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GS1100E anti-dive. How to get rid of it and why?

  • Thread starter Thread starter Anonymous
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Anonymous

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I've heard of people getting rid of or disabling the anti-dive unit. What is the reasoning behind this and how do you do it? Can you buy a block of plate or do you just leave it on and reaplace the banjo bolt with a regular bolt and replace the dual banjo bolt on the calipers with this one?
 
I dont recomend getting rid of the anti dive unless you have problems with it. if you do then a simple elimination mod is to remove the banjo bolt on both th a/d unit and the brake caliper, swap the locations so the shorter bolt is on the caliper tighten it down, bleed the brakes build a loop with the short hose and longer bolt then reattatch to the a/d unit. now all should be sealed and the a/d is no longer functional. you can add about 1.5 inch spacer with a piece of steel pipe that is the same diameter as your springs with a fender washer that will fit inside your fork tubes between them for some additional stiffness.
 
I had anti-dive on my 81 Seca. When I removed it I thought my brakes improved. I'm not saying this is going to happen but that is what it seemed like to me.
 
I've just heard that a lot of people disable it and I could never really see why so I thought I'd ask. I'm not having any problems with it so I'll just leave it.
 
Anti-dive was a popular thing in the 80's. The idea is that when you apply the front brakes some mechanism closes valves in the fork to make it 'stiffer', therefore keeping the front end from diving so much during braking. Most magazine tests said there was not much improvement in front end dive and the extra plumbing resulted in a softer brake feel. The real problem was soft springs and a lack of damping in the fork. I have removed my anti-dive by simply removing the extra brake lines, using the single banjo bolts, and plugging the holes in the anti-dive units on the forks with bolts. I use Progressive fork springs and heavier fork oil. I weigh 225 lbs. and don't feel I suffer from too much front end dive.

Joe
 
Eliminating the anti-dive will make a difference depending on what shape your bike's in and how you ride.

Removing the extra plumbing decreases the volume of fluid required to apply pressure to the calipers so you may feel a 'tightening' of the brakes, i.e. less lever pressure. The flip side is the bike may compress the forks (dive) slightly more when braking. Again, this is affected by how agressively you ride and the condition of the anti-dive before being eliminated.

As Joe Nardy mentioned above the smart money, for bikes of this vintage, is to go with Progressive springs and heavier fork oil if the anti-dive is eliminated. The Progressive springs do the job of the anti-dive anyway. Next is a set of braided brake lines.

I still have the anti-dive on my 1100. I don't ride like a madman and it seems to work ok.
 
As Joe Nardy mentioned above the smart money, for bikes of this vintage, is to go with Progressive springs and heavier fork oil if the anti-dive is eliminated. The Progressive springs do the job of the anti-dive anyway.

Thats wht i did on mine. but just a bolt with a proper sealing washer into the anti dive unit to prevent any possible leakage
 
I think I'll just leave it be. I don't ride the GS like a madman anyway, I save that for my Bandit. The GS is more like my Sunday rider.
 
If improving spongy brakes is the objective I'd first convert the lines to stainless before thinking about changing the antidive unit.
 
My only reason for dispensing with the anti-dive was the cost of the two extra lines it needs when I fitted stainless steel brake lines. I just used a bolt to black off the a/d unit as others have described here. I didn't notice any difference in suspension.
 
as a bit of a caveat to those that have removed the anti-dive or are contemplating it... They are also the fluid path for compression, if you just blank them off, you are preventing the proper amount of fluid to flow between the upper and lower fork leg segments (on either side of interior piston) when the legs compress and rebound. You must drill out the fluid cup equalizing holes to approximate the flow through the anti-dive valve when open, failure to do so WILL result in blowing a fork leg seal, inside out, literally, due to the high pressure generated by the lack of proper oil passage between compression and rebound segments of the fork leg. I found out the hard way and re-engineered accordingly
 
daveo said:
as a bit of a caveat to those that have removed the anti-dive or are contemplating it... They are also the fluid path for compression, if you just blank them off, you are preventing the proper amount of fluid to flow between the upper and lower fork leg segments (on either side of interior piston) when the legs compress and rebound. You must drill out the fluid cup equalizing holes to approximate the flow through the anti-dive valve when open, failure to do so WILL result in blowing a fork leg seal, inside out, literally, due to the high pressure generated by the lack of proper oil passage between compression and rebound segments of the fork leg. I found out the hard way and re-engineered accordingly
Click to expand...


Dave please be more descriptive. i dont understand what is happening.
 
scotty he is refering to when you totally remove the a/d unit from the forks, if you just bypass the brake line the the valve is still there and functional and allows the fluid to pass thru both sides of the fork tube. if you take the valve off the forks then you need to create a passage for fluid to move or you can blow the seals.

your fork fluid does not flow thru the brake line if it did then every time your forks would compress your front calipers would squeeze together and bring you to a stop :twisted:
 
slopoke said:
Dave please be more descriptive. i dont understand what is happening.
Click to expand...

Sorry, I'll try...when the anti-dive is activated, a plunger-valve closes the oil passage between the compression and rebound sides of the fork leg. This prevents the fork leg from compressing, or 'diving'. This anti-dive valve also has a pressure relief function, which, when the compression side is overpressured, opens, to allow fluid to flow to the rebound side of the leg, thereby alleviating the over-pressure on the compression side. When the AD valve is removed, so is the pressure relief. Effectively, you're running in anti-dive mode constantly, as the pressure is only equalized by a small pair of holes in a fluid retention cup 'oil lock piece' at the bottom of the leg.Since you don't have the proper amount of fluid flow available between compression and rebound, and no pressure relief, the upper seal becomes the weak spot if you hit a good sized hole (how I found out) or whatever, and blows inside out. The holes in the 'oil lock piece' must be drilled larger to return the fork to it's regular function. I'll post these pics too, so you can see what I mean, probably better than my explanation.....let me know if you see what I mean
site1155.jpg

site1156.jpg

site1157.jpg
 
As an interesting post-script to this string I was just in the middle of flushing the front brake lines on my 1100E. Having the usual troubles with bleeding the a/d I thought 'what the heck' and eliminated it with a couple of M10 bolts.

Brake feel is MUCH improved over stock, even with non-braided lines. The line flush was brough on by the addition of a new GSXR master cylinder but so far it's better than I ever remembered it...
 
When I first resurrected my GS last year, I rode it for a weekend and had spongy brakes. I replaced the brake fuid and it would stop me plenty quick with just two fingers. I read somewhere on the forum that you should replace your brake fluid every two years. If this is followed I believe that most of the spongy dissappears.
 
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