Feels like trying to stop a freight train... - Yamaha R6 Forum: YZF-R6 Forums
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post #1 of 29 (permalink) Old 03-13-2013, 08:43 PM Thread Starter
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Feels like trying to stop a freight train...

I am looking for thoughts about a issue I am having with my 2007 R6. I have done 2 TDs so far and love the bike. It does everything better than my 675, except stop! It literally feels like the bike weighs twice as much as it does BC i'm having to use all my hand/forearm strength to squeeze the lever to get her slowed. This cuases me to have to brake earlier than I'd like. I am litterally distracted by how much effort it take on the brake lever. I put a Brembro MC on my Daytona (19x18 as I recall) and it stops on a dime. This bike already had a Brembro MC-same size I beleive. Its been on there for a while, I wonder does it need to be refreshed/rebuilt-is that a option? My much wiser mechanic friend said I need a different size MC?? Like 19X16? I dont honestly understand the difference other than it relates to piston size I guess??
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PS the pads are good quality with lots of life and the brake fluids is so fresh and so clean
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so I dont think that's the problem. I guess I could bleed it again
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Any help would be appreciated

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post #2 of 29 (permalink) Old 03-13-2013, 08:48 PM
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Should have mentioned it when we were out there last weekend brother. I would have taken it for a quick lap and seen what the feel was, then we could have trouble shot it in the pits. With a Brembo master you should have no issues. Which leads me to think it's air in the lines, or you're just used to a diff brand of pads that had a more initial, aggressive bite. My HH pads suit me quite well, but don't bite hard at all initially. Every rider is different though.

What pads were you running in the Daytona, and what are in your bike now? I'd ask Brian and see what he says... Could just be air in the lines though if they feel squishy and non responsive...


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post #3 of 29 (permalink) Old 03-13-2013, 10:33 PM
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Re: Feels like trying to stop a freight train...

You could try bench bleeding the brake system. Basically take it off the bike, put something between the pads, and let the calipers hang so the lines are totally straight so make sure you don't have any bubbles trapped in a bend somewhere - and bleed them that way.

When I went from my '03 street bike to my '05 track bike I was frustrated because it felt like it didn't stop as hard and didn't have great initial feel, despite having bigger brakes and aftermarket rotors. Dunno what it was about the '03, but I somehow managed to get a magical, perfect bleed on the system and had absolutely zero slack on the lever. Feel was soooo good. Every other bike I've been on has at least a little bit of initial wiggle before the brakes start to grab.
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post #4 of 29 (permalink) Old 03-14-2013, 06:33 AM
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Re: Feels like trying to stop a freight train...

Bleeding won't reduce the effort. Air in the system will give a lever that pumps up or is inconsistent in stroke.

The pads may not be to your liking or are glazed and not working properly. You may be able to clean up the discs with emery cloth and sand the pads.

Or the piston in the Master Cylinder is too large and requiring too much effort to build pressure.
A larger piston requires less travel and more effort, a smaller piston requires longer travel and less effort.

Last edited by narve00; 03-14-2013 at 06:36 AM.
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post #5 of 29 (permalink) Old 03-14-2013, 07:30 AM
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Re: Feels like trying to stop a freight train...

the oem brembo should work fine, but it is a little more progressive feel as your friend told you vs. the 19x18. The oem mc is used by MANY racers.. (self included) i love the oem brembo.
post a photo above the handlebar, showing the distance from the grip to the master cyl. My suggestion is to loosen the master cyl perch bolt, and slide it AWAY from the grip a little further. This gives you more LEVERAGE on the brake lever. You can adjust the distance to the bar for comfort.

Yes.. as someone said, your brake pads may have tons of material, that does not mean they are working. if they are stock, they are not going to work as well on track. OEM pads are designed to be able to heat up fast enough to be safe for street use. They are "ok" for a slower track day rider, but not gonna do the job as the pace pics up.
Get a new set of EBC extreme pro pads. I would start with the EPFA if you want a good but still somewhat progressive pad (it's what i use) or jump right to the GPFA for some serious bite.

as someone else mentioned, if the lever is firm.. and not coming back to the bar, it likely does not have air in the line. If it's been more than a year since you bleed new fluid, it's way over due.

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post #6 of 29 (permalink) Old 03-14-2013, 08:01 AM
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Re: Feels like trying to stop a freight train...

Clean the slide and make sure the pads are not binding. They should be easy to move in and out the caliper.
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post #7 of 29 (permalink) Old 03-14-2013, 10:26 AM Thread Starter
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Re: Feels like trying to stop a freight train...

Quote:
Originally Posted by R-Silaxin View Post
Should have mentioned it when we were out there last weekend brother. I would have taken it for a quick lap and seen what the feel was, then we could have trouble shot it in the pits. With a Brembo master you should have no issues. Which leads me to think it's air in the lines, or you're just used to a diff brand of pads that had a more initial, aggressive bite. My HH pads suit me quite well, but don't bite hard at all initially. Every rider is different though.

What pads were you running in the Daytona, and what are in your bike now? I'd ask Brian and see what he says... Could just be air in the lines though if they feel squishy and non responsive...


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Quote:
Originally Posted by narve00 View Post
Bleeding won't reduce the effort. Air in the system will give a lever that pumps up or is inconsistent in stroke.

The pads may not be to your liking or are glazed and not working properly. You may be able to clean up the discs with emery cloth and sand the pads.

