Gen III front sag - advice please.

[mcatrophy]

I've never been fully happy with my 2014 FJR1300AS that has the "ES" suspension. Whilst it's always given me the utmost confidence in riding, it's been relatively uncomfortable.

I've improved this somewhat by reducing the front tyre pressure form "my" 40-odd psi to nearer the Yamaha recommendation of 36 psi. Posted about this here.

My gut feel is that my suspension is too stiff. In order to get some sort of handle on this, I've done some sag measurements. While I am aware of some of the terms used ("static", "dynamic"), I've seen different definitions of these, so I'm not using them, instead I'm being purely descriptive.

I weigh about 145 without gear. I use the bike for shopping, playing in country lanes, touring consisting of slab right through to mountainous regions.

All the measurements were made as I usually have the suspension, rider only, hard + 0.

1) Front off the ground (blocks under the headers), length of the exposed fork tube with no weight on the front wheel: 135mm.

2) Bike on centre-stand, so some weight on the front wheel, no rider: 133mm -> 2mm sag (probably a useless measurement)

3) Bike on side-stand, no rider, so a bit more weight on the front wheel, steering straight: 110mm -> 25mm sag (probably a useless measurement)

Using a plastic wire-tie round the fork tube, pushed up against the seal, then gently pulled the bike upright. Lowered it back onto the side-stand.

4) Length measured to top of wire-tie, bike's weight, no rider: 102mm -> 33mm sag ("Static" sag?)

5) Gently got on the bike, balanced as best as I could, then gently off the bike, so after rider sat on bike: 97mm -> 38mm sag ("Dynamic" sag"?)

6) Finally I stood beside the bike, front brake on, pumped down as hard as my limited weight and advancing years let me, length measured after pumping: 53mm -> 82mm sag(?).

In summary, probably the most useful measurements:

Front sag with bike only: 33mm

Front sag with rider: 38mm

So, are these reasonable numbers?

I took a few pictures to show what I was doing. Typical measurement method:

(Click on image for larger view)



They all can be viewed here.

 

[rogdeb]

Don't know enough to give advice, but I'm sure someone will be along soon as I really want to read about it.

 

[Fred W]

There is really only one meaningful measurements here.

# 5 minus #1 - Fork movement when fully loaded with rider and gear (Dynamic Sag).

You want this sag number to be approximately 1/3rd of the total suspension travel. The 2014 ES front fork total travel is 135mm. That means the ideal dynamic sag value would be ~45mm. At 38mm you aren't all that far from the ideal.

There are two ways to alter the dynamic sag. One is to change the spring preload, the other is to alter the spring rate. Changing the preload will change the ride height, and therefore the steering angles and fore/aft weighting a little. But it will not actually soften the spring and provide more compliance. For that you would need to go with a softer spring.

I've got to ask though, have you tried any damping besides "Hard"? I weigh a good bit more than you and am finding I like "Normal 0" most of the time and switching to Soft -3 on the really beat up roads. It is unfortunate that they tied the compression and rebound damping adjusters together. It sure would have been nice to be able to set them independently.

 

[mcatrophy]

There is really only one meaningful measurements here.
# 5 minus #1 - Fork movement when fully loaded with rider and gear (Dynamic Sag).

You want this sag number to be approximately 1/3rd of the total suspension travel. The 2014 ES front fork total travel is 135mm. That means the ideal dynamic sag value would be ~45mm. At 38mm you aren't all that far from the ideal.

There are two ways to alter the dynamic sag. One is to change the spring preload, the other is to alter the spring rate. Changing the preload will change the ride height, and therefore the steering angles and fore/aft weighting a little. But it will not actually soften the spring and provide more compliance. For that you would need to go with a softer spring.

I've got to ask though, have you tried any damping besides "Hard"? I weigh a good bit more than you and am finding I like "Normal 0" most of the time and switching to Soft -3 on the really beat up roads. It is unfortunate that they tied the compression and rebound damping adjusters together. It sure would have been nice to be able to set them independently.

Thanks for reply. Yes, I've tried the three settings, but not moved from "0" on any of them.

Except on a very smooth road, "soft" I find very bouncy, almost sickenly so. On a good motorway, it is the most comfortable, occasional minor irregularities like white paint or joins between different surfaces, bridge expansion joints and the like are absorbed quite well, "standard" lengthens the time these are felt, "hard" makes them more intrusive.

