Rear Suspension - Ohlins or Penske?

[Fuzzy]

Setting up a ride in to GMD in north Georgia for suspension upgrade. Racetech gold valves and springs for forks. They recommend Penske over Ohlins for rear shock. Any thoughts here?

He is checking to make sure Penske has one for NC, so if not decision is easy.

 

[Beemerphile]

I bought my Ohlins at Hard Racing LLC. They rep and recommend both as first quality shocks. I think you could safely choose on features, availability, and cost. Penske is US made and rebuildable. The Ohlins I got had limited adjustability and thus lower cost. Penske makes a "budget" shock for about the same price but claims a limited model span for it. You might be looking at a higher-end Penske shock unless they have introduced something recently. Properly spec'ed when purchased, I have not missed not having a trio of expensive knobs on mine. Make sure you are comparing similar equipment levels (single, dual, triple adjustable, rservoir style, etc.).

 

[Fuzzy]

Both budget in $650 cost range.

 

[Beemerphile]

Both budget in $650 cost range.

Probably a toss-up. You say they recommend Penske over Ohlins, do they have both available for sale, or does their recommendation just happen to be the one that they have? If they have and sell both, then it is a stronger recommendation. Either way, it is most likely a safe bet.

 

[Fuzzy]

I found GMD on Racetech’s web page as the only Racetech center in the area. I don’t want to do the front shock modification in my driveway without a shop or even garage and prefer ride in to sending parts off and not being able to ride while I wait.

Talking on the phone found out he just had an NC in shop whose owner had a flat and rode on the rim too long. Owner let him ride the NC on some back roads and he was impressed with it although he also experienced the limitations of the suspension. Said he wants one for off road riding with upgraded suspension and fat bars.

On the Penske vs Ohlins he sells both. He has a preference for Penske but not a big one. Price is the same. He is checking whether Penske has a basic one designed for the NC yet. I plan to buy the basic of one or the other with price around $650 for either.
He also said he could do a gold valve and spring job on the rear. Problem is Racetech does not have a kit yet so he would have to buy springs elsewhere. Springs come in 1” lengths and NC shock has less than 1” adjustment so he would have to fabricate spacer to get preload right. Cost would not save anything over Ohlins or Penske and they would be a better shock so why bother. If Racetech comes out with a kit including spring that equation could change. He expects this is just a matter of time. Maybe if a bunch of NC owners contacted Racetech they would get busy with it….

 

[Old Can Ride]

Ohlins or Penske are both great rear shocks. If adjusted properly both are just about impossible to bottom out, but both are stiffer than the OEM shock.

 

[Chestnut]

What mileage does Penske recommend before you do a rebuild?

 

[Fuzzy]

Mine will be a Penske. Received this from dealer:

We have the Penske ordered. Yes, they can build it. Ohlins had some, sold out and are not making anymore.

Not sure what this means for someone wanting an Ohlins rear. I would assume it is more like not making anymore this month with August vacations.

Ride in scheduled for September 19 on way to a MP3 gathering at Cumberland Falls St Park in SE Kentucky. Should have about 1000 miles on it by time I get home.

 

[Antarius]

Ohlins or Penske are both great rear shocks. If adjusted properly both are just about impossible to bottom out, but both are stiffer than the OEM shock.

They are as stiff as you set them up to be. The stock shock does not work like a shock should, as its rebound is directly related to the amount of preload you have set in the shock. A Penkse or Ohlins will work much better in that each component -- compression, rebound, and preload are all separate and act separately from one another.

You could set your preload on the Penske to have a 300lb rider, and the rebound and compression dampening will feel the same as when you had the preload set for a 100lb rider. With the stock shock, when you increase the preload you also DECREASE the rebound dampening and INCREASE the compression dampening.

In layman's terms, if you set the stock shock preload higher than "factory" because, well, you arent a small japanese man or you ride 2-up, you would be making the compression dampening increase (in other words, STIFFER) and you would be decreasing the rebound dampening (in other words, making the wheel push back into the ground AFTER hitting a bump FASTER -- I.E., feeling more bumpy). This is why with the stock shock you can feel it more or less "scatter" across big bumps -- the shock when set for your weight has made the compression too stiff and the rebound too fast, so you essentially feel 2 bumps for each bump you hit -- the initial point of impact and the wheel slamming back down to the pavement.

