Fork spring preload?

rwthomas1

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Joined
Jun 6, 2020
Messages
1,159
Location
Rhode Island, USA
Bike
'01 ST1100 non-ABS
Hello All,
ST1100's have a reputation for being softly sprung. Under hard braking, downhill on off-ramps, over bumps, I believe the forks are bottoming out. It's not a regular occurrence, but being 250lbs, and having 48K on the odo I'm sure isn't helping.

Is there a simple way to increase spring preload? In my old bike days it was a simple thing to add a PVC pipe spacer. I believe that will work on the left side fork, but not the cartridge side? I've looked at the manual, but it isn't entirely clear if it can be done easily. I used to do this with the forks installed, pop each cap off, install the spacers and go ride. I'm guessing it's not that simple, and cannot be done with the forks installed?

Understand I'm planning to go through the forks and rest of suspension this winter. New springs, etc. So this is just a temporary fix to get through the season.....

Thanks, RT
 
The 1300 is set up for your average 170 lb rider - and i think that's with ATGATT, so a 150-160 lb rider in his birthday clothes. Since the 1300 does not offer a quick and easy way to add preload (pull the caps, unscrew them from the damper rod, etc....) I don't think you will have a quick and easy way to change preload on your 1100. But I'm sure more knowledgeable guys will chime in soon.
 
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yes, I think you understand it fairly well, left side is an easy cap removal and insert longer spacer. Right fork requires disassembly to install a longer spacer. But, the simple solution is to leave the right side as is, and put twice as much length extension in the left side, which gives the same result and is much easier to experiment with to get the ride height you're happy with. If that doesn't solve the problem you may be better off going to heavier weight springs, adding preload adjusts the ride height, but can't do everything.
 
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Roger. said:
Adding tube spacers will only adjust ride height - with the danger that your springs become coil-bound before all your fork travel is used up. The answer, as you said, is heavier duty springs.
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With the stock spacers installed and the fork fully compressed, how close to being coil bound is the spring? Has anybody ever been able to coil bind the spring after putting in longer preload spacers? Would be interesting to know just how much you can add to the spacer before coil binding could become an issue.

Also, if the fork travel is already bottoming out, as in the case of the OP, is there any practical difference between bottoming out the fork travel or coil binding the spring, seems like they'd be pretty similar.
 
Well, after looking around a bit, it seems Progressive springs are the easy way to go. A little bit stiffer and the price is right. RaceTech, Traxxion, etc. all seem great. But more money than I wish to spend at the time. I am satisfied with the handling other than the softly sprung forks. From what I can determine, I could swap in the Progressive springs without taking the forks off the bike. That's a big deal, minimizes downtime, etc. I understand there are tools that can be borrowed? Who do I talk to?

RT
 
rwthomas1 said:
Well, after looking around a bit, it seems Progressive springs are the easy way to go. A little bit stiffer and the price is right. RaceTech, Traxxion, etc. all seem great. But more money than I wish to spend at the time. I am satisfied with the handling other than the softly sprung forks. From what I can determine, I could swap in the Progressive springs without taking the forks off the bike. That's a big deal, minimizes downtime, etc. I understand there are tools that can be borrowed? Who do I talk to?

RT
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I currently have the Fork R&R loaner kit. @John OoSTerhuis is the keeper of this kit. PM him and he'll give me the OK to ship it to you.
 
rwthomas1 said:
From what I can determine, I could swap in the Progressive springs without taking the forks off the bike.
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I've always taken the forks off the bike to do anything to the right fork, but also never borrowed the fork R&R kit. Is it possible to swap springs on the right fork with the fork still on the bike using tools in the kit? FWIW, taking the forks off the bike isn't a lot of work.
 
dwalby said:
I've always taken the forks off the bike to do anything to the right fork, but also never borrowed the fork R&R kit. Is it possible to swap springs on the right fork with the fork still on the bike using tools in the kit? FWIW, taking the forks off the bike isn't a lot of work.
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According to STriders.net, yes it appears to be a pretty simple procedure. Having a third hand for the cartridge side apparently helps, but it looks entirely possible. I know its not a huge deal to pull the forks, but it will save considerable time to do it on the bike. My only confusion is the fork oil level, but I only have access to the online manual. The hardcopy I have at home will likely have more clear guidance on that.

RT
 
John OoSTerhuis said:
Just checking in long enough to say we are without power. Three days and running. Will check back in when able.

John
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John, is that from the storm on Sunday? I rode through the east side of Iowa on Sunday coming back from MNSTOC. I saw some pretty good wind and rain, but missed the big stuff.

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Still without power, since 1:50 Monday. Maybe tomorrow. Yes, we experienced a derecho. Terrible damage throughout Iowa and Illinois. Straight line winds in excess of 100 mph. Thought our old big maple (4’ diameter) might end up on the roof. Lots of folks suffering. Major crop damage. Your corn flakes (and ethanol gas) will be a bit more expensive soon.

