brake temps -how hot is too hot?

[lindermant]

I'm planning to install a set of moon disc hubcaps. I've read that these could cause overheating problems (no vents in the cap to allow cooling).

I have an '05 Civic coupe (front disc/rear drum), and using a Fluke mini 62 IR thermometer got the following readings:

85F all four corners (ambient temp after sitting in garage overnight)

after my 37mile commute (30mi highway, 7mi stop-n-go city):

(LF)120F (RF)119F

(LR)112F (RR)112F

I'll monitor the temps over the next few days to establish a baseline, and again when I install the moon discs. But my question is how hot is too hot, at what point should I expect to encounter brake fade and/or rotor damage (warping)?

[krousdb]

I'm no expert but I would expect well over 200F before warpage would be a problem. If Im not mistaken, warpage is caused by extreme tamperature changes in a short period of time. Like spraying cold water on a hot rotor.

I doubt that a gassaver would overheat thier brakes, moon disc hubcaps or not.

[SVOboy]

I wouldn't worry about it unless you do some hardcore 100-0 braking.

By the way, welcome to the site! Feel free to start a thread in the introductions forum and tell us a little bit more about yourself and your civic. :)

[JanGeo]

My Geo was dragging a pad and heated the rotor and the wheel got hot too but it didn't damage the rotor it cooked the bearing - started rumbling.

[Ryland]

at around 380F metal will turn that pretty blue color, depending on the alloy of steel, and I haven't seen many warped rotors that didn't have signs of blueing, and have seen some pretty straight ones that were blue.
for an 05 civic, I think that has a 5 lug bolt pattern wheel, correct? the new civic hybrids have near disk, vented alloy wheels that are honda's 5 bolt pattern.

[SVOboy]

05 civic was still 4x100.

[lindermant]

Thanks for the replies; I'll follow-up with a post showing the delta in temps after the discs are installed. As kdb surmised, I'm pretty easy on my brakes so it might not be a huge difference; either way it'll be neat to see the numbers.

Ryland, my '05 Civic is the base coupe with 14" 4x100 steelies & hubcaps.

I'll drop an intro thread tonight when I get home from work (really shouldn't be goofing off and posting now, but... :D

[Ryland]

my '05 Civic is the base coupe with 14" 4x100 steelies & hubcaps.


then Insight wheels will fit perfectly, www.carpart.com is where I search for things like that, when I need to get new tires I think I'll look at some insight rims, around 11 pounds each for near disk alloy wheels, skip the hub caps and steel rims, save weight and be more airodinamic!

[SVOboy]

Or pimp some HX rims, :)

[philmcneal]

he has the same car as me! just an auto instead of a 5spd ;)

buty his gears are more tuned for efficency than mine grrr :( and he has other goodies like keyless and an armrest ;(

[lindermant]

ryland, I never considered Insight wheels - interesting, but if I go alloy it'll either be HX or Civ Hybrid wheels.

phil, I do have an armrest but no keyless entry. heck, I even have roll-up windows to go with my manual locks :D

[SVOboy]

Sweet, roll ups for life!

[MetroMPG]

I'm with Dan on this one: hypermiling doesn't lend itself to overheated brakes. I sealed up my plastic wheel covers a couple of months ago and haven't had any trouble at all (though I should say: I don't live in the mountains).

Maybe someone with more experience can talk about the smell of hot brakes vs. the danger of heat-related damage. I suspect if you ever got them hot, you'd start to smell them long before they were in danger of warping/bursting into flames/boiling the brake fluid.

Also one tidbit I remember from a racing course I took: because the brakes were so hot at the end of each lapping session, the instructors always encouraged us to stop the cars in the pits with the clutch (engine off), rather than the brake pedal. Their rationale was that squeezing the calipers that last time when parking the car meant the pads wouldn't retract as much (compared to while driving), and they might create (insulate?) a hot spot on the rotor, leading to warping from different rates of cooling.

[Gary Palmer]

Well, in my perspective, I wouldn't worry at all about overheating your brakes by putting on the moon hub cap's.

