New suspension settings

[harper]

I took the Fred W plunge today and followed his instruction set. I measured the front fork sag at 50mm so I went from one line showing to zero lines showing on the spring pre-load settings. This puts line 1 at the top of the adjustment nut. This brought the front fork sag down to 39mm. It made me more confident to mark the position of the cable tie with a Sharpie pen so it didn't matter if I bumped it while putting the bike on the center stand. It didn't move with all the jostling but it was still easier to make the measurement to the mark with the cable tie out of the way.

I adjusted the rebound settings as Fred W recommended and found them to critically damp a couple of clicks softer than I had previously dialed in. I toyed with the compression settings but they ended up back at my 12 July settings. The improvement was again noticeable.

My 12 July front fork settings were:

Spring pre-load: L 2 lines R 2 lines

Rebound damping: L 6 clicks out R 6 clicks out

Compression damping: L 8 clicks out R 8 clicks out

My new settings are:

Spring pre-load: L 1 line R 1 line

Rebound damping: L 8 clicks out R 8 clicks out

Compression damping: L 8 clicks out R 8 clicks out

I did not alter the rear rebound setting. I am unable to tell if the rear shock causes the back to overshoot after compressing. I'll try varying it after riding over some different surfaces.

Thanks for the write-up, Fred.

 

[harper]

Remeasured after a three hour ride. Found the front fork sag to be 36mm now. This was measured without changing the damping settings which should theoretically have no affect on the sag. Could be some stickiness but I didn't want to do five measurements and average them.

 

[Fred W]

Glad the adjusting made sense to you.

You are probably right about the difference being stiction related, affected by the heat of riding.

To measure how much stiction you have you'll need an assistant. Start out with (most of) your weight on the bike and have your assistant push down on the front faring and then release it. Move the ty-wrap to the top of the fork leg. Now have assistant lift the front end a bit and release it. The distance between the ty-wrap and the top of the fork is caused by stiction, and obviously less is better.

Just as an FYI... you can set the fork preload somewhere between the lines, if you want. A couple of mm is not that big of a deal.

 

[harper]

Just as an FYI... you can set the fork preload somewhere between the lines, if you want.

Yes, but aligning one of the grooves to the top of the adjusting nut is easy, accurate, and reproducible.

I softened the rear shock rebound damping three clicks and tried it out on a steep, twisty downhill with both hard and soft settings on the spring pre-load. It's remarkable to me how easy it is to alter and then test all of these suspension settings.

 

[HyperPete]

Thread revived from the dead!

I weigh just over 200 pounds. I set my Gen 1 to the settings HaulinAshe recommended in the 1st post. What a huge difference this simple change has made! The previous owner had it much too soft. Now my front end no longer feels as if it is going to shake itself apart on rough roads, and she's much tighter through the corners. The only difference I chose to make is to run the rear shock on soft. It's a Gen 2 shock, and I think the difference in spring rate is stiff enough to run it on soft when I am solo. I'll switch it to hard when I ride 2-up.

Thanks for this very helpful thread! It ought to be a sticky IMO.

 

[Bill Lumberg]

Guys here helped me get closer. My '14 was sketchy before that. Set the front all the way hard. No rings showing. I can run with the rear soft or hard, depending upon whether I'm solo and upon whether I'm riding good roads or interstate.

 

[RaYzerman19]

We did some sag measurements recently, which led me to the same thing (even with the new and improved fork springs over Gen1 & 2 - 0.85) . Cranked down the preload all the way, and it's a definite improvement. What we've done is partially compensated for the progressive part of the spring. The FSM says the stock springs are 0.85 kgf/mm 0-67.5mm and 1.02 kgf/mm 67.5-135mm, which I interpret as soft for the first bit and why they feel like they need more preload for the heavier riders. ES has the same springs but there are no adjusters, so the only option is to use washers/longer spacers if one wants to keep the same springs.

 

[redneckj]

Thread revived from the dead!
I weigh just over 200 pounds. I set my Gen 1 to the settings HaulinAshe recommended in the 1st post. What a huge difference this simple change has made! The previous owner had it much too soft. Now my front end no longer feels as if it is going to shake itself apart on rough roads, and she's much tighter through the corners. The only difference I chose to make is to run the rear shock on soft. It's a Gen 2 shock, and I think the difference in spring rate is stiff enough to run it on soft when I am solo. I'll switch it to hard when I ride 2-up.

