Nzeder....youre looking at a rear disc conversion......have you looked at the pics and thread of mine about the Arizona Z Car conversion with my Added Mechanical Spot caliper for a handbrake ?
Yes I have seen that - I have some Porsche Boxster mono block calipers that I got for the right price so I am using these. The rear is designed for a 20mm vented rotor that is 290mm in size. I am going to use a Z32 300zx rear rotor which is 297mm x 18mm thick with a hat of 63mm. These have an internal drum ID of 172mm. So now I am just looking into a simple backing plate mod using a common Commodore backing plate. However their internal drum is 160mm so I will be looking at getting some new linings added that will take the ID out to the 172mm ie some extra 6mm of brake material on each shoe. I was looking into the VP-VQ IRS senator rear rotor as these have the 160mm drum and the following rotor spec. 280mm x 20mm with hat of 67mm but the centre hole is 70mm and PDC is 5x 120mm via the 240z of 68mm and 4x 114.3mm. The only thing that has put me off these rear rotors is that they are not that common = limited suppliers. With the Z32 rotor there are number of rotor suppliers as these are also the same rotors used on some of the Skylines (R32, R33 and R34) and other than the mod to the shoes you can order the rotors in 4x114.3 from some suppliers = no mods to the rotor.
Sorry for the slight high jack this is why I have been looking into other rear conversion to see what size hat is used on these conversion so I know what alternative rotors I could use. The 280zx S1 conversion uses a 68mm hat and this is the biggest you can go without doing other mods. So this lead me to the VP-VQ HSV IRS rear rotor and also a Subaru rear rotor which is 290x18 with 67.5 hat. The issue with the Subaru rotor is the shape around the stud axles as the Subaru has a 5x100mm PDC their rotor has a stepped design. The smallest part of the step is 129mm = no way will a 240z stub fit in here ever. So a spacer between the rotor and stub would be required. The Subaru uses a 170mm internal drum. The issue with using the Z32 shoes is their height they fowl on the back of the 240z stub so this is why I am looking at the Commodore VN/VP internal drum as they have a much lower profile. The other setup I have that does work is a 190mm internal drum as used on the new Commodores and most Falcons since the EL range - however these have a much smaller hat and this setup does not work with the Porsche monobloc calipers that I have. I could just get some different calipers but my pedal box that I have with the master cylinder has be calculated with the piston sizing for the Porshce calipers so I would be up for new calipers and master cyclinders vs a mod to the shoes.
So this is a lot of stuffing around but once I have the solution down I will be set with rear disc conversion that is using a caliper with dust seals (not a legal requirement here in NZ but I live in the country on a non sealed road = lost of dust) and an internal drum for the park/hand brake.
And with all this stuffing around etc it would have been easier to just purchase a vented kit like this
http://silverminemotors.com/product.sc?categoryId=2&productId=38 before I got the Porsche calipers and master cylinder setup.
So back on topic now guys - sorry. For a straight disc to drum conversion either of the S1 or S2 280zx conversion is a good way to go. If you want to upgrade the front brakes then you should consider a larger rear piston setup to put the bias back in a good range again. A friend here in NZ with this race car had the MM conversion on the rear ie Z31 rear rotor (290mm x 10mm with 47mm hat) and the S31 caliper. But when he upgraded his fronts from Z31/Toyota 4x4 to a 12.2 x 1.25 (310mm x 32mm) with a large 4 pot we worked out the back was only every going to via 10% max. So he modified the MM brackets (cut the ears down and redrilled lower) the install Z32 rear rotors and calipers (the MM bracket had the correct offset already...bonus) the installed a hydraulic handbrake. So I am now heading in the same path as my friend but as my car will see more of the street I am not going for a hydraulic handbrake hence all must work to get an internal drum setup to go with my 4 pots on the rear.
There I go again off topic (sort of still talking about rear brakes just not the 280zx conversion now)
So my views
280zx rear conversion = good for drum replacement for like performance.
Consider something else if you will be running anything larger than the common Toy 4x4 front conversion.
