Let the fun begin...RPM Rear Shock

[weymouth399]

Well, I have, in my hands the first RPM rear shock to start testing.



Fitment will be started today and then testing should start this weekend. This is the early model shock and the late model is supposed to be be shipped by the end of the week. If so, that one will be fitted by next weekend and the testing will begin on that one as well.

There will be several thousand miles put on the shocks with changes to valving completed, spring rates tested and settings fine tuned.

Since we still have a couple of months of good weather before winter really hits, we should not have much trouble getting the testing completed, the changes made and the production started.

It has been a long time waiting and I believe the results will be worth the wait.

Randy - RPM

Randy that shock looks to fit, the years of the best looking FJs. Your not bias are you, just funny how it happens to fit BOTH your bikes.
If you need NE roads tested let me know, I have one it will fit too.

Bob W

[The General]

Its like an addiction: we´re still considering and saving to buy the fork valves and there is another gadget on the way...

MMMMmmmmmmm  Randy, do you know that there is an economic crisis and that you could be the guilty of lots of divorces?   

I just heard a classic understatement by a country bloke west of here.     "SHED HAPPENS"

bring it oooonnnnnnnnn, Randy 

[SlowOldGuy]

Randy,
Sorry if I struck a nerve.  It was not my intent to question the technology.  Since I haven't had the opportunity to install my fork valves yet, my old school brain is still trying to comprehend the one-size-fits-all capability that the inertia valve offers.

Ride height would be nice to have on the early model unit.

DavidR.

[fj11.5]

dam, , starting a new list now , , fork valves , fork brace , more pods, annnnnd a rear shock so Im not using a Honda part 

[big r]

I WANT ONE!!!!!! Please hurry up and get it tested, I need badly mine is bagged and isn't much better than a pogo stick. Big R

[racerrad8]

Randy,
Sorry if I struck a nerve.  It was not my intent to question the technology.  Since I haven't had the opportunity to install my fork valves yet, my old school brain is still trying to comprehend the one-size-fits-all capability that the inertia valve offers.

Ride height would be nice to have on the early model unit.

DavidR.

No nerves hit here and I apologize if I came off crossed in my reply. It is just the same questions when the fork valves came out, but since it is a different product, maybe they need to be covered again. So, here is the descriptions I gave regarding the way the valving with the IAT circuit works; RPM suspension valving explained If the shock needed the reservoir, It would be standard issue on all models of the shock, not a accessory to add on.

Ride height would be nice to have on the early model unit.
DavidR.

Since the 84 to 87 years don't have dog bones, the shock length is used to raise and lower the rear wheel. Will the RPM shock have the function to raise and or lower the rear wheel?

Okay, here is what we came up with the design of this shock as compared to the O.E. design compared to the other shocks on the market. I was able to send the manufacture an O.E. shock as well as a Penske so they could make the best product possible.

One thing the Penske does have that seems to be useful for the FJ owner is a longer shaft length. The reason it is long is because it is a universal shock that has adapted to fit to the FJ. The benefit of the longer shock has been the raising of the rear suspension. One thing that we found on the early version was the significant change of the swing arm cantilever the shock uses to control the ride height. This change in arm angle repositions the shock location to the point where the spring was interfering with the swing arm.

This problem was really amplified as the replacement aftermarket springs are a larger diameter wire resulting in a coil spring that is about 1/4" larger in outside diameter.

The other issue of the longer shaft of the Penske results is the shock body is smaller resulting in less compression travel. The smaller shock body of the Penske requires the remote reservoir to function at its maximum efficiency. Sure uit works better than the O.E. shock without one, but for the optimum performance you have to have a reservoir.

Now since the shaft is longer on the Penske, and it changes the cantilever geometry, it requires a much heavier spring to keep the ride height up at the raised position. So, now you have to have a compression adjustment to reduce the harshness of the stiffer spring required to keep the ride height.

So, as you can see when one aspect changes at least one other thing is affected by the change and that must be addressed exposing other issues.

