Brake Upgrades Performance and Weight
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Author:  AlanDatsomefun [ Wed Dec 07, 2016 3:43 pm ]
Post subject:  Brake Upgrades Performance and Weight

Brake upgrades to 296x30 with 4-spot calipers, or other fairly spectacular swaps are not new. Each satisfy the main need, put your foot on the brake pedal and your car stops more quickly than it would with standard brakes - very important if you have an engine that is putting out heaps more power than the original 96Bhp for a Datsun 1600 / 510, for example. EVERY upgrade I have seen adds weight, sometimes lots of weight. It is not uncommon for the weight increase to be 3-5 kg per side. Add bigger wheels and the weight starts to add up: could be 7-9kg per side. BDA Escorts, for example, commonly had aluminium alloy hubs. You'll find alloy hubs and brake hats and, of course, alloy calipers, on Porches and such. Why not on the humble datto? Is this just a matter of cost, or am I missing something else. Would you go down the the lightweight alloy hub, mounting ring / hat, alloy calipers and perhaps narrower but lighter ventilated discs (which would work about as well but much lighter). DBA make some very good 5000 series rotors, say 296x25, that could be adapted to a custom alloy hub and special (?) or modified alloy calipers. These could save 3kg per side over the standard R31 250mm via rotor setup - makes a lot of difference to braking stability, and suspension response = better handling. DBA Comments ... anybody?

Author:  SR20Datsun [ Thu Dec 08, 2016 9:36 am ]
Post subject:  Re: Brake Upgrades Performance and Weight

I've always wanted to get a rotor with an alloy hat, but then realised the weight savings was fairly negligible for the rotors I was using.
I think there would be a good saving with appropriately sized hubs in either a stronger material, or a lighter material.
I think Lampy here used 4140 to make up his hubs on his 1600. Less material, stronger and lighter.

I think running factory stuff makes it easier to buy bearings, spare parts etc. But I guess if you are chasing the 10/10ths then custom is the way to go.

Author:  AlanDatsomefun [ Thu Dec 08, 2016 11:27 am ]
Post subject:  Re: Brake Upgrades Performance and Weight

Thanks, I like the idea attributed to Lampy of using Chrome Moly alloy steel rather than aluminium alloy because it has a much better fatigue life and a really well designed alloy steel hub would be only slightly heavier (if at all) than an aluminium alloy one, but will last and potentially SAFER. Alloy hubs should be scrapped and replaced at around 80,00km. Absolutely no argument: custom is costly. I have gone down the Aluminium alloy custom route for hub and hat/mounting ring and DBA5000 series rotor. Impressive weight savings are possible compared to: R31 OEM 250mm brake / hub - custom setup is lighter by 3kg and has 296mm rotor; Datsport 296x30 rotor with S12 steel hub and 4-spot caliper, custom setup is lighter by a tad over 4kg. Again, the nagging question is: ... " is it worth the effort?" Quick reckoning of cost (not counting my time and effort to design them): Custom alloy hub $475 ea, alloy mounting ring $125 ea, DBA rotors (incl NAS nuts) $235 ea, R33 calipers including rebuild and some modification $255 ea, NAS titanium bolts $25, bearings and seals $25, ARP studs $85, TOTAL = $1,225 per side for 296mm diameter ventilated disc and 4kg in reduction weight. This is yet to be judged in terms of: braking effectiveness, steering and handling stability under brakes, and ride. Note that this project started off as a 5-stud conversion.

Custom Rotor-Hub setup.jpeg
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Author:  Brendan [ Sat Dec 10, 2016 3:26 pm ]
Post subject:  Re: Brake Upgrades Performance and Weight

Have you thought of using s13 280mm rotors with a modded r32gtst caliper if you shaved some thickness out of the caliper to use the lighter rotor you would be saving weight while still using factory parts, I would going to use the r32gtst cailpers and rotors then worked out how bloody heavy they are and going back with S13 or HR31 setup

Author:  AlanDatsomefun [ Tue Dec 13, 2016 9:32 am ]
Post subject:  Re: Brake Upgrades Performance and Weight

