I FINALLY installed the 12 inch rotor upgrade that I bought from RockCrawl 2 years ago. Nothing like procastinating. Anyway, nothing wrong with the kit (i think). Got everything bolted up and spun the wheels. Everything was fine, the fronts were alittle tight, But I thought it was the new pads. Well, took it for a spin, and not even getting it out of the driveway there was a hella scraping and grinding coming from the fronts. Long story short, seems the brake caliper slider bolts are too long? They are digging into the brake rotor. I got new bolts awhile ago, I believe from Fiero Store. Are they longer then the OEM bolts I wonder? Anyone else have this issue?

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1988 Purple Fiero GTw/SC3800 conversion
Best ET with 3.0 pulley,XPHOT cam, SS I/C and 105lb Valve springs: 12.38@110mph
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I put a set of brake calipers onto a '86 Fiero that were remanufactured (A1 Cardone brand) and they had slider bolts that were too long and would have done the same thing as you noted with your bolts. So, I guess that when they were rebuilt, they installed bolts that are too long?

I just pulled them out, went down to Advance Auto and got a new set of slider bolts for the Fiero, put 'em in, and everything was like it should be.

-Chris

I'll Have to check the local store then. The Four bolts on Front are definitely new, they are torx instead of hex headed and they are still shiny black.

If I remember correctly, the slider bolts for the rear calipers on '88's are slightly longer than the front bolts. Is it possible you mixed them up when rebuilding?

Are you sure it is the caliper bolts?

Several 88's, especially lowered ones have an interferance issue between the lower A-arm and the rotor (regardless of supplier of the kit). As the suspenion is loaded and the A-arm moves up, the nose of the A-arm can dig into the rotor. It is easily fixed by using a grinder to clearance the nose of the lower A-arm.

BTW, the caliper bolts on the 88's are torx - from the factory.

[This message has been edited by fieroguru (edited 06-06-2009).]

Is it true the slider bolts are different lengths??? Ok, then I am mixed up a bit. The rear slider bolts are ( 1 Hex head, 3- 50 torx), the fronts are 4 torx, larger then a 50, probably a 55 but I had to use a hex head socket because I left my 55 Torx at work.
There is a grove cut into the center of the rotor on the inside from whatever is cutting into it. I was so pissed I didn't take the wheel off or anything, just looked it over. Just let it sit till tomorrow.

quote Originally posted by SOULCRUSHER: Is it true the slider bolts are different lengths???

If they are, I have never noticed it... I will have to check in the morning. I can even take a pic of my gouged up roater as well.

[This message has been edited by fieroguru (edited 06-06-2009).]

WE HAVE A WINNER! After fieroguru made the statement about the lower control arm and lowered 88's I went out with a flashlight and looked a bit closer. You are right, it is the lower control arm digging into the rotor! Should have looked closer, as mine is lowered with springs and lowering balljoints. This sux. So I can just grind away the tips of the lower control arms?

[This message has been edited by SOULCRUSHER (edited 06-06-2009).]

Yes, you can grind away some material from the nose of the A-arm to gain additional clearance, but the lowering ball joints might be problematic since they move the ball joint pivot an additional 1" (or whatever size they are) away from the A-arm centerline which means the nose of the A-arm will move towards the rotor at a faster rate than stock. This is only really an issue once the A-arms begin to pivot upwards which the lowering balljoints will lessen, but once they do start pivoting up the A-arm will hit the rotor much faster than stock. You should disconnect the sway bar links and use a jack to load the suspension and see how much material you are needing to remove.

Also, with the caliper spacer moving the calipers towards the center of the car about 3/8", the calipers rotating up via the adapter plates and the upper a-arms at an ever increasing upward angle as the front is lowered, the caliper slider sleeve can hit the upper a-arm and reduce the turning radius as well as pinching the front brake line.

I ended up clearancing a portion of the upper A-arm to regain some of the lost turning radius when my 88 was this low:


I have since raised the car some, but even at this height my stock 88 can still turn a much tigher radius than my lowered 88 with the 12" vette rotor upgrade:


When I get home this morning, I can post pics of a stock lower A-arm, and the modified lower and upper A-arms on my 88 (it is up on jackstands with the wheel off at the moment).

quote Originally posted by fieroguru: Are you sure it is the caliper bolts?

