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Fiero front brake upgrade 87 gt by jjd2296
Started on: 10-19-2016 07:44 PM
Replies: 15 (931 views)
Last post by: mr_corean on 10-21-2016 10:14 PM
jjd2296
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Report this Post10-19-2016 07:44 PM Click Here to See the Profile for jjd2296Send a Private Message to jjd2296Edit/Delete MessageReply w/QuoteDirect Link to This Post
I'm looking at doing te front brake upgrade on my 87 GT. The Fiero store sells a bolt on kit that appears to be the grand am set up but I'm not sure. I have emailed them to ask. I have also
Looked at west coast Fiero 9 3/4 z24 front brake upgrade. Are the z24 rotors bigger? I don't know the size of the grand am ones I only know that they are the same size as the Fiero rotors but I don't know that size either!!
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Report this Post10-19-2016 07:56 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes, the Fiero Store package uses Grand Am brake hardware. Also, the Z24 and Grand Am brakes are basically the same thing. They both use 9.75" vented rotors with GM FWD front calipers.

[This message has been edited by Blacktree (edited 10-19-2016).]

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jjd2296
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Report this Post10-19-2016 08:20 PM Click Here to See the Profile for jjd2296Send a Private Message to jjd2296Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thnx so much for that!! The west coast Fiero product is 50 bucks cheaper and there is no core charge of 100 bucks!!!
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Blacktree
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Report this Post10-20-2016 12:05 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just FYI, that brake upgrade is going to shift the brake bias further to the front. So the front brakes will lock up sooner, and the rear brakes will be weaker. Also, brake pedal travel will increase, and the brake pedal will feel a little spongy. I'm not sure if you knew that already, so I thought I'd put it out there just in case.

If you don't need a parking brake, you can put the Grand Am front brakes on the rear also. That will even out the brake bias. The Grand Am front brakes are a direct bolt-on for the rear of an '84-87 Fiero. You swap the calipers left-to-right to put the bleeders on top, and that's it.

To get a decent brake bias while retaining the parking brake, you'll need to step up to the 11" brake kit, on all 4 wheels. And you'll need 15" or larger wheels.
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jjd2296
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Report this Post10-20-2016 07:42 AM Click Here to See the Profile for jjd2296Send a Private Message to jjd2296Edit/Delete MessageReply w/QuoteDirect Link to This Post
Even if I have done the s10 brake booster upgrade and instal the 11% larger brake master cylinder ?
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Report this Post10-20-2016 12:05 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jjd2296:
Even if I have done the s10 brake booster upgrade and instal the 11% larger brake master cylinder ?
Tip: The Fiero Store and some others are Not your friend and sells "brake upgrades" and other dubious things just to make money.

Install big MC on stock brakes will make the brakes Weak. This is one of the Basic Laws of Hydraulics.
Big MC is used to fix Fluid Volume use by GA upgrades and Not a upgrade to boost power because Big MC Reduces Power for them too.

  • Big MC + GA front + OE Rear = Rear brakes do Very little. Far less then normal.
  • Even if you Pass or Have No Inspection, removing Parking/Emergency Brakes is illegal in most States and Other places.

    Why some have Big MC + GA front + Seville Rear. Seville rear uses bigger piston with Parking Brake. (Note that Seville and others rear disk use same piston design w/ same problems as all years of Fiero. See my Cave, Rear Piston notes etc. )

    After all work is done, is a minor power boost at best but w/ vented rotors that can help stop brake fading for some racing like Auto Cross.

    See my Cave, Brake Upgrade

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    Blacktree
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    Report this Post10-20-2016 01:26 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
     
    quote
    Originally posted by jjd2296:

    Even if I have done the s10 brake booster upgrade and instal the 11% larger brake master cylinder ?

