Rotor Thickness With Aftermarket Calipers

[Luke_ENR34]

Hey guys,

Brought some 8pot brembos the other night and they come with 380x34mm rotors.

Is that thickness ok for the rear with a 6pot Brembo?

What if i went 380x32 on the front and 380x34 on the rear?

Will be running a peddle box to control bias.

Cheers

[MrStabby]

Hey guys,

Brought some 8pot brembos the other night and they come with 380x34mm rotors.

Is that thickness ok for the rear with a 6pot Brembo?

I guess you could measure the distance between then pistons when they're fully seated and compare between the two sets of calipers. If the distance is the same, then the rotor width should be the same. Only complicating factor is pad width, so check that as well. For some calipers you can order different width pads.

[PM-R33]

Pics of brakes?

[Luke_ENR34]

Fronts

Rears

[PM-R33]

Very nice.

[JAGR33]

Personally I would not run those 6 pots on the rear, piston size is way too large for a rear caliper and you will have all sorts of issues with brake bias.

Those 6 pots you have would be more than capable for the front, just look out for some 4 pot rear calipers and about a 330mm size rotor for the rear.

[Risking]

^^^

100% correct.

Those would be far to large for rear calipers. What piston sizes are they??

Let alone piston sizes but rotor size, pad surface area etc are all to much for a rear caliper.

I'd assume your planning to use decent pedalbox system but even then your going to get caught with a massively over braked car in the rear even when you correctly size the masters. You'd have to use a very low bite pad in the rear to get anything even semi decent from the front to work.

I've tried it before on several race cars for customers, large rears like that just don't work well, we spend all this time machining up adaptors and rotor hats for them only to waste it all and have to go back to something 4 piston and 350mm, if only they'd listen straight up.....

These are competition cars with top shelf Tilton pedal boxes and alot of development behind them.

[Luke_ENR34]

I'll have to double check piston sizes again.

Using a OBP peddle box http://www.obpltd.com/

Has a balance bar aswell as a adjustable cockpit knob.

What if i turn the rear bias to hardly anything? Surely there's a way to make it work.

How does other brakes work with 10 or 12pot fronts and 8pot rears?

[JAGR33]

How does other brakes work with 10 or 12pot fronts and 8pot rears?

The 8pot rears utilise a caliper specifically for that, they have much smaller diameter pistons than the ones you want to use.

As cool as it would be to run 8pot fronts and 6 pot rears save yourself the hassle, it's not worth it.

You may want to consider the weight saving using a smaller caliper and rotor aswell.....

[Risking]

I actually have some nice 4 piston rear calipers which work well on skylines and can take a 355mm rotor no problem.

They are also brembo calipers. Might suit your application better than what you have now

[Risking]

Turning bias down is only one part of tuning a pedal box.

Master sizes, pedal ratio etc are far more important.

You could get the bias reasonable with the odd sized masters you'd need ( tell me piston sizes, pad size, rotor size, car weight and I'll tell you a good master size to start) but once heat, speed, pads etc are introduced it will turn to crap with what are the wrong calipers for the job.

Those 12 pot calipers It's a wank factor of having 12 pistons which aren't needed.

Size the brakes sensibly and appropriately instead of just cause I can attitude and the car will be better for it.

[Risking]

Oh and don't use a OBP pedal box. If your going to the expense of doing it do it right and buy a tilton with 64series masters.

[Luke_ENR34]

Why not use the OBP box? Theres a few local guys using them and are very happy with them.

With our local Mallala track its probably one of the hardest tracks in Aus for brakes.

I'll be sure to drop you a pm when i measure everything.

Its really all a black spot for me.

Thanks Luke

[Risking]

Have those same guys used a tilton box??

Pedal comfort is one thing that tilton are renound for. If your planning to use a 3 pedal the throttle linkage kits are brilliant for varying throttle application speeds and pedal to throttle plate ratio's

On the 600&900 series you can adjust the pedal ratio without buying new pedals

Ive fitted plenty of pedal boxes and even fabricated my own when dollars were tight. They all flex and squirm under heavy brake applications but the tilton's seem to be

consistent and reliable.

If $ permit spend the extra on a 900 series with pivoting masters. Ive never had one bind up in the bias adjuster, they have sphericals at all pivoting joints instead of bushes and they are a robust unit.

People have their brand preferences, tilton are one of my favorites to use. Wilwood pedals are a tad nasty in my opinion they are more designed around hodrod and street custom car builds, saying that I know of plenty being used I'm circuit cars without dramas.

