What is wearing inside the fork tubes?

Discussion in 'General Harley Davidson Topic' started by Porter, Dec 21, 2009.

  1. Porter

    Porter Junior Member

    After reading the post/pictures that Smitty posted on the bushings/seals in his fork tube I have a question: Regarless of how or when you change the fork oil, why does is appear so dirty?

    If the replacable parts in Smitty's post aren't showing a tremendous amout of wear, what is wearing to cause so much sediment in the oil? Or is is a case similar to "blood in the water"...where a little bit looks like a lot?

    Just seems to me from looking at my chain case oil, motor oil and transmission oil, and the shock oil and letting it settle and using a strong magnet, there was a significant amount of metal in the shock oil compared to all the others.

    I am not saying this is good, bad or indifferent, I am just wondering where it is coming from since I am not sure how the shocks work from a technical/hands-on standpoint. Again, this is my first HD so I am learning as I go..
  2. Porter

    Porter Junior Member

    It was just impressive see the color change of the oil in the from new to "used" but now that you bring up the possibility of water getting in the oil, perhaps that is why my observation was the oil had a very "grey" color.

    Also, it help to know that certain parts are wearing more or as intended to keep more expensive parts from wearing out....makes sense.

    Thank you for the insight!:D
  3. bikerdad

    bikerdad Junior Member

    I replace my forks with chrome when the bike had 1400 miles on it. I was very surprised at the change in the oil that quick. Quite dark grey coming out and new bright red going in!
  4. RickyBobby

    RickyBobby Active Member

    I had a seal leak on one leg. I decided to fix it myself and change the original oil out too. The original oil in my Showa forks was at best, fish oil. I installed a new seal and changed the oil. It was all pretty easy, except I had to run over to the dealer and buy more oil. Using the height of oil measurement, I need 4 quarts, not 2. I still have a little left, but that is pretty much going to waste. The 44mm tubes hold more than I thought. I don't really notice any dampening change, but the original oil was really foul stuff. This was at about the 4000 mile mark.
    Using the old bushing to install the new bushing would work well unless you have the correct installer. I used the old seal to install the new one. :)

    Merry Christmas all.

    NEWHD74FAN Experienced Member Retired Moderators

    Oil changes color for a number of reasons as Smitty says, however, it turning dark is due to oil collecting and keeping in suspension particles of aluminum oxide/corrosion, rubber seals/dirt that got past the slider seals, bug guts and organic materials. It is that slurry of stuff that looks so bad and honestly, it is the reason why I change it more often than HD recommendation...10,000 miles is fine, less better, and clean fluid in there means less wear, even though there is always the risk of introducing debris even if the risk is pretty low. Use the Self Help tab for easier method to change fork oil.
    Last edited: Dec 21, 2009
  6. Porter

    Porter Junior Member

    4 quarts? Do you have custom forks? My 07 ultra takes 10.8 oz per fork. That is less than a quart for both. That is interesting...

    I understand the arguments for and against changing the shock oil earlier than recommended and I am familiar with the self help technique that Glider posted on changing the oil. It was just shocking to me to see how dirty the oil gets compared to how bright red and clear new oil is. I am sure it is part of the design and perhaps the tolerances are much different in a shock than in the engine (hence the need for a filter) and there is really no way to boil off any moisture in the shock system, once it gets in there. My Spectro 6-speed transmission fluid looks just as it did when I put it in new. I don't even have metal on the magnet. I even had a mountain bike a long time ago that really saw some abuse, mud and water and the oil was still clear. But as Smitty posted, if there is a part in there that is designed to wear out to protect the fork tube, than I would think that is most of what I have observed plus a little moisture, since I happen to ride in the rain....

    All good stuff to learn and think about....:D
  7. Steve Di.

    Steve Di. Active Member

    I had a distinct front end clunk whenever I rode over bumps. Identifying the clunk was difficult until the left fork seal let go while under way. The fork oil drained all over my pants leg leaving quite a smelly mess. When the seal was replaced and fork refilled with oil, the clunk was gone, but the nasty smell of the oil was tough to get rid of.

    This incident left me believing there are some parts in the fork that are exposed to rigorous wear and tear.