Cutting brakes

woody

eternal noobie
Staff member
Oct 12, 2010
1,347
54
Toquerville UT
Just a quick and dirty on cutting brakes.... I run a EMPI setup that I got on EBay - $140 for the brake setup, figure another $60ish for the fittings and such to run separate lines to the rear brakes.


Simply put, I spend 99.999% of my normal wheeling day in 3WD....front ARB on (effectively a spool) and the rear open. I then rely on the rear cutting brakes to direct wheel speed and traction as needed...it helps a ton with keeping my lightweight FToy on the correct lines, and when most of the crew I run with are on 42's and rear steer, I need all the help I can muster.

First video is of a recent run up the Nasty Half Crack...it was a couple weeks back, and it was cool and damp from recent rains. Needed the rear locker 2-3x to push some of the climbs on this run, but ran it this past Monday and never used the rear ARB once. Pics are via a friend, and gives at least a basic idea of what the entire section looks like.


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Ujcblakenorth

Loves Light Bars
Dec 2, 2020
2
Sandy Utah
And a video look at cutting brakes.... front ARB is on, right rear cut brake pulled. Left rear tire rotates at 2x speed.

#buggythings

Sorry about redirecting an old post here but I’m trying to do something similar and this video has caught my attention.
I’m guessing that using cutting brakes with three active tires doesn’t work as well as using front wheel drive with one wheel locked? It would be nice to see the vehicle in action from an outside perspective instead of a cockpit perspective.

I had the theory that this concept would work but have been told by many people that it won’t work and that the vehicle will simply push through the brakes.
How well does the vehicle turn in 3wd with a rear brake locked?

tia
 

FredSteis

Spotter Required
Nov 25, 2020
106
36
Tampa, FL
"I spend 99.999% of my normal wheeling day in 3WD....front ARB on (effectively a spool) and the rear open. I then rely on the rear cutting brakes to direct wheel speed and traction as needed...it helps a ton with keeping my lightweight FToy on the correct lines"

Well, that actually solves a whole lot of concerns on the rough terrain.
 

woody

eternal noobie
Staff member
Oct 12, 2010
1,347
54
Toquerville UT
I had the theory that this concept would work but have been told by many people that it won’t work and that the vehicle will simply push through the brakes.
How well does the vehicle turn in 3wd with a rear brake locked?
Interestingly, it will depend on the situation. With my old FToy, the transfer cases did not allow for front dig, so only RWD, 4WD or 3WD was an option. FWD was not.

FWD while using cutting brakes will spin the vehicle in a tighter circle since you can fully lock the inside rear tire for the turn. In some situations, you could also lock the outside rear tire and the inside rear tire will rotate in reverse, making for an even tighter spin. However, that also assumes that the front tires have good traction - they may not. In those cases, 3WD (which is always front locked, rear open) and the inside cutting brake works pretty well, and while the inside rear tire likely won't lock completely, it will slow it's speed and force the opposite rear tire to try and spin faster, helping push the rig around.

When sidehilling, keep the front spooled/locked and the rear open, and use the high-side cutting brake to help hold the rig from sliding downhill...the low-side rear tire tries to spin faster and helps keep the front from sliding down while the high-side rear tire (with cutting brake applied) won't spin/slide and will help the vehicle track better.

Same with a hard turn uphill (ie: into a rock wall)- lock front, open rear, cut the inside rear tire and the opposite rear will help push the front up onto the wall. Something that won't work well with front dig only.

Arguably, I used my rear locker less than 1% during a day of wheeling. The balance was constant cutting brake use, literally every time I'd turn the wheel I'd add pressure to the inside tire. Turn right, right cutter. Turn left, left cutter. Learned a TON of tricks during climbs, ledges (forcing one tire to pull up while the other hardly moved), etc.

----

It gets really entertaining when you add a front selectable locker and front cutting brakes (spin around a front tire or sideways slides)....THEN add in a rear driveshaft brake (rig in FWD, rear tires spin in opposite directions). Ridiculous control and possibilities, but arguably only useful for competition.
 

