netacoma2003

I have an '09 base convertible Z51 with ~23k miles. The brakes seem to be fantastic when they're dry, however, when I drive in the rain they get REALLY stiff.....to the point where I almost have to stand on the pedal.

Is this common or is something else going on?

AORoads

Haven't heard that in a long time (since the days of all drum brakes). Some simple questions: last time brake fluid was flushed?* have you recently bled the brake fluid? did you change pads recently and to what? did you change tires recently and to what? look at all four tires---what is the condition of the tires---inside edges, too?

If it were me, I'd start with the simple things first such as make sure by tire gauge (not DIC) that tires are at correct pressure. Do a break in/bedding procedure per tech section of StopTech brakes website.

http://www.stoptech.com/technical-su...and-procedures

*if you haven't flushed the brake fluid, generally, it's recommended by some to do so every two years. your car could have been built in '08---that makes it potentially six years old.

Boomer111

Agree with all that AORoads said.

If nothing has been done recently but the fluid is fresh maybe the pads have glazed over.

Not sure if this would cause brake pedal stiffness but braking performance can be reduced greatly.

Check the fluid level, if fluid was just changed maybe some air pockets in the line.

Post up so we can learn.

netacoma2003

I haven't done anything to the brakes since I purchased the car with ~15k on it.....so I assume the brakes are original.....including the fluid.

Will need to look into my stopping power a bit more as the condition can be quite annoying.

glenB

Is it possible you are engaging the ABS?

All things being equal, the only variable being rain, I would exclude pads, rotors fluid..... because they function normally when dry, so, either the rotors are getting really wet, or the ABS is engaging.

AORoads

Not to argue, but why would ABS engaging cause OP to have to stand on the brakes to get any kind of braking action? And doesn't ABS engage when the car's wheel(s) detect slip---if that's the case, couldn't that be related to tires, pads or rotors, potentially?

All have different braking and stopping characteristics/coefficients in wet compared to dry conditions depending on their condition and design.

Just thinking out loud here.

glenB

My thinking is that the ABS, which gives a firm pedal when engaging, and feels very similar to reduced vacuum in the booster.

The OP states that the problem exists only in the rain, which would allow the brakes to lock up, to whatever degree. If it was a pad or fluid problem, it would most likely do it under most occasions, not just raining.

I've had my brakes lock up in the dry and the pedal gets hard, like the OPs complaint. At first you press harder and it feels like you're sliding. In the old days the pedal would kick back, but I've not noticed this in my vette.

AORoads

You have a point there. My older DD suv does kick back on ABS activation. I can't recall that "feeling" (which is quite distinct in the older car) in the Vette. And that could make it feel like one is pressing more to get what feels like less stopping power (but might not actually be less).

How about a glazing issue with the pads/rotors that gets exaggerated only in wet weather? Possible, glenb?

v26278

Could be a hydraulic issue with one wheel getting more pressure than the others, causing ABS to kick in and the driver to push harder on the pedal. This would be more pronounced in wet conditions with the one wheel trying to lock up. If the fluid level isn't going down that would rule out a leak, likely moisture got into the fluid. I would bleed the system and see if that helps.

netacoma2003

I'm leaning towards the pads or rotors being glazed rather than wheel/tire slippage.

I've got basically new Hankook Ventus V12 tires and they're AWESOME!

Snake.Oiler

Brakes getting wet. Same thing happens with my truck.