Jump to content
SAU Community

Recommended Posts

I've cracked a rear DB4000. Using Ferrodo DS2500 pads.

I was at the track and the only thing apart from running it around there that I can think of as relevant is the fact that I left the track at some speed then sat in the kitty litter for 10 minutes.

Link to comment
https://www.sau.com.au/forums/topic/139840-what-causes-rotors-to-crack/
Share on other sites

I've cracked a rear DB4000. Using Ferrodo DS2500 pads.

I was at the track and the only thing apart from running it around there that I can think of as relevant is the fact that I left the track at some speed then sat in the kitty litter for 10 minutes.

Welcome to my world. My rear rotors cracked on my GT-R. I was only (At the time) using Bendix Ultimates on the rears & was always careful to let the rotors cool properly.

Did the cracks you have in your rotors start from the small return grooves on the outer circumference?

IMHO, the best bet is not to use these rotors...... :)

post-5134-1161561217.jpg

I've cracked a rear DB4000. Using Ferrodo DS2500 pads.

Here's some wild speculation that someone will probably shoot down as BS, but i read somewhere that the thermal conductivity of the pad is an important property in brake operation as it helps even out the temperature on pad and rotor. After frying my front rotors (just warped, no cracks and a blue tinge on the outer of the mating surface) with DS2500's i'm speculating that perhaps they dont conduct heat well and therefore are tougher on rotors than other pads. The outer edge of the rotor gets a lot hotter than the inside edge and the difference in thermal expansion cracks the rotor.

About 4000s - http://www.dba.com.au/DBA4000series_specs.pdf says "motorsport applications and premium street performance" for the slotted (not drilled) rotors, but in the box comes a note "warrantee of DBA product is void when used in any form or motorsport" - tossers! Since they've said motorsport applications, i can see why you cant return them based on the Fair Trading law's requirement that goods are 'fit for purpose'. That law overrules anything the manufacturer says.

Another thing about 4000s - the vane design appears to have been make to look "wikkid" rather than provide optimal cooling...but maybe i'm just bitchy.

Rgs,

Kot

Other then warming up and coolign them down...looks to be a metallurgy thing.

My old DBA 4000s lasted for years, in fact they are still going on a friends car. The 4000s i have now have the same slots as in djr81's photos...and i honestly dont hold out much faith that they will last as well as my old set (Old set had different slots arrangement)

yes vane design i think is another point. I would much prefer a nice, conventional curved vanve rotor to the k-paw DBA style, but finding one for a good price is not easy.

Wonder if the K paw idea is causing these cracks?

If you look down the inside of the rotor you can see a straight path inbetween the K paw sections that joins both sides of the rotor together. Not sure if it would cause the problem but if you add the heat that a good track session will generate this just has to be the weakest section.

If you look at a curved vain type design the vain all over lap so there is none of these straight line oportunites, I did in the end crack my RDA k paw rotors, but only after the worse possible treatment, and they cracked in the straight line area right between any of the k paw connections.

They generally recommend you have a cool down lap to help disipate air through the rotors, and naturally cool them.. instead, you quite *possibly* could have been slamming the hell out of the brakes at the last second and then came to a complete stop and suddenly cooler. So just metal fatigue?

my front rotors have 100000 hairline cracks in them. they going to go bang soon so i gotta do something about them

Try getting the cracks machined out. Even though the material will be thinner, it will be stronger as the stress will be spread out across the surface rather than being concentrated at the head of the crack. That's the theory at least.. (and why slots are curved - no corners for stress to concentrate in).

Edit: Here's what DBA has to say about rotor longetivity http://www.dba.com.au/tech/major_considerations.asp

Rgs,

Kot

Edited by MrKotter

Good old DBA's. I know quite a few people that have cracked DBA rotors.

I did that the above at EC. I came off a pretty heavy session (playing chase car to a MX5) and forgot to do a cool-down lap before bringing it into the pits.

That said, I think it was cracked when I was driving down pit lane to my garage (had a weird pulsing coming through the brake pedal), so parking it without a cool-down lap may not be the cause.

Nope always do 2 cool down laps without touch brakes if i can help it, set the stop watch at the time we leave the garage and start the cool down laps at 15 minutes.

And i have 2 ducts to each front wheel so i know they are getting plenty of air to cool them, i didnt have any brake fade and i didnt feel the pulse from the crack until the next day after getting it home. Still it would have to be stronger with the curved vain design as it would have to crack the vain as well as the rotor which is not the case with the K paw design.

so no one has heard of the dont leave your car in the same spot for longer then a few mins after coming off the track after a race. Need to move the car a few inches forward or back so the heat isnt concentrating on the same spot of the rotor. Id say you came off possibly after breaking or breaking while coming off and then sat in the litter for however long with the breaks stuck on the same spot and it was too much concentrated heat.

