PE175 - '82-'84 Full Floater vs '80-'81 twin shock?

[Chuck78]

I'm looking to buy a PE175 and sell my '74 Rickman VR 250 MX.  Definitely looking for the more powerful 80-84 PE175 engine, for more power, and for ease of obtaining replacement pistons... Also wanting the newer 175 for the chassis revisions and the aluminum swingarms of course. 

I'm a vintage and twin shock guy.  My buddy has a Full Floater '84 PE175, and he hangs with us on the most technical terrain we ride with no problems even with everyone else on more modern bikes.  An old timer enduro racer was for a long time singing to me the praises of how great the Full Floater PE175 was in the handling/capabilities department.  

The 38mm forks, thicker and longer travel, certainly will really help give an edge to the handling. The monoshock obviously was the wave of the future, and Suzuki nailed the functionality standpoint of the Full Floater rear end, despite any criticisms for all the extra linkage parts "looking" odd. 

The 80-81 has more laid down shocks than the 78-79, and a nice aluminum swingarm as well as a lot of other great features for it's time.  I'm really wondering how "capable" a good set up 80-81 PE175 with a nice set of dialed in long travel Fox Shox on it (perhaps a hair longer than stock even) would do on the really rugged stuff vs the Full Floater '82-'84??

Has anyone ridden these to be able to make a good direct comparison?  Keeping in mind I'm interested in the final results with nice aftermarket twin shocks vs a rebuilt/good condition Full Floater 175 setup.

Thanks!

Chuck L

[Chuck78]

I've done a bit of reading, & it seems that a whole lot of people consider the Suzuki Full Floaters to be one of the all time best rear suspension configurations, due to the floating shock/bellcrank, and the angles of the linkages. Apparently this allows a very soft plush supple initial travel, but a nice linear soft progressive rising rate under more and more travel. As well as the ability to allow the rear to drop the wheel down into holes in the terrain and then very softly suck the impact back up when travelling past that hole, yet on big hits deep into the travel range, the rate stiffens appropriately.

Most people seem to think Suzuki eventually dropped the design because it was too complicated, too many moving/wear parts, but apparently the design was based on someone else's theories, & Suzuki abandoned it due to pending legal litigations.
The end of this forum thread sums it up extremely well:
thumpertalk.com/forums/topic/97026-full-floater-suspension-design-vs-tuning/

[Chuck78]

From the ThumperTalk link:

Borneo biker
Posted March 22, 2017
just some thoughts.. not 100% on the accuracy.. more of an observation.

I think part of the reason it works so well is that it combines multiple classes of levers working in a compound manner, optimum angles and maximizes the shock spring length. The longer the shock spring, the more supple that spring can be in the initial stages of compression.(fact??)

The full floater (FF) set up uses multiple classes of levers in their near to optimum arrangement. Most suspension set ups have a class 2 lever in that the wheel end is the force applied and the swing arm (SA) pivot is the fulcrum, and the load (shock spring/motorcycle weight) is the resistance to that movement which is placed between the SA pivot and the force.

Where the FF differs is that in addition to the class 2 lever above, the entire unit is also working as a multiple compound of levers whilst in motion. The SA link rods that “push” up the upper link (class 1 lever) go through a varying degree of angle, which in turn has added rising rate benefits. As the angle between the upper lever and those rods progressively moves closer to 90 degrees from swing arm, the rate rises. So there in that section of the arrangement, there is already a dual rising rate function. Firstly the leverage ratio of the upper lever and secondly the angle at which the force is applied to that lever. Additionally, if the wheel drops into a hole, and the SA lowers accordingly, the angle between the SA and the push rods narrows further. This allows for very supple movement from the extreme limit of travel since the angle of the arms to SA has closed up. This provides a soft rate rising through a long stroke. Another benefit of the FF arrangement is in a deep hole. The shock spring is exerting force directly to the SA via lower shock mount, plus via the upper lever and push rods which are now “pushing” the SA downwards mid way along the SA. This is easier for the spring to ‘move’ the wheel down since it is pushing the SA half way along its length in addition to the forward end of the SA at lower shock mount. (or is it negated by the levers???)

The upper control lever that compresses shock, being a class 1 lever, applies a long sweep of travel to move the load a small distance. Again, very progressive and uses the angle to maximal effect. The angle of that lever at rest is far (less) than 90deg. At the top of its movement, it has reached almost 90 deg. This is very much optimised for rising rate. The competition can’t achieve this with short linkages and short shock lengths.

Thirdly, the long shock allows a long spring that can allow soft resistance to small bumps that will rapidly ramp up the rising rate through all the above mentioned motions. The upward movement of the SA assembly is moving the lower end of the shock towards the lever compressing end at top simultaneously which further adds to the rising rate progression. I think that these actions provide long supple wheel motions rapidly rising in a "hook type curve" towards the upper end of progression.

All these actions/levers working in unison provide a far greater level of “ideal” rising rate. Most all of the competition can manage to produce a rising rate suspension. It’s the nature of the rising rate that really differs with the FF. The genius of the design has yet to be matched by anyone.

The manufacturers will tell us that “their” system is better in some way or another, but real reason the FF left us too early was because of litigation. Suzuki stole that invention from Don Richardson and once they were found liable, dropped it.

lowmass
Posted July 17, 2017
All I know was the full float system was the best rear suspension I have ever ridden. What impressed me the most was its square edge bump absorption. Almost magical and far better than any I have ridden

brufnus
Posted May 16, 2015 

The real benefit of the Full Floater suspension is the fact that the bellcrank's angle changes as the shock absorber is being compressed, which in turn make the shock absorber compress progressively.

When encountering small bumps, it's rather soft - but as the bumps become bigger, the travel of the shock absorber increases even more.

I still remember how amazed I was with the bike's suspension the first time I drove it - especially the Full Floater suspension made a huge impression on me. c",)