Questions about Pedals

Alright so I got this 1976 fiat 124 that im kinda of building into a track/street car and its now time to consider the pedal situation. Im going from cable clutch to hydraulic and from cable to electronic throttle (putting in a rx8 Rotary) So obviously the stock pedals are not gonna work. I've considered multiple options but the one that tickles my pickle the most is some universal floor mounted pedals, you know something like this:

my only problem is I do not know how to hook up the brakes with this kind of setup. Obviously you can no longer have a brake booster so my question is how do these pedals actuate the master cylinder? And can you use the stock master cylinder? Im new to a more race oriented build so any help is appreciated.

Behind the pedals are usually three master cylinders.  One for the clutch and one for the brakes or, more often, one for the front and one for the rear brakes. 

Run the lines from the masters to the appropriate destinations, T’ing the front and rear lines to each wheel

In reply to jfryjfry :

ooooh so the master cylinder is just right on the pedal, alright alright

In reply to jfryjfry :

now, with these setups do you have metal brake lines still? or do you just go rubber all the way, typically i mean

Metal is more time consuming to run but better for several reasons.  

You can run short rubber/braided lines from the masters and slaves to the hardliners for flexing and r/r purposes. 

Moral support granted for the swanky floor mounted pedals.  They sound like a proper solution given the swap.  They look really serviceable in that location as well.

Make sure there is enough room to install these.  Seriously consider mounting the reservoirs up higher by running a piece of hose from the master up to the reservoirs.  Thats why they are called remote.  You will end up with 2 brake masters.  Each is sized accordingly to the brakes they are actuating.  Lots of research on your part to get this right.  There will be a balance bar between the two brake masters, so you can adjust that bar to give more or less pedal pressure to each master relative to each other.  I just went thru this converting my LS3 powered TR8, except I ran hanging reverse mount pedals.  Ran the remote cylinders so they stick up thru the top of the dash.  Can check levels visually as I'm driving and can top off easily if needed.  Looks real racy too.    Pedals are $250ish.  Each master is 85ish.  Then you need lines, adapter fittings, etc.  I also added a remote adjuster for the brake bias that mounts on the dash.  Can make brake bias adjustments on the go.  Don't have to stop, crawl on my back and turn the bar with a wrench every time.  Was going to add gauges to show line pressure as well, but at this point I'm probably not going to do that unless I have an issue I can't diagnose.  Not a cheap way out.  All in with Wilwood parts everywhere.  Calipers, aluminum hats and vented rotors, pedals, cylinders, hard lines. fittings, etc.  I'm around $3500 in brakes, and I could have spent more on the calipers and rotors.  I figure at 2400 pounds, I don't need nascar level calipers and rotors, so I went a little smaller, lighter, and cheaper.

I have the tilton pedals pictured above. The explanation about remote resevoirs and master sizing by TR8Todd is right on. With a 124 chassis you do not want to spend too much time trying to fit everything under the dash/on the floor. My pedals with the smallest master cylinders are about 3.5" from the nearest firewall location, so there is some real estate figuring to do. I ran banjo bolts from the masters to hardline out to the car corners, with an3 stailess braided from the suspension pickup points to the calipers.

You could potentially mount the masters on the outside of the firewall, with the pedals inside the cabin.

One other thing to consider is that with the masters mounted low in the car, you may need to run residual pressure valves to keep the calipers/drums from pulling back too much.

In reply to manladypig :

Please reconsider floor mount.  Several reasons. I know they are easier to put in but there are some real disadvantages to them.  

First the master cylinders are often lower then the brake calipers. That makes bleeding difficult.  

Second the lever on floor mount tends to be much shorter than hanging pedals allow, thus your leverage is worse. That means a smaller movement of your foot has a greater effect ~ brakes tend to feel more like on off switch than something easy to modulate. Thus threshold braking is much harder to achieve. 

Third most cars have hanging pedals so almost all of your previous training doesn’t apply and you’ll need to relearn how to brake.  

Like others have said, please reconsider floor mount pedals. Like others have written, they are harder to drive and bleed. On that last point, they also require a check-valve in the lines if they are mounted lower then the calipers. That is to prevent all the fluid from flowing back to the master cylinders if ever you have a leak near the calipers. Also, the floor needs to have a lot of structure added if you go floor mount.

