Pulsing front brake

[headshrink]

I have less than 1K miles on my rotors (OEM), pads (Galfer black) & SS F line (Hel).

I haven't had a lot of good riding lately, with being out of commission for valve job, waiting for parts, handful of storms, etc. (normally ride 52wks a year), but I have noticed in the past couple days I am getting some pulsing in the front brake when I come to a stop. The pads seemed to bed fine initially, and I haven't done any hard riding since I did the brakes last. I tried to check the rotor for warping (don't know how that would happen), but I don't have one of those fancy run-out-measuring-do-hickies.... so all I have is my eyes, and a ruler. I really can't tell with any measure of confidence. Any ideas about this one, or is it cut and dry a warped disk?

[headshrink]

I used some brake cleaner on the rotor, and thought it was improved for my ride to work this morning..... but it got worse again at the end of my ride home. I'm thinking heat has something to do with it. Any ideas?

[stealth250]

Does the caliper piston retract all the way? Does the rotor show any blue tint as if it was getting hot? You can check runout with a pointer (coat hanger) fastened to the fork and barely touching the rotor. When you spin the wheel it will either stay consistently in contact with the rotor or you will see variance as it rotates. I suppose a small amount would be acceptable, but if it's new parts, I wouldn't expect any variance.
Also, you might check the slide pins for the caliper. I assume you took them apart and cleaned/lubed them(?)

[kkim]

also, when you installed it, did you make sure the wheel mounting surface was clean and that the disc is laying flat on the wheel? did you torque the bolts to the the specified torque and use a cross pattern when tightening?

[headshrink]

I did notice the pulsing again at the begining of my morning commute... so although heat [may] be a factor, I am guessing it is less significant than I previously thought.

Originally Posted by stealth250

Does the caliper piston retract all the way? Does the rotor show any blue tint as if it was getting hot? You can check run-out with a pointer (coat hanger) fastened to the fork and barely touching the rotor. When you spin the wheel it will either stay consistently in contact with the rotor or you will see variance as it rotates. I suppose a small amount would be acceptable, but if it's new parts, I wouldn't expect any variance.
Also, you might check the slide pins for the caliper. I assume you took them apart and cleaned/lubed them(?)

I don't know if the caliper piston retracts all the way... it releases, so it doesn't maintain a constant drag that I am aware of. Is there another way to test? What is the best way to clean them? I don't want to shoot brake cleaner in there, for fear of destroying the rubber seals.

I do not see any noticeable blue discoloration.

Also, I should mention that when on paddock stands, when I spin the front wheel, there is one spot it seems to make contact with the pad(s). It is very slight, and makes a slight noise when it does so, but doesn't [seem] to cause significant drag. I haven't paid too much attention to this, because it has ALWAYS done this, even with the original set of pads and rotor.... I will try the "coat hanger run-out test" when I get home.

I will double-check the slide pins as well. I did clean them, but don't think I lubed them... I do this automatically on cars, but didn't because the SM didn't say to do it. Sometimes I don't know if I should or should not second guess the SM.

Originally Posted by kkim

also, when you installed it, did you make sure the wheel mounting surface was clean and that the disk is laying flat on the wheel? did you torque the bolts to the the specified torque and use a cross pattern when tightening?

I don't think I cleaned the wheel mounting surface specifically, but I can't recall specifically. IIRC, there was a bid of residue from red Loctite in the mounting screw holes from the previous defective EBC snafu. Perhaps it is also worth a second look.

Bolts where torqued to spec with star pattern.

I don't see any obvious signs of glazing.... would rubbing steel wool over the rotor be effective/recommended?

[kkim]

You could try cleaning off the disc with some steel wool or a scotch brite pad. On cars, sometimes there is what is called pad transference that can have the exact symptoms you describe, where some of the pad material builds up on the disc and can cause irregular braking feel. Try it and see if it helps... if nothing else, you'll have a clean disc.

[Moldbuster]

Try this...
http://www.onthethrottle.com/howto/p...-installation/

Pinch bolts. Posted on the Sportbike Network forum...solved a lot of problems for a lot of guys who thought they had rotor issues when in fact their front forks were ever so slightly misaligned.

[headshrink]

Interesting video... the Ninjette doesn't have pinch bolts on the front axle, so it can't be that, BUT it still brings up an interesting possibility.

