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  1. #1
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    Discussion of rotor diameter (from old site)

    DLinson
    Unregistered User
    (10/15/03 11:11 am)
    Reply Opinions on rotor sizes
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    For my Nova I bought 11 3/4" x 1.25" rotors fro the front and I have factory 96 Camaro rear bakes and rotors. The front calipers are Willwood Superlite IIA 4 piston. The pistons are 1.75 bore. I bought the brakes back when I was planning on using 15 inch wheels. I have made custom from spindles which are completed and painted.

    My question for you all is, do you think I should get 13.5 inch rotors for the fronts and 13 inch rotors for the rear? This would mean modifying my custom front spindles which would require a lot of work and making new rear brake brackes. I would plan on using the same calipers front and rear. Do you think it would actually help out in stopping performance or is it mainly a cosmetic issue.

    KacyZ28
    Registered User
    Posts: 68
    (10/15/03 11:56 am)
    Reply re
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    remember the bigger the rotors requires bigger wheels

    Ralph L
    Registered User
    Posts: 1725
    (10/15/03 1:44 pm)
    Reply
    Re: re
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    if you want a bigger rotor, check out wilwoods new 6 piston 14 inch brake system for the C5 vette, its the same caliper that is on my system for my first gen cam, but with a 14 inch rotor, instead of a 17 inch rotor, when my rotors go, if ever i will be switching to the 14 inch rotor as well.

    later,
    Ralph
    "Project Phantom"
    My Tahoe

    conekiller13
    Registered User
    Posts: 578
    (10/20/03 10:28 pm)
    Reply Is bigger better?
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    Bigger diameter rotors will most defanetly improve braking. The increase in swept area with a bigger rotor is exactly what gives the big brake kits there worth. It will require a bigger wheel for sure. A 13.5 may require a 18" wheel depending on how big that caliper is. You may or may not have noticed that Road and Track magazine has added swept area/ton to it's spec lists as a comparable measure of brakes between vehicles. As far as rotors go.............the bigger You can afford, the better.


    Dan

    Rick Dorion
    Registered User
    Posts: 383
    (10/21/03 5:31 am)
    Reply Ralph
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    Wow, Ralph, a 17 inch rotor!

    Ralph L
    Registered User
    Posts: 1759
    (10/21/03 5:59 pm)
    Reply
    Woopsie!
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    Rick, I meant 13 inch rotor!! DOH!!
    Ralph
    "Project Phantom"
    My Tahoe

    walapus
    Registered User
    Posts: 68
    (10/22/03 10:47 pm)
    Reply big brakes
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    Just so you know:

    Larger rotors won't necessarily make a dramatic difference in an isolated panic stop circumstance. If you can already lock up your front wheels, your brakes out-power your tires. Your tires stop your car, not your rotors. In order to make the best stop, you would actaully be feathering the pedal. With the bigger brakes, you would just be feathering more lightly. I can't remember which magazine it was (maybe chevy high performance?), but they did a big brake upgrade and made the mistake of printing before and after results. The return on their investment: 4-6 whole feet from 70-0. "but they sure do feel better". Hardly worth the $1200.

    Big rotors DO give big returns for repeated braking and/or high speed braking, which is why the race cars have gargantuan brakes. Brakes are energy dissipaters. High speed=high energy=more dissipating requirement. In the above example of a panic stop, if this stop is performed at high speeds, then halfway through your stop with stock rotors you may be cooking your fluid and loosing stopping power, whereas with an upgraded rotor you still have most of your intial torque available. Most of the street people who install big brakes don't ever actaully need them. So, if your going to race or drive down the freeway at 120mph, then by all means go for big rotors. But if you mostly cruise to work and back, ask yourself how many times you've really warped your rotors?

    www.stoptech.com/whitepap...122701.htm

    walapus
    Registered User
    Posts: 70
    (10/23/03 10:14 pm)
    Reply PS
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    My spelling stinks!!

    conekiller13
    Registered User
    Posts: 581
    (10/24/03 9:44 am)
    Reply Bigger
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    Larger diameter rotors are also less prone to lock up. A small rotor will be spiked into a lock up condition in a panic stop. A large rotor with more surface are will resist this pressure spike and slow more rapidly with as much tendacy to lock up. Most defantly though Repeatablity of stopping distance is reason #1 for large rotors.



    Dan

    gmachinz
    Unregistered User
    (10/24/03 10:44 am)
    Reply RE:Bigger
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    Dan, following up on what you just said do you think then that huge rotors (13 or 14" diam.) are overkill for the street-mainly for looks? I mean, if better stopping distance is what the main benefit is, at speed are we talking? Surely not 60-0 between city blocks? Some brake pads, for example that are strictly for race use are not recommended for the street because a street car will not see the kinds of speed required to see the full advantage of said "race pads". So can this arguement be made in the case of huge rotors? Sure, it helps IF you ever can take your car 160mph and then slow it to a halt-but for the average street car I would suggest they are perhaps race functional-but not for the street. My point is-properly tuned, won't a standard (right now, anyway ) 12" rotor front and 12" rotor back combo work just as well as a Baer or Wilwood 14" brake kit-for the STREET? I'm not trying to counter what you're saying, I'm merely trying to understand why people choose the products or systems they do. Thoughts?

    conekiller13
    Registered User
    Posts: 584
    (10/24/03 4:57 pm)
    Reply Size does matter
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    With all other factors being the same(calipers and pad compounds) larger rotors WILL noticably improve panc stopping distances. Anywhere from 5 to 20 feet at 60 mph. Is that very much? If You need and it's not there then...........I would say that big rotors are installed more for looks than performance but brakes and wheels on production cars keep getting bigger for a reason. Look at how many cars are comming with 17 to 18 inch wheels and 13" or bigger brakes stock. Take a look at Baer's web site and the info on their system for late model trucks with 18 or bigger wheels. It's a perfect example of the differnce rotors alone make. Pad compound is much specific to street and track. Most race pads don't work untill they get to race temp. At cooler temps they have increased distances and can be very high wear on the rotors. You can certainly get better than stock performance from better street compounds but a "big" brake system is defenatly worth the expense.



