mekilljoydammit

What about the Coleman stuff; their T-lock mounts and floating rotors? A bit more expensive than the cheapest Wilwood stuff, but looking at it, doesn't seem like it'd jack the consumables cost up too much.

sixshooter

iTrader: (12)

Emilio said "decent". Stop Tech and HP+ don't qualify. Try PFC PF11 or something else with a known linear torque curve.

OGRacing

iTrader: (1)

lots of things including the rotor can cause drag. The problem with cheap sub $200 calipers we run into issues with them because they are built to reach a price. I like to pick on wilwood so i will continue to do so. this by no means that they are the only guilty parties. to reach a price they made the caliper a 3 piece. that means the caliper body is made in two halves and to reach the required rotor thickness they use a spacer.

Cutting up a caliper like that does decrease the structural strength and they cut it twice. All the calipers worth a hoot in Motorsports have a Square cut O ring for the pistons. pictured below. These square cut O rings do retract the the pistons back into the bores a decent amount. Where we find drag from a flexing caliper is if the caliper flexes further than the O-rings can retract. For example the caliper at the pistons will flex 3mm and the o rings only retract 1.5mm. your pads will keep a slight pressure on the rotors. this can get quite hot as the car is doing 110mph and will kill top speed. The easiest way for us to fix this is to have a stronger caliper. the stronger it is the better chance the O-Rings have to retract the pistons further then the caliper body flexing. allowing the pistons to release the pressure on the pads.



You did ask how can we make a caliper stronger. the easiest and fastest way to make a wilwood or a f33 caliper stronger is with the use of a bridge bolt.







that little bolt is a must in my book. it does requre you to Drill out your pads, but it does miles of good in closing the largest open gap that your caliper has. it also adds a lot of strength. I think goodwin should be able to get you one if you have willywoods.

mekilljoydammit

Thanks for the input, that makes a lot of sense. The bridgebolt makes that much difference? Good, that was on the list. Due to having machining resources and a complete lack of common sense I was going to try to make some frankenbrakes out of a set of Afco calipers I found for cheap.

OGRacing

iTrader: (1)

on a willwood or afco caliper you will notice a firmer pedal and less drag.

acedeuce802

iTrader: (1)

I'm planning for a dual master setup, and I wanted to run through my thought process on master sizing. This will be on a V8 swapped NB with 11.75" Trackspeed front BBK, and the MTuned rear (stock 1.8 caliper over sport rotor). Pads are Carbotech XP10 in front and XP8 in rear. 225/45/15 RS3's. This setup is very front biased, so I'm looking to offset the masters by 1 size to account for this. The main reasons for dual masters are to have 2 true separate circuits, have balance bar adjustment, and be able to size masters separately for nominal bias.

I found this picture which looks like the compact Wilwood master cylinders fit perfectly with the stock mounting holes, which would be great to be able to utilize that. This would however limit how much I could change pedal ratio, as too high of a pedal ratio without being able to relocate the master height could cause bind.



With that my only tuning for pedal lockup force is master cylinder diameter. I can't find any reason that keeping the stock 4:1 pedal ratio and going with a smaller master cylinder bore diameter would negatively affect feel or pedal displacement. Sure, a smaller diameter master cylinder will travel more than a larger, but the larger master cylinder will require a higher pedal ratio, which will then increase the pedal travel. Unless I'm missing a contribution to pedal travel in my spreadsheet (pad air gap, compressability, caliper flex) then a given line pressure will equate to a fixed pedal displacement, without a booster. Reaching max stroke is certainly an issue, but that should be less of an issue with duals. Since instead of 1 master supplying fluid to 4 calipers, now each master only supplies 2.