The RPM shock is designed pretty close to the O.E. stroke length which does not have any interference issues on the early models. I have had a couple different versions of the RPM shock body in my hands to check for clearance issues regarding the overall stroke of the shock travel. This also allowed us to have a large enough body to contain all of the valving as well as enough oil to operate for many, many years of service.

Now, the dog bones are easily modified on the late model bikes, but the early models are going to require a specific manufactured piece. I have one sitting here, and if there seems to be a large enough request for raising the rear of the 84-88 models I will start looking into the options for that request.

The rider sag is going to be very crucial on the RPM shock and the coil over adjustment is going to be means of getting it correct. The shock, just like the fork valves use lighter springs that the old school shocks use to allow the IAT (inertia) valve to work over the high speed shock travel and absorb all of the sharp bumps, offering a much more comfortable ride than the Penske could ever offer.

Randy that shock looks to fit, the years of the best looking FJs. Your not bias are you, just funny how it happens to fit BOTH your bikes.
If you need NE roads tested let me know, I have one it will fit too.

Bob W

I have to start the testing somewhere...

Since I don't have a late model sitting in my shop, I figured it was better to start putting miles on it. I am ready to get these this bolted on a enjoy the ride. The valving is going to be real close based on the dyno numbers as compared to the Penske, but the spring rate is going to be the biggest thing we have to get figured out.

If anyone has any further questions let me know, I am glad to answer them. I understand we have progressed into new technology and the old way of thinking is hard to get past. Heck, there has been more than one guy that bought the RPM fork valves and installed heavier than recommended springs or way to much preload and they have not been happy with the fork valve performance. But after they get things set up the proper way as I have recommended they cannot believe the performance improvement.

I will end this with the question I ask myself when I start a project like this, "Does the value of the item equal the performance?"

I don't sell too many "shiny" items that do not offer any benefit other that just looks. Heck, David know this as he was the one who started the
Carb S/S screw & o-ring kit. I added a few more items to be a full kit including the intake o-rings, but the majority of the kit is the same kit he sold. That kit not only replaces the crappy screws and old o-rings, it uses bitchen S/S for improved performance & looks.

Randy - RPM

[RichBaker]

There is a coil over adjuster on it

Ride height is adjusted separately from sag. The preload ("coil over adjuster") adj. is for sag.  Ride height on the Penske is adjusted using a threaded shaft between the mount (top or bottom) and the frame (or linkage).....
A ride height adjustable shock is better than using different length dogbones, because it won't affect linkage "rates". Most shock linkages incorporate a "rising rate" geometry that mimics progressive springs, but better.

[racerrad8]

A ride height adjustable shock is better than using different length dogbones, because it won't affect linkage "rates". Most shock linkages incorporate a "rising rate" geometry that mimics progressive springs, but better.

If the shock length is changed over the O.E. setting then the linkage rate will change due to the angle changing. Anytime the linkage angles are changed, the linkage rate will change and the spring rate must be change to compensate.

If the ride height adjustment is made after the shock linkage via dog bones, the linkage rates operate in their designed perimeters.

I can tell you the Penske I borrowed to design from did not have any adjustment for length. The top shock mount is one piece aluminum and the lower mount was removable but not adjustable due to the adjustment knob for valving adjustment.

I even borrowed Ed's complete shock book at the WCR so we could get Baldy's shock set up for him and do not recall a height adjustment, only the coil over for sag.

Maybe I had the basic Penske and the adjustable length is on the high dollar ones...

Randy

[racerman_27410]

Maybe I had the basic Penske and the adjustable length is on the high dollar ones...

Randy

this..... i dont believe the Penske sport shock has ride height or compression damping adjustment.

i am curious how resistant to fade the new RPM shock is... looks good keep us up to date on how the testing goes.

KOokaloo!

Frank

[SlowOldGuy]

I have Penske Sport Shocks for my '85 and '93.  The both have shock length (ride height) adjustment.  The lower mount threads into the shock piston shaft.  There is a maximum length for the adjustment (12mm if I recall).  The Sport Shock does not have compression damping adjustment, only length, rebound damping, and preload.

