# ZIMMERMAN"S



## D3hd3nd (Jun 18, 2008)

old thread....


_Modified by D3hd3nd at 4:32 AM 1-27-2009_


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## spitpilot (Feb 14, 2000)

*Re: ZIMMERMAN"S (D3hd3nd)*

I've had these rotors on my cars for years...some drilled, some plain...work fine. Only difference I saw between drilled and plain....pads seemed to wear a bit faster with drilled rotors. Any of the EU OEM quality suppliers...ATE, Brembo, Zimmerman make good stuff..stay AWAY from the plain brown box Chinese knockoffs..I"ve heard bad things about warped rotors etc...not good to skimp on brake parts..you wanna put cheapo poor quality lenses on your marker lites..go for it...no body's gettin hurt if they crap out..brakes another story!


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## VWn00b (Mar 4, 2005)

*Re: ZIMMERMAN"S (D3hd3nd)*

I have a set of cross-drilled Zimmermans. 10.1 vented, stock size for the mk3 2.0.
Been great for the past...2 years I think. Been beat up on track days with aggressive pads and it's only now starting to get a small lip on the rotor.
Another nice thing about the Zimmermans is that on the cross-drilled rotors, they are casted with the holes, so they are much less prone to cracking.


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## GTijoejoe (Oct 6, 2001)

*Re: ZIMMERMAN"S (D3hd3nd)*

I used Zim. cross drilled for years, they do eat pads quicker, and corrosion over a few yrs will force you to replace them.
I use brembo disks now, nothin fancy.


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## jettasmooth (Aug 7, 2002)

*Re: ZIMMERMAN"S (GTijoejoe)*

zimmerman 11" fronts with audi 5000 G60 dual pistons..... they rock, and there is definitely no need to go cross drilled. I stop just find with vented rotors, and im running a 1.8T in my MK3.


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## D3hd3nd (Jun 18, 2008)

*Re: ZIMMERMAN"S (jettasmooth)*

nice nice and keep it coming... I'm not sure if im going XD or just solid yet...


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## JB FTw (Apr 9, 2008)

*Re: ZIMMERMAN"S (D3hd3nd)*

is it worth getting drilled/slotted ones? or is oem good? im looking at ecs for 20th ae 12.3mm brakes. are the OP ones godo?


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## spitpilot (Feb 14, 2000)

*Re: ZIMMERMAN"S (JB FTw)*


_Quote, originally posted by *JB FTw* »_is it worth getting drilled/slotted ones? 

Only for style points...if you're willing to pay a bunch of extra $$'s for your car to look fast..then go for it. Upgrading to larger diameter OEM solid rotors will add to braking power (since the caliper force is applied to larger rotor and braking torque is forceXradius..you get actural braking power increas by spending money on larger rotors)...X drilling and/or slotting will not change braking power, and unless you track your car (and I'm not talking drag races here) you won't benefit from any added cooling from X drilled rotors. http://****************.com/smile/emthup.gif


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## lubok (Feb 7, 2008)

*Re: ZIMMERMAN"S (spitpilot)*

using larger rotor and same caliper, will not stop better. Larger rotor will dissipate heat much faster and will withstand more to brake fade but it won't provide you with shorter stop. Larger rotor means more weight= more unsprung weight which equals crappier handling and slower acceleration. If you are experiencing Brakes fading even on street you are using crappy pads.


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## spitpilot (Feb 14, 2000)

*Re: ZIMMERMAN"S (lubok)*


_Quote, originally posted by *lubok* »_using larger rotor and same caliper, will not stop better. 
 Go back and read your high school physics book! Same caliper = same force applied to pads, same pads mean same friction force applied to rotor...same force and say 10% larger rotor = 10% larger braking torque!..And you get the additional heat sink and larger rotor area for heat dissipation and fade resisitance as you mentioned!... http://****************.com/smile/emthup.gif


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## lubok (Feb 7, 2008)

