I've been doing some reading on here about brake upgrades, and I'm assuming this has been thought of already, but why wouldn't a 5x100 large rotor work vs doing a C4 corvette rotor and having to get it drilled?
The main reason is that the bolt pattern is one of the easiest things to change and other more critical dimensions can't be changed.
Say you were looking for a rotor to be used on an 88 Fiero and want to retain the stock calipers. The rotor you selected won't work for a few reasons.
Rotor thickness - must stay below 20mm to retain use of the 88 Fiero calipers (or use the C4 Vette caliper) - rotor in the link is nearly 30mm thick. So unless you want to start swapping calipers, that rotor is an immediate no-go.
Rotor Hat ID (back side that the wheel flange slides into) - again with the 88 Fiero, the front wheel flange on the hub is oversized - sized to allow a 5 x 4 3/4" pattern. Issue is when mfgs use a smaller wheel pattern, they normally reduce the ID of the rotor hat... This means that the vast majority of the rotors with a 5x100 and even 5x115 pattern will not clear the enlarged wheel flange on the 88... so that makes them an immediate no-go as well. I can tell just by looking at the link, that rotor will not clear the 88 front hub.
Rotor Depth - To move the calipers, you need room for caliper adapter brackets, unless you want a very complicated and more costly caliper bracket design). This means that you want the rotor to be deeper than stock, but you can go too deep or the rotor and/or the caliper will interfere with the a-arms.
Hub Pilot ID - Needs to be large enough to slide on the Fiero hub. Some of the rotors with 5x100 have a smaller pilot ID than the Fiero, so now you have to enlarge it with precision.
Cost - this only comes into play if you have the option to choose between two that otherwise fit the same. Using rotors from mass market applications will help keep costs down as well as ensure rotor availability for years to come.
Weight - again only comes into play if you have the option to choose between two. Lighter is better, unless it costs 3X as much.
Finding a large diameter rotor that fits, works with existing calipers, and doesn't require other cutting and grinding of other components for installation and proper clearance, is not easy. The list of larger rotors that fit well is very, very small. I have reviewed dimensions on well over 1000 applications and have a list of possible contenders at various size points that is over 140. However, the list of ones that fit all constrains is single digits... Options are very, very limited.
The primary focus for when I started making it was for the 88s, but I didn't restrict the fitment to just what fits the 88. If it was in the ballpark I added it to the list. The 84-87 rear rotor can't be as deep as the 88s, and the front can be deeper with the primary source of interference being the caliper to the shock.
If I have an 86GT, and was looking to start gathering parts, would you suggest getting 88 calipers or c4/c5?
Neither...
The 88 Fiero calipers will require you to install them upside down in order for the parking brake to work with the 84-87 cable setup. C4/C5 calipers really mess with the bias and require several other parts and owner adjustment to get the bias back to anything close to stock... and you have other challenges with getting the rear parking brake setup to work.
I was looking into a cheap upgrade for my 87 GT in addition to the Tuff Stuff booster for sticky tires, and for a better look. I'm pretty busy right now building a house and work, then going back to my second job after the house is done.
But I think I found a 13" rotor that seems like it would work with the stock calipers with adapters. I think I might get into it soon. We have a machine shop we have do work for us at one of my jobs that should give me a good deal on adapters.
I should probably just pass the info to Guru since I've been trying for a couple years to get on it...
[This message has been edited by SCCA FIERO (edited 05-12-2019).]
That is a 2 piston willwood caliper that I use on my 86 GT with 11" Lebarron rotors and a set of the zettner style adaptor brackets. If you look at my thread in the construction zone you can see how it all works.
The problem with modding the 84 to 87 brakes is that the stock proportioning valve is too front biased. This is not that noticeable with stock calipers and rotors because they are not strong enough to overcome the grip of modern tires. I did not run my car very long with stock brakes but I could stomp on them and nothing would lock up. They would have maybe been able to lock up the fronts if the brakes were bedded in better but I don't know.
So then you put on a Lebarron or other big brake kit and you now have more than enough power to overcome the grip of your new high performance tires. So what happens? The right front tire locks up when you stomp on the brakes. The rear tires do not come close to locking up (in this case a good thing) so the car will stay straight. Stopping distance will improve slightly but not enough to make it worth while flat spotting a front tire.
With a bigger brake set up you need the rear tires to do more work than what the stock proportioning valve will let them do. You could put bigger rotors and calipers in the back and leave the fronts stock but that would spoil the big brake look. And really, filling that wheel with a big rotor and a nice powder coated caliper is all most people are trying to do anyway.
You can leave the 11" Lebarron rotors at all 4 corners and use a small bore single piston Willwood caliper in the front and the Camaro rear calipers to balance things out a bit better. Not the way I did it but it seems to work fairly well.
Keep in mind that the effectiveness of any brake system is affected by 3 main things: the weight of the car, the grip available at the tire and the balance of the system. Once you get to the proper size of caliper and rotor to suit those factors, going bigger just adds more weight to the car. And it is unsprung weight, the worst kind.
And thats why I think any thing bigger than 11" rotors are a waste of money in most Fieros. Yes they look cool but they just are not needed for a car that weighs 2800 lbs or less.
[This message has been edited by wftb (edited 05-12-2019).]
Living in the country, and also not racing, I have never needed panic emergency stopping power. I do however realize the Fiero is lacking in brake performance.
A 'no longer posting' member of the forum and a member of my local Fiero club told me about a great break up grade he bought and swore by.
It was a modified brake booster. It was sold in The Mall but I did not follow the thread to see the opinions of any who went that route. "Darkwing" alerted me via PM. Let me see if I can find it.
Just some links with info about how the brakes work and what some of us have done to them. The S10 brake booster upgrade is a popular item for stock brakes. Do a search, lots of info about this mod available.
------------------ 86 GT built 2.2 ecotec turbo rear SLA suspension QA1 coilovers on tube arms
The 88 Fiero calipers will require you to install them upside down in order for the parking brake to work with the 84-87 cable setup. C4/C5 calipers really mess with the bias and require several other parts and owner adjustment to get the bias back to anything close to stock... and you have other challenges with getting the rear parking brake setup to work.
You have great info, what would you use on a non 88?
Originally posted by 2.5: You have great info, what would you use on a non 88?
When I find something that meets my standards, I will offer an 84-87 brake kit. Front caliper mounting using a machined surface and the rear parking brake setups are the primary areas of concern.
Originally posted by fieroguru: Front caliper mounting using a machined surface
I'm semi-seriously imagining that you could ship a file with your brake kits, so that users could flatten that area.
My dad was telling me that back in his day, as part of his education, he had to take a piece of steel, and turn it into a cube with perfectly flat sides (and presumably perpendicular), using only a hand file.
Most of my products have a strong bias for bolt-on install with minimal to zero "finesse" work. Expecting the customer to make the surface flat & parallel will have inconsistent results, which I am not a fan of.
Most of my products have a strong bias for bolt-on install with minimal to zero "finesse" work. Expecting the customer to make the surface flat & parallel will have inconsistent results, which I am not a fan of.
What do you think of the Grand Ams all around as far as improvement? Tho yes, no Ebrake.
Also do you think braided hoses make a difference in performance or at least a better feel?
On the back of my fiero I have a rubber hose on one side and a braided hose on the other. I had a braided hose that got ruined so I just temporarily put on a rubber hose I had laying around. It is still like that, and it makes no difference at all.