Changing oil in stock shocks
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Road Master
Joined: Jul 2008
Posts: 1,092
Likes: 1
From: USA
Changing oil in stock shocks
I just bought some SG shocks to put on my RG and I keep hearing that it might be better to change the oil to a heavier grade. Can anyone tell me about this? What type,grade,how much,and how to do it? Any info would be appreciated. Thanks guys.
Outstanding HDF Member
Joined: Nov 2006
Posts: 2,049
Likes: 6
From: Oregon City, OR
I changed out to heavier oil (SE) in the front suspension when I swapped out my fork lowers and it was a noticable improvement, but have not heard of anyone putting heavier oil in the rear shocks.
Road Captain
Joined: Jun 2008
Posts: 550
Likes: 1
From: Arlington, TX
Road Captain
Joined: Jun 2008
Posts: 550
Likes: 1
From: Arlington, TX
here is another
https://www.hdforums.com/forum/touri...shock-oil.html
This one may be the best
https://www.hdforums.com/forum/touri...ks-better.html
https://www.hdforums.com/forum/touri...shock-oil.html
This one may be the best
https://www.hdforums.com/forum/touri...ks-better.html
Tourer
Joined: Jan 2009
Posts: 325
Likes: 0
From: Tennessee
I bought a set of 12" shocks off an 09 street glide to lower my Ultra a little. When they arrived, the dealer that took them off before they left their shop hadn't plugged them. Some of the oil had leaked out. Thus began my journey into the world of rear shocks.
I've read the threads above and there is a lot of good information, but the one thing that is hard to nail down is the quantity of oil in an 09 12" shock. There are lots of numbers out there and depending on the model year of the shocks, they may all be correct. I started with 10 oz and began to work my way up. I think I have about 11.5 oz in now. Still have issues with the bike bottoming out.
I have talked to 3 Harley shops and none of them can get any numbers from Harley on the quantity of oil to use in rear shocks. The only way to determine the correct amount is to drain a new shock to see what it holds.
The shock is going to bottom out at a specific position or length. The oil-air ratio is important in that too little oil leaves too much space for air and with maximum pressure in the shock when it's sitting on the stand, the pressure when the shock bottoms out (full compression) could be greater than the shock can handle because of the increased air pressure. On the other hand, too much oil could cause a hydraulic lock with the same overpressure problem.
I'll probably try some 7.5 Wt shock (not fork) oil next to see how that helps.
I've read the threads above and there is a lot of good information, but the one thing that is hard to nail down is the quantity of oil in an 09 12" shock. There are lots of numbers out there and depending on the model year of the shocks, they may all be correct. I started with 10 oz and began to work my way up. I think I have about 11.5 oz in now. Still have issues with the bike bottoming out.
I have talked to 3 Harley shops and none of them can get any numbers from Harley on the quantity of oil to use in rear shocks. The only way to determine the correct amount is to drain a new shock to see what it holds.
The shock is going to bottom out at a specific position or length. The oil-air ratio is important in that too little oil leaves too much space for air and with maximum pressure in the shock when it's sitting on the stand, the pressure when the shock bottoms out (full compression) could be greater than the shock can handle because of the increased air pressure. On the other hand, too much oil could cause a hydraulic lock with the same overpressure problem.
I'll probably try some 7.5 Wt shock (not fork) oil next to see how that helps.
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Road Master
Joined: Jul 2008
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From: USA
Well 1st of all I think I will put the shocks on and see what happens. I had an aftermarket lowering kit on at one time,it lowered the rear abpit an inch and I never had any prblems bottoming out,and I ride 2-up about 50% of the time.
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Road Warrior
Joined: Jan 2005
Posts: 1,416
Likes: 27
From: Northern Part of the Great Lone Star State
If memory serves me there is like 330 CC's in the 12" rear shocks
Hope this helps
Oh by the way this ain't rocket science so pretty much 325 cc's - 340cc's should be just fine...
AS far as the 12" shocks bottoming out you will get that more so due to the fact there is only 2" of travel with the rear shock
With the 13" there are 3" of travel so before you bottom out you have an extra 1" of travel...
FWIW
I have played with 12" and 13" and keep coming back to the 13" with a 1" lowering kit rather then the 12" without a lowering kit...For me I like the idea of having an extra 1" of travel for the wife and I when we travel or just ride around the block...
FFT
Hope this helps
Oh by the way this ain't rocket science so pretty much 325 cc's - 340cc's should be just fine...
AS far as the 12" shocks bottoming out you will get that more so due to the fact there is only 2" of travel with the rear shock
With the 13" there are 3" of travel so before you bottom out you have an extra 1" of travel...
FWIW
I have played with 12" and 13" and keep coming back to the 13" with a 1" lowering kit rather then the 12" without a lowering kit...For me I like the idea of having an extra 1" of travel for the wife and I when we travel or just ride around the block...
FFT
