LT1 brakes

97 Trans Am daily driver
Goodyear F-245/45VR17, R-275/40YR18
Installing:SLP Level 1 suspension package and
Z06 calipers and rotors with metallic pads on the front. Need recommendation for rear calipers,rotors, pads and fluid.

Thanks
Frank

If this is a daily driver and ocassional track days car.... this is what I use.

I use Ford HD brake fluid. Cheap and has high boiling temperature rating. FORD HD is probably the best cheap fluid on the market at about $3+ a bottle. Others I know use and really like Motul 5.1, very good also just cost about $8+ a bottle.

For brake pads, I use Performance Friction Z-rated and Performacne Friction pfc90's. You can get eithe at Autozone - prices are $50-90.

As for rotors, I just use the Autozone lifetime guarantee ones at $30 a piece.

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96 Z28 M6-Lots of bolt ons!

Smitty's Speed Shop (http://www.neto.com/speedshop)
My 1996 Z-28 (http://www.neto.com/speedshop/james.htm)

Road Racing Pics (http://smittysspeedshop.cz28.com/msr.htm)

I'm using KVR. I'm really happy with them. They offer great performance and less dust than the stock ones did. Oh ya, good prices too.

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1993 red M6 Z28; custom control arms; bushings; strut bar; Eibach Pro-kit;17" rims & 275 tires; Mac exhaust; K&N cold air; airfoil; TB bypass; 3.73 gears; KVR pads & rotors; -1 camber alignment

Check my reply to you at LS1.com. Basically, if you're going to track the car, dump the LT1 front brake system altogether. It is poor-performing at best, and dangerous at worst.

Read the "Mov'it Brake Review" thread in this forum. Jon A was a believer in polishing the LT1 brake turd, until he ended up with his ass end in a dirt embankment because they overheated on him. Now he's got real brakes.


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Pat Newton
'97 Formula - unstock
'85 BMW 524 turbodiesel - stock and stinky
http://home.attbi.com/~patricknewton/f-body/formula.htm

I'll take a moment to self promote:

I'm the exclusive vendor for Bob Bishop's C5 brake adapter brackets. They are on backorder now but I can get you a complete kit with all required parts for under $900 shipped. Much, much cheaper than the Mov'it system and equally capable in my and Bob's opinions. I'm about to put them on my car as well.

Lots if info and pics are up at www.nashvillespeed.com (http://www.nashvillespeed.com)

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Owner, Nashville Speed & Performance (http://www.nashvillespeed.com/)

1996 Trans Am WS6 (http://www.nashvillespeed.com/projectcar.htm)

First let me say that I think the C5 upgrade is a very significant upgrade and for the price is a great value. I would expect most everybody that buys it to be very happy with it.

<font face="Verdana, Arial" size="2">Originally posted by Chris 96 WS6:
Much, much cheaper than the Mov'it system and equally capable in my and Bob's opinions.</font>

But let's be realistic, here. It isn't even in the same class as the Mov'it kit or for that matter the Brembo, Baer/Alcon or Stoptech big kits.

I could go on and on about pad area, swept area, rotor size, rotor design, caliper design, etc, but that's all been done before.

If the C5 brakes were in the same class, you wouldn't see threads like this:

http://forums.corvetteforum.com/zerothread?id=304452

http://forums.corvetteforum.com/zerothread?id=308897

http://forums.corvetteforum.com/zerothread?id=287224

http://forums.corvetteforum.com/zerothread?id=283810

http://forums.corvetteforum.com/zerothread?id=274020

...as you don't see them from people that have gone with the really big aftermarket kits. Also remember F-Bodies are a fair amount heavier than C5's.

Like I said, it's a nice kit at a very nice price. But let's not exaggerate.

