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#46
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How about looking at this way: if you were to remove one cleat from a bulldozer's track it would obviously cover less ground per revolution of the drive sprocket. Or would it? Actually the drive wheel's radius remains the same and it covers the same amount of ground, whether there are 50 cleats or 100.
Heheheheh....
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ASE Certified Master Automotive Technician w/L1. ASE Certified Master Medium/Heavy Truck Technician. Certified EVT (Emergency Vehicle Technician) |
#47
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All right...that does it!
Someone bring an air compressor to Reading so we can do the test I suggested with Rob! LOL...the only way I will accept that the same steel belting that makes up the circumference of an inflated tire slips, shrinks or vanishes when a tire looses air is if we get together and perform this test. I'll gladly use my car as a guine(?) pig. Like Lee, my mind works in a "classroom environment" mode. I'm not saying that Porter is wrong but until I see it actually happen in the real world I won't be able to put aside my doubts. Maybe there is some 4th dimensional factor occuring that I am not aware of.
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Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
#48
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We could all save a lot of gas money if we put taller tires on the rear, thereby allowing the car to run downhill most of the time.
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ASE Certified Master Automotive Technician w/L1. ASE Certified Master Medium/Heavy Truck Technician. Certified EVT (Emergency Vehicle Technician) |
#49
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I gotta quit doing this
BTW - Why don't we have to jack a tire up off of the ground in order to correctly adjust the air pressure? When the weight is on it the bottom of the tire flattens - doesn't that raise the pressure?
__________________
ASE Certified Master Automotive Technician w/L1. ASE Certified Master Medium/Heavy Truck Technician. Certified EVT (Emergency Vehicle Technician) |
#50
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Re: All right...that does it!
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LOL! The 4th dimension is there man, just waiting to suck you in! OOOH... I just had a thought... I'll be right back with a pic. |
#51
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Check it out... this illustrates it better.
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#52
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Re: I gotta quit doing this
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We don't because the manufacture tells us what the recommended presure is taking into account the weight of the car - which will change the pressure in a tire when applied. Oh yeah - so how do you check the spare? And for the record and to put this one to rest - the pressure will change (drop) if you jack up the car off the ground.
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Matt Locker Link 2015 BRZ Limited 6MT 92 Ebony LS-L ECUtune Stage2av1, Z32 MAF, 370cc injectors, TomsSVX intake, BontragerWorks 22mm RSB #003, HID Hi and Lo beams, OT endlink and bushing mods, PWR Aluminum radiator, Harvey's QC shift kit, 2.5" flowmaster 80 exhaust, 17" Michelin Pilot Sport A/S, Poly sway bar bushings, Slotted Bradi rotors, AFBeefcake powdercoated calipers, 97 grill, and a huge set of air horns. 300,000 miles and counting 92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles 19 Subaru Ascent Premium - -Hers !. 89 DL 4x4 little red wagon - a.k.a. The immortal suby. 275k R.I.P. |
#53
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OK, so I did the tire growing by pressure thing (as Lee continues to beat on this dead horse).
My right front tire grew by approximately 7/16" in circumference via changing pressure from 29 to 33 PSI. test methodology: let pressure down to 29, measured around tire. Added air from compressor to 33 and measured around again. No control or measurement of air temp inside tire, but both the tire and compressor were sitting overnight in my garage(about 74F). Tire particulars: Fulda Extremo, 225-50X16, Z-rated. This amounts to 0.5% growth in circumference. BTW, Assuming all else remained the same, a tread depth difference of 1/4 inch on these tires (front to back) would work out to be almost 1.6 inches difference in circumference (or about 2%). Maybe if I get re-energized (doubtful, but...) I'll try this with say a range of 15 to 33 PSI and see how much it changes. For now I have to do some heavy thinking on Beav's latest thoughts. Beav, wouldn't the position of the valve stem matter, i.e., it would balance out if the stem was at the bottom where the sidewall was flexed - wouldn't it? Oh, and assuming I forever after jack up my car to check tire pressure, I would think the stem needs to be in the same position on each tire when I measure - you know like altitude adjustments??? |
#54
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For the record, 225/45/17 falken azenis - 42psi with car on ground measured with digital tire pressure gauge in 60 degree garage air -41.5 psi with car jacked up. Repeated test and results repeated again.
...I just had to know
__________________
Matt Locker Link 2015 BRZ Limited 6MT 92 Ebony LS-L ECUtune Stage2av1, Z32 MAF, 370cc injectors, TomsSVX intake, BontragerWorks 22mm RSB #003, HID Hi and Lo beams, OT endlink and bushing mods, PWR Aluminum radiator, Harvey's QC shift kit, 2.5" flowmaster 80 exhaust, 17" Michelin Pilot Sport A/S, Poly sway bar bushings, Slotted Bradi rotors, AFBeefcake powdercoated calipers, 97 grill, and a huge set of air horns. 300,000 miles and counting 92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles 19 Subaru Ascent Premium - -Hers !. 89 DL 4x4 little red wagon - a.k.a. The immortal suby. 275k R.I.P. |
#55
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Quote:
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#56
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You guys crack me up... It was good seeing you last night, Matt! And your lovely wife too. Mike was convinced that she thought we were nuts or something. I was like, no way man.. she has one too!
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#57
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Quote:
Lowered air pressure only means a longer & wider contact patch and less effort for the engine to rotate the tire (leverage advantage od shorter radius). It does not mean that the circumference of the tire decreases. You will still have 87.9 inches (C = 2 x 3.14 x R(14")) of rubber to be travelled in one revolution of the wheel. If that shortened radius you keep basing it on was the only factor then you might be correct but you still have not explained what happens to the other 8.5" of tire circumference. Yes the tire is squashed where it touches the ground but tire still has the same circumference. That is the mystery that you are not explaining.
__________________
Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
#58
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You do realise that for this discussion to properly occur, we will need to be sitting in a bar with some good tunes in the background while we nurse some beers and munch some peanuts.
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Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
#59
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Yeah, but we'd have to keep our voices down in order to not attract the guys with the big nets and funny looking, long sleeved jackets.
__________________
ASE Certified Master Automotive Technician w/L1. ASE Certified Master Medium/Heavy Truck Technician. Certified EVT (Emergency Vehicle Technician) |
#60
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Quote:
Your concern (mine too originally) would be valid if all wheels were in locked hubs (that's the part I forgot - they aren't - I need a 'duh' slap). The critical difference for this explanation is that they are allowed to differ in the number of rotations between side to side & front to back. The tire rotates based on the radius at mid-patch contact. To go all the way around, it still has to use all the belt, but it doesn't have to turn around at the speed that the other tires do. So if one tire is at full pressure, it will only rotate at say 90% of the rotational speed of the half-flat tire because it has a larger effective radius at the contact point. Hence, that's why the differential gets taxed by differing pressures/sizes. Porter/Trevor, either I'm getting closer, or one of you is gonna have to come shoot me and put me out of this misery |
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