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Message started by Greg on 04/02/13 at 07:06:20

Title: Can I add more fork oil?
Post by Greg on 04/02/13 at 07:06:20

I had my forks done by a local shop. I can make my front end bottom out if I ride just right. They said they added the correct amount and weight fork oil. Would it hurt anything if I add a little more?

Title: Re: Can I add more fork oil?
Post by Dave on 04/02/13 at 08:27:36

Well......maybe. The damping effect comes from the thickness of the oil mostly, not from the quantity as long as the poper amount is in the forks. There are instances when some people do add additional oil to stiffen up the action of the forks.

Adding more oil reduces the amount of air in the system, and as the forks compress the pressure inside the fork rises.....and the smaller the air space the higher the pressure becomes......so more oil can help to stop forks from bottoming out if done correctly. Too much oil and the forks will not work well, an the pressure on the seals could become excessive.

It is hard to determine how much oil is in the forks after they are on the bike. Some bikes have you remove the caps and springs and drop the forks and measure the height of the fluid when the forks are compressed - but I have never seen that measurement for a Savage. I believe the proper oil amount is 14 oz. per leg. I also believe the standard weight is 15.....which is almost identical to ATF oil for automatic transmissions.

Title: Re: Can I add more fork oil?
Post by WD on 04/02/13 at 08:51:38

Modern ATF (Dex 3 and newer) is 10w or 5w or even 2.5w (Dex 6). Type F is 15w or 20w depending on who blended it to which era spec. Type F will eat your fork seals. B&M Trick Shift (super expensive "performance" ATF) is actually just Type F... ::)

Can you add any to your existing fill? Yes. An ounce per side at a time, with test riding in between each addition. If you hit 18oz per side, assuming you had 14 oz per to begin with, and it still feels soft or is bottoming out, drain them and go up a weight or two on your fork oil. You can get up to 40w from Bel-Ray. The thicker the oil, the more likely you are to blow out a seal.

I use Dex3 in my Savage. Drop out the forks, drain them, collapse the upper tubes into the lowers. With springs out fill to the top of the upper tube, extend forks, add guts, bolt back in. Ride is still a bit soft for my liking, but, I'm used to springer and girder front ends. I hate fork dive...

Title: Re: Can I add more fork oil?
Post by justin_o_guy2 on 04/02/13 at 09:18:23

What do you weigh?

What is "just right"?

Title: Re: Can I add more fork oil?
Post by Greg on 04/02/13 at 09:50:35

JOG, I am 300+ lbs. Riding just right is grabbing the front brake so the bike stops instantly. It will dive and I hear and feel a hard clunk. It will also do the same when I get to the small water trough at the end of my driveway. My old forks didn't do this.

Title: Re: Can I add more fork oil?
Post by verslagen1 on 04/02/13 at 09:52:08

check you steering bearings, might be loose.

Title: Re: Can I add more fork oil?
Post by Greg on 04/02/13 at 10:04:33

I thought of the bearings. I will check that as well. That is done by tightening the bolt going through the triple tree right?

I did forget to mention that these are the 4" extended tubes. Forks by Frank said to add the stock amount of oil since the travel didn't change. I spoke to the shop and they agree but also disagree since the air volume changed. I think I will check the bearings and if they are tight, add some 30 weight to the 15 that is in there and see where I end up.

Also, they didn't add by volume, they did the 75mm from the top.

Title: Re: Can I add more fork oil?
Post by WD on 04/02/13 at 11:09:11

4" longer tubes is a lot of extra "oomph" coming into the lowers. You need more/heavier fluid, especially with your physical weight. If the shop went strictly "by the book" for your fluid work, they don't have a clue about what they are doing. There are several reasons more than 1 weight of fork oil are offered. Apparently, none of the "mechanics" fall outside of the "statistical average" the book specs are written for.

The stock fill is fine for somebody 4'8"-5'10, under 200 pounds. Outside of that range, it's experiment and see what works time.

Title: Re: Can I add more fork oil?
Post by arteacher on 04/02/13 at 11:18:23

Personally I would not change the weight of the oil. This will make the movement stiffer throughout the entire travel. Add oil in small increments (5ml) at a time until your forks don't bottom out. You want the same amount of air in there as the stock forks had, minus a bit at a time. Too little air and you will blow the seals, and will have to look at stronger springs, or longer spacers. (more pre-load.)
I hope the shop who did the work took the springs out when the filled the tubes to 75mm from the top. If they didn't there isn't nearly enough oil in there.
When I put the rake kit on mine, with 4" longer tubes, I had the same problem.
The longer tubes were from Franks, but they were for a Yamy Verago 1100, which use thicker walled tubing. The kit included new dampers to accommodate the smaller bore, but the instructions said to put in the stock amount of oil for the S 40, not the Verago. I bought Progressive springs that fit the Verago, and put in the Verago spec'd amount of oil, and the problem went away, not because of the springs, but because of the amount of oil. If you talked to Progressive they might have a longer spring the same diameter as the stock spring.

Title: Re: Can I add more fork oil?
Post by gdrseeker on 04/03/13 at 10:32:14

180B4F0 wrote:

I Thought it was OK to use Type F instead of Fork Oil. I just recently changed mine and used ATF. ?? So Dex 3 ATF is ok just not Type F??

Title: Re: Can I add more fork oil?
Post by WD on 04/04/13 at 10:01:25

If you used Type F, don't sweat it. I use it in my 1969 Dodge 727 trans which is spec'd for Dexron/Mercon, hasn't eaten the seal away yet. Have done so for almost 9 years, either straight Type F or a blend of Dex 3 and F.

Type F isn't very compatible with modern synthetic rubber. You may have to change the seals every 3-5 years, key word is may. I have no idea what compound Suzuki uses in their fork seals, I do know that Honda and Yamaha seals react "unfavorably" in the presence of Type F but do fine with Dexron/Mercon 3. Switching from fork oil to Dex 3 actually significantly slowed a leaky seal that failed on mine the day I bought the bike brand new in February of 1998. Barely enough to dampen my finger tip since 2010 when I last had the forks off the bike.