Brake drag, front end alignment "how to" - Page 2 - Suzuki GSX-R Motorcycle Forums Gixxer.com

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post #21 of 54 (permalink) Old 03-21-2014, 05:12 PM Thread Starter
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Re: Brake drag, front end alignment "how to"

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Originally Posted by sir stackalot View Post
I pump the front end without the calipers on.

If you have the calipers on and brakes applied, the brake pressure will not allow the fork leg to align on the axle.
Incorrect. Ive tested both ways and there is less brake drag installing the calipers first.

In all reality the step that "could" be skipped is the dropping and bouncing of the front IF you are using a pin lift stand as you should be and IF the fork is aligned vertically properly the fork aligns on the axle by itself and the brake pistons grabbing the disk without the bouncing of the front

But in case those two ifs are not the case then bouncing helps make sure.



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post #22 of 54 (permalink) Old 03-21-2014, 05:23 PM
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Re: Brake drag, front end alignment "how to"

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Incorrect. Ive tested both ways and there is less brake drag installing the calipers first.
agreed, there will be less brake drag using the way you say, because the brake pressure will align the fork leg/caliper assembly to the brake disc.

but imo pumping with no brake influence will allow the fork to align on the axle in it's more "natural" place ,giving less stiction in the fork, and if there is brake drag, this will generally drop to an acceptable amount after a couple rides

Last edited by sir stackalot; 03-21-2014 at 05:26 PM.
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post #23 of 54 (permalink) Old 03-21-2014, 05:30 PM Thread Starter
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Re: Brake drag, front end alignment "how to"

Unless you have worn fork bushings or a bent/warped/dished disk (which is another problem all together and this write up assumes your bike is in good working order) I disagree. Again. The brake pistons can float (again assuming they are clean and in good repair). Any side pressure put against them would compress the piston... not move/flex the fork against its slider bushings.

Feel free to disagree all you wish. Do it your way if you wish. I used to out calipers on last too, until a respected AMA tech suggested doing them first. I then objectively tested the difference... and doing it the way outlined has the best outcome in every way.

For a street ridden bike it is likely moot anyway though.





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post #24 of 54 (permalink) Old 03-21-2014, 07:01 PM
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Re: Brake drag, front end alignment "how to"

There are a number of different ways. I leave mine on the stand and tap the knuckle with a nylon hammer. That shock is just as good as bouncing the front. Most brake drag comes from dirty pistons and not alignment.
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post #25 of 54 (permalink) Old 03-21-2014, 07:53 PM Thread Starter
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Re: Brake drag, front end alignment "how to"

I've found that actually a substantially large portion of brake drag is from alignment actually. There have been numerous times where I've had to change tires quickly and as such did so on a paddock stand and noticed far more drag than I would with a pin lift stand, caused by the forks not aligning when holding the weight of the bike without the axle in place.

In those instances I've come back in, noticed the drag putting the warmers on, and alleviated it by re setting the front end on a pin stand.



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post #26 of 54 (permalink) Old 03-22-2014, 07:40 AM
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Re: Brake drag, front end alignment "how to"

If you don't install something right, of course it's going to have ill effects elsewhere. I wouldn't call that brake drag, I'd call that not installing the front wheel correctly.

It's their bike, but I just cringe when I observe the way some people working on their bikes. Just having tools doesn't make you a mechanic. I don't know how many bikes I've seen that were just hacked on before. Installing a front wheel on a motorcycle really does take a bit of knowledge. Taking the stress out of the system before clamping it down is important for more than just brake drag.


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post #27 of 54 (permalink) Old 03-22-2014, 08:15 AM Thread Starter
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Re: Brake drag, front end alignment "how to"

MOST people will argue that if you have it on a paddock stand when you take it apart to change front tire and don't move it when putting it back nothing changes. I've found that to be wrong.

So what I am saying is most brake drag experienced by most people is likely due to alignment as much or more than caliper crud.
I'd say most people don't do either... clean the calipers enough nor align properly, hence why I took the time to write both up.



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post #28 of 54 (permalink) Old 04-28-2014, 05:10 PM
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Re: Brake drag, front end alignment "how to"

Hmm. This might cure my brake drag problems. I performed a full caliper cleaning but still have horrible wheel spin and brake drag. The bike went through 4 offs last year () so Im sure this is long overdue anyways.
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post #29 of 54 (permalink) Old 04-28-2014, 05:26 PM Thread Starter
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Re: Brake drag, front end alignment "how to"

If you have not had your chassis checked for straight you probably should as well



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post #30 of 54 (permalink) Old 05-26-2014, 05:10 AM
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Re: Brake drag, front end alignment "how to"

The SRAD doesn't have any "Hex" on the drivers left fork collar. That is, a collar like this:

So it seems that they are just like the Y's and K1's...I think first gen Busas are like that too.

Now, I think I have a brake drag problem...just installed some nice calipers, which are clean, when trought Moto_Joe bleeding technique (which worked very well with this calipers and MC), and gone through the alignment process as described in this thread, but couldn't get better than this:



Well, it did got better when hot, after a ride, but gone back to this soon after.

Now, the only step I'm not 100% confident is the vertical alignament. I rotated the axle, while moving one fork leg up and down, in order to find the spot with less resistance. But at some point there is more resistance at a particular angle of rotation.
Does this alignament need to be that precise? When the wheel is on the ground, doesn't the forks level them selfs? What if I tighten the right pinch bolts with the wheel in the ground?
Is there any other method, fool's proof, than one can suggest me to align it verticaly?