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96 Z28 M6 (http://home.earthlink.net/~jonaa/Z28.html)
13.59 @ 102.96 (http://home.earthlink.net/~jonaa/Timeslips.html#2)
MODS (http://home.earthlink.net/~jonaa/Mods.html)

Ok, so then what is the best brake system available that uses 13" rotors, and why? What are the best pads to use with it, and what is the cost/frequency of rotor replacement?

The use is W2W roadracing, 1/2 hr sessions, with 3" cooling ducts.

thanks

BobC

Well, I feel the best 13" brake system is the Mov'it system or I wouldn't have bought it:

http://home.earthlink.net/~jonaa/MovitBrakes.html

Why?

One reason is they have by far the biggest pads of any of the systems at 76.5 square cm each. This will keep temps down as the same amount of heat being generated over a larger area will result in lower temperatures. And obviously, the pads will last much longer.

Then there's the swept area. Compared with these the C5 brakes (and many other 13" systems) only have the pad contacting the very outer edge of the rotors. What the larger swept area does is spread the heat out over a larger portion of the rotor, again, resulting in lower temperatures. (The big Brembo and Alcon kits do pretty well in this area as well.)

I think the cooling vane design of the Porsche rotor is better than anything else out there. Keep them cool and they will last.

And the caliper itself.... The older "Big Reds" were already stiffer than their Brembo counterparts. The Monoblocks are even stiffer and yet they are lighter.

What pads?

The Porsche guys seem to like Pagid pads. Orange, Yellow, etc, depending upon what type of racing they're doing. Simple open trackers like me can use stock Porsche street pads. No fade, plenty of stopping power, last a long time and are cheap to replace (cheaper than PF racing pads for my LT1 brakes were).

How long do the rotors last?

I've only had mine to the track once so I can't tell you personally. But the last time I talked with John (SweetSavannah) he had 16,000 miles, 18 open track days, and the 2001 One lap of America on his first set of rotors. He was on his third set of Porsche street pads. That helped influence my decision.

I don't know of any F-Bodies that wheel-to-wheel race with them yet, but it doesn't really matter to me. The components have been well proven by thousands of 911 racecars all over the world from the club racing level all the way up to the big time. And they are WAY faster than me.

Yes, they are overkill for me at the moment. But after my brake problems and all the money it cost me, I wanted overkill. I wanted the best. I wanted to be done with it.

Mission accomplished. I know if I double the HP of my engine and even start seriously racing in ITE, I'll have brakes that can handle it. The brakes are done. With C5 brakes and my future plans, they would not be.

You'll have to forgive me, although I'm reasonably well versed in brakes, I'm no expert. Let me just say for the price the C5 upgrade is hard to beat. Certainly there are better systems if you are willing to pay the price.

I had not even thought in terms of pad size and swept area.

The best feature of the C5 kit is cheap replacement parts. Yes the OEM rotors might not be bulletproof, but they are $50 each and widely available.

[This message has been edited by Chris 96 WS6 (edited June 17, 2002).]

I don't have a good brake setup yet, but if I did it would be the Brembo.

Louis Gigliotti has Brembo's on his LS1 Z28 and with over 80K miles he changed is rotors for the first time. I was there when he changed them and they were originally slotted and they worn beyond the slots and still working perfectly.

Now both the Brembo and Movit are out of my price range and I will be going with the C5 setup that is pretty hard to beat for the money.

Since I only do open track events also, this difference in price is hard to justify and currently my LT1 brakes aren't as bad as they are made out to be. I have abused the crap out of them and they have held up with zero problems.

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96 Z28 M6-Lots of bolt ons!

Smitty's Speed Shop (http://www.neto.com/speedshop)
My 1996 Z-28 (http://www.neto.com/speedshop/james.htm)

Road Racing Pics (http://smittysspeedshop.cz28.com/msr.htm)

When you see Viper guys throwing thier brakes away for Movits, then yes, it sure seems nothing beats the Porsche setup.

For $900 though, I would assume I'd just pass and go Wilwood for not much more.

