911 Brakes 3" vs 3.5", What am I missing and |
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911 Brakes 3" vs 3.5", What am I missing and |
jesiv |
Aug 26 2008, 01:41 AM
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#1
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Senior Member Group: Members Posts: 552 Joined: 5-August 07 From: Pensacola/Milton, Florida Member No.: 7,975 Region Association: Northern California |
Ok so I am upgrading to a 911 suspension (Seperate Thread http://www.914world.com/bbs2/index.php?showtopic=87337 ). Then I hear brake caliper bolt spacing 3.5 vs 3.0. So (IMG:style_emoticons/default/WTF.gif) WTF is 3" vs 3.5" Am I making a mistake going with 3.0 vs 3.5? I really don’t understand the issues. Do I care?
Thanks for real world opinions! Regards, James |
McMark |
Aug 26 2008, 02:26 AM
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#2
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
It depends on what you want to do with the car. What kind of motor you're putting in etc.
Basically, more stress (big motor, track time, etc) means more brakes. 3" = 'low' and 'medium' brakes 3.5" = 'medium' and 'high' brakes |
ArtechnikA |
Aug 26 2008, 05:52 AM
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#3
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
3" = 'low' and 'medium' brakes 3.5" = 'medium' and 'high' brakes To expand a bit, in case you were wondering where the 'M' and 'S' brake classifications came from, they are Ate (Itself an abbreviation for Alfred Teves) designations for the size of the caliper. Mitte - middle/medium duty Schwer - heavy duty There are good brakes to be had in both sizes. a /4 on 'normal' street tires can lock 'em up repeatedly with stock calipers, which is -probably- all the brake you need. The small caliper and unvented disk/hub assembly is quite light which contributes to the 914's nimble feel and good road-holding. For more power and increased fade resistance (i.e. V8 or trackday) the vented rotor has its benefits. 911 'M' calipers are plentiful and cheap. It's what 914/6's came with up front. Be aware that /6's also came with bigger pistons in the -rear- brakes, so if you go increasing front caliper size, you're tinkering with the front/back brake bias as well as approaching the hydraulic limits of the 17mm 914.4 master cylinder. This is all manageable, but it is additional stuff to think about. You -can- put truck brakes on a 914 - after all, the 935 brakes were basically a standard heavy truck brake Ate was asked to make in aluminum rather than the truck's cast iron... But your car won't stop any faster. And all this presumes you are going 4-lug, 'cause AFAIK, there are no 4-bolt 3.5" bolt spacing struts. (BTW - that's a real 3.0" and 3.5" measurement, one of 4 or 5 English unit parts that are international standards. Another thread for those...) |
Richard Casto |
Aug 26 2008, 08:39 AM
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#4
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Blue Sky Motorsports, LLC Group: Members Posts: 1,465 Joined: 2-August 05 From: Durham, NC Member No.: 4,523 Region Association: South East States |
To expand a bit, in case you were wondering where the 'M' and 'S' brake classifications came from, they are Ate (Itself an abbreviation for Alfred Teves) designations for the size of the caliper. Mitte - middle/medium duty Schwer - heavy duty With both "S" (aluminum) and "A" (steel) front calipers being 3.5" is there a reason behind the "A" designation? |
ArtechnikA |
Aug 26 2008, 07:14 PM
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#5
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
With both "S" (aluminum) and "A" (steel) front calipers being 3.5" is there a reason behind the "A" designation? Frère to the rescue again.. The 'A' calliper (The Brit spelling, as I'm kinda quoting...) was originally developed for the Alfa-Romeo. For those of you playing at home, you'll also recognise that the Weber carburetors were also originally developed for the Alfa, which has slightly shorter cylinder-to-cylinder spacing on their V-6's - which is why Porsche intake manifolds have slanty end runners... |
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