My rear brake pedal has to be depressed a long way down before it works. It seems to work OK with adequate power, and not noticeably spongy. I have checked the fluid level in the reservoir and it is fine.
Any ideas what I could do? Would it pass an MOT as long as the power is enough.
I think the MOT definition is that there shouldn
t be excessive travel in any brake lever/pedal. My own MOT tester expects the brake to be fully applied before the pedal reaches half of its travel and will log it as an advisory should it go any further, if it goes up to 3/4 travel then he logs that as a failure. The usual cure is to replace the fluid after first checking for excessive wear on the pads etc. thats assuming all the pistons are in good order.
Pad wear doesn’t affect the Pedal travel, as all Hydraulic Brake Systems are ‘self adjusting’.
When was the Fluid last replaced?
Should be done every year really, regardless of Mileage.
Same question for Bleeding the System, and does it have ABS?
Master Cylinder Rod is adjustable, and being a big lumpy Twin, the Locknut can easily come loose, happened on my Stelvio, check and adjust if required.
It should have around 4mm of travel on the Rod before contacting the M/C Piston.
Does it pump up? As in, will quick repeated depressions of the pedal have it working nearer the top? If they do it needs bleeding.
Is it worse after a longer period of riding since its last application? If so it is warped discs and you are suffering ‘brake knock off’.
Less likely, but check the pads. Sometimes when the material gets thin it starts lifting off the backing plate and makes the brake action more spongy.
I checked the free play in the rod and it seems to be ok. I doesn’t pump at all but seems to have enough power on first application, consistently, just with too much travel. I think the pads are OK and suspect that I just need to replace the fluid, will try that anyway.
Silly question(s) time -
Has it only recently happened, if so, what’s different? Have you done anything to it?
Did you put new pads in, if yes, they usually take a while to bed in, until then pedal/lever travel will be greater than normal. Also friction coefficient will not be at its best. This could take quite a few miles.
PS: this also happens when you take pads out and put them back, if the caliper pistons have been disturbed.
It definitely sounds like it just needs Bleeding.
Depending where the Bleed Nipple is located, it can help to remove the Caliper from the CARC Unit, and hang it up as high as possible while bleeding.
You want the Nipple to be the highest point in the line.
Before bleeding though, find a piece of wood/metal the same thickness as the Disc, and tape/tie it in place between the Pads.
It’s always a good idea to replace the Fluid, particularly if you don’t know when it was last done.
As it was going in for Mot anyway, I just got them to change the fluid for me before doing the MOT. Did the trick. Really brings it home how much the fluid can deteriorate over time. I guess it happened gradually.
Nice fresh MOT anyway.
Doesn’t take long for the Fluid to get grubby, especially in our damp climate.
Hydraulic Clutch on the 2V Engines?
Check the Fluid in there too, that goes ‘bad’ even quicker.
This was the Reservoir on a friend’s Stelvio that I did some work on recently . . .
Couldn’t decide whether to flush it out, or dip a Quill in it!