Shock spring rate

Hey guys - my first post on VFR World. Looks like a great site.

I need some advice on which shock spring I need for my Penske double adjustable shock. I weigh 245 lbs, ride the north GA mountains/twisties agressively, and consider myself a pretty experienced rider.

The suspension dealer who sold me my Penske set it up with a 1400 # spring. I've had recommendations that range from 950 # from RaceTech to the 1400 # spring that Traxxion installed. The rear end seems a bit harsh for my taste.

Any input would be appreciated.

 

Reg:

Thanks for the welcome.

Keep me posted. The best advice I've recieved so far is from Jim Lindemann at Lindemann Engineering. He said the old 10 mm static sag (no rider) and then another 20 mm dynamic sag (with the rider on the bike) is still a reliable method for checking if the spring rate is correct.

I've been doing some checking around on the net. It is amazing how many springs and spring rates Hyperco has available. Go to a website called "www.performanceshock.com". They have a huge selection of Hyperco springs (in 50#/in increments from 600# to 1600#). A Hyperco spring is a Hyperco spring whether it comes from an automotive oriented website or a motorcycle oriented web site. Performance Shock sells Hyperco springs for $75-85 so they about $25/spring cheaper than Traxxion/Lindemann/Aftershocks for the exact same spring. Penske's seem to use the 2.25" internal diameter springs in either 6" or 7" lengths. Performance Shock has a big inventory of both.

I'm surprised by all of us that as easy as it is to change a spring on an aftermarket shock (especially the Penske) that we don't do more "fine tuning" of the suspension with different spring rates. We seem to get all worked up over one or two clicks on the compression and rebound settings but just slap on whatever springs the "suspension experts" tell us to use or sell us with the shock. Comparing dollars to dollars, you can buy 10 Hyperco springs for the price of one Penske double adjustable shock.

On my KTM Duke II, I can change the shock spring without removing the shock from the bike. I haven't tried it yet on the VFR, but I'm guessing you can do the same.

To change the spring on a Penske shock, you back off all of the preload and get a little slop in the spring preload collar. Take off the bottom clevis of the shock. Move up the bottom spring perch about a quarter of an inch and there is a wire ring that prevents the bottom spring perch from coming off the bottom of the shock. Remove the ring, slide off the bottom spring perch, and the spring slides right off.

I've made quite a few posts on the VFR Discussion Group site and it amazes me in the range of spring rates eveyone is running on their bikes.

I'll keep you posted on what I learn and figure out. Do the same with me.

Thanks again for the welcome.

RDR

 

Lindermann is a smart man, he set up my WP shock, which has it I'm no help at all with a Penske. Thou I'm thinking here as I installed my shock there be no way for me to change out the spring with out taking the shock out of the bike, not a lot of room, thou one might if you where to get all the lower linkage out of the way as well as the exhaust plumping. Now that said, be easier to pop it out then work on it in a vise.

 

No doubt, changing the shock on a VFR is not the easiest task in the world.

 

As you guys get to know me through my posts, you will learn that I have a propensity for thinking some things to death. I do enjoy the tinkering and modifiying my bikes just about as much as riding them.

One thing I've been thinking about concerning this subject: Is Racetech/Lindemann/Aftershocks/Traxxion too race oriented? As an analogy, do you think that even though both types of bikes are out and out race bikes, don't you imagine there is a completely different setup for an Isle of Mann type bike vs. a MotoGP bike? The Isle of Mann doesn't look near as smooth as Laguna Seca.

I live the metro Atlanta area. I've either raced or done track schools at Road Atlanta (both original and current), Savannah, and Jennings in this area. I can tell you for a fact, those tracks a lot smoother than the roads and highways of north GA (Highway 60, Wolf Pen Gap Road, etc).

We run one tire setup/pressures for track days vs. the street. Would we not do the same with spring rates and compression/rebound rates?

 

Maybe, thou I can say My setup works great for the track as well as the street less it's a bit stiff for the street, sure works great when called upon, so for me it's more a tire issue. if I'm on the track I'm getting the best rubber possible, for the street its a bit different, still want the best tire just a different use factor being applied.

 

I spoke with Jim Lindemann last Friday evening (I'm east coast, he's west coast).

He told me to do the old "10/20" measurement to see if I had the correct shock spring rate. He said the bike should have 10 mm of sag without the rider aboard (static sag) and then sag an additional 20 mm when I mount the bike.

I measured mine last night. I had 4 mm static sag and 31 mm dynamic sag. That would seem to indicate to me that I might be a little stiff on the spring.

I wrote Jim about these numbers and am waiting to hear back from him.

 

Heard back from Jim. He said he has never specified anything heavier than a 1300 # spring for a VFR. I think I will try one. They're easy to get.