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I need some help/advice on my dual piston C4 Corvette upgrade by zmcdonal
Started on: 10-17-2014 07:27 PM
Replies: 22 (638 views)
Last post by: jb1 on 10-24-2014 02:34 AM
zmcdonal
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Report this Post10-17-2014 07:27 PM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
My 3800 car already had the dual piston C4 Corvette brake upgrade done on it when I bought it, it has a couple issues and needs some tweaking. There does not seem to be much info on this swap, it seems that most people are running the single piston Corvette calipers or the 12" Corvette rotors with 88 Fiero calipers. Everything in the rear is fine but the front has some issues. When I was driving it I thought it didn't seem to turn very sharp compared to my other Fiero, but I thought it might have just really need an alignment. After taking a closer look at the front I discovered that the brakes are not clearing the lower control arms. The front shocks have already been relocated a little further back for clearance. The banjo bolt was running right into the lower shock mount.

Here is the brake setup for any that are not familiar


Here is the issue



Normally the steering rack of the Fiero GT is 3 turns from lock to lock, with this interference I am only getting a little over 1 turn before the brakes hit, and that is with the suspension loaded, with the suspension relaxed the wheels can barely turn at all before the banjo bolt contacts the shock mount.

After extensive searching on here I found a couple people that have used these brakes. From what I found it looks like everyone running these calipers runs them upside down, so the bleeders are on the bottom which moves the banjo bolt up for a little more clearance.
Here is a picture I saw on WCF site and they show the calipers upside down

So this morning I swapped the calipers which barely helped increase clearance with the suspension loaded, but with it up on stands it now has the same clearance with relaxed suspension, so I am moving in the right direction.




I have been using this thread from yellowstone's brake install as a reference
http://www.fiero.nl/forum/A...0111-2-109385-2.html

It looks like I am going to have to trim the lower shock mount to get clearance like they did for yellowstone's 13" brakes


I just wanted opinions on where to cut so that I do not sacrifice any strength of the shock mount. Also if I cut out a V section like shown in the picture and then bend the front part of that mount back, does it need to be welded or should it be ok without?

Unmodified shock mount


Should I just make a cut something like whats shown in yellow here and bend that front piece back?


Thanks in advance for the help and advice.

[This message has been edited by zmcdonal (edited 10-22-2014).]

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Report this Post10-17-2014 08:15 PM Click Here to See the Profile for IMSA GTClick Here to Email IMSA GTSend a Private Message to IMSA GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I would be curious about the hub that is used. I thought the kit had a thicker hub that pushed the rotor and wheel outwards a little more. This would slightly increase the turning radius. Also as far as alignment, when your wheels are straight, is your steering wheel centered?
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zmcdonal
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Report this Post10-17-2014 08:35 PM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by IMSA GT:

I would be curious about the hub that is used. I thought the kit had a thicker hub that pushed the rotor and wheel outwards a little more. This would slightly increase the turning radius. Also as far as alignment, when your wheels are straight, is your steering wheel centered?


Well my car also has the Corvair hub conversion done on it to run the 5x120 bolt pattern. As far as alignment goes, it does need to be aligned, it has not been aligned yet since it was all taken apart for the powder coating and new parts so the steering wheel is off center, but it looks like the inner tie rods have some play so the rack will probably need to be rebuilt.

 
quote
WCF website:
The Hubs are Fiero front Hubs with the disks machined off. These modified Hubs will increase the track width of the Fiero by 5/16" per side. The modified Hubs are required on the front only. The 1988 Fiero do not require these hubs.


So it looks like the brake swap runs the same modified Fiero hubs that any other brake swap would require.

[This message has been edited by zmcdonal (edited 10-17-2014).]

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Report this Post10-17-2014 08:53 PM Click Here to See the Profile for IMSA GTClick Here to Email IMSA GTSend a Private Message to IMSA GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
See this thread. This was a conversion offered by Chris (DoubleC4). Notice how thick his hubs are but also notice that the person that installed them had the same issue that you are having with rubbing. You may want to PM him if he found a solution.
http://www.fiero.nl/forum/Forum2/HTML/130826.html
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zmcdonal
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Report this Post10-17-2014 09:10 PM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by IMSA GT:

See this thread. This was a conversion offered by Chris (DoubleC4). Notice how thick his hubs are but also notice that the person that installed them had the same issue that you are having with rubbing. You may want to PM him if he found a solution.
http://www.fiero.nl/forum/Forum2/HTML/130826.html


Those are actually stock Fiero rotors that have been turned down, they just look thicker because they left a little more meat on them. But that is not a bad idea to PM him to see how he solved the issue. Actually after looking closer he posted his solution.

 
quote
Originally posted by thesameguy:
After lowering the car about 1.5", getting banjos with slimmer heads, and adjusting for a quarter inch of toe the interference was virtually (but not quite) eliminated, but just an FYI for a totally stock car.



