My 92 Legacy Turbo sedan has always had a propensity for warping its brake
rotors. It doesn't make sense to spend one-fourth of the value of a car on
fancy brake rotors. Does anyone know of a cost-effective way to treat the
stock rotors so they won't be so prone to warping? Does anyone know of
warp-resistant aftermarket rotors that will fit under the stock wheels? Has
anyone ever upgraded to a single stage brake booster to cure that stupid
mushy pedal feel? Does anyone know exactly which Impreza models had the
single stage booster that fits our cars?
Bill Robinson
Warping Brake Rotors
Moderators: Helpinators, Moderators
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Josh Colombo
Warping Brake Rotors
Bill,
Here's what I would suggest you do. The turbo legacy front brake calipers have the same piston size as the WRX. The caliper only allows for a slightly smaller rotor, so upgrading in size to a WRX sized rotor 11.4" won't probably gain you much. Plus if you want to keep the 15" wheels, you need to stay with the current sized rotors.
First issue, warped rotors. This term is thrown around a lot, myself included.....when the rotor itself is probably not warped, but has a variation in thickness along its surface. This white paper can probably explain it better http://stoptech.com/whitepapers/warped_rotors_myth.htm
As for a solution.......I've run several different brands/types of rotors, from OEM, aftermarket from parts store, and brembro rotors. IMO, the OEM's provided the best bang for your buck in terms of not having vibration issues, ie. Disc Variation Thickness. The next step would be to cryo-treat the rotors. As explained in some messages about brakes just before this one. Cryo-treating metal, especially cast metals, dramatically improves its properties, and for around $50 I think it's worth it.
Other issue that can cause brake pedal pulsation or the affect of feeling like the rotor is "warped" is when you replace pads. A new brake pad will lay down a layer of pad material on the rotor as it breaks in......If you switch brake pads, you have two different brake compounds on the rotor, and can get a spotchy effect where you have different brake pad material on the rotor, which has different coefficients of friction. This mostly seen on semi-metallic pads. Some people say you should have the rotor turned. If you know it's good.......just sand the rotor or something similar to remove the previous pad material.....so you have a "green" surface when you bed in the new pads.
The single stage booster.....I know a bit of impreza guys have done it......some say it was worth it....others say it wasn't worth the hassle and complete pain in the arse to remove the booster and all the associated stuff underneath the dash. The single stage booster came on 93-95 impreza L models I believe. Other good thing is that the single stage booster is of the earlier design boosters so it should fit your existing master cylinder just fine. (There's been talk that the boosters changed design and that the older boosters won't work right with the newer MC's, however I haven't really had anyone confirm it.)
Bill, what I would suggest for you is getting a set of OEM rotors, have them cryo-treated. Get a set of stainless steel lines, which will improve the mushy brake feeling. Get a set of good pads, probably axxis metal masters or preferably axxis ultimates....depending on your braking needs, and top that all off with some good fluid, Valvoline synthetic DOT 4 fluid.
That combo is an effective in performance and cost, and should satisfy things.
I'm goin to post some links.....but I gotta find them first....
Here's what I would suggest you do. The turbo legacy front brake calipers have the same piston size as the WRX. The caliper only allows for a slightly smaller rotor, so upgrading in size to a WRX sized rotor 11.4" won't probably gain you much. Plus if you want to keep the 15" wheels, you need to stay with the current sized rotors.
First issue, warped rotors. This term is thrown around a lot, myself included.....when the rotor itself is probably not warped, but has a variation in thickness along its surface. This white paper can probably explain it better http://stoptech.com/whitepapers/warped_rotors_myth.htm
As for a solution.......I've run several different brands/types of rotors, from OEM, aftermarket from parts store, and brembro rotors. IMO, the OEM's provided the best bang for your buck in terms of not having vibration issues, ie. Disc Variation Thickness. The next step would be to cryo-treat the rotors. As explained in some messages about brakes just before this one. Cryo-treating metal, especially cast metals, dramatically improves its properties, and for around $50 I think it's worth it.
Other issue that can cause brake pedal pulsation or the affect of feeling like the rotor is "warped" is when you replace pads. A new brake pad will lay down a layer of pad material on the rotor as it breaks in......If you switch brake pads, you have two different brake compounds on the rotor, and can get a spotchy effect where you have different brake pad material on the rotor, which has different coefficients of friction. This mostly seen on semi-metallic pads. Some people say you should have the rotor turned. If you know it's good.......just sand the rotor or something similar to remove the previous pad material.....so you have a "green" surface when you bed in the new pads.
The single stage booster.....I know a bit of impreza guys have done it......some say it was worth it....others say it wasn't worth the hassle and complete pain in the arse to remove the booster and all the associated stuff underneath the dash. The single stage booster came on 93-95 impreza L models I believe. Other good thing is that the single stage booster is of the earlier design boosters so it should fit your existing master cylinder just fine. (There's been talk that the boosters changed design and that the older boosters won't work right with the newer MC's, however I haven't really had anyone confirm it.)
Bill, what I would suggest for you is getting a set of OEM rotors, have them cryo-treated. Get a set of stainless steel lines, which will improve the mushy brake feeling. Get a set of good pads, probably axxis metal masters or preferably axxis ultimates....depending on your braking needs, and top that all off with some good fluid, Valvoline synthetic DOT 4 fluid.
That combo is an effective in performance and cost, and should satisfy things.
I'm goin to post some links.....but I gotta find them first....
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Josh Colombo
Warping Brake Rotors
If this dude has the right info, here is the part numbers for the booster http://forums.nasioc.com/forums/showthr ... ge+booster
and here is a listing of some other threads that have info on the single stage booster.......which may or may not persuade you to do the work.
http://forums.nasioc.com/forums/search. ... descending
Josh
and here is a listing of some other threads that have info on the single stage booster.......which may or may not persuade you to do the work.
http://forums.nasioc.com/forums/search. ... descending
Josh