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MotorGround >> Upgrade brakes?


7/13/08 6:53 PM
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Frills
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I've got a new set of wheels and tires ordered and should arrive next week.

I was wondering if I should go ahead and upgrade the brake rotors, pads, and lines at the same?

If I only upgraded the front brakes and left the rear stock do you think it would screw anything up?

8600 miles + 2 track days = new tires, but well worth it.
7/14/08 1:11 AM
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Frills
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the rotor + caliper packages basically start around 5k, which is well out of the current price range.

Do you think just upgrading the front will unbalance the car in the corners? I don't think it would unless I did calipers and the whole package, but since it wouldn't be a full upgrade I imagine it will be alright. I just don't want to screw it up

Being a mid engined car kinda worried that the extra stopping power on the front end will increase the likelyhood of being passed by the ass end in a corner.
7/14/08 10:33 PM
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stevekt
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I would do front and rear at the same time. Don't know why, but I'm assuming these big brake upgrades are designed to work as a complete kit.
7/14/08 11:11 PM
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stevekt
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 Here's a letter I scanned from Sport Compact:

MORE STOPPING OR MORE GOING?

Question:
I have a base 350Z and I've been wanting to upgrade the brakes as my first modification. Since I read Sport Compact Car, not sport Luxury Car, you can probably guess I'm on a budget. The planned set-up is a 13-inch, four-piston front with StopTechs and Racing Brake's 13-inch OE upgrade for the back.

The only problem is that the rears will still be the stock sliding calipers instead of a fixed, opposed-piston set-up like the front. Would this numb the feel on the front brakes because I didn't change the rear calipers?

My driving skill is good enough to feel and understand a vehicle's dynamics. I go to at least four HPDE events a year and do a lot of spirited driving. The guys I run with all say I should go opposed-piston all around, but they can afford cars that come with good brakes stock.

I guess I could try the Racing Brake upgrade and if I don't like it, eBay it. But skipping it altogether would save about $1,500 for that Quaife ATB differential I'm considering. I think I just answered my own question ... but I would still appreciate your input. Oh, and don't tell people to cut their springs, seriously.

Frank Monserrate Alameda, CA


Answer:

You should be very cautious mixing unrelated brake kits. Odds are good that not only will braking performance be hurt by your arbitrary rear upgrade, but the opposed-piston rear calipers might even make pedal feel worse.

First, braking performance. A properly engineered brake kit like Stop Tech's will be tuned to provide the correct brake bias. Most factory systems are a little too front-biased for maximum stopping power. In spite of their larger size, the frant brakes in a Stop Tech Z kit actually exert less brake torque for a given line pressure than the stock brakes. This forces the rears to work proportionally harder and should get all four tires to the point of lock-up (or to the ABS threshold) at the same time.

Advantages of a big brake kit come not from increased brake torque, but from maximizing the stopping potential of the tires through brake bias optimization, improved modulation through more rigid calipers, and from better consistency through improved heat capacity and cooling.

Trusting that Stop Tech did its homework right on brake bias (and there are few companies who get gold stars on their papers more consistently), fitting bigger brakes on the rear is probably going to throw that bias off. While the exact brake torque available from a given brake kit is hard to calculate, it's reasonably easy to guess which way things will go when parts are changed.

Torque is a force times the lever arm it's applied with. When tightening a bolt, yanking on the end of a one-foot wrench with 50 pounds of grunt will get 50 ft-Ibs. Same goes for brakes. The force is a function of the surface area and coefficient of friction of the pads, how hard they're clamped against the rotor, and how fast the rotor is moving. The lever arm is simply how far the caliper is from center of the rotor.

With the Racing Brake 13-inch OE upgrade, the OE calipers are used with larger-diameter rotors (this is made possible by Racing Brake's clever caliper bracket that re-aligns the factory caliper with its larger rotor). On the force side of the torque equation, the surface of a larger rotor will slide past the pads a little faster, slightly increasing the force applied by the pads. On the lever arm side, the caliper is further from the center of the rotor, so the arm is longer. More force times a longer lever arm equals more rear brake torque. To maintain proper brake balance, this stronger rear brake should only be used with a stronger front brake.

Does ABS sort things out? To a point, yes, but ABS doesn't simply watch wheel speed and react, it's programmed with some basic assumptions to speed up reaction times. Deviate too far from the line-pressure-versus-torque relationship it's expecting and ABS performance-and stopping distances-will suffer. 

There's also the small matter of what happens before ABS intervenes. Imagine trail-braking into a corner with rear-biased brakes. Each tire only has a limited amount of grip-if that's used up with braking, there's less for cornering. Even before lock-up, heavily rear-biased brakes will tend to cause brake-induced oversteer. Have fun with that.

On the issue of pedal feel, it's important to realize that the rear brakes don't clamp nearly as hard as the fronts, therefore don't flex nearly as much. There is relatively little pedal feel to be gained in the rear. On the other hand, a Quaife will make a huge difference on the track and, as you guessed, will be a much more effective use of funds.
 

7/15/08 8:40 PM
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Atecexa
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what kind of car is this going on?
7/16/08 10:42 AM
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Frills
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Edited: 07/16/08 10:42 AM
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2007 Lotus Elise 
7/16/08 12:32 PM
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Ponyboy
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If you've done track days and the rear brakes did not catch on fire, you should be okay.
7/16/08 8:21 PM
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stevekt
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[quote]Frills -   2007 Lotus Elise [/quote] 

Nice color.  Looks similar to my Mazda.  Got any closer shots?

7/24/08 11:25 AM
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Atecexa
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"2007 Lotus Elise"

what are the goals of the upgrade? shorter stops from 60? from 100? less fade? longer wear? is this a street car or track only?

A lot of issues could possibly be solved with stickier tires or something like an EBC Red or Yellow pad which would require warm up so not the best thing for a street car. Instead of going bigger rotors try better rotors, check into anyone making a ceramic composite brak rotor for the car similar to what some of the newer 911's come with. when upgrading brakes the size of the rotor and the layout of the caliper are not usually the bottlenecks

what are you really trying to accomplish?
12/20/08 4:11 AM
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Frills
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12/20/08 5:57 AM
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walbjj
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as mentioned, what is ur end goal?
u mention track days. how often? do u run street tyres for everyday use and semi slicks for the track?
do u suffer from braking issues at the track? fade? have the rotors warped or cracked?

my brother ran an evolution 9 and he tracked it regularly. it has brembos as stock and his first track day, it faded badly. so he upgraded to goodrigde braided brake lines, higher temp brake fluid, changed his pads to a more street/ track orientated one (at the expense of squeal on the street) and he didnt suffer anymore fade at the track.
the next step for him would have been changing rotors to slotted and possible a different material, but his current rotor was still ok.
the final stage would have been a bbk, but that would be too much for the power he had.
running a lotus, power isnt the issue. i would look more at ur tyre, suspension and the initial brake upgrades rather than outlaying a chunk of change on a bbk. the bang for buck wont be there, especially for a light car

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