Thanks for this very helpful thread! It ought to be a sticky IMO.

The gen 2 rear spring on the hard setting is still not stiff enough unless you are a $150. There are several different ways to improve the suspension. Its all about the money. If you didnt want to spend alot of money, you can always get a Gen 3 rear shock and upgrade your front springs to 1.0's or go with the Hyperpro front setup. If you install 1.0 springs in the front with factory valving I would suggest 10W fork oil.

 

[HyperPete]

Its all about the money.

Exactly. I don't have the money to go for new suspension at this time. It's suitable for me right now. When the money tree bears fruit I will upgrade!

 

[RaYzerman19]

If you can find a GenIII shock, it's almost going to keep you from going aftermarket, it is that good. I was surprised how good it is compared to the RaceTech on my GenII.

 

[MCRIDER007]

Thread revived from the dead!
I weigh just over 200 pounds. I set my Gen 1 to the settings HaulinAshe recommended in the 1st post. What a huge difference this simple change has made! The previous owner had it much too soft. Now my front end no longer feels as if it is going to shake itself apart on rough roads, and she's much tighter through the corners. The only difference I chose to make is to run the rear shock on soft. It's a Gen 2 shock, and I think the difference in spring rate is stiff enough to run it on soft when I am solo. I'll switch it to hard when I ride 2-up.

Thanks for this very helpful thread! It ought to be a sticky IMO.

The gen 2 rear spring on the hard setting is still not stiff enough unless you are a $150. There are several different ways to improve the suspension. Its all about the money. If you didnt want to spend alot of money, you can always get a Gen 3 rear shock and upgrade your front springs to 1.0's or go with the Hyperpro front setup. If you install 1.0 springs in the front with factory valving I would suggest 10W fork oil.

Installing 1.0 springs with the factory valving is going to result in a harsher ride over bumps or rough surfaces but using 10W fork oil is only going to make the problem worse. The biggest drawback with the OEM valving is that the high speed compression circuit does not flow enough oil and 10W oil is twice as thick as the OEM oil even though Yamaha sometimes incorrectly refers to that oil as 10W.

 

[Donal]

The thing I noticed most just after I had installed Racetech Gold Valves with 5W oil was the almost complete disappearance of high frequency, low amplitude vibration. It was a real moment of realisation........

 

[Fred W]

We did some sag measurements recently, which led me to the same thing (even with the new and improved fork springs over Gen1 & 2 - 0.85) . Cranked down the preload all the way, and it's a definite improvement. What we've done is partially compensated for the progressive part of the spring.

Except it doesn't actually work that way. You can't make a spring increase it's spring rate with preload. When you crank up the preload (by any means, either screwing down the adjusters or adding spacers inside) all you are going to do is alter the ride height. The spring will still compress the exact same amount inside after you put a static load on it, and it will still deflect at the same rate from there because the spring rate is the same

The FSM says the stock springs are 0.85 kgf/mm 0-67.5mm and 1.02 kgf/mm 67.5-135mm, which I interpret as soft for the first bit and why they feel like they need more preload for the heavier riders. ES has the same springs but there are no adjusters, so the only option is to use washers/longer spacers if one wants to keep the same springs.

Where did you get that info? The ES has the totally different, upside down forks.

The FSM does says the 2013-2015 A model has a dual rate spring, 0.85 kg/mm & 1.02 kg/mm, but the ES model claims to have a single rate spring for all 135mm of travel. They say it is 2.04 kg/mm, but I assume that to mean the sum of the two fork springs. In any case it is a single, stiff spring rate on the ES. Why they changed how they are specifying the spring rate for the ES is anybody's guess.

 

[ajpagosa]

If you can find a GenIII shock, it's almost going to keep you from going aftermarket, it is that good. I was surprised how good it is compared to the RaceTech on my GenII.

I would have to agree with this sentiment, having just done it on my '07. I have a Penske rear shock and Traxxion forks on another bike (Blackbird), the rear on the FJR feels nearly as good. Now for the forks...

