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The Passing Lane Newsletter - January 2011

Page 3: Tech Tip:FAQ's, Stock Replacement Rotors by Zimmerman

Orders placed through our website will automatically receive any discount pricing associated with this promotion.
If you call to place your order, please be sure to mention media code "MN" to ensure that the correct sales pricing is applied to your phone order.

Sale pricing valid from Wednesday, January 06, 2010 through Sunday, February 28, 2010


Do I need to change the rotors when I change the pads?The short answer is probably yes, but there are a lot of different factors that contribute to this.

In the good old days, brake rotors were giant blocks of steel alloy that would last the life of the vehicle. With an eye towards improving ride quality and un-sprung weight the manufacturers have gradually made the rotors lighter and thinner. If you got a good long run out of your previous set of brake pads, there is a pretty good chance that your rotors are now approaching minimum thickness. If they have not reached minimum yet, it is almost certain that they will before you get through another set of pads. It’s usually stamped in the edge of the rotor or you can find it elsewhere. Rotors below minimum thickness are dangerous for multiple reasons including the overextension of the pistons in the calipers and potential fluid leakage.

The surface of the rotor conforms to the shape of the old pads. Sometimes this is visible and the old rotor looks like a grooved record. You can also feel the ridge on the outside edge of the disc. If you put new (flat) pads on this old rotor, the pad surface will not fully contact the disc surface resulting in a smaller effective braking surface and less overall braking available and noise issues. Rotors always have a concave wear surface in the swept area. You can turn/grind the rotors flat again but this will frequently take you too close to the feared “minimum thickness” and can be like throwing money in a hole.

If you do install new pads on old rotors, how long will this last before the rotors give you issues? If you balance out the cost of the machining and the pads that you used it may be a false economy.

Do I need to change the pads when I change the rotors?The pad surface did conform to the surface of the old rotor. If there was an actual reason to replace the previous rotor, it is hard to imagine a situation that would not be reflected in the same problems on the pad surface. We’re not talking about contamination here, but simply the need to get the full surface of the pad in contact with the rotor surface. Mismatched surfaces will cause poor braking and noise.

Do I need to clean my rotors first?All new rotors have some form of machining residue or rust protection on them when you take them out of the box. If there was no residue, the rotor would begin to rust within hours of manufacture. Most rotors will have instructions in the box describing the coating and the procedure, if needed, for removing the residue/coating. If you are not sure, clean the braking surface anyway to avoid pad contamination. You can use specific brake cleaner or acetone. Remember that if you clean the rest of the rotor it will simply accelerate the rust process. This doesn’t really cause any concern, but some people find it very annoying.

If you are using old rotors, you should scuff up and clean the surface with medium grit sandpaper. If you don’t, the new pads will have a hard time bedding in.

Do I need to break in my brakes?Yes. But this is not nearly as complicated as most people think. Usually a few long medium-hard brake applications without completely stopping will do the trick. Just make sure that you don’t try this out in traffic.

Why do my rotors warp?Well, the truth is that they probably don’t. Old school solid rotors can warp, but the vents in the middle of most modern rotors give a degree of rigidity that is pretty impressive. Rotors like that just can’t warp. Next time a mechanic tells you that your brakes are warped, ask him to show you the actual deformation on a lathe. You will most likely find that the run-out is within factory specs.

Why do my brakes shimmy?Different alloys wear at different rates. Brake rotor manufacturers try to make sure that the alloy of your rotor is exactly the same all the way round. Sometimes you will see a rotor that has part of the surface showing more wear than the rest. This seems impossible on first thought, but it’s actually pretty common. This will feel like warpage but it really isn’t. If you buy name brand product, this should not happen to you. Buyer beware.

Brake pads come recommended for different heat ranges of optimum operation. If you drastically exceed the heat range of your pads, they can actually melt a bit. It is possible to have a few thousandths thickness of melted pad stuck to part of the surface of your rotors. This will give part of the rotor a different level of friction than the rest. This will also feel like warpage, but it’s not. Sometimes you can scrub this off by going through a break-in procedure.

Stock Replacement Rotors by Zimmerman

These high-quality German-made rotors by Zimmerman are an excellent alternative to stock OE rotors. Generally shipped with a protective shipping coating. Don’t forget to use a good Brake Cleaner to remove this transit film prior to installing them on your car. As with most Volvos, it is strongly recommended that you MEASURE the SIZE of your rotors before placing your order. Sold as each.
850 (4 lug) 1993 only Front rotor
850 (4 lug) 1993 only Rear rotor
850, 70 series (11” diameter) 1994-2000 Front rotor(1)
850, 70 series except AWD 1994-2000 Rear rotor
C70 (11” diameter) 1998-2000 Front rotor(1)
BAD PART NUMBERC70 (11-7/8” diameter) 1998-2005 Front rotor(1)
C70 1998-2005 Rear rotor
S/V70 (11-7/8” diameter) 1998-2000 Front rotor
70 series AWD 1998-2000 Rear rotor(2)
S40, V40 2000-2004 Front rotor
S40, V40 2000-2004 Rear rotor
S60, V70 (11.1/4” diameter) 2001-2007 Front rotor(3)
S60, V70, S80 (11-7/8” dia) 2001-2007 Front rotor(3)
S60, V70, S80 (not AWD) 2001-2007 Rear rotor(3)
(1) Most 1999-2000 70 series are equipped with 11” front rotors. Some have 11-7/8” rotors. Be sure to measure before ordering.(2) Fits up to the following chassis numbers:V70 AWD up to #587425, V70 AWD XC up to #587441, V70 AWD R up to #587596 (not for 2000R)(3) Not available for S60R and V70R

Sale pricing valid from Wednesday, January 06, 2010 through Sunday, February 28, 2010

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