Jump to content
Sign in to follow this  
zzzzed

R31 vs 280zx rear brake calipers

Recommended Posts

Some one on a different forum told me that r31 skyline rear calipers are garbage. I have a set of 280zx rear calipers would I have been better off fitting the 280zx calipers?

Share this post


Link to post
Share on other sites

Some one on a different forum told me that r31 skyline rear calipers are garbage. I have a set of 280zx rear calipers would I have been better off fitting the 280zx calipers?

 

Hi Mick, can't comment on the 280zx rears as haven't used them but I have R31 rears on mine and they are OK.  There are certainly better options out there but the R31 setup is a straight bolt on with the right brackets.

Roger

 

Share this post


Link to post
Share on other sites

I think that depends on what exaclty you want the calipers to do?

 

Eg, trying to use the handbrake to initiate a drift in a R31 skyline is a bit of a futile effort, the stock calipers are garbage and dont handle that abuse well at all, the handbrake adjustment goes out the window and you end up with a park brake that wont hold very well even when parked.

However, for a 'proper' setup (not that stupid drifting) they work quite well.

Share this post


Link to post
Share on other sites

280ZX calipers have MUCH smaller pads i have both at home and compared them and you would be much better going with R31 in my opinion.

Share this post


Link to post
Share on other sites

Aren't 280ZX a bolt on with the right brackets also?  ::)

 

 

yes but the brackets are $200 from ROBCO

Share this post


Link to post
Share on other sites

yes but the brackets are $200 from ROBCO

Regardless the price.

I was highlighting the statement about R31 rears being bolt on.........  with the right brackets.  ;D

 

Just put some Brembo's on Mick...... they are bolt on........... with the right brackets!  :P

Share this post


Link to post
Share on other sites

If you add up the R31 brake conversion on ebay prices including new pads, kits, rotors and having the machining done you'll come in around the $500 mark. You're half way to having an arizona z car rear brake set up delivered.

Share this post


Link to post
Share on other sites

And at the end of the day they dont provide anything substantial in the way of braking power upgrade!

Share this post


Link to post
Share on other sites

Aren't 280ZX a bolt on with the right brackets also?  ::)

 

See my post below  :-*

Hi Mick, can't comment on the 280zx rears as haven't used them

 

What would be a better option up from the r31 then?

 

This might be a good setup but again, I have no personal experience

http://silverminemotors.com/Stage-4-Rear-Big-Brake-Kit-Stage-4-Rear-Big-Brake-Kit.htm

Roger

Share this post


Link to post
Share on other sites

I have R31's they seem fine on track but if I did the conversion again I'd definately go r32 or 300zx. There's nothing worse than winding caliper pistons in, it sucks. If you want the handbrake to work with the standard cable you have to mount them at 9 or 3 o'clock position... This means you have to remove them from the bracket to bleed properly, very painful.

 

 

 

Share this post


Link to post
Share on other sites

I think I will run the r31 calipers for a while as I have already fitted them up. And upgrade later after I have it on the road

Share this post


Link to post
Share on other sites

I think I will run the r31 calipers for a while as I have already fitted them up. And upgrade later after I have it on the road

 

Let's not let this thread end here!  Too much yet to clear up.  :P

 

What other "bolt on" brake upgrades are there for rear?  How well do they stop compared to each other and which have handbrake issues.

 

Also, which brake combinations do and do not require a proportioning valve?

 

From what I have understood so far, the list for rear starts with stock drums, 280ZX disk, R31 disk, R32, 300ZX, AZ Car Wilwoods.

 

Surley R31 disks would be a HUGE improvement over stock drums. I doubt whether you would feel the need to upgrade again Mick.

Share this post


Link to post
Share on other sites

I put VT Commodore calipers on the rear of mine, but mounted to a VS anchor bracket and backing plate. The anchor and backing plate bolts where the original drum brake backing plate mounted to, and the park brake is a drum set up inside the rotor. The service and park brakes are independent, and i far prefer a drum brake as a park brake...the self energising design is superior to stop your car rolling away compared with a disc setup that is entirely dependent on park brake cable tension to function. I used HSV VS vented rear rotors. I have GT3 Brembo calipers and rotors on the front, and a 280ZX 15/16" master cylinder. Now this was all a fair bit of messing around to do, so not for everyone, but the point of the story is about choosing rear brakes.

