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CompBrake Pedal Box, Anyone using it?

 
Old 02-27-2019, 06:17 AM
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Default CompBrake Pedal Box, Anyone using it?

I'm finally getting rid of my damn booster, master cylinder started leaking so it's time to upgrade everything the way I want.

Save the "you need your booster" BS, I've driven many many many cars, and I've always hated boosters.

The plan is to do a proper dual reservoir setup with a balance bar. The CompBrake kit is supposed to increase pedal ratio to 5:1 (from 4:1 if my data is correct). This will all be going to standard 1.8 brakes.Yes, stock NA8 brakes, get over it.

They don't mention the master cylinder sizes, or if they ever offer size options. Any advice on sizing?

Haven't decided on a pad yet.

So does anyone have experience with their kit(s) or any part of their kits?
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Old 02-27-2019, 08:32 AM
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watching this with intrest, I find the booster / master cylinder replacement units messy or 'un-finished'

I'm building a bias-adjustable twin cylinder pedalbox for my car but modifying the mazda setup & bulkhead for neatness & space reasons (I live in the UK so right hand drive jdm car so no exhaust heat to boil the cylinders )

https://i.imgur.com/mA3fRgN.jpg

this was the first 'idea' pedalbox to visualise if everything fits, the pedalbox was a scrap spare that had cracked apart & been stuck back togther so no important to a working car, its several alterations later now but I've no photo's sorry

the bulkhead will happily accept a pair of single-circuit cylinders and an adjustable 'ballance-bar' can be fitted to the pedal to operate them. pedal ratio could be adjusted as its 4:1 for the booster setup and somewhere around 5 or 5.5:1 would be more user-friendly.

as to cylinder sizes, usually a .625" for front and .75" for rear but depending on driver preference sometimes sub in a .7", a friend has his 1975 mk2 Ford Escort running equil .625" for gravel.

I've been involved with competition cars for nearly 30 years both building & driving rallycars so prefer adjustable setups but I'm intending to use my Eunos for hillclimbing

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Old 02-28-2019, 10:27 AM
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For those wondering what the OP is discussing. https://www.compbrake.com/product/ma...ylinder-kit-b/
They also offer breakdown kits so you can purchase the individual components or mix and match. We are using a Tilton 600 series top mount pedal set with throttle. More details in the Vegas build thread. Our fabricator had to weld a plate into the firewall to mount it. Some minor oversights in the design of the Tilton box as it is virtually impossible to install their bias cable adjuster if you use the throttle pedal. So unless we make some major revisions to the hardware, I have to crawl under there and turn the bar manually to make bias adjustments.

We are currently using .625 and .75 masters. Pedal effort is still too high so we are swapping the Superlite calipers to the next size larger piston, 1.25 to 1.38". Pedal ratio is not adjustable on the Tilton's. You can reposition the actual metal plate around on the end of the arm a bit but that doesn't change much. It is currently is extended as it can be and still be ergonomically viable. Obviously pedal ratio is a key component and I'm not sure how the Tilton assembly compares to the Compbrake. No plans for another race car just now but if we do I will probably try the Compbrake setup.
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Old 02-28-2019, 06:28 PM
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Originally Posted by emilio700 View Post
Some minor oversights in the design of the Tilton box as it is virtually impossible to install their bias cable adjuster if you use the throttle pedal.
Have you tried using their 90-degree bias cable coupler? At least on the 3-pedal 600-series boxes, it nestles pretty nicely out of the way of the throttle.


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Old 02-28-2019, 11:03 PM
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Yep. That part didn't help. It's difficult to describe but if you had the pedal assembly in front of you you would see how routing a cable in there is so difficult.
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Old 03-01-2019, 06:41 AM
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Originally Posted by emilio700 View Post
I have to crawl under there and turn the bar manually to make bias adjustments
do you find that the adjuster turns itself when in use? especially to the rear

was something that always annoyed me when rallying on cars without adjusters ( would rig something with a few 'loose' cableties on the end of the adjuster to stop it turning but allow movement)

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Old 03-01-2019, 10:14 AM
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We don't have enough hours on the car yet to see if that's going to be a problem. But it did look like it was possible with the Tilton design.
We are still messing around trying to get the balance and effort where I like it. Once we get that sorted I'll probably have John print some sort of lock for the shaft. Really annoying that I can't put an adjuster on the dash though. Oh well.
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Old 03-01-2019, 05:55 PM
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I have one of their complete kits for an RX8. Have not had the chance to use it yet but it seems like a decent solution. I'd like to try it in the Miata as well.
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Old 03-08-2019, 01:52 AM
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Sort of been slacking on getting this done, but still need it done. Lots more research to do, going to bang it out later today.

I have been looking at reviews of CompBrake's products, lots of people hate them. Only found one good review for a firewall mounted booster delete box like the one mentioned here, but who knows how much thrashing that car gets. It wasn't a race car, just an old Escort project out of the UK I think, or some other cool old Ford. If I had a nickel for every good review of a horrible product I've read, I'd have well, lots of damn nickels.

Most people complain their floor mounted pedal boxes bend, and blame the reasoning on the thin steel construction of them vs the aluminium construction of the Tilton boxes they supposedly copy. People have complained that the firewall mounted booster delete boxes have also bent. This is quite concerning. I figured I could still purchase it and just double up the walls with some quick welds, but why spend all that money on a "bolt-on" solution to have to re-engineer it. By the way pedal ratio remains the same with the box, does not increase to 5:1 as I read on this forum somewhere. Problem I have here is my Miata is a daily, I need a bolt in solution because the car doesn't have the downtime to R&D this simple box.

People also complain about their customer service and tech support. So far, my experience with customer service has been trending in that direction, rather mediocre.

I would think the greatest application for these boxes would be the rally community, but I rarely if it all have seen it mentioned or used in these applications. Seeing as many Japanese manufacturers share the booster bolt pattern on the firewall as the Miata, I should be able to fit a firewall bolt in solution made for another chassis. Mitsubishi comes to mind that is the same I think, and given the Lancer evolution chassis' I thought it would be easy to find a rally application product that would bolt in. Surprisingly my quick (un-thorough) search yielded no results. Will try again today.

I know most fully built rally cars run all out aftermarket pedal setups, but from my experience in the amateur rally scene most people don't. The brake booster does horrible things when it comes to a rally car, there has to be an in between solution out there somewhere. I doubt that CompBrake is the one who invented the wheel here, based on my interaction with them and their product reviews. Has anyone found other manufacturers that make these type of firewall bolt in pedal boxes? Maybe they don't exist for a reason...

My biggest concern is pedal ratio, and not getting enough of it. CompBrake advises to drill new holes in the pedal arm. In my opinion, I would think you can only go so high before the angle gets too aggressive. Need to do the math still, and learn all about displacement and pressures with the setup I want to run (stock NA8 non-sport brakes). I'm hoping to achieve at least a 7:1 ratio (from what I've read so far) with some room for extra adjustment if necessary, hopefully that can be done without moving the connecting point on the pedal arm too high.

Emilio, what ratio were you running on your Tilton setup?

Last edited by BlackBerriesAndThinkPads; 03-08-2019 at 11:48 AM.
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Old 03-08-2019, 10:19 AM
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We have not measured the ratio on the Tilton assembly. I'll see if we can get that done today and publish it in our Vegas build thread.
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