John
 
rwthomas1 said:
Well, after looking around a bit, it seems Progressive springs are the easy way to go. A little bit stiffer and the price is right. RaceTech, Traxxion, etc. all seem great. But more money than I wish to spend at the time. I am satisfied with the handling other than the softly sprung forks. From what I can determine, I could swap in the Progressive springs without taking the forks off the bike. That's a big deal, minimizes downtime, etc. I understand there are tools that can be borrowed? Who do I talk to?

RT
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No info for the tools, but FYI, I put the progressive springs in mine and found the ride harsher afterwards, the stock fork oil is only 5 weight and I found that the damping was inadequate. I switched to a 10 weight on the cartridge side and found it much better. Your mileage may vary. hope it helps.

Nice thing about the ST is it has a fork oil drain plug, so you don’t have to pull the fork to change the oil. As long as the fork cap is off, and you put back the same volume you took out. I use the old ladys Pyrex measuring cup. (I just wash it and put it back), what she dont know wont kill me.
 
John OoSTerhuis said:
Still without power, since 1:50 Monday. Maybe tomorrow. Yes, we experienced a derecho. Terrible damage throughout Iowa and Illinois. Straight line winds in excess of 100 mph. Thought our old big maple (4’ diameter) might end up on the roof. Lots of folks suffering. Major crop damage. Your corn flakes (and ethanol gas) will be a bit more expensive soon.

John
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I’ve seen pics from your area John, you’re definitely in our thoughts and prayers. Terrible storms out there. We are farmers over here, we really feel for crops being down.
 
rwthomas1 said:
I'm guessing it's not that simple, and cannot be done with the forks installed?
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One can change fork oil and replace coils while having the front end installed on the bike.

Bike on mainstand, place jack underneath oil pan, lifting point underneath the drain bolt (the most rigid edge there), jack up till front wheel still contacts the ground (you'll apply down-pressure on the fork-springs later), throw a towel or old blanked over false tank and fairing parts, remove handlebar covers, remove bar clamps, swivel handlebar backward and place on false tank (hence the rag there), open upper triple clamp bolts first, then attempt to unscrew fork caps (swivel steering to the limiter as support, while pushing against the bike with your thigh/hips to prevent dropping it)
One cap comes off, the other is still attached to the damper rod (use 2 box-wrenchs to detach cap from rod)
Once the caps are off no internal pressure, so then one can drain the fork oil through the 2 bolts on each leg's sides (non-ABS ST1100 only)
With the oil out, less spill while pulling coils out (still need to wrap them in old towels in the process)

I'd measure the length of the uncompressed coils and compare with the numbers in the shop manual, possible their just worn and saggy...
When changing to progressive ones, I'd consider installing a rear shock with similar spring rate while at it.

With the drain bolts still removed one can also rinse the forks a bit, petrol, brake cleaner, etc... (just as dirty, quick service) give it time to vent afterwards though

John's advise of checking the anti-dive is also sound; see if bracket & piston move freely, accumulated debris might have seized up the parts

Trying stiffer fork oil might also be worth a test; I wouldn't go higher as 10W (using a 7W with Hyperpro springs myself)
If you refill by oil volume (as by the shop manual) or fluid height, or measuring remaining top air volume is food for philosophical debates... ;)
I'm very happy with my measuring cup though...

You might need to build yourself a tool/hook (stiff welding- or cloth hanger-wire) to lift/hold the damper-rod while slipping that C-clip on again; some folks even suspend the rod from the ceiling with tie-downs or a rope to have both hands free, or maybe a second person lending a hand.
Other tools might be a threaded rod with a coupling nut screwed on, maybe even with a spade-handle on top.... anything to hold the damper rod up while depressing the coil with that C-clip to slide it under the head...

Check torque values on all and everything, don't forget to tighten the upper triple after the caps are screwed in...
 
I think I'm gonna go with the Sonic Springs, 1.00kg/mm. A wee but softer than the recommended 1.02-1.05, but considering the stock spring is 0.6kg/mm, the difference should be huge. RT
 
I ended up with 0.9kg/mm springs in my 1100 and was very happy with them; they were surplus from my VFR800, and even though they are technically lighter than ideal for the heavier ST, I think the much longer fork travel of the 1100 (150mm vs 120mm for the 800) makes up for that. I weigh about 85kg and don't do any two-up.
 
TerryS said:
I ended up with 0.9kg/mm springs in my 1100 and was very happy with them; they were surplus from my VFR800, and even though they are technically lighter than ideal for the heavier ST, I think the much longer fork travel of the 1100 (150mm vs 120mm for the 800) makes up for that. I weigh about 85kg and don't do any two-up.
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Seems 1.00 should be perfect for me then. I'm 250lbs, or @113kg? Thanks, RT
 
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