Fine tuning the Penske 8983

[kamal]

Nice day today so I decided to give my 'new to me' Corbin saddle some 'ass time' and check the performance of my new suspension setup.

A friend came over yesterday and helped me setup the 'sag' (something I had never done before in fifty years of riding

)

I studied the manual that came with the shock, and managed to completely baffle myself. So I studied a post from last year:

https://www.fjrforum.com/forum//index.php/topic/149012-adjusting-the-fjrs-suspension/page-2?hl=%20penske%20%20setup

- which made way more sense to me, and set off. Traxxion had done a great job of setting everything up for my weight, riding style etc. What I wanted to try was a road with broken pavement and tight corners, didn't have to go far at this time of the year. The bike handled this stuff way better than before, though the rear felt a little harsh, so I just backed off the rebound four clicks and called it 'job done'.

Anyway, the point of this post is to ask if I've got compression and rebound figured out. If I understand correctly, adjusting rebound alters compression and rebound somewhat, I only alter the compression setting on the remote reservoir to fine tune things?

Does that make sense? Remember, I'm a little out of my depth here, but I'm learning.

Thank you.

Al.

 

[MCRIDER007]

I think the rebound and compression adjustments are totally independent on the 8983. If your ride is harsh you probably should be adjusting the compression damping on the reservoir.

 

[kamal]

I think the rebound and compression adjustments are totally independent on the 8983. If your ride is harsh you probably should be adjusting the compression damping on the reservoir.

Thanks MC.

That's the kind of feedback I need. Right now the compression is set at halfway between + and - with 150psi of gas. I'll try adjusting it tomorrow.

 

[TomInPA]

I installed the 8983 the day before I had knee surgery in November and then left CA for PA and haven't seen the bike since. Plans are to get back to CA April 19 and leave on April 21 for a cross-country trip. I need to read up on tuning that shock.

 

[kamal]

I installed the 8983 the day before I had knee surgery in November and then left CA for PA and haven't seen the bike since. Plans are to get back to CA April 19 and leave on April 21 for a cross-country trip. I need to read up on tuning that shock.

Happy to be doing your homework Tom.

Al.

 

[MCRIDER007]

Be aware that if you got the same Penske Technical Manual that I did, the description of the 8983 Compression Adjuster in the back of the manual is wrong, it is actually a copy of page 11 which is the description of the 8986. There is a big difference between the 8983 and the 8986, the 8983 adjustment changes the low speed compression damping, the 8986 adjustment changes the high speed compression damping.

On the 8983 you turn the adjustment knob clockwise to increase the damping....if the ride is harsh you want less damping so turn the knob counter-clockwise.

 

[kamal]

Be aware that if you got the same Penske Technical Manual that I did, the description of the 8983 Compression Adjuster in the back of the manual is wrong, it is actually a copy of page 11 which is the description of the 8986. There is a big difference between the 8983 and the 8986, the 8983 adjustment changes the low speed compression damping, the 8986 adjustment changes the high speed compression damping.
On the 8983 you turn the adjustment knob clockwise to increase the damping....if the ride is harsh you want less damping so turn the knob counter-clockwise.

Yes, that's the manual I have. Luckily it gave me a headache, so I gave up on it. I think I'm starting to get this.

Thanks again.

 

[TomInPA]

I know I have the 8983...here is the sale thread. Sure wish I would have had the chance to try this thing out before dropping a 4000 mile road trip on it.

 

[MCRIDER007]

I know I have the 8983...here is the sale thread. Sure wish I would have had the chance to try this thing out before dropping a 4000 mile road trip on it.

I don't know your weight or much total weight you will be carrying but a 850 lb spring is a pretty hefty spring for a GEN1, if it feels too firm you may need to put the compression damping on or close to full soft. Either way it should be a huge improvement over a high mileage OEM shock.

 

[Nikk]

kamal, I'm 210 pounds and run a Penske 8983 shock and GP Suspension rebuilt forks.

I setup my FJR to 30% sag numbers which is about 37mm.

[SIZE=11.818201065063477px]My suspension settings: [/SIZE]

[SIZE=11.818201065063477px]1wb - rider with empty bags, 2ld - rider loaded for touring, 2ld - rider and passendger loaded for touring this addess a lightly loaded top case.[/SIZE]

Values are turns out from the full + direction.