    Dan

    protour2001
    Registered User
    Posts: 15
    (10/24/03 7:53 pm)
    Reply Gotta disagree
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    Conekiller, I gotta disagree about large rotors being less prone to lock up-the amount of pressure placed on the disk is strictly hydraulic pressure applied and caliper piston area. That, or your tires can't apply the braking force to the ground. The size of the rotors doesn't have an effect. Read the Stoptech link above, it's good.

    protour2001
    Registered User
    Posts: 16
    (10/24/03 8:17 pm)
    Reply Re: Opinions on rotor sizes
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    Just another interesting link. www.zeckhausen.com/testing_brakes.htm

    pdq67
    Registered User
    Posts: 188
    (10/24/03 8:34 pm)
    Reply xx
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    Heck, 17" rotor's!!

    I saw a SUV with 22" rims on it at one of the local ACE Hardware stores while I was gathering bolts and such to finish my front "pdqCBB" setup today!!

    So why not!!

    pdq67

    DLinson
    Unregistered User
    (10/24/03 9:13 pm)
    Reply Brake Rotor Opinoins
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    Thanks all for the input. I doubt I'll be doing any high speed racing events at least for the first year. I may do some autocrosses so the big brakes probably won't be needed there. I probabaly won't go to a track for the first year but the next year I'll probably hit the Ferrari track day in St. Louis. A friend at work takes his Vette to it every year and they let in all kinds of cars just to get the cost down.

    Anyway, I may hold off till next winter to add the 13" rotors and stick with the 11.75" rotors. I have plenty of other things to get done if I want to finish the car before next summer.

    Thanks again everyone.


    Rick Dorion
    Registered User
    Posts: 389
    (10/25/03 4:37 am)
    Reply Re: Brake Rotor Opinoins
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    A good thread. In the 0-100-0 articles, I've been reading some good perfomances with fairly stock front disc/rear drum setups. I'm hoping my 12" front/drum rear setup will provide good street performance. Even on my truck, I've seen good improvements with pad choices. I put Hawk pads ( HPS I think) on my brother's Miata. Really didn't expect much but he called back after driving home to say he was very pleased with the improvement. I'm going to try them on my camaro.

    jon sikora
    Unregistered User
    (10/25/03 8:50 am)
    Reply x
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    i would suggest good brake cooling ducts,temperature indicating paint,and pads appropriate to your intended use.wider,stickier tires will have the most effect.

    Mrfspdwrks69SS
    Registered User
    Posts: 45
    (10/25/03 9:26 am)
    Reply Welcome back Jon
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    Hey Jon,
    Welcome back to the board. Missed your imput on the many topics that have been discussed here on Pro-Touring.
    Mike
    Metal Works Performance Engineering
    12540 West Cedar Drive
    Lakewood, Colorado 80228
    (303)980-4700

    conekiller13
    Registered User
    Posts: 586
    (10/25/03 7:09 pm)
    Reply Size
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    What makes the larger rotor less prone to lock up is mechanical advantage. The increase in surface area in effect makes the rotor a longer lever. It's not that they won't lock up up but that it's eaiser to modulate them. Any properly functioning brake system can be spiked into lock up, I.E. panic stop. The larger rotor wants to keep spinning so it slows down rather locking. It's like the flywheel keeping the engine running when Your off the throttle. It's simple physics.


    Dan

    protour2001
    Registered User
    Posts: 17
    (10/25/03 7:37 pm)
    Reply Re: Size
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    I still feel that caliper design/implementation is far more important than rotor sizing(within reasonable limits, of course). Dan you say "the larger rotor wants to keep spinning"-that's inertia and it would lengthen braking distances, I would think. Kinda like all the SUV guys putting 22" wheels on that weigh 90 lbs and wondering why the braking (and acceleration!) performance goes down. Just my .02.
    Brian

    Edited by: protour2001 at: 10/25/03 8:18 pm

    conekiller13
    Registered User
    Posts: 589
    (10/25/03 8:24 pm)
    Reply ...
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    Brian,

    Inertia is what makes the trucks with those big wheels stop worse. That inertia is due to the increase in mass given by those wheels. Most of those wheel and tire packages wiegh about 120lbs per corner. The larger rotors provide more leverage against this increase in mass. The best exmple of this is on Baer's site. The kit they have for SUV's usue nothing but a larger diameter rotor. They test the stock brakes with stock wheels and tires, then stock brakes with 22" wheels and tires and then bigger rotors on the same 22" wheels and tires.........same pads, same calipers, didn't even bleed the brakes. The stopping distance with the large rotor was better than not only the stock brake and big wheels but also the stock brakes and stock wheels. That to Me is proof positive that larger rotors do indeed make a differance.


    Dan

    andrewb70
    Registered User
    Posts: 1727
    (10/25/03 8:50 pm)
    Reply
    Re: ...
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    I am with Dan on this one. Also keep in mind that most large (14+) inch rotors are a 2 piece design. My 14 inch rotors with the aluminum hats weighed less then the 13 inch all iron rotors. I definitely feel that my large rotors greatly contribute to the effectiveness of my brake system. I wish there was an easy way to measure how well my brakes work. Any syggestions?

