What a difference some front preload makes

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Why are our fork caps not preload adjustable?
Anyway I always felt my forks were too harsh riding over bumps. Never did anything about it because I'm not to particular. But I checked my sag yesterday roughly by myself with a wire tie. Holy Smokes it was about maybe 60mm as close as I could figure. Between 55 and 60 anyway. Again by yourself makes it a bit difficult.
So just using what I had in the garage I managed to get the caps off (good trick without a 17mm allen socket) and find suitable spacer material (out of a VFR airbox), about 22mm, and go for a test ride. Wow. SO much better. My dumb lazy @zz. jeez.
Anyway if you have not checked your sag, do.
 

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JimGregory said:
Why are our fork caps not preload adjustable?
An air assist kit might be nice. I added one to my GL1000. It really helped the ride. Two taps in the caps connected by a plastic tube. One had an air valve that was filled with a syringe device. A few quick pumps and the front end would raise 1/4 or so and the typical harshness of Honda forks went away. Never had a seal leak with the kit and only had to top it off maybe once a month or three weeks.
 
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I have wonder why all bike do not have the air assist on the front forks. It makes a big difference. I also have a GL1000 with the after market air assist and the air made the old wing a different bike. The system is pretty simple and could be made for almost any bike. Mine has a pressure gauge and a air valve to add or remove air. I run mine between 25 to 30 LBS. Seldom to never needs air added. I wonder why the air never leaked until I had to replace the seals on a backhoe I own. The seals for the backhoe where the same design that where used in the motorcycle. The seals on the backhoe lasted 20 years and lifted more weight and always had dirt being dumped on the tubes.
 
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You should also be able to use adjustable caps from another bike that has the same diameter forks. IIRC the ST13 is 43mm, in which case the preload adjusting caps off say a 2002-2012 VFR800 would be a good match. On my ST11 I have installed the caps off a VFR800 (which I already had in a box under then bench). For spacers, any suitable diameter PVC pressure pipe works very nicely, and is cheap and easy to modify.

A small disadvantage with using air for preload is that it adds to the seal pressure and consequently adds a bit of stiction.
 
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Both my old CB's have air adjust forks. One, that has 2" of extra preload spacers (on top of the stock springs) also runs at the max limit of 14psi in there. The other CB runs zero air assist now,, because I replaced the stock springs with Progressives, and they made such a difference that it does not need air help now. I am going to follow Jim's example of adding a 25mm spacer to preload the stock springs on my ST13. I am also going to thin down the 10w fork oil that it came with,,, as my impression is the front end is under sprung and over damped. The front suspension is not really that bad,,, but it could obviously be better. Cat'
 
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You should also be able to use adjustable caps from another bike that has the same diameter forks. IIRC the ST13 is 43mm, in which case the preload adjusting caps off say a 2002-2012 VFR800 would be a good match. On my ST11 I have installed the caps off a VFR800 (which I already had in a box under then bench). For spacers, any suitable diameter PVC pressure pipe works very nicely, and is cheap and easy to modify.

A small disadvantage with using air for preload is that it adds to the seal pressure and consequently adds a bit of stiction.
I just looked at the parts diagram for a couple of VFR 800's and the fork nut has a screw in adjuster. Did you mean the cap from another bike?
 
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My Magna simply had two Schrader valves- one on each fork. Seven PSI added to the forks made a big difference.
My V45 Sabre has them also, I keep the front air pressure at 14 psi and my rear shock at 57 psi. Both front and rear have the maximum allowed air in them. My seat is 34 years old and the foam is shot. This is how I compensate for a worn out seat.

I have 2 spare shocks that I'm going to take the Schrader valves out and put them on my ST1300 caps.
Thanks for the idea.
 
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I just looked at the parts diagram for a couple of VFR 800's and the fork nut has a screw in adjuster. Did you mean the cap from another bike?
I just checked and the ST13 has a 45mm fork, so the chances of finding a suitable adjustable cap donor are much slimmer (maybe just a CBR600RR), but the VFR800 caps (which use screw-in preload adjusters) are fitted to my 1990 ST1100.
 
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JimGregory
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I just checked and the ST13 has a 45mm fork, so the chances of finding a suitable adjustable cap donor are much slimmer (maybe just a CBR600RR), but the VFR800 caps (which use screw-in preload adjusters) are fitted to my 1990 ST1100.
I would think that if there WERE a bolt up replacement we would have known about it long ago. But maybe not.
 
