1990 rear brake SWITCH adjustment

[7234ct]

Morning all,


First post
Recently bought a 1990 Fj1200. The PO lived on a dirt road, so it wasn't  pretty, but rode and  functioned.
The price was VERY good, so its now in my hands, insured, and awaiting registration.
I've done  a minor wash to eliminate the overall grittiness.
I know it will need inspection, just making it safe is  my goal thus far. Needed mirrors, an oil change, plugs, and the valve cover/ grommets were a bit weepy and  replaced......so that's what I've done thus far
All lights work, all gages work....horn etc....... HERE'S MY PROBLEM
The rear brake light switch works, and can be ACTUATED, but  the brake pedal doesn't t pull the pin/switch far enuf out to trigger the  brake light.
It' seems that its nearly @ the  end of  its adjustment limit, but man o man it's difficult getting any kind of wrench back there to adjust it.
So anyhow, the  switch DOES work.... I just  need the most economical way to get  the  brake  pedal to activate it.
The spring doesn't look to played out, so I don't think that's it.
The pressure needed for me with needlenose pliers was a  bit tougher than I'd  think, but I don't have a reference  point, so who knows.
Theres the stiff bentish wire that attaches the spring to the  the brake pedal cam, but I really don't  to bend that to mickey mouse something that seems  to be correct.
Any help is appreciated

[Pat Conlon]

Welcome, what's your name? We are informal here. When you get a chance, go over to the Introduction section and give us a post about yourself so we can get to know you better.
Re: the rear brake light switch. The switch has threads on the barrel and a lock nut which you move the barrel to adjust the point of activation. It is hard to get to...I adjust mine when I have the back wheel off.
Anyway, It sounds like you should plan on removing your back wheel and swing arm so you can clean and lube the swing arm bearings and linkages.

Typically the rear switch is adjusted when you put a set of fresh brake pads on. That is the point where you will have the least amount of travel on your brake pedal...due to the new thick pads..  As the pads wear down the pedal travel is increased, and that's why the spring in there, to allow the longer travel without pulling the guts out of the switch barrel.

Pat

[yamaha fj rider]

Typically the rear switch is adjusted when you put a set of fresh brake pads on. That is the point where you will have the least amount of travel on your brake pedal...due to the new thick pads..  As the pads wear down the pedal travel is increased, and that's why the spring in there, to allow the longer travel without pulling the guts out of the switch barrel.

Pat

Pat I hate to disagree with you because normally you give such good advise but the pistons in the brake caliper come out to make up for the wear of the brake pads, this is why you need to compress them when installing new pads.

Since the bike was driven off road so much it may just have some dirt in the switch, try cleaning it then some silicone spray to lube it, making it easier to pull. JMHO Hope this helps.

Kurt    

[rktmanfj]

Probably some crud in the lever pivot as well.

Removing the shaft and putting a dab of grease in there would probably help.

[Pat Conlon]

No worries Kurt. I notice my front lever travel and rear pedal travel is less when new thicker pads are installed. On the racing bikes they have a adjuster that the rider can access and adjust during the race that compensates for the extreme wear on the front pads...it takes the play out of the front lever from the thinner pads.

[yamaha fj rider]

Pat maybe I stand corrected but I thought that the adjuster on these bikes was to compensate for loss breaking due to heat and the need for increased pressure to be applied.

Kurt   

[Dan Filetti]

On the racing bikes they have a adjuster that the rider can access and adjust during the race that compensates for the extreme wear on the front pads...it takes the play out of the front lever from the thinner pads.

Here's Rossi doing exactly that, (remote side adjuster) while racing @ 190 mph, while passing two guys...  I saw the video of it once but for the life of me I can not find it, apparently it keeps getting taken down after being posted...



