Brake dust sheilds, raining day

Because I took off my oem 10.5 solid front disk off my Alfa Romeo spider,and installed 12.19 vented disk on the front. I removed the dust sjeild,as they don't fit. Driving home from work,in the rain, took my exit off freeway, brakes down to get off the offramp

. No brakes, had to ride them to get stopping power back

 Am I right that lacking dust shields the rotors got wet, causing the lack of brakes and definite raise in heart rate?

Our racecars have no dust shields and they do fine in the rain both on and off the track. I don't see how brakes getting wet would stop them from working.

But on the track you are on and off your brakes,often. I was on the freeway for 20 mins, no brake action. Might be a different situations.

In reply to buzzboy :

I imagine different cars are differently prone to soaking their brakes, depending on what hangs down where, and how long the water stuck around would be affected by temperature (i.e. on track I'd think they'd dry pretty quick).

Water can be a lubricant. If the pedal was firm but there was reduced braking action which came back, then I'd say wet brakes were the simplest explanation.

I know soaking drum brakes would certainly prevent them doing much stopping 'til they dried out.

IDK, we don't have dust shields on the rally car, and even in muddy/wet events where we are CONSTANTLY in water I've never noticed any lack of braking power. And unlike a track car, rally car isn't constantly on the brakes hard. Especially on long transits (in the rain), still never had issues. I've used the same pads (HPS) for almost 7 years :)

what pads are you using? maybe it's just a compound that needs some heat for good initial bite, so driving with no brakes for 20 minutes they were simply cold and lacked initial bite, regardless of water. Water may have kept them cooler than usual, but IDK.  the rotors are going round and round with the wheel and any water that gets on them just flings to the outside and off. Not like there is "standing water" on the rotor face.

Side point: you changed the rotor size, but did you also change the calipers, or just move the old ones outward?

My DD Golf has no dust shields - tinworm got them!!!

No issues even in cold, rain, snow etc.

This is topic is relevant to my interests as tinworm also ate the shields on my 84 Rabbit.  I’ve been wondering if it would be worth the $$ to replace them.

Maybe that money would be better spent on other parts.

In reply to irish44j :

Updated the calipers to 2001 Porsche boxster 4 pot brembo's

Alfaromeoguy said:

In reply to irish44j :

Updated the calipers to 2001 Porsche boxster 4 pot brembo's

So is your braking otherwise good? Did you change the master cylinder (not sure what the piston areas are between your Alfa stockers and the Brembos). I know when I upgraded a prior car's stock calipers to big Wilwoods with the stock M/C, they took a ton of pedal effort to bite hard.

Now I'm really wondering. I've definitely had wet drums not work; I can't recall ever having issues with discs, but I've never yanked the dust shields.

In reply to paranoid_android :

Pick and pull.for shields only $

In reply to irish44j :

When dry they work great, no power boost, so nice pedal feel and the start stopping at top of travel

In reply to Ransom :can be a wee bit exciting, like a old British  car 0 to 60 in 20 secs. Loose those brakes because  of wrong brake fluid, 60 to mach 2 ....now.  lol

Alfaromeoguy said:

Because I took off my oem 10.5 solid front disk off my Alfa Romeo spider,and installed 12.19 vented disk on the front. I removed the dust sjeild,as they don't fit. Driving home from work,in the rain, took my exit off freeway, brakes down to get off the offramp

. No brakes, had to ride them to get stopping power back

 Am I right that lacking dust shields the rotors got wet, causing the lack of brakes and definite raise in heart rate?

Yes.

I noticed this effect multiple times, across many different cars.

My VW Quantum got scary in the cold and wet after the brake shields were removed (by lightly pulling).

I have found that "ceramic" brake pads are very bad in the cold/wet no matter if you have the shields in place or not.  I had them on a B12 Nissan and the brakes would literally do nothing when wet until you heated them up.

I've had a mild lack of braking from rain, especially without dust shields (but even with them).  The worst (and I've had this happen with dust shields) is when you're on the highway in snow and slush and haven't used the brakes in an hour or 2.  You go to use them and it takes a couple seconds to break the thin ice film off the pads, rotors, sliders, etc. before you get any meaningful braking. 

Alfaromeoguy said:

In reply to irish44j :

When dry they work great, no power boost, so nice pedal feel and the start stopping at top of travel

ah, no power boost...that may explain it. I mean, wet and cold rotors/pads certainly have way less momentary friction, but with power brakes they would overcome that issue with little notice. Thinking back, I do remember my GT6 not stopping quite as well in the wet. The rally car ('85 bmw) still has its power brakes, which is why wet brakes aren't an issue. 

irish44j said:

Alfaromeoguy said:

In reply to irish44j :

When dry they work great, no power boost, so nice pedal feel and the start stopping at top of travel

ah, no power boost...that may explain it. I mean, wet and cold rotors/pads certainly have way less momentary friction, but with power brakes they would overcome that issue with little notice. Thinking back, I do remember my GT6 not stopping quite as well in the wet. The rally car ('85 bmw) still has its power brakes, which is why wet brakes aren't an issue. 

I invite you to drive my Volvo in the rain.  Whatever pads are on the car DO.  NOT.  WORK.  when it is below about 45F and wet.  Power brakes are still present, and there is even a vacuum pump to ensure that they are always getting assist.  (I have the model with the fancy 330mm rotors and Italian four-piston calipers at every corner, so one can't say that the brakes are undersized...)

This thread reminds me that I really do need to get around to changing the pads.   Dragging the brakes every five minutes got old fast last winter.  Without that, I was counting 10+ very, very long seconds to slow down from 80mph to 60mph with calf-straining pressure on the brake pedal.

The only time ive ever had a performance increase from drilled rotors was on my old Dakota r/t. Damn thing would NOT bite in the rain or snow no matter what until they dried out. Drilled fixed it. Same thing on my v6 dakota. Stock brakes, stock calipers, 4 different types of pads before the drilled rotors. 

So, the answer here is obviously to buy a dakota r/t and put drilled rotors on it.

Dusterbd13-michael said:

The only time ive ever had a performance increase from drilled rotors was on my old Dakota r/t. Damn thing would NOT bite in the rain or snow no matter what until they dried out. Drilled fixed it. Same thing on my v6 dakota. Stock brakes, stock calipers, 4 different types of pads before the drilled rotors. 

So, the answer here is obviously to buy a dakota r/t and put drilled rotors on it.

My Durango was the same way. Drilled rotors changed everything.

Knurled. said:

I have found that "ceramic" brake pads are very bad in the cold/wet no matter if you have the shields in place or not.  I had them on a B12 Nissan and the brakes would literally do nothing when wet until you heated them up.

I agree with this -- some pads do much better when wet than others.  My Miata stock everything had about a half second of no brakes when driving on the freeway in heavy rain, swapping to R4-S pads and simultaneously deleting the dust shields basically removed the issue.

So I'd guess that you probably changed pad compound at the same time as the rotors & calipers, and that's likely responsible for the effect.

In reply to codrus :

That half second seams like a long time, when a car is in front of you..

In reply to Alfaromeoguy :

The world's longest second.

Had the same issue when I changed to a open wheel design on my DD Saturn. Different wheels same brakes, good sec or too before they grabbed. eBay drilled and slots solved the issue

I don't think it's the shields that's the problem. Some OEM's even delete the shields on some models they expect to be tracked more likely then other models.

My 1993 Cobra R came from the factory without any shields and I never had a problem with no brakes in the rain. True it was during  rain races but never an issue of "no brakes".