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Ah yes, suspension tuning....... first place I would spend money on an ST or GL if I had one again. The ST has older technology with damping rods which are simply a set of holes through which the fork oil flows as the suspension moves. A compromise situation. If one went high end, one would put proper cartridges in with adjustable damping. At minimum, one should replace the (undersprung) springs with good aftermarket straight rate springs tailored to your weight for not too many $$. Adding spacers/new spacers to preload the existing is a compromise improvement, but you really need new springs. The more coils and better spring rate are the way to go, then set preload based on spacer length/washers. Without adjustable fork caps, this will be trial and error, but you can get close first time around using the calculations that come with the new spring kit. But, you will get a good bang for the buck just replacing the springs.

Another older tech is the use of Schrader valves to add air, which was also on undersprung forks like my old Magna. It works, nothing wrong with it, compensates for weak springs to some degree....... but your other option is to lower the level of fork oil to have more air, maybe 25mm would be a good start (spring kit should come with a recommended fork oil level). If you have new springs, you probably don't need air valves. Best $150 you can spend.

A better way to go if one wants to spend money, is get a set of proper cartridges, say from Traxxion. You can also play with fork oil weight, lighter to reduce harshness, heavier to increase damping..... but again the existing damping rods are a compromise in this area. If one was to experiment, one could drill additional holes to reduce harsh damping...... why not install a RaceTech gold valve kit for example, which is also tunable.

That's all a good start, but the rear shock needs a lot of help too..... new spring again tailored to your weight, one should attempt to balance front and rear suspensions so they work together. Do both front and rear and you'll think you have a new bike. Especially with an aftermarket shock that has adjustable preload and individual adjustments for compression and rebound damping.
 

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Ah yes, suspension tuning....... first place I would spend money on an ST or GL if I had one again. The ST has older technology with damping rods which are simply a set of holes through which the fork oil flows as the suspension moves. A compromise situation. If one went high end, one would put proper cartridges in with adjustable damping. At minimum, one should replace the (undersprung) springs with good aftermarket straight rate springs tailored to your weight for not too many $$. Adding spacers/new spacers to preload the existing is a compromise improvement, but you really need new springs. The more coils and better spring rate are the way to go, then set preload based on spacer length/washers. Without adjustable fork caps, this will be trial and error, but you can get close first time around using the calculations that come with the new spring kit. But, you will get a good bang for the buck just replacing the springs.

Another older tech is the use of Schrader valves to add air, which was also on undersprung forks like my old Magna. It works, nothing wrong with it, compensates for weak springs to some degree....... but your other option is to lower the level of fork oil to have more air, maybe 25mm would be a good start (spring kit should come with a recommended fork oil level). If you have new springs, you probably don't need air valves. Best $150 you can spend.

A better way to go if one wants to spend money, is get a set of proper cartridges, say from Traxxion. You can also play with fork oil weight, lighter to reduce harshness, heavier to increase damping..... but again the existing damping rods are a compromise in this area. If one was to experiment, one could drill additional holes to reduce harsh damping...... why not install a RaceTech gold valve kit for example, which is also tunable.

That's all a good start, but the rear shock needs a lot of help too..... new spring again tailored to your weight, one should attempt to balance front and rear suspensions so they work together. Do both front and rear and you'll think you have a new bike. Especially with an aftermarket shock that has adjustable preload and individual adjustments for compression and rebound damping.
The ST1300 has cartridge forks, not damping rods.

Replacing the springs may not be necessary based on rider weight. It is popular to start out with "throw away the old springs" but when asked what the sag was with them you get a blank look. The stock spring rate (.897 kg/mm????) is good for riders under 155 lbs if you check spring rate calculators like that one on Race Tech's site. The choice of replacing the OEM progressive springs with straight rate springs is another factor altogether but a good first step if the stock rate is good is to get the sag right with preload.
 
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JimGregory
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The ST1300 has cartridge forks, not damping rods.

Replacing the springs may not be necessary based on rider weight. It is popular to start out with "throw away the old springs" but when asked what the sag was with them you get a blank look. The stock spring rate (.897 in/lb????) is good for riders under 155 lbs if you check spring rate calculators like that one on Race Tech's site. The choice of replacing the OEM progressive springs with straight rate springs is another factor altogether but a good first step if the stock rate is good is to get the sag right with preload.
Once I realized my front sag was way over spec I repaired the problem and now have 38mm measured about 1 minute ago. I have been VERY pleased with the improved comfort, and this morning noticed the greatly improved high speed behavior. I have complained in the past that the bike was too quick steering on the highway and a little flighty, or not so settled in, or however best to describe this fairly common complaint. Well it is much improved by getting the front sag in the right neighborhood to the point where it is not an issue. As I said I am not terribly particular and I think the stock suspension works well for me now that it's set up closer to spec.
I also loved my 2001 VFR suspension that many insisted I spend a fortune to improve.
My ST is not even broken in yet. No need to throw money at it.
 
