Project Viper: Part 15 – Fixing the Factory Brake Bias

2nd Gen Viper GTS 40mm Toms rear caliperKnown as the “Tom’s 40mm caliper”, the new caliper was modified by a guy named Tom, who machined out a factory caliper to accept a larger 40mm piston.  This shifts the brake bias from a terrible 70.3% front bias to a more ideal 66.0%. (the actual piston cap of the new caliper is still the same 36mm in size).

When the Viper gained ABS in 2001, those cars used an entirely different suspension knuckle and caliper, that featured a 43mm piston and a 62.7% brake bias.

Viper Stainless Steel brake line vs stockTime takes its toll on rubber. While we had the caliper off, we upgraded the factory rubber brake lines with stainless steel replacements from Stoptech.  Stainless steel brake lines make a huge difference in terms of pedal feel by reducing expansion of the line, which results in a more solid brake pedal that has less ‘mushy’ travel.  I highly recommend upgrading brake lines to stainless.

Viper Gen 2 Tom's 40mm rear caliper and stainless steel brake lineWith the stainless steel lines and new 40mm caliper reinstalled, we were ready for the brake pads.

Viper GTS rear brake pads Ferodo DS2500There are not too many pad options for the Viper/Elise rear caliper.  The Ferodo DS2500 (FCP878H) is a great trackable street pad and a good match for the front pad we will be using.

For 1992-2000, the rear pad size can be searched by the following numbers: 330.5, 22, 491, D491, 0491.XX.15.44, 1682, HB278, FCP878, MDB1445

Gen 2 Viper stock Brembo pads vs Ferodo DS2500The factory Brembo pads (left) still had plenty of life left in them.  But while we were at it, we wanted to freshen up every aspect of the Viper’s brakes with the new Ferodo DS2500s (right).

Gen 2 Viper GTS rear brake caliperAfter installing the pads, the rear brakes were done and we could turn our attention to the fronts.

Quick Reference:

Page 1 – Stock rear brake caliper removal and measurements.
Page 2 – Rear 40mm calipers, stainless steel lines, and upgraded pads.
Page 3 – Replacing front brake lines with stainless steel.
Page 4 – Upgraded front brake pads and install.

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