Best/Correct Tire Sizes??
12-22-2003, 04:45 PM
#1
Best/Correct Tire Sizes??
I know this has been discussed many times before..but the search function is disabled and i dunno whats goin on.
just lemme know what sizes are optimal for the following wheels please:
17x7
17x7.5
18x8
18x7.5
thanks again guys
just lemme know what sizes are optimal for the following wheels please:
17x7
17x7.5
18x8
18x7.5
thanks again guys
12-22-2003, 06:34 PM
#2
It's chrome alright...
Join Date: Dec 2001
Posts: 4,009
you don't have to search, it's in the FAQ (see the stickies at the top of this forum).
This is one of the things posted there. My next tires are 235/45r17s.
---original message---
In defense of running 235/45R17 tires on 5th Gen OEM rims quote:
There are many factors that go into setting safety standards for items like tires. The most important aspect of these in this discussion in layman's terms is the consideration of "what if...?" So what's the "what if" here? Seating of a tire in a rim has to consider adding all of the forces together that could cause a tire to be unseated, identifying the most critical, then using this as the safety design basis.
Even the most severe turn puts very little force on the tire/bead interface. First, the lever affecting the force on the rim (the distance from rim to road of 2.75") is short compared to the overall lever length (12" which is distance from road to hub), hence over 97% of the force (I won't bother with formulas) is transmitted to the center hub (the longer the lever arm, the more force is transmitted) at which point the lugs take the stress. The remaining force is distributed evenly around both circumferences of approximately 120" linear length (total of inside and outside circumference of bead length), PROVIDED THERE IS SUFFICIENT INFLATION to equalize force distribution (back to the caps in a minute). Hence even a severe turn exerts only a very small lever force that is distributed throughout the tire. Modern tire designs all use wire cable in the bead area for reinforcement to retain tire diameter at the bead, providing an additional safety margin. The CAPS above are to emphasize the lowest common denominator in the tire safety equation: pressure. Tire pressure is what seats and seals the tire to the rim and distributes peak loads throughout the tire to dispell energy. Hence the engineer's challenge and the limiting factor is maintaining adequate pressure in the tire for that dreaded unknown factor: the consumer.
As we all know, most people don't bother checking tire pressure on a regular basis. Therefore the National Highway Department and tire manufacturers have to set their standards to the lowest common denominator, a too-low tire pressure where the rim is almost to the road due to low pressure (probably around 2-3 psi). Under these circumstances, an emergency maneuver places at least a 1000-fold increase in point pressure at the tire/bead interface since it is only the bead (<2") on the outside of the rim that has to take all of the side forces of a sudden maneuver. The tire contends with an additional force here where the tire tends to "fold over" as the vehicle's weight shifts, bringing much more of a side vector force on the bead interface.
In the Ford Explorer/Firestone tire fiasco, Ford listed a recommended inflation range of 22-26 psi for a few years, actually lower than what Firestone recommended. Given the lack of maintenance that SUV owners are notorious for, in all likelihood the tires were rolling off the rim, especially in cases where the wheel dropped off the edge of the road. It is no wonder that Explorers were rolling over!
So, what do I do to ensure my own safety margin? In addition to a RSB and FSTB to distribute force equally to all 4 tires, I also visually check all 4 tires' levels before EVERY trip, maintain my tires with at least weekly tire pressure checks, and run a pressure of f/r 36/32 psi to ensure a tight and safe bead seat. [SIDEBAR: Why do I run a higher pressure in the front? To better support the front weight bias of our cars to give me more neutral handling (less understeer).]
Just to anticipate your follow-up question for the accident scenario, if I lose tire pressure suddenly (massive blow-outs don't really occur if tire pressure is maintained, sniper attacks not included!), I imagine there WOULD be an increased risk of the tire rolling off the rim. But you have to remember that in this scenario that tire is going to be a handling problem REGARDLESS without its vital air pressure.
SUMMARY: Tire safety standards are set assuming the worst case, which in this discussion is the lowest possible pressure that keeps the rim off the road for many consumers. Since I check my tires at every trip, know their height when normal, and back this up with regular (at least weekly) tire pressure checks, then I am confident that I am operating a safe vehicle at 104% width compared to guidelines.
CAVEAT: I am NOT recommending this choice for all of you, this is MY choice as you might consider me an outer fringe high-risk taker. I am currently starting a business to commercialize a new chemical process to make hydrogen peroxide by directly reacting hydrogen and oxygen gases, certainly a hazardous operation if not done carefully (remember the Hindenburg!). I also have worked with rocket fuels and components for binary nerve gas agents, so I am VERY aware of safety considerations in designs of equipment and materials. Tires that are properly inflated are critical to my own safety and that of my family, and safety is an essential consideration at ALL times.
Credit: RsMaxMaggie
Source: http://forums.maxima.org/showthread.php?threadid=131766
Personal note: This is the FIRST and ONLY scientifically based argument I've seen on this forum that supports exceeding industry and manufacturer safety guidelines. Notice, however, the steps RsMaxMaggie undertook and continues to undertake to justify exceeding those guidelines:
(1) Installed Front Strut Tower Brace (FSTB)
(2) Installed Rear Sway Bar (RSB)
(3) RELIGIOUSLY maintains correct tire pressure at all times
If you are not prepared to follow his example or if you are adverse to taking risks, I suspect that RsMaxMaggie would put you into the category of those who should NOT exceed industry and manufacturer safety guidelines.