Jon,

The pad area of the C5 calipers is 72 square cm ea. The Brembo pad area is 6 % larger; I wouldn’t say that is “by far”. The swept area of the C5 front brakes is 263 square inches. Since the pad area is very close, then the swept area will also be close for the same diameter rotor. If you want to compare a larger diameter rotor, then Doug Rippie has been offering a 14” diameter rotor for use with the C5 calipers for 4 years, but it would have many of the same problems that have already been cited: the rotor costs a lot more initially, it has a shorter life, it costs a whole lot more to replace, it requires the use of 18” wheels, you severely limit the # of people you can sell your car to because a GM dealer won’t do brake maintenance on it, etc. Most people don’t want to invest 20-25% of the value of their car on front brakes alone, and then have the upgrade lower the resale value of the car (unless you sell it to a fellow racer).

That Brembo rotor is probably the best rotor available, with cross-holes in it. Please don’t take this as a personal attack. I don’t even know you, but I admire the fact that you aren’t a cheapskate, and that you are very articulate. BUT, the elongating of the bolt holes to force a Porsche rotor to fit our bolt circle is poor engineering. When braking, all of the reverse torque is applied to the wheel lugs as side thrust from those 5 holes. Most of the “side” of the holes is missing. The torque would tend to walk up the bottom third of the hole side which remains, which would be the path of least resistance. There would then be a shear force applied mainly to the “corner” of the hole; holes should not have corners. I am not saying that the holes will wallow out with time, but that appears a possibility. If the rotors are the “floating” variety (as most Brembos are), then that possibility would be increased. It may not have happened yet on cars in your experience, but that proves nothing. If an elevator repairman cuts through 2/3’s of the strands of the supporting cable and demonstrates that the elevator still goes up and down without falling, I won’t accept that as a valid engineering analysis.

You provided links with posts from people defending the performance of the C5 brakes, and others who were proud of their expensive brake upgrades and felt they were necessary. Gary Hoffman won 1st place in 6 of the 8 Corvette T1 races he competed in last year, and set a new T1 lap record in qualifying at Lime Rock Park. He uses the stock brake system that came on his C5 with the addition of stainless steel pistons (available from Doug Rippie for less than $100). Those pistons transfer less brake pad heat to the brake fluid and are probably a good idea if you compete at that level. You can do a search for “Ghoffman” on the ZO6.com site to read his posts.

I am a believer in Brembo. Their floating rotor system is successful in multiple ways, and their monoblock calipers may be the best available. I am not convinced that Movit has done a serious adaptation of the Brembo parts to our cars. Their adaptor bracket uses only 2 of the 4 wheel bearing assembly bolts to locate and support the caliper. I question their engineering analysis there also. Those bolts are already doing a lot. Per GM, they are to be torqued to 63 lbs/ft, and the bolts are only rated to 64 lbs/ft maximum, if Movit supplies 12.9 property class bolts. That is the strongest bolt available in the 10mm size required. I supply 12.9 property class bolts. I’ve noticed that Baer supplies only 10.9 property class bolts there, which are rated for a maximum of 53 lbs/ft, 10 lbs/ft less than the GM torque spec. When it comes to safety, I also believe in overkill, as we all should. If the rotor holes and adaptor brackets prove adequate, I imagine that you will enjoy years of the best braking performance available for the Fbody. And, I am glad you weren’t hurt when your LT1 brakes let go.

Regarding Frank's original question, he is installing my front brake system and is asking for rear brake recommendations. I have already given Frank my suggestions privately.

Bob Bishop




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lateapex@worldnet.att.net
'94 Z28 with C5 front brakes and other road racing stuff

Thanks, Bob. I think I got off pretty easy from the crash compared with what might have been. I wasn't hurt, a bent axle and a couple thousand in body damage (that I haven't had done yet--that money went to the brakes! http://web.camaross.com/bb/wink.gif ) is pretty minor in the grand scheme of things. Most importantly, I learned many lessons that day.