A Penske or Ohlins adjustable shock will not do this. You will be able to successfully control the rate of the wheel as it first impacts a bump, rolls over the bump, and then finds its way back down to the smooth pavement. When your settings are figured out correctly, you will have a *SMOOTHER* ride than stock, AND you will be able to adjust your preload for when you have that second rider or when you gain weight or put your saddle bags on, without it affecting the tires ability to follow the roadway.

So, sorry to say, but the "Penske and Ohlins are stiffer" comment is just patently false. If you set them up correctly, the wheels will FOLLOW the roadway rather than bounce over bumps and thus, will be smoother *AND* offer more grip.

 

[Fuzzy]

The vendor asks a umber of questions for the setup prior to sale, most around weight and type of riding. For me weight can swing 100 pounds when I load up fr travel / camping. He wanted to know if optimum setup should be with or without extra weight. Correct spring must be installed. When you adjust preload on a progressive spring the stiffness will change a bit. Only user adjustment on low end shocks is preload.

No personal experience yet but here is Beemerphile's critique.

The RaceTech /Öhlins suspension is night and day vs. the original suspension. There is a bridge that I cross often that is about an inch higher than the road, so there is a square edged step change in the pavement when you get to the bridge. With the stock suspension it physically hurt in the lower back to hit the bridge at road speed. My TMax had the same result. My BMW with Wilber's suspension acted like it wasn't there. Post modification, the NC is almost BMW-like now when crossing the step. There is a little more feel, most likely because of the lighter weight of the NC, but it is quite comfortable. I took a couple of dirt/gravel roads and it was extremely plush. Amazingly, it is a firmer suspension than stock, yet much more supple and plush than before. Best of both worlds. I consider this a must-do modification. Ranking them, I think the front is the most important.

 

[670cc]

They are as stiff as you set them up to be. The stock shock does not work like a shock should, as its rebound is directly related to the amount of preload you have set in the shock. A Penkse or Ohlins will work much better in that each component -- compression, rebound, and preload are all separate and act separately from one another.

You could set your preload on the Penske to have a 300lb rider, and the rebound and compression dampening will feel the same as when you had the preload set for a 100lb rider. With the stock shock, when you increase the preload you also DECREASE the rebound dampening and INCREASE the compression dampening.

In layman's terms, if you set the stock shock preload higher than "factory" because, well, you arent a small japanese man or you ride 2-up, you would be making the compression dampening increase (in other words, STIFFER) and you would be decreasing the rebound dampening (in other words, making the wheel push back into the ground AFTER hitting a bump FASTER -- I.E., feeling more bumpy). This is why with the stock shock you can feel it more or less "scatter" across big bumps -- the shock when set for your weight has made the compression too stiff and the rebound too fast, so you essentially feel 2 bumps for each bump you hit -- the initial point of impact and the wheel slamming back down to the pavement.

A Penske or Ohlins adjustable shock will not do this. You will be able to successfully control the rate of the wheel as it first impacts a bump, rolls over the bump, and then finds its way back down to the smooth pavement. When your settings are figured out correctly, you will have a *SMOOTHER* ride than stock, AND you will be able to adjust your preload for when you have that second rider or when you gain weight or put your saddle bags on, without it affecting the tires ability to follow the roadway.

So, sorry to say, but the "Penske and Ohlins are stiffer" comment is just patently false. If you set them up correctly, the wheels will FOLLOW the roadway rather than bounce over bumps and thus, will be smoother *AND* offer more grip.

I don't know a lot about suspensions and I'm trying to learn. As I understand it, the spring and the shock are two separate devices but in a motorcycle they are built into one assembly. They could be separate assemblies, as they are for example, on a truck, or combined as on a motorcycle.

The preload you mention I assume is spring preload. Or, in other words, setting the sag or the ride height. The spring rate itself is a function of the spring, and the spring rate cannot be changed without swapping out the spring for one with a different rate.

The dampening is controlled solely by the shock with internal valving. On the stock shock, the valving is not adjustable.

You said that on the stock shock assembly, that increasing the (spring) preload setting would increase the compression dampening and decrease the rebound dampening.