Last edited by tmp; 05-26-2014 at 05:34 AM.
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post #31 of 54 (permalink) Old 05-29-2014, 09:20 AM
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Re: Brake drag, front end alignment "how to"

Been reading, and it seems that more than one wheel revolution, like in my video, is considered "normal"...is that true?
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post #32 of 54 (permalink) Old 05-29-2014, 10:39 AM
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Re: Brake drag, front end alignment "how to"

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post #33 of 54 (permalink) Old 05-29-2014, 10:57 AM Thread Starter
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Re: Brake drag, front end alignment "how to"

That video isn't bad. I've seen better and I've seen worse. Does sound a bit noisy but can't pinpoint the noise. Does it get significantly better with calipers off or just a little better? Almost sounds like wheel bearings but likely is video quality



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post #34 of 54 (permalink) Old 05-29-2014, 11:15 AM
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Re: Brake drag, front end alignment "how to"

Thanks for your reply!
The noise comes from the pads rubbing the rotors. Without the calipers, the wheel spins nicely without any noises. When riding the bike at slow speed, in the garage for example, the noise can be heard too.
BTW, while hot, after a ride, it seemed a little better...

Kinda lost in what to check next...
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post #35 of 54 (permalink) Old 05-29-2014, 11:47 AM Thread Starter
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Re: Brake drag, front end alignment "how to"

You said calipers are clean. Did you clean them per the third how to I have ?



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post #36 of 54 (permalink) Old 05-29-2014, 12:03 PM
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Re: Brake drag, front end alignment "how to"

No...first, at that time I wasn't aware of your how to's and I got them out of the bike, neither can find the "simple green" in Portugal...
But I took it to a friend who builds custom bikes and got very experienced cleaning calliper's in UK (due to salty roads), and we disassembled them completely, took the pistons out with those rubber end plyers and clean them one by one.
They didn't need that much of a cleaning, we could see that they were very low mileage and perfect shape inside, bore and all!
On assembly, we used a bit of red rubber grease on them.

In the end the pistons slided with only one finger push...
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post #37 of 54 (permalink) Old 05-29-2014, 12:22 PM Thread Starter
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Re: Brake drag, front end alignment "how to"

Simple green is just a biodegradable degreaser. I'm sure there is something similar there.

I also spray the pistons with Teflon lube. Seems to help a lot.



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post #38 of 54 (permalink) Old 05-30-2014, 05:49 AM
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Re: Brake drag, front end alignment "how to"

Maybe the Teflon lube would solve the issue as it would help things sliding better, but yesterday I found the real culprit.
I've spoke that friend of mine that worked as a mechanic in UK, and he pointed out that sometimes the callipers aren't able to center the pistons properly.
What happens is when we are pumping the brakes, one side of the pads get to the disc first (ex: the outer pads), then all the positive and negative pressure will work on the other side (inner pads). So, that way, the inner pads are stealing the retract force from the outer pads, not letting them release the disc properly, and it will keep that way as the inner are free and the outer are stuck against the disc.

Now, the solution is simply trying to equalize the distance between pads and discs. I just pushed the rubbing pad back while pressing the brake lever, and now I get two full revolutions at the wheel.
The next time I may fit a thick piece of paper under all pads, press the lever until they meet the paper so that all them will be at the same distance of the disc. Then remove the paper and hopefully with one lever press, all the pads will meet the disc.

Does that make sense?
Well, for me this worked quite well!
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post #39 of 54 (permalink) Old 05-30-2014, 06:09 AM Thread Starter
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Re: Brake drag, front end alignment "how to"

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Originally Posted by tmp View Post
Maybe the Teflon lube would solve the issue as it would help things sliding better, but yesterday I found the real culprit.

I've spoke that friend of mine that worked as a mechanic in UK, and he pointed out that sometimes the callipers aren't able to center the pistons properly.

What happens is when we are pumping the brakes, one side of the pads get to the disc first (ex: the outer pads), then all the positive and negative pressure will work on the other side (inner pads). So, that way, the inner pads are stealing the retract force from the outer pads, not letting them release the disc properly, and it will keep that way as the inner are free and the outer are stuck against the disc.



Now, the solution is simply trying to equalize the distance between pads and discs. I just pushed the rubbing pad back while pressing the brake lever, and now I get two full revolutions at the wheel.

The next time I may fit a thick piece of paper under all pads, press the lever until they meet the paper so that all them will be at the same distance of the disc. Then remove the paper and hopefully with one lever press, all the pads will meet the disc.



Does that make sense?

Well, for me this worked quite well!

Yes. And because of that I don't just pump the pistons out all at once. What I do is rotate the tire as I lightly tap the lever to bring the pistons back out slowly and more evenly.

But the Teflon frees them up enough that they more easily are retracted too



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post #40 of 54 (permalink) Old 05-30-2014, 08:06 AM
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Re: Brake drag, front end alignment "how to"

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For racers... the internal fork length variance is why geometry needs to be checked from axle center to lower triple with no preload, as apposed to using the fork caps at the top triple.
Pretty much a myth that's so simple people believe it. It is true that the internal fork length variance exists. But here's the problem. If your legs are 5mm off, the pressure difference between the two sides will be only 5mm/spring rate. Not much at all. The longer will easily match up with the shorter and the pressure on the axle will me marginal at best.

Matching the forks at top-out (full extension) really doesn't do a damn thing. Where you want the forks to match is at bottom-out (full compression). At bottom-out, if one side is different from the other the pressure differential can be extreme causing one leg to compress farther than possible for the other. This can cause deflection of the front wheel and undue fatigue to the front axle system.

The really good suspension guys assemble a leg with no spring, then fully compress it and note the length. Then when assembling a fork, they note the difference and adjust the cap height to make sure the bottom out length to lower crown is identical.


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