OK, back to brake tech: http://web.camaross.com/bb/biggrin.gif

When I said pad area was bigger "by far," I was comparing it with all other 13" systems--not just the C5 system. The C5 caliper does have a large pad. The Brembo and Stoptech calipers have 62.5 square cm if I remember correctly and the Willwood has something like 54.

On swept area, it's more the width of the pad than the pad area that matters. The C5 pads get so much area by being really long which doesn't increase swept area. The Porsche pad is about 2 7/16" wide. Total swept area of the front is 323.5 square inches.

On the elongated holes in the rotors, no you wouldn't design them that way from the beginning, but I'm not worried about it. Here's why:

The reverse torque of the rotors is not being taken by the wheel studs in shear, bearing against the holes in the rotors. If it was you'd have threads in bearing which is a big no-no from the beginning. This is one of those applications on the automobile (along with about every bushing in our suspensions) that relies on the preload force from the clamp-up of the fastener and the resulting friction between the parts to fasten the parts together.

I don't have all the equations in front of me at the moment, but off the top of my head an M12, 1.5 pitch stud with a nut torqued to 100 lb-ft should provide around 10,000 lbs of preload. That's a total of 50,000 lbs pressing the rotor against the hub. The coefficient of friction between non-lubricated steel on steel is usually .6 to .8 depending upon surface finish...I can't remember if iron on steel is higher or lower but I don't think it's much different. Anyway, you're looking at something over 30,000 lbs of force being required to move the rotor before it would put any load into the stud in bearing once you bolt on the wheels.

The proof of this concept is as easy as looking at the stock system:

http://www.sfuller.net/misc/jona/Movit1.JPG

As you can see, the holes in the stock rotors are about 50% bigger than they need to be. This makes for a "sloppy" fit over the studs. With the stock system, if you remove the wheel you can move the rotor back and forth relative to the hub a fraction of a rotation and make the studs clank from one side of the big holes to the other.

For the studs to keep the rotor from moving in shear, they need to be in contact with the holes in the rotors. If this was happening, the rotors would clank to one side of the holes when you back out of your parking spot in the morning and would clank back to the other side the first time you applied the brakes while moving forward. This would be no good. A failure would occur shortly.

Thankfully, this isn't happening. Once you torque your lugnuts, the rotor doesn't move. The rotor hole surfaces won't see any compression against the studs.

Usually friction is the enemy...but sometimes it can be your friend. http://web.camaross.com/bb/wink.gif

On the brackets, I wouldn't mind if they picked up all four bolts of the hubs but I don't think it's needed. With a 2 piston sliding caliper, the bracket is going to see significant side loads. It needs the extra two bolts to give some leverage against the resulting moment or you'd be popping the heads off the first two bolts.

But with a 4 piston fixed caliper, the side loads should be negligable. All they need to react is the radial torque. Apparently they're adequate. The brackets are very similar to OEM Porsche brackets and Brembo, Stoptech and Alcon use the same type of bracket for many different applications. Here's one example:

http://www.europeancarweb.com/images/content/0801/stop05.jpg

Mov'it supplies 12.9 grade bolts.

On the links I gave, that was kind of just a hodge-podge of C5 brake discussion. Some say the stock stuff works great, some go through a set of rotors every weekend. It's one of those things where your mileage may vary. http://web.camaross.com/bb/wink.gif I think many of the discrepancies are due to people running different tracks (some harder on brakes than others), driving styles and/or skill levels, street tires or race tires, power level of the cars, etc....

The point I was trying to get accross was that nobody with the Mov'it upgrade goes through a set of rotors in a day or two or through pads so quickly. And much of the same can be said for other big brake kits.

Like I said in the first post, I do think the C5 upgrade is a very significant improvement. And for the price it's a hell of a Bang for the Buck.

I just wanted to make clear that with the "big money" systems you are getting a bigger bang for those extra bucks. Most may not need it or want it for the cost, but there is a difference for those who pay for it.

