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Old December 16th, 2008   #1
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Default Penske Rear Shock review (from the Old MSN Forum)

From: sport_tourer (Original Message)Sent: 5/16/2005 6:35 PMPenske Racing Shock Review.

Well, on the main board I posted in mid April or so that I had ordered a Penske Racing Shock for my ST1300. I looked long and far on shocks for the ST1300 before deciding on a Penske. This post will detail my saga and experience with the shock.

The shock was ordered from Jim Lindemann at Lindemann Engineering. The shock took 10 business days to build (as Penske originally stated) and was dropped shipped (per my request since I live on 20 miles from Penske's Main office) at my home. The shock arrived nicely packaged, complete with dyno curve for my shock, a technical manual and overall a pretty nice looking item. I ordered the two way adjustable model 8981 (6 click slow speed compression, 25 click rebound, manual preload, and ride height adjustable shock. Shock comes with a remote reservoir and utilizes a single rate spring.

Removal of stock Honda old shock.........well, all I can say is ma Honda decided to install the lower shock mounting bolt from the wrong side of the mount. This necessitated removal of the aluminum "frame" which supports the footpegs. Stupid assemblers. Otherwise pretty straight forward and essentially simple, but in all honesty, more of the motorcycle had to be disassembled than I thought would be required. As a note, if you remove the old shock, make sure you install the lower shock mounting bolt from the left side of the bike.

Installation of new shock.....crap it didnt fit! Yup, you heard right, the new Penske shock did not fit. Specifically, the upper mount on the bike's frame had to be radiused (read ground down) about 2-3 mm so the new shock body would clear the frame. The problem is that the Penske shock body has square shoulders, not round like the stock shock, and this created the problem. Turns out Penske makes another shock body which would fit without grinding/frame modification, however, they would not be able to install a remote reservoir on such a shock body because they could not install the necessary fitting. So, after a little grinding on ye old frame, the Penske shock fits fine. If you do not consider it acceptable to take 2-3 mm off your frame to mount the shock, the Penske shock will not work for you. WIthout pictures its hard to explain what had to be ground off....basically the grinding process takes a right angle edge of the frame and rounds its off a bit. Not an excessive process, but grinding was indeed required.

After the shock was installed, bike was dropped off the center stand. Whoa, holy chopper-like ride batman! The bike practically collapsed on itself. The 1000 lb spring which was installed on the Penske shock was woefully too soft...not even close for the bike alone, yet the addition of my 220 lbs fully dressed in gear. So I dialed in some preload to the spring. BTW, the Penske preload collar is basically a collar with numerous "holes" in it..... a special tool is inserted into the collar and then one can easily turn the preload adjuster with the shock installed in the bike. No need for a remote preload adjuster on this shock as preload adjustment is quite simple and no fuss. This was one of the advantages I saw with the Penske shock. I wound up having to dial in 2.0 inches of preload on the 1000 lb. spring to get the proper race sag for my weight. 2.0 inches or preload confirmed that the spring was way too soft.

Calls were then made to Penske and Lindemann Engineering to complain of the soft spring problem Turns out that Penske has only sold 2 of these shocks for ST1300s. The other shock was ordered by GP Suspension and they specified a 1000 lbs spring and since Penske never heard back from them, they assumed that the 1000 lbs spring was correct (more on the spring thing later). Well, after explaining the shock was woefully undersprung, the guys at Penske asked me to pick a date, which turned out to be today May 16, 2005, to visit their shop 20 miles from my home and they would do whatever was necessary to get the shock setup correct. So off to Penske I went this AM.

I met with Tim and Bruce at Penske. I showed them the bike with their shock and the required 2.0 inches of preload for my weight. They were kinda amazed at that amount of preload. So into their garage I pulled the bike, and I removed the rear shock. I also brought along the stock Honda shock so that they could run some tests and obtain some data. The stock shock was disasembled and the spring tested. The stock Honda spring is essentially a single rate spring rated at 900 lbs (for those requiring details, at 1/2 inch compression 450 lbs, at 1.0 inch compression 922 lbs on one try and 931 lbs on another, at 1.5 inches compression 1427 lbs, and 2.0 inches compression 1964 lbs. compression). However, what was quite interesting on the stock shock was the fact that the shock is only allowed maybe 1/2 to 3/4 inch stroke before encountering a bottoming bumper. NOW THIS IS IMPORTANT.......This explains why the back of the ST also felt like they was never any movement in the rear suspension....the god damn bike was essentially riding on the bottoming bumper and that WAS THE SUSPENSION! Given the fact that the Penske shock was built with a 1000 lb spring while the stock shock was a 900 lb spring, yet the 1000 lb spring required 2.0 inches of preload, tells u that the stock shock is woefully far undersprung that it really isnt even adequate for a passenger of zero pounds weight! If you could see the bumper in action, you would find that the stock shock is essentially sitting on the bumper or is damn close just from the weight of the bike. After a bit of required suspension travel, you are no doubt into the bumper and thus the bumper becomes your suspension. Nice job Honda!