I just pulled the rotor off, cleaned it with steel wool, cleaned the mating surface on the rim, re-torqued the rotor, wiped the caliper clean (don't know what else to do there), wiped the pads with a dry rag, lubed the retaining pins & post that the long pad hooks onto. My test ride revealed the exact same results. I forgot to do the hanger trick when the bike was on stands, but the rotor seemed to lay flat on a flat surface, so I suppose it is good. I'm not sure what to check next.....

[Moldbuster]

Sorry, should have clarified...no pinch bolts, but the concept is the same. Perhaps the front axle bolt not being tightened properly could do it...or not having something seated quite straight. Maybe try loosen things up to let them re-seat. Could be just a very slight tweak. Often it is the smallest things that cause the greatest irritation.

[headshrink]

I took everything off, cleaned, and retourqued.... I don't know what else to do. I have an extra rotor, but prefer not to risk breaking it (no pun) if the problem is elsewhere, and the current rotor is still a brand new $300 emergency charge on the CC.

Should I look into caliper rebuild kits?

[stealth250]

As far as the caliper is concerned, I would take a preferably old brake pad and put it in the caliper against the pistons, then take a c-clamp and see if the pistons retract easily. (Also, it might be wise to put some tape on the outside of the caliper so the c-clamp doesn't scar it up). If they go in, then the caliper is probably ok. If not, then take the brake hose off or open the bleeder to see if that makes a difference.

[headshrink]

Originally Posted by stealth250

As far as the caliper is concerned, I would take a preferably old brake pad and put it in the caliper against the pistons, then take a c-clamp and see if the pistons retract easily. (Also, it might be wise to put some tape on the outside of the caliper so the c-clamp doesn't scar it up). If they go in, then the caliper is probably ok. If not, then take the brake hose off or open the bleeder to see if that makes a difference.

I can squeeze it in with my hand (with a little effort). Does that count?

I also just did the hanger test.... assuming I did it right, it was difficult to get and keep positioned, it didn't seem to reveal anything.

[kkim]

Bob,

if you have the front wheel off the ground, can you spin the front wheel freely even after you've squeezed and released the front brakes? If so, then I'd say you don't have a sticky caliper problem.

[headshrink]

Originally Posted by kkim

Bob,

if you have the front wheel off the ground, can you spin the front wheel freely even after you've squeezed and released the front brakes? If so, then I'd say you don't have a sticky caliper problem.

You are correct, I can. I THINK I MAY have discovered the problem..... will report after test ride within the hour.

[headshrink]

OK, here's what I think MIGHT be the problem.... although I did still have pulsing on my test ride to work:

I think the culprit may be the anti-rattle spring. I'm not 100% sure about this, but I believe the pad on the caliper side got behind the spring and pushed it over, and that part of the pad stayed stuck behind the spring, instead of freely sliding over it. There was some scratching/marring on the pad backing that supports this theory. Also, for the "slave" side, there are supposed to be two little points that stick up from the spring on the bottom to keep that pad in place (maybe it is only for assembly?). One broke off when I changed the pads, but I didn't think it would matter much. My hunch is it wouldn't if installed properly, but I may be wrong. Regardless, I accidentally broke the other one off today.

I may have done this by over compressing the piston (maybe that was the noise I heard way back when when I squeezed the break). I repositioned the spring, gave it a little lube, and figured I would order a new spring.... it's $20!!!

HOPEFULLY the spring slipped again, because I thought repositioning it would fix the pulsing altogether.

Does anyone know of a rebuild kit that includes hardware? I can't find one, and was thinking it might be cheaper than buying a little part here, and a little part there.

[kkim]

how about a used caliper off ebay?

http://cgi.ebay.com/ebaymotors/2008-...item5884ee1e1f

http://motors.shop.ebay.com/Motorcyc...=p4506.c0.m245

[headshrink]

Originally Posted by kkim

how about a used caliper off ebay?

Funny, you read my mind.... I was just thinking that when I signed back in

[kkim]

there are some calipers for sale in the ninjette classifieds as well.

http://www.ninjette.org/forums/showthread.php?t=68353

[headshrink]

Ebay scrap on order.

Do you think it is safe to ride until it arrives? I don't get any shaking/vibrations, and the pulsing is relatively minor (primarily felt under 30mph.... although I rarely have the need to touch the break above 30mph with engine braking).

