Hi all. just replaced my ft fork seals and they bottom out now when hitting larger bumps or pulling into driveway . My manual has 10w 30 as the got oil could this be wrong and causing the problem?
sounds like your oil level is low .
did you measure it?
quick check is 120mm from top with springs out and forks compressed.
Quote from: Mark Olson on July 17, 2011, 08:37:34 PM
sounds like your oil level is low .
did you measure it?
quick check is 120mm from top with springs out and forks compressed.
I did measure it , manual called for 15.08 oz . I will check the level, thanks for the input
If you're bottoming out, then you've got a spring problem.
The spring is what holds the bike up. The fork oil only controls the VELOCITY of the fork movement. It has no effect on the position of the fork.
Bottoming out is a spring problem (i.e. weak spring or not enough preload).
DavidR.
Quote from: SlowOldGuy on July 17, 2011, 11:10:18 PM
If you're bottoming out, then you've got a spring problem.
The spring is what holds the bike up. The fork oil only controls the VELOCITY of the fork movement. It has no effect on the position of the fork.
Bottoming out is a spring problem (i.e. weak spring or not enough preload).
DavidR.
What about the "air spring" effect of a higher oil level creating resistance to bottoming?
Before I did the seals and fixed a dampner rod on my 85 it would bottom out after I did them there great.So springs must hold the bike up but the oil must stop the amount of travel when you brake so the oil is holding the front end up when braking IMO.
Quote from: Flying Scotsman on July 18, 2011, 12:00:10 AM
Before I did the seals and fixed a dampner rod on my 85 it would bottom out after I did them there great.So springs must hold the bike up but the oil must stop the amount of travel when you brake so the oil is holding the front end up when braking IMO.
Nope.... all the oil does is damp oscillations and control the speed of the suspension movement. There is an "air spring" effect that is determined by the oil level, and that will help reduce fork "dive", but the springs "rate" is what sets ride height and bottoming resistance. The OEM springs are fairly soft, too soft for most normal-sized riders.
guys , the original post was he changed his seals and now it bottoms out.
so either he did not set the preload correctly or the oil level is to low. Also he is using motor oil .
Had the same problem with my 1990 FJ. At any rate it "clunked" or banged pretty hard going over a curb. The bike was new to me and it was just another part of trimming it out. I drained the oil and it had 8 oz plus or minus a bit in each leg. Manual spec's 10w fork oil or 30 w motor oil, or 10-30 weight motor oil (equals about 15 W?).
I'm not a small guy so I used 10-30 motor oil and set the preload up to max setting. Installed 14 ounces of oil in each leg. Works great now. No problems. Think I will now take 1 setting off the preload and do a test run next. The fork seals seem to be holding good with no leaks, when I found only 8 oz in each my thought was probably bad fork seals but no problem there. Oh, after the oil and preload change I did a sag check. It came out good. My front springs were the stock progressive type.
I set the rear up to max preload for the time being. I am still playing with the settings. Seems to understeer a bit but that hasn't got anything to do with the fork oil, preload etc.. Have a good day :)
Quote from: Mark Olson on July 18, 2011, 01:06:47 PM
guys , the original post was he changed his seals and now it bottoms out.
so either he did not set the preload correctly or the oil level is to low. Also he is using motor oil .
Is using motor oil not good ? I had a friend who worked at a bike shop do the job for me he said the adjusters were frozen so he would have to keep it at the same setting but something has changed I can hold the front brake and with a little effort I can bottom out the frt end couldn't do that before and there was only about 4 to 5 oz of oil in each fork when we originally drained them. my first thought was wrong oil. Thanks I appreciate your input
It's not the oil ( so long as you put enough in)
If you have 86 forks with anti dive they should be the same as my 1985 I use 10W30 in them.My 90 has later shocks and 10W30 isnt spec I think it was 15W fork oil.My horn used to hit the fender brace but the forks were just about empty.There good now.
What year is your FJ ?
I would take them apart and do it again something seems wrong or try more oil first so theres less air in there.
Mr Baker makes sense with the "air spring" effect"
I have a lot to learn about suspensions.
