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This is for a 2018 VW Tiguan Allspace with 49,000 km (34500 miles). Living in a pretty mild climate (ie no snow and no extreme heat), but near the coast. The pad wear light came on and I scheduled the service with the dealer. I got a call later to say that the rotors should be replaced and they always recommend replacing the rotors with the pads because "European Cars use softer metals in their rotors". I would completely agree with replacing the rotors if:

  1. The rotors had scoring, rust etc on their faces
  2. The rotors were warped
  3. The rotors were at minimum thickness.
  4. The rotor on one side was needed replacement (in this case I think you should do both)

I thought that the whole purpose of pads is that they take the bulk of the wear, and then you replace them more frequently than the rotors (and calipers). Theoretically I think it would require less time to replace just pads (seems that way in motor racing). I guess I would expect to replace rotors, which have none of the issues in the above list, maybe every second pad replacement.

We do occasionally tow a 1500kg caravan, but I would expect this to create higher wear on the pads.

If the reason hadn't been "European Cars use softer metals in their rotors", I probably wouldn't be asking questions.

Also, if the rotors have no visible damage, when you replace pads, why would any resurfacing be required. Surely the new pads will bed into the existing rotors after 100km (60 miles) or so.

Appreciate any thoughts.

Cheers

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  • 10
    Some dealers just flat out lie: I took in my Kia Sorento to the Fort Wayne dealer for service unrelated to the engine, and later the service manager came out and told me he found some sludge just inside the oil fill port, and that I should replace the entire engine. There were no symptoms, and no fault codes, just "sludge". XD
    – donjuedo
    Jul 28 at 11:32
  • 3
    My (15 year-old) BMW went to the dealership for a recall on some cabling. When it came back, they had (among other items) listed discs/rotors as eligible for replacement along with pads. Four years, 40k miles and 2 sets of pads later, they're still fine. I trust my indie mechanic so much more than the dealership. They're a bunch of chancers.
    – spender
    Jul 28 at 16:41
  • 1
    For what it’s worth, we’ve noticed both dealerships and other service establishments pushing much more unnecessary or optional work on customers (e.g. alignments on every single car that shows up for service). With people driving less the past 16 months due to the pandemic response they are presumably trying to make it back. Changing the rotors too jacks the bill up significantly without using much more shop time. Jul 28 at 17:57
  • 1
    I've avoided dealers ever since they recommended replacing the entire exhaust system (front to back) by a new one on a 20-year old car that was brought in for a broken muffler...
    – Mast
    Jul 29 at 5:42
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    BTW, any other Brits wondering what 'rotors' are… they're brake disks ;) [I had to google pictures]
    – Tetsujin
    Jul 29 at 16:28
48

You are right to be skeptical, the 'softer metals in european rotors' is complete horsedung. A bit of rust is completely normal, the rest of your criteria for replacing rotors is right on the money, if the dealership is trying to pull that line on you then they are either incompetent or trying to run up your bill.

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  • 2
    Sometimes they imply the extra cost is worth spending on the grounds of safety and "peace of mind" (having just created the doubt in your mind) - typical salesman tricks of the trade. So they are usually careful not to actually lie to you. Basically the front office staff are salesman, not motor engineers. They have a loyal customer base from those who think that all non-franchised agents are "back-street garages" which certainly isn't true (but some are). Jul 28 at 7:02
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    My VW Touran got to 130,000 miles without needing replacement brake discs (rotors).
    – uɐɪ
    Jul 28 at 7:37
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    My old SEAT (VW group) got to 170,000 miles on its original front disks (rotors). The rear ones had needed replacement because I didn't often brake hard enough to "polish" them, and the surface accumulated rust and ultimately became pitted. Anyway, if they are telling you that the state of wear of front and rear disks is the same, that's another reason to know that they are BSing you. The front ones wear faster but stay shiny, and the rear ones will suffer worse from rust.
    – nigel222
    Jul 28 at 12:15
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    As long as you didn't put a nasty body kit on it too @Paul_Pedant.
    – GdD
    Jul 28 at 13:44
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    @GdD Didn't need to. It was made ugly, and dangerous. Vauxhall Carlton 1986 -- front disks not even ventilated. Every component was crap. It was a company car: personally I only buy big old Volvo estates (140, 740, 960 Turbo, V70). Jul 28 at 16:38
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No, rotors can go through 2 or 3 sets of pads.