Around town, "standard" is ok unitl I hit a pot-hole or other nasty road irregularity, the bike tends to jiggle afterwards. "Hard" is the best all-round, but doesn't give a relaxed ride.

Hit any sort of irregularity when leant over, "hard" is definitely the best option. Also, "hard" seems to give the best balance between front and rear. With "standard" or "soft" on irregular surfaces, the two ends seem to want to move independantly. I find this difficult to describe, it's as if each wants to deal with the irregularity in its own way without matching the other end.

It's not all bad. The bike gives me huge confidence. There's a corner near home I do most times I go out. On my Gen II, 40 was the maximum speed I felt comfortable with. The second time I went round it with my '14, it was doing 45 and asking for more. So, no complaints there, it's just that a lot of the time it feels a bit like a row-boat with perfect steering shooting through rapids.

I'm getting the feeling that I'm just going to have to get used to it. Pity that I find it so much less comfortable than my Gen II.

Indecently Incidentally, i had occasion to take a pillion passenger over some varied roads, a little over 100 miles. I wasn't pushing the bike's capabilities at all, but it did feel very much better (set for rider and passenger).

Any further comments welcome.

 

[Fred W]

Indecently, i had occasion to take a pillion passenger over some varied roads, a little over 100 miles. I wasn't pushing the bike's capabilities at all, but it did feel very much better (set for rider and passenger).

Assuming you transposed a couple of letters there, and that you weren't riding two up with no clothes on...

I have noticed the same phenomenon, both on the new ES and also on my old '05. With the added weight of my 100 lb passenger, the bike just seems more "planted" and (surprisingly) I am able to ride faster and smoother with her on the back than without.

Of course without her I am able to stretch the envelopes more when cornering (without a whack to the noggin) but it just isn't quite as smooth.

 

[mcatrophy]

Indecently, ....

Assuming you transposed a couple of letters there, and that you weren't riding two up with no clothes on... :uhoh:

I have noticed the same phenomenon, both on the new ES and also on my old '05. With the added weight of my 100 lb passenger, the bike just seems more "planted" and (surprisingly) I am able to ride faster and smoother with her on the back than without.

Of course without her I am able to stretch the envelopes more when cornering (without a whack to the noggin) but it just isn't quite as smooth.

Whoops, spell checker strikes again! I assure you we were both ATGATT. Please read "incidentally" not "indecently".

It's a pity my Better Half doesn't ride with me. But She would also complain about my driving, so probably just as well.

Having said all that, it is really pleasurable when attacking interesting roads where comfort is of secondary importance, both its suspension and throttle control are significantly better than my previous bike.

 

[Pterodactyl]

I weigh about 145 without gear.

There's your problem. FJRs are made with American's in mind. Get that up to 145 kilos and it'll smooth right out.

 

[mcatrophy]

I weigh about 145 without gear.

There's your problem. FJRs are made with Americans in mind. Get that up to 145 kilos and it'll smooth right out.

Well, I suppose that's one possible solution. At the moment, though, I'm pretty healthy for my age, I have none of the issues that often afflict the obese more generously built

.

I could possibly tie a sack of cement onto the pillion seat. Probably better than wearing one round my waist

.

 

[rwortman]

There is really only one meaningful measurements here.
# 5 minus #1 - Fork movement when fully loaded with rider and gear (Dynamic Sag).

You want this sag number to be approximately 1/3rd of the total suspension travel. The 2014 ES front fork total travel is 135mm. That means the ideal dynamic sag value would be ~45mm. At 38mm you aren't all that far from the ideal.

There are two ways to alter the dynamic sag. One is to change the spring preload, the other is to alter the spring rate. Changing the preload will change the ride height, and therefore the steering angles and fore/aft weighting a little. But it will not actually soften the spring and provide more compliance. For that you would need to go with a softer spring.

I've got to ask though, have you tried any damping besides "Hard"? I weigh a good bit more than you and am finding I like "Normal 0" most of the time and switching to Soft -3 on the really beat up roads. It is unfortunate that they tied the compression and rebound damping adjusters together. It sure would have been nice to be able to set them independently.

That is true if you are only talking about tweaking the existing hardware. The difference between bike only sag and bike with rider sag will tell you if you have the right spring rate.

 

[Fred W]

That is true if you are only talking about tweaking the existing hardware. The difference between bike only sag and bike with rider sag will tell you if you have the right spring rate.

I have heard that statement before, but I fail to see how those measurements will provide that. I mean, it's not like the bike will ever be ridden without the rider, so why not just consider the total weight of bike and rider?