    Andrew
    Project GatTagO



    67Sally
    Registered User
    Posts: 224
    (10/26/03 5:34 am)
    Reply Re: ...
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    DIg out the original rotors and claipers from the old GTO and bring your RSE pit crew to the next event and have them swap them out for you between runs.
    William
    Project PonySnake - 67 Mustang Fastback

    gmachinz
    Unregistered User
    (10/26/03 5:37 am)
    Reply got any before/after info??
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    Andrew, did you get a chance to do any before/after skid pad tests with you GTO before going all out on the brakes-such as just the stock disc/drum set-up?
    One thing I wonder is besides the weight of the brakes themselves and the larger rotor acting as a larger lever (I agree), what about actual vehicle weight acting upon those brakes as well when you decide to "panic stop"? I mean, the forward inertia of some vehicles (such as yours, Andrew) have quite a bit more than Camaros or even G-bodies. To me, I guess I would focus on front/rear brake bias as it relates to vehicle weight first. Then factor in amount of torque/HP since rapid acceleration must be proportinate to rapid de-celeration and then finally-tire choice. Would you agree that is the most basic starting point when deciding on brake systems?

    protour2001
    Registered User
    Posts: 18
    (10/26/03 7:58 am)
    Reply size
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    Dan, you're right, on an underbraked vehicle anything is a definate improvement. I wonder how dramatic Baers test would be if they started out with a 3200 lb car with 12" rotors and swapped in 14's? Don't get me wrong, I definately agree that big rotors make a differance, I just think it's relatively minor compared to caliper design and tire technology. I'm really not trying to start something, believe me, I just think everyone follows the mantra of bigger is better on this subject. Mercedes puts 14" rotors on the E55 for a good reason, but what is the rotor size on the new Lotus(forgot the name)? or any formula car? Lighter cars don't gain as much benefit, compared to other system upgrades that are possible.

    Andrew good point (and a slap to the forehead) about the 2 piece rotors, I missed that point. Of course that takes away one of the major drawbacks of bigger rotors(weight).

    Please don't think I am anti big brake, or trying to start something, I just think people tend to follow the "accepted" knowledge when most of the time that "knowledge" comes from companies trying to move product. I remember when Baer used to say that crossdrilling was not necessary-now that 80% of their sales are crossdrilled, they don't.

    Oh and here's my next brake kit! www.impalassbrakes.com

    walapus
    Registered User
    Posts: 75
    (10/26/03 9:19 am)
    Reply big brakes
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    Exactly. Bigger brakes CAN be helpful, but they are not always the MOST helpful. My guess is, if you have to ask IF you need bigger brakes, but don't have any specific reason to ask (warped rotors, fade, etc), then you probably do not need them. I think protour2001 is right about the SUV test, they made a large difference becuase of the gigantic amount of dead weight from the wheels forced the issue.

    When I was on the Formula SAE team at my college, the brake and suspension guys were pushing for smaller, not larger. This is of course the exact opposite of the SUV situation, since that car was incredibly light. But the point is, there is such a thing as too small, but there is also such a thing as two big.

    And, just becuase a 14" rotor weighs a tad less on the scale isn't the only consideration. The mass of the brakes contribute to your unsprung mass, and of course less is better. But, those two piece rotors shave all their weight at the hub, which is small in radius. This means you've still got a ton of weight out at the large radius, which equals more rotational inertia (prop to m*r^2!!!) which means possibly slower acceleration and more required effor for deceleration.

    I tend to agree that, especially if you've already upgraded your rotors once, a good set of brake pads and and better tires will do more for your stopping distance than further increasing rotor size, will help you in acceleration, and will save unsprung mass for better handling. Better calipers, as I understand it, will help in brake feel and modulation but not out-and-out performance. After the transient deflection of the caliper has taken place (fractions of a second) then it's down to the basic physics again, just as if it never deflected. It may make slight differences due to pad misalignment if the deflection is drastic but there again if you've already got the ls1 12" setup you're in pretty good shape in that area.

    In my head, I've even almost talked myself out of installing my 12" setup at times, since most of the time I drive like a wuss to work and back. I'll have to change my wheels too (which I just got new tires for, dang it). Who I am kidding, of course I'll still install em! But I won't go any bigger, I don't think. Then again, I buy stuff I don't need all the time just becuase it's a good deal, so who knows what parts I'll have on my garage floor a year from now!

    keithq
    Registered User
    Posts: 716
    (10/26/03 10:04 am)
    Reply 13" brakes.
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    I have 13" C4 brakes for my car.
    I am going to use the two peice rotors to get the weight down. I am also going to install some brake cooling ducts and I am thinking about a fluid circulation system. This allows the hot fluid in the caliper to move back to the master and lets new fluid into the caliper. It makes a big difference to how long it takes to boil the fluid. I am going to have to talk to someone about setting one up on my system

    Keith Quinn.


    andrewb70
    Registered User
    Posts: 1729
    (10/26/03 10:26 am)
    Reply
    Re: size
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    I wish I had some more imperical data avaliable for a before and after comparison. Here is what I do remember. Here is what the car looked like from 91-98, before I started the current build up:



    The car was setup with poly bushings all the way around. The front springs were 480lb/inch and the rears were 140lb/inch. I am actually still using the rear springs now. The sway bars were 1 3/8inch front and rear. The brakes were stock power disk/drum and the tires were BFG HR Radials, 265/50/15 on all four corners. The engine was an all iron, Pontiac 400 with a Muncie 4spd. I figure the front end weight was very similar to what it is now, with an iron headed BBC.

