Hey Stoney, give me an email at sasparilla256@hotmail.com I might have a solution for you.

I was always wondering if the tire sizes on the 06 Hybrid Civic and 06 Civic DX were just larger (the tires themselves being bigger in depth between the wheel and the road) than on the LX/EX models to make up for the 1 inch difference in Wheel size.

Scott

 

When I researched this, I found no difference in tire weight between LRR and non-LRR. There can be, however, +/- 1-2 lbs between manufacturers (given same size). TireRack.com and the manufacturer web sites usually have good weight data.

Stock HCH I wheels (14") are 14.2 lbs. A larger 15" would be right around that, if not a tad more. The stock setup for the HCH I with Dunlop SP20s was 31.8 lbs. So a 30 lb setup is really good. Even with my lightweight 15" rims I'm at 29.1 lbs. I'd be somewhat suspicious that a 16" stock wheel and tire would be 30 lbs. 16" lightweight rims are typically 14-15 lbs - that's the $300 "racing" wheels too. I found most tires to be at a minimum 18 lbs, with the larger 205 widths to be more like 21-22. So figure more like 32-37 lbs. However, if you really want to know, you'll have to pull one off and weigh it.

TireRack should have diameter sizes too - or the manufactuer sites definitely will. If you match diameters, you should have no problems with you guages.

 

So the diameter HAS to be the same to keep all gauges true and acurate?

 

I don't pretent to be an expert on this, but here's how I resolved it in my mind.

A new tire will loose diameter as it wears. I figure if the tire looses 1/4" of tread in it's life, that's 1/2" diameter. Clearly cars are all designed to account for some amout of variation in tire diameter without nullifying the guages.

With that in mind, when I shopped for tires I elected to only consider those that were within 1/2" of the OEM tires, figuring that's within a range of variability the car can handle.

Unfortunately I cannot tell you the impacts of being 3/4" or 1" off in diameter, other than my speculation. All tires come with a revolutions per mile measure. 1" off would create a considerable difference in revolutions per mile - I have to believe that has some effect on the FE and MPG guages. How much, I cannot tell you.

TireRack has a lot of white papers - maybe this topic is one of them?

 

Here's a handy link to see what happens when you change tire sizes.

http://marksink.com/tire_wheel_offset/tires.html

 

Yeah Don, please dont use this color it hurst some peoples eyes..!!
Thanks Dude..

Yeah Thats a good question, on the 15 - 17" tires is there a change in MPG's?
Would the speedo have to be recalibrated?

 

That is a handy link there SLEDGE!! Thanks


I inputed the stock HCHII tire size(195/65/15) and then inputed a maximum width of 205, which is what the stock EX 16" is (205/55/16). According to that website...the speedometer would be off by -0.29.

 

I can't tell you about the actual replacement of the tires, but with respect to messing up the speedometer and MPG calculator, I recommend that you go to a web page with a "tire diameter calculator". It will allow to you enter the OEM size of the HCH (get it from your car), and the OEM size of the EX wheels (get it from a 2006 EX with 16" rims).

It will tell you the diameter difference and also the speedometer difference (in percentage).

My hunch is they are very similar.

 

Please remember that you can't assume that the speedometer is accurate to begin with. For years I have been reading Car and Driver and Motor Trend. When they test a vehicle, one of the things they do is to check the calibration of the speedometer at 60 MPH. I have NEVER seen a car that under registers speed. In the vast majority of cases, speedometers are calibrated to OVER REGISTER. This is likely because the manufacturer can't be at fault if you get a speeding ticket. In the vast majority of reviews that I have seen, at 60 MPH indicated, the car is only actually going 58. I have seen as low as 56 and in a few cases, dead on at 60.

For this reason I always calibrate my speedo and odo. The best way is to find a 50 mile stretch on a highway and set cruise to 60mph. As you pass a mile marker, reset your trip odometer and start a stopwatch. Hopefully after 10 miles or so you don't encounter any traffic and can maintain 60 mph. If it takes exactly 10 minutes, your speedo is dead on. Most likely it will take more than 10 minutes. Do the math and you will find your speedo error. But speedo error does not necessarily eqaute to odometer error. Continue for 50 miles and note your trip odometer reading at the 50th mile post. Do the math and you have your odo error. In most cases, you will find that your odometer registers by about 3%. That means that your MPG display is 3% optimistic, as well as your pumped fuel calculations. I always use corrected data for mine. Luckily, for my 2004 Prius, the speedometer and odometer ore almost dead on.

 

I think I am going to do it!!!