Thanks. I had a look at using a two piece 280x30 rotor with a Z31 Californian hub (because I wanted 5 studs), but a HR31 hub with a single piece rotor works out about the same weight if you are keen to use Sumitomo 4- spots). Both these options weigh in at about the same as the standard R31 cast hub/rotor setup. Using HR31 rotors and calipers is actually a good way to go and is somewhat lighter, mainly because the rotor, being somewhat thinner, is lighter. 30mm wide rotors are damn heavy. In 296x30 size these are about 8kg: make good boat anchors. Alloy hats and rotors I have used weigh less than 6kg. If you are chasing a big weight saving, that is to be found in using an alloy hub. Skimming a couple of millimetres off each half of a 4-spot caliper to suit a 25mm or 26mm rotor, rather than the Nissan 30mm, is a precision machining job, because the cross-over galleries of the two halves meet at strange angles (about 60degrees) to the mating face. Best option is to take the required 2.0mm or 2.25mm off each half of the caliper, and re-position the O-ring recess (12.6mm diameter and 1.6mm deep, from memory): CAUTION: if these galleries do not line up EXACTLY, your brakes will NOT work, and if the two mating faces are not exactly square and parallel, and the O-ring recess not machined properly, you could have leakage or the pistons not exactly at right angles to the pads. You CANNOT skim the total amount from one half of the caliper only. Seriously, whilst I have done it, modifying calipers is NOT the recommended option. I reckon there is a really neat option out there - one that uses a DBA5000 series rotor with a light OEM caliper (both around 25mm) and a custom hub with an integral mounting ring/hat - and whole thing could be both light and cost effective?

Author:  SR20Datsun [ Tue Dec 13, 2016 10:03 am ]
Post subject:  Re: Brake Upgrades Performance and Weight

I thought you could get Z32 (non turbo??) callipers which from memory (and it's a bit hazy) had a rotor thickness of 28mm?

Author:  AlanDatsomefun [ Tue Dec 13, 2016 1:37 pm ]
Post subject:  Re: Brake Upgrades Performance and Weight

Yes, and yes: I believe you are right.

Author:  RJB510 [ Thu Dec 15, 2016 8:11 pm ]
Post subject:  Re: Brake Upgrades Performance and Weight

Why not just use S13 (the 180sx SR20 Turbo) turbo rotors and brakes. They are 28mm from memory, they are 4 stud not 5 and the calipers are cross slide twin piston (from memory) rather than sealed 4 piston z32 units. But they brake quite efficiently i thought and having less pistons will require less braking effort.
Should make for a light and solid brake setup with easily replaceable parts? I think a lot of 1200 guy's go down this route, i'm surprised that its not more common on 1600's.

Author:  Woznaldo [ Sun Dec 18, 2016 6:26 pm ]
Post subject:  Re: Brake Upgrades Performance and Weight

Something that needs to be considered is the optimum brake temperature. It's no good fitting these big rotors if they aren't getting up to temp. Wilwood sell two piece rotors in fairly thin thicknesses that might meet the required end goal.

As an example, a friend who runs a light hillclimb car (700kg hatchback) went to solid rotors as his vented setup didn't get up to temp in the 45-90 second runs he was completing. The switch to solids allowed temps to climb quicker and saved unsprung mass. Obviously hillclimb is fairly short and gravity is also assisting with the braking, but the point about temps is still relevant.

Author:  AlanDatsomefun [ Mon Jan 23, 2017 1:40 pm ]
Post subject:  Re: Brake Upgrades Performance and Weight

Good point. At the other end of the scale, large commercial aircraft and certainly fighter aircraft have several solid discs at each (under wing) wheel: these get very hot very quickly and don't get a chance to cool down during operation, but only have to work for a few seconds at at time.
In the 12 kilometre downhill Tawonga Gap stage into Bright in the Alpine Rally, for example, it's common to get brake rotors red hot and have liquified wheel bearing grease ooze out past the wheel bearing seals. Wheel bearing grease fails at temperatures above 150 degrees C, but rotors can easily exceed 815 degrees C ( i.e. glowing light cherry red). That is a situation where ventilated front discs are essential. Under these circumstances the front brakes are required to do some 80% of the braking work.
If brakes do not get hot enough you can have other problems: If you have ever had to cope with competition pads in cold weather when driving to work, you quickly discover the meaning of "scary": hit the brake pedal and nothing much happens ... for what seems to be a very long time.
Also, there is no point in carrying around a whole lot of excess weight just to say you have the biggest brakes.
If you have a quick car that has to stop frequently from speed, then ventilated discs make a whole lot of sense. For example a Lotus Exige used on the track well needs 296 x 26mm ventilated rotors all around.
RGB510 suggests, 280x28mm ventilated rotors with 4-spot calipers and good pads, would be a good choice for a Datsun 1600. You would have to be going seriously hard in a 1000kg car to exceed the capacity of a set of these. If your car is a high performance rocket with 1500kg curb weight, then you will need bigger brakes. If you race a hill climb car and don't use the brakes much, then smaller solid rotors will do.
One advantage of running largish ventilated discs is that you can use "standard" compound pads to give good response. Another advantage of largish ventilated discs is that because it is unlikely that you will overheat them and they will remain stable and undistorted. Stable braking means driver confidence.