Randy, sorry to ask the same old questions.  I'll trust the technology until I get my fork valves installed.

What I do have questions with is the testing process.  Will the testers have experience with more advanced suspension than the FJ.  It's not too hard to improve on the stock FJ components (that's not meant as a knock on your stuff).  For instance, with RT fork valves and a Penske both my FJs are INCREDIBLY FAR BETTER than stock.  However, they still SUCK compared to the STOCK suspension on my FZ1.

As the Race Tech guy likes to say: "The best you've ridden is the best you know."

There's a lot of "what feels right" involved in suspension setup (after getting the basics down).  I'm sure not everyone on the MotoGP grid has the exact same setup.  What concerns me is there appears to be no fine tuning.  What the "testers" felt was right might not be what I like.  It's a trade off of comfort versus performance.  I might prefer more on the sport side.  It would be nice to be able to "fine tune" the final product for personal preference.  However, I can underrtand that the valve might not be "adjustable."

I'm just not sure I trust someone elses opinion on what I want my suspension to feel like.  Again, I'm not trying to be confrontational, just truthful.  Suspension "comfort" and "control" are two vastly different beings.  My brother's BWM is nice and comfy when the electronically adjustable suspension is on Comfort mode.  But it's a PIG in the twisties with this setting.  It does much better on the Sport mode, but even that mode can stand a little tweaking for my tastes.  But that's not possible, "someone" at BMW decided what the "best" settings for the different modes are.

This brings up a question about the fork valves.  When I finally get around to installing my fork valves, the rebound circuit is still active, true?  If not, how do the RPM fork valves bypass the stock rebound circuit?

DavidR.

[yamaha fj rider]

Randy looking at your new shock makes me feel like a little kid on xmass morning. I cant wait. Thank you and keep up the good work. 

Kurt

[Mark Olson]

Hey randy , great job , I would be willing to be a test mule for the 86 shock and compare it to my penske ride height adjustable ,rebound adjustable , compression adjustable ,remote reservoir old technology shock.
it was such a pain in the ass to set it up I think a good to go replacement would be welcome by all.

Craig and I were talking about a trip to your shop anyway,
so if you dare , I promise a fair trial.
you have seen me ride.

Craig would like one for his 90 as well.

[Alf]

I´m not a particular fast rider but I´m a "sensitive" one: i.e., if a tyre have lost 0,2 bar I´m able to feel it. And usually my friends ask me about to tune their suspensions

Getting a "do all everything" for a suspension is a very difficult task. In my own bikes I only get an optimum setting after 3 or 4 ownership months, riding in a lot of roads and a lot of kms. My friends feel surprised when ride my bike and have the best of 2 worlds: comfortable to ride all day long and control for a sport ride

People usually dial too hard the suspension leaving the bikes difficult and harsh to ride except on the most perfect pavement roads, something very unusual in the real world. When the suspension is too hard you have the feeling of going fast... then a softly and properly suspended bike pass you and go away

So the Randy approach to tune the shock I think is the correct way... and the most difficult. The shock could be excellent.

[nurse]

Now, the dog bones are easily modified on the late model bikes, but the early models are going to require a specific manufactured piece. I have one sitting here, and if there seems to be a large enough request for raising the rear of the 84-88 models I will start looking into the options for that request.

Two quick questions:

1) will the shock come with a recomended dog bone length for the late models?, or is it a case of do for yourself, what you are happiest with (given we all have different rear end set ups)?

2)What rider weights will the set up be based on?  Anecdotaly having read different threads on here, most of us (optimistically!?! - me included) put ourselves around the 100kg mark - give or take a kilo or 2 or 3 or 4 .....

[yamaha fj rider]

Awesome Randy, thanks for the update. Wish I lived close enough to be one of your test subjects. You could then state that your shock was monkey tested and Power Ranger approved.

That is quite an endorsement! 

Kurt