This is one of the things posted there. My next tires are 235/45r17s.
---original message---
In defense of running 235/45R17 tires on 5th Gen OEM rims quote:
There are many factors that go into setting safety standards for items like tires. The most important aspect of these in this discussion in layman's terms is the consideration of "what if...?" So what's the "what if" here? Seating of a tire in a rim has to consider adding all of the forces together that could cause a tire to be unseated, identifying the most critical, then using this as the safety design basis.
Even the most severe turn puts very little force on the tire/bead interface. First, the lever affecting the force on the rim (the distance from rim to road of 2.75") is short compared to the overall lever length (12" which is distance from road to hub), hence over 97% of the force (I won't bother with formulas) is transmitted to the center hub (the longer the lever arm, the more force is transmitted) at which point the lugs take the stress. The remaining force is distributed evenly around both circumferences of approximately 120" linear length (total of inside and outside circumference of bead length), PROVIDED THERE IS SUFFICIENT INFLATION to equalize force distribution (back to the caps in a minute). Hence even a severe turn exerts only a very small lever force that is distributed throughout the tire. Modern tire designs all use wire cable in the bead area for reinforcement to retain tire diameter at the bead, providing an additional safety margin. The CAPS above are to emphasize the lowest common denominator in the tire safety equation: pressure. Tire pressure is what seats and seals the tire to the rim and distributes peak loads throughout the tire to dispell energy. Hence the engineer's challenge and the limiting factor is maintaining adequate pressure in the tire for that dreaded unknown factor: the consumer.
As we all know, most people don't bother checking tire pressure on a regular basis. Therefore the National Highway Department and tire manufacturers have to set their standards to the lowest common denominator, a too-low tire pressure where the rim is almost to the road due to low pressure (probably around 2-3 psi). Under these circumstances, an emergency maneuver places at least a 1000-fold increase in point pressure at the tire/bead interface since it is only the bead (<2") on the outside of the rim that has to take all of the side forces of a sudden maneuver. The tire contends with an additional force here where the tire tends to "fold over" as the vehicle's weight shifts, bringing much more of a side vector force on the bead interface.
In the Ford Explorer/Firestone tire fiasco, Ford listed a recommended inflation range of 22-26 psi for a few years, actually lower than what Firestone recommended. Given the lack of maintenance that SUV owners are notorious for, in all likelihood the tires were rolling off the rim, especially in cases where the wheel dropped off the edge of the road. It is no wonder that Explorers were rolling over!
So, what do I do to ensure my own safety margin? In addition to a RSB and FSTB to distribute force equally to all 4 tires, I also visually check all 4 tires' levels before EVERY trip, maintain my tires with at least weekly tire pressure checks, and run a pressure of f/r 36/32 psi to ensure a tight and safe bead seat. [SIDEBAR: Why do I run a higher pressure in the front? To better support the front weight bias of our cars to give me more neutral handling (less understeer).]
Just to anticipate your follow-up question for the accident scenario, if I lose tire pressure suddenly (massive blow-outs don't really occur if tire pressure is maintained, sniper attacks not included!), I imagine there WOULD be an increased risk of the tire rolling off the rim. But you have to remember that in this scenario that tire is going to be a handling problem REGARDLESS without its vital air pressure.
SUMMARY: Tire safety standards are set assuming the worst case, which in this discussion is the lowest possible pressure that keeps the rim off the road for many consumers. Since I check my tires at every trip, know their height when normal, and back this up with regular (at least weekly) tire pressure checks, then I am confident that I am operating a safe vehicle at 104% width compared to guidelines.
CAVEAT: I am NOT recommending this choice for all of you, this is MY choice as you might consider me an outer fringe high-risk taker. I am currently starting a business to commercialize a new chemical process to make hydrogen peroxide by directly reacting hydrogen and oxygen gases, certainly a hazardous operation if not done carefully (remember the Hindenburg!). I also have worked with rocket fuels and components for binary nerve gas agents, so I am VERY aware of safety considerations in designs of equipment and materials. Tires that are properly inflated are critical to my own safety and that of my family, and safety is an essential consideration at ALL times.
Credit: RsMaxMaggie
Source: http://forums.maxima.org/showthread.php?threadid=131766
Personal note: This is the FIRST and ONLY scientifically based argument I've seen on this forum that supports exceeding industry and manufacturer safety guidelines. Notice, however, the steps RsMaxMaggie undertook and continues to undertake to justify exceeding those guidelines:
(1) Installed Front Strut Tower Brace (FSTB)
(2) Installed Rear Sway Bar (RSB)
(3) RELIGIOUSLY maintains correct tire pressure at all times
If you are not prepared to follow his example or if you are adverse to taking risks, I suspect that RsMaxMaggie would put you into the category of those who should NOT exceed industry and manufacturer safety guidelines.
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