With Formula 1 cars running 13 inch diameter wheels
and NASCAR running 15 inch diameter wheels
people who argue that 20 inch diameter wheels
are necessary for braking
ought to get a subscription
to Race Car Engineering magazine.

The toughest braking challenge in all of auto racing
is the LeMans series.

I will let anyone interested
look up what diameter tires LeMans runs,
and what lessons you can draw from that.

Who said that it was pimps who originated the big tire craze?

It was Bob Lutz, not me.

 

Ok ya got me on that one, I don’t subscribe to any engineering magazines.

Speaking of NASCAR what about those inner tires for long tracks, how does that affect 'rotational moment of inertia?'

Really now how many regular old vehicles have dedicated brake cooling systems lets say like F1, NASCAR and Le Mans? My point exactly.

Since braking is considered part of driver skills in those sports and regulated (NASCAR not as much) they have systems that directly cool the immense heat generated by their brakes. Again my point.

How does one do that in a normal old truck coming down the mountain hauling a 5k load? I'm guessing the larger area for air to flow the better.

Hey what about those other racing sports like at the drag strip, muddin or ones like that? What size rims do they use? I bet Big Foot would uses 12 inch rims if he only new about that Race car engineering magazine, then again maybe not.

As for Bob Lutz I didn’t see you quote him until now.

Hank I wish I had more time to philosophize with you but I will be on the road for a week. So you have the floor.

Be safe and have a great week.

 

Not taking any sides, but I will contribue what I know as a fact (from my mechanical engineering degree pursuit, and I don't think these support either sides, I think both of you have valid points). Torque is force x distance, so the greater the overall TIRE HEIGHT (diameter of tire, not just rim) the lower the force exerted at the road. Also, the greater the deformation of the tire (greater rolling resistance) the less of the force pushing the vehicle forward. These are also altered by the rotational center of gravity; if the majority of the mass is farther out more force will be required to rotate the wheels and vice versa. As it turns out, there is a lot of variables in determining the best tire/wheel size combo in the best mpg debate, and often changing wheel/tire sizes will not be very noticeable to the average person.

 

My offroad wheels with the 275/70/17 tires weigh 72#. I put some aftermarket 20x10 mottos and with tires, they weighed 92#. The performance hit just at part throttle was so bad, I put 4.56 gears in just to compensate. I can't recall the formula for axle weight but the 80# I added was equiv to close to 400# in the bed. Added axle end weight is way worse than weight in the bed.

Now that I need tires again for the 20's, I've got the offroad 17's and 275/70 tires in the back of my truck right this minute to have put back on.

I will say that my friend with his '07 4x4 Ram commented on how light his new 20's were compared to the previous model trucks. I don't think he's weighed one though.

 

http://en.wikipedia.org/wiki/Unsprung_weight

since they may soon change the US law on what has to be stamped
on the tire sidewall:

http://www.moderntiredealer.com/t_in...p;storyID=7401

It would not be a bad idea at all to stamp the weight of a new tire on there too, along with rolling resistance

 

Gee and someone said I was nuts! lmao!

I build Race cars so I know that a change in the front tires of 40lbs is worth .10 to .20 in the quater!

I may even go 17s just to save more weight

 

This is true in Drag Racing also! Find me a Full on Top Fuel /Funny car or Pro Stocker with anything other than a 15" wheel! Cant reason weight! Tires weigh a lot less then anything out there. And drag tires are not made for street use! Reason there 1 and 2 ply side walls to reduce weight and rolling resistance!

In a street car application the weight dif. can be felt big time! On my T-Type for example I took the factory Wheels off the car (They didnt seem to weigh that much) and put my Pro Stars on the car. Now I notice they were lighter but again not by that much, The first ride I went on with them the car stopped faster (Even with 3" ons in front!) and seemed to move with less presure on the gas pedal!
I then changed to Aluminum drums and the car again stops faster and has better throttle responce! The dif, in weight in the drums was only 3#'s each!
Its not just in my head and with gas prices the way they are I am looking to get as much as I can even if I do have to go to a 17" wheel to do it

On a side note if you keep the 33" tire diamiter your speedo will be uneffected and the only diff. would be in the Weight as long as I can find a tire the same width as the stockers. (The width thing is an issue as it increases rolling resistance) Thus far the Width is the issue as I have not found to many tires that only have 10.1 contact patch and still look hald way cool

 

Bob Lutz has it right its totaly true the first cars we saw in the Detroit area with 20"s were on the drug dealers cars when we went downtown to the getho to watch some street racing that was like late 1990's ! [:-]
We were all like thats gay looking and then they took off with all the sports people and now we have shows like Uniqu whips on speed that all they do is bolt on a set of 20-25" wheels a gay grill and charge out the *** for it and people think its cool?? WTF car customizers in the 50's did more than that for less $ lmao!
Just my .02 I think 20's look cool on the rams dont get me wrong and they look cool on the new chargers and 300C's but I wouldnt do it as I am a white boy!