2010 Ultra Classic

With about 160,000 miles on my bike, it's time to change out the brake rotors. I bought a new rear rotor to take care of that one first. When I got home to compare them I noticed a difference between the rear rotor that is on my bike and the one I had purchased. The part number on the new rotor is HD41810-08B. The part number for the rotor that is on the bike is HD41810-08A. I'm hoping that the P/N difference is just an upgrade.

My question is...
What is the small circular attachment on the older rotor that is not present on the new rotor? See pictures... The pictures are of the new rear rotor and the older front rotor just because getting the picture was easier. That circular attachment is on the older rear rotor too.

new rotor

older rotor
Any help? Thanks!!

 

 

side note: when you go to take the rotor bolts out, chances are they have RED locktite on them

they will be a b*tch to get out.

If you have a soldering iron, put it on the head of the rotor bold tor a few minutes to release the locktite before you try to remove

 

B means its the 2nd supercession, and probably design change (although it's been done simply because of packaging changes before). Hopefully you bought new rotor bolts too since they're one time use only. I've seen a few complaints of the floating rotors rattling or clunking, which is why they probably went back to the rigid design.

 

Further to 95th's reply, the original version of your rear rotor didn't have a letter, so your 'B' is the third version or second supercession (not sure how to spell that!). It may be a change of supplier, or a minor upgrade of some sort, but doesn't affect our use of it.

As for that single pin on the 'semi-floating' rotors, we've discussed it endlessly, but haven't come up with a good explanation for it yet! I prefer proper fully floating types and currently have EBC rotors front and rear.

 

Be sure and replace the bolts when you install the new rotor. And yes, the old one is semi-floating and the one you bought is solid. You probably won't notice any difference but the semi-floating rotor is easier on caliper and pads. Full floating is the best but the solid one will get the job done. A lot depends on your riding style. If you use the rear brakes more than the front the solid rotor is more prone to warp than a floating rotor would be.

 

I'm not an expert on HD brakes but I've changed a lot of brakes on my sportbikes over the years. Don't compare front and rear rotors. The rear rotors typically are fixed not floating (that's why they are solid and the front has that button). You should not expect them to look the same at all so don't sweat that. Does the bike have linked brakes at all? It might be worth it to return that rotor for the same one just to air on the side of caution. As mentioned, it will get the job done but it just won't last as long.

The reason for a rotor being either semi floating (connected in all but one area) or free floating (the rotor and hub are not connected and the rotor blade stays on with those buttons) is to allow for expansion as the rotor gets hot from braking.

Here's a link from EBC that does a good job of explaining about floating rotors.

​​​​​​https://ebcbrakes.com/product/floating-mc-rotors/

 

Thanks for the replies, fellas. I completely forgot about the 'semi-floating' rotors. I knew I could get past the weird answers I was getting from two different dealers. It seemed like I wasn't going to get the right answer until I handed over my credit card to buy "the correct one".

R-

 

 

yea what he said and 160k wow