2013 Front springs replacement

[@rjen]

This weekend our dutch FJR Community had an organized 'tech day' at a dutch Suspension specialist: HK Suspension.

I used this opportunity to replace my rear shock (Ohlins YA-053) and front springs.

Since mine was the first 2013 they got into the shop it was quite interesting to find out what the new springs look like. Here some answers.

To start:

the 2013 model is the first FJR where the front legs are not identical: preload is adjustable on both legs, Damping can only be adjusted on the right leg.

As a result the interior of both legs is slightly different as well...

The disassembly in pictures:

Right leg: on the outside not much difference from older models

First sight of the spring. First observation: the 'filler tube' on top of the spring is shorter than it use to be.

The spring, no surprise yet:

And there it is... it's progressive!

Minimizing weight by Yamaha: the insides are indeed made of aluminium...

Another observation: the needle is now 'loose' in the tube. Got to be careful not to lose it or put it back in upside down...

Spring comparison: behind a Gen2 spring with filler tube, upfront the taller Gen3 spring. As it turns out the total length has remained the same.

Measuring the spring strength: this turns out to be unchanged.

Now the left leg: the filler tube here is completely different:

At this point we established that is is possible to use a Gen2 aftermarket spring in the Gen3. We have installed a set of Wilbers springs. Since these are effectively the length of the Gen2 Yamaha springs we have used the old Gen2 filler tube on the right leg, and created a new tube (aluminium) with the same length for the left leg.

The new tube in comaparison to the Yamaha Gen3 tube:

In overview from left to right:

1. A Gen2 spring with the old -taller- filler tube
2. The longer Gen3 right leg spring with original filler tube
3. The longer Gen3 left leg spring with original filler tube
 

 
Assembly was a piece of cake.
 
Some notes from the suspension specialist:

• Damping of the Gen3 was judged to be fairly soft. To improve this a different grade of fork oil was used after replacement (grade 10)
  
• Air chambers in the legs were of different size (10 cm right side, 12 cm left side). We found no explanation for this. After replacement both were set to 10 cm.
  
• Settings with the new springs in: rebound unchanged (3 rings), 10 clicks damping topside, 8 clicks damping bottomside.
  

Results:

I rode about 300km since including highway and twisties: the Gen3 feels great. Lot of precision, very predictable both in long and short corners, a littje less comfortable than the factory settings but well worth it in improved sports riding...

 

 

[Enn]

Great report, @rjen, very well documented. Thanks for posting!

 

[VMaxChuck]

Great post! Thanks!!

 

[Fred W]

Thanks for the great pictures. Now we all know what's in there.

What spring weight were the Wilbers springs that you used? Heavier than stock I assume?

How did you arrive at the 10 and 8 clicks adjustments for the damping? With a heavier weight oil in there you would expect to have to open the damping adjusters up to be in the same ballpark. Of course with the heavier spring you would require more rebound damping and less compression damping than stock.

Since those were the only changes to the forks, one of them must be responsible for it feeling "less comfortable." Less comfortable probably means that something isn't quite right still.

 

[MCRIDER007]

Thanks for the pictures, I sure don't see any improvement over the GEN2 forks. I consider the springs to be dual rate rather than progressive and they are the same worthless design that Honda uses in the Goldwing, I say worthless because the soft end of the springs are totally used up by the weight of the motorcycle so the dual rate does not serve any useful purpose. I am going to take a wild guess that the damping pistons are the same cheap design used in the GEN2 and the GEN3 needs the same fork upgrades to achieve its "sport" potential.

 

[@rjen]

The damping adjustment setting was made by the suspension expert, not me.

But I believe your thinking is correct: I had already adjusted the standard settings for damping, since I found these too soft. Prior to replacing the springs I had them set to 8 (top) and 5 (bottom).

The "less comfortable" is due to the harder springs. As a result there is more direct contact with the road surface. In my opinion it is not possible to fully combine comfort (softness) with sportier settings, but we can still try some fine-tining over the next few weeks...

I forgot to ask what 'weight' spring was used, but yes, they are heavier....

 

[yamafitter]

Since those were the only changes to the forks, one of them must be responsible for it feeling "less comfortable." Less comfortable probably means that something isn't quite right still.

I could say that then I did the suspension upgrade on my bike that it felt "less comfortable" in the way a sports car is less comfortable than a Buick. That doesn't necessary mean anything is wrong. It all depends on what results you are attempting to achieve.

I would suspect that going from the longer progressive springs to the shorter straight springs is mostly responsible for the change though the change in fork oil from 5W to 10W would definitely have an effect on the dampening. The OP also stated that they went to a heavier spring. Going to a 10W fork oil probably will help better dampen the heavier springs since all the dampening is occurring in the one fork leg.

 

[Fred W]

Best of luck with the tuning!

 

[yamafitter]

It will be interesting to see what Ohlins or GP Suspensions take on this will be. Newer does not always mean better, just ask Chad Reed over in the Supercross series. In the last race they finally pulled Honda's new air suspension off the bike and have gone back to last year's design.

 

[Fred W]

I would suspect that going from the longer progressive springs to the shorter straight springs is mostly responsible for the change though the change in fork oil from 5W to 10W would definitely have an effect on the dampening. The OP also stated that they went to a heavier spring. Going to a 10W fork oil probably will help better dampen the heavier springs since all the dampening is occurring in the one fork leg.

The Wilbers springs used still look progressive to me. But I'm sure it is stiffer all through its range.

But, a stiffer spring doesn't always mean a stiffer suspension. If you back off the slow speed compression (only compression damping adjustment available) damping the total compliance to bumps would still be the same.

I am also assuming that although there is only adjustment in one fork leg but that both legs have oil in them, so both contribute to the total damping. Going to a considerably heavier weight oil (the stock is actually more of a 3 weight) will cause all damping to increase. The adjustable part and the un-adjustable too.