Regarding what it's like to overheat. Their are several things which will happen. First, and one of the most important, is when they start to get hot, you start to loose some of your stopping power. With rotor's, the amount of impact is profoundly less than with drum's and consequently, although they can get pretty hot, you can still stop the car, although it can take a significantly greater effort. Caution, if you try to slow down and you can feel that it's taking more effort, then you need to do something to let the brakes cool down. The best course, if you have a stick is to go down a gear or whatever it takes to get your speed down and keep it down, so you don't need to use the brake's.

Second, when you start to heat the brakes up, they do smell and while it's hard to describe the smell, it basically smells like something is getting smoldering hot and smelly.

I've managed to warp rotor's and drum's, but in both cases, what it came down to was I was going downhill, in a heavily loaded vehicle, with a loaded trailer and with an automatic transmission. Additionally, in going downhill, their were also a lot of very steep, hairpin turn's, such that if you did not keep your speed down and keep it down, you ended up standing on the breaks, on every turn, as you go down the hill. It generally takes a pretty steep descent and a large number of hairpin's, to create a circumstance where thing's start getting hot, as far as brake's, rotor's, drum's and so forth.

The only other thing I can refer you to, is if you find a long, fairly steep grade, which semi's have to come down, if you think of the "unique" smell you encounter, that is hot brake's, rotor's and drum's.

In short, I think that unless you are driving something heavily loaded, down hill's, with a lot of twist's and turns, you are probably not going to need to worry about getting anything to hot.

[lindermant]

metro & gp - thanks for the info!

I checked my brake temps when I got home tonight (much cooler wx on the route home), and they barely broke 100F. Forgot to check ambient temps before I left work...

[Gary Palmer]

So, where are you located?

p.s. welcome to gassaver's

[rh77]

A lot warped rotors out there are as a result of over-torquing the lug nuts. Make sure if you take it to a shop or rotate the tires yourself, then torque to the factory specs. ...and by the way, welcome to GS!

RH77

[lindermant]

GP - I'm in Northern Virginia.

rh77 - thanks for the welcome!

[krousdb]

Good to see you here too Lindermant!

[lindermant]

UPDATE:

my moon disc hubcaps arrived today! I installed them and went for a drive (very representative of my daily work commute listed above) and got the following numbers:

85F all four corners (ambient temp after sitting in garage overnight)
28 mile trip, good mix of highway and stop-n-go city:
(LF)114F (RF)114F
(LR)100F (RR)100F

These are the first datapoints with the new hubcaps, but it doesn't look like my brake temps will suffer much at all.

Now for the pics:

http://www.cleanmpg.com/photos/data/500/Dsc00892.jpg

http://www.cleanmpg.com/photos/data/500/Dsc00893.jpg

No A-B-A runs yet, I'll get around to that later.

[SVOboy]

That second picture is niceness. How much were they?

[lindermant]

$140 shipped

[SVOboy]

Not bad, they look really good. Match the car well! Looking forward to the A-B-A

[MetroMPG]

Nice.

I'd be (pleasantly) surprised if anything conclusive showed up in an ABA with a ScanGauge; I suspect it'd be a small gain.

Regardless, this is one of those common sense changes where you don't need to test to know it's better than before.

[ketel0ne]

Looks great!

[WisJim]

I found some (set of 4) genuine "Moon" discs on eBay a couple of weeks ago, 13", and got them for $50 including shipping. One has a little dent and one has a scratch in the clear coat, so I figure that is quite a deal. Put them on our 2000 Metro and they look great. Not sure if they make a measurable difference as I have no way to tell, yet, but I was missing a hubcap anyway, so thought these were worth trying.

Now I need to get some "Mooneyes" decals, and maybe a Mooneyes tee-shirt for my wife.

[SVOboy]

Got any pictures for us?

[Matt Timion]

I've been looking for Insight rims for a while now... the cheapest I can find is around $180 each.

Considering the price, I'd rather just buy HX rims and get hubcaps than buy Insight Rims.

[Headshot Zod]

I know this is an old thread. But MoonEyes (http://www.mooneyes.com) carries those original discs. And I think JC Whitney probably has a cheaper version. They also have decals and the like.

[basjoos]

Dispite having smooth hub caps, front and back wheel well skirts, exhausting my radiator air into the front wheel well and doing a lot of mountain driving, I have not had any problems with brake fade or warped discs.