 

Caliper selection is partly piston diameter, partly pad area and mostly your required needs. When i first did the conversion i used the VS calipers, with a 36mm piston. With sticky 235 rubber on the back, these calipers could not stop the tyres...with full rear bias (from the adjustable proportioning valve), I could not lock the rears even if I tried (note locking rears is NOT desirable...it's best for the front to lock first)....the point is I couldn't do it because I didn't have enough braking effort. That is why i went to the 44mm VT calipers. These can easily lock the rears, and hence i can use the proportioning valve to balance the car, and achieve max rear braking effort short of creating lockups.

 

Pad area is the next consideration. When the pistons clamp the rotor, the same force is transmitted to the rotor regardless of pad area...it is just spread over a greater area (to change the force, you need to change the piston diameter, NOT the pad area). Consequently, provided the pad friction coefficient is the same, different size pads will produce similar braking effort for the same pedal force. What changes is pad heating and wear rate. Small pads concentrate heat more and hence get hotter, and will wear faster. The temperature change also affects their coefficient of friction (depending on the compound, it usually goes up as the pads heat up, and at some temperature they go off, lose their C of F until they overheat, disintegrate and fail.

 

So...choosing the 'right' caliper is about the application. If you are racing, you need to be able to dissipate a lot more heat than in a road car...so big enough to provide adequate braking effort as well as resist fade for the duration of the race are the constraining factors. For a road car, heat dissipation is a much smaller issue as you can't go fast enough for long enough to repeatedly put heat into the brakes...remember that the heat energy the brakes need to dissipate comes from the engine, so if you're not working the engine hard, you're not working the brakes hard either (unless you're coming down a very long hill). So for road applications, choose brakes that are adequate to stop the rubber you're running, offer good pad selection, adequate size to resist road car fade, and balanced against the master cylinder and front calipers you're running. You don't need super duper brakes on a road car unless you are chasing a higher impression ratio. Sure they look good, but you don't need them and they add cost and weight if you overdo it.

 

Jamo

 

 

 

Share this post


Link to post
Share on other sites

Well I would one day like to fit wilwoods to the rear

So I have them front and back.

So do r32 skyline and 300zx rear calipers have hand brake or are they in the drum? Could a hydraulic hand brake be run to combat this issue?

Share this post


Link to post
Share on other sites

I'm not sure about the configuration of the handbrake on R32's. Hydraulic handbrakes are a race (rally) car thing...from memory, the ADR requires the handbrake to be independent of the service brake, so I don't think a hydraulic handbrake would be legal on a road car. You can use a caliper with an integrated handbrake, but the packaging of the cable can be tricky (but not impossible)...

Share this post


Link to post
Share on other sites

R32/Z32 brakes are the same setup as above with the drm backing plate.

 

Excellent post Jamo lots of good info there. I know I will be doing a similar set up to yours but with Z32 setup. There is an article on hybridz.org on how to do it.

Share this post


Link to post
Share on other sites

XF falcon rear brakes could also fit as a rear disk conversion and are larger than r31. I dont have much info on them other than that they use the same handbrake arrangement as r31 and only require redrilled disks and modified brackets to fit onto an r31. Using my manbrain and logic it shouldnt be a difficult conversion... right?

Share this post


Link to post
Share on other sites

Pad area is the next consideration. When the pistons clamp the rotor, the same force is transmitted to the rotor regardless of pad area...it is just spread over a greater area (to change the force, you need to change the piston diameter, NOT the pad area). Consequently, provided the pad friction coefficient is the same, different size pads will produce similar braking effort for the same pedal force. What changes is pad heating and wear rate. Small pads concentrate heat more and hence get hotter, and will wear faster. The temperature change also affects their coefficient of friction (depending on the compound, it usually goes up as the pads heat up, and at some temperature they go off, lose their C of F until they overheat, disintegrate and fail.

 

Jamo, I need some help to understand this.  :o  My manbrain tells me that braking force will be determined by the amount of friction created at the disc surface. I would suggest - and I'm not an engineer or a physisist - that size of pad would be a significant contributor to the friction equation.  Obviously keeping pressure and pad material constant then pad area would make a massive difference.  I take your point that if you can increase pressure it will improve braking force, but I can't get my head around that different pad size will not affect braking force.