If you decide to go floor mount, don't forget to reinforce the floor just like you would if you mounted a seat. The forces are similar.

Personally, I would go with something like these:

or 

Unless you are built like Clyde the orangutan, there is no way in hell those pedals work in a 124 Spider.  You are already sitting too far away from the steering wheel, and those are going to cost you more leg room.

Unless you intend to sit in the rear seat, and add a couple of feet to the steering column, those won't work.

In reply to Streetwiseguy :

The required fabrication is a little more difficult than floor mounts but can be done.  Maybe you don’t have the vision to imagine how to do it. ( I wish I could figure out how to post a sketch). But the added work will pay off in less time on maintenance and easier driving.  

Streetwiseguy said:

Unless you are built like Clyde the orangutan, there is no way in hell those pedals work in a 124 Spider.  You are already sitting too far away from the steering wheel, and those are going to cost you more leg room.

Unless you intend to sit in the rear seat, and add a couple of feet to the steering column, those won't work.

I was going to say this. The fiat is set up with pedals close and steering far.

If its going to be a street car it should still have a proportioning valve om the rear brakes IMO as it automatically changes the f/r balance for you based on pedal pressure so wet and dry balance are both right without driver intervention.  On the track it gives you a bit more grip coming onto and off the brakes.  More to setup but for sure on the street its time well spent I think.

frenchyd said:

In reply to Streetwiseguy :

The required fabrication is a little more difficult than floor mounts but can be done.  Maybe you don’t have the vision to imagine how to do it. ( I wish I could figure out how to post a sketch). But the added work will pay off in less time on maintenance and easier driving.  

I was talking about floor mounts.  Underdash unit would be fine from the footwell standpoint.

In reply to Streetwiseguy :

Several of the race cars I’ve built had to use the floor mounted pedal assemblies and yes you are correct they do take up leg room. 

One a tube framed Chevy V8 powered Devin  had me driving cross legged (and  I only have a 28 inch inseam) because there just was no other way  to drive.  Left foot throttle right foot clutch and brake. In a right hand drive car with brutal acceleration. 

That plus diving head first under the steering wheel to add fluid made replacing that system the highest priority following the race. 

mke said:

If its going to be a street car it should still have a proportioning valve om the rear brakes IMO as it automatically changes the f/r balance for you based on pedal pressure so wet and dry balance are both right without driver intervention.  On the track it gives you a bit more grip coming onto and off the brakes.  More to setup but for sure on the street its time well spent I think.

Fiat had a very interesting proportioning valve from the factory. It allowed full braking front and rear until the nose started to dive and the rear rose, The valve was bolted to the body with a rod to the axle, and when the axle dropped, the valve cut off pressure to the rear brakes

mad_machine said:

mke said:

If its going to be a street car it should still have a proportioning valve om the rear brakes IMO as it automatically changes the f/r balance for you based on pedal pressure so wet and dry balance are both right without driver intervention.  On the track it gives you a bit more grip coming onto and off the brakes.  More to setup but for sure on the street its time well spent I think.

Fiat had a very interesting proportioning valve from the factory. It allowed full braking front and rear until the nose started to dive and the rear rose, The valve was bolted to the body with a rod to the axle, and when the axle dropped, the valve cut off pressure to the rear brakes

That's not all that unusual, especially in vehicles that saw a wide ride height variation. My 80's Toyota pickup had something similar.

One thing to note about dual master cylinder setups that use a bias bar - it's a fixed F:R ratio. This means that the proportioning is really only correct at one level of deceleration, which basically means maximum stopping on track. On the street, it would too much front brake.

I ran floor mount pedals on my Locost with residual pressure valves. No real problem with bleeding that I recall.

Keith Tanner said:

One thing to note about dual master cylinder setups that use a bias bar - it's a fixed F:R ratio. This means that the proportioning is really only correct at one level of deceleration, which basically means maximum stopping on track. On the street, it would too much front brake..

Sure but its no different than any system.  Optimal track performance will need the brake bias tweaked and bias set for sticky track tires will be a light on rear bias on street tires......but it will be safe and provided much better street braking than not having a proportioning valve.  There is a reason all street cars have them.

