[swedishandgerman]

On the back of each hub carrier and between the drivesahft rubber belows (CV Joint boots) is a toothed wheel that gets full up with dust from the brakes, mud flicked up from the road and possibly mank after you've washed your wheels as above. They also deteriorate with corrosion and get flaky. At worst, they corrode so badly they break up. They're the ABS rings

It's a bit of a fiddly job to clean them up, but if bad, most certainly make the ABS ultra sensitive, make the cruise control erratic and/or make the ABS light come on

Mine were so bad they were broken up and my extremely superb and friendly Volvo workshop replaced for £108 labour plus parts. I bought genuine ABS rings (£31.50 ea) and driveshaft bolts £2.30 each). My CV Joint boots were looking poor so they changed those too. I refused to pay £45 for each genuine CV joint boot and paid £10 for non-genuine ones.

At that price and for the risk of pulling my driveshafts apart, it wasn't worth getting my hands dirty!