12" or 13" rears?

[Jasons68]

Hey all,
I have been looking into adding rear disks using a Kore3 kit on my 68 camaro. I currently have 13" C5 brakes up front with the s10 master cylinder, proportioning valve and hydroboost.

The price difference is negligible between the two kits (12" & 13") but I am thinking 13" on the rear may be too much and result in undesured lock-ups. Does current wisdom still say the rears should be smaller than the fronts? Can the 13" be safely used?

Thanks
Jason

[jpgolf14]

Hey all,
I have been looking into adding rear disks using a Kore3 kit on my 68 camaro. I currently have 13" C5 brakes up front with the s10 master cylinder, proportioning valve and hydroboost.

The price difference is negligible between the two kits (12" & 13") but I am thinking 13" on the rear may be too much and result in undesured lock-ups. Does current wisdom still say the rears should be smaller than the fronts? Can the 13" be safely used?

Thanks
Jason

There are examples out there of OEM cars using larger rear rotors than front.
2010+ SS Camaro
89-92 F Body

What you really need to do is match the torque bias ratio front to back. If you plan to run an OEM prop valve, I would run the same bias ratio front/rear as that car used. This means considering the rotor size and the piston size. So yours is an S10 prop valve? what year?

[Jasons68]

No the prop valve is an aftermarket adjustable type. Sorry I wasnt more clear on that. I

f I recall the year of MC is 1988. I have taken a few years off from the car and hope to start fixing her up again! Some of the thing I knew off the top of my head a few years ago arent so clear any more!!

Is there a formula or calculator to help match the torque bias ratio? Or can I sufficiently adjust (using the proportioning valve) the bias to function safely/properly?

[jpgolf14]

No the prop valve is an aftermarket adjustable type. Sorry I wasnt more clear on that. I

f I recall the year of MC is 1988. I have taken a few years off from the car and hope to start fixing her up again! Some of the thing I knew off the top of my head a few years ago arent so clear any more!!

Is there a formula or calculator to help match the torque bias ratio? Or can I sufficiently adjust (using the proportioning valve) the bias to function safely/properly?

Since you have an adjustable prop valve, it really doesn't make any sense to try to match the torque bias ratios. Since you'd have to dial the adjustable prop valve in anyway. With that said, it shouldn't matter much wether you choose the 12" or 13". Either will be enough for the track. Obviously the 13"s like nicer, but are also heavier.

[Antti66ht]

12" setup clears most 152 wheels, if you want to do drag racing with some slicks ocasionally.

I have wilwood 12,4 kit in the back and 14" with audi eight pots in front. I had stock front discs last summer, which area 10,5 paired with bigger rears, with no problems...