So, how does altering the mounting point of the spring (preload, sag, ride height), have any affect at all on the dampening rates, which is a function of the shock? In the case of the truck example, with separate springs and shocks, how would putting a spacer under the spring (preload) have any affect on how the shock dampens suspension movement?

Just trying to understand . . .

Greg

 

[Antarius]

Greg,

You are correct in how a properly designed and manufactured / valved shock is supposed to work in terms of preload.

In the real world, a lot of OEM shocks (including our NC's) are a low quality shock with poor dampening and valving inside. As a result, the preload spring becomes a part of the working shock. To make it simple, the valving of the shock can't keep up so you end up also feeling the spring rate as the shock fails to dampen the rebound or compression and you go pogo'ing down the road on the preload spring as it tries to reset to its sag height.

What should happen is a shocks valving should be good enough to set it in a manner that when you, say, go over a large bump, the compression and rebound dampening are controlling the rate of the rear wheel both up and down as it travels over the bump. If it cannot keep up, the shock will "unload" and when it does that, it's effectively using the preload spring to do that. Then it unloads, usually higher than it should, and then it settles back to where it should "sit" based on your preload setting.

Our OEM shocks are hopeless in keeping up with rough roads as the valving is poor and there's no adjustment. This means you are going to be feeling that spring, and as such, your preload setting will change the ride quality as I described. It isn't actually adjusting the dampening in the shock, I was just describing what it would feel like (too much compression and too little rebound dampening) to illustrate what cranking up the preload will do to a low quality shock in terms of performance and feel.

Don't get me wrong though, a $1000 shock will so the same if you crank the preload up and turn the compression knob all the way in and rebound knob all the way out. The difference is on a quality shock, it's an adjustment you can make to fix the problem.

 

[Antarius]

Greg,

You are correct in how a properly designed and manufactured / valved shock is supposed to work in terms of preload.

In the real world, a lot of OEM shocks (including our NC's) are a low quality shock with poor dampening and valving inside. As a result, the preload spring becomes a part of the working shock. To make it simple, the valving of the shock can't keep up so you end up also feeling the spring rate as the shock fails to dampen the rebound or compression and you go pogo'ing down the road on the preload spring as it tries to reset to its sag height.

What should happen is a shocks valving should be good enough to set it in a manner that when you, say, go over a large bump, the compression and rebound dampening are controlling the rate of the rear wheel both up and down as it travels over the bump. If it cannot keep up, the shock will "unload" and when it does that, it's effectively using the preload spring to do that. As in, the spring is trying to bring the bike back to its preloa setting. Without proper rebound dampening, it will "overshoot" where it should rest (as in, it's rising or unloading too quickly), and then your weight and the bike squish the spring again and compress it to its correct "sag" setting. This is what makes you feel like the bike is kicking you in the ***. You hit a bump, the compression valving is too slow to work properly so you feel it. The rebound is too fast so it bounces, and when this happens rapidly the shock unloads and boingggg you go feeling the shock trying to settle back on the spring to its preload setting as the valving is for all intents and purposes, ineffective.

With ineffective valving, more preload will do this faster and less will so it slower. Neither are good for performance or comfort.

Our OEM shocks are hopeless in keeping up with rough roads as the valving is poor and there's no adjustment. This means you are going to be feeling that spring, and as such, your preload setting will change the ride quality as I described.

Don't get me wrong though, a $1000 shock will so the same if you crank the preload up and turn the compression knob all the way in and rebound knob all the way out. The difference is on a quality shock, it's an adjustment you can make to fix the problem.

**EDIT**

I realized I didn't explain part of this as simply as I could: On a motorcycle shock, the preload spring does exactly that -- it PRELOADS the spring to a set rate. The spring is ALWAYS trying to lengthen the shock. The degree to how hard the spring is trying to lengthen the shock is determined by how much preload you add to the spring -- more preload tightens the spring and makes it use more force to lengthen the shock. The only thing regulating the rate which the spring successfully "unloads" (or lengthens) the shock is the rebound valving -- and the riders weight. The opposite is true for compression valving. If the shocks valving is inadequate -- which ours and most stock shocks are -- it simply becomes overwhelmed and at that point the spring is free to "unload" (or lengthen) the shock at will, when you hit a bump and you temporarily lighten the amount of pressure on the seat due to the physics of, well, hitting a bump.