 

[@rjen]

Please bear in mind: the springs showing in the pictures are the Gen3 and Gen2 original springs. I actually forgot to take a picture of the new springs and only realized this once they were already installed ...

The new Wilbers springs used are progressive and for those of you who know what this means: spring strength of the standard Yamaha spring was measured at 75-90 progressive. The new ones are 70-100 progressive.

 

[Fred W]

Oh, I thought that one of the pics showed the Wilbers. My bad.

But if the old ones were 75-90 and new ones are 70-100 then this is even more reason to think that the damping changes are what is causing the loss of "comfort." I am interpreting loss of comfort at mean less compliance to bumps. The new spring should actually be more compliant to small bumps since the initial spring rate is softer.

 

[ahchiu]

Great writeup, I would not take his discription of less comfort to be a bad thing, I'm just guessing but maybe he meant he can feel the road more with this setup.

 

[Fred W]

That very well may be. Only way to know is if it doesn't get any better with adjustment.

 

[MCRIDER007]

Oh, I thought that one of the pics showed the Wilbers. My bad.
But if the old ones were 75-90 and new ones are 70-100 then this is even more reason to think that the damping changes are what is causing the loss of "comfort." I am interpreting loss of comfort at mean less compliance to bumps. The new spring should actually be more compliant to small bumps since the initial spring rate is softer.

If you measure the spring rate on a workbench then the initial spring rate is going to be softer, however if you look at the "soft" end of the spring, the tightly wound coils at the end of the spring; they are going to completely bind once the bike is off the centerstand, specially with the rider's weight. There really is no softer initial rate with this type of spring, its just marketing hype.

I bought the Wilber's fork springs in the 2006 group buy and followed their instructions to use 7.5 wt fork oil. It definitely had a firmer feel and nice ride on smooth surfaces. However, when those springs were tested by GP Suspension, they were the same rate as the OEM springs, just 15mm longer and the firmer feel was due to the heavier oil. The FJR OEM high speed compression damping is essentially a spring loaded relief valve that is either open or closed, using heavier oil may give what feels like a firmer ride over smooth surfaces but its going to result in a harsher ride over bumps, especially large bumps.

 

[Fred W]

If you measure the spring rate on a workbench then the initial spring rate is going to be softer, however if you look at the "soft" end of the spring, the tightly wound coils at the end of the spring; they are going to completely bind once the bike is off the centerstand, specially with the rider's weight. There really is no softer initial rate with this type of spring, its just marketing hype.

Interesting. I have heard similar thoughts about progressive springs before, but you would think that if this were completely true that OEMs with advanced design engineers, like Yamaha as an example, wouldn't fall for it. Why would they go to the bother and expense of having the progressive springs stock if there is no real benefit?

I guess the theory could be tested easily enough. Just compress the spring on the bench and measure at what length the soft part is spring bound. That would translate to the fork travel and could be compared to the dynamic sag measurement to see how bound up that softer part of the spring really is.

Of course there will still be some progressive resistance to compression, even on a straight wound spring due to the air in the fork leg.

 

[@rjen]

I have been in touch with HK suspension today, and they advised my to adjust up the damping considerably for starters and test if this softens up the ride. If not, it is the spring itself.

Just did some tests on a 60 minutes ride. Softening up damping with 10 clicks to start helps considerably. After a few more tests I ended up with a new setting: 15 clicks damping topside, 13 clicks damping bottomside.

At this time it seems the best balance between 'firmness' and comfort...

 

[MCRIDER007]

If you measure the spring rate on a workbench then the initial spring rate is going to be softer, however if you look at the "soft" end of the spring, the tightly wound coils at the end of the spring; they are going to completely bind once the bike is off the centerstand, specially with the rider's weight. There really is no softer initial rate with this type of spring, its just marketing hype.

Interesting. I have heard similar thoughts about progressive springs before, but you would think that if this were completely true that OEMs with advanced design engineers, like Yamaha as an example, wouldn't fall for it. Why would they go to the bother and expense of having the progressive springs stock if there is no real benefit?

I guess the theory could be tested easily enough. Just compress the spring on the bench and measure at what length the soft part is spring bound. That would translate to the fork travel and could be compared to the dynamic sag measurement to see how bound up that softer part of the spring really is.

I was thinking the same thing. The GEN3 springs are not progressive, they are dual rate. True progressive springs start with a tightly bound coil and each succeeding coil is less tightly wound and when you get to the end the gaps between the coils are 2-3 times are large as the other end. I bought several of these fork springs from Progressive Springs in the 80s. You change a spring rate by reducing the number of effective coils and a progressive spring reduces the number of coils through out the springs compression. Dual rate springs however, have one set of coils that are tightly wound and another set that are widely spaced. As weight is applied to the spring, all coils compress equally (at the soft rate) but when the tightly bound springs bind, the number of effective coils is greatly reduced and the spring rate jumps to the higher spring rate....and this happens pretty quickly. My Tenere has dual rate springs that transition at 75mm of sag, just about the middle of the compression used when riding over large bumps....those that have switched to linear springs to avoid that transition (from .86 to 1.2 kg) have been very satisfied with the results.

 

[Fred W]

OK, but it just sounds to me like a dual rate spring is just a different implementation of being progressive in steps rather than, well... progressively.

At least from a purely theoretical standpoint the latter sounds like a better idea.

Thinking out loud here, I'll bet the down side of having a progressive spring is that you don't also have progressive rebound damping. Since the rebound is determined completely based on how fast the spring wants to extend the unweighted fork, it could only be optimized at one point along the fork/spring stroke vs a straight weight spring once optimized it should be right for the entire stroke.