Most discs get warped when someone does a lot of hard braking and immediately afterwards sits for awhile stopped at a red light, etc. with the hot pads clamped down on the disc so that the clamped part of the disc heats to a high temps while the rest of the disc is cooling down. If you have to stop after a lot of hard braking, it if best to hold your position with the parking brake or with the auto trans in "P", rather than sitting there holding the brake pedal down.

[onegammyleg]

Discs are made from cast iron and this metal has a temperature limitation of about 1220F before it changes composition (structure).
Cast iron is used because it holds it shape and dimensions the best.
Discs are not made from steel.

Most suspected diesc warpage problems are not actually so.
In most case they end up being an uneven transferance of pad deposits that have transferred to the discs surface.

The high spots of depositied friction material and the disc in that spot keep getting hotter and hotter untill it bonds with the disc.(1200 to 1500F = cementite)

if you have just noticed the start of a vibration but the discs havent reached that high temperature the depsoits can be broken off the disc with garnet paper.(not sand or emery paper)

On a disc that has bad juddering it is often fixed with surface grinding , and while this does make it good for a short time it doesnt undo the changes that have occured in the disc metal itslef.

The localised hotspots are still there and will affect the evenness that he disc heats up and cools forever.

Its just a matter of time before this disc is juddering again.

If you have a juddering disc , throw it away.

[onegammyleg]

...and most fade is caused by the lubrcating effect of the gasses produced from the hot pad friction material and not from the disc being too hot.

[onegammyleg]

yeup :thumbup:

[Sigifrith]

How did the Moon eyes turn out?
Where they of any value?

[lindermant]

How did the Moon eyes turn out?
Where they of any value?

no measureable FE gain in the time I had them installed; they were very noisy at slow speeds so I took them off. I thought they looked cool, but that's about it :D

[cfg83]

lindermant -

I never had a problem with overheated brakes. The Saturn service guy warned me but I ignored him because I was never a "performance" driver that would push it to the limits.

And the moons were stunning regarding the looks. I had them powder-coated on my previous SC2 :

625

However, they became my bane. On certain road bumps, the front passenger one would go flying off. I *think* this had something to do with my Saturn front wheel drive balancing, but I have no proof, only a similar story from a friend. I couldn't justify keeping them on.

If it weren't for that, I would have lived with the scratchy sounds. I did it to complement the looks of the car, not for saving gas.

CarloSW2

[cfg83]

theclencher -

There must be a way to attach them that eliminates the noises. Perhaps a gasket?

I tried electrical tape over the teeth, but that didn't work. A gasket would be better. Over time, I think the teeth would scrape through. The key would be finding a gasket made of the right material. Also, the teeth bend easy, so I think the cover can become loose after multiple on/offs.

I think the real deal would be to go with real racing disks that require 3 holes screwed into the rim.

Since my SW2 has fancy allows, I can't install the racing disks on them. However, I have recently been staring at the "aluminum wheel center caps" on my Saturn and wonder if a "donut" shaped disk that exploited the center caps as a locking base might work. Just a thought experiment, though.

CarloSW2

[lindermant]

Were the teeth the source of the noise, or some other part? I'm not familiar with the exact geometry of those disks, but I would think the teeth need a secure bite and the rest of it either needs enough clearance (wheels flex) or a gasket to isolate from metal to metal contact.

On my mooneyes brand discs, it was definitely the teeth causing the noise. They were a tight fit, but at least they never flew off ;)

[cfg83]

theclencher -

Were the teeth the source of the noise, or some other part? I'm not familiar with the exact geometry of those disks, but I would think the teeth need a secure bite and the rest of it either needs enough clearance (wheels flex) or a gasket to isolate from metal to metal contact.

As lindermant said, it is definitely the teeth. I still have them, even the ruined ones that flew off (they mock me!!!!!!!!!!). I'll try to post a picture. I think they are proof that the steel rim is flexing.

CarloSW2

[cfg83]

theclencher -

Here's the pics of the moon disk :

636

637

638

I think a gasket would be troublesome because, as you can see (with your mind), the gasket would be "pulled off" when you pushed the disk in. Also, I forgot that the teeth are little "double teeth", or maybe little grabby fingers.

CarloSW2

[JanGeo]

I was watching some car videos on utube yesterday and noticed a BMW commercial for the fastest car and they had the speed disks on it - funny thing was they used an M3 to film the rocket? powered bullet car doing a speed run with a big camera hanging on the outside of the door.