Or the piston in the Master Cylinder is too large and requiring too much effort to build pressure.
A larger piston requires less travel and more effort, a smaller piston requires longer travel and less effort.
Quote:
Originally Posted by MELK-MAN View Post
the oem brembo should work fine, but it is a little more progressive feel as your friend told you vs. the 19x18. The oem mc is used by MANY racers.. (self included) i love the oem brembo.
post a photo above the handlebar, showing the distance from the grip to the master cyl. My suggestion is to loosen the master cyl perch bolt, and slide it AWAY from the grip a little further. This gives you more LEVERAGE on the brake lever. You can adjust the distance to the bar for comfort.

Yes.. as someone said, your brake pads may have tons of material, that does not mean they are working. if they are stock, they are not going to work as well on track. OEM pads are designed to be able to heat up fast enough to be safe for street use. They are "ok" for a slower track day rider, but not gonna do the job as the pace pics up.
Get a new set of EBC extreme pro pads. I would start with the EPFA if you want a good but still somewhat progressive pad (it's what i use) or jump right to the GPFA for some serious bite.

as someone else mentioned, if the lever is firm.. and not coming back to the bar, it likely does not have air in the line. If it's been more than a year since you bleed new fluid, it's way over due.
I will re-bleed the brakes just to be safe but yeah as mentioned I dont think that is the issue B/C the lever isnt "squishy" or moves all the way to the bar, it just takes a lot of effort to stop. The Daytona I am running Galfer pads, I'll have to double check the what model but it's one of the more aggresive but not full sintered pads. I will probably get a new set of these for the R6 just so I know my pads are good. I am still curious to have someone explain to me the difference on piston size ect with the different MC sizes.

I'll take some pics tonight and post them up just for reference.

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post #8 of 29 (permalink) Old 03-14-2013, 10:35 AM
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Re: Feels like trying to stop a freight train...

It could very well just be that you're conditioned to expect A to happen, from bike A(the Daytona) on bike B (the R6). Maybe your learning curve with this bike will take some getting used to in the end. I will say, if you found a brake pad that you liked, which worked for you in your Daytona, why not buy the same set of pads for the R6. In retrospect the R6 is a bit heavier, and I'm sure feels "bulkier" then the Daytona. May just take some getting used to, once you troubleshoot it. The R6 could very well be in perfect working order, and you're just 'used to' the Daytona. Best of luck Leif. If you've got questions next time out at the track, I'll take it for a spin and maybe give you some peace of mind if the case just happens to be it's a bigger bike, and will take some getting used to on your part...


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post #9 of 29 (permalink) Old 03-14-2013, 10:43 AM Thread Starter
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Re: Feels like trying to stop a freight train...

Sounds good Adam
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post #10 of 29 (permalink) Old 03-14-2013, 11:46 AM Thread Starter
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Re: Feels like trying to stop a freight train...

Here is the copy of a email from my mechanic-basically I have him do things I'm too scared to do myself including brakes and electrical. Obviously I respect his opinion and though there was some good info here, feel free to add your opinion on what he says:

"Anyway, in regards to the brakes on the R6...

My belief is that the 19x18 brembo is sized too large for the relatively small-diameter pistons found in the R6 calipers. This minimizes the mechanical advantage, which means whatever force you input at the lever will not be magnified very much at the calipers. Conversely, when you either decrease the master cylinder piston size, OR increase the piston diameter / number of pistons, you increase mechanical advantage, which means you magnify the input at the lever more... meaning less pressure to achieve the same braking force. The trade-off is in lever travel.... the more your braking force is magnified, the more lever travel will be required to move the pistons out the same amount.

The R6 / R1s have always had awesome calipers. But their awesomeness comes from their internal stiffness, and part of that stiffness itself comes from the very small piston diameters they use (smaller than any other sportbike I'm aware of). Most people don't take this into account when purchasing aftermarket components. IMO, every time someone slaps an aftermarket brembo on a bike with R6 calipers, they **** it up.

I wanted to pull up that spreadsheet I mentioned - where I have the dimensions of just about every master cylinder / caliper combo imaginable along with their calculated leverage ratios. Unfortunately I had to wipe my ssytem last week due to a virus, & that file is gone. Regardless, I feel you'd be much better off with a smaller master cylinder (smaller as in smaller piston size) in order to magnify your input force. That alone may or may not solve all your braking problems, but I'm sure it would help.

Have you ridden a stock R6? They have pretty nice Brembo MCs stock that are sized appropriately for the calipers. Granted, they're cast MCs, not forged, so they're not the best, but the leverage ratio makes more of a difference than the material stiffness. Even if you'd rather go with an aftermarket MC, getting on a stock R6 would give you an idea of what the brakes will feel like with something sized appropriately. Going off memory, the stock MC is either a 14 or 16mm piston.

BTW - In case you're not familiar with master cylinder sizing, the first number is the piston diameter, and the second number is the distance from the pivot point to point where the lever exerts pressure on the piston rod. Going up in piston diameter will decrease lever travel but increase the amount of pressure required to get X-amount of braking force (you're moving more fluid for each unit of lever travel). Going up on the 2nd number does the same thing. So a 19x18 will have more lever travel than a 19x20, but will require more force at the lever to get the same amount of force at the caliper. Likewise, a 16x18 will have more lever travel than a 19x18, but will require more force at the lever as well."

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