[doubleoseven]

Here's a question for you guys: By how much do your tires affect your fuel economy?

This is my problem. I went to the GM dealer to get routine maintenance done 50,000 km (around 20,000 miles). A week afterwards I slapped on a set of BF Goodrich Comp T/A HR4 tires.

I'm now noticing a drastic increase in my fuel consumption and I'm trying to decide if it is the tires or if they messed up something when I was in the shop. :bash:

Why I'm confused is this: The BFGs are a full inch wider than the stock Eagles. Will that amount of extra be enough extra rolling resistance on the tires to be that noticible in my fuel consumption?

I'm running the stock 4.3 V6. I used to be getting over 300 miles to the tank. Now I'm getting over 60 miles less. WTF?

Any thoughts?

 

[MightyMouseJ5]

it isnt so much the width of the tire as much as the aspect ratio. what size tires did you have compared to what you have now?

 

[doubleoseven]

Well the originals were 235/55/16 (if I remember correctly) and now they're 255/50/16.

Thoughts?

 

[MightyMouseJ5]

if i did my math right there is only about a tenth of an inch difference. i dont think that is enough to cause a big difference in fuel economy.

 

[doubleoseven]

no, wait, that does make sense. The tread is slightly wider, but it's the profile of the tires where the added width comes in. The sides balloon out .5" on either side. My buddy and I figured that it could have been an issue of clearance during steering.

Anyways, so bottom line is that the contact area is pretty much the same. So the added tread causing all that fuel loss? Doesn't sound right to me. Sh*t

 

[MightyMouseJ5]

what i meant by a tenth of an inch difference was the tire hieght. i am not sure about the contact patch, it shouldnt make that much of a difference. the taller the tire, the less it has to rotate to cover the length of a mile, while a smaller tire has to spin more to cover the same amount of ground. the faster the tire has to revolve, the faster the engine has to spin causing poor fuel economy.

 

[doubleoseven]

That makes sense too. So therefore if the difference in diameter multiplied by the number of missing miles = approx difference in distance then I'm getting the same mileage. I'll look into this further.

Thanks for your help bro,

~w

 

[96blazer]

Tires could underinflated.

But you woulda noticed that.

 

[doubleoseven]

Agreed, but I'm postive they're at the proper pressure. It's just the design of the tire.

 

[96blazer]

Check your brakes!

On my g/f's Blazer one of the front brakes locked up. It gripped the disc just enough, that it wasn't noticable.. When I had the brakes checked (because it wastime for new ones). They removed the tires, put it in nuetral and the disc would not turn freely. They said it must have been like that for awhile. After it was fixed, I did notice a little better mileage

 

[doubleoseven]

Update: Well I took it back to the garage to have them run it over. I suggested the brakes may be rubbing so that was checked out. As for the new tires, nobody there thinks that they could be the cause. Maybe a little bit, but not a lot.

They ran all the diagnostics on it, checked the computer, pretty much everything and came up with nothing! :bash:

So I'm at a loss as to what to do. I could bring it back for a fuel consumption test but that means going rideless for a few days. (sigh)

Maybe I'll just drive slower. Nah.