Front Brake Vibration - Moderate Pressure

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Front Brake Vibration - Moderate Pressure

Post by JTChiTown » Sun Jun 22, 2014 8:40 pm

Guys,

Hoping to tap into so hidden knowledge here. Went on my first ride with Miles leading the pack this past Saturday. As some of you know, I just picked up my bike about 6 weeks ago. Only put about 300 miles on it as of today, including Saturday. The 675 was originally sold in Hawaii and shipped here. It only has 4500 miles, and sat for over a year down in Killeen before I bought it.

Anyways, on the ride I noticed that I had a significant pulsation from the front brakes at higher speeds (50+) under moderate pressure. When I hit the brakes from high speeds, it wasn't nearly as severe, or when it was near panic, it didn't seem as bad either.

Here's what I'm thinking. Either I've got a wrapped rotor, which doesn't make sense as these are full floating. My second thought is that there is a spot on the rotors from it being shipped from Hawaii, where the exposed portion of the rotors had salt corrosion from the sea air (we have this problem shipping cars from Australia and Korea) and the section covered from the pads didnt.

Has anyone experienced something like this before? And does someone have a dial indicator with a role tip I can borrow? I have an indicator, but the tip that's on it won't move slowly over the rotor surface.

Either way, I'll probably replace the rotors after the 4th holiday, but the engineer side of me wants to know what the problem was.

Appreciate any thoughts!
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Re: Front Brake Vibration - Moderate Pressure

Post by fixxervi6 » Sun Jun 22, 2014 9:49 pm

Pulsing as in it pushes back against the break lever, or pulsing as in grabbing harder in spots than other spots
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Re: Front Brake Vibration - Moderate Pressure

Post by U-Turn » Sun Jun 22, 2014 9:56 pm

Maybe the floating isn't floating but I would think it would break loose under use.
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Re: Front Brake Vibration - Moderate Pressure

Post by DemonDuck » Mon Jun 23, 2014 1:12 am

I would try sanding the rotors a tad and roughing up the pads. Also flush out the brake fluid. If it hasnt been done since the bike was shipped to the states then it could have a bunch of moisture build up in the brake fluid. That can cause weard stuff to happen.
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Re: Front Brake Vibration - Moderate Pressure

Post by JTChiTown » Mon Jun 23, 2014 6:04 am

Thanks for the suggestions. I replaced the pads with Ebc HH pads, and took some 120 grit to the rotors, both sides. Problem still persists.

I haven't bleed the brakes yet, but I'll try that this week. If that doesn't work, I was planning on pulling the rotors and really trying to clean and free up the float area on the to see if there is one that is seized up tight.
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Re: Front Brake Vibration - Moderate Pressure

Post by Stardog » Tue Jun 24, 2014 3:57 am

Go somewhere desolate, run her up to about 130 and brake like hell down to zero or close. Obviously don't just grab the lever and yank but go smooth on it and slow down as fast as you can. If it gets better but is still there then do it again. You probably have some friction material built up on the rotors. Like they said, bleed the brakes first.
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Re: Front Brake Vibration - Moderate Pressure

Post by Rhino » Tue Jun 24, 2014 6:33 am

Stardog84 wrote:Go somewhere desolate, run her up to about 130 and brake like hell down to zero or close. Obviously don't just grab the lever and yank but go smooth on it and slow down as fast as you can. If it gets better but is still there then do it again. You probably have some friction material built up on the rotors. Like they said, bleed the brakes first.
You don't need 130, you can bed brakes at 60 mph. I did it on the access roads around my house.

I recommend sanding your brake discs with a high grit sand paper before doing this to try to get material off the discs first. Do both sides of all discs.

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Re: Front Brake Vibration - Moderate Pressure

Post by milesmiles » Tue Jun 24, 2014 6:41 am

Who doesn't need 130mph in their life...I do
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Re: Front Brake Vibration - Moderate Pressure

Post by Striple » Tue Jun 24, 2014 7:12 am

Yeah, you can definitely bed the pads at lower speeds. The key is to gradually increase brake pressure.
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Re: Front Brake Vibration - Moderate Pressure

Post by fireblade » Tue Jun 24, 2014 9:23 am

There really is no need to do any surface treatment. The most important thing is to properly bed the new pads in on the rotors. Anytime new brake components are installed the mating parts do not mate very well, as you can imagine. So, the braking occurs on a very small amount of the available area of the pad/rotor surface. Hard braking at this point can easily overheat the brake contact patch (the relatively small, local areas of contact) and permanently damage or degrade the brake capability. You want to avoid severe braking with new parts until they are bedded in. The old wives tale of going out and doing some "panic" stops from 80 is NOT what is recommended to bed new brake parts. Find a deserted stretch of road and accelerate to 35 or 40 and then do a firm, rapid stop. Don't stop completely and sit with the pads stationary on the rotor, just brake hard to about a 95% stop, roll out and re-accelerate to 35-40. Stop again the same way. Do 10-12 hard stops from 35-40 like this. Then ride off and ride at speed to cool everything down. When cool, repeat the 10-12 hard stop routine. Cool down again. Consider the brakes "burnished" and do what you want with them. It is important to bed them like this to mate the parts together, optimize the contact patch between the pads and rotors, get the parts up to high temp to clean off any volatiles from the manufacturing or handling process and to transfer a bit of the pad material to the rotor surface for optimum friction characteristics. The stops should be hard but not panic and not hard enough to activate the ABS. Just a good, firm, hard stop to generate heat in the brakes. Braking from only 35-40 will minimize the amount of heat to prevent damage but you should be able to get them pretty warm and some smoke is usually evident after the 10th or 12th stop.