Sure, leaving the caliper pistons and pad parked in the same spot of the rotor when they are glowing isnt good. It will liekly warp a rotor, but i cant see it cracking them...as its a localised thing.

Crackign a rotor suggests a metallurgical flaw, or thermal shock and cyclic loads. So it would be more likely the fact that you have stone cold rotors and you roick up to the first 6 corners standing on them rather then bringing them up to temp geradually on your warm up lap as your tyres come into their working temps/pressure.

Likewise, if you come and park it glowing red/smoking then the parked pad may cause the rotor to warp, but crack? Im not sure. Perhaps the differential expansion in the rotor cause the crack, as differential expansion/contraction are a classic for it???

Well I do proper warm ups and proper cool downs.

I think the DS2500's seem to heat the rotors more. I've had people say my front rotors were glowing hot but with 2 track days on these pads and rotors, why aren't the front ones cracked? They would surely get a hell of a lot hotter.

I don't see how you can blame the pads.

Firstly, the metal in the rotor will be massively more conductive than the pad material (Any pad material).

Secondly the amount of heat input into the rotor will be defined by how hard you are braking, not by the pad characteristic.

Lastly, we are talking about rear rotors here. Mine don't usually get hot enough to flash off the high temp thermo paint (The third of the three colours). But they still crack.

And yeah, the DBA (lack of) warranty is piss week. The things are designed for track work but as soon as you get within 100 miles of a circuit the warranty is void. That is not that suprising, but it is still rubbish. I have had to bin rotors with no more than a few tenths of a mm wear. Which pisses me off no end.

Edited by djr81
I don't see how you can blame the pads.

Firstly, the metal in the rotor will be massively more conductive than the pad material (Any pad material).

Cant argue with that.

Secondly the amount of heat input into the rotor will be defined by how hard you are braking, not by the pad characteristic.

If you look at it from an energy perspective, the pad can either transfer the energy into heat or new surface area - ie by wearing out either the rotor or itself. My porsche was roughly equivant to my skyline and never had any brake issues after getting decent fluid and EBC Greens. The GTR is struggling, so next thing i'm trying is the 324mm UAS rotor kit and i'll run some ducting as well. If that doesnt work i'll try the Greens on it.

And yeah, the DBA (lack of) warranty is piss week. The things are designed for track work but as soon as you get within 100 miles of a circuit the warranty is void. That is not that suprising, but it is still rubbish. I have had to bin rotors with no more than a few tenths of a mm wear. Which pisses me off no end.

So what do you reakon is the answer? RDA? Nissan? (is nissan exy?) Upgrade?

