Weight vs Diameter of Tire??
 

Hey all,

I was looking to get some tires for my 86 yota pickup 4wd. It has a 4cyl. 5 speed tranny. Of course i am looking to get the best mpg. :)

A 235/75/15 is about 29" diameter and weights 35-37 lbs.

A 225/75/15 is about 28" diameter and weights 27-28 lbs. (stock size)

My question what would give the best mpg? The larger tire making the gears a little taller but heavier? OR The smaller and lighter tire with stock gearing.

I currently have some old mismatched 235's on some steels, but the new tires will go on some OEM alloys. I am currently getting about 23 - 24 maybe?? At best. :(

Thanks,
Kirk

I think in the case of a m/t pickup, stock size is best.

You have the 5 speed OD tranny which I think gives you a pretty good OD ratio in stock form. I don't think the slight change in final drive will over come the weight penalty, especially since it is rotational weight.

Also, the stock tires are likely to be a fair bit cheaper.

That's a large weight gain for a small increase in tire size. Are the smaller tires P (passenger tires) and the larger LT (Light Truck)? Or are both the same type?

I went from a P to an LT on my Silverado. Even though the size was the same and I could run higher tire pressures, the weight went up and fuel economy went down (even after they were broke in). Between those two options, the smaller is likely the better of the two.

http://ecomodder.com/forum/showthrea...hts-19698.html

Why guess?

What is the rpm at 50, 60, 65, 70? (for what you currently have)
then do the % change with the size not on the truck.

not sure were you got your weight but it's way off.
the tires (just tires) are 2lbs apart.
weight issue is a mote point.
Kumho Solus KR21
the tire revolutions are 734 and 716. that barely 3%. Statisticly you need 5% + to really be able to notice any difference.

yes it is a large weight gain, although i just checked the specs and it depends on which tire brand we are looking at. The specs vary a significant amount. The above LT tire was actually 40 lbs. and the P tire was 27 lbs. The tires i was looking at were the Eldorado ZTR as they are available locally.

The Toyo Open Countrys P225 weigh 27.8 lbs. and the LT235 weigh 34.4 lbs. A much smaller difference. Though the P235 still weighs 34.2 lbs.!

Thanks for sharing your experience on the weight gain.

I know at 55 mph i'm running at 2200 rpm in 5th gear. That is with the oddball 235's...

True for the kumho solus...
 

I was comparing a "P" tire to a "LT" tire. The tire brands i was looking at had only one preferred size in each of the two classes - P, LT. I guess i was comparing apples to oranges in a way? :o So depending on brand i may be able to get the weight down. :thumbup:

Im looking for an All Terrain tire BTW. :) it kinda limits the options a bit.

Thanks for the info on statistics. I bet i might be able to "just" tell a difference 'cause my truck lugs a bit now with the 235's. :D

Thank you all for your support and guidance! :)

I will look at the "P" tires for the weight advantage (price too) and probably go with the slightly narrower and smaller stock tire despite the small difference. Though some brands/models the difference is greater.

Just to put this all in perspective:

The larger tire will result in ever so slight improvements in fuel economy - all other things being equal. The biggest problem is the "all other things" part.

Changing from P type tires to LT type tires is the wrong direction for F/E. LT tires are "work" tires and F/E isn't much of a consideration.

All Terrain tires will be worse than All Season tires. More mass.

There are tires with improved RR, but they frequently have sacrifices in treadwear or traction. That might be OK with you, but for many, it's not.