1wb 1ld 2ld

Front preload 8(lines showing) 2 2 2

Front rebound damp (out) 9 7 7

Front comp. damp (out) 14 14 13

Penske Rear pre-load: 37mm +1.5turn +2turn

Penske Rear rebound (out) 13 10 8

Penske Rear comp. (out) 16 17 17

Right or wrong, I tend to back off the rebound and add some compression damping as I load the bike. Plus some preload for sure.

I had a great deal of trouble dialing in the Penske with the stock forks, once I had GP fork upgrade the shock was much better behaved.

You should be able to get the rebound close while parked. Just weight the rear and watch how fast the bike recovers. You don't want the bike to pogo but you don't want it to recover too slow. There is some magic here that you just need to learn by experience.

Than I would set the compression damping on the low end and gradually increase it over time until you settle on something you like.

I spent about 2 years of riding to get my gear dialed.

 

[kamal]

Thanks Nikk.

I'm also a svelte 210 geared up.

Those settings are more or less where I'm going to end up at.

Al.

 

[kamal]

I know I have the 8983...here is the sale thread. Sure wish I would have had the chance to try this thing out before dropping a 4000 mile road trip on it.

I don't know your weight or much total weight you will be carrying but a 850 lb spring is a pretty hefty spring for a GEN1, if it feels too firm you may need to put the compression damping on or close to full soft. Either way it should be a huge improvement over a high mileage OEM shock.

I also have the Hyperco 850lb spring, shortened .25" so I can sit flat footed. Seems to work great.

 

[MCRIDER007]

Right or wrong, I tend to back off the rebound and add some compression damping as I load the bike. Plus some preload for sure.

When you add a significant amount of weight you also need to use preload or the ride height adjustment (which is very easy to use on the Penske) to maintain your steering geometry. The required rebound damping is closely tied to the spring's rating but adding weight to the bike will make the spring go deeper into its compression stroke and rebound harder....therefore any adjustment to rebound should be to increase damping. Likewise for compression damping, a rider and passenger would do better with a heavier spring but increasing compression damping will help to slow the spring's action on the compression stroke.

 

[MCRIDER007]

I know I have the 8983...here is the sale thread. Sure wish I would have had the chance to try this thing out before dropping a 4000 mile road trip on it.

I don't know your weight or much total weight you will be carrying but a 850 lb spring is a pretty hefty spring for a GEN1, if it feels too firm you may need to put the compression damping on or close to full soft. Either way it should be a huge improvement over a high mileage OEM shock.

I also have the Hyperco 850lb spring, shortened .25" so I can sit flat footed. Seems to work great.

I thought you said it worked great except for the harsh ride.....which is understandable for a 210 lb rider with a 850 lb spring on a GEN1 (GEN2s have a longer wheelbase and need about an extra 50lb in the spring rate). I'm surprised they gave you a 850 unless you indicated that you often have a passenger or a large trunk but you may still get a plush ride by backing off the compression damping.

 

[900gc]

Don't be afraid to try the compression and rebound damping over the full range of adjustments and even a few turns of spring preload. Its a learning process which you can have some fun with: set it up full soft and ride for a while, stop, set everything to full firm and ride for a while. You will notice quite a difference at the extremes. Then start to dial it in to where you like it. Hopefully if the spring rate and valving are right, you'll end up somewhere near the middle. Its a little trick I learned from veteran racers years ago to set up my race bike. You can learn to become sensitive to small changes eventually.

Compression and rebound damping are separate but you can make the shock seem "harder" when hitting bumps by using too much rebound. It can cause the shock to "pack down" by not allowing it to recover it's stroke before the next bump.

A nice thing about adjustable suspension is the different settings you can use to make your ride more enjoyable depending on circumstances. So have fun and experiment.

 

[Fred W]

I know I have the 8983...here is the sale thread. Sure wish I would have had the chance to try this thing out before dropping a 4000 mile road trip on it.

I don't know your weight or much total weight you will be carrying but a 850 lb spring is a pretty hefty spring for a GEN1, if it feels too firm you may need to put the compression damping on or close to full soft. Either way it should be a huge improvement over a high mileage OEM shock.

