Disc Brakes in rear of Grand Am??? [Archive] - GrandAmGT.com Forum

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82-T/A
10-30-2010, 01:53 PM
Hey guys,

Haven't been on here in a long time. I hope you guys don't mind me posting here, but I no longer own a grand am anymore. I went through two 97 Grand Ams back in the day, and they were great cars.


So... I'm upgrading my 1987 Pontiac Fiero. I just installed a brand new set of Grand Am brakes to the front of my Pontiac Fiero:

http://www.PontiacPerformance.Net/Temp/Brake1.jpg

I've been told that because the car is mid-engine, if I'm going to upgrade the front brakes, I really need to upgrade the rear brakes as well. So... technically, I could just swap in a Grand Am rotor and caliper on the back too... but I would really rather it be proportional.

Can anyone tell me... was there ever a Grand Am that had DISC brakes in the rear? Or were they all drum? My two Grand Ams had drum brakes in the rear.


Thanks!!!

Todd

whiteGT99
10-30-2010, 02:00 PM
my 99 has disc brakes in the rear

AaronGTR
10-30-2010, 02:02 PM
Most '99+ grand am's were rear disc. Only certain SE models came with rear drums, and all GT's were disc.


As for keeping things balanced, that is a good idea. As for how much rear braking power you really need, that would take a little bit of research. It would depend on what your actual front to rear weight bias is, and how stiff your springs are which will somewhat affect the weight transfer to the front under braking. With the engine mid/rear mounted you can probably use more rear braking power than most cars (similar to Honda's NSX) but the fronts still do a larger percentage of the work.

I would say an upgrade to discs would be warranted, just not too big on the disc size or calipers. If you really wanted to optimize it you could test stopping distance and tune the balance using a proportioning valve and different front/rear pad compounds. Depends on how picky you are and what level of performance you are shooting for. :thumbs:

82-T/A
10-30-2010, 02:13 PM
Most '99+ grand am's were rear disc. Only certain SE models came with rear drums, and all GT's were disc.


As for keeping things balanced, that is a good idea. As for how much rear braking power you really need, that would take a little bit of research. It would depend on what your actual front to rear weight bias is, and how stiff your springs are which will somewhat affect the weight transfer to the front under braking. With the engine mid/rear mounted you can probably use more rear braking power than most cars (similar to Honda's NSX) but the fronts still do a larger percentage of the work.

I would say an upgrade to discs would be warranted, just not too big on the disc size or calipers. If you really wanted to optimize it you could test stopping distance and tune the balance using a proportioning valve and different front/rear pad compounds. Depends on how picky you are and what level of performance you are shooting for. :thumbs:

Thanks Aaron, I really appreciate it.

It already has discs in the rear, but they are proportional to what was stock in the front. The gang on the Fiero List say I should upgrade too... but I like keeping "like components." I probably could have just checked on Rock Auto before (like I just did now) and discovered that there are disc brakes for the Grand Am. I guess the only question now is whether or not I can make them fit. Strangely enough, stock Grand Am front calipers apparently fit on the rear hub without any modification? But... then I lose my emergency brake.

The weight distribution is 47 front / 53 rear. The plan was to keep the stock proportioning valve (and the stock proportion). I've got a larger bore master cyl, and stainless lines all round.

Do you know if the bore on the front grand am brake calipers are the same diameter as the bores on the stock rear Grand Am calipers?


Thanks!!!

AaronGTR
10-31-2010, 11:32 AM
They are not. The piston bore on the front calipers is much larger the rear calipers on this car (since it's front engine fwd). The rears are pretty small. The rear disc is a decent diameter but is thinner and solid (non-vented) and doesn't have as much pad area as the front. This is mainly because the emergency brake is a cable operated drum style brake inside the hub of the rear disc.