Unsprung Weight vs. Rotating Mass

A.I.I.Raciing said:

There some very smart guys in here and I was wondering something, if a 35" tire weigh's 83 lbs, would it be about the same power lose as running a 37" tire that weighs 68 lbs?

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It's interesting to me that a 35 weighs 83 lbs. and a 37 weighs 68 lbs.

I get that it's correct but still, I find it interesting that there's a 15 lb. discrepancy between the two tires you're talking about.

What I would like to see on this forum is a list of:

1. Tires that Raptor owners use and the weight of each (including the stock BFGs)

2. Wheels that Raptor owners use and the weight of each (including the stock wheels)

Seems to me that all wheel and tire discussions should include some mention of their respective weights. I think it'd be great to have those weights listed somewhere that's easy to find.

Which 37" tires are 68lbs? I would like less unsprung weight I saving that much might push me over the edge to 37" tires

MagicMtnDan said:

It's interesting to me that a 35 weighs 83 lbs. and a 37 weighs 68 lbs.

I get that it's correct but still, I find it interesting that there's a 15 lb. discrepancy between the two tires you're talking about.

What I would like to see on this forum is a list of:

1. Tires that Raptor owners use and the weight of each (including the stock BFGs)

2. Wheels that Raptor owners use and the weight of each (including the stock wheels)

Seems to me that all wheel and tire discussions should include some mention of their respective weights. I think it'd be great to have those weights listed somewhere that's easy to find.

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I think there is a sticky that discusses the weight of different wheels/tires

Killjohnathan said:

I think there is a sticky that discusses the weight of different wheels/tires

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If you find it please post a link to it here. Thanks

AZEngineer said:

Which 37" tires are 68lbs? I would like less unsprung weight I saving that much might push me over the edge to 37" tires

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BFG A/T in 37" are 66.4 lbs. BFG MT2 are 68lbs - 70lbs, depending on the data source. All of the other 37's are quite a bit heavier.

---------- Post added at 12:47 PM ---------- Previous post was at 12:44 PM ----------

Wheel weights:
http://www.fordraptorforum.com/f25/raptor-aftermarket-wheel-weights-1841/

Tire weights:
http://www.fordraptorforum.com/f25/tire-weights-1835/

Both are stuck at the top of the wheel / tire forum.

Read this and though some might want to see it also

"Rotational mass is 4x's as important as sprung weight, and 2x's as important as un-sprung weight. So if you remove 40lbs of rotational mass it will give you a similar effect as removing 160lbs out of your chassis. You will brake safer, accelerate harder, and carry more speed.
A 2 piece rotor is a simple and effective way of removing rotational mass. In some cases we've seen a weight savings as high as 15 lbs per wheel!! That’s 60lbs of rotational mass, similar to removing 240 lbs from your chassis. That’s one way we can engineer your car for total performance"

Digging around the cellar here I had to add something simple that can nearly negate differentials.

Going with a lighter same size wheel to offset increase in tire weight neutralizes the differential of weight. Where the comparison is 35-37" tires is concerned, the inertia difference in rotating mass will be literally indifferent to the "seat of the pants" feel. In other words acceleration from a stop wont be all that noticeable.
I'm going to try to validate this by replacing my OE wheels and tires with a set of American eagle wheels that weigh 26 pounds. (I think 12 pounds lighter) and BFG KO2 37x12.5x17's. The tires are 71 pounds to the OE tires 64. In theory I should notice improved handling and responsiveness in all conditions. The acceleration loss in gear change should be negated, and by the actual overall weight loss improved.

---------- Post added at 02:56 PM ---------- Previous post was at 02:54 PM ----------

Great post Dan.

Good old boy observation:

I just put 37" Generals on my truck. I cannot notice any changes in acceleration. 5* tune and Methods. Can't wait to get it off road, but street and highway manners are unaffected as far as I can tell.

Just my $.02