    That will fix the brake pedal travel and sponginess issues. But you'll still have excessive front brake bias. If you're planning to keep the Fiero rear brakes, then you may want to look into modifying the combo valve to increase the rear line pressure, or maybe install an aftermarket combo valve.
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    theogre
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    Report this Post10-20-2016 03:18 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
     
    quote
    Originally posted by Blacktree:
    That will fix the brake pedal travel and sponginess issues. But you'll still have excessive front brake bias. If you're planning to keep the Fiero rear brakes, then you may want to look into modifying the combo valve to increase the rear line pressure, or maybe install an aftermarket combo valve.
    Likely won't help.
    Big MC will always make OE rear very weak.

    80-85 Seville rear use ~54mm diameter piston vs 48mm OE Fiero (~54mm but RAYBESTOS Specs is 2.121" convert to MM is 53.8734.)
    With GA front and big MC You have some F/R Bias and parking brake.
    But Big MC + Seville rear is so close to same piston ratio to OE MC & rear meaning you get nothing but a vented rotor for money and time spend to "upgrade" the rear. Difference OE vs Seville is −0.006 (for 54mm −0.023 for Raybestos #). Minus is Seville is slightly weaker then OE. If Seville uses smaller Pads could be weaker still. (Front GA vs OE is only a little bit stronger. GA & OE front pads etc are very close to same but GA uses vented rotors.)

    [This message has been edited by theogre (edited 10-20-2016).]

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    jjd2296
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    Report this Post10-20-2016 05:25 PM Click Here to See the Profile for jjd2296Send a Private Message to jjd2296Edit/Delete MessageReply w/QuoteDirect Link to This Post
    Sounds like I shouldn't bother then if all I am doing is cruising? I did the S10 brake booster upgrade and I have to say its saved me on the pedal pressure needed! maybe that's all I need then?
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    theogre
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    Report this Post10-21-2016 12:11 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
     
    quote
    Originally posted by jjd2296:
    Sounds like I shouldn't bother then if all I am doing is cruising? I did the S10 brake booster upgrade and I have to say its saved me on the pedal pressure needed! maybe that's all I need then?
    I have and I'm disable too.
    Again, Use an OE MC w/ stock brakes.
    Restoring OE brakes can cost depending how bad the system is.

    Likely the old booster, MC or both had problems to need high pedal effort but too many people push various "upgrades" to fix them.
    Many people have no clue that a booster can "fail" but still work, often w/ high pedal effort depending on exact issue.
    MC w/ iffy "quick take up" section can cause same problem.

    Rear caliper(s) w/ pad clearance problems can cause low pedal but not high pedal effort.
    Air anywhere in the system can cause spongy pedal but not high pedal effort.
    Cheap pads can cause poor brake performance but don't buy hype or "race" pads. (Some race pads won''t work well for normal driving because can get enough heat.) Many local stores have good pads but don't cost a lot.

    See my Cave, Brake Service and Rear Brakes for a start.
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    Patrick
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    Report this Post10-21-2016 12:55 AM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
     
    quote
    Originally posted by jjd2296:

    Sounds like I shouldn't bother then if all I am doing is cruising?


    Unless you're "cruising" at 200 KPH... probably not.
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    Dennis LaGrua
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    Report this Post10-21-2016 01:16 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
     
    quote
    Originally posted by theogre:


    Install big MC on stock brakes will make the brakes Weak. This is one of the Basic Laws of Hydraulics.
    Big MC is used to fix Fluid Volume use by GA upgrades and Not a upgrade to boost power because Big MC Reduces Power for them too



    The people that have done the S-10 master cylinder upgrade and have driven their cars seem to say otherwise.

