A 5th Gen Front brake story, 5gc big brake upgrade for the 6gc Options

[Kwanza26]

As some of you may know... the later model (92-93) 5th gen Celica GT and GTS (minus the vert) wear some fairly decent sized front brakes (277mm diameter vs. the 6th gen ST's 254.7mm diameter rotors and the 6th gen GT's 275mm diameter rotors). There was a 1/2 price sale at a local pick and pull so I picked up a pair of front calipers and brackets from a 92 Celica GT and had been saving them for a while now as an upgrade in size to my Celica ST's dinky brakes. It's purely cosmetic... and was cheap, so I went ahead and did it.

I finally ordered some rotors last week and today went ahead with the install. Low and behold... there was a difference. The 5th gen Rotors did not sit flush on the 6th gen hub because the bore on the center hub of the 5th gen was much smaller than the 6th gen. After some test attempts, I got out a caliper and measured the bore diameters on the 5th gen GT (or GTS) rotor and the stock ST rotor. Sure enough... almost a 1mm difference. I believe it was something like .8mm difference... but yeah... enough that the 5th gen rotor did not sit flush to the 6th gen hub. After a few calls to local machine shops... I ended up whipping out our porting tools and after a few minutes... I had the 5th gen rotors sitting flush to the 6th gen hub. Next... was the calipers.

The 5th gen Calipers do bolt-on to the 6th gen knuckles without much problems, and the spacing between the spindle and the caliper was correct that the rotor's diameter fit as if it was stock. The problem was... after I tightened down the calipers, they were offset wrong and ended up touching the rotor, glueing it in place. After some quick thinking... I added some spacers (simple washers) between the knuckle and the caliper brackets and voila... perfect fit. The Stock ST brake lines then bolted on and everything was set. System was then bled and the car ran and stopped great.

So all in all... we all learned today that the 5th gen Calipers are ALMOST direct bolt-ons... and the rotors are ALMOST direct fit. It will take very little work to get them all together... but in the end... it works like a charm. I would imagine the same issues may be present for any or all of the other possible big brake options for the 6th gen Celicas (7th gen Big Brake kits, Scion tC Big Brake kit, etc...) Experiment and share the info... =]

[Galcobar]

You cannot quite use the fifth-gen rotors on the sixth-gen. As Kwanza discovered, the centrebore is smaller, 54mm on fifth-gens to 55mm on sixth-gens.

For 5SFE-powered Celicas:
Front rotors
90-91 255 mm diametre, 22 mm thick, 54 mm centrebore
92-93 277 mm, 25 mm, 54 mm (same as 90-93 All-trac)
94-99 275 mm, 28 mm, 55 mm

Rear rotors
90-93 269 mm, 10 mm, 54 mm
94-95 269 mm, 10 mm, 55 mm
95-99 269 mm, 9 mm, 55 mm

That bore difference is probably how Jeff cracked his rotor. Basically, the fifth-gen GT/GTS got the All-trac brakes in 1992.