 

A little experiment that I did as I was trying to work this one out was:

 

I placed the pad of my middle finger lightly on my desk and dragged it towards me.  I then placed my whole hand on the desk, with as close to the same force (arm effort) and dragged that towards me.  Obviously this is a huge increase in 'pad' size, but the friction increase (resistance to drag) was substantial.

 

Please help me to understand.  I promise you that I am not taking the pi$$, I really do want to understand.

 

To the rest of you - stop dragging your hands across your desks and get on with your work!

Share this post


Link to post
Share on other sites

Jamo, I need some help to understand this.  :o  My manbrain tells me that braking force will be determined by the amount of friction created at the disc surface.

Please help me to understand.  I promise you that I am not taking the pi$$, I really do want to understand.

 

Total clamping force is a factor of pressure on a given surface area (say pounds per square inch) muliplied by the total surface area.  Keeping the piston pressure (force) constant and increasing the pad surface area certainly increases the fricton area but there is less pressure per square inch so the overall clamping force remains the same.

 

The only way to increase the braking force is to increase the pressure at the piston or to make the disc diamter larger and move the caliper outwards increasing the brake torque.

 

So what are the benifits of a larger pad?  Better temperature control as each square inch of pad is doing less work, better pad life (same reason) and less tapering or uneven wear over the pad area.

Roger

 

Share this post


Link to post
Share on other sites

Something that might help explain it a bit more for you:

So in Roger's example the thing to take into account is that it is using a constant size piston(s).

 

So if you have a caliper with pad of size 'A' and piston size 'B' and you have another caliper with a pad of 2 x 'A' and a piston size of 'B' you get the case that Roger has given. This is not what is happening with your hand experiment, because if you pushed as hard as you could on one finger you would break it, unlike your palm. You can however feel the difference in heat dissapation over the larger area.

 

So tying it together:

If you have a caliper with both a pad 2 x 'A' AND piston size 2 x 'B' you can exert the same amount of pressure over the greater area - which is like your palm on the desk as you can push harder on your hand than you can on your finger.

 

 

Funnily enough at the end of all this R31 rear calipers do have a bigger piston than the 280ZX i think so there you go. I'll check later.

 

 

Share this post


Link to post
Share on other sites

Hey MaygZ...the other lads have done a pretty good job of explaining it, but I will add the formula....

 

The formula for braking force (F) is given by: coeficient of friction (u) x clamping force (N). F = uN. Braking force is the tangential force of retardation that the brakes create...this can then be translated into a torque figure for the purposes of determining whether the braking torque is sufficient to stop a tyre (lock up), and then a braking power figure (by introducing rpm) if you want to determine the power the brakes are dissipating at any given speed....we won't worry about all that for now.

 

u is the coefficient of friction, and is a function of the surface characteristics of the material. Brake pads are commonly in the 0.3-0.5 range. Note that u has no units...it is a constant, and therefore applies regardless of area. In the context of your finger vs hand comparison, we would assume that u for skin is the same whether we are talking about your finger or your whole hand!

 

N is the force in Newtons applied by the pads on the brake rotor surface. In the case of brake pads, the force is applied via the piston, so if the area of the pad is larger, the force being applied to it is identical via the piston, so the force it applies to the rotor is identical, just spread out over a larger area. It is the force component to the equation that takes into account the area of the pad (it's an inverse relationship...greater area = lower force).

 

So, using our formula, if we assume u = 0.4, and we applied say 800kgf to the pad via the piston, this would be the equivalent of 800 x 9.81N = 7,845N.

 

Now F = uN, so F = 0.4 x 7,845 = 3,138N, or 318kg force in a tangential direction. To convert this to a braking torque, we can take the radial distance the force is being applied from the centre of rotation (let's assume 150mm), then the torque in Nm is 3,138 x 0.15m = 470Nm.

 

While there are a number of factors that interact and effect real world braking performance, hopefully this helps you understand why the pad area does not relate to braking force. It relates to power dissipation, pad heating, wear rates, tapering and stuff like that.

 

Cheers

 

Jamo

 

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×