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531blackbanshee wrote:

they use this jig to make sure they are in the right place.

beyond that i am of no help. :whistle:

leon

oh that poor z1 frame,my god im starting to sound like one of those damn model A restorers! :woohoo:

This on my 550, the original location was where the "O' is drawn. The shock angle changed about 10 degrees. I hope it improves the geometry, but I admit that I did mostly for cosmetics. To my eye piggyback shocks look better at an angle greater than stock.

dutchz wrote: Yes but only if you move the shock mounts towards the fulcrum point not away from it, otherwise the decreased leverage on the shock will negate the reduction in spring rate.

It can get complicated!:laugh:

boyracer wrote: whats the deal with laying the shocks over?...but what is the significance of the extra included angle?....

May be demonstrated with aftermarket accessory "lowering blocks" which move the lower mount rearward about 2 inches and results in the same shocks proving a ride almost as stiff as struts.

At more severe angles, the suspension action begins trying to bend the shocks more than just compressing them.

Good Fortune!