wider tire?
11-28-2008, 09:41 AM
#12
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
157 - there was nothing wrong with your approach - it would apply quite accurately for something like a free-rolling steel railroad wheel. IOW, it's an omission of something not generally obvious rather than an "error".
What's easy for most people to miss is that there is a correction for tire tread circumferential compression as it passes through the contact patch zone. The amount of this compression lies somewhere between the difference between circumference calcs based on the unloaded and loaded radii, and most folks don't have any tire tech references handy to give them a number to put on this even if they recognize that the effect exists.
Norm
What's easy for most people to miss is that there is a correction for tire tread circumferential compression as it passes through the contact patch zone. The amount of this compression lies somewhere between the difference between circumference calcs based on the unloaded and loaded radii, and most folks don't have any tire tech references handy to give them a number to put on this even if they recognize that the effect exists.
Norm
Last edited by Norm Peterson; 11-28-2008 at 09:42 AM. Reason: I type slow and had to add a post reference
11-28-2008, 03:06 PM
#13
Cut & Paste Expert
Join Date: May 2007
Location: NW Arkansas
Posts: 13,322
157 - there was nothing wrong with your approach - it would apply quite accurately for something like a free-rolling steel railroad wheel. IOW, it's an omission of something not generally obvious rather than an "error".
What's easy for most people to miss is that there is a correction for tire tread circumferential compression as it passes through the contact patch zone. The amount of this compression lies somewhere between the difference between circumference calcs based on the unloaded and loaded radii, and most folks don't have any tire tech references handy to give them a number to put on this even if they recognize that the effect exists.
Norm
What's easy for most people to miss is that there is a correction for tire tread circumferential compression as it passes through the contact patch zone. The amount of this compression lies somewhere between the difference between circumference calcs based on the unloaded and loaded radii, and most folks don't have any tire tech references handy to give them a number to put on this even if they recognize that the effect exists.
Norm
I thought of this when replying but didnt want to get too technical.
Like air pressure effecting the REVS/MILE because of the contact patch
situation with air filled rubber tires and not steel train wheels or wagon
wheels with zero slippage so as to not have to factor that variable into
the equasion also. I measured my BFG 255/45-18 KDW2s muonted on
18x8.5" rims and they differed from my numbers but were close to the
235/55-17s I removed and the 215/65-16s that were OEM.
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