Why Do My Honda Motorcycle Brakes Keep Bottoming Out?

If the rear brakes on your Honda VTX1800 bottom out each year after you take the bike out of winter storage, what could be the problem? Maybe air got into the braking system.

Partzilla’s Honda motorcycle expert John Talley hosts live Q&A sessions on our YouTube channel every Friday at 3pm Eastern. In this session, John was asked why the rear brakes on a 2007 Honda VTX1800 bottom out each and every time the motorcycle is taken out of winter storage, requiring a brake bleed each time to solve the problem.

Honda VTX 1800 rear brake master cylinder

Honda VTX1800 Rear Brakes Bottoming Out Q&A

I have an 07 Honda VTX1800 and during the winter months it sits in the garage. When the season starts and I go to get on the bike, the rear brake bottoms out. Only when I bleed them they are good. Literally every year I have to do this at the start of the season. No leaks that I see ever. Why would that happen? …

John Talley: Well, she must be getting some air in there somehow or another. Because if there’s not a puddle on your floor, that means the brake fluid isn’t going out and it doesn’t evaporate, not to my knowledge. So it must be letting air get in. I’d be a little suspect of the master cylinder letting air in. That would be my guess, anyway. But yeah, I’ve experienced that before, and it is a bit of a conundrum. Where does the fluid go? I mean, if there are no leaks like you said, it doesn’t evaporate so how’s that happening? My guess would be air is getting in through the system on the master cylinder side. So maybe go through there and look at those lines and make sure they’re not old or cracked or anything like that. And maybe do a quick rebuild kit on it to keep that air out. I’m really surprised the fluid isn’t leaking.

I was told that the rear master cylinder, the float that’s supposed to be in it (which it is not I just found out) supposedly helps with that issue.

John Talley: Oh, well I think you just nailed it. So I would say that was probably the case, so get that float … I think I know what you’re talking about, it’s that plastic piece that has the rubber section in there that acts as a cushion, so to speak. Ok, get that popped in there and see what happens.