Author:  SR20Datsun [ Mon Jan 23, 2017 3:21 pm ]
Post subject:  Re: Brake Upgrades Performance and Weight

Everything is a compromise.
I agree with you Alan, and my setup is a pretty good case in point. My pads aren't full blown race pads. I am running quite large rotors (296), but sometimes I have been known to pass a Lotus...
The pad/rotor/calliper combination that I am currently using in my 1600 are a good for street/track. I know it sounds wrong, because you never can have both as you will always compromise one. A good street pad is a very poor performing track pad due to the vastly different operating temperature ranges.
So the pad I have has pretty good performance for every day street use. Ramp up the temperature and they get better. The Coefficient of friction is actually very good for a street pad as they are (when not up to temperature..) I don't get that crazy put the foot down and nothing happens.
On the street/track I have seen up to 1.1g braking capacity when hot. Cold isn't as good, but you can guarantee it is still bloody good.
Anyway the reason I am saying all this is the brakes that I have mean I can drive the car to the track and then go hammer and tongs without changing anything (except for tyre pressure!). I'll take a spare set of pads, but they are the back up in case I chew through them.
Pad wear is excellent.
I'm only doing sprints (so 15 minutes max at a time with about 5-6 sessions). Doing an enduro style would probably mean I need to get some ducting happening...Then I need different pads.. Off we go again.

Author:  lampy [ Mon Jan 23, 2017 4:57 pm ]
Post subject:  Re: Brake Upgrades Performance and Weight

The hubs I made were 6061 t6 aluminum. They weighed in about half the originals.
The hard thing was getting the right press fit on the bearing. Hubs can get very hot as Alan has mentioned above. Would be bad news if the bearing lost it interference fit when using the silvia style hubs
Didn't get around to machining some 4140 hubs. You would have to do some serious thinking about the forces involved if reducing the thickness. Need to utilise solidworks or similar I would think


Author:  Woznaldo [ Thu Jan 26, 2017 11:01 am ]
Post subject:  Re: Brake Upgrades Performance and Weight

Aluminum Uprights would save a lot of weight and is what you'll commonly find on high end rally cars. The cost of making these parts is high! Designing, Raw Material and Machining all cost. I'm lucky enough to have access to Catia (a CAD program) and it's a fantastic tool, but I'd still to pay for machine time.

Author:  AlanDatsomefun [ Wed Feb 01, 2017 1:38 pm ]
Post subject:  Re: Brake Upgrades Performance and Weight

