Paralever adjustable strut questions

[Xjskins]

Ram shox/ram engineering/realm engineering/ other company name have produced an adjustable paralever strut that is a good portion cheaper that the one or two others on the market. 

From my limited understanding you would use this for 2 reasons: 1) to raise or lower the seat according to your inseam and/or 2) change the handling characteristics.

So my questions are as follows:
1)How, if at all, does this effect the rear spring rate?
2)Say a person wanted to purchase a new shock, should they mention that they have this installed and in which manner (raised or lowered seat height)?
3)How does this compare with purchasing a shorter shockif your goal is to lower the seat?
4)Can it be used in tandem (jack the the strut for handling improvement but short shock to maintain ride height or lower the bike +/- 2")?

Cheers

Rick

[rbm]

I'm going to weigh in but should mention that I'm not a suspension expert.  I invite other more knowledgeable persons to criticize my argument.

I think the most practical use of the adjustable strut from Realm is to compensate for a shorter shock.  Essentially, its use would be your #4, to compensate for a shorter shock than stock.  To quote from Anton Largiader's web page on paralever analysis,

The Paralever suspension was introduced on the 1988 R80GS and R100GS, then used on the 4-valve K and Oilhead bikes (except the R1200C). Whereas the original Monolever system had a single pivot at the front of the swingarm, like most motorcycles, the Paralever uses two links to connect the rear drive to the transmission. This is a "Four-bar" linkage, similar to double-wishbone suspension in cars which keeps the rear drive at a constant angle as the suspension moves.
...
The Paralever drive unit, on the other hand, does not rotate as the suspension moves up and down - it stays at the same angle as the chassis because of the parallel links. Since there is no direct relationship between vertical suspension movement and drive unit rotation, the torque of the wheel does NOT result in suspension movement. This, in a nutshell, is what the Paralever is about.
...
The intent of the Paralever is to create a longer effective swingarm (with this length determining the amount of rotation that the final drive experiences as the suspension moves).  Making a perfect parallelogram creates a swingarm of infinite length, as far as any shaft-jacking effects go, with no rotation of the rear drive at all.

If one shorten's the shock and retains the OEM Paralever strut, the position of the final drive at the resting position with correctly set sag will render the major axis of the final drive non-parallel with the ground, thus moving the contact patch of the tire rearwards and increasing the wheelbase.  The adjustable strut can be shortened, restoring the parallelness of the final drive, move the contact patch forward and restore the stock wheelbase.

So, to answer your questions:
1: The spring rate is not affected by installing the adjustable strut.
2: Can't comment on this.  I think your shock selection is dependant on your goals.
3: The shorter shock will lower the rear end which will lower the seat height, along with change the bike's geometry and handling.
4: See above.

[Martin]

 Rick why do you want to change the shock, is it just because of the height or do you wish to modify the handling ( You really should leave that to experts ). And if you really don't want to modify your bike, raise the rider. Buy a pair of boots with the thickest soles you can find, this can give you up to 1" plus. If you want more height buy a pair of shoe lifts,this can give you another 1" plus. If you go the lift route buy them first and try them in the boots before you buy them. Easier to make short people taller than tall people shorter. Unless you have a chainsaw.
Regards Martin.

[Xjskins]

Martin,

I need to change the shock out as the one that is on it now is toast.  Been looking at replacements and came across this strut thing, having troubles figuring out why anyone would need it.  But, yes I am short.  I shaved the stock seat down on the side so that I could get my feet down enough to feel comfortable as a new rider.

RBM to summarize and add my thought on yours:

If you had a OEM short shock and shortened the strut, it would move the lower shock mount back, increasing the distance between shock mount points thus lowering the seat, but also increasing the angle of the shock. 

If you had a OEM or short shock and lengthened the strut, it would move the lower shock mount forward, decreasing the distance between the shock mount points thus raising the seat, and decreasing the angle of the shock.

Would not either scenario not affect how the shock preforms? 

The change in handling would really only come from the fact that you would be changing the head/fork angle, correct?

oem shock + short strut = lower seat height and lazy steering (my term for increasing (old school chopper) fork/head angle)
oem shock + long strut = raised seat height and quick steering
short shock + short strut = way low seat height and really lazy steering
Short shocK + Long strut = no change (lighter pockets)

Am I correct in understanding that this is only good for tall people that should have bought a crotch rocket or someone that is doing a cruizerish instead of a cafe conversion.

Really just thinking out load and in need of a sounding board
Thanks

[Martin]

Rick I have no experience with K1100 suspension, only short riders. Somebody in brickland will probably be able to help you. If you put in what your trying to actually achieve you will probably get an answer.
Good luck Martin.

[rbm]

If you had a OEM short shock and shortened the strut, it would move the lower shock mount back, increasing the distance between shock mount points thus lowering the seat, but also increasing the angle of the shock. 

If you had a OEM or short shock and lengthened the strut, it would move the lower shock mount forward, decreasing the distance between the shock mount points thus raising the seat, and decreasing the angle of the shock.
Would not either scenario not affect how the shock preforms? 

Setting dynamic sag on the rear will determine the seat height.  Shock and strut length should not matter as much as spring rate, preload, bike weight and rider weight.  The shock will still perform as designed at any angle.

The change in handling would really only come from the fact that you would be changing the head/fork angle, correct?
oem shock + short strut = lower seat height and lazy steering (my term for increasing (old school chopper) fork/head angle)
oem shock + long strut = raised seat height and quick steering
short shock + short strut = way low seat height and really lazy steering
Short shocK + Long strut = no change (lighter pockets)

Change in handling will come with changes to the wheelbase that results in changes to the front and rear trail numbers.
- Short shock + OEM strut = increased front trail = less responsive steering
- Standard shock + short strut = decreased front trail = more twitchy steering

There may also be changes to the anti-squat angle because of changes to the rear trail, resulting in changes to the handling of the bike.

You can counter the changes to the rear end through introduction of a shorter shock with OEM strut by raising the stanchions in the triple tree.  Raise the stanchions enough to counter the increase in front trail.  This will lower the overall stance of the chassis.  However, this will require changes to the front fork preload to compensate and possibly changes to the front spring rate.

Everything is interrelated, and some are overlapping.  It would be good to get ahold of books like "Motorcycle Handling and Chassis Design" by Tony Foale or "Race Tech's Motorcycle Suspension Bible" by Paul Thede & Lee Parks.