The final Penske setup......we decided on essentially what is a 1400 lb spring (for those wanting details, 1/2 compression required 632 lbs, 1.0 inch required 1400 lbs.) A shim stack of the following shims.... 1.350 x .010 and 1.20 x .010 (these two make up the low speed compression) and 1.050 x .010 and 0.900 x 0.008 (these two make up the high speed compression). The shock was completed with 150 psi nitrogen. 5 wt Silkolene oil was used. The rest is their basic 2 way adjustable model 8981 shock. Remember, this is for a geared up 220 lb rider. WIth the new setup, I am running about 8 mm preload on the spring to obtain 17 mm race sag and have about 3mm free sag (no rider on board). This is suggesting the spring may be a touch too stiff as the amount of preload currently required (8 mm) is a bit less than what Penske and most shock manufacturers like to see (12 mm to 25mm). A 1300 lbs spring would obviously require a bit more preload than the current 1400 lb spring, but since I like to run race sag on the "less" more than the "more" side and the stiffer spring will help in those rare occasions I have a passenger, I think I will keep the 1400 lb spring. After a bit more seat time, I may change my mind and request a 1300 lb spring. We also added about 1/8 inch of ride height to the stock length, which in turn resulted in about a 1 inch increase in ride height of the rear of the bike (due to the layed down nature of the shock which leverages the actual ride height of the bike). Just a note, 1/8 inch of ride height increase on the shock is about the maximum you can run on this bike....any more and the bottom of the swing arm contacts the top of the exhaust pipe just in front of where the mufflers attach to the pipes. With the increased ride height, when the bike is on the center stand, the rear tire is no longer off the ground!

The final ride result....I only have about 60 miles on the bike since the new shock setup was completed. However, I am very much liking it. My compression adjuster is set at "4" and the rebound is set at approximately half way plus 2 clicks (I didnt actually count the number of clicks from full in or out and just took my reading from the stock Penske setup, but given the 25 click adjustment for rebound, I have plenty of room to go). The increased ride height noticeably quickened the turn in of the bike, and the damping of the Penske shock makes high speed compression obstacles disappear. The bike actually has a suspension which one can feel working. This is sweet. The addition of the Penske shock to the Race Tech front end (including fork brace) on this bike has transformed this bike into what it should be. In my opinion, the Penske shock was worth the price and would be a far better "investment" than pipes for the ST1300.

So, if you are in the Southeast Pennsylvania area, weigh 200 to 240 lbs, and need a test ride on a properly suspended ST1300, the cost is only $50 per ride (hey, I gotta get my money back some way for the two days off from work I had to take to get things sorted out between Race Tech and Penske) plus some release papers, etc.. I will say, if you weigh anything less than 210 lbs naked and ride primarily solo, you probably should be looking at a 1300 lb spring, not 1400 lb.

And remember, when you order your Penske shock, you have me to thank for Penske's development of their two way shock for the ST1300.


Message 2 of 6 in Discussion From: steveonahondaSent: 5/16/2005 8:16 PMChris,
Great write up with just the right amount of ego to back it up. Just one thing though. What was the cost of this setup? Or do I just need to multiply $50/ride x the number of rides to recoup the costs....

High Point, NC

Message 3 of 6 in Discussion From: SteveJonesMOSent: 5/16/2005 10:25 PMChris:

Did you (or they) talk or think about the spring needed for somebody who wanted the suspension properly set up for riding 2-up at full GWVR?

Also, what tool did you use to grind the frame to accomodate the shock?


Steve Jones, St. Louis, MO
STOC 3920, '03 ST1300 ABS, '83 VF750F Interceptor

Message 4 of 6 in Discussion From: sport_tourerSent: 5/17/2005 2:18 PMSteve............shock cost was $679 through Lindemann Engineering.

Steve that Penske has a baseline spring from my experience which works with my weight, you just need to give them your 2 up weight and they will accomodate you with the correct spring. Just remember, if u ride 2 up only 50% of the time, and you get the spring for 2 up riding, the other 50% of the time the spring will be too stiff for you. You have to make some concessions here if you want a single rate spring but use the bike in two different modes (solo and two up). I do not like progressive rate springs, but sometimes they are the wiser choice if you loads on the bike vary greatly. Call Penske and talk with Tim or Bruce.... should work but if it doesnt just do a quick search.

As far as grinding the frame down, simply took an air grinder with a diamond tipped bit and had at it...took about 15 minutes, and I also used a very thin bayonet belt sander (think a long thin belt sander). A dremel with appropriate cutting tools will work just fine. The grinding is not hard and I am certain is will not effect the frame strength in the area which has to be ground. Just the fact that u grind a frame ma Honda wont like!

One last note, if you are doing the Penske shock, make sure the front end is up to snuff first. I will be sending the stock front spring to Jim Lindemann at Lindemann Engineering when I get the chance so he can make up some single rate front springs for the bike in the 1.10 to 1.30 kg/mm range. Race Tech apparently hasnt taken the task to heart and hasnt done such as of yet. 1.0 kg/mm springs, which I have in mine, are barely adequate for my 210 lbs naked weight.


Message 5 of 6 in Discussion From: JoeZulaskiSent: 8/12/2005 6:15 AMGreat report and nice follow-up work, Chris.

I had a Penske shock on my old ST1100 and RaceTech on the front. Great combination. It really transformed the bike and I can only imagine the difference on the ST1300.

Penske was always a great company to deal with when I needed something done to the shock (I had it rebuilt just before the 2001 Iron Butt Rally and had a tight deadline which they met with no problems).


Joe Zulaski

Message 6 of 6 in Discussion From: Wal_N2BRKSent: 11/13/2007 4:10 PMI know that this is digging up an old post, but if y'all can humor me :-)

I was reading about all of the instability comments by Mag testers on the ST13 and the latest one in MCNews mentioned how it has less trail then the FJR and the C14. I know the FJR needs some really heavy inputs, so since the ST and the FJR have the same 26* rake, maybe the magic number for trail is somewhere between the 3.9" for the St and the 4.3" for the FJR?

At least I thought so until I read this post. Your bike didn't become more unstable at speed with the rear end raised? By doing so of course, you actually reduced your amount of front end trail. I would have thought that it would have made it worse. I was thinking about running a shorter shock to increase trail slightly, but a stiffer spring and less sag.

What is your longer term report on this now?

Thanks :-)
Joe Zulaski
Redmond, WA
MSF RiderCoach
STOC# 929, IBA# 218

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