I've settled on using 3/4" front and 5/8" rear Wilwood compact master cylinders, with a Wilwood balance bar. This would equate to 66% front bias, while the front tires will be 70% loaded at 1.2G (current bias is 73% front). I'll still have an adjustable prop valve in the rear circuit, so that would be dialed back to 80% while the balance bar is in the center position, and then the balance bar can be used with a remote **** for fine tuning. This would also be a 70 lbf lockup, which seems kind of high, but I may be able to increase pedal ratio slightly without raising the master, maybe 4.5:1 or so.

Does this logic seem reasonable?

Madjak

A larger master gives you less fluid pressure so you will want the front to be 0.625" with the rears either the same or 0.7".

I'm running 0.625" front mc on 11.75" rotors with dynapro calipers and 0.7" rear mc on 11.44" rotors with stock NA6 calipers on an offset. Balance bar is currently set a fair way rearwards to get balanced brakes so I could probably switch the 0.7 to a 0.625 to center it. I'm running the stock pedal ratio with the same pads all round and have no issues with generating enough brake pressure on the track.

If you plan on modifying a stock pedal box like me you need to get a smaller balance bar (100mm wide) *** Edit: 75mm - 3" actually *** rather than the generic wilwood one as the centers of the masters will be spaced too wide to fit in the pedal box. Make sure you get a balance bar with built in hard limits so that you can still brake if a circuit fails. It makes bleeding the brakes much harder though.

emilio700

iTrader: (3)

The wheel side of your proposed setup is not excessively "front biased". It should be near perfect in terms of torque. No need to compensate IMO. This based on direct personal experience, not a guess. No harm in in dual masters though.

In any case, I recommend against intentionally setting up a sytstem that grossly underutilizes one end and attempting to compensate with a prop valve or staggered masters. Any brake system, not otherwise electronically or actively regulated, should be balanced under low line pressure trail braking. Wilwood and Tilton prop valves don't affect line pressure until heavier straight line braking.

Its important to tune for the flat, broader area of your pads friction/temp curve (hot). If deliberately under using one end, the pads might always be running in the steep or non-linear portion of their curve (cold or way overheated). That leads to unpredictable braking. One reason I also recommend against mixing different brands or types of pads.

mekilljoydammit

As others have said and as someone who's been running through these calculations too, if your math is suggesting something like 3/4" front and 5/8" rear masters, you should check your math. Secondly, if you're sticking with the same sort of piston sizes as stuff intended for stock boosters/etc I'd be tempted to look at something like the Wilwood 340-4630 if you're not going to be modifying your pedal ratio. Used one in an EProd car and it was a kind of convenient solution to getting a bit more pedal ratio and not having to figure out how to fit a balance bar to the stock pedal - without something to bump up the pedal ratio, the brake torque per pedal force is going to be less than half any stock setup.

acedeuce802

iTrader: (1)

I've validated my spreadsheet with this: Dual Bias Calc.

It still backs up that using 3/4" front and 5/8" rear will be 66% front bias, and using 5/8" all around would be 73% front bias. Brake balance should be around 70% at max decel.

Tuning for low pressure definitely makes sense, since the Wilwood prop valve won't affect that area. However, tuning for lower load would indicate that it needs more rear bias, right? Less load transfer means more rear brake, then use the prop valve to reduce rear pressure at high loads to compensate?

mekilljoydammit

Trimming the balance bar to zero and using the calipers and masters you specified in that spreadsheet I'm seeing 64% front bias. Did you double the piston area for the floating rear caliper?

*quick edit* Oh, and seriously, look at the pedal force needed to generate good deceleration. Yikes.

acedeuce802

iTrader: (1)

Yeah, I have 1.25" entered for both rear outer and rear inner.

I've got pivot offset set to zero, front MC at 0.75, rear MC at 0.625, front pistons at 1.38" for inner and outer 1 and 2 (so 4 total), 11.75" rotor diam front, 0.6 mu front, 1.2" for inner and outer rear (2 total), 10.9" rotor diam rear, 0.56 mu rear.

Then a 2500 lb 50% biased car, 15" CG, 91.6" WB, 23" tires.

