anti-dive

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Oct 13, 2009 | 03:36 AM

#11

t150vej

HDF Community Team

Joined: Dec 2005

Posts: 5,375

Likes: 2,570

From: NC USA

Quote:

Originally Posted by notlost_nc

I removed mine and put Progressive springs in it. Still rides like an old tractor.

I've never actually looked at a pair, but that's why I suggested the dampers be changed. They are a different part number and logical to assume they would have different ports since the air pressure has more to do with holding the fluid in the bottom of the legs than helping spring action.

I tried some "heavy duty" fork oil (30w) and didn't like it at all with air or without (when I had a bad air leak) Seems to work best with ATF or HD fork oil and 15lb of pressure.

Oct 13, 2009 | 10:19 AM

#12

1skrewsloose

Stellar HDF Member

Joined: Feb 2009

Posts: 2,936

Likes: 20

From: Driftless Area

I love anti-dive, mine still works, 90 fxrs-sp, went to mini-apes, had a friend at work make a custom bottle that mounts to where you would mount an oil cooler. Only needs to hold about a little less than two cups liquid from stock bars.

kinda looks like a liquor flask. I'm not an engineer, but I think it helps the keep the front geometry where it should be. When not braking I love the ride. bottle only needs to handle 20psi pressure max.

Oct 13, 2009 | 08:09 PM

#13

perpulreaper

Cruiser

Joined: Jun 2007

Posts: 249

Likes: 1

From: maryland

is this why my front forks need air , just thawlt they where like air shocks

Nov 27, 2009 | 10:27 PM

#14

NorthGeorgiaHawg

Club Member

Joined: Jun 2007

Posts: 3,193

Likes: 7

From: North Atlanta Area, GA

Quote:

Originally Posted by perpulreaper

is this why my front forks need air , just thawlt they where like air shocks

They are not really air shocks. It's an "anti-dive" system. The air you pump into it is really not used all that much until you apply your brakes. It can soften or stiffen your ride to an extent, but that's not what it's primarily there for. The high-pressure air is stored in both the fork tubes and also in the crash bar (on older bikes) or in the handlebars (on "later" bikes, like my '95 FLHTP). When you apply the brakes, a solenoid clicks (you should hear it click when you apply your front or rear brakes), closing a valve in the air line at the top of the forks. When this valve closes, it traps the high-pressure air in the forks, which is a very small volume compared to the total volume of air in the forks plus the air in the crash bar or handlebar reservoir. The air being trapped in the small volume of the fork (at high-pressure) when the brakes are applied stiffens them considerably. This is because the small volume of air in the forks (at high pressure) won't compress nearly as much as the much higher volume of air at the same high pressure in the forks + the crash bar or handlebars would. The physics of this low-volume, high-pressure air in the forks works to fight the natural tendency of the bike to dive when braking. This is "anti-dive" at work.

If your anti-dive system is functioning properly (the solenoid clicks when you apply the brakes) AND has the right amount of air in it (15-20 lbs pressure), the system will work quite well to prevent front-end diving when braking hard.

So, keep your air pressure at 15-20 lbs, and make sure your solenoid is clicking when you apply the brakes! You will feel the difference...

Last edited by NorthGeorgiaHawg; Nov 27, 2009 at 10:46 PM.

Nov 28, 2009 | 07:28 AM

#15

Moog Player

Road Captain

Joined: Oct 2009

Posts: 701

Likes: 1

From: The Great Southwest Desert

Went through the work to keep it all alive during/after a complete rebuild of the front forks last month. Rides much nicer than my old non air FL ever did no matter what oil or valving combo I had in it.

Nov 28, 2009 | 07:50 AM

#16

perpulreaper

Cruiser

Joined: Jun 2007

Posts: 249

Likes: 1

From: maryland

with my windshield cut down and my strait ppips i would have a hard time hearing a click. i use my front brakes all the time anyway

Last edited by perpulreaper; Nov 29, 2009 at 07:36 AM.

Nov 28, 2009 | 08:02 AM

#17

NorthGeorgiaHawg

Club Member

Joined: Jun 2007

Posts: 3,193

Likes: 7

From: North Atlanta Area, GA

Quote:

Originally Posted by perpulreaper

with my windshild cut down and my strait pips i would have a hard time hearing a click. i use my front brakes all the time anyway

Perpul - to check it, just turn your ignition on but don't start the bike. Apply either front or rear brake and listen for the click. Probably best to check front and rear individually to make sure each of them makes that relay click. My relay is in the dash up front, but mine is an unusual bike. Yours is probably under one of the side covers. I wouldn't ride my Big Fat Hog without the anti-dive working. My front-end is really heavy, and she would dive like crazy!

Good that you use your front brake, too! Some riders don't for some reason, as discussed in other threads. I use both front and rear for best control... when I wanna stop, I wanna STOP!

Nov 28, 2009 | 08:43 AM

#18

Dr.Hess

Seasoned HDF Member

Joined: Aug 2007

Posts: 8,195

Likes: 3,085

From: NW AR

There's no relay controlling the valve. The control for the valve is wired into the brake light circuit. If your brake light comes on with the rear brake, then the valve is being energized. The rear brake light is controlled by a pressure switch. You have to have moderate rear brake pressure to activate it. Just a little amount won't turn on the rear brake light, at least on my bike. The front brake has a switch, and just moving the lever a little will turn it on. Yeah, with the motor off, ignition on, grab some front brake and listen for the click from up front. The valve (solenoid) is still available from the dealer. There's a new part number, but it's the same valve. I replaced mine a couple years ago when it wouldn't click anymore.

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Nov 28, 2009 | 09:08 AM

#19

NorthGeorgiaHawg

Club Member

Joined: Jun 2007

Posts: 3,193

Likes: 7

From: North Atlanta Area, GA

Quote:

Originally Posted by Dr.Hess

Interesting, Dr... I *thought* my bike had a relay for it, but I might be confusing it with the starter relay. My bike has the toaster dash, and that thing is CRAMMED FULL with all kinds of wire bundles, the starter relay, the turn signal auto-cancellation module, and lot of other things. It has a little module of some sort in the dash that clicks when I apply either brake (I thought it was a relay), and if I disconnect it the anti-dive stops working. But it's a police bike, and I've found a lot of things that are "different" on it from the standard FLHT shop manual (like the clutch interlock, positioning of some electrical components, etc.). I even bought the police supplement for it on eBay, which turned out to be a huge waste of money... I learn as I go!

Nov 28, 2009 | 02:16 PM

#20

gnafin

Thread Starter

Tourer

Joined: Sep 2009

Posts: 292

Likes: 3

From: Westland, Michigan

Hmmm i just check out mine and i get no click and i have the spedo removed. and i do see the guy that had the bike before me had the system removed. has plugs in the top of forks.....guess i will try to make it like stock...

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