    With the above setup the car was a bit scary in panic stops. When the brakes were hit hard, all 4 tires would lock up. The front and rear biased was pretty good. I am not 100% sure what the cause was, but thats what it did.
    I think Dan's statement :
    Quote:
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    Larger diameter rotors are also less prone to lock up. A small rotor will be spiked into a lock up condition in a panic stop. A large rotor with more surface are will resist this pressure spike and slow more rapidly with as much tendacy to lock up.
    --------------------------------------------------------------------------------

    is very accurate.

    With the current setup I can get the brakes to lock up, but its a very subtle, easily modulated process. No doubt the fact that I have manual brakes contributes to the ability to modulate the brakes at the point of lock up. I am also sure that my current Nitto rubber is WAY better then those old BFG tires. The xcross at RSE had a very short area for braking. I would come through the finish line at about 50 MPH. Many people came up to me and commented on how well the car looked during the braking. The weight transfered a little bit to the front and the brakes were just on the edge of lock up. I could hear just a hit of tire sqeel. When we were swapping the rear end, I noticed that my rear pads were almost gone! The car has 3000 miles on it, so you know the rear discs are working and contributing to stopping the car.

    So, do you need large rotors? In my opinion, the heavier the car, the large the rotor should be.

    Andrew
    Project GatTagO



    conekiller13
    Registered User
    Posts: 592
    (10/26/03 11:38 pm)
    Reply rotors
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    I think this has been one of My favorite discussions on this board thus far.............

    Anyway..........one of the reasons that F1 cars have such small brakes is because the rules don't allow them to run any bigger than than a 13" diameter wheel. Their brakes are also carbon so weight isn't really an issue for the rotors. It is for calipers............the Mclaren team runs it's calipers at the bottom of the rotor for lower cg. I think it's a little pointless to use F1 or CART as an example here though because those cars weigh less than 20001bs. LMP900 and GT and GTS cars and WRC should be the guiding light. I found it interesting on (I think it was) the StopTech site, their coment about low profile tires offering less braking stability and performance. To Me that seems completly ludicris as the stiff short side wall is exactly what make the tire more stable and keeps the footprint of the tire planted. They throw in the comment about F1 tires being high profile but again that's because that is what the rules dictate.

    For what it's worth Baer still says the cross-drilling is for visual impact only.......that You will never see temps. high enough on the street to need it. Although I like the cross-drilling My next set will most likley just be slotted.


    Andrew, I couldn't quite tell...........was there fuzzy dice in the early picture? I definatly prefer GTO V2.0
    My experiances going from stock disc/drum to the Baer set up are the same as Andrew's with Willwood. The amount of controll You gain is very satisfieying. (Damn I wish I could spell)

    The brake fluid circulators look like a cool idea, but I'm still looking for a distributor of the water cooled calipers that the WRC and Trans-Am cars use.

    I think all in all though, just making sure You have a well balanced brake system with all components working together is the most important. I would say that calipers are probly the easyist to screw up. People seem to throw miss-match piston bores together all the time and end up with a myriad of problems.


    Dan





    jeffandre
    Registered User
    Posts: 526
    (10/27/03 7:48 am)
    Reply Footprint Increases?
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    Dan,
    I am far from an expert on this subject, but thinking about the higher sidewall benefitting braking makes sense if you relate it to the higher sidewall helping off-the-line traction. I would guess that a higher sidewall (within reason) would tend to both widen and elongate the footprint under braking, thereby increasing the amount of rubber on the road for braking purposes. Of course the sidewall height also affects cornering and steering input greatly, so a balance must be had in order to compete successfully. I would guess that Andrew B. has found that balance, whether it be by luck or design, so cars similar to his weight distribution would be well off to follow his lead as a start, then experiment from there.

    Jeff

    protour2001
    Registered User
    Posts: 23
    (10/27/03 8:04 am)
    Reply this discussion
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    Yeah this has been a good(and civil!) thread. It all started with a question, I hope that was answered. I am thinking along the same lines as Jeff, straight line traction is lessened by a lower stiffer sidewall.

    So riddle me this, is there a point at which the benefits of larger discs are outweighed by the negatives? The wheels that are available now can handle even larger rotors(ever seen stock brakes behind 22's? ) The largest rotors I have yet seen are 15"(on super heavy or racing vehicles only, sorry couldn't resist). Is that the limit? From my perspective, the benefit/drawback ratio seems to be even right around 13-14" for most people.

    There sure is a lot of (mis?)information about big brakes now, not like 10 years ago!

    One last question, everyone with the Wilwood setups, are you still happy with them? I just found a kit that is about half the price of what I thought I was gonna spend, and the shop is local.

    Brian

    Edited by: protour2001 at: 10/27/03 8:05 am

    andrewb70
    Registered User
    Posts: 1732
    (10/27/03 11:26 am)
    Reply
    Re: this discussion
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    I definitely think that my GTO v2.0 is way better. Back then I was working out of a little one car garage and a rather limited budget. The car actually handled very well.

    The subject of sidewalls is pretty interesting. My current rubber definitely has generous sidewalls. The tire diameter is about 27 inches in the front. So even with an 18 inch wheel, I have about 4 inches of sidewall in the front. I do suspect that this helps during breaking. Once again this is pure theory. It sure would be nice to be able to do some testing and confirm some of these theories.

