[cfm56d7b]

Originally Posted by casualDIYer

I've heard this as well but it seems the car manufactures have a much different approach. If a shock absorber fails under warranty, the manufacturer does not replace any non-broken shocks. They replace only the broken one. The same goes for brake calipers, control arms, sway bar end links, tie rods, spark plugs, fuel injectors, headlights, tail lights, etc. It would be literally impossible for any two parts on a car to perform identically after they go into extended use. Parts are considered 'working' if they fall into a range of acceptable performance. Once a part falls out of that range, the part is considered 'defective'. 'Feels the same' isn't an objective measure of performance.

Consider this, a car starts off with 4 new shocks at the factory. Customer gets car, then hits a pot hole 3 weeks later. Does the customer now back up and drive each wheel into the pot hole, at the same speed, to make sure all 4 shocks are the same? Does the customer count the number of left and right turns to make sure each side of the car is used equally? Do customers commit to never gaining or losing weight and have a strict rule that passengers must weigh the same as they? After years of use, none of the 4 is going be identical, but the performance of the 4 should fall within an acceptable range.

As an owner, I don't care whether one or two or 4 shocks are replaced in a warranty repair. I just want the car to return to acceptable use. If one shock is swapped and the car now leans heavily to one side, that's not acceptable repair and the maker has to rectify that. So, the maker of the car is interested in parts that maintain a level of acceptable performance during the warranty period to avoid excessive replacement cost.

I believe the 'replacement the pair' idea comes from idea that if one is broken the other may break soon so why not save yourself additional labour cost and hassle and perform preventative maintenance now. If one were to argue for identical performance, I'd say swap all 4 then. Don't front and back need balance too?

Adding to the discussion.

Every vehicle component subject to continuous wear-and-tear has a useful lifespan which depends on road conditions and driving style.

If the punctured left rear tire has to be replaced, it might sense to replace both tires if the tread on the right rear tire is close to the end of its useful lifespan.

For tires, the decision whether to replace in pairs is more straightforward.

For struts, it's a bit more difficult because the useful lifespan can vary greatly.

If one of the struts failed at 10K miles, I would replace one strut.

If one of the struts failed at 70K miles, I would replace all four struts. My own opinion only - not a recommendation.

There are no fixed rules in this case. Only the owner's perspective matters on the value of spending more money to avoid multiple service visits later. Time is after all money.

[Tommi_Mav]

Warranty replacement is a completely different thing. No dealership will replace you nothing else than what is defect. But IMHO shocks cannot be treated the way e.g. lights are.
Of course, it's a different thing if one shock is broken after 5K miles, 25K miles or 70K miles. Personally, if one shock was broken after 20-25K miles, even if it was replaced under warranty, I would ask to replace at least the other one in the same axle too. That would result in a more uniform behaviour by the car. If it was broken after 5K miles, then ok, I would replace only the broken one, since there's no significant wear on the reamining shock.
There are shops where you can measure the wear and responsiveness of each shock (while on the car). I wouldn't be happy to have a completely new 100% performing shock on one wheel and a 60% performing shock (which is still acceptable and doesn't need replacement) on the other wheel. So, the most economical solution is to replace both shocks on the same axle, if not all of them.

Bottom line is that what each owner does, relies truely on his/her perspective on things, as cfm56d7b states.

[Randy Johnson]

Originally Posted by Jvac

I never heard of replacing springs as a wear item until I joined this forum. I wonder if we all just over-maintain our cars or there's something unique to the bmw that I haven't discovered yet.

There is something unique to BMW: They fall apart after the warranty expires!!!

[casualDIYer]

Originally Posted by Jvac

I never heard of replacing springs as a wear item until I joined this forum. I wonder if we all just over-maintain our cars or there's something unique to the bmw that I haven't discovered yet.

The issue with springs is they are paired to dampers. Unless you are going BMW OE, any other damper will have a different compression/rebound rate compared to the BMW OE. Is the difference significant? Depends on what damper you choose.

[Jvac]

Originally Posted by casualDIYer

The issue with springs is they are paired to dampers. Unless you are going BMW OE, any other damper will have a different compression/rebound rate compared to the BMW OE. Is the difference significant? Depends on what damper you choose.

I'm with you on that, but I was referring to the posts about replacing springs because they have 60k or more miles on them. In all the years of owning cars I've never even had a shady mechanic try to sell me new springs because they were worn. It wasn't until I read threads like this that I heard people suggest new springs because they are cheap parts. I really don't think that's necessary unless they're damaged or you fit different shocks that are poorly matched with oem springs.

[casualDIYer]

Originally Posted by Jvac

I'm with you on that, but I was referring to the posts about replacing springs because they have 60k or more miles on them. In all the years of owning cars I've never even had a shady mechanic try to sell me new springs because they were worn. It wasn't until I read threads like this that I heard people suggest new springs because they are cheap parts. I really don't think that's necessary unless they're damaged or you fit different shocks that are poorly matched with oem springs.

I agree. A worn spring at 60k miles / 100k km would be exceptionally rare. Maybe if you had an SUV or other type of truck and hauled a lot of stuff and had issues with rust, I could see broken spring (saw one on a Tiguan, among one of the finest Mexican made autos one can buy). If anything were to be replaced at that mileage, at best I'd expect a refresh of the rubber pads and that would be mainly to get rid of squeak as opposed to disintegration of the part itself. Maybe some thought replacing the spring was a solution to replacing the pads that support the spring?