*Re: ZIMMERMAN"S (spitpilot)*


_Quote, originally posted by *spitpilot* »_ Go back and read your high school physics book! Same caliper = same force applied to pads, same pads mean same friction force applied to rotor...same force and say 10% larger rotor = 10% larger braking torque!..And you get the additional heat sink and larger rotor area for heat dissipation and fade resisitance as you mentioned!... http://****************.com/smile/emthup.gif 

In the case mention above going from 288mm rotor to 312mm it won't make a difference. the pads in 288 application are allready using their 100% area to stop the spinning rotor. Bigger does not mean better all the time. for your argument. Lets say the vehicle with stock brakes stops from 60mph to 0 in 100'. You are arguing that using 10% bigger rotor in front will give you 10% more braking power. Lets say the brake distribution is 70-30 front to rear. That would mean using the bigger rotor you should be able to stop 7' shorter of the original brakes. Sorry to burst your bubble but it isn't that easy. The brakes will be more prone to brake fade and will be more accurate performing under harsh conditions but there is no way in hell that they will give you 10% shorter stops.


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## spitpilot (Feb 14, 2000)

*Re: ZIMMERMAN"S (lubok)*

Since you obviously haven't studied Physics, let me provide some factual enlightenment to this discussion of the impact of moving the stock calipers further out from the axle centerline. I quote from Physics For Students of Science and Engineering..Part I , Chapter "Rotational Dynamics, page 216:
"If we apply a force F1 at the point a (closest to the axis in the example) the stick will rotate, tha is it will accelerate rotationally from rest about the axis...If we exert the IDENTICAL force F1 at the pont b, (further from the axis) the stick will again accelerat rotationally; however, the acceleration will be greater than before. Everyday experience, such as pushing revolving doors, confirms the fact that to obtain a great rotational effect with a given force we apply the force at a point farther from the axis of rotation." Now of course brakes are meant to cause negative acceleration but the relationship holds, and since increasing the (negative) acceleration will decrease the time it takes to stop and the distance traveled, there will indeed be the improved braking action I claimed....Of course the friction forces applied by the pads will change with temp etc., but for any given force they apply the stopping effect (negative acceleration) will be greater the further away from the axis (axle) the gripping force is applied. Of course there is a practical limit to how large a rotor can be used in a given car...so to gain really large increases in stopping effect the more efficient way is to vastly increase the force being applied to the rotor...can you say 4 piston calipers?
























_Modified by spitpilot at 9:24 AM 1-27-2009_


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## GTijoejoe (Oct 6, 2001)

*Re: ZIMMERMAN"S (lubok)*


_Quote, originally posted by *lubok* »_using larger rotor and same caliper, will not stop better. Larger rotor will dissipate heat much faster and will withstand more to brake fade but it won't provide you with shorter stop. Larger rotor means more weight= more unsprung weight which equals crappier handling and slower acceleration. If you are experiencing Brakes fading even on street you are using crappy pads. 

Oh my the arguing hurts my eyes








OK FYI time: 
As a brake system's pressure will equally generate the same max value regardless of where the calipers are placed, since all of the components are exactly the same, the same normal force from the caliper's piston(s) (based on piston area and pressure) will always hold true to be the same. Therefore brake force can be simply defined as:
Calipers normal force x friction mu (of the pad) = brake force
Next we can simply state brake torque:
Brake force x effective radius = brake torque. 
Now that this is simply broken down it should be obvious to understand.
As you increase in disk size, you can also increase the caliper's effective radius (please note only because it is a bigger disk does not mean it has a larger effective radius, normally only increased thermal mass) the brake torque is proportional. 
Larger effective radius (from larger disk) increases brake torque, thus increases brake gain.
When you increase brake gain you potentially have the ability to decrease stopping distance. But please understand not to get things twisted, vehicle brake distribution is very important in achieving maximum brake effectiveness, just increasing the gain in the FR and not changing the rear by the same percent, will potentially INCREASE your stopping distance. Most big brake systems do NOT change the gain of your original system (by some tolerance), they actually try to match the vehicle's stock gain, especially systems that only offer a FR BBK. BBK's will increase thermal mass with a larger disk, and also increase the effective radius, so they than can control the gain by decreasing piston size and/or changing friction properties.
Everything that I have stated is known to be true in brake design, if you didn't understand it, than read it again. If you still didn't understand, than ask your questions and I'll take you to school. http://****************.com/smile/emthup.gif


