Brake power loss on steep grades

[YannieSolo]

Hey y'all,

So I have a new gladiator with 37's and I've only gone off road a couple times now, but both times I've found myself going down quite steep grades (25ish degrees).

In both instances, my breaks seem sketchy. The pedal, after a couple of presses end up on the floor with no additional travel, and I feel like if I pump them again I'm going to lose braking power.

Once I'm back on level ground, I pump them a few times and feel the pressure come back into the pedal.

Anyone have any thoughts on this?

Thanks!

Sponsored

 

[Kevin_D]

Have you checked the brake fluid level?
Sounds like at that extreme angle, you may be starving the master cylinder for fluid.

Kevin

 

[YannieSolo]

I'll have to check. I honestly hadn't as I literally have a mostly gentle 6,500 miles on it, but I suppose it's possible that it didn't come filled adequately from the factory.

 

[ShadowsPapa]

I'd expect air in the lines and the brakes not coming back if that happened. You run low on fluid, it takes in air. Air compresses and gives a spongy pedal.

Are we sure it's not loss of power in the power brakes? These are electric vacuum pumps, are they not? Or is this different on these?

It would have to be awfully low - and an extreme angle to get air into the system.

This is how mine came -

 

[chorky]

I'd expect air in the lines and the brakes not coming back if that happened. You run low on fluid, it takes in air. Air compresses and gives a spongy pedal.

Are we sure it's not loss of power in the power brakes? These are electric vacuum pumps, are they not? Or is this different on these?

It would have to be awfully low - and an extreme angle to get air into the system.

This is how mine came -

electric power brakes?? Wow thats crazy i gotta go look now. Anyway. I had the same situation as the OP A couple times. However it was early on when the glad was only a few weeks old so i was still getting used to everything. Consequently i pumped the brakes a ton going down a somewhat steep grade. I attributed it to my pumping the brakes too much causing the vacuum chamber to loose sufficient vacuum. And this would make sense if it is in fact a electric pump.

also. The OP must consider the fact they are on 37’s. Which of course requires more oressure to stop that rotational mass as compared to stock tires. For example, when I stepped up to 33’s from 31’s on my 06 TJ the braking force required was distinctly different.

 

[HankB]

It is possible going down a steep incline off road triggered your ABS system. My Glad is still new and I haven’t activated the ABS yet, but on other cars where I have, increased peddle travel is part of the process and pumping the brakes can exacerbate the issue. An incline shifts the force on the vehicle from weight from mostly downward to partly in the forward direction. When this happens because the downward force is also the major driver the friction force between the tires and ground, stopping performance degrades. As you go down applying the brakes stops the wheels from spinning, but the truck is still being “pushed” down the hill by gravity And the tires are less “sticky”. With poor surface conditions some wheels may continue to spin, and others lock up. The condition becomes just like being on icey pavement and triggers the ABS. Yes I realize ABS causes pulsing in the brakes and a hammering noise, but if I was going down a 25% grade my attention would be on other things. So it is possible to overlook that

 

[YannieSolo]

I think with "off road +" enabled it deactivates abs?

I started looking into if my Jeep had an electric pump... Then, digging into those threads on the forums I found others with my issue.

Seems like this might be unique to the ecodiesel with adaptive cruise control. (Sorry I didn't mention that earlier, didn't think it was relevant).

Might be time to go into the shop and start complaining.

 

[YannieSolo]

https://www.jeepgladiatorforum.com/forum/threads/soft-brake-pedal-on-my-gladiator-rubicon.46858/

 

[Mr._Bill]

I think with "off road +" enabled it deactivates abs?

I started looking into if my Jeep had an electric pump... Then, digging into those threads on the forums I found others with my issue.

Seems like this might be unique to the ecodiesel with adaptive cruise control. (Sorry I didn't mention that earlier, didn't think it was relevant).

Might be time to go into the shop and start complaining.

The dealer is not going to do much. They will check that everything is working, and then tell you the problem is the large tires.

 

[YannieSolo]

Ugh man.

