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
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
Quote from: Pat Conlon on March 31, 2013, 10:56:17 AM
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
Probably some crud in the lever pivot as well.
Removing the shaft and putting a dab of grease in there would probably help.
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.
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
Quote from: Pat Conlon on March 31, 2013, 01:30:09 PM
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...
(http://i185.photobucket.com/albums/x139/19doug90/brakeadjuster.jpg)
Dan
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 :biggrin:
Quote from: Windmill on March 31, 2013, 03:26:54 PM
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.
Quote from: Pat Conlon on March 31, 2013, 04:00:23 PM
Quote from: Windmill on March 31, 2013, 03:26:54 PM
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...
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.
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)
ugly paint or not, post up some pics of her,, fj , or wife if you feel the need :biggrin:
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.
Ah, there you are...been waiting. I don't think anyone said that brake fluid was compressable.
Ah but, old brake fluid can be very compressible :yes:.......it absorbs moisture and becomes aerated. :blush: Hence only storage in sealed containers and one of the reasons to change the brake fluid completely at regular intervals..... The difference does relate to volume though, as demonstrated in the difference in response of systems using narrower or wider bore pipes.
Sorry Alan, getting hooked up on the theory and your thread drifting off a little. :pardon: Sure someone else more experienced here will tell you but are you sure the new brake pedal is for the correct model.........there seem to be many minor variations in the same item between various models, as I know to my cost having bought wrong stuff I was sure was correct. It would only take a small difference for the pull length to be different. Sure previous advice to thoroughly free off the switch is correct too though. Like the PO's theory by the way, install new pads but remove brake pedal and the pads will last longer :biggrin: unlike the rider I suspect........
I can empathise with your bike condition, mine was the same but riding it even with faults was enough to ensure I persevered with it. Keep at it, it will all be worth it in the end :drinks:
Quote from: Windmill on April 01, 2013, 03:57:20 AM
Ah but, old brake fluid can be very compressible :yes:.......it absorbs moisture and becomes aerated. :blush: Hence only storage in sealed containers and one of the reasons to change the brake fluid
Yes it absorbs water, but water is not compressable in its liquid form and its presence alone won't aerate the fluid unless it boils, which it will do at a lower temperature than the fluid.
Its presence will also cause corrosion and rust, it is less viscous than brake fluid so more prone to leaking and it lowers the boiling point.
You can often stop leaking / weeping seals for a considerable time simply by refreshing the fluid.
If you have a container full to the brim with an incompressible fluid (and we'll ignore surface tension), adding a cup of liquid to that container will cause a cup of liquid to spill out. The size of the container is utterly ignored.
If the bore of the caliper's piston is slightly conical, getting larger as the piston adjusts further out, then there will be a mild difference in the travel you get at the lever with new vs old pads.
I wonder if the incredible heat that a racebike's brakes undergo has any influence on a rider needing to change the adjustment of their controls, possibly.
Quote from: Windmill on March 31, 2013, 03:26:54 PM
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.
Thin pads, thick pads, should feel the same.
You are talking about an extra thimble full of fluid in the chamber. The extra force required to move it only has to overcome weight and friction. Given the enormous advantage the lever and the hydraulics give you, I don't' think even NASA could measure it.
Flossing before you ride would have a bigger impact on you power to weight ratio than this would have on the brakes.
Noel
Noel, I agree, the "feel" remains unchanged, but have you noticed a difference in lever travel when going to new pads?
Pat,
I was merely stating the simple fact of fluid incompressibility and hydraulics.
To tell the truth, I haven't really changed brake pads that often to notice any difference in lever "travel." I might notice a difference in lever "feel" but that should be attributed to fresh pads providing better stopping power than worn out pads.
But even then, I recall new pads feeling a little "squishy" until their bedded. The pad material does compress slightly during the break-in and bedding period. But the lever travel should be identical from a new pad all the way to grinding metal on metal.
DavidR.
Quote from: SlowOldGuy on April 01, 2013, 12:15:26 PM
..... But the lever travel should be identical from a new pad all the way to grinding metal on metal.
Should be...but it isn't. That's why the racers use these:
(http://www.constructorsrg.com/images/levers/image_large_remote_lever.jpg)
http://www.constructorsrg.com/levers/remote.html (http://www.constructorsrg.com/levers/remote.html)
"Derived within the top levels of motorcycle road racing, remote (left hand) adjust brake systems allow riders to compensate for front brake system variations due to system fade, and brake pad wear during race situations...."
Of course that is a extreme example, but the basic principal applies. Lever/pedal (free play) travel is 'slightly' different between thin pads and new thick pads.
Quote from: Windmill on April 01, 2013, 03:57:20 AM
Ah but, old brake fluid can be very compressible :yes:.......it absorbs moisture and becomes aerated. :blush:
Well yeah... once it's seriously contaminated with water (and at what point can you consider it still 'brake fluid'), and under braking the water turns to steam (and steam is VERY compressible).
But regular maintenance keeps the brake fluid pure, and as David stated, it's just not compressible.
Quote from: Pat Conlon on April 01, 2013, 12:42:40 PM
Quote from: SlowOldGuy on April 01, 2013, 12:15:26 PM
..... But the lever travel should be identical from a new pad all the way to grinding metal on metal.
Should be...but it isn't. That's why the racers use these:
(http://www.constructorsrg.com/images/levers/image_large_remote_lever.jpg)
http://www.constructorsrg.com/levers/remote.html (http://www.constructorsrg.com/levers/remote.html)
"Derived within the top levels of motorcycle road racing, remote (left hand) adjust brake systems allow riders to compensate for front brake system variations due to system fade, and brake pad wear during race situations...."
Of course that is a extreme example, but the basic principal applies. Lever/pedal (free play) travel is 'slightly' different between thin pads and new thick pads.
My understanding of these is they do exactly what our adjustable levers do but without having to take your hand off the throttle. The left hand for a Motogp rider is the only one that has any free time.
The only reference to compensating for pad wear appears to be in the ad writers mind. They also mention compensating for brake fade. I would be very surprised if these high tech, cutting edge bikes suffered from this. I have never heard of brakes going off as the race progresses.
I do believe (I have read) that riders like a different feel to the brakes at different stages of a race though.
Noel
Quote from: ribbert on April 01, 2013, 07:17:52 PM
The only reference to compensating for pad wear appears to be in the ad writers mind......
Heh heh, ok Noel, it must be someone's creative imagination...who do they think they are kidding?.. :flag_of_truce:
Another issue racers have is head shake. When the front wheel goes into a mini tank slapper the side to side force causes the pads to push the pistons away from the pads/rotors. I have had a tank slapper and had no brake pressure right after. One or two pumps and it is back to normal. Watch any of the motogp guys and they often check brake pressure after a steering episode.