[This message has been edited by Jon A (edited June 21, 2002).]

Jon,

Your point is taken on the bolt holes, but it still looks like a “homemade” solution. If any lug nuts were to loosen or weren’t torqued adequately to start, I expect that things would get more catastrophic quicker by not having concentric bolt holes.

The picture you linked of the Stop Tech package isn’t applicable to your point. That bracket doesn’t piggyback on the wheel bearing bolts, it merely extends the factory caliper mounting point a short distance. The bolts used to attach that bracket would have much less mechanical advantage working against them, would be performing no other function, and have no other stresses.

Also, there would be LESS side force applied to the C5 adaptor bracket because of the fact that it is a floating caliper which naturally centers itself around the rotor.

On a 14" rotor, the C5 calipers provide 296 square inches of swept area. I probably would't use that large a diameter in a rotor only 1.25" thick with a car as heavy as ours. The extra thickness of your rotors has many advantages as you know. The only downsides I know of would be expense and weight. Lingenfelter had 1.32" thick Alcon rotors on their "1 lap of America" car a few years ago. I called them the day I read the article and said I wanted those brakes. Of course, the thicker rotor requires a caliper that allows for it. All told, it was going to cost me $6000 (and that was 5 years ago)for the front brakes, and a 3 month wait to get them from England. I passed on them.

I think that the dialog is good. We could all use to think more comprehensively about the “improvements” we plan to make to our cars, especially if they are used in a racing environment. Pooling everyone’s knowledge and experience benefits us all.

Bob Bishop




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lateapex@worldnet.att.net
'94 Z28 with C5 front brakes and other road racing stuff

[This message has been edited by lateapex (edited June 21, 2002).]

I'd sure love to have the Movit system but unfortunately I will have to make do with the C5 upgrade.

I'm curious about the rotor you got Jon. I'm familiar with the 2 piece 322mm rotors from the 993TT but what are yours from? I thought the 996TT with the monoblocks used a 2 piece rotor?

George E.

George,

The 322x32mm 2 piece rotors were used on the 993 Turbos with the older two piece style "Big Red" calipers. For the 996 Turbos they went to the 330x34mm one piece rotors along with the newer Monoblock calipers. Here's a pic of them on a 2001 GT3:

http://prospeedmotorsport.com/Brakes/Graphics/Large/GT3-3.jpg

Those are the same parts that are on my car. Other than being one piece, the basic design of the rotor looks to be the same (cooling vanes, etc) the newer ones are just bigger.

Bob,

Good point on the bolts now doing double duty. That's definatly true. But the loads on the bolts due to the brakes will depend upon the spacing between the holes as well as their distance from the caliper. It won't matter to what they are bolting. The pic I posted of the Stoptech brackets does look like the holes are slightly closer to the caliper than my brackets, in which case they would see smaller loads (if the spacing between the bolts is the same). Obviously this will vary from application to application. I was only trying to say they are all using the same basic idea even if the dimensions are slightly different from car to car.

On the side loading of the bracket, this is what I was thinking:

For a floating caliper to press the pads into the rotor, it needs to slide. Once braking has begun, the radial torque puts a side load on the sliding pins. With this side load, the pins will develope friction and resist movement. The force resisting this movement will have to be reacted by the bracket. But, I have no idea just how big this force would be.

On the other hand, the 4 piston caliper will be centered to within a few thousandths when mounted (Mov'it provides shims). And there it stays. Even if off by a little bit, the pistons will take up the slack the first time you pump the brakes and they press the pad against the rotor. From that point on, when you hit the brakes you're putting the same pressure on the same sized pistons which will result in the same force being applied to each side of the rotor.

So, the forces will cancel out. I don't see how the calipers could put any side load on the bracket that would be large enough to even be mentionable.

I agree, discussions like this are a good thing for everybody. A great learning tool for everybody (myself included!).