Dan

[Windmill]

I've always noticed brakes are firmer with new pads. I understood that it is to do with the lower volume of fluid in the piston chamber, hence less fluid to move before the pressure is applied.  Also was led to understand adjusters were to help compensate for changing characteristics of overheated brakes/fluid, but wear compensation also makes sense

[Pat Conlon]

I've always noticed brakes are firmer with new pads. I understood that it is to do with the lower volume of fluid in the piston chamber, hence less fluid to move before the pressure is applied.....

Yep, that's the reason.
Thick pads = pistons in = less fluid in the chamber = less free play.
Thin pads = pistons out = more fluid in the chamber = more free play.

Thanks mate.

[FJmonkey]

I've always noticed brakes are firmer with new pads. I understood that it is to do with the lower volume of fluid in the piston chamber, hence less fluid to move before the pressure is applied.....

Yep, that's the reason.
Thick pads = pistons in = less fluid in the chamber = less free play.
Thin pads = pistons out = more fluid in the chamber = more free play.

Thanks mate.

This means the compression value of the brake fluid is the cause? More fluid to compress...

[Pat Conlon]

Yea, you could think of it as more brake fluid to compress, but not due to the properties of the brake fluid itself..

I like to think that it's about fluid volume.

The m/c's have a certain volume of fluid they displace when they are engaged. This displacement is constant.
What changes is the fluid volume in the caliper chamber, that's variable, depending on how far the pistons stick out, which is determined by how thick the pads are.
For the same given stroke of the m/c, brake pad engagement with the rotor will happen sooner, earlier in the stroke, with a low chamber volume due to a thick pad.
To get the same amount of work done (pressure) The same m/c will have to move more fluid (later in the stroke) when the caliper chamber has more volume to fill, due to the pistons sticking further out, compressing thinner brake pads...

That's my understanding anyway.

[7234ct]

Alan here....the newbie who posted the original thread CT7234

I'm going with the rear wheel off to gain access to the  switch, clean off the crud off and  hopeflly it'll be a win.

Also more maintenance on the wheel bearings themselves

I forgot to mention when I bought the bike.... IT HAD NO REAR BRAKE PEDAL!!!!.

I got a good ebay deal as a lot that inclded a brake pedal.

It was funny that when I installed the pedal, the total movement was less than 3/8" travel  before the  pads engaged.

I was worried, but the  PO did say he did new pads about a year ago, and  rode for about 6 months without the pedal, so very little wear I guess equals little pedal movement.

I thank you for all the input..... I post what all transpires /transpired in about a week.

The bike is real ugly( can  say bedliner spray paint???), but a good thing is no one covets an ugly bike.
Did take er out for a quickie early morning spin, and  surprisingly balanced,  I'm gonna really love riding it on the 200 plus mile rides thru New England.

Side  note.... I was looking for  an FJ during this  fall & winter, and  found this  2 states away from me. Settled  on $550 for a running bike (36,000 miles).
                    Bought it on a Sunday, and  the next Tuesday a gorgeous 89 came up on craigslist for $1,300 35  miles away,...corbin seat, 4into 1
                    way way WAY prettier than mine.
                    Was  going to buy it (despite my wife screaming hobby out of control)  , but it sold THAT NIGHT.
                    So I'm kinda kickin myself, but  I'm gonna love the one I have for a couple of  years (both wife and  ugly FJ)

[fj11.5]

ugly paint or not, post up some pics of her,, fj  ,  or wife if you feel the need 

[SlowOldGuy]

Sorry, but brake fluid is INcompressible.  That means it does NOT compress, therefore, whether you have a little of it in the caliper piston bore or a lot of it, the brake lever force and travel are always the same.

The fluid does actually have some compressibility, but it would take some expensive test equipment to measure it.  You sure won't feel it.

This is just basic hydraulics.  It's also the reason for hydraulic brakes.  If it was a cable operated system, then it would need to be adjusted.  Hydraulics adjust automatically.

DavidR.

[Pat Conlon]

 Ah, there you are...been waiting. I don't think anyone said that brake fluid was compressable.