As I said earlier, you can get the right ride height either by changing springs or varying the preload.

Varying the preload will allow you to hit the desired ride height but will not change the spring's rate (assuming a straight weight spring). So, for a given amplitude bump in the road the suspension will still deflect the same amount regardless of the preload.

Varying the spring rate will allow you to use more or less preload to hit optimum ride height, but more importantly, it will change how compliant the fork is to bumps (how far it will deflect for a given size bump).

So, the way I see it, you would select the spring rate depending on how compliant you want the suspension to be: How much you are willing to have the fork deflect over the expected terrain and load. And then set the ride height with the preload adjusters to keep the fork centered in its operating range.

How compliant you want it is a compromise of comfort over rough terrain vs steering angle stability through corners. The two extreme cases would be a road race bike, where you want the maximum stability of steering and the road will always be smooth, vs an off road machine where maximum suspension compliance is desired, and steering is often done with rear wheel slide.

 

[rwortman]

Lets demonstrate by using extremes. Let's say you have a 400 lb rider. He sits on the bike and you adjust the sag at both ends to be 1/3 of the travel. He gets off the bike and both ends are bang up against the top stops. This means you have had to add too much preload to the spring because it is too soft for the bike/rider combination. Now the opposite, a featherweight rider sits on the bike and you once again adjust the sag for the 1/3 travel. He gets off and the bike only moves up 1/2 inch. This is because the spring is way too stiff for that bike/rider combination. This is why there is both a bike only, and bike with rider sag spec. If you can't achieve both, the spring is wrong. On a 650lb bike the rider isn't as much of the total weight so there is a wider range of rider weight covered by the same spring. on a sub 400lb sport bike or sub 300lb dirt bike the rider is a big percentage of the total weight and these checks can get you pretty close to the ideal spring. It's not that the bike will be ridden without a rider, it is that this is a tool for determining proper spring rate.

 

[MCRIDER007]

Lets demonstrate by using extremes. Let's say you have a 400 lb rider. He sits on the bike and you adjust the sag at both ends to be 1/3 of the travel. He gets off the bike and both ends are bang up against the top stops. This means you have had to add too much preload to the spring because it is too soft for the bike/rider combination. Now the opposite, a featherweight rider sits on the bike and you once again adjust the sag for the 1/3 travel. He gets off and the bike only moves up 1/2 inch. This is because the spring is way too stiff for that bike/rider combination. This is why there is both a bike only, and bike with rider sag spec. If you can't achieve both, the spring is wrong. On a 650lb bike the rider isn't as much of the total weight so there is a wider range of rider weight covered by the same spring. on a sub 400lb sport bike or sub 300lb dirt bike the rider is a big percentage of the total weight and these checks can get you pretty close to the ideal spring. It's not that the bike will be ridden without a rider, it is that this is a tool for determining proper spring rate.

Peter Verdone has some comments on his website supporting what you are explaining....that for any given rider on any given bike there is one one ideal spring rate. However, the ideal ratio between the two sags is going to be dependent on the ratio between the weights that the forks are supporting in both measurements (my opinion) and those ratios are not published because they will vary for each rider. Another way to estimate ideal spring rate is to pick the lightest spring that will give the correct sag but not bottom under heavy braking...which could take a lot of testing to find that spring.

Back to the OP's question, he obviously has too heavy of fork springs for his weight (or too much compression damping) when riding solo and the ES's linked damping system is preventing him from finding a solution to getting the front and back to work in harmony. Damping complements spring rate but if the spring rate is wrong and you can't separate compression and rebound damping then one or the other is always going to be less than ideal. If he was satisfied with the forks' performance on his GEN2 then GEN2 springs in the ES may be a solution....and may require some spacer adjustments to get the sag right but should work fine otherwise

Another thing he could do if he wanted to play with the forks before changing springs would be to put the preload on solo, go to the soft damping position, disconnect the fork compression damping wire (I think that is on the left side), put the rest of the system on STD or Hard and see how the forks respond (will probably get an error message on the dash). If that is an improvement then it may to possible to soften the forks compression damping by raising the height of the stepper motors.