This is what my hubs look like


It looks like DoubleC4's brackets clock those calipers up higher too. Notice how mine are like centered at 9 o'clock, the bottom of his caliper is at 9 o'clock. But my brackets look the same as the ones that WCF offers.
WCF bracket

My bracket

DoubleC4's bracket

[This message has been edited by zmcdonal (edited 10-17-2014).]

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jb1
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Report this Post10-17-2014 09:43 PM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post
I have same issue with my 13" set, I have dual piston camaro calipers. I plan on swapping to the newer camaro rotors and cutting a spacer to make up difference. . I cut the lower shock mount. But caliper still hits..
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Report this Post10-17-2014 10:52 PM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jb1:

I have same issue with my 13" set, I have dual piston camaro calipers. I plan on swapping to the newer camaro rotors and cutting a spacer to make up difference. . I cut the lower shock mount. But caliper still hits..


Any chance you have any pictures if how you modified the shock mount? How much did you gain from cutting the shock mount, compared to before? So have you just been living with the terrible turning radius, I mean the Fieros turning radius was pretty pathetic as it was for how small the car is.
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Report this Post10-18-2014 03:35 AM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post
not been driving mine, trans problems. it really doesn't bother me to bad as far as normal driving , if I have to cut it very sharp it would catch the shock,
I cut the lower shock mount as pictured above and drilled a new hole further up to move the shock back, mine will catch the shock when trying to turn wheel but will not stop the wheel from turning just the banjo bolt catches it and if i turn it bit harder it goes past the shock,, not good but not an issue , usually only drive it for a few hours then back to my daily..
I am going to use the 13" 2012 camaro rotors and just make a spacer between the adapter and the knuckle and it should be plenty of clearance.

Also I have 13" so my calipers fit further out than yours,

[This message has been edited by jb1 (edited 10-18-2014).]

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Report this Post10-18-2014 06:32 PM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
Here is a picture that shows how much the turning radius is affected. The tape line on the bottom is the outside edge of the tire with the wheels at full lock. The tape line on the top is the outside edge of the tire when the caliper hits the shock mount.

This images is larger than 153600 bytes. Click to view.

[This message has been edited by zmcdonal (edited 10-18-2014).]

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Report this Post10-19-2014 12:25 AM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post
i got some shock brackets I thought about cutting the factory totally off and welding them up higher on the lower control arm...

------------------


87GTseries 1 3800sc (7.597 @88.53 1.579 60ft)
(series II swap in progress)
85GT Northstar/ 4t80e
86GT 3800 n/a---sold
Northstar Rebuild

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Report this Post10-19-2014 04:23 AM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post

jb1

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Member since May 2003
after thought , was the c4 front or rear rotors used? if the front were there is the problem , you might look at a set of rear c4 rotors and then have to space out caliper brackets for the difference the is about 1/4"...

------------------


87GTseries 1 3800sc (7.597 @88.53 1.579 60ft)
(series II swap in progress)
85GT Northstar/ 4t80e
86GT 3800 n/a---sold
Northstar Rebuild

[This message has been edited by jb1 (edited 10-19-2014).]

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Report this Post10-19-2014 05:10 AM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jb1:

after thought , was the c4 front or rear rotors used? if the front were there is the problem , you might look at a set of rear c4 rotors and then have to space out caliper brackets for the difference the is about 1/4"...


Hmm. Interesting, I have no idea what was used. I wish there was more info on THIS brake swap on here. There doesn't seem to be much. How did you know to use rears up front?
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Report this Post10-19-2014 08:22 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
It looks like yours are the rears, but the angle of picture isn't good. Put a straight edge across the wheel mounting surface of the rotor and measure to the backside of the rotor.

