Max Tyre Size for M47 Pickup 16" Rim

[waynet]

Hi Folks,
I am wanting to reduce engine RPM, when cruising the highway, by increasing rear tire size on a standard 16" rim on our Mercury M47. Currently running 215/70/16 with 3 speed box and Dana 41 rear end.

Any experienced suggestions?
Thanks.

[Mart]

235/85R16 Land Rover size.

[frnkeore]

I run 215 x 85 x 16's on my F350. They are 30.39" tall.

Your 215 x 70 x16, should be 27.85". The 85's should give a extra 2.5+".

If your rim width will except the 235's width, you'd have a tire 31.73 tall, a extra 3.88".

How wide are your rims?

Edit:
If you go with the 215 x 85, it will increase your speed from 60 mph, to 65 at the same rpm, the 235 x 85 would be 68 mph.

[truckdog62563]

A 235/85R16” has a minimum rim width standard of 6.00”. These would be appropriate only if you have non-stock wider rims. If you have stock 4.50” rims even your current 215/70R16s are over spec. Stu

[waynet]

Originally Posted by truckdog62563

A 235/85R16” has a minimum rim width standard of 6.00”. These would be appropriate only if you have non-stock wider rims. If you have stock 4.50” rims even your current 215/70R16s are over spec. Stu

Stu I was unaware of that. Stock rims they are.

[Fred A]

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Interesting that Stu mentions the rim width specs in an old Ford or Hot Rod environment. For years the "community" has scoffed at that specification with 750s mounted on 4" wide wheels, almost as a tradition. "They may look like donuts but they work great" We need some slick lawyer to check that assumption if any accident can be blamed on improper equipment, no matter of fact required. I have Good Year Wrangler P235/75R16s @ 29.25" squeezed into Ford Pickup/Station Wagon wheels(4.50"). Widest vintage 16" Ford/Merc/pickup wheels I see in the service bulletins is 5". I went to aftermarket to go beyond. Caveat: Fred A

[truckdog62563]

I put my name at the bottom of every posting I make, both here and on FTE. I have a reputation and try to give factual info supported by references. When correct tire sizes exist I think it wise to stay within Tire and Rim Association standards. In this person’s case I would stay with stock 6.50-16” tires.

I try to avoid the debate over bias vs radial tires on cars and small trucks. Our old riveted rims were never intended for radials, but I’ve not found an authoritative reference that documents harm due to their use. This is not the case on big truck tubeless sizes used commercially. I have an SAE study showing rim failures due to radial usage on early riveted tubeless wheels. Stu

[Fred A]

I'm not critical of anything Stu writes. I was impressed that someone other than I notices that there is a standard. There are so many ignored engineering and safety standards in the old car hobby, that it invites unwanted regulation as we got with emissions, and safety industries. Good Luck: Fred A

[waynet]

Originally Posted by Fred A

Interesting that Stu mentions the rim width specs in an old Ford or Hot Rod environment. For years the "community" has scoffed at that specification with 750s mounted on 4" wide wheels, almost as a tradition. "They may look like donuts but they work great" We need some slick lawyer to check that assumption if any accident can be blamed on improper equipment, no matter of fact required. I have Good Year Wrangler P235/75R16s @ 29.25" squeezed into Ford Pickup/Station Wagon wheels(4.50"). Widest vintage 16" Ford/Merc/pickup wheels I see in the service bulletins is 5". I went to aftermarket to go beyond. Caveat: Fred A

Very interesting Fred - so there are a few options then?