Ujcblakenorth

Loves Light Bars
Dec 2, 2020
2
Sandy Utah
Interestingly, it will depend on the situation. With my old FToy, the transfer cases did not allow for front dig, so only RWD, 4WD or 3WD was an option. FWD was not.

FWD while using cutting brakes will spin the vehicle in a tighter circle since you can fully lock the inside rear tire for the turn. In some situations, you could also lock the outside rear tire and the inside rear tire will rotate in reverse, making for an even tighter spin. However, that also assumes that the front tires have good traction - they may not. In those cases, 3WD (which is always front locked, rear open) and the inside cutting brake works pretty well, and while the inside rear tire likely won't lock completely, it will slow it's speed and force the opposite rear tire to try and spin faster, helping push the rig around.

When sidehilling, keep the front spooled/locked and the rear open, and use the high-side cutting brake to help hold the rig from sliding downhill...the low-side rear tire tries to spin faster and helps keep the front from sliding down while the high-side rear tire (with cutting brake applied) won't spin/slide and will help the vehicle track better.

Same with a hard turn uphill (ie: into a rock wall)- lock front, open rear, cut the inside rear tire and the opposite rear will help push the front up onto the wall. Something that won't work well with front dig only.

Arguably, I used my rear locker less than 1% during a day of wheeling. The balance was constant cutting brake use, literally every time I'd turn the wheel I'd add pressure to the inside tire. Turn right, right cutter. Turn left, left cutter. Learned a TON of tricks during climbs, ledges (forcing one tire to pull up while the other hardly moved), etc.

----

It gets really entertaining when you add a front selectable locker and front cutting brakes (spin around a front tire or sideways slides)....THEN add in a rear driveshaft brake (rig in FWD, rear tires spin in opposite directions). Ridiculous control and possibilities, but arguably only useful for competition.
That’s awesome. Thanks for sharing. The concept of a rear brake on the DS is a new one for me. Way cool idea. I’d love to find a way to implement that.

my Jeep has ABS I stalled in it. Have you found any issues with installing cutting brakes on an ABS vehicle?

My plan was to use electronic solenoids. Lock out the brakes I don’t want to use and that would free up my brake pedal to control the amount of pressure I want on that last corner. It would also allow just front brakes to be activated for rear digs.
 

woody

eternal noobie
Staff member
Oct 12, 2010
1,347
54
Toquerville UT
That’s awesome. Thanks for sharing. The concept of a rear brake on the DS is a new one for me. Way cool idea. I’d love to find a way to implement that.

my Jeep has ABS I stalled in it. Have you found any issues with installing cutting brakes on an ABS vehicle?

My plan was to use electronic solenoids. Lock out the brakes I don’t want to use and that would free up my brake pedal to control the amount of pressure I want on that last corner. It would also allow just front brakes to be activated for rear digs.
I would never use a fixed solenoid for this. The variable control with a hand brake is what makes it effective, and keeps you from breaking.

ABS should disable in low range automatically.
 

whiterhino

Spotter Required
Nov 10, 2020
35
michigan
Woody, You use a dual lever and pull to engage? I've heard people say they get get better brake pressure by pushing. I'm sure part of it is the packaging.
I've had a cutter brake in the back for some time but with a Grizzly it really only helped with front digs. Then added the ARB this year but haven't had a chance to use it much since I bought the buggy.
 

woody

eternal noobie
Staff member
Oct 12, 2010
1,347
54
Toquerville UT
Dual levers/pull - correct. With the FToy, the cutting brake levers were in the same arm plane as the shifter, so it was very natural to reach. They were nearly arms length away too, so maximize your pulling leverage versus having them close to the driver/body.

The new buggy will have some similarities in layout, and I'm used to the pull-action to activate them.
 

Scooter

Loves Light Bars
Nov 9, 2020
3
Washington
Woody, You use a dual lever and pull to engage? I've heard people say they get get better brake pressure by pushing. I'm sure part of it is the packaging.
I've had a cutter brake in the back for some time but with a Grizzly it really only helped with front digs. Then added the ARB this year but haven't had a chance to use it much since I bought the buggy.