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35-38 mm of rider sag is a sweet spot reported by other ST riders. Mine was 47 mm at first check and set to 36 mm with 16 mm of preload over stock.

Like Ray said, getting the rear now to help the front will make a difference. For me, fixing the sag and raising the ride height of the forks made the bike steer a little too slow for me. To make that worse I was still on a Michelin tire that aggravated that behavior. Instead of the standard preload setting of 7 - 9 clicks I started using more preload on the rear shock, 12-14 clicks, to raise the rear and get back some of the steering quickness lost. Then I slid the fork legs up 5mm in the clamps so 7-10 clicks of rear preload worked better.
 
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JimGregory
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I am at 10 clicks on the rear. It think it's all just right now for me. I didn't lose any noticeable steering quickness at low speeds and high speeds she is well behaved now.
14 clicks for me would be a little harsh. I am 185lbs.
 
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Just to clarify,, Dduelin,,, my '04s FSM illustrates and labels both the "damping rods" and "damper units". Is this just a case of differing terminology ?? They do refer to spacers as "spring collars". Confusing,,, Cat'

The ST1300 has cartridge forks, not damping rods.

Replacing the springs may not be necessary based on rider weight. It is popular to start out with "throw away the old springs" but when asked what the sag was with them you get a blank look. The stock spring rate (.897 kg/mm????) is good for riders under 155 lbs if you check spring rate calculators like that one on Race Tech's site. The choice of replacing the OEM progressive springs with straight rate springs is another factor altogether but a good first step if the stock rate is good is to get the sag right with preload.
 

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dduelin said:
The stock spring rate (.897 kg/mm????) is good for riders under 155 lbs
I'll never see those days again! I'll have a look at the RaceTech chart to see rates of where I want to be vs where I am. I should check sag. Never have as I'm not picky except to be aware of the harsh front end that I've felt with probably every Honda I've ever had. With new springs and spacers in my VF1000 and V1100S they were much more fun to ride.
 

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Just to clarify,, Dduelin,,, my '04s FSM illustrates and labels both the "damping rods" and "damper units". Is this just a case of differing terminology ?? They do refer to spacers as "spring collars". Confusing,,, Cat'
A damping rod fork uses fixed size holes in a rod or piston to slow or dampen compression and rebound. When the fork compresses and extends oil is forced to travel through the holes. The fixed size of the orifice means that the action is probably a compromise of under damped for soft slow movements and over damped and overly harsh on fast sharp movements or if the action is optimized for one action it is not good for the other.

Collars are the service manual term for spacers. Cartridge is just a term for a damping mechanism (unit) that uses a valve or stack of thin shims or leaves that vary the size of the orifices based on the speed of the compression and rebound. The action can have a wider range of good damping control instead of a fixed amount.

Honda termed their forks and shocks that contain variable damping units Honda Multi Action System. The ST1300 has HMAS forks. They can be improved by aftermarket tuners obviously but in stock form are tunable with changes in preload, oil viscosity, and oil level.

Suspension tuning is art and science and needs of the individual can call for total replacement, gentle massage, or nothing at all.
 
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JimGregory
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I'll never see those days again! I'll have a look at the RaceTech chart to see rates of where I want to be vs where I am. I should check sag. Never have as I'm not picky except to be aware of the harsh front end that I've felt with probably every Honda I've ever had. With new springs and spacers in my VF1000 and V1100S they were much more fun to ride.
As I said in the first post. If you have not checked the sag, do. My 07 is now a much more pleasant and safer bike for it.
My harsh front end was why I didn't check it. What was happening though, was much of my travel was used up on (VERY) excessive sag and the forks were bottoming instead of doing their job.
ADDING preload has softened my ride. Chew on that a bit.
 
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dduellin is correct in his detail. Jim, what you call harsh is actually an undersprung "mushy" suspension that travelled too much and bottomed out. You firmed it up with your spacer adjustment and it is better no doubt. I think harsh is more accurately described as too much preload or excessive (harder) damping. All good, you're on the right track.
 
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JimGregory
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dduellin is correct in his detail. Jim, what you call harsh is actually an undersprung "mushy" suspension that travelled too much and bottomed out. You firmed it up with your spacer adjustment and it is better no doubt. I think harsh is more accurately described as too much preload or excessive (harder) damping. All good, you're on the right track.
Ray I think I figured that out on my own, but Dave preceded me by a few years no doubt.
I say it's harsh when it hurts to hit bumps. But things that hurt now in my 60's were called "fun" not many years ago!
 
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