Actually, you're exactly wrong when you say it is better than not having a prop valve. Having fixed bias from a bias bar and/or mixed MCs is exactly like not having a prop valve. The bias bar and staggered MCs are just another way of adjusting the front/rear bias, no different than juggling piston sizes in the calipers or rotor diameter. Like you said, there's a reason street cars aren't built this way.

That setup is different from other systems in a very important way. A typical bias valve has a knee point in it that allows it to very roughly approximate a curve, and a curve is what you want as the ideal bias will change with the rate of decel and the amount of weight transfer. A bias bar and/or staggered MC sizes has a straight line and a constant F:R bias. If you just run a setup like this with fixed bias designed for high grip tires at maximum decel, you basically won't be using your rear brakes on the street. That's stable if you lock the fronts first, but you give up a bunch of stopping distance and it's no fun when you hit stuff.

This knee point usually comes from a ball/spring setup. Here's a writeup I did about 15 years ago with the actual numbers used in production cars: https://www.flyinmiata.com/tech/stock_bpv.php

In reply to Keith Tanner :

Without the proportioning valve you don't have a knee of any kind in the system so you have the worst possible design. 

The factories set base bias by selecting wheel piston size.   Most aftermarket bolt-on setups try to get close the the OEM choices but many (most?) DIY or race upgrades have bias that is odd at best.  A dual master setup with a bias bar will let you correct for almost anything at the wheels to get a useful bias balance back into into the system.

.....but a proper system still needs to have an proportioning valve to provide the pressure knee to the rear to account weight shift differences with changing needs or grip.  If you are running the OEM wheel stuff or close copies of the OEM stuff then you'll end up with the bias bar at about 50/50 and  the factory proportioning valve will probably be ok....maybe not optimal as your testing found but ok.  If the wheel parts have changed the factory valve is about worthless and an adjustable one like these is probably needed:

https://www.wilwood.com/MasterCylinders/MasterCylinderValves

What I do is set the valve to as little knee as possible and set the bias bar on a water dry day.  Then wait for a cold wet dry to adjust the valve.  Then wait for warm dry and recheck the bias...then wait and repeat until very little change is needed.  Not perfect but it works pretty well to make a good street street car.  Tuning brakes is really no different than tuning the engine....more fuel, more timing, more fuel....perfect, at lest today but maybe worth a data logging run up the tallest mountain in the area...check it again next real cold day....etc.  I do the same with brake setup when I've seriously messed with stuff.

Your point about race cars and race tires not being street cars is a good one and spot on right.  On the track optimal will mean more front bias...which means if you're making adjustments then its best to write your setup settings down and set the correct street settings for the brakes just like many do for their shocks so as they change back to street tires they can set the car up popery...but even left in track mode the brake system will work better on the street if the system includes a proportioning valve because at least you'll get some additional rear bias ay low pedal force.

In reply to mke :

Track changes, and condition changes make adjusting brake bias important especially in longer races or on tracks that put brakes to the ultimate test.

Here I’m thinking of Elkhart Lake, Mid Ohio, heavy brake use like those tracks that leads to brake fade can benefit  from shifting brake bias towards the rear 

Same thing in the rain or on oily slippery tracks.  But how much rear bias and which corners is something that requires a great deal of skill and experience to optimize. 

Typical knob adjustment is really lousy way to do adjusting with thick racing gloves on. Especially if it requires removing one hand from the steering wheel and reaching for a knob.  Really tough to feel how many clicks were made so you can quickly get back to baseline.  That plus some adjustments really don’t take place until the pedal is loaded and unloaded a few times.  

The optimum balance bar-proporting valve , has to be the one used in early to mid JaguarXK120’s from about 1952-55 .  In was an in-line tandem cylinder with tilt valves.  They are very rare because they used a dual tilt valve assembly  to determine bias that was instantly bias adjusting. 

Using that system I could always out brake everyone in the extremely short wheelbase Black Jack Special especially under really hard braking like going into turn 5. At Road America. 

If anyone is reading my posts and coming up with “you don’t need a prop valve” then I’m doing a terrible job of expressing myself!