The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Bigger tires

donut · 04-28-2012, 10:07 AM

No comment on larger tires, don't know. Depending on the actual cruise rpm they may help, at the expense of lower rpm driving.

I wanted the torque down low, so I went with a 245/75 series tire, iirc 31" close to what I think was stock. 65-70 mph was showing 3000-3200 on my tach. Mpg noticeably dropped @ 70. I toyed with the thought of OD, but with the cost, I figured I could buy a lot of gas.

A friend of mine was getting 15 mpg with a 6.0l and OD in a 3/4 ton, so I didn't think 13 mpg with 4.10's and no OD was that bad.
His truck was more comfortable, but I wasn't shelling out hundreds a month for the privilege.

Bottom line, how did you calculate the rpm? Maybe borrow a tach off a buddy for a week?

04-28-2012, 10:07 AM	#10
donut Registered User Join Date: Aug 2009 Location: S.C. Posts: 1,593	Re: Bigger tires - better gas mileage? No comment on larger tires, don't know. Depending on the actual cruise rpm they may help, at the expense of lower rpm driving. I wanted the torque down low, so I went with a 245/75 series tire, iirc 31" close to what I think was stock. 65-70 mph was showing 3000-3200 on my tach. Mpg noticeably dropped @ 70. I toyed with the thought of OD, but with the cost, I figured I could buy a lot of gas. A friend of mine was getting 15 mpg with a 6.0l and OD in a 3/4 ton, so I didn't think 13 mpg with 4.10's and no OD was that bad. His truck was more comfortable, but I wasn't shelling out hundreds a month for the privilege. Bottom line, how did you calculate the rpm? Maybe borrow a tach off a buddy for a week? __________________ '86 C-30 dually, 454/tbh400 '73 K-20 350/350/205 (sold ) I'm kinda like duct tape- no real purpose, but handy to have around.