 

[RaYzerman19]

I was wrong on my ES spring rate, it is 2.04. I would say judging by the sag measurements we took last year on an ES, that it would mean 1.02 each.

In my perhaps twisted view, once you increase the preload on the progressive spring, you have primarily compressed the weaker part of the spring. I'd think it would compress first, or at least the most, as the higher rate part has a higher resistance to compressing by definition. On a straight rate spring, the rate doesn't change. With either type, there is more weight required to compress as distance compressed increases, which in effect is increasing resistance to sag.

 

[Fred W]

I was wrong on my ES spring rate, it is 2.04. I would say judging by the sag measurements we took last year on an ES, that it would mean 1.02 each.

Agreed. If it was actually 2.04 each they would feel much stiffer.

In my perhaps twisted view, once you increase the preload on the progressive spring, you have primarily compressed the weaker part of the spring. I'd think it would compress first, or at least the most, as the higher rate part has a higher resistance to compressing by definition. On a straight rate spring, the rate doesn't change. With either type, there is more weight required to compress as distance compressed increases, which in effect is increasing resistance to sag.

This is one of those "physics things" that's a little hard to wrap your intuition around. Let's look at what happens (ignoring the phenomenon of the fork leg lengths changing due to the top-out springs)

Springs have a particular resistance force to compression based on the wire diameter and coil spacing. In the case of the 3rd Gen A model's dual rate springs each spring is .85 kg/mm in the soft part and 1.02 kg/mm in the stiffer part, for a total spring rate of 1.7 kg/mm and 2.04 kg.mm. These forces are measured by applying a weight force on the end of the spring and measuring how much the total spring (not just the soft or hard part) compresses overall and allows the fork leg to move.

When you begin compressing the spring from the fork's fully extended length, you will not only compress the softer coils; the stiffer coils will also compress somewhat, but a much smaller amount than the softer coils do. However, the total resistance of both sets of coils in series felt from the ends of the spring is 0.85 kg/mm. We know that the fork will compress 67.5mm at that .85 kg/mm rate from topped out.

The soft coil part of the spring isn't physically 67.5mm long. Some of that stroke distance is allowed by the stiffer coils compressing in series with the soft coils, and then there is also a nominal amount of spring preload that was applied from the fully extended length of the fork leg. The spring free length is 345mm. The installed length is 322.8mm, so both springs are pre-compressed (preloaded) by a nominal 22.2mm at the .85 kg/mm spring rate. The kinetic force in the pre-compressed springs will be 37.74 kg total for both legs with the forks fully extended and preloaded.

To make the fork legs begin to move at all from fully extended you will have to apply more than 37.74 kg to overcome the preloaded spring force, and from there it will take 1.7 kg to move each additional mm up to the 67.5mm spring rate change.

The curb weight of a 3rd Gen is 290 kg. I measured the axle weights on my own 3rd Gen and the distrubution is 47.6% front / 52.4% rear. So the forks support 47.6% of 290kg = 138 kg.. Subtract the first 37.74 kg of the preload force, the fork springs would compress from the remaining 100.26 kg force, or 59mm.

So the springs were preloaded 22.2 mm and further compressed 59mm by the bike's static weight (sag), the springs inside would be compressed by a total of 81.2 mm to support the bike's weight.

What happens now when you add 10mm of preload?

The total spring preload would increase from the nominal 22.2mm to 32.2mm. The kinetic force of the preloaded springs would be 32.2 x 1.7kg/mm = 54.74 kg. The first 54.74 kg to overcome the preload leaves 138 kg - 54.74 kg preload = 83.26 kg / 1.7 kg/mm means the static sag would now be 48.9mm.

So in our example, adding 10mm preload the sag went from 59mm to 49mm.; the ride height increased by the preload amount. However, the springs inside with the higher preload had 32.2mm of spring preload plus 48.9mm of sag for the (same) total of 81.2 mm of total spring compression due to the bike's weight. The springs will be compressed by the identical amount. therefore it will not feel stiffer due to the increased preload.

The things that will change slightly is the front to rear weight bias from the raised front ride height, and also the angle of the forks from vertical, but those amounts of change will be very small. The bigger change will be how the steering angles affect how the bike will turn in.

