Is there any reason I should not remove the dust shields from brhind the front and rear wheels on my mini so that the brakes will have more air directed to them? What is the function/purpose of the dust shields - why does mini put them there to begin with - don't they restrict air flow? Why do I not hear of more people taking these off - tyring to get more air to the brakes before upgrading to a bbk?

 

My guess is to keep dust and dirt out of the brakes for the everyday mini driver, sounds like a good idea. That side of the brake system is very exposed, so higher chances for stuff to get jammed between your brakes and rotors.

More air: Please!! Biggest weakness if you track, so i'm thinking of building some brake ducts to get more air. Dust sheilds will either go or get modified. I'd rather stick with the OEM size and invest in cooling vs. just going bigger.

phil.

 

The only down side is that if you super heat the rotors in the rain, the rain will cool them quickly causing the potential for warping - been there. There is apparently little warping potential with larger rotors - for the Mini...

 

Actually if you look (as I remember) you will see that these shields are designed to direct air into the rotor.

If you remove them then make sure to insulate the ABS- DCS sensor line.

 

Rotor Warping - This is an interesting topic. Last summer I went through a set of Ferodo 3000's (front) brake pads in 3 days at Mont. Tremblant. It's pretty highspeed track (they used to run F1 there untill it moved to the Montreal track).. anyways - Go to Tremblant!! Amazing track!

Back to warped rotors. At the end of the 3 days my rotors became pretty warped (that's what I thought it was at the time), but through some research and talking to some mechanics I discovered that it is VERY difficult to warp rotors. It is un even buildup of brake material that causes the brake shudder. To get rid of it I ran my racing pads for a week and did some break in cycles to basically grind off all the uneven spots.

Rain - I don't see how rain alone can cool down the metal so fast and uneven to cause warping. Maybe superhot (red) rotors in ice cold water, but not on a car.

After grinding the uneven brake pad deposits off my rotors they have been good ever since.

Just my 2 cents, but I will never point the finger at warped rotors again.

phil.

 

i took mine off when i started using a brake cooling kit. i haven't had any troubles with them being off. it is my track car and daily driver so it sees rain. no rotor warp issues as of yet.

 

This problem I site may be a very specific to a given application. However, the dust shields direct cool air as Onasled wrote, but they also prevent water from drowning the rotors from between the tires. This information came to me by way of Tire Rack and two other companies who campaign race cars during casual conversation over the past 10 yeas or so. I was told the reinstall these at once to eliminate the problem...never had the car long enough. For track work, removal is desirable, but the water thing is still a mystery. Perhaps Todd can offer an explanation...

I cannot say why larger brakes are not affected. I can only assume that the greater heat sink helps.

Warping also comes fromt improperly torqued lug nuts; either too tight or unevenly torqued. Once warped from this condition, all you need to do is properly torqued the wheels and take her up to about 100mph and hammer the brakes a few times and they'll straighten right out.

This is all based upon personal experience.

 

dust shields are there to prevent water, mud, dust, dirt, and general crud from getting on the rotors and casuing difficulties with braking. they also cause the rotors to run hotter by ~50-75F(on a typical vehicle)...not enough of a temperature delta to really justify removing them.

and as far as "warping" of rotors is concerned, if you can add a few thousand psi to the lug torque, you may warp a rotor, the shuddering that you feel is due to thickness variations on the rotor. this can be from excess pad material build-up, or from uneven wear by the pads. cast iron is pretty difficult to warp, wood and plastics...yes; metals?? c'mon, lets have a common sense rally

 

Properly lugged and set up brakes on my 1999 civic Si warped on schedule within every 10,000 miles of driving, and I put 200K on the car. The dust shield suggestion wasn't a casual one, it was emphatic from everyone I spoke with. My experience, steel rotors warp very easily, especially with a quick build up of heat, and, quick dissipation from water; if one side is cooled drastically relative to the other, warping will occur. FWIW 50-75f is a big deal if it's a borderline condition.

I still believe in removing these if the car sees a lot of track work. As far as temp deltas; it will depend upon the application and the venue.

As far as warping rotors by over torquing...no, it takes far less than a few thousand psi to make a huge difference. Steel acts just like fabric when it's over torqued; the face of the rotor becomes distorted with heat and the bolts over stretch. That's why torque settings exist for wheel lug nuts.