I've been seeing this recently too. I've never had cutting brakes but will on the new buggy. It seems far more natural to me to want to pull vs. push. I feel like the human body can naturally pull more weight than push, at least from a seated position, but I think it does depend on where the levers are located.
 

woody

eternal noobie
Staff member
Oct 12, 2010
1,347
54
Toquerville UT
Got asked about the dimensions of the cutting brake itself...

Base is about 8"l x 3"w - handles are 15" from bottom of base to tip. Max handle throw is 10" (half that needed in actual use)
 

MDNyota

Loves Light Bars
Jan 15, 2021
4
NM
Woody, so are you running toy dual cases or do you have the ability to do front digs? Also, I can't wrap my simply brain around why/how the the rear tire is rotating +/- twice as fast in the one video, could you elaborate?

Thanks
 

woody

eternal noobie
Staff member
Oct 12, 2010
1,347
54
Toquerville UT
Woody, so are you running toy dual cases or do you have the ability to do front digs? Also, I can't wrap my simply brain around why/how the the rear tire is rotating +/- twice as fast in the one video, could you elaborate?

Thanks
That's how every open diff works. Stop one tire, the opposite doubles in speed. If one is 33%, the other is 66%....ir 80%, 20%....etc etc Driving down the street (straight) it's 50/50.

The FToy ran two cases, and no ability to disconnect the rear...so no front dig option. The front and rear driveshafts spin at exactly the same speed. Lock in the ARB and the tires spin at exactly what the ring/pinion ratio ends up sending....3.73:1 or whatever....with a 50/50 split between each side on that axle Unlock the diff, and "jam" one tire/brake (with cutting brakes), and the power transfer sends what would have been 50/50 all to one tire....so 0/100.

This is the reason running in 2WD with a rear spool (or locked ARB, or a Detroit under load) will spin attempt to spin both tires equally in a turn, and the reason the tires squeal in a corner as each spins in different circle sizes, but 50/50 for power...one has to slip. Open/unlock the rear (a normal daily driver) and as the inside tire makes a smaller circle than the outside, the differential DIFFERENTIATES between those two to allow for power distribution to each side, without tire slip (assuming equal traction)

Physics ;)
 

MDNyota

Loves Light Bars
Jan 15, 2021
4
NM
Well when you put it that way..............duh, guess I just didn't think about it long enough. I just finished buggy recently, but already want better maneuverability. I have been toying with options for front digs and the more I look into D300 to toy case to A340 to etc, I'm thinking an ATLAS to 400 might end up similar in cost (which I don't want to spend just yet). Therefore, your cutting brakes w/ ARB in your Ftoy, might be the ticket. Looks like you used it quite a bit.

Would you say it helps you pivot pretty well? I'm currently spooled 9.5" w/ fj80 RCVs Diamond front; Strange 9" 35 spline spooled in rear. Was thinking ARB front first but maybe I'll entertain ARB rear w/ cutting brakes.

Thanks for the response!
 

woody

eternal noobie
Staff member
Oct 12, 2010
1,347
54
Toquerville UT
I honestly barely know how to drive offroad without cutting brakes anymore...lol

Sold the FToy at Trail Hero, and am borrowing the Truggy from Rich for this weekends Winter 4x4 Jambo (mid-90's Jon Bundrant build, iconic rig!) It has lockers/spools front and rear...and it's driving me insane! The improved maneuverability with the cutters is hard to explain. Once you have cutting brakes, your wheeling style changes....rear locker is used less than 1% of your day, and only for short climbs, just enough to get the tires started up. Literally on for 1-2 feet at a time, then off. Then, every time you turn the wheel right, pull on the right brake...left turn, left brake. It changes everything. I'll never claim that I kept up with my rear steer friends, but they did keep inviting me back ;)
 

albert

Loves Light Bars
Mar 12, 2021
1
san diego
Hey Woody and

i am trying to build out a off-road 19 rv and just realized they don’t make a rear diff lock for this yet. Wondering if you think the cutting break system would work for something this heavy/bulky. I have even considered a limited slip as an option in desperation. Any advice is much appreciated

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