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Bill in Houston 05-23-2007 08:27 AM

Old Tires, Higher RR?
 
I am currently driving on my 3.5 year old OEM tires with 40000 miles on them. They are not down to the wear bars, but are lower than I like to go. I have been putting off getting new tires because I am concerned that new tires will make my gas mileage drop due to the greater tread depth of new tires. BUT, I am wondering if it is possible/ probable/ likely that somehow the old tires have gotten stiffer as they have aged, maybe causing their RR to be higher than when they were new. Anyone think that it is possible/ probable/ likely?

bbgobie 05-23-2007 08:39 AM

Quote:

Originally Posted by Bill in Houston (Post 52383)
I am currently driving on my 3.5 year old OEM tires with 40000 miles on them. They are not down to the wear bars, but are lower than I like to go. I have been putting off getting new tires because I am concerned that new tires will make my gas mileage drop due to the greater tread depth of new tires. BUT, I am wondering if it is possible/ probable/ likely that somehow the old tires have gotten stiffer as they have aged, maybe causing their RR to be higher than when they were new. Anyone think that it is possible/ probable/ likely?

2 other possibilities to think about:
1. Your worn tires have lost rotational mass because you've worn them donw.
2. Its very possible new tires would be more efficient and lighter with regards to FE.

I would replace the tires if they need to be replaced. Unless they are say for example super sticky high performance tires, and you don't drive like that.

Gary Palmer 05-23-2007 08:45 AM

I don't think that you are going to see enough of a drop in mileage, by putting on new tires, to be worth fiddling with. If you'd feel more comfortable with new tires and greater tread depth, then I would suggest getting them. It's worth the peace of mind.

rvanengen 05-23-2007 09:11 AM

Takes a lot of MPG to pay the insurance deductible...and I am not sure that any amount of extra MPG is worth your life or health. Get new tires (sensible) before you hit a good puddle!

zpiloto 05-23-2007 09:45 AM

Quote:

Originally Posted by Bill in Houston (Post 52383)
I am currently driving on my 3.5 year old OEM tires with 40000 miles on them. They are not down to the wear bars, but are lower than I like to go. I have been putting off getting new tires because I am concerned that new tires will make my gas mileage drop due to the greater tread depth of new tires. BUT, I am wondering if it is possible/ probable/ likely that somehow the old tires have gotten stiffer as they have aged, maybe causing their RR to be higher than when they were new. Anyone think that it is possible/ probable/ likely?

Just get LRR tires. Lots of tread, high 51 psi max rating and the RR would have to be better then 4 year old technology even if they are wore out.

Bill in Houston 05-23-2007 09:45 AM

But Randall, I don't want to drag the Leftover Bananas down. :-)

Okay, you guys convinced me. I'll do it within the next few weeks... Thanks for helping me do the right thing. Good tires are the cheapest insurance you can buy.

The Long Trail TAs are supposed to be low RR according to Greenseal way back when. Maybe they will be a noticeable improvement... Hey, I can dream, can't I?

thisisntjared 05-23-2007 05:15 PM

i think as tires get older the contact patch shrinks. as that happens there is less friction.

MetroMPG 05-23-2007 05:23 PM

The Prius comments I've read suggest that people notice replacement LRR tires of the same brand/size etc. have more RR than the old tires. But they also say the tires break in, and get better within a few 1000 miles.

slurp812 05-23-2007 05:28 PM

I had some old really crappy worn out performance tires on my car when I first got it. They were shot, like crayons slippery as a banana. I got new all season fairly cheap tires to replace them, and my MPG dropped about 2 mpg or so. I didn't calculate as accurately as I do now, but it was noticeably less miles per tank. Of course mine was almost a worst case scenario. So YMMV!

Bill in Houston 05-23-2007 06:15 PM

Quote:

Originally Posted by MetroMPG (Post 52490)
But they also say the tires break in, and get better within a few 1000 miles.

Thanks for trying to cheer me up. :-)


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