 

[DirtFlier]

[A Penkse or Ohlins will work much better in that each component -- compression, rebound, and preload are all separate and act separately from one another...With the stock shock, when you increase the preload you also DECREASE the rebound dampening and INCREASE the compression dampening.]

All the adjustments of the shock affect other areas so there is no real isolation. Spring preload is totally different than opening or closing valves that control damping in either direction, and although preload has nothing to do with those valves, it feels like it does so it's reality.

 

[NC Rick]

With regard to servicing shocks, the manufacturers recomended interval should not be confused with quality or longevity. As you asked about Ohlins and Penske ( both brands I am very experianced with) the actual requirements are going to be very similar. Likely, the need to service them would not be more than the stock oem shock you replace. The biggest difference is that you are purchasing a top quality product that was designed to be serviced and has a ready supply of reasonably priced parts. If asked about a specific point in those shocks that may need more attention than an oem shock, I would say that the shaft seal system used is a little less focused on pure reliability but engineered to provide a higher level of performance at the possible cost of slightly more susceptibility to damage or wear related leakage. I don't think there is any hard, statistical numbers to support my view and this can be dependent on so many outside factors. I personally pick the better performing seal type all day long.

My recommendations for servicing suspension components centers on 2 years, 20,000 miles. Riding style and conditions weigh heavily on the actual needs so YRMV.

 

[drdubb]

Check out Cogent Dynamics. I think they are making a rear shock and fork valving for the NC700x. I have their suspension on my DR. Transforms the bike.
Give' em a call.

 

[DirtFlier]

[Check out Cogent Dynamics. I think they are making a rear shock and fork valving for the NC700x.]

They have an excellent reputation, plus I have two close friends who have their stuff (forks & shock) and they both rave about the transformation. Neither bikes are NCs but I'm sure they can do their magic on our bikes.

 

[L.B.S.]

Threaded Spring Preload

"Threaded pre-load (Tpl) is accomplished by turning a threaded collar. As you adjust the threaded collar, which compresses the spring, it will increase the spring pre-load. Increasing Spring Preload moves the spring further into its travel and makes the shock “feel” stiffer initially, and makes the chassis sit a little higher (less sag/more ride height)."


"Spring Pre-load and spring rate - CHANGING PRE-LOAD DOES NOT CHANGE SPRING RATE. You don’t get a stiffer spring by adding pre-load. Rather you change the weight point at which the spring starts to move. Once the spring starts to compress it will move at its spring rating.

Example: Using a 100 pound linear-rate spring, preloaded one-quarter inch, would take twenty-five pounds of force before it would further compress. In effect the spring will not compress until 26 pounds of force were applied. The spring rate however has not changed, even though it initially takes 50 pounds of force to move the initial one-quarter inch, it would continue compressing one-quarter inch for every additional 25 pounds of force applied throughout the active length of the linear-rate spring, until the coils touch each other (bind)."

This is what forever caught me out, always being told that upping the preload of the spring didn't result in a stiffer spring, yet my a** could instantly feel that the bike DID feel stiffer, nonetheless. I guess it's that initial sag compression factor that influenced my (and others) thoughts regarding the spring being stiffer throughout it's travel; versus just the first amount of rider /passenger/luggage sag being taken up by however much the preload was cranked to.

 

[NC Rick]

Nice post L.B.S.! As sort of a thought experiment, think of a stiff spring out in the garage, not in a bike. If we step on it, balance all our weight on it, we compress it to a degree based on the springs rate and how much we weigh. Same thing happens on the bike, it is just the total portion of the bike and rider that compresses the spring. Add "preload" and the spring is not compressed any more (as long as there is still some "sag"). What the "preload" adjustment will do is change the position of the suspension within its practical travel. We want to target some number like one third of the full travel so that around two thirds travel is usable for absorbing a bump and one third is there to allow the wheel to "droop" into a roadway depression, for example. All this is a very simplified and basic model of the total dynamics involved. Often, the dynamics dictate that there is much less than all the bikes weight on the wheel (think about going over a steep ramp to railway tracks where it would be easy to have a negative weight on it (like when the bike jumps). I think it is this factor that makes my butt feel a higher stiffness ;-)

 

[bamamate]

Thanks Rick. I finally understand preload.