Region: WDC
Car #: #23
Year : 1991 Posts: 642
Status: Offline
posted
Time to R&R the brake system.
Over the last season I've heard the following three setup recommendations from various racers:
#1 - I don't use any of the hardware, clips or springs and it all works fine. Criticism - Potential for door stopping. Excess friction/drag by not using the springs.
#2 - I use the clips but don't use the springs. Criticism - Excess friction/drag by not using the springs.
#3 - I use all of the hardware, clips & springs. Criticism - Greater chance of pad knock back especially after bumpy exit curbing.
For the last two seasons I used the clips only and have never experienced pad knock back. Others who have used the springs have had knock back. I have experienced greater rotor checking than others which has been blamed on not using the springs.
Personally, if I have to choose between changing rotors more often and ending up in a tirewall at the end of a long straight, I would choose the former.
Experts - Which setup is the correct one and what are the downsides, if any?
-------------------- Muda Motorsports "We're all here 'cause we're not all there."
Knockback is contributed to by slider friction (both pin and hardware, under load), piston friction (under load), wheel bearing play (at speed, at temperature, under load), pad thickness, pad taper. Whether that entire equation is affected by the Whataburger springs or not is impossible to be predicted, even by SM.Com website luminaries with many trophy icons and long signature lines filled with sponsors.
Light dragging (or not) based on not running the springs (or not not running the springs) will not contribute to heat checking.
Some pad backing plates are a little oversized for the hardware (esp PFCs).
Thin or tapered pads allows a vibration to "hammer" the piston back in situations where full thickness pads prevent this. Rotating pads to minimize taper is a good practice that most SMers do not do. This also helps minimize deposits on the rotors if you are having that problem.
Heat checking has more to do with the track and the pads being used, rotor mass, age, and usage history, followed possibly by the rotor quality and whether the calipers are returning well. Heat checking is a thermal fatigue mechanism (a function of "heat cycles" not a one-time extreme temperature experience). Do not confuse normal heat checking with a bona fide "crack". Uniform hairline cracks less than an inch long are "checks" and generally normal if you are running a pad that allows long rotor life (e.g. Carbotechs) but a crack that stands out on its own, is longer than 1" or longer than all others and you can catch a thumbnail in it, requires immediate replacement.
If you run the clips, note that they become dimpled where the pad backing plate hammers into it every time you hit the brakes (when the pads hit the rotor, the rotor rotates the pad "downward", eh?). Rotate the clips top to bottom once the bottom ones become dimpled. Otherwise, you just have one more obstacle between your foot and perfect modulation.
If you don't run the clips, pay attention to where the pad hammers into the caliper casting every time you hit the brakes. You could file it smooth(er). You could lightly grease it. Does it slide freely when you run the pad through its motion? Will it do so with 100 ft-lbs of torque being resisted at that point where the backing plate hits the caliper casting? Would it be better to have as much contact area there or as little?
Do all this and someone will still pass you under braking. Do none of this and you will still pass someone else under braking.
-------------------- Visit the Midland City Arts Festival!
Region: NER
Car #: 7
Year : 1999 Posts: 636
Status: Offline
posted
John,
I went through 2 sets of rotors and 3-4 sets of Hawk Blues last season using the stock hardware, clips and all. I pitch my pads when they're about half worn. One of the rear caliper pins began to back out regularly and was loose after a weekend in Sep, so I'm replacing the caliper carrier assuming the hole/threads are toast.
I pull my brakes after every race weekend and wire brush the pad sliders, re-lube the pins and check for any abnormalities. Haven't had any problems so far.
Got some pad knockback after hitting the turtles at Lime Rock but it's not a regular occurance.
[ 11-29-2009, 08:44 PM: Message edited by: CP ]
-------------------- -Cy Supported by LTD Racing & Speed Shack - New England's Premier Auto Accessory Store Rt1 AutoMile - Norwood, MA http://www.speedshackonline.com
Region: Waterford Hills
Car #: 38
Year : 96 Posts: 348
Status: Offline
posted
I like using the clips. It gives the pads a nice smooth surface to ride on instead of the casting. I also file the pads where they contact the clips so it is free of any paint and burrs. I make sure everything moves with ease. I do replace the clips with a pad change, They are cheap.
I leave out the springs.
-------------------- Ralph Provitz #38 2008 WHRRI SM Champion 2008 WHRRI Top 10 Overall V2 Motorsports, Race support, Data Dude
Region: NER
Car #: 7
Year : 1999 Posts: 636
Status: Offline
posted
Clips, springs...wtf are you guys talking about?
I've got some U-shaped things that go into the holes on the front pad-backs that hold them apart. Then there are come W-shaped things that go between the rear pads that keep them apart. Are we on the same page here?
I don't have any springs in my brakes.
-------------------- -Cy Supported by LTD Racing & Speed Shack - New England's Premier Auto Accessory Store Rt1 AutoMile - Norwood, MA http://www.speedshackonline.com
Region: SFR
Car #: 88 SM
Year : 99 Posts: 367
Status: Offline
posted
Assuming your in SM. Is this subject moot, with the Dec. fastrack? "No components may be added or omitted from those specified by the published factory service procedures." J~
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