Apologies, apologies! It's NOT the slider bolts that are different lengths. It's the caliper to mounting bracket bolts that are different front to rear. The rears are longer to accommodate the extra thickness of the e-brake brackets.

Glad to see you found your problem.

Here is a stock 88 lower a-arm. Notice how the nose points out slightly at the bottom corner:


Here the lower corner of the nose was ground down and rounded so it would not hit the rotor - this pic is at full droop and the a-arm will be closer at ride height.


With the suspension at full droop, turning the wheel to full lock puts the brake line and the caliper slider under the upper A-arm. You can see the notch I made to gain more turning clearance, but it still limits turning radius vs. stock.




As you can see there is no binding at full droop (aside from the brake line bending), but as the suspension is compressed the upper A-arm will pivot down and it and the caliper will be fighting over the same space. The more the car is dropped, the further the A-arm will pivot and the more interferance it will have with the caliper.

The issue with the rotor and lower A-arm interferance is not vendor specific. It has to do with the lower a-arm design and the mounting depth of the C4 rotors. There is some variation from car to car and side to side, but for the most part this issue shows up more often on lowered fieros that stock ride height.

The issue with the caliper and upper a-arm interference is due to adaper thickness (bracket design), amount the caliper is rotated upwards (bracket design), and the degree of lowering. My setup is from WCF and they rotate the caliper up quite a bit in the front. At the rear they countersunk 1 of the holes to allow the caliper slider to partially cover it and rotated the caliper less (might just have to try swapping the brackets front to rear to see what happens).

I think these are fieroaddiction brackets, and he countersunk all the bracket to knuckle bolts and kept the calipers in the stock position (no rotation of the mounting point. These might not have any interferance issue with the upper A-arm:

[This message has been edited by fieroguru (edited 06-07-2009).]

quote Originally posted by fieroguru: The 88's do not have caliper brackets in stock form (you do install them for larger rotors). The caliper bolts directly to the uprights/knuckles front and rear and the e-brake bracket bolts directly to the caliper via the bolt that holds the 2 halves of the caliper together. Aside from the e-brake mechanism, the 88 calipers are the same front to rear - you can even run the front calipers on the rear if you wanted to eliminate the e-brake.

I don't know where my head is today. You're absolutely right fieroguru. The bolts I have unsuccessfully referred to in two(!) posts now are not the ones I meant either time! The bolts I've been meaning to describe are in fact the caliper halve bolts. They are different in length by about 5mm, with the rear caliper ones being longer than the fronts. This much I know for sure since I accidentally mixed them up thinking they were the same. If you put the longer bolts in the front calipers, they protrude that extra bit through the steel half of the innner side of the caliper towards the rotor. Not enough to make contact with the rotor, but if you've bought new bolts and they're yet an extra 5mm longer than the rear caliper bolts, and put them on the front, I guarantee you'll have clearance issues. Again, the reason for the different lengths is to accommodate the extra thickness of the e-brake brackets. Sorry for hijacking your thread Soulcrusher.

I was about to post this, so I'll do it anyway.

You need to clearly differentiate between the '88 Caliper Attach Bolts (Torx T55 head) that go through the slider pins, and the Bridge Bolts (external hex head) that attach the cast iron bridge to the aluminum caliper body. It is the Bridge Bolts (not the caliper attach bolts) that also attach the e-brake cable brackets to the rear calipers, so those may indeed be longer in the rear than in the front.

FWIW, the torque spec is the same for all '88 Caliper Attach Bolts and Bridge Bolts: 75 ft-lb. This is particularly important on the '88 Fieros, because the Caliper Attach Bolts have a nasty habit of backing out if not properly torqued. That said, I have never seen a properly-torqued '88 Caliper Attach Bolt loosen ... but I still highly recommend using a drop of blue thread locker when attaching the caliper to the knuckle, just to be sure.