Rgs,

Kot

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • My experience with Rising Sun Exports Before agreeing to the sale I tried to do as much research as I could (obviously), his Facebook reviews are 98% and he goes Live at least once or twice a week. I contacted 2 people in the UK who had used him for their imports, both had positive feedback. His explanation and talk through of the import process was thorough, answering any query no matter how stupid it was. It felt as soon as the money was sent, communication dropped off. I asked for shipping updates every 2 weeks or so, not wanting to pester him, he never had any updates. I wasn't informed the car had been dropped off at the port, I only found out by his Facebook story. I asked for the photos taken at the port, knowing he would need some for insurance purposes. I received a few 5 second clips and that's it. When asked again, he said his staff had them. Weeks later I asked again, he tells me he doesn't have any, but does have 50 photos from the original advert. I never received them. I eventually got the documents sent via WhatsApp after I mentioned the port was requesting them. I purchased a CarVX report, to find out the vehicle is a Grade R with recorded accident damage, first recorded in 2017 when it was first auctioned. He never told me the grade, then again I didn't ask. His response was "Grade R means nothing, it wasn't chassis damage". Still, I would have liked to have been informed about it. Jon prides himself on being open and honest when it comes to inspecting cars, it's his main job doing so at the auctions for customers. When the vehicle arrived in the UK I noticed a few little cosmetic issues. It's a 21 year old car so it wasn't going to be mint condition. The side skirts are cracked on each corner and the sealant is failing. The front grill on the bonnet/hood isn't secured very well, mounting studs are missing. Both minor things, but again, it would have been nice to be told. During a Facebook Live walk around video of the vehicle, he mentioned it has a front Whiteline anti roll bar/sway bar. While on the inspection ramp, I noticed the stock item has been installed. When first questioned, his response was "the ARB? Switched? Since when, it never had them". Since sending video and photo evidence I've not received a response. I'm probably being over critical of the overall condition of an old car, but all I wanted was honesty (which he claims to have). I'm aware I wasn't his only customer, he's busy doing XYZ but other reviews praise him for great communication with regular updates and photos, I felt I didn't receive the same treatment. 
    • I was able to get some underside photos while the car was on the ramp The suspension is all Altezza/IS200/IS300 so getting part's will hopefully be less of a headache
    • Welcome to my 2004 Toyota Mark ii IR-V Fortuna (series 2) With a 1JZ-GTE powerplant under the bonnet (hood) it'll give me plenty of scope for power upgrades. For those who aren't familiar with imports, the 1JZ-GTE is a 2.5L 6 cylinder VVTi engine with a single turbocharger. This has the factory R154 5 speed gearbox, along with a aftermarket 2 way LSD differential (brand unknown). Under the arches are a set of CST Zero 1 alloys, 18x9 +30 225/40 up front and 18x9.5 +15 265/35 on the rear. The car was quite low in Japan and there's evidence of the wheels catching the rolled arches/fenders. The tyre's aren't great so I'm in two minds whether to replace both or just the tyres and put up with the wider wheels on the rear. The car still uses stock brakes with the addition of some braided hoses. The exterior is stock with the exception of a BN Sports front bumper and a replacement Fortuna grill  Moving to the interior, the steering wheel has been replaced with a dished MOMO steering wheel (which will get swapped for my Momo Tuner for the time being) Defi Link Gauges are mounted above the climate controls and on the A pillar, the Oil Temp,Oil Pressure,Water Temp and Boost gauges should help with spirited and track driving  The stock seats have been replaced with some retrimmed Recaro bucket seats. Being a larger build these are a little snug, unfortunately the orange isn't for me so I'll look into replacing these down the line. Other modifications include a twin plate clutch, Blitz intercooler, Evolve alloy radiator, a stainless exhaust with decat, HKS EVC-S boost controller and coil overs
    • Apologies for the long read My R34 GTT was up for sale at the beginning of spring due to a few repairs creeping up. The strut tops needed replacing, roof and bonnet (hood) painting (yay for 3 stage pearl) and the underside stripped and treated. I sold the car which allowed me to be in a much better place financially. Leading up to the sale I was already thinking about the replacement. In an ideal world it needed to be a good all-rounder. Something I can mess around with, modify, do track days, do the school run, go on long drives etc.  Options included but not limited to... Laurel C35, Evo 8/9, Civic FD2, Impreza Hawkeye, Aristo and even an Audi S4 Avant (I've already got the Mazda 6 wagon). But there was always one car at the top of the list The Toyota Mark ii JZX110 I found an advert on a Facebook group for an example in Japan, from a seller called Jon at Rising Sun Exports. A few messages back and forth and Jon calls me from Yokohama one morning (or afternoon in his case). He briefly explained the import process, the costs involved and a repeat of the advert. After much deliberation, the price was agreed and the sale was locked in. I've never imported a vehicle so I jumped into the unknown head first. The money transfer was completed through wise.com (fees apply), very easy to use and the money was with him within a day or two.  The car suspension was raised for the vessel and the car dropped off at the port. It was 7 weeks later when the bill of lading was received and the freight invoice sent to me, followed by the export certificate a couple of days after (both digital copies) In the mean time the port had been in contact. I needed an agent to deal with the NOVA (notification of vehicle arrival) along with the tax/duty invoice, this was £75.00. The port also had a fee of £100, I'm guessing to cover the cost of the 10 day 'free storage' and for moving the car off the boat etc. They need a copy of the vehicle invoice, freight invoice and export certificate to allow the vehicle to pass through customs. The vessel arrived on Tuesday 5th August, the tax/duty invoice was generated and sent over. This is generally tax 20% and duty 10% of the vehicle value. Although the invoice came in at a higher amount than I had calculated. Once HMRC had received the payment the vehicle could be released from customs. I thought once the tax/duty was paid you could collect at any point, that's not the case. Your agent will need to book a collection slot, I requested Thursday 7th which was accepted, with a 9:00am slot allocated. It was a 5:00am start from Norfolk heading to Southampton. We eventually found the compound, upon presenting the bill of lading and some ID they released the car (they drove it out of the compound to the front ready for us to load up). The email from the port stated each slot had a 10 minute window, which seemed abit farfetched but the staff said it's not a strict rule. We were there for approx. 30-40 mins in total. A week prior to collecting I contacted my garage and explained the situation, I was able to get an inspection slot that afternoon. For the registration, DVLA require the car to be insured, for this I used a company called Adrian Flux who can insure the vehicle using the VIN number. 
    • Hey guys, looking for these side skirts if anyone can help me out. 
×
×
  • Create New...