64% is probably within tolerance of 66% considering we could have different pad heights and stuff like that entered. With the setup you have entered, change the front master to 5/8" (or anything that's the same front/rear), and let me know if your bias jumps above 70%.

From my thinking, going from 0-1.2G makes your weight balance go from 50-70%. This means ideally that your brake system would be set up 50% bias with a prop valve immediately linearly bleeding pressure form 50% to 70% bias. This isn't how the prop valves react, so you can't be that aggressive on the bias, and it's not like bias has to be dialed in at super low pressures, since you won't be close to lock up. Mid pressure is important for trail braking, and max pressure is important for max straight line braking effort. With a proper prop valve is able to knee around 300 psi or less, I would think you'd want to to have an aggressive bias with proportioning valve to help follow that weight transfer curve. Unfortunately there aren't curves for the Wilwood, so that is a shot in the dark. But I still feel like in this case it'd be better to bias the masters a little rearward and use a prop valve to dial back. Without changing calipers/rotors/pads, the way you achieve proper bias at lockup won't affect pad usage, except for the mid range, which as stated before I think would be more ideal with more rear bias and a prop valve. Let me know if this thinking is incorrect. I've only ran simple lock-up calcs on brakes before, so I'm trying to wrap my head around the theory.

mekilljoydammit

OK, plugged in your numbers so we're on the same page. The whole thing is it looks like you're tuning everything to run around using a prop valve *and* a bias bar? I really wouldn't - prop valves introduce hysterisis and means that you're forcing weird stuff to your master cylinder sizes - in this case, you're having to put 140 pounds of force into the pedal to decelerate at your target 1.2G. That's a bit much.

OGRacing

iTrader: (1)

* eats an apple and watches*

mekilljoydammit

Heh, well, while you're looking, any non-obvious disadvantage to staggering master cylinder sizes? Off the shelf Dynalite-compatible caliper piston bores (1.75F, 1.375R in this case) means either that or doing stupid crap like making a Dynalite with non-standard piston sizes.

Todd TCE

Try to keep your MCs within 1/8" bore of one another to limit any acute angles to the pivot.

Avoid the use of a prop valve AND a bias bar. It's somewhat redundant and given that prop valves are based upon input line pressure your net rear bias will become an inconsistent value.


My .02. Enjoy the page.

ThePass

iTrader: (3)

Good luck with that
The min. quantity to have Wilwood make a custom caliper (extra machining, different piston size, etc.) is large enough that we don't even do it except for a very few cases.



Unrelated to the above, if someone handed me a braking setup that required 140 lbs of leg force to achieve sufficient braking, I would hand it back and say "try again".

mekilljoydammit

I'm a nut job engineer with a machine shop, everything is possible!

... which is distinct from "a good idea"

Leafy

iTrader: (1)

140 pounds of leg force is ******* steep. Thats 1950's no power booster full sized car on 4 wheel drums **** right there. Pull up on the steering wheel and give her all she's got in every braking zone doesnt sound fun.

killjoy, the balance bar and prop valve do different things. The balance bar changes the brake balance at all amounts of braking force while the prop valve only changes it at high forces. You need to tune for both unless you want to suck at trail braking.

Madjak

On the track I'm hitting over 1000psi on the front brake circuit as it's maxing out my sensor, I'm not sure what my rear line is doing as I haven't wired up the sensor yet. I'm only hitting that high at one point on the track which is at the end of the main straight through a big dip where I'm braking from 190kph down to 90 in very a short distance The dip must give me a bit more traction at the brake point as the other corners are all a bit less than 1000psi. I'm pretty much at the limit of traction at all braking points. Doing the maths it shows I must be hitting more than 150lbs at the pedal but I do get a lot of assistance from my body weight transferring forwards as I'm braking. I can't say I really notice the effort at all, once you are used to having to stand on it a bit harder it becomes second nature. I'd certainly prefer that over the fluctuating booster I had previously.