OK, got the old grinder out and annoyed the neighbors. Got things straightened out now. Ground down the tips of the lower control arms. The trick is to jack up on the arm to check for clearance. when there is no load, everything looks like its clear. But like Fieroguru said, I DO NOT have the issue with the caliper hitting the upper arm when the wheel is locked left or right. I am using the Fiero Addiction kit. THANKS FOR ALL THE HELP!

quote Originally posted by SOULCRUSHER: WE HAVE A WINNER! After fieroguru made the statement about the lower control arm and lowered 88's I went out with a flashlight and looked a bit closer. You are right, it is the lower control arm digging into the rotor! Should have looked closer, as mine is lowered with springs and lowering balljoints. This sux. So I can just grind away the tips of the lower control arms?

Somebody posted about this problem some time ago- using lowering ball joints causes the interference inside the Vette rotors when doing this brake conversion. I was originally going to use Rodney's lowering ball joints but went with springs instead because of this reported issue.

Bump.

Since FieroAddiction seems to be no longer in service, someone should pick-up on the production of the '88 brake adapter kit.

Gosh darnit I had things I wanted to order from there booo

Soulcrusher, do you have any picts of how much you ground down your lower a-arms? I managed to get most of the rubbing to stop by pounding in the tip of the a-arms with a sledge, but it still does it under load while turning sharply. I may decide to grind/cut it down some in the near future. Here's a pic of mine from my build thread where I briefly discussed this problem:

would placing a thin, maybe 1/8", hub spacer work?

I was thinking that would be a safer bet, spacers.

I've heard of this problem before on one 88 but hadn't seen it until now. Interesting, I have the C4 rotors on one of my 88 Formulas but have never had an issue but, it isn't lowered and has no grinding A arm. Hmm, will have to look at this closer on the next installation. Thanks, interesting thread.

Ron

[This message has been edited by blackrams (edited 07-25-2009).]

quote Originally posted by fieroguru:

Is it necessary to do the additional counter sink machining on these adapters? Or, do the bolt heads create interferance to the calipers?

quote Originally posted by Amida: Is it necessary to do the additional counter sink machining on these adapters? Or, do the bolt heads create interferance to the calipers?

Yes it is required because the caliper slider will overlap the counter sunk bolt head slightly.

quote Originally posted by fieroguru: Yes it is required because the caliper slider will overlap the counter sunk bolt head slightly.

I see that's why the WCF bracket moves the caliper location to clear the bolt heads, but it created another clearance problem with the caliper hitting the front upper A-arm at full turn. By counter sinking the mounting bolts the calipers do not need to be moved/rotated on the rotors.

[This message has been edited by Amida (edited 07-25-2009).]

quote Originally posted by Amida: I see that's why the WCF bracket moves the caliper location to clear the bolt heads, but it created another clearance problem with the caliper hitting the front upper A-arm at full turn. By counter sinking the mounting bolts the calipers do not need to be moved/rotated on the rotors.

Correct. Eventually I will get around to making a set of adapters similar to FieroAddiction and do away with my WCF set.

I just read that Funnywheels on Madmechanics made his adapters from 1/2" steel & machined down the bracket to spindle surface to 3/8". The caliper bolt holes are then tapped instead of welding on nuts to the backside. If he also counter sunk the spindle holes I think this might be the best design. Any thoughts?

quote Originally posted by Amida: I just read that Funnywheels on Madmechanics made his adapters from 1/2" steel & machined down the bracket to spindle surface to 3/8". The caliper bolt holes are then tapped instead of welding on nuts to the backside. If he also counter sunk the spindle holes I think this might be the best design. Any thoughts?

There is no such thing as "best design" - every method has compromises and it is a matter of personal opinion/bias as to which compromise is best for you.

My WCF set is 3/8" steel plate with the holes threaded in the steel (no welded nuts). When I make my own set, I will use the 3/8" steel and thread one set of holes, counter sink the other and not rotate the caliper. Very similar to the geometry of the FieroAddiction brackets with thicker material and w/o the need to weld on the nut. These would be quite simple to fab up with a sawsall, grinder and drill press in an afternoon once I have the pattern lined out (but i have no intentions of making these to sell).

