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Purple_Beasty
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May 2002
icon5.gif  Should I get cross drilled rotors? Thu, 05 June 2003 07:43 Go to next message

To Crossdrill or not?[ 1 vote(s) ]
1.Yes 0 / 0%
2.No 1 / 100%

Just want a few opinions on what to do with the brakes on my car.
I have a 1964 Rambler American 2 door that is currently being converted to a 4 wheel disc brake setup from an XF Falcon.
Here is the question, I will be getting new rotors all round and need to decide between slotted (NZ$160 per disc) or slotted and cross drilled (NZ$200 per disc).
I know that there is no benefit in braking for a street car from cross drilling, but if it was your car would you spend the extra just for looks?

Here is a picture of the car and the wheels the brakes will be behind.

http://pic4.picturetrail.com/VOL54/962550/1804736/21395788.jpg

Callum

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Cool1
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I supported Toymods
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Re: Should I get cross drilled rotors? Thu, 05 June 2003 08:01 Go to previous messageGo to next message
That poll is farked Confused
Dont bother about the cross drilling, it doesnt look that good!
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manipulate
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Re: Should I get cross drilled rotors? Thu, 05 June 2003 08:03 Go to previous messageGo to next message
Dont bother for looks

also with cross-drilling if your not using the advantage of quick heat dissipation its pointless as theres less surface area contact with the pad right ?

Ta
Mani
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route__666
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Re: Should I get cross drilled rotors? Thu, 05 June 2003 08:52 Go to previous messageGo to next message
dont bother with cross drills because you can not get the machined if they ever need it
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Classique71
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Re: Should I get cross drilled rotors? Thu, 05 June 2003 09:01 Go to previous messageGo to next message
Just Slot the Rotors and put in a decent set of pads + good brake fluid.. Checking the likes of your brake lines + master cylinder would be worth it too if you want to reco the whole system to " new "

Cross Drills are Wank , unless your racing the car or want rice boys to NVY U - they are a waste of money
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Blown86
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Re: Should I get cross drilled rotors? Thu, 05 June 2003 09:35 Go to previous messageGo to next message
manipulate wrote on Thu, 05 June 2003 16:03

Dont bother for looks

also with cross-drilling if your not using the advantage of quick heat dissipation its pointless as theres less surface area contact with the pad right ?

Ta
Mani


Nope, cross-drilling doesn't affect performance.

There's no point to cross-drilling on the road, they crack easily and can be quite noisy.
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manipulate
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Re: Should I get cross drilled rotors? Thu, 05 June 2003 09:37 Go to previous messageGo to next message
Blown86 wrote on Thu, 05 June 2003 19:35

manipulate wrote on Thu, 05 June 2003 16:03

Dont bother for looks

also with cross-drilling if your not using the advantage of quick heat dissipation its pointless as theres less surface area contact with the pad right ?

Ta
Mani


Nope, cross-drilling doesn't affect performance.

There's no point to cross-drilling on the road, they crack easily and can be quite noisy.


but if theres less surface area to touch the pad ???
....(obviously assuming its the same size )
hmm...
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Blown86
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Re: Should I get cross drilled rotors? Thu, 05 June 2003 09:51 Go to previous messageGo to next message
Braking effort is only determined by clamping force and the coefficient of friction of the pads and disc.
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Norbie
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Re: Should I get cross drilled rotors? Thu, 05 June 2003 10:24 Go to previous messageGo to next message
The purpose of cross-drilling is to prevent a layer of gas forming between the pad and the rotor when the brakes get extremely hot. Obviously if your pad is floating on a layer of gas that will have an effect on the coefficient of friction!

Having said that, this isn't an issue for a road car - it's strictly for the track, or the poser set.
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M.J.H
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Re: Should I get cross drilled rotors? Fri, 06 June 2003 01:53 Go to previous messageGo to next message
Norbie wrote on Thu, 05 June 2003 20:24

this isn't an issue for a road car - it's strictly for the track, or the poser set.



I disagree as the brakes on the AU2 where getting to hot and not stopping as well as they should until the drilled and slotted rotors where fitted,now it just needs a light touch on the pedal to stop as it should.
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fingers
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Re: Should I get cross drilled rotors? Fri, 06 June 2003 02:12 Go to previous messageGo to next message
I always thought that track cars get the most benefit from rotors that were just slotted? The theory being that cross-drilled rotors have less metal to absorb the heat and then crack more easily after being abused?

As for the original question, whether or not to get the rotors cross-drilled or not, I reckon save the $40 per disc and just get the slotted.
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Purple_Beasty
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Re: Should I get cross drilled rotors? Fri, 06 June 2003 07:07 Go to previous messageGo to next message
Classique71 wrote on Thu, 05 June 2003 21:01

Just Slot the Rotors and put in a decent set of pads + good brake fluid.. Checking the likes of your brake lines + master cylinder would be worth it too if you want to reco the whole system to " new "


Actually getting the COMPLETE XF Falcon set up put in with Falcon front supsensions arms, balljoints etc modified to fit, recoed XF master cylinder, Falcon LSD diff narrowed to suit and new lines where required with BRAND NEW DBA rotors. Original set up was four wheel drums and it is currently running 40mm Shocked Shocked spacers to fit the current wheels. The car is actually a very rare factory right hand drive 1964 Rambler American 2 door.

