Gen III Non-ES fork upgrade?

[MCRIDER007]

But there is good reason to be dubious of the FSM specs. For instance, on the 3rd Gen ES they claim to have two single rate springs with 2.0 kg/mm rates. That is ludicrous. Perhaps they meant the sum of the two is 2.0 kg/mm, which would be much more believable, but why change from the normal method of spring rate spec now?

I think they meant the sum of the two is 2.0kg/mm but I have never seen fork spring rates expressed that way. Since I currently have both a 13A and a 14ES its been pretty easy to compare the suspensions and when riding in a straight line I don't think I could tell which which forks were attached to the handlebars in a blind test....which is pretty amazing since the damping designs are so different between the bikes. Any riding that involves putting stress on the frame is a different story, the inverted forks on the ES is a very nice improvement.

 

[MCRIDER007]

I have a 09 with 013 forks. I put the 09 forks on the 013 with AK-20s. Both scooters have Penskes. I'm always amazed when I take the 09 out and the excellent feel. If I were starting from scratch, I'd go 013 forks with a Penske. The 013 forks are not half bad.

Sounds like the 013 forks are pretty good.

 

[Fred W]

I hope that this is not drifting too far off the OPs intended discussion, but in thinking about "dual rate" springs, there are lot of nebulous thoughts that bounce around my head. One is: when one specifies two distinct spring rates, does each rate also take into account the influence of the other spring rate? When you are applying a load to the spring, the entire spring will want to compress, not just the weakest part alone.

So while they may say the lower spring rate is .85kg/mm is that the rate of the spring if there were no higher rate stage on top of it? In other words, if they were two unique shorter springs stacked up? When you lengthen the spring and put a second 1.0 kg/mm rate in series with the .85, wouldn't that lower the .85 somewhat?

Also, how exactly would one wind a single spring that transitions immediately from one rate to another? There should always be a coil or two that are "in between" the two desired rates, and that should create a transitional spring rate for some finite amount of the spring's travel. Plus the stiffer spring would still be compressing (albeit at a much lesser rate) as the weak spring compresses until it is coil bound.

This is the kind of mental exercises one comes to at ~3AM after you get up to take an leak and then are unable to get back to sleep.

 

[MCRIDER007]

I hope that this is not drifting too far off the OPs intended discussion, but in thinking about "dual rate" springs, there are lot of nebulous thoughts that bounce around my head. One is: when one specifies two distinct spring rates, does each rate also take into account the influence of the other spring rate? When you are applying a load to the spring, the entire spring will want to compress, not just the weakest part alone.
So while they may say the lower spring rate is .85kg/mm is that the rate of the spring if there were no higher rate stage on top of it? In other words, if they were two unique shorter springs stacked up? When you lengthen the spring and put a second 1.0 kg/mm rate in series with the .85, wouldn't that lower the .85 somewhat?

Also, how exactly would one wind a single spring that transitions immediately from one rate to another? There should always be a coil or two that are "in between" the two desired rates, and that should create a transitional spring rate for some finite amount of the spring's travel. Plus the stiffer spring would still be compressing (albeit at a much lesser rate) as the weak spring compresses until it is coil bound.

Its my understanding that with dual rate or progressive rate (which are pretty rare) springs, each coil in the spring compresses at the same rate and the change in the spring rate occurs when one or more coils binds thereby reducing the number of active coils and increasing the effective spring rate. Obviously, if you have 5 tightly wound springs there is going to be a slight delay from when the first and last coil binds and that will be the transition phase from the soft to the hard rate.

Most of the dual rate springs I have seen are essentially single rate because the tight coils are already bound when the weight of the bike and rider is applied. I was able to almost completely bind the tight coils on one set of aftermarket FJR dual rate springs by standing it straight up and pushing down with my hands. The worst dual rate springs I have seen were the OEM springs on a 2003 Goldwing that had 90mm of fork sag with the rider's weight. The tight coils were completely bound way before that point.

I think the idea behind dual rate springs is be able to ride on the soft rate and then have a much harder rate available to avoid bottoming during heavy braking. If so, then the tight coils should make up at least 2/3rds of the spring's length rather than 1/4-1/3 of the spring's length. In any case, linear springs are going to give more consistent damping than dual rate springs.

 

[Fred W]

Yeah... I'll have to do some more research (which would be anything greater than the none that I have done so far) but I do not think that it works that way in the world of physics. It just seems intuitive to me that when applying a particular load force to one end of a compound spring that the weaker springs would compress more than the stronger springs, but that they would all compress somewhat. I'll have to suss that out some to be sure.

None of which is particularly important except during those 3AM brain storms.