Uneven pad material build up? How exactly does this occur? I can understand that it might be caused by a warped rotor placing uneven loads on a pad, but a smooth operating rotor...

 

Here's a link to a Stoptech technical white paper on pad transfer.
http://www.stoptech.com/tech_info/wp...rakedisk.shtml

 

WOW! I wish I could show you some of the micro-graphs of "smooth" rotors.
steel may act just like fabric when over-torqued, but cast iron is elastic, most cast iron used for rotors will stretch by as much as 4-18% of the affected cross-sectional area before deformation begins. rotors experience thickness variations due to the fact that brake forces vary over time-the first instant that the brake is applied, more wear occurs, than at, say, the instant before the brakes completely release. drivers typically refer to this shuddering feeling, incorrectly, as 'warpage'.

 

I am familiar with the article, I've read it a few times in the past. I do not contest the information.

However, warping is a condition that occurs no matter what the article says. My eyes aren't that bad. And yes, cast iron - I wrote steel - is elastic and will deform under certain conditions - improper torquing followed by heat. As I wrote, the cure is to properly re-torque the wheels and then re-heat them. They will return to normal - this is clearly not caused by material transfer.

The other condition I wrote about is also pure warping casued by super cooling one side of a very hot rotor.

The above two conditions are easy to witness on a rotor lathe or grinder...it's not pad material transfer.

The article, most of which I've long forgotten, sites one qualifier, properly torqued lug nuts; proper torque value and proper torquing order. The other warping condition I wrote about was very specific to my experience with my car. I do not know if it occurred to other cars of the same model or to other makes. I can only say that three different organizations were very quick to point to the lack of a dust shield, along with high heat and super cooling with water as a cause. This, thru deduction, leads me to believe I'm not the only one.

I offered my experience above, that is all. You may not find it on the web, but if you're open to the experience of others you might just put my experience in the back of your brain for another day...perhaps when and if you experience the same thing...perhaps.

 

meb
I posted the link as a response to your question on how uneven buildup occurs. I didn't mean to leave an impression that rotors don't warp. I have never had a GM product that didn't develop warped rotors. I know its true!

 

The link was great to read. About 3% of what I read really sinks in. So, I have to read something a few times in an effort to commit it to memory. I did not remember the pad material transfer stuff, good to know. No apologies necessary no offense taken. I think Polmear doubts the existence of warping rotors...

I simply could not keep rotors on the Si - warping was a serious problem. It sits outside getting ready for a season along side the Mini, but now shod with Type R calipers and Prelude rotors. The Type R hubs and axles add a 5 bolt pattern, but the added cost plus different wheels and tires was too much.

I began a follow-up Thread under Wheels and Tires titiled warping rotors. I've enlisted the help of a brake engineer I occasionally speak with. Check it out.

 

I know that metal bends. I've seen calipers deformed to the point of looking cartoonish. however those were after being under loads of up to, and often over, 7ksi. I am a caliper design engineer-there are calipers I helped in the design of on several production models of heavy & medium duty trucks. I've been doing this for over 10 years. I'm stating that what MOST people run into and incorrectly call "warped" is disc thickness variation, due to non-linear application of braking forces during deceleration, and initial surface roughness. and I've known some people that can feel this starting with a few microns of wear, and most people can recognize it after a few hundred microns.
When I think of warp, typically what comes to mind is the distorted thing you get after leaving plywood in the rain and sun, uncovered, for a few weeks, and after 6 years of seeing warranty evidence, I have yet to see a 'warped' rotor.
The over-cooling distortion that you describe will probably never occur during normal everyday driving. Thermal shocking like that is much more likely in racing, or with over-loaded trucks. The mini already has a massive thermal volume in the stock rotors-as big as several of the medium trucks we work with; so getting that mass to a temp where such a thermal catastrophe could possibly occur, well...
Finally, yes 50-75F is not much, and these temps occurred on some medium duty trucks, during two seperate tests in LA city traffic testing, the same trucks saw no real temp difference during a suburban traffic test (mostly highway driving). removing the shields to run this much cooler is not really that much of a risk, though; how often do you take your mini off-road, or drive through deep water?
I'm not trying to offend, just to educate, if I can; (If I'm wrong, I'll whole-heartedly recant every word, cause I also like to learn-haven't stopped going to school over the last 15 years- I never know enough about a lot of stuff) but I guess I should have made these clarifications, it's just I don't often feel like typing so much.

