how much sag in the front fork?
fastjoe
Posted 8/18/2017 12:30 AM (#94710)
Subject: how much sag in the front fork?



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Put in Racetech fork springs about 2 yrs ago with their gold emulators when I bought the rig. I ended up with too much sag when I assembled the fork and put weight on it. Decided to just run it the way it was as I was due to leave on a trip and out of time.

Tomorrow I am going to install slugs to bring the fork up to the correct height. It came with a raked tree but no slugs. I'm going to rectify that because it does not have near enough ground clearance. I am also going to correct the sag which is 2+ inches right now on a fork with 5.5 inches of travel. As a percentage of travel how much sag should a sidecar rig have? Race tech recommends 25-33% of travel on two wheelers. What is right for sidecar rigs?
91 Gl1500 with Champion 2+2 car and car tire on the rear.

Any help or advice is appreciated.

Edited by fastjoe 8/18/2017 3:20 AM
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SwampFox
Posted 8/18/2017 8:10 AM (#94712 - in reply to #94710)
Subject: Re: how much sag in the front fork?



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I don't know the correct answer at all Joe, but on the Sportster with modified triple tree, without particular concern for precision, we set sag at 25-30% using a homemade slug spacer, which pretty much leveled the bike and performed well enough, altho the rig could use something like the emulators as there is still some excessive compression in a panic stop situation.
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tinboatcapt
Posted 8/22/2017 6:07 PM (#94789 - in reply to #94710)
Subject: Re: how much sag in the front fork?



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I don't have any monetary interest in TD except I have a AK-20 cartridges and a Penske Shock installed on my ST1100...and it was worth every penny.

Max McAllister of Traxxion Dynamics has a great YouTube.com series on suspension tech. The chapter on setting sag is Suspension for Mortals "Setting Sag" #13. In the series he gives some specific numbers, but more importantly, he tells why the numbers are important. From that, you should be able to find some starting points and do some fine turning. The first 20 minutes are general definitions and rear shocks, then at about minute 16 he talks about forks.

He has a 20 episode series on suspension and bike tuning for performance, but the basics apply to the street as well. After all, keeping the tire on the pavement is what it is all about.
The key thing to have is enough "Rider Sag" so the front will reach down to stay in contact with the pavement when rolling off a , or dropping into a dip.

My personal opinion (for what it is worth) is that with the heavy rig, operated at street/highway speeds, I would tune the sat to the shorter of the 25-30% range, and set the rebound toward the soft side.
FWIW
Jim



Edited by tinboatcapt 8/23/2017 7:33 AM
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fastjoe
Posted 8/23/2017 12:25 AM (#94796 - in reply to #94789)
Subject: Re: how much sag in the front fork?



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Thanks Jim.
What you suggested is what I ended up doing minus cartridges, I used cartridge emulators instead. Just got back from test riding it for the second time to test that the car had been moved to the correct alignment after the bike was raised back up to stock hieght in the front.
Turns out that the front suspension is listed as having 5.4 inches of travel but really only has 5.1 inches. Glad I checked before setting the sag.
I set the gold emulators to the recommended setting for a solo bike, set the sag closer to 25% than 30% and dumped the aftermarket fork brace that had been binding up the front fork.
It's a different rig now. I thought it was great before. Much better now even though the center of gravity is almost 2.5 inches higher

Edited by fastjoe 8/23/2017 12:26 AM
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fastjoe
Posted 8/23/2017 12:34 AM (#94797 - in reply to #94712)
Subject: Re: how much sag in the front fork?



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Lee,

The 25 to 30% turned out to be a good solid choice. Worked really well. Thanks.
The Gl1500 I have is the lead brick of Wings. It's heavy. To use the emulators I had to remove the wings antidive.. The heavier spring with the emulators work far better than the OEM setup in my opinion.
If and when you get the emulators you'll like them a lot because they make the fork more responsive and much less harsh provided they are matched with the correct springs when you install them.. On the wing I ended up with 1KG springs because that was the heaviest they have that will work with an emulator and that size fork tube. Turned out to be just right with this heavy bike and double car during panic stopping. Tried some panic stops tonight just to see how it all worked. Stops much better now



Edited by fastjoe 8/23/2017 2:05 AM
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cycleman
Posted 9/6/2017 7:44 PM (#94991 - in reply to #94710)
Subject: Re: how much sag in the front fork?


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When trying to beef up the front end of a gold wing, I always go to linear springs based on the weight of the bike and the rider. They do the job and you should be looking at in the range of 1 to 1 1/2 inch of sag.
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VLAD
Posted 9/7/2017 5:18 PM (#95000 - in reply to #94796)
Subject: Re: how much sag in the front fork?



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OEM springs too soft for sidecar use. I install Progressive and happy with it.
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draperg1
Posted 9/25/2017 10:28 AM (#95172 - in reply to #95000)
Subject: Re: how much sag in the front fork?



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FYI Progressive is now out of business! Its a shame, they provided a good product reasonably priced.
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dholaday
Posted 9/25/2017 11:12 AM (#95175 - in reply to #95172)
Subject: Re: how much sag in the front fork?



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Check out EPM [one of our advertisers]  - they're good people and can probably help.

 Duncan

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Al Olme
Posted 9/25/2017 1:30 PM (#95176 - in reply to #95175)
Subject: Re: how much sag in the front fork?


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This a second on EPM. They make a series of great products and they understand sidecars. Klaus is the owner, they can be reached at 732-786-9777 or info@epmperf.com. The website is www.epmperf.com. EPM can also rebuild almost any shock that can be opened for rebuilding.
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