 

[MCRIDER007]

Yeah... I'll have to do some more research (which would be anything greater than the none that I have done so far) but I do not think that it works that way in the world of physics. It just seems intuitive to me that when applying a particular load force to one end of a compound spring that the weaker springs would compress more than the stronger springs, but that they would all compress somewhat. I'll have to suss that out some to be sure.

A coil spring's rate is a factor of the quality of steel, thickness of the coils, and how many coils are in any given length of spring. Unless a dual rate spring contains different steel or a different thickness in some of the coils the resistance of each coil will be the same, and each coil will compress the same distance regardless of the spacing of the coils. If you take a linear spring and cut it in half, each piece will have twice the spring rate of the original....sounds crazy but when you half the number of coils, each coil has to compress twice as far when the spring is compressed any given length.

When the tightly wound coils bind, it changes the ratio of active coils to the remaining length of spring which changes the spring rate.

 

[DaJudge]

I hope that this is not drifting too far off the OPs intended discussion, but in thinking about "dual rate" springs, there are lot of nebulous thoughts that bounce around my head. One is: when one specifies two distinct spring rates, does each rate also take into account the influence of the other spring rate? When you are applying a load to the spring, the entire spring will want to compress, not just the weakest part alone.

No worries Fred.

My questions have been well and truly answered. Besides, I learn something interesting whenever you and MC have a discussion like this.

I'll have to show this one to my Mech.E. son when he comes to visit later this week. I'll also have him serve as my extra set of hands during the fork oil change.

 

[escapefjrtist]

I have a 09 with 013 forks. I put the 09 forks on the 013 with AK-20s. Both scooters have Penskes. I'm always amazed when I take the 09 out and the excellent feel. If I were starting from scratch, I'd go 013 forks with a Penske. The 013 forks are not half bad.

Interesting...I did the same thing with my [new] used '15A by transferring GP equipped forks and Penske from my '09 before it was sold. Couldn't get past the idea of giving up the GP forks in exchange for the stock peg leg set-up, no matter how well it works. Gotta say though, when I rode the '09 one last time it was smooth as glass and felt wonderful. New owner was certainly pleased to get essentially brand new forks and shock too!

YMMV

--G

 

[RaYzerman19]

I have a 09 with 013 forks. I put the 09 forks on the 013 with AK-20s. Both scooters have Penskes. I'm always amazed when I take the 09 out and the excellent feel. If I were starting from scratch, I'd go 013 forks with a Penske. The 013 forks are not half bad.

Interesting...I did the same thing with my [new] used '15A by transferring GP equipped forks and Penske from my '09 before it was sold. Couldn't get past the idea of giving up the GP forks in exchange for the stock peg leg set-up, no matter how well it works. Gotta say though, when I rode the '09 one last time it was smooth as glass and felt wonderful. New owner was certainly pleased to get essentially brand new forks and shock too!

YMMV

--G

I woulda done the same as I wouldn't have figured peg leg could be better than the aftermarket stuff. But, I'll say I didn't think the stock valving on Gen 1 or 2 was bad, mostly just the springs were weak. And conventional wisdom around here was put straight rate springs in. Gen 3's got the uprated springs, the weakness of prior Gen's, and sounds like it's a happy thing so far.

The OP however is 250 lbs, might be on the edge of needing something extra someday down the road. Straight rate springs to start?

 

[MCRIDER007]

I have a 09 with 013 forks. I put the 09 forks on the 013 with AK-20s. Both scooters have Penskes. I'm always amazed when I take the 09 out and the excellent feel. If I were starting from scratch, I'd go 013 forks with a Penske. The 013 forks are not half bad.

Interesting...I did the same thing with my [new] used '15A by transferring GP equipped forks and Penske from my '09 before it was sold. Couldn't get past the idea of giving up the GP forks in exchange for the stock peg leg set-up, no matter how well it works. Gotta say though, when I rode the '09 one last time it was smooth as glass and felt wonderful. New owner was certainly pleased to get essentially brand new forks and shock too!

YMMV

--G

I woulda done the same as I wouldn't have figured peg leg could be better than the aftermarket stuff. But, I'll say I didn't think the stock valving on Gen 1 or 2 was bad, mostly just the springs were weak. And conventional wisdom around here was put straight rate springs in. Gen 3's got the uprated springs, the weakness of prior Gen's, and sounds like it's a happy thing so far.

The OP however is 250 lbs, might be on the edge of needing something extra someday down the road. Straight rate springs to start?

Guess I am the odd man out. I had an 08 with the GP forks and a economy Wilber's shock and after riding both bikes back to back for a month I decded I liked the '13 OEM Shock better than the Wilber's and since the forks seemed to be equal, I decided to keep the '13 stock suspension. I did get an extra $500 for the suspension when I used the 08 as a trade in on my '14ES.