Gt rotors on St, Will I need new calipers? Options

[Jeremy1210]

I want to buy the slotted rotors that are for sale on ebay, but they say they are for Gt. I thnik I have read that the GT rotors are bigger,if that is true, will I need new calipers?

[kuya1284]

QUOTE (Jeremy1210 @ Aug 5, 2003 - 9:00 AM)

I want to buy the slotted rotors that are for sale on ebay, but they say they are for Gt. I thnik I have read that the GT rotors are bigger,if that is true, will I need new calipers?

Yes, they are a little bigger. As far as needing new calipers, I'm pretty sure you would, but I'm not sure how this would work out. As a matter of fact, I was going to look into this when I convert my drums. Good question...

[Jeremy1210]

Shoot I forgot to say that I was meaning the new calipers on the front

[kuya1284]

QUOTE (Jeremy1210 @ Aug 5, 2003 - 2:05 PM)

Shoot I forgot to say that I was meaning the new calipers on the front

Yeah, I knew what you meant...

[Jeremy1210]

I ask b/c I am in the process of converting to disc. And I figure why not just buy front rotors too, but I Don't want to have to buy calipers also

[Coomer]

Moved to a more appropriate forum, since I just edited the forums a little bit for clarity.

[SpedToe169]

I'm just guessing here but I bet the GT and ST calipers are the same. The caliper hangars will be different due to the different size rotors. If you're doing the rear swap anyway tho, it might be easier to take the calipers and hangars off all 4 corners and not have to worry about it.

[97GTinKC]

Are the pads the same for GT and ST? if not, then the calipers are probably different too. and if you dont swap the rear to GT disks, you risk changing the braking balance, could actually hurt braking performance, especially if you have ABS (did ST's have an ABS option?)... If I were doing it, I would try to get ALL the brake components off a GT, front and rear, including the proportioning valve, or at least spend some time researching part numbers to see what is different and swapping all affected parts as a set. (Or it may work great, anyone already tried all the different combos? )
I'm thinking that with the larger GT rotors, (they ARE larger aren't they?), even if the caliper is the same, the braking surface will be moving faster at the same speed, being farther out from center, this has to effect the stopping power differently, may not be enough to make a difference. there may be other factors i'm not aware of that will help compensate.
I have been this route on other cars, swapping larger brakes at the rear and not the front, and had problems with the brakes trying to lock up at one end b4 the other since I had upset the balance between front/rear.
It was great for making right-angle turns, didnt need to use the emergency at all, just cock the wheel in the direction you wanted to go, hit the brakes, the rear would lock up, sending you into a skid. then let off and floor it at the right time! but it sucked in the snow bigtime.

[SpedToe169]

Good points KC. Let me add some.

Anytime you change the braking potential at one end of the car or the other, you HAVE to change brake balance to keep the braking balance correct. This is done with an adjustable proportioning valve and is VITAL to non-stock brake systems. It also has to be set up correctly which can take some time and patience in a big deserted parking lot (or a race track if you have one handy ) but its not hard to do.

Secondly, the speed that the rotors are turning doesn't make any difference in braking performance. Its dependent upon the coefficient of friction of the pad/rotor interface (this changes with temperature), the area of the interface, and the pressure being applied to press the pad against the rotor. Bigger rotors work better because they have more mass, more mass means that they're bigger heat sinks, that means that they can absorb more energy before they get too hot and start to overheat the pad (this is a very high temperature >800F for most street pads ~1400F for real race pads). The larger rotors also create more of a negative torque acting to slow the car, so they don't have to work as hard to do the same amount of 'slowing'.

And lastly, KCGT had a very good point about the pads being different. I can attest first hand that the ST and GT pads are different, so the calipers are also different.

This post has been edited by SpedToe169: Aug 12, 2003 - 11:14 PM