You don't want to come to a hard stop each time during the bed-in and sit with the pads held against the rotors as that will cause non-uniform pad material transfer to the rotors and potential heat damage, since the hot pad will insulate the hot rotor in that spot and uneven cooling will result. Just roll out the stop each time and accelerate back to speed for the next one.

35-40 mph stops are pretty conservative for a motorcycle. I use 50 mph stops to bed my motorcycle brakes since I pretty much know what sort of heat and smoke and smell I am expecting. Try 35-40 to get the hang of the schedule and then step up the speed a bit if the brakes don't seem to get very hot after 8 or 10 stops and/or just do 15 or 16 stops instead at 35-40 to build more temp. You want to build the temp in a controlled fashion without overheating anything with a single hard stop from higher speeds.

This sort of procedure is not the sort of thing you want to tell "everyone" to do for obvious reasons regarding liability and traffic laws. So, be careful and do it in a safe, controlled space. That is why you don't get this story very often and why vehicles come with a "recommended break-in schedule". It isn't for the engine nearly as much as for the brakes. If you take off slow with a sense of taking it easy to "break in" the engine then you will inherently take it easy on the brakes so it is sort of an underhanded way of mandating a customer brake burnish schedule.
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Re: Front Brake Vibration - Moderate Pressure

Post by milesmiles » Tue Jun 24, 2014 9:29 am

tl:dr
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Re: Front Brake Vibration - Moderate Pressure

Post by Rhino » Tue Jun 24, 2014 9:44 am

milesmiles wrote:tl:dr
And this is why you fail so often.

That's freakin' fantastic info.

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Front Brake Vibration - Moderate Pressure

Post by milesmiles » Tue Jun 24, 2014 10:06 am

Fail. When do I do that?

Tl:dr just means shorten it a bit not necessarily I didn't read it. Geez, do you even reddit bro?
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Re: Front Brake Vibration - Moderate Pressure

Post by fireblade » Tue Jun 24, 2014 10:17 am

No, bad miles, not going to shorten it because you're lazy. good information there.
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Re: Front Brake Vibration - Moderate Pressure

Post by milesmiles » Tue Jun 24, 2014 10:57 am

Well...
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Re: Front Brake Vibration - Moderate Pressure

Post by Rhino » Tue Jun 24, 2014 11:16 am

milesmiles wrote:Fail. When do I do that?

Tl:dr just means shorten it a bit not necessarily I didn't read it. Geez, do you even reddit bro?
You failed *right there*.

tl;dr means "too long; didn't read". It doesn't mean "make it shorter", it means "I couldn't be bothered to read that."

Geez, do you even internet bro?

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Re: Front Brake Vibration - Moderate Pressure

Post by DarcShadow » Tue Jun 24, 2014 11:20 am

milesmiles wrote:Fail. When do I do that?

Tl:dr just means shorten it a bit not necessarily I didn't read it. Geez, do you even reddit bro?
I think if you check tldr DOES mean you didn't read it, that's what the D and the R stand for. And what does the new web site Reddit have to do with any of this?
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Re: Front Brake Vibration - Moderate Pressure

Post by milesmiles » Tue Jun 24, 2014 11:41 am

I know what it means! On reddit at the end of a long story they usually put a tl:dr version.
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Re: Front Brake Vibration - Moderate Pressure

Post by Rhino » Tue Jun 24, 2014 1:32 pm

That's because your typical reddit reader is a complete moron who can't grasp complex concepts.

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Re: Front Brake Vibration - Moderate Pressure

Post by dufremle » Tue Jun 24, 2014 1:53 pm

Rhino wrote:That's because your typical reddit reader is a complete moron who can't grasp complex concepts.
AKA Miles.
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Re: Front Brake Vibration - Moderate Pressure

Post by milesmiles » Tue Jun 24, 2014 2:01 pm

Holy shit y'all really are assholes.
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Re: Front Brake Vibration - Moderate Pressure

Post by Striple » Tue Jun 24, 2014 3:11 pm

milesmiles wrote:Holy shit, y'all really are assholes.
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Re: Front Brake Vibration - Moderate Pressure

Post by fixxervi6 » Tue Jun 24, 2014 3:14 pm

My question is still out there, is the pulsing felt in the brake handle, is it pushing back on you?
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Re: Front Brake Vibration - Moderate Pressure

Post by JTChiTown » Tue Jun 24, 2014 9:23 pm

Ha! So I guess this is what I asked for! With the weather, I probably won't be able to bleed and bed the brakes until after the 4th. Taking the glorious cross country road trip. I'll report back though once I get the time.

I'm an auto tech by trade, and bedding in the brakes isn't a new concept for me. We have to do it to every new unit, and it's crucial on some models.

To answer your question fixxer, my hands aren't sensitive enough yet to be totally confident in my ability to answer your question. It definitely affects the deceleration of the bike, but it was strong enough that I can't say if it was also pulsing the lever. My impression that it wasnt, and that it was only affecting deceleration rates.

Thanks for all the suggestions!
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Re: Front Brake Vibration - Moderate Pressure

Post by JTChiTown » Wed Jul 09, 2014 12:22 pm

So an update:

Bled the front brakes. The fluid that was in there was a little darker than normal, and I didn't get more than one little bubble out of the system. I flushed out all the old fluid as well, since I'm not familiar with the history.

Did the bedding process last night after the bleeding - no real impact on the vibration.

I'll pull the front rotors tonight and sand them smooth and try again with fresh surfaces and report back.

Really just trying to avoid the cost of buying new rotors if I can help it.
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