4x100 drum to disc

Hmmm...interesting. I recently dragged home an '86 GT that hadn't run in 16 years as a beater.

I found a set of 15x6 Miata wheels and 205/50 tires for about the same money as a new set of one of the trailer-grade Chinese 185/70-13s currently on the market so I've got room for more brake than I'd ever care to put on this car (with five other project cars around there's minimal budget for this one.)

I've got a set of GTS calipers and '88 MR2 rotors here for the front; most FWD vehicles don't make enough use of the rear brakes for it to matter what's in back so I'll probably live with the drums.

The FX16 rear rotors are quite small and the calipers have a 30mm bore vs the 32mm GTS rear calipers, those calipers are also relatively pricey as rebuilts. The MR2 rear rotors are larger, but the MR2 rear calipers have a considerably larger bore (more than you'd want to use on a nose-heavy FWD vehicle.)

If I were going to try to cook something up of my own I would probably use the MR2 rotors and look elsewhere for a caliper, as long as it's a lug-mount caliper the brackets are the easy part, it's the parking brake cables that are nasty...

 

FWIW rear-disc Civics of a decade or so ago had 30mm pistons and integral parking brakes, I think the Saturn SC of similar vintage was 32mm, Ford Focuses and ZX2s had a 34mm piston, all of the aforementioned calipers are more common and I think cheaper than the FX16 GTS parts.

 

i would love to see the rear mr2 set up. as it is, if you notice newer fwd cars, when you brake the whole car sinks down, compared to the st162, it just dips forward. i actually think that more rear is needed. often i found with my old celicas is that the bias is too much to the front so the front dips down too much, causing not enough weight in the rear to make the rear brakes effective.

 

Forward weight transfer is a function of a fair number of things, including CG location (fore-aft and height). suspension geometry (particularly anti-dive % in the front suspension), and suspension tuning. You can slow down weight transfer off the rear wheels with stiffer springs and more rear rebound damping, but there's going to be very few FWD passenger cars where in steady-state threshold braking the rears are contributing more than maybe 15% of the total braking effort. The rear brakes are basically the feathers on the arrow, they're there to keep the rear lined up behind the front.

The rear brakes on my '91 Taurus SHO, in stock form, did basically nothing; after a 20-minute track session that'd have the front brakes cooking the dust boots off the caliper pistons you could put your hand on the rear caliper without discomfort. Even with a manual proportioning valve you couldn't crank in much more brake than that or you'd have rear lockup (too much rear brake being worse than too littlle.) The situation got a little better when I swapped to the '96+ Gen3 front subframe, which has much better wheel location and anti-dive, but I'd guess the rears are still around that 15% total contribution number at most.

The ST162 has a pretty low CG compared to many FWD vehicles, I don't know how the anti-dive percentage in the front suspension layout compares to newer designs. Mine is a 130K-mile example with completely original suspension, the springs seem a little soft and the struts are definitely on the way out.

I'll report back if I do anything to the rear brakes, but I'm not really expecting to; the few bucks not committed to the '60s project cars or freshening a 3.2 for the SHO (to, at least temporarily, replace the 3.6L experiment that hasn't quite panned out) will go to new struts first.

 

The GTS front calipers and '88 MR2 front rotors are now on my ' 86 ST161 GT. Works fine. Cut off the splash shield, as (a) it wouldn't clear the new rotor and (b) I don't have a set of GTS splash shields.

Tomorrow if time permits I'll play around with my junkyard '88 GTS struts, try to get a bit of negative camber in front and work on my home-lift alignment techniques...

 

Front GTS calipers and '88 MR2 rotors (same size as GTS but 4-lug) are on and work fine. Didn't have GTS splash shields and wouldn't have wanted to remove the hubs to install them anyway so I just cut off the old splash shields.

Got lucky - junkyard GTS front struts have healthy KYB GR2 inserts in 'em. Had to swap on my old top mounts as the GTS top mounts were rattly. Changed the steering rack boots, cranked the little camber-adjuster bushings in the hub carriers out to maximum negative, did a quick toe alignment (and then did it again to get the steering centered...) and it all works very nicely.

A strut change on this car would be not much more than a fifteen-minute job if it weren't for those !@#$%!@# brake hoses thru the tabs. Bah!

Back onto the lift, pull the rear struts out and tear them down, completely shot. Tear down the junkyard GTS rear struts, shot too. A little random searching turned up another one of Amazon's random pricing imponderables - a Monroe 71824 at $15 and a 71825 at $23. So the car is stranded on the lift until they get here.

Historically, Monroe's US products have been nothing to write home about, but their Sensatrac/OESpectrum stuff for Euro cars was, last time I looked, coming out of a plant in Belgium that does Euro OE applications and I know a few BMW owners who've had very good luck with 'em. I have no idea where the Celica pieces come from, but they have to be better than what was on there.

Oh, and one other thought if anyone were inclined to try to staple together their own four-lug rear discs - the '94-02ish base Miata rear calipers are the right piston bore (32mm) and have an integral parking brake. Still think the hardest part of the whole thing is the parking-brake cables...

 

And the answer is...Spain.

One of my Amazon Monroes came in a Sensatrak box, the other in an OESpectrum box, but in every respect other than the printing on the box they look identical. They went in easily enough, and work very well.