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    Report this Post10-21-2016 03:21 PM Click Here to See the Profile for litespdSend a Private Message to litespdEdit/Delete MessageReply w/QuoteDirect Link to This Post
    Contact Sluppy123 here on the forum. Not sure how often he's here, but he makes different brake upgrades for Fieros, and the quality of his work and his parts is amazing.
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    jjd2296
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    Report this Post10-21-2016 03:30 PM Click Here to See the Profile for jjd2296Send a Private Message to jjd2296Edit/Delete MessageReply w/QuoteDirect Link to This Post
    oh man I'm so confused now
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    Blacktree
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    Report this Post10-21-2016 07:12 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
    Ogre is right, the bigger bore master cylinder can move more fluid, at the expense of mechanical advantage. You would only use a larger bore master cylinder if you swapped in larger bore calipers. If you install a larger bore master cylinder on stock Fiero brakes, it will actually reduce the braking power (i.e. you have to push harder on the pedal to make the brakes work). A more powerful brake booster (like the S10 unit) will compensate for the braking power you lost from the larger bore master cylinder.

    So in summary:

    A "big bore" master cylinder is NOT an upgrade for stock Fiero brakes. It's actually a downgrade, because it reduces braking power.

    A "big bore" master cylinder is needed when you upgrade to larger bore calipers, because those calipers need more fluid to fill the cylinders.

    A more powerful booster will increase braking power, both for the stock brakes and upgraded brakes.

    Hopefully that helps to clear some things up.

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    mr_corean
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    Report this Post10-21-2016 10:14 PM Click Here to See the Profile for mr_coreanSend a Private Message to mr_coreanEdit/Delete MessageReply w/QuoteDirect Link to This Post
     
    quote
    Originally posted by Dennis LaGrua:


    The people that have done the S-10 master cylinder upgrade and have driven their cars seem to say otherwise.



    I think you are actually referencing the s10 booster which is the common upgrade for making the braking effort easier. There has been much debate over the actual effectiveness of this upgrade, but I don't believe it has ever been stated that it is a downgrade. As Ogre and Blacktree have mentioned, if you only install the larger MC, which rarely comes from an s10, you will be exerting much more effort to get the same performance from your brakes. If you only install a larger booster, such as from an s10, you will get a brake pedal that is easier to push and get the same results from your brakes. This results in easier to modulate brakes for some and others having a harder time getting max effect from their brakes without locking the tires. I'l pile on with what Blacktree explained in list form but worded slightly different if it'll help at all.

    Larger front brakes, such as Grand Am, with no change in the rear, no change in booster, no change in MC results in heavy front bias and spongy pedal, terrible pedal feel.

    Larger front brakes, with no change in the rear, a larger booster, such as the common s10 upgrade, no change in MC results in longer pedal throw and heavy front bias, but decent pedal feel.

    Larger front brakes, with no change in the rear, no change in booster, a larger MC, such as the 90's full size chevy truck MC, results in a comparable to stock throw and stock like effort, but heavy front bias.

    Larger front brakes, with no change in the rear, a larger booster and larger MC results in good pedal feel but heavy front bias.

    Larger front brakes, with larger rear as well, no change in booster, no change in MC, results in very high effort at the pedal with a long throw and poor braking performance.

    Larger front brakes, with larger rear as well, a larger booster, no change in MC, results in the above with less effort at the pedal, but still poor braking performance.

    Larger front brakes, with larger rear as well, no change in booster, a larger MC, results in slightly heavier than stock pedal effort, stock like pedal throw, increased braking performance. Easier to lock all 4 tires if you have crappy tires.

    Larger front brakes, such as Grand Am, with a larger rear as well, a larger booster, a larger MC, results in a easier to modulate than stock brake pedal, stock like pedal throw, increased braking performance. Easier to lock all 4 tires if you have crappy tires.


    Obviously upgrading everything together is your best bet for performance and in some cases safety. I'd look around a bit to see what others have done for models as far as balancing fronts with rears. I personally have C5 front calipers and rotors with C4 rears along with the s10 booster and truck MC. The pedal feel is great, the travel is great, the stopping power is insane, the bias is good, the C4 rears keep the e-brake and use a different design that doesn't have the issues the Fiero e-brake has while still using the Fiero cable system. Only issue now is I have crappy tires, lol!

    [This message has been edited by mr_corean (edited 10-21-2016).]

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