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## lubok (Feb 7, 2008)

*Re: ZIMMERMAN"S (spitpilot)*

I not arguing with the physics but you have stated that by increasing a rotor by 10% you will increase your braking by 10% which is not true. Increasing rotor size by 10% will have such a small decrease in time/length to stop vehicle it will be almost impossible to tell. To get a noticeable brake improvement you need to increase the size of the pad and provide it with more even distribution of pressure. Just like you said


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## spitpilot (Feb 14, 2000)

*Re: ZIMMERMAN"S (lubok)*


_Quote, originally posted by *lubok* »_I not arguing with the physics but you have stated that by increasing a rotor by 10% you will increase your braking by 10% which is not true. Increasing rotor size by 10% will have such a small decrease in time/length to stop vehicle it will be almost impossible to tell. To get a noticeable brake improvement you need to increase the size of the pad and provide it with more even distribution of pressure. Just like you said
 Nobody's mentioned tires yet!





















From what test data I've seen tires alone can impact stoppin distances very signifcantly....but if what you say is true..that 10% increase in braking torque does diddly squat in terms of braking performance on the road..then why does VW (and other mfgs) waste money and increase weight/reduce mpg by adding larger rotors on their performance models? Car 'n Driver, Road 'n Track all give much better 70-0 stoppin distances to the GTI...be interesting to see GTI # with 205/55 tires on it! Or my Rabbit with 225/50's...that would end the "discussion" I'm willing to do the test if you guys will contribute to a set of 225 tires!


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## lubok (Feb 7, 2008)

*Re: ZIMMERMAN"S (spitpilot)*

I am not very familiar with A5 platform but i know simply upgrading front rotors on a4 platforms from 20AE/GLI models didn't do anything other than looking good. Tires are very important. To test for brakes/tires. Accelarate to 30mph and slam on brakes. If you will be able to get abs working on smooth and dry surface than the tires are not the best gripping tires. For summer/ auto-x I use Falkens RT615. I put about 6K miles on them and they are done, but they are the best tires I used so far. I will be getting next set within few weeks


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## GTijoejoe (Oct 6, 2001)

*Re: ZIMMERMAN"S (spitpilot)*


_Quote, originally posted by *lubok* »_I not arguing with the physics but you have stated that by increasing a rotor by 10% you will increase your braking by 10% which is not true. Increasing rotor size by 10% will have such a small decrease in time/length to stop vehicle it will be almost impossible to tell. To get a noticeable brake improvement you need to increase the size of the pad and provide it with more even distribution of pressure. Just like you said

Alright than, just making sure. You are 100% correct, any change in brake gain is not proportionally linear to braking distance http://****************.com/smile/emthup.gif 

_Quote, originally posted by *spitpilot* »_ Nobody's mentioned tires yet!





















From what test data I've seen tires alone can impact stoppin distances very signifcantly....but if what you say is true..that 10% increase in braking torque does diddly squat in terms of braking performance on the road..then why does VW (and other mfgs) waste money and increase weight/reduce mpg by adding larger rotors on their performance models? Car 'n Driver, Road 'n Track all give much better 70-0 stoppin distances to the GTI...be interesting to see GTI # with 205/55 tires on it! Or my Rabbit with 225/50's...that would end the "discussion" I'm willing to do the test if you guys will contribute to a set of 225 tires!























The concept of tires is very similar to pads, only because they are bigger does not increase the friction, larger tires have a better ability to deal with heat same as pads. As the tires heat up the friction characteristics change, the ability to keep constant heat range gives best performance, just like a pad. So basically you will be looking for a much sticker tire to base your performance needs. 
Of course dealing with brakes the size or gain of your brakes DOESN'T STOP YOUR CAR.... your tires do. As you match a 0.8, 1.0, or 2.0G stop, the tire friction must match. http://****************.com/smile/emthup.gif


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