RPM shock installed

[aviationfred]

Mark,

Here is a photo that Randy sent me of the 89'/90' upper shock mount when I did my install.




Fred

[FJmonkey]

Thanks Fred, that confirms it, the 89+ upper shock mount is higher in the frame than the 84/87 location. And looks to be about the same amount of lift as the 89+ shock link lower mounting point. My current frame is bent/tweaked so I can look at modifying my spare frame to raise the upper shock mount. Time to figure out how I am going to strip and repaint the spare frame in the mean time.

Is it beer o' clock yet?

[Capn Ron]

Time to figure out how I am going to strip and repaint the spare frame in the mean time.

I've got a reasonably priced powder-coater in Sun Valley.  I seem to recall, I paid $180 to have them do the frame and swing arm.  That included all the media blasting and masking.  Came out great and it was no more effort than driving over there and writing a check!   

Is it beer o' clock yet?

No, but it's always wine-thirty at my place!  Swing on over if you need a break!   

[FJmonkey]

I got some time on the bike today and took some tape measure (close) dimensions so I can model the FJ suspension. I am surprised that I got really close after I mated up the model bits and got really similar geometry results between my FJ and the model. In this first image it looks like my set up with the RPM shock, '89 shock link and 5.5 inch long dog bones (DB).



I have the lower frame rail the same height off the ground while on the center stand. Then I modeled the individual bits and simulated the frame mounting locations. I have the diameter of my rear wheel calculated from www.Gearingcommander.com. The Cent to Cent (C to C) distance of the shock mounts are very close the actual length of the '91/92 RPM shock.

Not the best image but you can see my current shock link is decidedly angled down and the DB will not allow the CS to fully stow. Making any cornering a recipe for scraping hard parts and lifting the rear wheel off the ground way too soon.



Then I took the '89 lower shock link and saw that it mounts the lower part of the shock 1.25 inches higher than the '84/87 link. So I made an upper location that much higher in the model and just guessed at using 3.5 in long DB and my C to C shock is about 1/2 short. Then I measured my 'OEM shock and the RPM shock and found the RPM shock and got about 0.43 inches longer on the '91+ shock. This next image is with the upper mount 1.25 higher and 3.5 DB.



The lower shock mount is now more horizontal and better tucked in where it will not foul the center stand when stowed. I would like to see a stock '89 image showing the linkage geometry. I want to mimic it as close as possible so the shock performs with the bike properly.

Now to make this project a reality I need to make a new upper shock mount. Here is the mount on an '86/87 frame.



And here is a first pass at the raised shock mount I will get made in the near future and welded on my spare '86/87 frame.



When I get the details sorted out I will publish the fabrication drawing in the files section. Just in case there are any other nut cases that want to go this much trouble for dog bones.

That is all for now.

[Cash Dereszynski]

I'm reading this with great inerest as I think I need to raise my rear suspension too. Maybe a longer shock with some length adjustably .

Cash

[andyoutandabout]

Captain ron's powder job is giving me a boner.

[fj johnnie]

 Good work Mark. I am anxiously awaiting your results.

[FJmonkey]

I won't be spending any more money till I find a job and get an income again. The good news is I am getting calls so the jobs are out there. I still want to complete this project and get my '86 back on the road and properly representing the FJ in Red and White. And I will post a proper wright up so others can follow if they chose.

[Canadianlocost]

Today I have some time to look at the shock install and compare the OEM set up and the 89" conversion parts I installed. First I put them side by side with a common bolt through the top shock mount.



I noticed that the RPM shock was slightly longer the OEM shock that was in my 86' FJ. The difference only adds to the next detail of why I needed dog bones that were 2 inches longer.



The 84/87 lower shock mounts to a common pivot point, the 89+ to a dedicated pivot point higher than the 84/87 point.



That higher pivot point effectively pushes the shock link further down and the dog bone pivots farther away from the swing arm pivot points.

I suspect that the 89+ frames have a higher upper shock mount location than what I have on my 86' as shown below.



Anyone with a spare frame or access to take a picture of an 89+ upper shock mount, similar to the one above? I need to confirm or deny my suspicions regarding the upper shock mount. 

I will be working with Randy as well on this, as he already mentioned, this is uncharted territory.

Important note:
Randy recommended that I simply use the 84/87 RPM shock. I decided I wanted to have the ability to adjust the rear height with 89+ dog bones. Sometimes Moditus means we create more work to keep us happy/busy with our FJs.

I have a fully stripped 1990 frame I can take a picture of if that is still desirable. It has a clean Washington State title with it if anyone wants it. Seems mike the main frame was not altered.

[FJmonkey]

I have a fully stripped 1990 frame I can take a picture of if that is still desirable. It has a clean Washington State title with it if anyone wants it. Seems mike the main frame was not altered.

Thanks for the offer, I have parked my '86 till I can fix the frame and the cracked case that leaks oil on to the rear tire. I have since purchased an '89 to prevent withdrawal and the nasty symptoms associated with nothing to ride. So I have a good example of the '89/'90 frame.