[kkim]

I think you should be fine unless there is loud screeching or other types of noises coming from the brakes. Then again, you know better than any of us exactly what the problem is, so you'll need to make that call if you think the problem part could dislodge in such a way that would prevent the brakes from operating, or worse yet, jam.

[headshrink]

I'm comfortable with riding it to work until then, unless problems worsen/develop.... I'll just take it easy.

Although the new(used) caliper ended up being twice as much as a new anti-rattle spring, if the problem doesn't go away, at least it will answer the question about the caliper being the culprit.... will update when able.

[headshrink]

Update: I received the new (used) caliper yesterday. I decided not to put the whole caliper on, because I didn't have the time to bleed it, and was worried I may not have enough fluid to do it anyways. I put the new good clip on my current caliper. In doing so, however, I noticed that the old clip and pads seemed to be in their proper positions. I also used the retaining pins from the new caliper, just in case there was some binding issue (and lubed them). I used an emery cloth to clean break dust off the old pads, and put it all together again. I went on a short test ride, and no fix

To recap/clarify, when I first noticed the pulsing issue, was after my bike was in the stable for a few days in during some storms, and unrelated repair. Rotor, organic pads, SS line, and fluid was all new.... but had been broken in over a few hundred miles with no problems. The last riding I had done was in wet weather, and I don't remember it giving me problems then (don't know if rain is a factor or not). I have been VERY light on the breaks, both before, and after I noticed the problem. When I have the bike on stands, and spin the front wheel, I do get a little bit more contact at one point.... but then again, I have ALWAYS had this happen, and honestly think it was contacting more with the original rotor/pad sets. The "hanger test" didn't work well for me, think I will need a more stable/accurate tool.

I am wondering (just a preliminary theory), if the problem stemmed from using organic pads with consistently breaking TOO light.... could this have glazed the rotor? Remember I did take off the rotor and clean it with steel wool, but I didn't see any evidence that this marked the rotor in any way, therefore question if it could have been enough to clean up any glazing, if that is the problem. Just a thought, as I am running out of ideas. Remember, I only feel this at very slow speeds, and feel NO vibrations, or head-shake.

Ideas????

[rockNroll]

take the rotor off and scrub it well on both sides with scotchbrite and soap (purple power or something else harsh like that, don't get that crap in yer eyes!). You're welcome

[headshrink]

Originally Posted by rockNroll

take the rotor off and scrub it well on both sides with scotchbrite and soap (purple power or something else harsh like that, don't get that crap in yer eyes!). You're welcome

I take it you think it is a likely theory?

I haven't used scotchbrite before.... is it more abrasive then steel wool?

[rockNroll]

Originally Posted by headshrink

I take it you think it is a likely theory?

I haven't used scotchbrite before.... is it more abrasive then steel wool?

Likely theory? Yep. A warped rotor won't cause a pulsation in your front brakes unless the caliper is stuck on it's slides. As the "warpedness" of the rotor goes back and forth, the caliper will just slide back and forth with it. Get the picture there?

A bent rotor, due to things like a crash and impact can cause a vibration because there a more abrupt change in the rotors direction on it's two planes. If your rotor suffered an impact I'd think you'd know it.

So.. what causes a pulsation?

Usually, one of two things. A thickness variation is one. If the rotor's thickness varies around the rotor your caliper will be squeezing as the rotor is spinning and you're getting thick/thin/thick/thin as you're braking. this is a pulsation. If your new rotor already has a thickness variation then it's defective.
The second, and way more common is a buildup of brake pad material in one spot. It can be invisible or can be a dark spot. Elbow grease and abrasive soap is the best thing to do. It's cheap and easy to try

Call a brake rotor manufacturer and tell them your problem (cept maybe tell them it's their brand of rotor) and see what they say. I have been told by two different people at two different manufacturers that most of the motorcycle brake rotors returned as defective have this problem and aren't defective at all.

Over the years I'd guess that this has fixed better than half my motorcycle brake pulsations, but I'm kinda hard on them. Most of my rotors get replaced because they crack. There's no guarantee that this will fix your problem but it's worth tryin.

[randomwalk101]

Is this oem rotor or aftermarket? May be the quality of the rotor is up to par?

[headshrink]

Originally Posted by randomwalk101

Is this oem rotor or aftermarket? May be the quality of the rotor is up to par?

This one was OEM. In another thread I had an issue with EBC rotors, but while I waited for a resolution with EBC (although I haven't tried their replacement parts yet, they made sure I was more than happy), I ordered and installed new OEM rotors.

