by HK1837 on Wed, 11 Oct 2017 7:36 +0000
The pre-stability control cars had smaller brakes and also a load-sensing valve on the rear circuit. So you have two issues:
1. If you go up in tyre size you have to go up in rotor diameter by a similar percentage to achieve the same braking torque. This is one major reason why when the SR5 went from 255/70/15 to 265/65/17 the rotor diameter increased from 297mm to 319mm. This is a 7-ish % increase in rotor and a 5.2% increase in tyre diameter. The 265/75/16 is 9% bigger than 255/70/15.
2. These also had the load sensing valve that increased rear braking when loaded. When your front suspension sags (which these are notorious for especially after fitting bar and winch) it provides less rear braking as the load sensing valve thinks the rear is higher.
The beauty with these though is you can fit TRD front rotors which are 338mm diameter (14% rotor diameter increase), all you need is the rotors (120 series or TRD Hilux), 120 series calipers (or TRD Hilux calipers) and the backing plates. I think you can use 150 series rotors and calipers too, they are the same diameter just 4mm thicker, but you'd need 150 series calipers too. Then buy some original Hilux or Prado 120 17x7.5" rims or aftermarket Speedy copies and fit either 265/65/17 tyres or if you want bigger go 265/70/17. 265/70/17 are pretty much the same size as 265/75/16 but remember that these are still 65mm diameter bigger than your originals and with a 50mm lift you are restricted legally to 50mm maximum increase (25mm lift) in tyres. 265/65/17 are 38mm (19mm lift) over the originals. At least with the TRD brakes you are accounting for the bigger tyres if you choose to go that way, the TRD combination was the 338mm brakes with 17x7.5 rims and 265/65/17 tyres. If you stuck with the legal tyres (265/65/17) you could also fit the 2012 update 319mm rotors and calipers and also have brakes equivalent to what the manufacturer intended. I don't see the point in that though for a pre-2012, just copy what the TRD had.
I cooked my original rotors by 30,000kM, mainly towing but with the 265/65/17 tyres. I replaced them with T3 rotors and Bendix pads but they suffered too. So I bit the bullet and upgraded to the TRD size 338mm rotors. Problem solved!