Friday, 1 Nov 2024 [26,074 miles]
I’m still over 1K miles short of my next service. That said, the brakes on this bike have never been measured and flushed. They don’t feel as I think they should. The brake fluid I ordered arrived so there’s no reason to wait.
I started by measuring brake rotor thickness. The minimum is 4.5mm according to the service manual. Both of my front rotors are over 5 mm thick, the left averaging 5.05mm and the right averaging 5.10mm. Wear seems even. The rear was a different story.
The wear on the rear is more on the outside edge of the rotor than the inside edge by about 0.17mm. The outside measures about 4.6mm and the inside measure averages 4.77mm. A new rotor might be needed about the time the rear brake pads are gone.
Rear pads
Rear caliper
I pulled and measured the rear brake pads. The minimum is 1mm and both pads had between 2.5mm and 3mm of friction material left. Both seemed to be wearing equally.
Saturday, 2 Nov 2024 [26,064 miles]
Nice afternoon with no household chores left needing to do. Think I’ll finish the brake bleed on the KTM 790.
Flush tools
I got out my flush-the-brakes tools: vacuum pump, syringe, screwdrivers, fresh brake fluid, etc. The rear uses an 9 mm wrench, the front an 8 mm. The handle of my offset 8 mm is too long to let me swing it enough to open the bleed nipple more than about an 8th of a turn. I used a small 8 mm open end wrench, instead. Not shown is the brake fluid tester. I tested the fluid in the rear because I was curious. The moisture level was above 3%, i.e. bad. I didn’t bother testing the front.
Clean
Kind of dark
New brake fluid
I cleaned the caliper and around the bleed nipple before attaching the vacuum pump. Ditto around the rear reservoir before opening the cap. I used the syringe to suck out the old fluid. I put too holes in the seal of the new brake fluid to make pouring easy.
Ready to flush front
After flushing the rear I moved the vacuum pump to the left front and prepared the reservoir for new fluid. Flushed the left side, then moved to the right. Filled the reservoir several times during the flush and never let it get empty. After completing both sides I made sure the reservoir was full and put the top back on.
After flushing I remembered to check the condition of the brake pads.
Can’t see wear indicators
Now can see wear indicators
About 4 mm pad depth
I tried using my phone camera to see the wear indicators. Nope. The were easy to see after removing the pad retaining pins and spring. As long as I’d gone that far I removed the pads to measure the friction material. Both are over 4 mm thick. Minimum in 1 mm. Got lots of pad wear left.
I find it interesting that the rear is worn so much more than the front given that I use the front brakes so much more than the rear. I’m wonder if that is due to the potential failure that caused a rear brake recall several years ago. I read several reports of dragging rear brakes. Maybe mine were slightly dragging and I didn’t notice.