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Discussion Starter #1
Hi all. I want to change the front discs even though they passed the MOT as they are developing a lip. However I can't get the countersunk screws that hold the discs out. I've tried an impact wrench and an electric impact driver to no avail. They aren't left hand thread are they?
 

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I doubt they are LH thread CM,they were probably fitted without any anti sieze grease (copper grease).
If the screws are a problem I usually spray them with plus gas or similar a couple of times,leave that to soak in a little,then get the biggest screwdriver or socket bit that fits snugly in the screwhead and then use a metal bar against a fulcrum to maintain inwards pressure on the end of screwdriver/bit whilst 'twitching' the bit slightly to try to rotate the screw.
If all else fails you could carefully drill the head off the screw and then remove the remains after the disc is clear,you can get LH drills which is sometimes sufficient to shift a recalcitrant screw.

rgds max
 
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RH thread give a soak as above an a good wack with hammer and impact driver. Probably never been off. I had my own Sorento from new and kept for over 10 years and they never needed changing.
 

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Are you sure you need to change them? It used to be a common way to generate extra business by remarking that "yer discs are lipped" - just about all discs develop a lip as they wear because the pads do not go all the way to the edge. Can you measure the remaining thickness on the discs? the disc should have it's minimum thickness stamped somewhere on it

If you still want to get them off then the application of some heat might help. Discs get very hot in use so unless you get the whole thing cherry red you will not damage them - while they are hot applying some penetrating oil (NOT WD40!) will help it to soak in and then a good whack or three with an impact driver. Sometimes it helps to try to tighten them first.
 

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I guess you tested the impact driver to ensure its not jammed.

Even if the disks are just liped it could be nice to grind the lips off, some lips grow in size and chaff on something after a while.
 

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Changed my rear disc and pads recently on my Venga and wanted to change the screws to stainless steel and with allen key tightening so used this guy on ebay..used him before and found his service good..

 

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Discussion Starter #7
The garage said they did not need changing for another year and I trust them. The discs do look a little worn though and the car is 14 years old. I've already bought the discs and pads so I might as well do the work.
Yes I tested the impact driver. It's only been used a couple of times.
 

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The garage said they did not need changing for another year and I trust them. The discs do look a little worn though and the car is 14 years old. I've already bought the discs and pads so I might as well do the work.
Yes I tested the impact driver. It's only been used a couple of times.
Hi all. I want to change the front discs even though they passed the MOT as they are developing a lip. However I can't get the countersunk screws that hold the discs out. I've tried an impact wrench and an electric impact driver to no avail. They aren't left hand thread are they?
I have used the impact driver before and they undo if you have a gas blow torch and heat the screw head then try undoing it the heat should expand the screw enough to unscrew it good luck.
 

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Thanks for the heads up crickley mal, I'll try and remember to give mine some lube when next swapping to winter wheels.
 

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There is a school of thought that the disc retention screws are not necessary
The discussion is that they are really only needed to stop the discs falling off the production line before the calipers are fitted.
Not sure how true this is but my car before the current Venga had a disc swap and screws were not replaced and it did 25K like that so maybe it is true.Certainly didn't cause any issues for me anyway.
Not to be confused with drum retention screws which can be needed as if the drum rusts to the wheel and you take the wheel off and the drums aren't adjusted properly, you could theoretically end up pulling the drum off with a wheel (ie: tyre change time / puncture etc)
 

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There is a school of thought that the disc retention screws are not necessary
The discussion is that they are really only needed to stop the discs falling off the production line before the calipers are fitted.
Not sure how true this is but my car before the current Venga had a disc swap and screws were not replaced and it did 25K like that so maybe it is true.Certainly didn't cause any issues for me anyway.
Not to be confused with drum retention screws which can be needed as if the drum rusts to the wheel and you take the wheel off and the drums aren't adjusted properly, you could theoretically end up pulling the drum off with a wheel (ie: tyre change time / puncture etc)
I have had that thought too,. The wheel nuts hold it all together when the wheel is on the car so the screws do seem superfluous.
 

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The screws are not necessary for safety but they do stop the disc moving (say) when you change pads or remove the caliper etc.
 

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When you're changing discs now, the special ceramic grease should be used sparingly on the face of the cleaned hub and on the thread of that retaining screw....you never know the next person to change them will appreciate you doing it properly....and it could be you!
 

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Some aftermarket discs I've changed haven't even had the screw holes, so the screws weren't re- installed.

I installed "coated" discs at the front a few years back, and they still haven't rusted, they are missing holes for the retainer screws. They are always loose on the hub when I change wheels.
It would be nice if they had rusted enough to hold them in place.

For anyone preparing their car for a nationwide lock down of several weeks or more, I would recommend coated disks.
The rear discs on the Kia are quite visible, they would have looked pretty ugly if they had been rusted and not coated.
 

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These are really nice to work with...or local motorfactors has changed supplier from mintex to these;

 

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the securing screws are required because without them the disc can ease out slightly when the wheel is removed, this then can cause particles of rust to drop down between the disc and the drive flange causing brake judder.
 

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The same size car from Toyota has M8, the heads look the same.
If you can zoom in on a picture of a disk, you can probably scale it off your computer screen.
Come to think of it, ATE have drawings of their products available with all the dimensions, brembo too and maybe textar.
 

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they are usually m8x1.5, to get them loose you need to have a socket type fitting so that you can hit it hard enough to loosen the thread
 
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