Bumps in the Road

The other day I got a phone call from a friend with a concern about his Subaru Legacy GT Spec B.  I had helped him improve the handling with some better springs, Whiteline roll center correction kit, and some nice anti-roll bars and end links.  We were both very happy with the results and he had put a few thousand miles on the car since the work had been done.  Now he was concerned because, under specific conditions, the suspension would react with a bang instead of its normal smooth ride.

We talked about the problem over the phone and arraigned for him to bring it by so we could take it out for a test drive and see what was going on.  The day came and he showed up.  He explained that it was most prevalent when he crossed on an overpass and the suspension hit the expansion joint at either end of the bridge.  I took the car out to a shopping area that had some pretty rough perimeter roads.  Sure enough, when an abrupt bump was crossed the suspension would react with a bang.  Then we drove to an overpass that we knew would provide the same situation.  On the way I took the car through its paces to see if it had any other suspension ills.  I was suspecting an errant end link or perhaps a loose nut on a strut.  In spirited maneuvers the car worked very well and behaved as it should with no noise or bad manners, but when we tried the overpass the sound was abrupt and jarring.

It was time to talk to the owner about the problem.  When trying to determine the source of difficult problem it is important to ask some key questions.  My questions centered on how the problem appeared.  Did it happen all of the sudden?  Did it start small and work its way up to the level it was now at?  What changes might have occurred at the same time?

I light bulb went off in my friends head as I went through the questions.  He suddenly realized that it started right after he purchased new tires. 

I remembered he and I had talked about what kind of replacements he should consider and I felt that he should stay with the brand that the car came with, Bridgestone, since his experience had been excellent with them.  We both agreed that it might be the time to just step up to a little more of a performance level and change to the Potenza 760 version. 

Now we had discovered that while the 760’s certainly provided additional grip and were compatible in most driving situations, the sidewall stiffness was totally incompatible with his suspension in that one driving situation.  So it was back to the tire dealer who was good enough to have Bridgestone pro-rate the wear and exchange the tires out for the original 050 version that his car came with.

This is a great illustration of how tires and suspensions can have incompatibilities in one situation and not in another.  A tire that is a real performer on one make and model of a car could turn out to be a gremlin for another.  You see it race cars all the time where the cars are literally designed around the tires and if the team switches to another brand during the season they often have to start completely reengineering the car and suspension.

I have seen some tires that are really great on most cars, yet cause problems like pulling to one side or another because of a difference in the cars’ differentials.  It is important not to forget that tires are sophisticated creations that are an integral part of a car’s suspension and therefore can either live in harmony or in conflict.  As you upgrade to some of the more performance versions of even the most reliable brands you might just find out what my friend did.

So my advice is to do your research.  I personally find that Tire Rack provides a lot of valuable feedback from customers and their own tire testing.  If you read through their customer comments be sure to focus in on the people with a vehicle like your own.  If you have an independent tire installer in your area you might also ask them what they have seen.  After all, they have mounted and balanced hundreds if not thousands of sets of tires and have seen which ones are difficult to balance and true up and those brands that have consistent quality.

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This entry was posted in Automobiles, Car Stuff, Care and Feeding, Cars, Servicing Cars, Sports Cars, Suspensions, tires. Bookmark the permalink.

4 Responses to Bumps in the Road

  1. Jim says:

    I really like Tire Rack and buy all my tires there. It doesn’t hurt that South Bend is my hometown, either. I drive up (from Indy) and have my tires installed in their facility there.

    I’ve had two Toyota Matrixes, the first a 2003 base and now a 2003 XRS. I liked the last set of tires I put on my base Matrix so much that when it was time to reshoe my XRS I put those same tires on. The two cars have the same suspension, but the base had 15″ wheels while the XRS has 16″ wheels. I like these tires on my XRS less than I did on my base. The front end is just less sure on uneven pavement. I’m not aware of issues with the suspension and all I can figure is that the larger tires are just a little different than the smaller ones on my old car.

  2. Noel says:

    Good comments on tires, Jim. Tire Rack has terrific info, but it’s important to read the details. The tests are useful but I think you have to read between the lines in the reviews from customers. A few thoughts that have worked for me.

    > Look for reports that list a good number of miles, like over 5,000. Many people comment on tires when they are new or relatively few miles on them, so you don’t get a real sense of how the tires work.

    > Look for reports from people who have a car similar to yours. What a guy in a RWD Mustang thinks of a tire doesn’t help a lot if you have an AWD Audi, Mitsu or Suby, or a tweaked FWD car.

    > Geography matters. The experiences of someone who lives in a world of smooth roads and moderate temperatures are different than those of someone like me who lives where there are four distinct seasons and the roads have divots, frost heaves, potholes and randomly patched surfaces.

    > Pay less attention to comments from people who don’t spell correctly or don’t write clearly.

    Beyond Tire Rack, see what people who have cars like yours recommend. For my Saabs, for instance, I get great info from a couple of Saab-related web forums, as tires are a common topic.

    When buying, price shop. Tire Rack has great prices but I find my local indy shop can come very close once you factor in mount & balance, free rotations, and free flat repair. And if there’s an issue he can deal with it right away.

  3. jimsgarage says:

    Great list of advice steps there Noel. I tend to go to Tire Rack since I worked at a Tire Rack installer for the past three years and found it was a good way to quickly check out what choices there were. Tire Rack does not carry all brands either so it is important to check out other sources.
    All your points are well taken.

  4. Noel says:

    Thanks, Jim. The other thing is that because of their relationship with BMW, Tire Rack does most of their tests driving BMWs. Bimmers handle better than many other cars, and are RWD, so how a tire performs on one doesn’t necessarily reflect how it will work on, say, a FWD Altima or Mazda 6. The overall tire characteristics will remain the same, but as you noted in the original post, not all tires work the same way on all cars.

    That said, Tire Rack’s recommendations and reviews were pretty much right regarding the RE960AS W-rated tires I put on my Saab Aero. And I wrote my own review on them after some miles built up.

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