the Hybrid Project

*** THIS IS A LATE POST FROM LAST WEDNESDAY.  SORRY FOR THE CONFUSION. ***

As you all know I am a proud driver of a 2002 Honda Insight Hybrid.  I have to say that it is one of the more interesting vehicles that I have owned and one that turns heads where ever I go.  Today I had to perform a regular duty of getting new tires.  This is something that every car owner must go through and something that people just don’t think about until they get the bill.  

Since most hybrids need a certain kind of tire to operate properly, our choices and price ranges are extremely limited.  So after talking with some people in tires stores, I decided today to replace my worn out stock tires with a slightly different kind of tire.  I went from the stock Bridgestone P165/65R14 to a Pirelli P175/65R14.  Not many of us know the differences between these tires, but if you ask a Honda Rep or any true Hybrid driver, you will get an ear full about what changing the size of your tire will do to your gas mileage.  However, no one can tell you for sure what will happen to your gas mileage if you do change from the stock equipment.  As an engineer and avid Mythbuster Fan, I can’t stand being lead down a path by salesmen without knowing for sure they know what they are talking about.  So I called the only other person I can trust to give me the straight scoop, my Dad.

My Dad is the only other person that I know that has a 2000 Honda Insight and has taken the plunge of switching from stock tires.  He told me emphatically, “DON’T DO IT!”  He noticed an immediate 10 mpg drop over the first couple of days when he switched from his stock tires.  He decided after only 6 months to switch back to the stock tires in order to reclaim his gas mileage.  However, there are some differences between his Insight and mine.  He has a manual transmission and I have an automatic CVT.  This may not seem like a big difference to the casual observer, but most drivers know that you can get better MPG efficiency out of a manual transmission then out of an automatic one.

So this brings us to THE HYBRID PROJECT.  After talking to my lovely wife, I have decided to run an experiment to see exactly how much of a drop in MPG will happen with these new tires.  I have a trip planned to Charleston, SC this weekend to shoot in a competition.  This will give me a great opportunity to run a test on the highway to judge the difference for myself. 

I have two problems facing me:

1) Speedometer and Odometer Offset 

Since the new tires are slightly larger than the stock tires, my speedometer and odometer do not truly depict my speed or mileage.  There is about a 1.6 mph difference the two tires when running at any speed.  This not only makes the car run faster then what the speedometer says, but it also does not track my mileage correctly.  If I decide to keep the tires, I will have to find someone that can recalibrate my computer to register the difference correctly.  Honda already said that they won’t do it.

2) Battery Regeneration

I have already noticed that my battery pack is running lower than usual.  This seems to be the case because I am using more of my electric motor to bring the car up to speed and to keep it there.  Since the stock tires are rated as LRR (Low Rolling Resistance).  It suggests that the car needs less energy to bring the car up to speed and to keep it there.  After my experiment this weekend I should know if this will cause additional strain on my battery pack and electric motor or if it will just work itself out in the wash over time.

If anyone was wondering why I would go to all of this trouble just to change tires, here is a short list of the differences in the tires:

Model:                P165/65R14 (LRR)

Miles:                 40,000 miles

Price/Tire:           $112.5.00/tire (Fully installed with roadside protection.)

Ride Experience:  Rough ride. Extensive road noise.  Ruts and cracks in the road are jarring and feel rough.  Speed bumps and train tracks feel like I am running into a curb.

Model:                P175/65R14

Miles:                  85,000 miles

Price/Tire:           $97.50/tire (Fully installed with roadside protection.)

Ride Experience:  They feel like new sneakers.  Going over speed bumps and train tracks feels great. No jarring when going over cracks and ruts on the road.  This does not make the car run like an Escalade, but does improve the feel of the ride greatly.

I’ll post again with my results from this weekend.  Wish me luck!