The Rear will be about 1.97" and the Front will be about 2.19"
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Report this Post10-19-2014 07:16 PM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post


Looks like I'm running fronts up front. So this swap is supposed to run rears in the front? Obviously it would give me a little more clearance. Does it matter what year? The previous owner said all the brake parts were 94. Then I would have to find the proper size spacers for the caliper brackets, any suggestions?
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Report this Post10-19-2014 07:25 PM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post
The brackets were made to use what you have but that doesnt work to well... have a spacer made to make up the difference between the fr and rear.. 1.97 and 2.19. It would need to be .22" to move the caliper out for the offset of the rear rotor.. that should give you the clearance you need

------------------


87GTseries 1 3800sc (7.597 @88.53 1.579 60ft)
(series II swap in progress)
85GT Northstar/ 4t80e
86GT 3800 n/a---sold
Northstar Rebuild

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zmcdonal
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Report this Post10-19-2014 07:37 PM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
Before I fork out money for new rotors and machine work I will mock it up with some washers and see how it does. Would be nice if that solved the problem.

My other thought was to start saving for Held's sport front suspension setup with tubular control arms and coilovers. A little drastic but I would think that would totally solve the problem with the added benefit of coilovers up front.



It's definitely expensive, but that seems like more of the right way to do it, compared to hacking up the shock mount.
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Report this Post10-19-2014 09:49 PM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post
You are going to have to buy new rotors... and a thin plate wu t 2 holes in it should not be much at all
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Report this Post10-20-2014 02:32 PM Click Here to See the Profile for OneQuickGTEdit/Delete MessageReply w/QuoteDirect Link to This Post


Not sure if this will be much help, but on mine I had a similar issue, I just rotated the caliper upwards by making new brackets.
This gave me the clearance I needed top clear the control arm.
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Report this Post10-20-2014 03:24 PM Click Here to See the Profile for Alex.07.86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
if cutting the shock mount is the fix, then cut it!
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Report this Post10-20-2014 04:07 PM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Cutting the shock mount will give you more but not full turn , swapping over to rear rotor and spacer for the caliper would be best way to go..
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Report this Post10-22-2014 10:38 AM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well the other day I was messing around with it some more and used washers to see how much changing to rear Corvette rotors in the front would help. It would help a little bit but I would definitely still need to trim the control arms. I still don't know if doing both of those would give me the full factory lock to lock. This is pretty ridiculous. The previous owner of my car did not purchase the brackets from West Coast Fiero, but they are the same design. How can they sell this crap design for $1,784?? For that kind of money they should of thought to move the caliper up slightly do avoid the interference like DoubleC4's brackets do. Yeah it might stop well, but you end up with the turning radius of a Mack truck, and for that price the customer shouldn't have to cut anything besides a check.

I think I am either going to find a machine shop and have new brackets made, or end up with the Arraut Motorsport sport front suspension kit, but so far I am not too impressed with them, I emailed them a couple days ago inquiring about it with a couple questions and have not heard back yet. As far as having new brackets made up at a machine shop, what is the best way to do that? I don't have any precise way to measure or make a template to take to them. Should I just drive the car over there and show them my problem?

Another option that I am tossing around is to order a set of DoubleC4's brackets since he is posting about running another set and just tossing all the 12" C4 crap on the front of my car.

[This message has been edited by zmcdonal (edited 10-22-2014).]

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Report this Post10-23-2014 08:25 PM Click Here to See the Profile for zmcdonalSend a Private Message to zmcdonalEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by zmcdonal:

Another option that I am tossing around is to order a set of DoubleC4's brackets since he is posting about running another set and just tossing all the 12" C4 crap on the front of my car.



Well I decided to ditch all the 12" C4 setup on the front of my car and order a set of brackets from DoubleC4 to put the C5/base C6 13" brakes on the front. I've already ordered a set of calipers and contacted him about the brackets. This just seems like a lot better end result, as far as quality of installation.

My 12" C4 setup will probably end up in the mall after I swap everything out if anyone would be interested.
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Report this Post10-24-2014 02:34 AM Click Here to See the Profile for jb1Click Here to Email jb1Send a Private Message to jb1Edit/Delete MessageReply w/QuoteDirect Link to This Post
good deal.....

------------------


87GTseries 1 3800sc (7.597 @88.53 1.579 60ft)
(series II swap in progress)
85GT Northstar/ 4t80e
86GT 3800 n/a---sold
Northstar Rebuild

[This message has been edited by jb1 (edited 10-24-2014).]

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