 

[mcatrophy]

Lets demonstrate by using extremes. Let's say you have a 400 lb rider. He sits on the bike and you adjust the sag at both ends to be 1/3 of the travel. He gets off the bike and both ends are bang up against the top stops. This means you have had to add too much preload to the spring because it is too soft for the bike/rider combination. Now the opposite, a featherweight rider sits on the bike and you once again adjust the sag for the 1/3 travel. He gets off and the bike only moves up 1/2 inch. This is because the spring is way too stiff for that bike/rider combination. This is why there is both a bike only, and bike with rider sag spec. If you can't achieve both, the spring is wrong. On a 650lb bike the rider isn't as much of the total weight so there is a wider range of rider weight covered by the same spring. on a sub 400lb sport bike or sub 300lb dirt bike the rider is a big percentage of the total weight and these checks can get you pretty close to the ideal spring. It's not that the bike will be ridden without a rider, it is that this is a tool for determining proper spring rate.

Peter Verdone has some comments on his website supporting what you are explaining....that for any given rider on any given bike there is one one ideal spring rate. However, the ideal ratio between the two sags is going to be dependent on the ratio between the weights that the forks are supporting in both measurements (my opinion) and those ratios are not published because they will vary for each rider. Another way to estimate ideal spring rate is to pick the lightest spring that will give the correct sag but not bottom under heavy braking...which could take a lot of testing to find that spring.

Back to the OP's question, he obviously has too heavy of fork springs for his weight (or too much compression damping) when riding solo and the ES's linked damping system is preventing him from finding a solution to getting the front and back to work in harmony. Damping complements spring rate but if the spring rate is wrong and you can't separate compression and rebound damping then one or the other is always going to be less than ideal. If he was satisfied with the forks' performance on his GEN2 then GEN2 springs in the ES may be a solution....and may require some spacer adjustments to get the sag right but should work fine otherwise

Another thing he could do if he wanted to play with the forks before changing springs would be to put the preload on solo, go to the soft damping position, disconnect the fork compression damping wire (I think that is on the left side), put the rest of the system on STD or Hard and see how the forks respond (will probably get an error message on the dash). If that is an improvement then it may to possible to soften the forks compression damping by raising the height of the stepper motors.

Useful comments, thanks.

At the moment I don't want to do any significant changes, there might be warranty issues, and it currently plays so nicely in the twisties.

I'm learning to put more weight on my feet before the lumpy-bumpy bits, this avoids some of the discomfort. I'll have to find a local suspension guru, see what might be possible.

Biggest issue will be from SWHTPS. "You've* spent £8000 changing your bike for one you said would be much better, and now you want to spend more?"

* Actually, she spent the money, but that's not how it will come across

.

 

[RaYzerman19]

The problem with the ES is the fork spring preload is not adjustable, and the spring rate is 1.0. This is too stiff for a 145 lb. rider, which you can verify on Sonic or RaceTech's site. Trying to compensate with lighter damping will just end up riding with inadequate damping...... I'd change the springs in the forks, shouldn't cause any warranty issue at all.

 

[Fred W]

I'm inclined to agree with Ray, above. Most of us don't have that "problem" because we weigh in at a whole lot more than our diminutive friend from Derby. I actually had 1.0 kg/mm springs installed on my '05, which is probably why the front of the ES feels just fine to me.

Now it's just a matter of finding some replacement springs for the ES. The specs for the stock springs are:

273.8mm (10.78") free length, 1.02 kg/mm constant spring rate, 10mm of preload. So your current preload force is 10.2 kg per side. You will have to adjust the spacer length (with washers, etc.) to get the same amount of preload force from the softer spring if you want to keep the stock ride height.

 

[mcatrophy]

The problem with the ES is the fork spring preload is not adjustable, and the spring rate is 1.0. This is too stiff for a 145 lb. rider, which you can verify on Sonic or RaceTech's site. Trying to compensate with lighter damping will just end up riding with inadequate damping...... I'd change the springs in the forks, shouldn't cause any warranty issue at all.

That agrees with what I've felt.

I'm inclined to agree with Ray, above. Most of us don't have that "problem" because we weigh in at a whole lot more than our diminutive friend from Derby. I actually had 1.0 kg/mm springs installed on my '05, which is probably why the front of the ES feels just fine to me.
Now it's just a matter of finding some replacement springs for the ES. The specs for the stock springs are:

273.8mm (10.78") free length, 1.02 kg/mm constant spring rate, 10mm of preload. So your current preload force is 10.2 kg per side. You will have to adjust the spacer length (with washers, etc.) to get the same amount of preload force from the softer spring if you want to keep the stock ride height.

Thanks for the spring info, Fred. I shall see if I can find somewhere that could do this, but as I said above, not sure I want to upset the Important Person

.