    I am very happy with my Wilwoods. If Wilwood made a bigger caliper, I would have gotten it. I think with my heavy car, the bigger the better. Wilwood does make bigger calipers, but the problem is the avaliability of street pats for those calipers.

    Andrew
    Project GatTagO



    conekiller13
    Registered User
    Posts: 598
    (10/27/03 1:34 pm)
    Reply stuff
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    I see what You are saying about the sidwall flexing into a bigger foot print.......but it seems that the stiffer sidewall is more stable........back to the ease of modulation I suppose. The biggest rotors I have seen were 16" I forget on what, at some point gyroscopic effects are really going to add up also. So I would say at some point there would be too big. I know Toyo says that 24" is the biggest it feels is safe for a tire. THey have said that the amount of sidewall left to support a 6000lbs truck on 26" wheels is not an exceptable margin. As of a year ago when I still had contacts with Toyo they had no plans to do a tire bigger than that. I think BFG has a 26" tire but it may only be a matter of time before either company changes thier minds. Anyway.......a wheel of that size could carry a 22" rotor I think.....it would be intersting to see what effect all the other forces have.



    Dan

    gmachinz
    Unregistered User
    (10/27/03 3:22 pm)
    Reply some more thoughts...
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    On the subject of sidewalls, I tend to think that a tire with a generous or "forgiving" amount of sidewall actually makes the suspension work harder-at least when cornering. If you can visualize how if you were to enter a turn and slow down hard, your sidewalls tend to "roll on the outside edge" a little which makes the front suspension react by making the opposite side want to come up. So the outside edge of one is digging into the ground while the other front tire is digging into the ground on the inside part of the tire. The stiffer the sidewall, the less this action occurs. However, if the tires did not have a certain amount of "give" or deflection in regards to the sidewalls, then the shear inertia of the vehicle would cause the tires to more or less slide across the pavement instead of digging in. Both situations will cause the tires to start to break loose and the very first indication of this is a tire squeel. Then, easing off the brakes or accelerating out of it is one way to counter act it. Tire compound choice is the next issue. At what point does the tire compound, heat and pattern make the car handle better? High performance tires can tax a stock suspension more so than "standard radials" so likewise, a poor tire choice can make an otherwise great handling car act crazy-even with a properly designed suspension. I use Firestone Firehawk SE50's which have a rigid sidewall but the tread compound is a little softer so thay work well as a staightline tire or as a handling tire. Plus, the tread design comes pretty far up the sidewall so it gives up very little in the "corner carving" department. They were roughly $320-340 each retail. Basically, it all really does come down to tire choice to optimize handling characteristics-at least for me. -G

    teamsleep13
    Registered User
    Posts: 70
    (10/27/03 4:43 pm)
    Reply Rotor size
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    The heavier the car, the larger the rotor is wanter, in diameter, or thickness, mainly becasue the rotor is designed to do one thing, dissapate heat to allow kinetic engery to turn into heat.
    Rotors can be made from iron, steel, aluminum, titanium, carbon fiber, carbon ceramic, and some from pure ceramic material. All of these materials have different properties, and after choosing one thats riht for your application, then size can be determined.
    Out of the materials avaiable....iron, steel, titanium and carbon ceramic are the only ones that will work well on a street vechile. Carbon fiber wont work, it sucks when its cold, and during street driving, brakes are cold.

    Now, for the best performance, we want the lightest brakes possible that will give us the best performance. If you try and stop a 1 ton car and a 2 ton car with the same 11inch steel rotors, over and over, the 2 ton car will suffer due to brake overheating. Rotor size is realted to car weight, and braking endurance demands. The heavier the car and the more often its brakes are used hard, the thicker and larger the rotors will need to be.

    So heres my dilema, the car will weight 3000 lbs with driver and all fluids. 18" Speedline magnesium wheels are gonna be used, along with 14" carbon ceramic brakes, from a porsche gt2 with 6 piston monobloc calipers......so everything is great cept....its gonna get extremly hot....whos got brake fluid that takes 750F+? Thats all i need

    Hunter
    1968 F-117 Stealth Project
    1000 hp Aluminum Twin Turbo Small Block
    IFS & IRS, TCS, ABS, Adj. shocks, space frame chassis
    Revised Aero's
    Coming in 2005....

    gmachinz
    Unregistered User
    (10/27/03 7:07 pm)
    Reply 750F??????
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    Holy crap! I think we just entered another dimension. I use Valvoline synthetic DOT 4-I believe wet boiling point is 405F. It's enough for me, though. Um, yeah.....maybe it's time for a new thread..........

    protour2001
    Registered User
    Posts: 25
    (10/27/03 7:20 pm)
    Reply Re: 750F??????
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    What does Porsche spec for the ceramics? That should be good for your project. Where are you getting the brakes from, direct from Porsche? $$$

    andrewb70
    Registered User
    Posts: 1733
    (10/27/03 8:22 pm)
    Reply
    Re: 750F??????
    --------------------------------------------------------------------------------
    750 degrees? Your fluid will never get that hot.

