Brake Dust Sheilds - In or Out?

[mcgc0]

Thanks to Mr Marshall, I've been pointed in the right direction of an irritating tinny rattle from the rear when on rough road or especially negotiating speed humps - the rear brake dust shields on the inside of the disks. On inspection I can feel them completely loose/disconnected and rattling about.

What to do; some say discarding altogether aids further cooling, any thoughts?

 

[NormalNorm]

Take them off, just a waste of time! I dont think ive seen many people use them.

 

[mcgc0]

Thanks. Checked them out over the weekend, and unless you remove the brake disk there's no way to remove the small 6mm allen screws and nuts holding the sheilds (or did hold until they came away) in place. It's the old tin snips out then...!

 

[iangray100]

Personally, they are there for a reason ..

1) Keeps water off the discs so max pad contact is there in all weathers , even after drving through large puddles
2) Keeps stones and rubbish off the discs
3) Could be seen to channel air to and around the discs
4) The car was type approved with them, so any change no matter how small, but its in a key area of the car ..brakes !, could be seem by an insurance company in the even of an accident as a brake modification.. so perhaps they wouldn't pay out when needed !!
5) etc etc etc

There are quite cheap so why not replace then and keep the car genuine ....

 

[bobster]

After experiencing water drenched pads and discs on a motorway in my old Elise, A scary moment! I made a point of cleaning up and refitting mine after a disc and pad change.
I even considered making some and retrofitting to the Elise. I know some people leave them off, but what price safety!

Totally agree with Ian on that point.

Bob

 

[mcgc0]

Intersting and valid viewspoints.. I know from my Historic rallying days we removed anything around brakes anyway (ease of repair/replacement and cooling).

Just a couple of points; The sheild is behind the disc, so only one side would be more protected from the elements anyway (although this is open to debate) and also they're listed as dust sheilds, presuming their primary requirement is to prevent brake dust blowing up into other areas(?)

Probably will repair or replace though. But as mentioned, complete replacement requires the removal of the discs to access the blind allen screw head of the sheild securing bolt. Which in my case, without braided flexi pipes, means disconnecting the brake pipes and bleeding them again later..

 

[Steve Brookes]

I've removed mine because like yours they were falling off. I was worried they could have caused real damage if they had completely given way whilst driving. However, I think the points other people raise above are good food for thought. In fact, I've noticed that because I track mine quite a bit that the inside pads seem to be overheating more since I removed the shields, which makes me wonder if they also help shield the brakes from exhaust heat? So I'm thinking of putting new shields back on when I change the discs.

Incidentally you should be able to move the calipers away without breaking any lines because the hard line from the caliper to the first coupling can be unclipped from the trailing arm to allow it to be swung free of the discs when changing them.

 

[Alexander_Drobik]

have to say I don't have them - just clogs with muck. no issues with rain etc - a hot spinning brake disc does not hold water - can't see the shield helping there. Ditto as a stone guard. I think there are fitted to keep the wheel clean from brake dust....

 

[iangray100]

As for the comment on hot spinning disc and water ....I hear what your saying but what happens if its not hot and not spinning very fast, and you use your brakes ......it will delay the biting point as the pads then have to push the water away. Same issue on a push bike and the old brake blokes ..you had no brakes .... Same issue on motorbikes ...its one reason for the drilled and slotted discs to allow the water to be pushed out quicker as well as allow the pad gases to escape when they run hot.

They are also there to stop all the road rubbish contaminated the discs and causing excess disc wear.....one reason why Aygo front discs wear at a high rate as due to cost cutting Toyota left off the shields and they now a load of warranty claims . Toyota just confirmed this today when I dropped my Aygo off with a premature clutch issue ..new clutch needed at 24,000Miles...known issue and warranty as well .

Any its your call and my technical opinion and obviously Toyota's opinion, as they left them off as well ....

 

[sawood12]

I don't believe that there are gasses and moisture between the pads and disk. Any water that gets onto the disk in the first place (difficult as the disk is buried inside the wheel) that isn't centrifuged off or evaporated off will be squeegeed off by the pad as the pad runs basically in contact with the disk when the car is running, so very little opportunity for water to get in there in the first place. Drilled disks were first introduced by Porsche to reduce weight and they unexpectidly found there was a benefit in brake performance. This is due to an abrasive shearing action between the hole or slot as they move past the pad carving off small chunks of pad material providing extra resistance - pad wear rates are higher with drilled and slotted disks.

I have never noticed any detriment to brake performance in the wet compared with dry (limits of tyre adhesion put aside) with any car i've had, so this gas/moisture theory it is not an issue in my view.

You shouldn't lose any sleep if you decide to ditch them.

Don't understand how Toyota were suffering with warranty claims for excessive disk wear as car warranties don't include consumable items. Look at the number of Boxster owners complaining about rear disk inner face corrosion (probably due to the presence of the disk shields as the outside faces are unaffected) meaning the disks usually need replacing long before they wear out - and those with drilled disks having to replace disks early due to cracks propogating from the holes. Warranty denied!! A nice little earner for the manufacturers.

 

[mcgc0]

Hmmm... down at Type911 this morning and they looked up Porsche replacements and they reckon they're £33 each!!

I shall this weekend check out the other side, as that shield has completely come away anyway, and if unrepairable they're out.. I think in wet conditions (where we adjust our driving style anyway) the nature of ABS intermittently applying and releasing pressure pretty much 'cleans' the disk surface in milliseconds of any water - if it was there in the first place.

Very interesting re the principle of drilled discs - less about cooling more about a higher friction contact. Better cooling obviously coming from wider vented discs then - a la turbo's or RS.

N.B. Anyone know where I can get a good deal on a carbon fibre strut brace? Found a dirt cheap place in Jo'burg, but they can't ship..

 

[polar964]

If you do end up replacing them i would get them powder coated as well. Just like the tin wear in the engine bay, these parts would appear to be made from the poorest quality steel. I think my dust sheids are worth saving so i'll be getting my coated.