I also have the Hyperco 850lb spring, shortened .25" so I can sit flat footed. Seems to work great.

I thought you said it worked great except for the harsh ride.....which is understandable for a 210 lb rider with a 850 lb spring on a GEN1 (GEN2s have a longer wheelbase and need about an extra 50lb in the spring rate). I'm surprised they gave you a 850 unless you indicated that you often have a passenger or a large trunk but you may still get a plush ride by backing off the compression damping.

I run 220 lbs, ride 25% of the time with a 100 lb passenger, and I told GP that I am not an extremely aggressive rider that rides on some crappy/bumpy New England roadways. They recommended that I up my spring rate from the 800 that was on there to a 900. They said that will allow me to back off on the spring pre-load and the compression damping and give me a more compliant ride.

I haven't got the shock back from them yet with the new spring, but will report my impressions when I do.

 

[MCRIDER007]

I run 220 lbs, ride 25% of the time with a 100 lb passenger, and I told GP that I am not an extremely aggressive rider that rides on some crappy/bumpy New England roadways. They recommended that I up my spring rate from the 800 that was on there to a 900. They said that will allow me to back off on the spring pre-load and the compression damping and give me a more compliant ride.
I haven't got the shock back from them yet with the new spring, but will report my impressions when I do.

We have a new Sheriff at GP Suspension and it sounds like he is recommending bigger springs than the old one.

My experience...........I'm in the same weight range and have a 15lb trunk that I transfer from bike to bike. My 800 spring (with 10mm of installed preload) is a tad firm with the saddelbags off but feels very good with the bags on and loaded. The spring felt a bit undersprung last summer when I had a 105 pound passenger and I had to add about 10mm of preload to maintain steering geometry.,,...but this is with a GEN2.

I think your 900lb spring on your 05 is going to feel pretty good loaded with your passenger but very stiff riding solo unless you are carrying a lot of weight in the trunk and bags (just like the LD riders who were using 900 lb springs in rally mode).

 

[kamal]

I know I have the 8983...here is the sale thread. Sure wish I would have had the chance to try this thing out before dropping a 4000 mile road trip on it.

I don't know your weight or much total weight you will be carrying but a 850 lb spring is a pretty hefty spring for a GEN1, if it feels too firm you may need to put the compression damping on or close to full soft. Either way it should be a huge improvement over a high mileage OEM shock.

I also have the Hyperco 850lb spring, shortened .25" so I can sit flat footed. Seems to work great.

I thought you said it worked great except for the harsh ride.....which is understandable for a 210 lb rider with a 850 lb spring on a GEN1 (GEN2s have a longer wheelbase and need about an extra 50lb in the spring rate). I'm surprised they gave you a 850 unless you indicated that you often have a passenger or a large trunk but you may still get a plush ride by backing off the compression damping.

To clarify. The setup does work great on most road surfaces. I was having problems, pre-upgrade, on roads with winter damage, in tight turns, the front end would start 'chattering' (for want of a better word). That problem has been completely cured but I noticed some 'harshness' at the rear, which prompted me to try to fine-tune it out. I think from what I've learned here, I now know how to do that properly. If not, it's a minor thing and something I can easily live with.

I appreciate your input and help.

Al.

 

[MCRIDER007]

To clarify. The setup does work great on most road surfaces. I was having problems, pre-upgrade, on roads with winter damage, in tight turns, the front end would start 'chattering' (for want of a better word). That problem has been completely cured but I noticed some 'harshness' at the rear, which prompted me to try to fine-tune it out. I think from what I've learned here, I now know how to do that properly. If not, it's a minor thing and something I can easily live with.I appreciate your input and help.

Al.

You're welcome.....but after thinking about the spring rate issue in more depth, my FJR experience is with a 800lb spring on a Wilbers 840 model shock that does not have independent compression damping and was originally valved for a 646lb spring. It probably should have been revalved for the larger spring and when I increased the rebound damping to compensate for the stiffer spring, I also increased the compression damping.......the end result is a shock that probably has a lot more compression damping than your Penske. Maybe I should stop commenting on spring rates until I hear some more feedback from FJR Penske owners (I have a Penske but its on my C14) but this discussion certainly demonstrates how woefully undersprung the OEM shocks are.