But if a stone or piece of grit causes scoring then they need replacing. Sometimes resurfacing is sufficient but often the time needed is more than replacing with new.

Also the rotor thickness should be checked - workshop manuals will give the minimum acceptable thickness as well as values for run-out.

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    I'm not sure about VW but many manufacturers have the minimum thickness on the rotors themselves.
    – jwh20
    Jul 27 at 18:23
  • @jwh20 well not seen that on the rotors of my car, but front rotor thickness (new) is 24mm (0.95 in) and discard thickness is 22.2 mm (0.87 in) and that’s from my copy of the workshop manual, I won’t bore you with all the other numbers such as runout and thickness variation...
    – Solar Mike
    Jul 27 at 18:34
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    @jwh20 If they had used other reasonable reason, like min thickness, or warping, or gouging, I would have been ok with it. Just to say its because the rotors are made of a softer metal in European cars, that's crap.
    – speedyps
    Jul 27 at 22:26
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    Ironically, the guy who sold me the car at the dealer, has just responded that 2-3 sets of pads would be what he expects. Disconnect between sales and service there.
    – speedyps
    Jul 27 at 22:27
6

Bull; find a dealer that can make up better stories. Rotors are grey cast iron; now I don't want to lie like your dealer, there may be some nodular or malleable cast iron rotors. It would require laboratory hardness testing to find the small variations that exist among grades. Rotor service is affected mostly by graphite morphology. Interestingly enough, I had "bad" cast iron rotors on my 2004 Nissan Titan (first year). Nissan or Eaton screwed up; Nissan replaced front brakes at no charge. When I pulled a wheel before taking it to the dealer, one rotor had two significant cracks. They kept the old rotors so I could not look at it further. Nissan apparently figured it out as my 2011 Murano has 86,000 on original rotors and pads and they look excellent.

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That's not decided by the dealer, it's decided by the "last turn" figure in the spec on the rotor.

If the machinist determines that turning it down to a clean surface will result in rotor thickness below spec, then the rotor is dead. They try to determine that before turning.

If the rotor is at limits, that means you can use it with 1 more set of pads, and then it's done.

In my observation, the machine work is only becoming more expensive, and for my last 4-5 brake rotor changes, I have found machining cost $15-20 and a new rotor costs $18. Of course that's a domestic econobox. I would expect on European exotica, the machine work would be $15-20 and the part would cost hundreds.

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"Softer metal" is BS, but BMW and VW both recommend replacing the rotors with the pads. The reason is that they often use ceramic pads which are more abrasive so they wear the rotors more. This could make it appear that the rotor metal is softer. Also, modern rotors are not as thick as the older ones, so you would be lucky to have a serviceable rotor after one resurfacing before they are at their service limit. A thinner rotor also makes them more susceptible to warping and causing shuddering when braking which means a customer complaint. Shuddering is also hard on the vehicle. The cost savings is also not that great anymore since fewer places have the brake lathe to resurface the rotors. Where I live (not the USA), a rotor for my work truck costs $150 each and resurfacing is $100 each. I would rather pay the extra $50 and be assured of getting full service life instead of having to do an early brake job.

I have had several VWs and a BMW and have to drive over a steep mountain pass every day, so only get 70k km (43k miles) out of a set of front pads. The rotors are typically about 4mm thinner at that point, so I just replace them. I have done 2 sets of pads with one rotor and even though they were within limits, the rotors warped near the end leading to shuddering, so I had to replace the pads and rotors early.

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    A hybrid would make your brakes last longer. Jul 29 at 11:06
  • Yes, the up-and-over would be ideal for a vehicle with regenerative braking.
    – Eric
    Jul 29 at 11:42
1

As an European owning both European and US car (and having owned a lot of European cars) I can confirm that rotors of either survive 3-5 pad changes before their controlled size (thickness) goes out of spec.

Safety and comfort issues arise even later.

Well, I can only speak myself about older VW models, I personally don't like them and never owned a VW car.

But, I surely would hear the loud swearing from other VW owners (i know a lot of them) about brake maintenance cost being 3x-5x the cost for other cars, including older VW models.


The only reason one may need to replace rotors at their 20-30% wear is a known problem with rotors for this particular car.

This is called a "recall". It is done at the expense of manufacturer and for free in regard to the car owner.

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