Anything I can do to improve their performance? I feel like I'm going to go out of control on those steeper hills once I'm "out" of brake travel in the pedal.

 

[ShadowsPapa]

electric power brakes?? Wow thats crazy i gotta go look now. Anyway. I had the same situation as the OP A couple times. However it was early on when the glad was only a few weeks old so i was still getting used to everything. Consequently i pumped the brakes a ton going down a somewhat steep grade. I attributed it to my pumping the brakes too much causing the vacuum chamber to loose sufficient vacuum. And this would make sense if it is in fact a electric pump.

also. The OP must consider the fact they are on 37’s. Which of course requires more oressure to stop that rotational mass as compared to stock tires. For example, when I stepped up to 33’s from 31’s on my 06 TJ the braking force required was distinctly different.

Electric vacuum pumps have been around for decades - both for racing and in production vehicles on the road.
(The power brakes aren't electric - the ASSIST method is.)

Another type of system used by GM took hydraulic pressure from the PS system to boost the brakes, not vacuum.

Because of the demands on modern engines, and the often lack of vacuum from the engine as a vacuum pump, some use an electric vacuum pump. A Power Brake Booster Vacuum Pump.
It's been a thing in racing for many years - high lift cams with an LSA not large enough to allow vacuum in the intake manifold high enough to operate a power brake booster - you install a vacuum pump to pull the vacuum for the power brakes. I'm talking about the big vacuum device between the firewall and master cylinder - the thing that assists you in pushing the pedal down, giving more force against the master cylinder piston.

Engines like that in my Javelin don't always run high enough vacuum to make a power brake booster function. My cam isn't radical enough to be a real problem, but anything larger and I'd likely be installing a vacuum pump. Mine runs about 14 inches vacuum , 17 on a really good day, sometimes only 7 and that's into the "damn, no power brakes" realm. 20-21 inches is normal.

Yes, bigger tires mean you have less braking as the tires have a lot more leverage over the wheel. The tire is a lever - the spindle the fulcrum. The distance from the spindle to the brake pads is fixed, doesn't change, but when you put larger diameter tires on it, the tires now have a greater mechanical advantage.
Go with big tires, your braking efficiency suffers. People expect braking and steering to remain the same - it just ain't possible when you start upping tire diameter, even wheel changes.
You actually increase braking distance by measurable amounts with bigger tires.
In other words if you avoided that obstacle easily with stock tires, you'll likely hit it with bigger tires.

The OP states pedal to the floor - lack of boost does NOT make the pedal go down farther, it does not impact the pedal travel/distance - it means you have to stand on the pedal with both feet to stop, but doesn't change how far down the pedal travels.
Only the hydraulics can impact how FAR the pedal travels.
The booster impacts how big of a guy is needed to push the pedal to stop - but the pedal distance won't change.
If the thing ran low on fluid - it won't be better later that day. Once air is in, it's in. It's compressible so pumping the pedal will compress the air and bring the pedal back up. But 5 minutes later when you press that pedal, you will be recompressing that air and have to pump the pedal again. The air does not go away. It's there until bled out of the system.
If there was an extreme steep angle and the master cylinder ports were exposed to air because of really really low fluid in the reservoir, it won't do a thing until or unless the pedal is pushed or the ABS kicks in. The master doesn't suck air in unless used.
So if you hit a huge hill, your reservoir was all but empty and the ports were exposed to air, once back on level ground all would be fine because the brakes were not used, ABS didn't kick in.
But if you used the brakes while the ports were exposed, then you got air into the system. That issue won't just go away.
But look at that reservoir - unless there was only 1" of fluid in there, that truck had to be at a good 45 to exposed the master cylinder ports to air.

 

[JTR178]

Ugh man.

Anything I can do to improve their performance? I feel like I'm going to go out of control on those steeper hills once I'm "out" of brake travel in the pedal.

Try Selec-Speed Control. Game changer.

 

[YannieSolo]

Think I could just select speed control down steep grades and tap the brakes when I need a little extra pause?​

Sponsored