[KELPHYN]

This sounds a lot like a problem that a friend of mine had his ZX-10 after he installed braided brake lines and racing pads. He felt a pulsing throught the lever all the time except when he was running hard and the brakes heated up, then it went away. So if you feel confident in the braking performance,(front tire isn't locking up while braking is it?) take the bike out and do some hard braking and see if the pulse goes away. It may just be a characterestic of the parts.

[KELPHYN]

Oh just thought of something else you could try. You still have the stock pads in the back? If yes, you could try putting them in the front ( them are the same) and see if the pulse goes away. It's something to try and doesn't cost you anything but time.

[headshrink]

My wife just brought back some scotchbrite pads.... she said there were no purple ones, but she brought back some dark green square pads, and a pack that are metal balls. Shall I assume it is the metal one I should use????

[kkim]

the dark green scotchbrite and some very strong detergent. Rock mentioned purple power which is a detergent. Any household dish washing detergent will do, if you don't have something strong like he mentioned.

[headshrink]

What exactly is the goal? It sounds like this would help remove any brake residue, but I was hoping to remove any glazing.... a wire brush on a dremel maybe???

Any idea on what actually caused this?

[kkim]

have you googled "scotchbrite"? this is essentially a nylon based sandpaper. great stuff that comes in a variety of "grits" while being more durable and easier to work with than sandpaper or steel wool.

also, google "deglazing brake rotors" and "brake pad buildup".

[headshrink]

Perhaps I misunderstood what glazing was... I thought it was the rotor getting rubbed to a mirror finish in spots... I guess I was wrong.

[kkim]

cool... so, what you are trying to do is cut through any pad buildup that has been deposited onto your disc and hopefully give you a nice fresh surface for the pads to contact with. When you deglaze your rotor, you might want to do the same to the pads so you're starting with fresh materials on both sides of the friction interface.

good luck... I hope this solves your problem.

[headshrink]

Me too... I wonder why the steel wool, brake cleaner, and emory paper didn't work before... well, I'll try the regular way tomorrow and report.

[AzEKnightz]

Originally Posted by rockNroll

Likely theory? Yep. A warped rotor won't cause a pulsation in your front brakes unless the caliper is stuck on it's slides. As the "warpedness" of the rotor goes back and forth, the caliper will just slide back and forth with it. Get the picture there?

A bent rotor, due to things like a crash and impact can cause a vibration because there a more abrupt change in the rotors direction on it's two planes. If your rotor suffered an impact I'd think you'd know it.

So.. what causes a pulsation?

Usually, one of two things. A thickness variation is one. If the rotor's thickness varies around the rotor your caliper will be squeezing as the rotor is spinning and you're getting thick/thin/thick/thin as you're braking. this is a pulsation. If your new rotor already has a thickness variation then it's defective.
The second, and way more common is a buildup of brake pad material in one spot. It can be invisible or can be a dark spot. Elbow grease and abrasive soap is the best thing to do. It's cheap and easy to try

Call a brake rotor manufacturer and tell them your problem (cept maybe tell them it's their brand of rotor) and see what they say. I have been told by two different people at two different manufacturers that most of the motorcycle brake rotors returned as defective have this problem and aren't defective at all.

Over the years I'd guess that this has fixed better than half my motorcycle brake pulsations, but I'm kinda hard on them. Most of my rotors get replaced because they crack. There's no guarantee that this will fix your problem but it's worth tryin.

Isnt a thickness in variation = warp? This is the first time, working as an auto mechanic that warp rotor would not cause any pulsation.

Warping is basically metal has been heated to a certain point at certain spots and causing a run-out situation where you will have high and low spots like you mentioned. Which is exactly what "warping" meant.

Also, not trying to offend anyone here. But as you are squeezing the brake handle firmly, the pistons from the caliper will stick out and stay out unless you release the handle.

As long as the pressure stayed the same, the piston position will stay at the same position. Remember, fluid is not compressible, air is. THE only different will be the warped rotor moving "thick, thin, thick and thin" motion and resulting this pulsation headshrink is describing.

I hope I've described enough of what the brake system does. Hope this brake class 101 helps ^^.

My suggestion to HeadShrink, put in the new rotor and road test, I am most likely sure that's what it is from the description. A defective fairly new rotor.
Unless you have a stuck caliper/piston otherwise, good luck.

-AzEKnightz