 

Polmear,

There were two sentences you wrote in the context of my experience that prompted me to reply.

c'mon, lets have a common sense rally

as far as "warping" of rotors is concerned, if you can add a few thousand psi to the lug torque

I stated my experience. Walk into most mechanic shops and the guy reinstalling wheels, you know, the one with a huge beer belly and a%$%s crack, dumps three hundred pounds of weight onto his four foot long wrench. It actually takes less, far less torque on the lug nuts to warp rotors; typical torque settings are in the 80-100ft/lb range for most passenger cars. 150ft/lbs is enough to cause a rotor to warp, within easy reach of most of us...more so if all the lug nuts are torqued with some X% ft/lb difference.

You mocked my experience with the common sense comment...you hurt my feelings - where the hell did those smiles go? The real message in my reply, none of us has seen eveything. Some more than others, but certainly not everything.

I began a Warped rotor thread under Wheels/Brakes/tires. Check it out...contribute...I've got my eye on you, don't mock me - insert another missing smile. Where do those icons go after editing?

What do you know about Honda rotors, or Honda's braking systems? This problem (warping) plagues most of the Civic line.

Michael

 

I apologize for anything I said that may have hurt your feelings. The smiley's were there as I typed it, and for some reason, didn't get put into the post, might be the firewall I'm behind; but my last post I know had 1 at the very end, and now is gone. (well it was gone before I started this reply, now it's back) maybe I'm just getting senile.
As far as the "common sense rally" I guess I should fire up the old brain before I put my typing fingers in gear. ( I often run off at the mouth, too...could be the Tourett's ) or maybe I'm just insane, either way I certainly didn't mean my comments to be hurtful.
and as for the comment about how much torque is required to bend a rotor, I just ran the math and it all depends on the initial length, cross-sectional area, and change in length. depending on what initial length I use (distance from the application of force to where the measurement is from) and the c/s area, a change of 150 microns can be induced with as little as 107 lbf. guess I should learn to put my brain in gear first

 

Polmear,

I wasn't hurt...well not really. This is the part where we drink beer...but not so much as the 300lb guy...

Thanks for the info regarding the rotor.

Michael :impatient Look! There they are!

 

since all car braking systems are generally the same, with few variations, I can say that I know a lot about Honda's braking system before I ever see a spec on it. Now if you have some specs, I can tell you more; but I did some other investigating here. I have a few questions...
what kind of rotors did you replace with? did you ever check run-out with brand new rotors? did you ever have the hub investigated for run-out? what type of pads were you running?
all these issues are general causes of the problem you describe. there are also other causes. guess what I'm saying is I need some of these answers before I can say more.
decided to engage the ole brain today

 

I always used Brembo rotors - stock size. Once or twice with gas slotting, but never drilled. Pads were Hawk Street/track - can't remember the part number. Steel lines and Motul dot super four...same pads and fluid I'm using in the Mini.

I never checked run-out ...oh goofy me - on either the hub or rotor. Sort of dumb, I know. I'll need to invest in some proper guages. This could have been the cause, I just never thought of it...my brain ain't so good sometimes either.

The Si now has Type R calipers and Prelude rotors. We'll see how this works...alhtough I'm not the driver this tiime around. I'll make sure hub run-out is checked before our first DE event. Thanks for the heads up Polmear

Michael

 

the reason I mentioned the run-out, on new rotors was a colleague mentioned he got rotors for his Si from a local el-cheapo parts discounter, whose murrays name murrays I wont mention, and right after putting the rotors on he went for a drive, and somehow gained an ABS system when he used the brakes :impatient

 

Ouch.

the engineer friend cannot explain the warping along with water relationship. Oh well.

 

Does anybody have a recomendation for a manufaturer and where I buy some insulating tape for the ABS - DSC line? Do people agree this is necessary if you're going to remove the dust shields?

 

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