S8 brake booster +/- master cylinder

[KYPREO]

Hi

I'm looking out for a s8 brake booster as part of the brake conversion on my series 3 RX-7. I might consider earlier FD as well (which I am told will also fit), but I understand the s8 booster is a bit more compact.

Preferably I'd like a master cylinder too, but I may end up buying a new one for piece of mind.

I have a number of potential brake booster/master cylinder options available, but I'm hoping the FD solution might be best bang for buck.

I'm located in Melbourne, Victoria, but willing to consider shipping from interstate at my cost.

Please PM if you can help out.

Thanks!

Greg 8)

[Suprspt]

Have several S6 boosters, probably $100 with master? If you want the S8 ones, bet James has a few...and understand he's got another car coming shortly too.

Bit dubious about running secondhand hydraulics. Did find Rockauto was cheap for non-oem masters, bought a 1" from them a while back for less than a standard rebuild kit from memory, vaguely remember the removed reservoir didn't have the feed for the clutch - which might be handy in your application.

[KYPREO]

Great, thanks! Still keen on a s8, but will let you know if I go for the earlier ones. I'm still trying to figure out exactly what the difference is and whether a s6/7 version will fit.

I agree about the masters. At the very least I would be getting any master rebuilt and resleeved. If I went new, I would have to go aftermarket. The OEM FD masters are ridiculously expensive.

[Suprspt]

Been decades since I've asked, but seem to recall it was only cast iron stuff that can be re-sleeved...done that for both clutch items as this modern iron is worse for pitting than even old 1970s Mazda hydraulics for some reason.

Haven't seen him on recently, email James - [email protected]. There's not a huge startling difference in the size of the boosters, if I can remember and get over there in the next day or so, I'll see if I can run the tape over one of them.

[Ceylon]

Just FYI, all models post December '95 had the later smaller brake booster.

[KYPREO]

Thanks for the info guys. I really appeciate it.

I'll have to look into this further. If I can't resleeve the FD master, a series 3 booster and master might be better after all. After all, the s3 ended up with the same size master cylinder as series 4 turbo models, which also had the same size calipers as the FD (which is what I'm using on my s3).

[Suprspt]

Measured a couple of boosters, surprisingly there's a later booster in the car, which I think came from a S7 car Phil Ward crashed at Clipsal years ago. Bit rough and ready and parallax error no doubt, diameter at the firewall is around 210mm on one and 225 on the early. The master cylinder side is around 170 v 210mm, so a bit smaller than I thought!

There's 6 masters there, a couple that are disassembled show a bit of wear where the steel washer sits behind the main shaft seal, the bores seem very good where the pistons bear. Pic of the reservoir with no clutch nipple.

Suppose the other thing to consider is pedal ratio, dunno what's on the S1~3, FD is around 70mm from pivot to pushrod and somewhere around 300mm pivot to centre of pedal pad.

[KYPREO]

Champion! Thank you for very much for this help. Good point about pedal travel too. Time for me to get measuring....