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Discussion Starter #1
I recently upgraded to a 21" 18" wheel set for my 2015 Shark. new rotors, abs bearings, etc. I am now getting a brake pulsation when stopping at low speeds. Being that I have the linked braking system I can't tell whether its from the front or rear. I've bleed the brakes, and the rotors measure perfect. Has anyone had this issue or have any ideas on how the get rid of the pulsation?
thanks in advance.
 

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Your ABS operates via speed sensors on the axle vs magnets in the bearings. When the circumference of the tire changes, it will send a false speed reading to the ABS computer. The ratio the computer sees as "correct" is based on the OEM tire sizes. When the tire size is changed, and the ratio is no longer the same, the ABS system reacts when pressure is applied to the brakes to force them to travel at the same speed. If the ratio is modified- without correction- it will "pulse" the calipers on whichever wheel is travelling too fast.

This seems like a dangerous situation. YOUR tire "upgrade", without proper calibration might only serve to make your bike look really cool right before you wreck it. Because you've modified the way the tires vs. brakes are *supposed* to perform, it may cause brake lockup due to the incorrect speed sensor ratio.

I could be completely off-base. But basic physics says that's where the problem lies.
 
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I have a stock set up. So my issues might be caused from a different situation. Thx


Sounds like YOUR diagnosis is correct. Do the forks "dive" as the brakes pulse? If so, that DEFINITELY sounds like warped rotors.
 

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My understanding is when the abs brakes are bleed it requires a dealer only machine to do it correctly. Some brakes completely lock up. I could be wrong.
 

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My Wheel vibration is felt when front brakes are applied.

Fresh glide might need that device that's been mentioned for adding a 21" wheel to a RGS.


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A way to find out which one it is Qhog, pull one side caliper off, put an old brake pad between the brake pad on the caliper that you took off and zip tie it in there and zip tie it to your crash bar. Think ride the bike on a test ride and see if it still does it. IF it does, that's the warped brake rotor, if not, put it back on and do the same to the other side. Easy way to find out which it is. IF you don't have a spare pad, use something you can zip in there to prevent the caliper from closing up all the way. I think you get what I'm talking about. Good luck finding it.
 

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Discussion Starter #10
Your ABS operates via speed sensors on the axle vs magnets in the bearings. When the circumference of the tire changes, it will send a false speed reading to the ABS computer. The ratio the computer sees as "correct" is based on the OEM tire sizes. When the tire size is changed, and the ratio is no longer the same, the ABS system reacts when pressure is applied to the brakes to force them to travel at the same speed. If the ratio is modified- without correction- it will "pulse" the calipers on whichever wheel is travelling too fast.

This seems like a dangerous situation. YOUR tire "upgrade", without proper calibration might only serve to make your bike look really cool right before you wreck it. Because you've modified the way the tires vs. brakes are *supposed* to perform, it may cause brake lockup due to the incorrect speed sensor ratio.

I could be completely off-base. But basic physics says that's where the problem lies.
I do have the correct abs bearings for the wheel and tire size upgrade. If it was incorrect the ABS light should come on correct?
 

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I do have the correct abs bearings for the wheel and tire size upgrade. If it was incorrect the ABS light should come on correct?
NO, the ECM is calculating how many times the wheel turns at a given speed and relates that to the abs for proper applications to the brakes. Now that you have different wheel size, these calculations are off and is messing up the info sent to the abs module. I know some tuners have the means to correct this. I'm sure harley can re-flash to correct your system.
 

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Discussion Starter #12
NO, the ECM is calculating how many times the wheel turns at a given speed and relates that to the abs for proper applications to the brakes. Now that you have different wheel size, these calculations are off and is messing up the calculations. I know some tuners have the means to correct this. I'm sure harley can re-flash to correct your system.
Thanks. I guess I'll have to take it to the Stealer.
 

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Smarty, I do have stock chrome rotors on. I've had warp rotors before and this feels like the same. But thanks for the that trouble shooting tip.


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Smarty, I do have stock chrome rotors on. I've had warp rotors before and this feels like the same. But thanks for the that trouble shooting tip.


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The only reason I said that about the chrome rotors is, when I changed mine out a couple of months ago, as it wears down the chrome on braking surface, I've noticed a not pulsing feeling but rough almost like the surface isn't smooth now. I'm going to remove the wheel and use a side grinder with a sanding wheel and knock the surface off the pads and then give the surface on the rotor a light buffing too to see if that helps.
 

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That's what I'm feeling. It like riding over those carved ridges on the side of the road that are used to wake you up if you drift out of line. This same thing happens to me with my 12 RG stock rotors.


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That's what I'm feeling. It like riding over those curved ridges on the side of the road that are used to wake you up if you drift out of line. This same thing happens to me with my 12 RG stock rotors.


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I've read somewhere about sanding the pads and the rotors to fix this. This is the first time it has happened to any of my bikes until now.
 
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