Simplicity of fabrication rates high on my compromise scale.

Thank you for this thread. I just went for a drive in my 88 Fiero with the WCF C4 12" kit and the 1" Rodney Dickman ball joints and it rubs. My first thought was that both bearings went out. I will grind away some of my a-arm tonight after I put the kids to sleep.

I don't have this issue but i was just wondering if heating the end of the a arm and the hammering the clearance needed wouldn't be better than just grinding off the edge. It should leave the arm stronger than cutting off the lip. You might have to remove the ball joint to protect it from the heat, or you could wrap it with a wet rag to keep it cool....

Just a thought.

Ran into this problem too. http://tinyurl.com/ybrgh9g

Was thinking the same as below. Does anyone have any photos of how much they grinded off the lower "A" control arm?

quote Originally posted by Sebringdcp: I don't have this issue but i was just wondering if heating the end of the a arm and the hammering the clearance needed wouldn't be better than just grinding off the edge. It should leave the arm stronger than cutting off the lip. You might have to remove the ball joint to protect it from the heat, or you could wrap it with a wet rag to keep it cool.... Just a thought.

quote Originally posted by FierociousGT: Does anyone have any photos of how much they grinded off the lower "A" control arm?

This was posted several posts above:

quote Originally posted by fieroguru: Here is a stock 88 lower a-arm. Notice how the nose points out slightly at the bottom corner: Here the lower corner of the nose was ground down and rounded so it would not hit the rotor - this pic is at full droop and the a-arm will be closer at ride height.

quote Originally posted by Sebringdcp: I don't have this issue but i was just wondering if heating the end of the a arm and the hammering the clearance needed wouldn't be better than just grinding off the edge. It should leave the arm stronger than cutting off the lip. You might have to remove the ball joint to protect it from the heat, or you could wrap it with a wet rag to keep it cool.... Just a thought.

Aren't the A arms Tempered and wouldn't heating it remove that Temper? Please correct me if i am wrong.

I did see those fieroguru. Hard to tell. I actually hit it in with a hammer. will post photos later.

EDIT:
Great I just noticed that there might be an issue with the brake caliper and the upper "A" control arm. Is all this due to Rodney Dickman's lowering ball joints or due to the adapter bracket?

quote Originally posted by fieroguru: ....... Also, with the caliper spacer moving the calipers towards the center of the car about 3/8", the calipers rotating up via the adapter plates and the upper a-arms at an ever increasing upward angle as the front is lowered, the caliper slider sleeve can hit the upper a-arm and reduce the turning radius as well as pinching the front brake line. I ended up clearancing a portion of the upper A-arm to regain some of the lost turning radius when my 88 was this low: I have since raised the car some, but even at this height my stock 88 can still turn a much tigher radius than my lowered 88 with the 12" vette rotor upgrade: ........

[This message has been edited by FierociousGT (edited 01-28-2010).]

quote Originally posted by FierociousGT: EDIT: Great I just noticed that there might be an issue with the brake caliper and the upper "A" control arm. Is all this due to Rodney Dickman's lowering ball joints or due to the adapter bracket?

It is a bracket design issue and is the same for the WCF design and all the ones that copied it... It tends to show up more on the cars that are extensively lowered in the front (with either lowering springs or lowering balljoints). The latest version of FieroAddiction's brackets moved the bracket out w/o roating it up at the same time and fixed the issue, but those are no longer made.

I've started to make these bracket packages. I've been working with FierociousGT on his install, debugging design issues. Additionally I've been consulting with Fieroguru since he's installed several sets of these.

I'll keep you posted with what I find and pictures. Reading this, I'm inclined to develop a separate "front" and "rear" package, but let's see how the debugging goes. A "common" design would be more usefull if it's possible.

Marc

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Marc in sunny Titusville, FL

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quote Originally posted by fieroguru: I think these are fieroaddiction brackets, and he countersunk all the bracket to knuckle bolts and kept the calipers in the stock position (no rotation of the mounting point. These might not have any interferance issue with the upper A-arm:

Thanks for the info - I have those brackets in a box in the garage and couldn't remember what they were for exactly.