Potential 11 1/8" Brake Upgrade for 88 Fieros with Stock 15" Wheels (Page 1/4)
fieroguru NOV 22, 01:19 PM
For a while now I have been looking for 2 things.

1. Caliper upgrade for the 88 Fieros - mainly looking for a caliper with the same or slightly larger piston bore, that has the same bolt pattern for mounting.
2. Brake upgrade for the 88s that will fit under the stock 88 15" wheels.

I think what I have figured out so far is really cool and wanting some feedback as to the potential market.

First up is a new caliper option that I will call Caliper X. A stock 88 front caliper is on the right, Caliper X is on the left in both pictures.



Caliper X is very similar to the 88 Fiero caliper and has some cool key features.
1. Looks very similar to the stock 88 caliper - for a stealthy upgrade.
2. Same mounting pattern, so it will bolt directly to the stock 88 knuckle.
3. Same caliper bridge bolt pattern, so Fiero bridge will bolt to Caliper X and Caliper X's bridge will bolt to the stock 88 caliper.
4. Caliper bridge is about 1/8" wider, so this caliper with accept rotors thicker than 20mm.
5. Available with caliper piston diameters of 48mm (stock 88 Fiero) or 52mm (17% increase in clamp pressure and should be a small enough change to keep the stock brake master).
6. Caliper piston and bridge placement are shifted away from the rotor, which gives them 9% more braking leverage, and allows an 11 1/8" larger rotor to fit under it (stock 88 is 10.4")
7. Caliper body for the piston is cast iron.

So caliper X has the potential to improve braking 9% through increased leverage as well as 17% (with 52mm piston) with increased clamp pressure by 17%, allow for a larger than stock rotor to improve heat dissipation and fade resistance, and can be installed under the stock 88 15" front wheel.

88 Fiero caliper mounted on an 88 Fiero rotor:


Caliper X mounted on an 88 Fiero rotor:


I am still sorting out the rotor options that will fit under Caliper X w/o a caliper bracket. I am trying to find the best compromise between, largest OD, lightest weight, and availability/cost. The 11 1/8" rotor shown below is a strong contender. It fits perfectly, is readily available and weights 12 lbs (stock 88 rotor is about 11 lbs). I have 4 more rotors to check fitment on before narrowing down the selection, but this one certainly works!

Caliper X mounted on an 11 1/8" rotor and inside an 88 Fiero front wheel:







I still need to develop the concentric rings and find the proper brake hoses as the hose connections are slightly different, but most of the hard work is done.

Unfortunately, this is front only option at the moment, as this caliper doesn't have a parking brake setup.
We could think of it as the grand am style upgrade for the 88s, where it is plug & play using stock parts w/o needing any caliper brackets.

I might be able to pair the Caliper X front kit with an other 88 stock wheel kit I was working on, but stopped because it wouldn't fit under the stock 88 front wheel (but did fit the 15" rear). I have found a rotor slightly smaller than 11 3/4" that can be made to work with the 88 Fiero 15". It will need a caliper bracket, concentric ring, and either a small wheel spacer (1/16" would be plenty), or clearance the head of the brake line bolt. This kit would provide about 19% increase in braking leverage and allow reusing the stock 88 rear caliper for parking brake function. This would end up being a slightly less overall improvement vs. the front using 52mm Caliper X , but it could be an option for a more closely balanced approach.







Thoughts and feedback?

[This message has been edited by fieroguru (edited 11-22-2018).]

mrfiero NOV 22, 02:18 PM
I like it! I have your 13" brakes on my 3800sc GT and will be reusing the old 12" set-up it replaced on another Fiero and like them with the bigger aftermarket wheels. I also have a bone stock '88 GT and Formula that I plan on keeping stock. I would be very interested in improved braking on these cars while keeping the stock wheels.

Keep me in the loop!
88Fingers NOV 22, 06:40 PM
Hi Paul, this would be a great addition to the Targa car as I need to keep the 15" wheels now due to needing the taller sidewall tires for the brutal road conditions.
Even just a larger front kit would be advantageous for heat dissipation for the tight in-town sections. Please soldier on with this development!
pmbrunelle NOV 22, 07:38 PM
Interesting, but a brake kit is uninteresting if one of its components is referred to only as "Caliper X".