    Andrew
    Project GatTagO



    Edited by: andrewb70 at: 10/27/03 8:35 pm

    teamsleep13
    Registered User
    Posts: 71
    (10/27/03 8:37 pm)
    Reply Re: 750F??????
    --------------------------------------------------------------------------------
    Buying them directly from Porsche, its like almost 5 grand a rotor. So I get them from a supplier who buys them off wrecked 911 Turbo's with that option, since it is the same brake system as the GT2 just offered as an option on the Turbo's. Bout 5 grand for 4 rotors.
    Spec's from Porsche dealers, they use 550 degree fluid. But this is not reccomended from Porsche if using the car for racing, as many GT2 owners are. A 600 degree racing fluid is reccomended. I have talked to two guys who own and race Turbo's with the ceramic brake option. They say that the 600 racing fluid works great. Also, the calipers will have a heat rejection coating on them, and the pistons will be titanium to help to keep everything cool.
    I guess I should have been more clear. I would love to find 750 degree brake fluid, but if it isnt out there, the 600 will be fine, I just like to have a margin of safety. Thanks

    Oh also, fluid recirculators, everytime you hit the brakes it circulates fresh, cooler fluid into the caliper.

    Hunter


    1968 F-117 Stealth Project
    1000 hp Aluminum Twin Turbo Small Block
    IFS & IRS, TCS, ABS, Adj. shocks, space frame chassis
    Revised Aero's
    Coming in 2005....

    Edited by: teamsleep13 at: 10/27/03 8:43 pm

    conekiller13
    Registered User
    Posts: 600
    (10/27/03 9:15 pm)
    Reply from rotors to fluid
    --------------------------------------------------------------------------------
    The best rated fluid out there is Castrol SRF racing fluid. It has a wet boiling point of 518 degrees F which higher than most other fluids dry boiling points. It is the highest rated fluid out there. Is what sold Me on it is stories of aluminum pistons actually deforming from heat and pressure with out the fluid boiling and loss of pedal feel. It is a bit pricey though at $80 a pint.



    Dan

    andrewb70
    Registered User
    Posts: 1734
    (10/28/03 7:02 am)
    Reply
    Re: from rotors to fluid
    --------------------------------------------------------------------------------
    When you spend 5K on rotors, whats 80 bucks on a pint of fluid?

    Andrew
    Project GatTagO


    walapus
    Registered User
    Posts: 77
    (10/28/03 8:39 pm)
    Reply to each his own
    --------------------------------------------------------------------------------
    I couldn't have fun driving a car with parts that expensive. Unless I didn't own it. We're in different realms....

    gmachinz
    Unregistered User
    (10/29/03 5:24 am)
    Reply 5K?
    --------------------------------------------------------------------------------
    Wow. At least if your rotors displayed any excessive runout problems, you could take 'em to O'reillys and have 'em turned for $12 each!


    conekiller13
    Registered User
    Posts: 604
    (10/29/03 5:54 pm)
    Reply rotors
    --------------------------------------------------------------------------------
    Not if they are corbon/ceramic. No machining on those rotors......of course they are not supposed to have run out issuse.




    Dan

    CarlC
    Registered User
    Posts: 75
    (10/30/03 10:15 pm)
    Reply Brakes
    --------------------------------------------------------------------------------
    I've had a bit of experience with three different rotor sizes, two different calipers, and multiple master cylinders with the same set of tires.

    I agree with conekiller, parts compatability is key for a properly working system. System is the key, one component that is out of whack with the others will send the car into a tailspin. Ask Craig Boone how much fun a 100 mph tailspin is.

    For a basic car, on the street, using a reasonably sized rotor on a well matched system the tires are going to be the primary factor in stopping distance. The best rotor on the planet won't significantly help a crusty pizza-cutter tire.

    A stock 11" early GM rotor and rear drum system is quite good for the money. With the right pad/shoe and an adjustable proportioning valve they can be made to stop, and hold up to reasonable heat, better than some aftermarket so-called "systems". I had this setup on the car with the same tires for one year.

    There are some aftermarket kits, not systems, that are not designed well. Many of the front kits are based on the GM 12" C4 rotor. This rotor has a larger diameter than the earlier 11" but is thinner. Depending on the company the rear caliper can be from a variety of makes and manufacturers. There are two major factors that now come into play: 1) The front-to-rear caliper clamping force ratios, and 2) the master cylinder-to-caliper compatibility. I can speak from firsthand knowledge that these two factors are not addressed well by some aftermarket companies. In other words, a well put together stock 11" front disk/rear drum "system" can work significantly better than a hyped-up 12"f/10"-11"r aftermarket "kit". Lots of different MC's and pads did not fix the underlying problems. I had one of these kits on the car for almost one year. The stock setup was better in almost every respect.

    The current brake system is basically a home-brewed setup based on stock GM and Ford components. 13" C4 front rotors and PBR calipers, 12" Z28 rear calipers, a Ford Cobra Mustang MC and hydraboost, adjustable proportioning valve, and Hawk HP+ pads. This setup has enough braking power and heat dissipation capability to handle 20+ minutes on a road coarse without fade. The car with 1/2 tank of gas knocks on the door of 3,600 lbs.

    If the car had more tire, hence allowing more braking capability, then fade might become an issue.

    The 13"/12" combo stops the car in a shorter distance than the other two. Why? For me this setup has the best balance, modulation, and pedal effort. The brake feel is significantly better and that goes a long way toward better stops. On non-ABS cars it's the drivers' brain-to-foot-to-pedal interaction that controls ultimate braking power. The smoother, and more controlable, that interaction is the better the car is going to stop. The stock setup had plenty of power but was more difficult to control. The closer to lock-up, the more difficult it became to control.

    Driving experience is also a huge factor. All the brake in the world won't do a bit of good without regular hard use and practice.

    As far as rotor weight goes, the inertia calcs are based on the square of the radius of the mass in question. In simplest terms, a two pound weight at a 13" radius (tire diameter) will have a 3.5x more effect on the inertia than a 2 pound weight at 7" (14" rotor diameter). Saving a few pounds in tire weight will go a lot farther than trying to pinch weight pennies on the rotors.