I realize that my example numbers appear not accurate, that the sag values are too large. This is because I did not account for the forks being at an inclined angle from vertical, so the bike's weight is not applied directly to the ends of the springs, but reduced by that vector angle. The force applied to the springs is reduced by that angle, but it will compress the forks at the same rate proportionally.

 

[MCRIDER007]

This is one of those "physics things" that's a little hard to wrap your intuition around. Let's look at what happens (ignoring the phenomenon of the fork leg lengths changing due to the top-out springs)
Springs have a particular resistance force to compression based on the wire diameter and coil spacing. In the case of the 3rd Gen A model's dual rate springs each spring is .85 kg/mm in the soft part and 1.02 kg/mm in the stiffer part, for a total spring rate of 1.7 kg/mm and 2.04 kg.mm. These forces are measured by applying a weight force on the end of the spring and measuring how much the total spring (not just the soft or hard part) compresses overall and allows the fork leg to move.

When you begin compressing the spring from the fork's fully extended length, you will not only compress the softer coils; the stiffer coils will also compress somewhat, but a much smaller amount than the softer coils do. However, the total resistance of both sets of coils in series felt from the ends of the spring is 0.85 kg/mm. We know that the fork will compress 67.5mm at that .85 kg/mm rate from topped out.

WOW....that is quite an analysis but I'm not sure it is totally correct. It is my understanding that if the materials and wire diameter are the same throughout the length of the spring then each coil will compress the same amount when weight is applied and the springs overall resistance and spring rate will increase as the tighter spaced coils bind and the number of active coils decreases (if you cut a 1.0 KG spring in half each remaining half will have a spring rate of 2.0 KG). Most of the springs marketed today as "progressive" are actually dual rate springs with about 25 percent of the coils being very tightly wound. When all of the coils are active the effective spring rate is the "lower" rate, however when when the weight of the bike and rider are applied those tightly wound springs quickly bind, becoming inactive coils, and the effective rate of the spring from the remaining active coils is the stated "higher" rate. Its hard to tell where that transition point actually occurs but it seems to me to be much sooner than the FSM states meaning that most riders are using the higher rate almost all of the time....most of the time dual rate springs are a marketing gimmick because the tightly wound coils are always inactive, they just add unsprung weight to the spring. The best example of this is Hyperpro Springs, the bottom coils are so tightly wound that you can completely bind all of them by hand, the only active coils during actual use would be the top coils.

Preload doesn't seem to have any effect on when the transition from the soft to hard rate occurs because of the compression of the top out springs and because preload does not change the springs total compression once static weight is applied.

 

[Fred W]

I don't see where you said anything that contradicts what I said. I think we are saying the same thing in different words. I intentionally left out the fork length issues the top out spring adds because it is not germane to the discussion about what happens to the loaded ride height and main spring rates with varying preloads.

 

[SCB]

Excellent analysis and example Fred and kudos to you for taking the time to write it all out. It appears correct to me as far as it goes but your expected static sag of 59mm (ignoring head angle) is too large and got me thinking. In reality there are 2 'springs' in each fork, the mechanical spring which you considered but also an 'air' spring. There is a certain amount of air trapped in each fork leg. As the fork compresses the trapped air is compressed, effectively acting like a second spring. The effective spring rate for the fork is the sum of the two. This, along with the head angle of the forks as you mention, is the reason why our bikes don't have 59mm of static sag as your calculations would predict. Part of the weight is supported by the air spring.

Taking this a step further, if the air spring were linear like some mechanical springs the only difference in the fork would be a higher effective spring rate. However, the air spring is highly progressive. The result is that it takes much more additional force to compress the fork an additional mm at the bottom of the stroke (compressed) compared to the top (uncompressed) so ALL forks are progressive to some extent, even with those with single rate mechanical springs. Adding progressive mechanical springs does further increase the progressive nature of the fork.


I will note here that increasing the level of oil in the fork should result in a stiffer, and more progressive fork. Maybe a poor man's substitute for stiffer fork springs?

 

[Fred W]

Good point. Yes the air spring makes a definite difference, but you also have to be concerned that you do not raise the oil level too far. Once the air space is gone (fully compressed) you'll blow the oil seals out.

Back in the day, I remember adding schrader valves to the top of some MC fork legs to pressurize the air space for added "spring". I think that was on my Suzuki GT550.