Callum
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toycelica77
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Re: Should I get cross drilled rotors? Fri, 06 June 2003 07:20 Go to previous messageGo to next message
Blown86 wrote on Thu, 05 June 2003 19:51

Braking effort is only determined by clamping force and the coefficient of friction of the pads and disc.


what about rotor size?

apart from bigger surface area, the length of the braking arc is increased therefore allowing for greater breaking force to be applied...

are you saying small rotors with the same braking area as fuckin huge rotors will brake the same? if this is the case, why do bikes have huge rotors? and not small rotors with calipers rated at the same clamping force?

in response to the orginal topic - cross drilling on street car is kinda pointless, unless your going for 'show-factor'
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crazy_camry
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Re: Should I get cross drilled rotors? Fri, 06 June 2003 11:17 Go to previous messageGo to next message
have a look at this discussion for more opinions:
http://www.toyotanation.com/showthread.php?s=& threadid=6862
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Blown86
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Re: Should I get cross drilled rotors? Sat, 07 June 2003 09:43 Go to previous messageGo to next message
toycelica77 wrote on Fri, 06 June 2003 15:20

Blown86 wrote on Thu, 05 June 2003 19:51

Braking effort is only determined by clamping force and the coefficient of friction of the pads and disc.


what about rotor size?

apart from bigger surface area, the length of the braking arc is increased therefore allowing for greater breaking force to be applied...

are you saying small rotors with the same braking area as fuckin huge rotors will brake the same? if this is the case, why do bikes have huge rotors? and not small rotors with calipers rated at the same clamping force?

in response to the orginal topic - cross drilling on street car is kinda pointless, unless your going for 'show-factor'



Making rotors larger just increases the mass of metal able to be used as a heat sink. Breaking force remains the same but maximum braking force can be maintained for longer before the brake temperature exceeds the maximum operating temperature of the system.

Bikes have large diameter but very thin rotors to maximise the heat sink available for the least weight, possibly for looks and brake lever feel as well.

Cross drilling does not really provide cooling improvements as some manufacturers like to claim. It only really reduces mass and therefore unsprung weight and helps remove the pad boundary layer. From tests I've done in the past on open wheeler race cars, the only advantage was that cross drilled dics cool down faster when the car is stationary.
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trent_kershaw
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Re: Should I get cross drilled rotors? Sat, 07 June 2003 11:45 Go to previous messageGo to next message
1) Go and spin a bike wheel. Stop it with your hand near the axle.

2) Spin it again. Stop it with your hand near the outer rim.

Which of these required less effort from you?

Physics suggests that 2 requires less.

Same should apply with large and small brake rotors.
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ed_ma61
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Re: Should I get cross drilled rotors? Sat, 07 June 2003 13:14 Go to previous messageGo to next message
Blown86 wrote on Sat, 07 June 2003 19:43

Making rotors larger just increases the mass of metal able to be used as a heat sink. Breaking force remains the same but maximum braking force can be maintained for longer before the brake temperature exceeds the maximum operating temperature of the system.

Bikes have large diameter but very thin rotors to maximise the heat sink available for the least weight, possibly for looks and brake lever feel as well.


WTF!!!

oh dear god... go read an elementary physics book, speciiclly the chapter titled "torque"

i am astounded you can state all of the above with a straight face. please dont continue to spread misinformation...

and fwiw: bikes weigh oh, i dunno, 15% the mass of a car?? they only have x amount of kinetic energy to scrub off, and thus dont need 32mm thick rotors to act as heat sinks.

lever feel is SOLEY a mechanism of slave/master ratio, lever design, hose flexibility, and caliper flex.

i didnt want to get into explaining this, but i guess i should...braking force is governed ONLY by pad frictional force (which is influenced by piston force, and pad compund only - NOT surface area), and rotor diameter. other factors like pad surface area, rotor slotting and drilling, rotor width etc are to do with heat and gas control.

obviously then, the two best things to upgrade are pad compund, and rotor diameter. dia is NOT a heat thing... yeash!
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toycelica77
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Re: Should I get cross drilled rotors? Sat, 07 June 2003 23:52 Go to previous messageGo to next message
haha blown86 - j00 GoT OwNeD!

ed - with cross drilling i also heard is a way to keep water off the pads as it takes a small scraping off the pad when the holes passes over the pad face, is this true?

[Updated on: Sat, 07 June 2003 23:52]

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ed_ma61
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Re: Should I get cross drilled rotors? Sun, 08 June 2003 03:26 Go to previous messageGo to next message
toycelica77 wrote on Sun, 08 June 2003 09:52

with cross drilling i also heard is a way to keep water off the pads as it takes a small scraping off the pad when the holes passes over the pad face, is this true?


slotting pretty does this - scrapes a layer of glaze off the pads. they let water shed, and give a port for gas escape.

holes reduce rotaional mass. they also increase surface area for the rotor for heat exchange (much like finned rotors).

holes are just silly ideas for a road car. they create stress risers in the material, and can promote cracks. this isnt a problem for race cars as they replace their rotors ultra regularly. how often does joe avergae change (or even check) his rotors.

ed
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SUPRAGTE
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Re: Should I get cross drilled rotors? Sun, 08 June 2003 12:24 Go to previous message
Yeah, you'll notice none of the V8Supercars run cross-drilled rotors either as they had major problems with the discs cracking and disintegrating.

Just slot them.
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