    Just my 2 cents.

    walapus
    Registered User
    Posts: 82
    (10/31/03 3:19 pm)
    Reply oversize rotors
    --------------------------------------------------------------------------------
    I agree. with almost all of that! My stock brakes work so well, I'm hesitant to change them. I wouldn't run them on race course for very long though. Tires are a HUGE factor.

    What follows a larger, heavier rotor? Even larger, substantially heavier wheels, unless once again you resort to incredibly deep pockets for ultra-lightweight wheels.

    A side note: A lot of people seem to look at the newest supercars for guidance. Remember, braking power depends not only on the mass of the vehicle, but also on the speed braking is initiated at (in fact, much more so). New corvettes and porsches need reliable braking from 170 mph. Hence 13" rotors. Does that mean you 14" rotors to slow from 60 mph, even while autocrossing? I doubt it

    A corvette (3000lb) at 170 mph has 3.9MJ to dissipate.
    A 3800lb car at 60 mph has 1/6 that. Plus, at 170 mph, stability obviously becomes a PRIME issue. I think, FOR A STREET CAR of 20+ years age, returns are fast diminishing beyond 12" or so, even in terms of feel. It would take a very impressive argument to convince me that 14 or 15" rotors are worth anything besides bragging rights

    I'll be the first to report how much improvement I get when i go from my stock disc/drum to LS1front/lt1. I honestly do not expect a huge gain in ultimate one-stop performance, but like Carl I recognize that driver confidence, feel, and balance really guide what you are are able to do with your car, and I think this setup will be near perfect for my 3400ish lb nova. I think my gains will be in large part to much improved calipers and the increased fade resistance of the overall system.

    I intend to do before/after measurements, maybe even in phases to show stock, stock front/lt1 rear, stock rear ls1 front, and ls1/lt1. Measurements won't be taken until after I feel each system is properly set up (correct M/C, adj prop valve if necessary). I don't know if I should tweak with an adj prop valve in the stock system or not. On one hand, it will no longer be "stock", but on the other hand if an adj prop valve can really make a gain even on the stock, I'd like to know.
    I'll let you know what I find.

    gmachinz
    Unregistered User
    (10/31/03 5:12 pm)
    Reply here's what will settle it...
    --------------------------------------------------------------------------------
    I say we get as many people on this board to gather for a "club show" and demonstrate our own 0-100-0 shootout, dragrace event and roadcourse slaloms. That would kick @$$!!

    conekiller13
    Registered User
    Posts: 608
    (10/31/03 6:40 pm)
    Reply YEA
    --------------------------------------------------------------------------------
    If it's on the west coast and I ever get My car back together, I am soooooo there.

    Dan

    walapus
    Registered User
    Posts: 83
    (10/31/03 8:31 pm)
    Reply group event
    --------------------------------------------------------------------------------
    That would be awesome. I would love it if for nothing more than to just see all these awesome creations I've been reading about. I wish I knew of a good track around here, since our shop is on the central coast, almost exactly between LA and SF. We used to be able to do stuff at the airport, but that got shut down....

    parsonsj
    Registered User
    Posts: 1257
    (10/31/03 8:36 pm)
    Reply Not a "club show"
    --------------------------------------------------------------------------------
    Not a club show. You mean a Pro Touring convention! Complete with track time, skid pad and braking measurements, vendor participation and consulting, plus magazine guys walking around being constantly bugged. Maybe even a dragstrip for grins.

    Hold them annually, starting wherever can get the biggest turnout, then move them around the country in subsequent years.

    What fun that will be!

    John Parsons


    gmachinz
    Unregistered User
    (11/1/03 8:25 am)
    Reply "Pro-Tour" coming to a city near you...
    --------------------------------------------------------------------------------
    That kinda has a cool ring to it! We could drive across the U.S. and people (pro-tourers) can join in wherever it comes the closest to them at. Maybe have an award for the longest distance travelled? How about having it coincide with a larger venue like the Hot Rod power tour (just as an example) and we could organize our own "track times" in various cities! Just think of all the magazine coverage pro-touring would get! Not to mention the marketing possibilities for Larry! Hell, I bet we could get a staff writer from a major mag. to ride along for a week or so to get to know everybody and their cars! Maybe each day on the "Tour" that writer could cruise in somebody else's car for the day. Craziness but I bet it could happen!

    jon sikora
    Registered User
    Posts: 538
    (11/1/03 9:20 am)
    Reply the event already exists
    --------------------------------------------------------------------------------
    thunderhill raceway,willows california,nov.22-3.all the track time you can stand,plus use of the skid pad and a mesured braking area.a chance to get real numbers.the events already exist,the problem is getting anyone to participate.i've done 5 track days,2 open road races and 1 superspeedway event so far this year.if my 'trashy ghetto beater' can do it,surely there must be a couple other cars that can turn out for the occasional event.back to the original ?,my truck has a 10,000 # gvwr,comes in at 6300+# unladen,and has 11.75 1.25 rotors,drum rear.it stops vey well indeed.balancing front to rear caliper bores and choosing the correct mc is more important than rotor size.i've had 5 rotors,5 calipers and 7 masters on mine.i've become a real fan of speed bleeders.are people installing big brakes for the look?well, yes.but i bought my whole car for the look,so what does that matter?i think we can all agree that you don't need 13" rotors to roll the car around the garage.get it on the road,you can upgrade the brakes later.

