Can anyone give me an idea about how high their stock spacer tubes extend above their forks when the cap is removed on their XZ550?
Haynes just says that there is some pretension. What is "normal" Thanks.
The purpose of the preload tubes is to control 'sag', i.e.: the amount the suspension compresses under load.
https://www.motorcyclistonline.com/suspension-setup-101-part-i-setting-sag
A reasonable goal for laden sag for street use is 30 - 35 mm. If sag is too little, cut the tube a bit, if too much, find a longer tube. ABS pipe works well.
Quote from: pinholenz on April 03, 2018, 06:35:18 AM
Can anyone give me an idea about how high their stock spacer tubes extend above their forks when the cap is removed on their XZ550?
Haynes just says that there is some pretension. What is "normal" Thanks.
It's been a while since I had a set apart but I don't think it's a lot. It's not like the cap should be very difficult to reinstall anyway. Why do you ask? Are you wondering if your springs have relaxed or are you considering aftermarket replacements?
Quote from: John Malcolm on Facebook
https://www.facebook.com/groups/32575026241/? (https://www.facebook.com/groups/32575026241/?)
I have the same setup as you. Forks,aircaps and spacers transferred from an XZ400 donor, but with the original XZ550 springs. I couldn't get the caps on so I shortened the spacers till I just could. However, forks are diving too much so I have just refilled them with ATF instead of 10W fork oil, to 6 inches from the top.
I did wonder what the "normal" pretension was though.....
Over to ROV....
If you can only just get the caps on then that's about your limit using the spacers. Now that you have air caps, you can add a little pressure for firmer springing and better overall stiffness spec is 6psi (0-36psi). (though some on this site will argue against using any pressure)
Thanks George, thats an easy explanation for getting sag about right. Presumably front and rear should be the same. Now that I have my new rear shocker in, I will tweak that along with the front pretension to get it in range.
Rikugun, if you read the quote from POD you will see I have rebuilt my forks and am now suffering from quite a bit of dive in my front end. This is probably oil related but wanted to make sure that I didn't have too much or too little pretension in the OEM progessive spring. (Air caps have a different length to the original caps and I cut down my spacers until I could just reinstall the caps.)
I guess the first stage is to adjust pretension till I get the correct 30-35mm sag all round, then worry about the damping
With the '83 air forks, could one just use air pressure with no spacers to adjust sag?
Quote from: pinholenz on April 04, 2018, 06:02:11 AM
......Rikugun, if you read the quote from POD you will see I have rebuilt my forks and am now suffering from quite a bit of dive in my front end.......
I was unaware you had posted any of that info about a rebuild.
When you rebuilt the forks did you install new springs or use the old sacked out ones. The Race Tech or Progressives are almost a must for these bikes. Race Tech includes thin walled aluminum tubing to use as a spacer while progressive uses low tech pvc pipe. A note of caution on using air. The increase in pressure causes the seal to grip the tube tighter and you end up with more stiction which keeps the slider from moving freely. It really is best to do it with springs.