On the Mar 23rd, 2013 show, Tom from Indianapolis called in with a broken spring - he later said a brake caliper was broken. Tom questioned the mechanic’s advice to replace BOTH front calipers.
Our friends, Tom and Ray - and I hope this is correct - advised that replacing both SPRINGS was a good idea - that replacing both front calipers was a so-so idea - and that having all 4 tires the same was totally un-necessary. I disagree, and I’d like to start a discussion on these points. Since I brought the subject up, I’ll go first.
I think this is all about balance and risk. I think it is obvious that you’d want the car to be balanced side to side, but I think balance front to rear isn’t emphasized enough. The risk is a vehicle that could go out of control (remembering that the average driver has very few skills to warn him that this is about to happen.)
Tires: I know that there can be a wide range of handling characteristics between tires - to the point where certain combinations make the car tail happy. Not a good situation. I would think that the best advice would include regular tire rotations so the car is balanced front to rear and that tires ought to be replaced in sets of 4. Again, remember we are talking about dispensing advice, not what YOUR personal habits are. I know that I do things that I wouldn’t recommend to others because I don’t think they would pay attention to the warning signs of trouble.
Springs: Obviously if one side is broken, the other is likely to break as well. I think a competent mechanic should advise that both be replaced.
Calipers: Here’s where I disagree with Tom amd Ray the strongest. I think it is very poor advice to question the mechanic’s advice here. First, the mechanic is the only one who has seen the parts. Second, the mechanic is open to legal liability if something goes wrong. I think the only safe thing to do is to replace both.
Do I follow my advice? No. On the other hand, I know the warning signs and am sensitive to them. When I give out advice, I know that the recipient is NOT an expert and is likely to ignore those signs - or worse - mis-interpret them. I don’t want to be responsible for someone else’s tragedy.
Tires: I agree with them. They should match from side to side. Front to back is not nearly as important as long as they’re the same types of tires - - i.e. don’t put winter tires on the front and summer tires on the back and then go charging into a blizzard.
Springs: I agree with Tom and Ray - not because the other side might break, but because springs generally come 2 to a set, and as springs age their springrate can change, which can cause a stance issue as well as uneven handling.
Calipers: I agree with them again (and note that they were very careful to say that the mechanic might have seen something that they don’t know about, however, the mechanic told the caller that you should always replace both calipers, and Tom and Ray correctly said that old saw was bogus). As for mechanic liability - I don’t buy it. What if he replaces the caliper and then the MC fails? Or a line from the MC springs a leak? Or the engine catches fire? Better replace everything to eliminate liability. Better yet, if your car needs anything other than tires, just buy a new car. Point being, there are plenty of parts that are working at the time of inspection that then stop working after inspection. If mechanics were held liable every time that happened, there wouldn’t be any mechanics because they’d all be sued into bankruptcy.
I would like to see some more about SYMMETRY.
My 2004 Suburu Forester recently blew a (right, rear) tire (road debris, the Michelin tires were only about a year old).
Page 11-47 of the owners manual says (in BOLD, WARNING BOX):
“All 4 tires must be the same in terms of manufacturer, brand, construction, degree of wear, speed symbol, load index and size. Mixing tires of different types, sizes, or degrees of wear can result in damage to vehicles power train…Use only radial tires”.
I only replaced the one rear tire. I think the variation between that one and the tires with 1 years wear is minimal, and the cost of replacing all large. With this discussion, I am now uneasy. MORE COMMENTS PLEASE.
A 4WD/AWD vehicle means (simplistically) that all the wheels are connected to each other. If one wheel is spinning faster than all the other wheels because the tire is smaller in diameter because it’s got a year of wear on it, you’re putting strain on the differential, and can eventually break it if you do it long enough.
I have no idea what kind of car was involved in Tom’s call from Indianapolis. I do know that my son had a front spring break on a 1989 Mercury Sable when he was in a remote part of eastern Kentucky. The Ford dealer didn’t have new springs available, but did install a used spring and strut assembly from a salvage yard. He had the car a couple more years and had no problem. Apparently the used spring and strut matched well enough the spring and strut on the other side of the car.
In the old rear wheel drive days we didn’t worry much about matching tires. I had to buy a tire once while I was on the road and bought what was available. The tires, as I remember were Firestone 721 radials and I found a GoodYear store. The mismatched brands didn’t seem to make a difference. This was on my 1978 Oldsmobile. Usually I bought a pair of tires at a time so that the tires weren’t mismatched from side to side, but I often had different brands on the front than on the rear.
Today, with either FWD or AWD, I buy all 4 replacement tires.
I did have a garage put on cheap shock absorbers and charge me for the more expensive shocks. The left shock was noisy, so they gave me a replacement that was the quality I paid for. When I went to replace the shock, I saw that I had been cheated. I replaced the left shock with the better quality, but the car didn’t seem to handle right. I paid for a more expensive matching shock for the right side and the handling was back to normal. I never went back to that shop.
springs yes, calipers no, tires maybe. I like to get all four tires at the same time, but I think a lot depends on a persons driving habits and where they live. I you are the type to push the vehicle to its limits, then yes on all four tires, but if you are a little old lady type driver, then I don’t think it is necessary.
The Subaru manual says that because of the differences in rolling diameter. Those differences can cause excessive slippage of the center coupling and can cause it to fail. These vehicle are known to have this issue. The fact that you haven’t experienced any problems has more to do with luck than anything else.
Ticodean, for about $2 you can purchase a tire depth gauge. This will give you a definitive answer. The maximum difference in tread depth from the most worn to least worn on a Subaru is 2/32".
The fact that it was a rear tire, which wear out much slower than the front means that there probably wasn’t that difference. If it had been a front tire, you may have had a problem, but you might have been able to get away with just buying two tires.
The fronts wear much faster on a vehicle that is FWD or AWD so you should be rotating them on a fixed schedule, or when ever you can measure a difference of 2/32". I prefer to use the gauge and also check the wear patterns on the tires at that time for any alignment issues. If the wear is even and not faster than expected, then leave the alignment alone, but if an odd wear pattern is found, then address it immediately, the payback will come in the form of much longer tire life.