Stock shock

[LA Mike]

I am trying to get the spring rate of the stock shock for our bikes(87-91). I think I remember reading it was 800lbs long time ago over at the Yahoo forum, is this correct if not what is the correct rate?

Thanks,
Mike

[Arnie]

I am trying to get the spring rate of the stock shock for our bikes(87-91). I think I remember reading it was 800lbs long time ago over at the Yahoo forum, is this correct if not what is the correct rate?

I measured the '91 rear shock spring @ 700lbs/in.  There was a change of shock style btwn the 87-90 and the 91-93 models.  The front spring rate went down considerably in '91 and it is likely that the rear was also made softer at the same time.  We had some springs made that were spec'ed at 900lbs/in but the first batch delivered were ~1100lbs/in.  You'd have to be a really "fat bastard" to need these.  The 900lb/in springs were right for most.

Sorry to all about to ask for one, they are no longer available.

Thanks,
Mike

[tqmx1]

Mike, I just checked the Penske sight and they call for up to 160# 850/ 160-190 900/ 190-225  950/ 225 up 1000. But what I have found on my FZ1 they run low on there rates for my weight they call for 550 but a 650 is what I ended up with

Good luck on what you chose

Kim

[Arnie]

Oops!  I put my reply along with LAMike's question.  my bad.

The reply (only) should read:

I measured the '91 rear shock spring @ 700lbs/in.  There was a change of shock style btwn the 87-90 and the 91-93 models.  The front spring rate went down considerably in '91 and it is likely that the rear was also made softer at the same time.  We had some springs made that were spec'ed at 900lbs/in but the first batch delivered were ~1100lbs/in.  You'd have to be a really "fat bastard" to need these.  The 900lb/in springs were right for most.

Sorry to all about to ask for one, they are no longer available.

Arnie

[LA Mike]

I saw that they change style on the 91 & up.  So guess what is the spring rate on the stock 1989/90 shock if they made rate changes for different years.


Thanks,
LA Mike

[Arnie]

I saw that they change style on the 91 & up.  So guess what is the spring rate on the stock 1989/90 shock if they made rate changes for different years.

Thanks,
LA Mike

I wouldn't worry too much about what stock was/is, but what YOU think will work best for you.  Does the bike wallow, especially with a pillon or gear loaded?  Does it bottom?  You need a higher spring rate.
Does the bike pogo?  Does the rear bounce up into the air on even small bumps? Then you need a lower spring rate and/or more damping.

My WAG is that you probably need higher spring rate, and higher preload, and more damping.

Cheers,
Arnie

[the fan]

Mike,
I installed a 950lb spring on deans FJ before the fall rally. I was able to get a very good balance with the forks which IIRC are equipped with 1.0kg/mm springs and emulators. Dean also has shortened dogbones out back.

The damping control was OK with the heavier spring. Not spectacular, but not bad either. I did not spend much time on the bike but it seemed to work very well on my short test ride through the local twisties. Dean will have to fill you in on the rest.

This was discussed here: http://www.fjowners.com/index.php?topic=760.0

Lindemann Engineering sells an Eibach spring with the correct ID and fairly close in overall length that should work well. (58mm ID, 7" -178mm free length and 950lb rate)
http://www.le-suspension.com/catalog/product_info.php?cPath=21&products_id=37

[LA Mike]

The reason I am trying to find out the spring rate of the OEM shock spring is that I am trying to mount the OEM spring on a FOX twin clicker shock I picked up on flea bay a while back. The shock was mount on a bike that was much lighter that the FJ, thus the spring that came with it is useless to use on the FJ. The total eye-to-eye length of FOX shock is about 10mm longer than OEM and its also height adjustable.

I was able to take the FJ OEM spring off shock and the FJ spring is the same inner diameter as the fox spring so it mounts on the fox collar perfect. The only difference is the FJ spring is 13mm shorter than the spring that came mounted. When I did my test fit and I still had just shy of 85mm left of preload threads until the end. I think that should be more that enough especially with the heavier FJ spring.

When I took the Fox shock apart to get to the valving the oil was still very clean. I have never rebuilt a shock but the O-rings in the shock and reservoir look like they are in good shape, do you just seals anyway?

I know I will have many more questions to follow as this is a first. Thanks in advance,

LA Mike

[the fan]

Mike,

I replaced the seal and bushing with parts purchased from Lindemann Engineering http://www.le-suspension.com/ .

Jim Lindemann(the owner) was very helpful in setting mine up for my YZF. He also seems to have a better stock of fox parts than Fox itself.

If you were happy with the stock FJ spring before, you should be just as happy now. esp since you have the availability of quite a bit more preload adjustment over the stock shock. Just keep an eye on the free sag which should be somewhere between 15 and 20mm (bike only) after you set the ride sag.

[LA Mike]

If you were happy with the stock FJ spring before, you should be just as happy now. esp since you have the availability of quite a bit more preload adjustment over the stock shock.

I am just trying to save some $$$ by reusing the stock OEM spring on the FOX, a new 900lb+ spring is over $100 dollars. The OEM shock adjuster did work well and the preload was frozen or broke, the only thing on the whole shock worth anything was the spring.

I just need the OEM spring rate so I can get the valving correct. Bill/ anybody what is you take on race tech gold valve kit for shocks, or should I stay with the Fox valve and change the shims on the valving stack(s)

http://new.racetech.com/HTML_FILES/GVCONVERSION.HTML

[the fan]

I have run the Gold Valve kit in a few shocks (including both of my current bikes at one point) and it works well IF you get it right the first time...PITA if you have to go back in to change something. This should not be an issue if the kit is going in a shock designed for the application as RT gets it pretty close in thier charts, but all bets are off when you start modifying linkages and whatnot. Working in the shops I installed dozens of gold valve shock kits in MX bikes and a few Sport bikes, all with good results. It was far more common with the dirty bikes as the cost of parts and labor rebuilding a stock shock (FJ shock is not easily rebuilt as there is no provision for charging nitrogen built in)
get close to the cost of a decent aftermarket piece.

To answer your question on the fox valving all I can say is that the Fox valving works very nicely in the shock I put on my YZF. Due to overly generous genetics i am running a 600lb spring on a shock originally equipped with a 475lb spring and am well within acceptable adjustment range with the stock Fox valving.

I never looked, does Race Tech offer a kit for the fox shock?

[LA Mike]

I went out to Race Tech today to see if they could fit a Gold Valve kit to my FOX shock and they can for $185. I am going to keep looking to see if I can keep the FOX valve and just get the correct shim stack(s) to save $$$, just need to locate info/chart for a starting point for the valving.

Anyway while out there I had them test the OEM spring from my '89 and it is 19.2kg/mm or 1075lbs; so I guessing this will be the same for the  '84 ~'90 models '91 on is a different style. I know most of you guys who run Penske's have 950~1200 springs so this should be OK for my fat $$$.

Mike