Ian Comerford Posted February 5 Posted February 5 Can anyone please tell me the thickness of front and rear 3.2 discs when new and also what the wear limit is, ie at what thickness should you replace them? Thank you
World Citizen Posted February 5 Posted February 5 https://www.impactbumpers.com/forum/index.php?/topic/38061-minimum-brake-disc-thickness/
Ian Comerford Posted February 6 Author Posted February 6 The reason for the question was that whilst my car was in Greatworth Classics this week (for tappets and RSR rocker shaft seals) they mentioned that I should consider fitting new discs this year. Checking my records I last replaced these when fitting 3.2 calipers in June 2008, 16.5 years and 65k miles ago. Pretty good all in all. So the next question is… with which discs do I replace them? I recall these are Zimmerman which were half the price of OPC discs at the time and regarded as nearly as good. Thoughts, opinions, facts etc appreciated. Also has anyone fitted drilled or slotted discs and really noticed a difference. Thank you
Ian Comerford Posted February 6 Author Posted February 6 I also noticed that they were £76. + VAT at the time so not everything has hugely increased in price as we generally think.
Nige Posted February 6 Posted February 6 (edited) I think after 16 years and 65k miles they've done pretty well even if they are still in spec. For £75 each just replace them, Zimmerman are fine Ian. Pagid are also good, Brembo, etc. Have you checked ECP, CarParts4Less, GSF, etc? I've never been bothered about cross drilled, my experience is that the holes fill up with dust, crud and rust and can crack between them over time. So probably won't last another 16 years. Edited February 6 by Nige 1
Ian Comerford Posted February 6 Author Posted February 6 Thanks Nige, appreciated. If I could buy the same again I would, for obvious reasons. But I’m not very heavy on brakes so they will last won't they. I forgot to add a thumbs up for Greatworth Classics, they seem like nice people doing a good job. They must be doing something right given the variety/number of cars in there too.
Strictly Posted February 6 Posted February 6 For brake disc jobs get one of these, I've not actually tried it on an air cooled 911 yet, but it should work fine...but maybe do some measurements first just in case If you don't know why...hubs where the discs bolt to must be clean, if not then the disc will instantly have runout and will develop brake judder. My maserati granturismo discs are £1000 a pair. Insert the word surgically in this case Although the picture below shows the hub to wheel face my comments above are relating to the disc to hub face, obviously do both. https://www.ebay.co.uk/itm/235936117973?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=40-spqRVRwi&sssrc=4429486&ssuid=0evmTIHMR0G&var=&widget_ver=artemis&media=COPY
Ian Comerford Posted February 6 Author Posted February 6 Thank you for this, good advice about the runout. I’ll also check it once the new ones are assembled.
World Citizen Posted February 7 Posted February 7 Light smear of Copperslip around the annulus and on the flange stops your hub getting seized in the holes Follow me at #sendit for more top tips 👌 1
proporsche Posted February 7 Posted February 7 On 05/02/2025 at 23:14, Ian Comerford said: Can anyone please tell me the thickness of front and rear 3.2 discs when new and also what the wear limit is, ie at what thickness should you replace them? Thank you it is usually written on the disc-on the edge..
Ian Comerford Posted February 7 Author Posted February 7 Just now, proporsche said: it is usually written on the disc-on the edge.. Thank you, they are a bit rusty after 16 years but I’ve got the figure from a previous reply. Appreciate your response
World Citizen Posted February 7 Posted February 7 On 06/02/2025 at 08:19, Ian Comerford said: Also has anyone fitted drilled or slotted discs and really noticed a difference. Thank you Not sure these slotted discs are something I'd fit to my car 🤔 But I wouldn't have any worries about fitting slotted discs with a less offensive groove pattern to my car Just bought front crossed drilled discs for my FJ from Autodoc to go with some new 6 pot Alcon calipers, can't go wrong with Brembo's IMHO Check out Autodoc, they should have a good range of makes for your car and give you size info/engineering drawings too
Chris_911 Posted February 8 Posted February 8 Brembo quality is not what it was. I fitted a set of Brembo discs to my wife's BMW F11 - had a recurring pulsing pedal ever since. Never had a problem with OE discs.
Strictly Posted February 8 Posted February 8 (edited) 12 minutes ago, Chris_911 said: Brembo quality is not what it was. I fitted a set of Brembo discs to my wife's BMW F11 - had a recurring pulsing pedal ever since. Never had a problem with OE discs. You sure it wasn't brake judder caused by dirt between the disc and the hub? That sounds like what happened. This is why I explained the above. I currently have 3 pairs of brembos fitted and do not have this problem Edited February 8 by Strictly
Strictly Posted February 8 Posted February 8 P.s on some of my old cars I have fitted any quality discs, I'm talking GSF £25 a pair jobbies! I have never had brake judder (pulsing pedal)...but i have always made sure the disc to hub mating face it totally clean which us where the run out starts. How you clean it is up to you. I have only recently splurged £16 on a tool that is supposed to do it, see my post above. As I said I've not tried it yet on an aircooled 911....but if you work on your other cars it will save doing it by hand 1
Ian Comerford Posted February 8 Author Posted February 8 Interesting, thank you. I think I am going to find another set of what I have been using happily for 16 years or so, another set of Zimmermans
Ian Comerford Posted February 16 Author Posted February 16 Interesting morning. I finally got around to measuring the disc thicknesses and the results are a bit of an eye opener. RL 23.114mm RR 23.076 FL 23.03 FR 23.012 Bear in mind the discs have dine the same mileage at 65k miles Strangely there isn’t much difference between front and rear, which isn’t what I expected. I’ve mentioned a guy called Bill Verburg on Pelican Parts before who is a respected brake guy. He has reams of data, fact on pretty much every brake option for our cars. His data suggests that fitting a full set of 3.2 brakes to an SC creates an imbalance, he says you should only fit fronts. I wonder if this is what I’m seeing in real life ie the brake effort is more on the rears than would be the case with SC rears fitted, hence the relatively even wear front to rear? So, no need for new discs yet. Thanks for all of your input though, it's appreciated.
World Citizen Posted February 16 Posted February 16 Was just trying to snap you back into the real world 😉 Was worried you were having an OCD seizure 🥴 Didn't mean to offend 😬
Ian Comerford Posted February 16 Author Posted February 16 54 minutes ago, World Citizen said: Was just trying to snap you back into the real world 😉 Was worried you were having an OCD seizure 🥴 Didn't mean to offend 😬 Ok, what you are really trying to say is that you’re as interested as I am in the fact that my front and rear discs have nearly the same wear after 16 years and 65 k miles……..
Northy Posted February 17 Posted February 17 That’s is interesting. I’d have assumed you ideally want more front bias. Under heavy breaking you don’t want the rears locking up first. Are you running the sC proportioning valve?
Beaky Posted February 17 Posted February 17 (edited) On 07/02/2025 at 13:24, World Citizen said: Are these not the Dogs b*ll*cks.....................lol On 06/02/2025 at 08:19, Ian Comerford said: Also has anyone fitted drilled or slotted discs and really noticed a difference. Thank you When I upgraded to Carbon 12's the front and rear discs were slotted, not had any issue, nor brake fade on the few tracks day I've done Edited February 17 by Beaky
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