Thanks for the interesting discussion. This brings out some of the challenges with designing and fabricating aluminium components. My comments relate to hubs designed to fit R31 / HR31 struts: each hub has one large tapered roller bearing inboard and one smaller tapered roller bearing onboard on the spindle. Later models typically use large, very wide double row bearings. Regarding the installation and subsequent removal/replacement of bearings into aluminium alloy hubs, the following suggests how. Calculate the desired interference fit between the bearing race and hub at an operating temperature of 150 degrees C, which is the practical upper temperature limit for continuous operation of the hub. For standard size bearings, say, NTN 4T-LM67010 (inboard) and NTN 4T-LM11910 (outboard) or their equivalents, the interference fits are significant. Pressing the races into an alloy hubs with very tight fits comes with a high risk of damage to the hub. Here's what you will need: a quantity of liquid Nitrogen, an oven, appropriately sized tapered drifts for installing the bearings, a hammer, a couple of short lengths of timber dowel to which some wire or thin sheet metal can be attached and safety gear including insulated mits used for furnace work, and full face shield. CAUTION: BOTH EXTREME HEAT AND EXTREME COLD CAUSE SERIOUS BURNS!! Take one hub and heat in the oven to 200 degrees C. Install the outer race of, say, the inboard bearing onto the piece of dowel ... held in place lightly with the wire or piece sheet metal (use a screw to attach the wire or sheet metal to the dowel to keep it in place). The bearing race should be installed on the piece dowel - this needed to get the bearing race into the right position so it can be installed into the hub. Imagine the dowel standing upright with the wire or thin sheet metal at the lowest point ... place the bearing race with the widest part of the taper pointing downward. The piece of dowel will be your tool for firstly placing the bearing race into the liquid Nitrogen to get it cold (nearly minus 200 degrees C). When it is cold, withdraw it from the liquid Nitrogen and feed the free end of the dowel up through the hub (which you have just removed from the oven). This will pre- position the race for what follows. Carefully invert the hub ensuring that the race is held roughly in position. In preparation for using the drift and hammer to tap the bearing into place, carefully turn the hub over so the bearing is now uppermost pull the dowel down and through so it just releases the bearing race ... hold the bearing in position with the right sized tapered drift before QUICKLY and carefully tap the race into its home position. Initially, when the temperature difference is around 400 degrees C, the race will be a loose fit in the hub, BUT the heat transfer occurs quickly and if you waste any time the bearing race will get stuck part way in. Best idea is to have a few mental rehearsals before attempting to do this for real. It's easy to do, but you must be prepared and move quickly and confidently but not hastily. Repeat until each of the outer bearing races are installed. Once the bearing races are installed this way they are NEVER going to come loose during operation. Whilst compressive "hoop" stresses are very high, this will cause no damage to either the bearing race or the hub. IF you ever need to remove a bearing race to replace a bearing (unlikely, because if the bearing has worn out your hub has probably reached the end of its fatigue life anyway), you will need an arc welder. Simply run a good thick bead of weld along the inner face (the surface where the rollers run). This should be 25mm long or so, repeat two more times, leaving a gap between runs. Leave to cool down to room temperature and carefully tap the bearing race out from the inside. If you have not provided recesses so the back face of the bearing can be accessed, you will need to weld a piece of steel rod or similar to the bearing to use as an extraction tool. If you have been careful when welding, there will be no damage to the hub and the old bearing race will come out with just a little pursuading. For the standard bearing sizes mentioned, the recesses in alloy hubs made of 6061-T6 or, say, 5083 will be 59.05+0.00,-0.05 and 45.20+0.0, -0.05 millimetres respectively. If you choose to make hubs out of steel CrMo 4140 or similar, just use the same sizes for the bearing recesses as OEM cast iron hubs.

Author:  AlanDatsomefun [ Tue Jul 10, 2018 11:51 am ]
Post subject:  Re: Brake Upgrades Performance and Weight

Like so many things, alloy hubs are not a new idea. Of course, there are important considerations regarding choice of alloys: have to be light and strong but not horrendously expensive and here are a number of significant engineering design and fabrication issues with alloy components, as indicated above.
When it comes to everyday use in cars, there are really two issues: cost and cost. Compared to cast iron, aircraft grade aluminium alloys are very expensive. It is difficult to impossible to predict when a highly stressed aluminium alloy component is likely to fail. Possibility of premature or unexpected failure of a brake hub is a serious matter. Replacing bearings is largely impractical for most workshops, so the best strategy is to design the hub so that bearings never have to be replaced. The result is an expensive, throw-away item, that must be routinely replaced well before it is likely to fail.
Back in the late-1970s factory prepared Group 4 Ford Escort BDA RS1800 rally cars used alloy front hubs.
In the 1980 Southern Cross International Rally, whilst I was engaged in a mid-field battle for Group 1 honours, Greg Carr was in a battle for the lead in a factory-backed Escort RS1800. He might have won outright Gp4 except for a "brake failure" that caused the left front wheel of his BDA Escort to lock solid.
He continued on regardless, demolishing the tyre and grinding the wheel rim and brake rotor down flat, right down to the edge of the hub ... I recall there being much excitement in the Ford camp ... and he still managed to finish 2nd outright.
It is not really clear whether the bearings in the hub seized because of lubrication failure and overheating or the stub axle was bent when Greg hit a bank, or ... ? Greg or team manager Colin Bond would know.
There is no doubt that the alloy hub was strong: it did not shatter or break despite this incredible punishment.
How frequently were these hubs replaced? I'm guessing that for rally competition at this level they would be replaced after 5,000 kms or at the beginning of each season (each year), whichever is sooner.
If you have a new BMW 'M2' or a Porsche 911 with alloy hubs you might know what the manufacturer's maintenance strategy regarding these items?

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GP4 Alloy Hub.jpg [ 27.03 KiB | Viewed 1118 times ]

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