Vendors go out of business, so I would never buy a brake kit having a caliper that can only be purchased from the kit vendor. Ditto for the rotors.

A known second source (hence divulging the identity of the caliper) is a requirement for any wise consumer.

As far as the parking brake, what about a drum-in-hat setup? After my present engine project, I'll be trying to make the drum parking brake work on my LeBaron discs, in order to get a good parking brake and 2.5" bore calipers all around.

Other than the LeBaron disc commonly used on Fieros, there are other Chryslers having the same drum-in-hat, but having different outer disc portions. Maybe one of those would fit within the diameter requirement of Caliper X.
fieroguru NOV 23, 12:01 AM

quote
Originally posted by pmbrunelle:

Interesting, but a brake kit is uninteresting if one of its components is referred to only as "Caliper X".

Vendors go out of business, so I would never buy a brake kit having a caliper that can only be purchased from the kit vendor. Ditto for the rotors.

A known second source (hence divulging the identity of the caliper) is a requirement for any wise consumer.



In the event I bring this kit to the market, anyone who purchases the kit, will get the application information for all parts, so they will be able to source replacement parts from where ever they wish, when ever they need to.

[This message has been edited by fieroguru (edited 11-23-2018).]

sourmash NOV 23, 09:48 AM

quote
Originally posted by fieroguru:


In the event I bring this kit to the market, anyone who purchases the kit, will get the application information for all parts, so they will be able to source replacement parts from where ever they wish, when ever they need to.



So long as it's a caliper that isn't an odd duck (obscure unit) that will go into discontinued status in short order, it sounds like a good option if you want to retain stock wheels. QUESTION: has anyone considered machining the stock caliper for a larger piston? It doesn't allow for a larger rotor, I know.
Iain NOV 23, 10:10 AM
Interesting, especially since 'X' is made in France, a bit closer to me than the States!
I suspect the cost will probably be cheaper from you than our froggy neighbours though. I have been looking into different calipers as I'm not terribly impressed with the various Wildwood calipers I've been trying to fit up.
Will uou be selling just the calipers on their own? I have Ali hats with a variety of rotors, the wider bridge would give me better options.
fieroguru NOV 23, 12:23 PM

quote
Originally posted by sourmash:
So long as it's a caliper that isn't an odd duck (obscure unit) that will go into discontinued status in short order, it sounds like a good option if you want to retain stock wheels. QUESTION: has anyone considered machining the stock caliper for a larger piston? It doesn't allow for a larger rotor, I know.



The production numbers for this application far exceed those of the 88 Fiero. Additionally, there is a newer version from a later model application that uses the pad abutment brackets like everyone is switching to, so that will further expand the caliper availability.

The OD of the piston bore housing for the 88 Fiero caliper is about 64mm. So with a 48mm bore, the wall thickness is 8mm. Going up to the 52 mm bore would reduce it to 6mm. With 100 lbs force on the brake pedal, the line pressure will be about 1500 psi. Add the S10 booster and will be nearly 1700 psi. For reference, the bore housing on Caliper X is 68mm, so it has the same 8mm wall thickness, but is cast iron.


quote
Originally posted by Iain:
Will you be selling just the calipers on their own? I have Ali hats with a variety of rotors, the wider bridge would give me better options.



I will likely have various levels of kits with one of them being just the calipers.
Iain NOV 23, 05:23 PM

quote
Originally posted by fieroguru:


I will likely have various levels of kits with one of them being just the calipers.



Wonderful, I'll put my brake experimentation on the back burner. 1 less Project holding me up..
Pity I sold all my 15" wheels.
Raydar NOV 23, 05:36 PM
Wow!

My 2nd car has the C4 rotors, using the 88 calipers, and a knockoff of Jon Lagler's (dogbone shaped) brackets. That was the kit that I was going to install on my gray car, before I got your 13" kit.
If I didn't already have what I do, this new kit would be a definite consideration.
(FWIW, I particularly don't like the 88 brackets that are currently available elsewhere, due to the way that the calipers are offset, upward - for several reasons. But that's just one man's opinion.)

[This message has been edited by Raydar (edited 11-24-2018).]