[Luke_ENR34]

Thanks heaps for that info mate.

I'm planning to go to a few workshops in the following weeks to see how they mount the accelerator cable, I'll try and get a few more words out of them about the peddle box to.

Just one other thing. With the Tilton boxes have you ever had to mount the seat back further?

Thanks Luke

[Risking]

Tilton have the best throttle linkage system of any pedal box I've ever used. There is massive amounts of adjustment and it's so easy to make subtle changes.

I'll take some photos of a 900series pedal set that I have on the shelf to show you what I mean. The 600 series can have the same throttle linkage fitted too.

I personally have never mounted a seat further back.

I make my pedal box platform properly with a built in foot rest and at a height that's suitable for the driver.

If you use a 900 series with pivoting 77 series masters the whole unit is fairly short.

Or use a 600 series with 74series short body masters, with the kit you can remote mount the resiviours and it's a fairly short unit too, cheap when you buy a master kit too

On my own cars If I'm using a 600series I'll use 76series short body masters with the an fittings to teflon hose to resivours. Rubber hose supplied works but if it's a race car I hate rubber hose when there is something better available

Expensive but worth it.

[Risking]

The other option you have of you are tall is an overhung box from the dash bar in the cage.

My old r32 had a tilton hanging pedal set. Masters mounted behind the dash cluster 6.25:1 pedal ratio. Works really well and factoryish pedal location.

These are my choice for any ipra circuit build I do as they have a 75mm from oem pivot rule.

[Roy]

At the end of the day, if its a show car then go for it as it will look pretty out of this world. If you want to actually stop, then sell it all/parts off.

If you want to actually stop a car quickly then brakes are only about 30% of the equation. You need sticky tyres and you need good quality suspension to control pitch of car and keep the tyre in contact with the road when stopping.

As others have said, depending on what you have planned for the car. I think 380mm brake setup is well and truly up there for people who want to be circulating for 30mins + at speed on the track with a heavy, powerful car.

I think I read that you bought that kit which was meant for a Range Rover or something so I would be checking the piston sizes ASAP and making sure you understand whether they can be made to work on a Skyline.

I personally think pedal boxes etc are a waste of time for 90% of people. Ditto bias valves etc. If you know your way around them then great. If not then most people charging you money to set them up wont really know what they are doing either. If you are running different levels of downforce for different tracks, have an 80L+ fuel cell which changes the weight bias of your car as it goes from full tank to empty and need to change the brake bias so that the braking is optimal for the duration of the session etc etc

Also, some things to consider. Rotor width aids cooling, and there is a reason why rear brakes are typeically 22mm or 28mm. You need your front brakes to be running at their operating temps just like you do your rear. Brakes convert kinteic enrgy into heat and noise and with the rear brakes not doing as much work as the fronts then they need to dissipate less energy then the fronts. This is important to remember as with a massive diameter and thick rotor your rear pads will never get up to temperature. This means poor performance and possibly excessive rotor wear, AND also the bias issues others have spelt out.

Be interesting to see which route you end up taking and your results, but personally I would be only running as big a brake as you need to run and keeping it basic unless you are doing all the worl yourself. Otherwise 8k later a car with std brakes that are sorted with good tyres and suspension will be outbraking you

[Risking]

A range rover.....

So it's like 3/4 of the big brake kits people bring me to fit to skylines.

Oh bought these from somewhere can you make adaptors....

They never work properly.

Troy is also correct about pedalboxes. Something I didn't mention.

I'd say 6/10people pay to have the pedals fitted reasonably well then try and listen to their bone headmates about masters and bias control. 2/10 pay cheap rates to fit and have some moron try and get it working for you.

The remaining 2/10 pay Someone good money to have it done with good quality gear and it works well for them.

Costs twice as much as the first two options initially but in the long run you don't end up forking out for 8 trial sets of master cylinders, two pedal boxes cause the 1st was rubbish, 4 sets of pads and 20 hours labour cause the guy trying to tune it didn't understand pedal ratio's, caliper

sizing, pad compounds etc properly

Worth considering.

[Luke_ENR34]

Thanks for all that info guys. Defiantly a whole new learning curve for me.

Havent measured the 8pots as they are still in Japan.

Regarding the 6pots the pistons are 38mm, 34mm and 30mm

Rotors are 380x34

Masters are 0.625 and 0.7

Am basically building this myself so any help towards this is much appreciated.

Setting up the Bias, balance bar will be left to the experts (which being in small Adelaide there arnt many )