    CarlC
    Registered User
    Posts: 79
    (11/6/03 11:38 am)
    Reply Track day
    --------------------------------------------------------------------------------
    Hotchkis Track Day. May 9, 2004 at Buttonwillow Raceway Park. Anyone interested?

    jon sikora
    Registered User
    Posts: 539
    (11/7/03 8:53 am)
    Reply hell out there
    --------------------------------------------------------------------------------
    suddenly very quiet in here.how about a little friendly competition?maybe the fastest lap time of the day should be presented with,and forced to take home,a truly ugly trophy.perhaps a ceramic nekkid lady with a clock in her belly,or something like that.

    walapus
    Registered User
    Posts: 89
    (11/7/03 3:18 pm)
    Reply excellent....
    --------------------------------------------------------------------------------
    How about a gold plated 1/18 scale yugo?

    gmachinz
    Unregistered User
    (11/7/03 4:53 pm)
    Reply how about.....?
    --------------------------------------------------------------------------------
    How about making the loser (last place finisher) drive around for the rest of the event with an inflatable woman riding shotgun? I had to tote one around all over town for my bachelor party a few years back! I went in with the guys to (of all places) a strip club and I actually had a hard time (please, no puns! ) keeping everyone in the bar from stealing "my girl"!!

    keithq
    Registered User
    Posts: 724
    (11/7/03 7:56 pm)
    Reply Ceramic rotors.
    --------------------------------------------------------------------------------
    Hey Guys.

    Just a note on the ceramic rotors.
    My cousin has a 2002 C4S, when he was at the dealer getting a service he talked with a guy who had a turbo and went to the track once, drove the car hard and had brake problems. He bought it to the dealer, they installed new rotors and handed him a bill for about $7000.00. The guy said lots of others have had the same complaint. My cousin checked some of the Porsche sites he goes to and sure enough there were other complaints on there too.
    Looks like the newest and best is not always so.

    Keith Quinn.


    CarlC
    Registered User
    Posts: 86
    (11/8/03 4:04 pm)
    Reply Nekked ladies....
    --------------------------------------------------------------------------------
    Jon,

    OK, that's it. I'm now officially on the yard sale hunt for just such a trophy! Maybe Larry will pony up a sticker to put across her, uh, um, private areas

    I can just imagine trying to explain it to my wife....



    I have a lot of work to do before May 9. Any takers?

    protour2001
    Registered User
    Posts: 31
    (11/9/03 9:06 am)
    Reply Track days.
    --------------------------------------------------------------------------------
    Jon Sikora, I have a question for you under "hardcore brake discussion" . Thanks!

    I like the idea of getting together for some OT time and testing, somewhere in California probably. My car will be running come spring time, I'd like to test it some before the real mods begin!

    pdq67
    Registered User
    Posts: 194
    (11/21/03 10:09 pm)
    Reply xx
    --------------------------------------------------------------------------------
    Gee whiz guy's!

    This is way outta the "pdqCBB" setup league, but I kept reading anyway.

    Thanks for all the good info.

    pdq67

    davidpozzi
    Moderator
    Posts: 950
    (11/23/03 9:17 pm)
    Reply
    Re: xx
    --------------------------------------------------------------------------------
    I'd like to add that a larger dia rotor with better leverage ratio over the tire will reduce pedal effort and brake line pressure required to stop the car. This lower pressure requirement will show up (hopefully) in less deflection of the caliper and all the other brake system components including the brake pedal and even the firewall on manual systems! Lower deflection should show up as an easier to modulate braking system making wheel lockup easier to avoid.

    An increase of vehicle weight or increase of tire traction will increase the load on the brakes. Horsepower increases will add a lot to the brake heat on a road course.
    67 RS Camaro, 69 Camaro vint racer, 65 Lola T-70 Can-Am vint racer.
    http://ourworld.compuserve.com/homepages/David_Pozzi/

    chicane
    Unregistered User
    (12/1/03 9:03 pm)
    Reply Pro-Touring day.........
    --------------------------------------------------------------------------------
    Great point David.

    Hey why dont we have a Pro-Touring meet here in Vegas? We can rent the LVMS big track and use the drag strip, a road course, a skid pad and a nice long slalom.......and just make a weekend out of it.

    andrewb70
    Registered User
    Posts: 1948
    (12/1/03 9:24 pm)
    Reply
    Re: Pro-Touring day.........
    --------------------------------------------------------------------------------
    With any luck I will be living 2 hours from Vegas in the next few months. Sounds good to me!

    Andrew
    Project GatTagO

    jeffandre
    Registered User
    Posts: 561
    (12/1/03 10:47 pm)
    Reply Silver State?
    --------------------------------------------------------------------------------
    Andrew,
    Any designs on running the Silver State with the goat?

    Jeff

    andrewb70
    Registered User
    Posts: 1958
    (12/2/03 7:13 am)
    Reply
    Re: Silver State?
    --------------------------------------------------------------------------------
    Maybe...someday...not anytime soon.

    I have way too much on my plate at the moment.

    Andrew
    Project GatTagO

    parsonsj
    Registered User
    Posts: 1306
    (12/2/03 9:09 am)
    Reply Too quiet
    --------------------------------------------------------------------------------
    I'm quiet about all that for two reasons: I'm thousands of miles away here in Maryland, and my car isn't done. But I will be there somehow, eventually.

    jp


    d touring
    Registered User
    Posts: 717
    (12/3/03 4:15 pm)
    Reply Re: Too quiet
    --------------------------------------------------------------------------------
    I would love to get in on this !!! Sounds like fun times to me
    But i will have to get the car done an move first!!!
    David 69 pro-tour camaro