Cutting brakes

[woody]

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.

Empi 16-2540 Upright Single Handle 3/4" Turning Brake Vw Baja Dune Buggy | eBay

Empi 16-2540 Single Handle Turning Brakes With Upright Handles. Designed Flow Through System Does Not Interfere With Your Normal Brake Pedal. Ideal for Quick Turns In The Sand Or Dirt. Sandrail Or Dune Buggy Vehicles With Disc Or Drum Brakes.

www.ebay.com

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.

 

[woody]

And a video look at cutting brakes.... front ARB is on, right rear cut brake pulled. Left rear tire rotates at 2x speed.

#buggythings

 

[Ujcblakenorth]

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]

"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]

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.

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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]

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]

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]

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]

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]

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]

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)

 

[whiterhino]

How tall is the mechanism not including the handle?

 

[woody]

2-1/2"...plus the fittings to connect to the top of each cylinder

 

[whiterhino]

Thanks. Much appreciated.

 

[MDNyota]

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]

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]

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]

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

 

[whiterhino]

I turn my locker off all the time in dry conditions but pretty much leave it on in wet, mud or snow.

 

[albert]

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

 

[woody]

WAY WAY too much weight.

 

[akeboi]

WAY WAY too much weight.

I’m kinda stumped on why my cutting brake setup isn’t working. Running a single lever 3/4 bore in my 2 door Jeep. Everything’s plumbed, no leaks, bled properly multiple times. I can lock up a tire when the rear axle’s jacked up, it just doesn’t have nearly enough clamping force to lock up or even slow down a rear tire in actual use, no matter how hard I pull the dang thing. Maybe my stock calipers don’t have enough clamping force? No idea

 

[akeboi]

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’m in the same boat, did you ever get around to implementing that setup?

 

[woody]

I’m kinda stumped on why my cutting brake setup isn’t working. Running a single lever 3/4 bore in my 2 door Jeep. Everything’s plumbed, no leaks, bled properly multiple times. I can lock up a tire when the rear axle’s jacked up, it just doesn’t have nearly enough clamping force to lock up or even slow down a rear tire in actual use, no matter how hard I pull the dang thing. Maybe my stock calipers don’t have enough clamping force? No idea

If all 4 tires are on near-equal traction surfaces, it will never lock in 3wd. If the "locked" rear tire is on high traction and the "unlocked" rear tire is on something like sand, then one will lock and the other will spin.

 

[whiterhino]

If all 4 tires are on near-equal traction surfaces, it will never lock in 3wd. If the "locked" rear tire is on high traction and the "unlocked" rear tire is on something like sand, then one will lock and the other will spin.

I agree. There have been times that I have gotten frustrated because it doesn't seem to work and other times it works great. I've come to realize that if no tires are slipping, it doesn't work, it simply follows your turning radius. That said, there are times when it works - it works amazing.
My brakes don't hold as well as I would like on inclines so I just ordered a set of Hawk SD brake pads for all 4 corners. Curious to see how they work. Although the website recommends the LTS for trucks/jeeps, I contacted customer service and was recommended to the SD series.

Jeep

Super Duty

Installing this week and will give them a whirl Saturday.

 

[woody]

I've come to realize that if no tires are slipping, it doesn't work, it simply follows your turning radius. That said, there are times when it works - it works amazing.

but, it IS working. 95% of cutting brake use has nothing to do with stopping the tire.

Ever walked when it's windy? "leaning" into the wind is exactly how cutting brakes work....you are "leaning" into the high-side of a sidehill, or "leaning" into the inside of a turn. The slight slowing of one tire and the slight added speed of the other tire (even if you don't see it) is doing exactly what it's supposed to. It's not stopping the tire. It's taking a slight bit of pressure/leverage and redirecting it from one side to the other.

 

[whiterhino]

but, it IS working. 95% of cutting brake use has nothing to do with stopping the tire.

Ever walked when it's windy? "leaning" into the wind is exactly how cutting brakes work....you are "leaning" into the high-side of a sidehill, or "leaning" into the inside of a turn. The slight slowing of one tire and the slight added speed of the other tire (even if you don't see it) is doing exactly what it's supposed to. It's not stopping the tire. It's taking a slight bit of pressure/leverage and redirecting it from one side to the other.

I buy that completely. I guess it would be better to say that when all 4 tires have traction, I can't tell the difference in turning. I understand the "leaning into the wind" but if both my front tires have good traction, they follow the turning radius of the vehicle. Otherwise, they would have to be skipping sideways or something binds. Much like it's not a good idea to do a front dig on super grippy surfaces. That's how front axle shafts get broken.

Rich helped us build a shotcrete feature here. One portion "kinda" mimics Rocker Knocker but with a tighter right hand turn if you go straight up the first ledges than Moab. I've played on this countless times. With/without rear ARB locked, with/without cutting brakes. I have found that it works best with the rear ARB open, but only a few times have I really noticed a difference using the cutting brake. Why? Usually the front tires have so much traction that they won't slide sideways. But if I get far enough up the wall where the front starts to unweight, then it works really well. The pic below is the spot. If I try to turn right on the flat area, it follows the wheelbase. Once I get further up, it will slide around.

 

[whiterhino]

Speaking of push vs pull on cutting brakes, I went with "push" partially due to packaging. The problem I had was getting good pressure at full push because the handles were too far away and my arm was at full extension. So I cut and bent them so they are closer. I can now put full pressure and still have my arm bent. Much better! It's going to take a little getting used to because they are sorta in the way between the steering wheel and shifter. But so far - so good.

 

[whiterhino]

So Woody, a question about cutting brakes. I never feel like mine are bled good enough. Maybe I'm misinterpreting. My cutting brakes feel mushy. If I push on the brake pedal, they firm up. When I push harder on the cutting brake, it pushes back into the brake pedal. Is this normal? It makes it difficult because each time I know I am going to try to lock up a tire, I kinda pump the brakes to get a firmer bite.

My brakes have been bled multiple times. Gravity, pump up and bleed, crack and push pedal slowly and vacuum pump. But I have to say, my vacuum pump is a cheesy hand pump, not an air assist pump.

Not sure what my next step should be.

 

[woody]

A "real" air assist pump is vital for good cutting brakes....my FToy worked but had the same symptoms you describe. The new buggy is 10x better since they were air-bled.