The easiest way is to change the oil. You have to use fork oil 10W (originally), or heavier (if you are quite large sized :)). You will see the difference at once. Or may be not... ;)
Did you mount the legs properly? I mean, there is small part at the bottom of tube outer - SPINDLE, TAPER.
If its in wrong position only springs works. Like you would have no oil. Its worth to check.
Quote from: Travis398 on July 18, 2011, 05:34:19 PM
It's not the oil ( so long as you put enough in)
+1
Quote from: Mark Olson on July 17, 2011, 08:37:34 PM
sounds like your oil level is low .
did you measure it?
quick check is 120mm from top with springs out and forks compressed.
+1
Quote from: JFox on July 18, 2011, 05:54:24 PM
Did you mount the legs properly? I mean, there is small part at the bottom of tube outer - SPINDLE, TAPER.
If its in wrong position only springs works. Like you would have no oil. Its worth to check.
We may have a winner....
I'd go in that order. At least you'd verify what is is what should be. Let us know how it goes, and good luck.
I stand corrected. I put 15 oz oil instead of 14. And that was 120-130mm measured from the top, no spring, fully collapsed. Check your oil level first. Rest to , ride tomorrow :good:
Maybe the damper rods were not installed correctly (by the PO) and that was keeping the forks from bottoming out.
If you think oil holds the bike up, then take out the spring and see what happens. :-)
The tapered spindle will give you a hydraulic cushion at the bottom of travel, but that's not holding the bike up.
DavidR.
Quote from: SlowOldGuy on July 18, 2011, 08:14:09 PM
Maybe the damper rods were not installed correctly (by the PO) and that was keeping the forks from bottoming out.
If you think oil holds the bike up, then take out the spring and see what happens. :-)
The tapered spindle will give you a hydraulic cushion at the bottom of travel, but that's not holding the bike up.
DavidR.
I'm a Newby here so don't punish me if my answer is not to your liking. The dampener rods can be a real pain if not aligned correctly with the hole below and the forks just lock when pushed down, obviously if the forks have some bounce then this is not the problem.
The other issue is the thickness of oil 15-30W (engine oil?) combined with max setting which would cause a hydraulic lock with sudden movement. My forks run 12W fork oil is the hotter Western Australia climate with progressive springs (with spacers) and midway dampening.
Currently my bets are with the dampener rods.
Quote from: SlowOldGuy on July 18, 2011, 08:14:09 PM
Maybe the damper rods were not installed correctly (by the PO) and that was keeping the forks from bottoming out.
If you think oil holds the bike up, then take out the spring and see what happens. :-)
The tapered spindle will give you a hydraulic cushion at the bottom of travel, but that's not holding the bike up.
DavidR.
If you think the springs stop the forks from bottoming out ,take all the oil out and see what happens.
we all know springs hold the bike up , but the oil is what controls the travel of the forks up and down.
if the oil level is low you will bottom out even with brand new race tech springs going over speed bumps and curbs and such.
that is why the level of oil and weight is so important.
different for each rider. the 120-130 mm is a starting point to be fine tuned to your riding style.
if you overfill the forks then they are stiff as hell and hydro-lock.
Sag is controlled by spring rate. The rate at which you use the travel is set by the oil (or lack thereof). Oil can prevent bottoming because of the intertia of the front end travelling down, it slows the travel and prevents it from overshooting the balance point (set by the spring and preload). There's a big difference between sitting on a stand in the garage and measuring where the forks are (oil does nearly nothing in that situation, unless you're way overfull) and seeing how the suspension moves in a dynamic environment.
A professional rider can likely tell the difference easily, but most people that I've talked to notice the effect of damping to a much greater degree. Absolutely full forks (no air gap) will not be hydrolocked for long, as the seals will give out almost immediately!
Without looking it up (being lazy) I want to say stock oil spec'd is 10w for the FJ. If the oil is more than a few years old, almost anything will be an improvement, as forks do ugly things to the fluid you put in them in short order. Springs also wear, but at a much slower rate.
And yes, the damper rods are a right bastard to get installed properly.