Ah cool - I think I should be ok w almost 1 3/8" clearance running the Asfir skids. Looks like the sway bar will butt against the radiator hose connect or dang close?
34's on stock setup - it's done, now some advice...
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Markuson
SILVER Star
You're in San Diego... Maybe we can meet somewhere and you can have a look at mine...
My bar is close to the radiator hose but doesn't contact it.
You should be fine without spacers. My stock skids are much closer.
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- #144
FWIW I was reading online recently in the DOT specifications that tire size is measured when mounted at some predefined temperature and pressure but not actually on the vehicle. I would be very curious to know what your 35s measure at 80psi (assuming they are E load) vs the 35psi or whatever you normally run them at. If you want a "true" 35x12.5, you just need to treat your tires like they're basketballs.
The Code of Federal Regulations of the United States of America
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- #146
"official" size is measured at 38C/100F ambient temperature.
I would assume that once you get near the max psi the size doesn't change much. i.e. 80psi cold and 90psi hot wouldn't be significantly (if at all) different in circumference. In fact it's entirely possible that the circumference might max out (or the increase will taper off) well before you reach maximum pressure.
You should try and measure them while you're flyin' down the highway Tony and see if they're any different than when parked and cold
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It's even worse here.... 25-30psi in the AM and 40-42psi in the heat of the day 2-4 PM. Plus the 6300-7600' elevation takes its part in the pressure changes.
J
"official" size is measured at 38C/100F ambient temperature.
I would assume that once you get near the max psi the size doesn't change much. i.e. 80psi cold and 90psi hot wouldn't be significantly (if at all) different in circumference. In fact it's entirely possible that the circumference might max out (or the increase will taper off) well before you reach maximum pressure.
You should try and measure them while you're flyin' down the highway Tony and see if they're any different than when parked and cold
If I remember I'll get measurements before I leave and when I get to work. There's also a decent elevation change as I'm now living in North SLC up on the bench.
Markuson
SILVER Star
Rim width is also a significant factor because of its effect on whether the side wall is free to span straight up to the outer tread, or if it is pulled at an angle, inward to a narrower wheel. This will shorten the tire...
This is one of the reasons why I always chuckle with those posts that say "You should run exactly 37.25psi or you're going to die" because unless you're using nitrogen to refill your tires when you air up after trail duty, you're going to experience a lot of fluctuation based on a ton of factors - temperature, load, road conditions, elevation, driving style, etc. I ride motorcycles and check my psi religiously on the bikes, but even then there is enough of a variance over the course of a ride I don't worry too much about a psi off here and there.
gaijin
GOLD Star
There's a lot to unpack here, and I've touched on a lot of the bits and pieces involved before, but let me try again using your post as a guide in an attempt to dissemble fact from myth.
- Tire pressure recommendations are always given as Cold Tire Inflation Pressure. This means that the tire/wheel combo is at the same temperature as the surrounding air (ambient) temperature. This recommended pressure assures that the tire will have the required Load Limit to handle the loads imposed on it by the vehicle and the manner in which it is driven. Factored into the recommended Cold Tire Inflation Pressure is the fact that the tire pressure will increase as the tire temperature rises above ambient as it is driven. This is normal. This is why it is dangerous to adjust tire pressure when a tire is "hot" or above amnbient pressure because as the tire cools to ambient, the prtessure will decrease below the recommended pressure.
- ALL gases will expand as temperature increases. It makes no practical difference whether a tire is filled to its Recommended Cold Tire Inflation Pressure with compressed air, Nitrogen, Carbon Dioxide, Argon, Helium, or any other gas - as the tire temperature increases, the tire pressure will increase. There is a lot of misinformation out there about the reasons for using gases other than compressed air, but the bottom line is that any gas that comes compressed in a cylinder - like Nitrogen - will not contain any moisture/water vapor. It is the water vapor - common in compressed air - that can cause dramatic increases in tire pressure. This is due to the fact that water vapor expands about seven times more than any dry gas when its temperature increases. Using a dry gas, like Nitrogen or Carbon Dioxide, will help control dramatic pressure swings as tire temperatures change.
- It is normal under ALL use conditions that cause the tire temperature to change that tire pressures will fluctuate. It is silly - and also wrong - to try to monitor/adjust tire pressures under these dynamic conditions. What is important, and is worth worrying about "a psi off here and there" is when the tire is adjusted to the Recommended Cold Tire Inflation Pressure when at the same temperature as the ambient conditions.
HTH
I wasn't calling you out or anyone else for that matter, but I do think people can get too preoccupied with ensuring their pressure is exactly perfect. For instance, when you say "This is why it is dangerous to adjust tire pressure when a tire is "hot" or above amnbient pressure..." that can be confusing or misleading in an instance like spending a hot day on a trail in the desert where one has aired down to say ~15psi and needs to air up for the drive home. Clearly the tire and air inside is hot, the ambient temperature is hot, the road surface is hot, and the drive home will see highway speeds. To say it's dangerous to inflate while the tire is hot could indeed scare well intentioned people who are already confused about what to do. What I do (and I think it's the reasonable thing to do) is to fill my tires to where I want them to be for the ride home which is typically 38psi, and in the next day or two check the pressure when the truck is sitting in the garage and top off / bleed out air if necessary. I've had good luck with even wear, longevity and on/off road manners in the ~18 years I've been going off road, and I'm confident I haven't always been exactly perfect on psi...but probably pretty close.
gaijin
GOLD Star
My intention was to caution against adjusting tire pressure to the Recomended Cold Tire Inflation Pressure at every rest stop on the highway while the tires are hot. This would result in underinflated tires.
I agree entirely with your suggested practice for airing up after airing down while out on the trail. What I do when airing down is measure the tire pressure just before airing down, while the tire is hot, while I am at altitude, etc., make a note of that tire pressure so that when I air up before hitting the road back home I can re-inflate to that pressure. Of course, I would adjust again the following morning when everything is at ambient again.
HTH
@Markuson @TonyP @Willy beamin thanks - install relo no problem - no rubbing on driver - tad rub on passenger sway but smooth surface. True 34s on 17 look great - was on 33 w 18s. Sorry to hijack your post @linuxgod but it's 34s I mounted this week and this was a great thread.
Exactly right. Engineers don't get measurements wrong (very often). The only way to get accurate measurements is by way of well defined parameters and processes, that reduce variables that affect the measurement.
To think we as laymen can do it better with a tape measure is silly. Which is why I still insist this is the only way to measure apples to apples between tires.
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- #156
Heh no problem. Glad to see the discussion and what you've done.
And I'm still gonna claim I run a 34, even though its not actually 34 unless I run 80psi in it
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- #157
I personally wasn't implying that you should actually measure temperatures hot. I just wanted to see if TonyP would whip out the tape measure and lean out the window at 70mph
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- #158
We've got clearance, Clarence.
Teaser courtesy of my wife who says "on the lowest adjustment, it's really soft".
Teaser courtesy of my wife who says "on the lowest adjustment, it's really soft".
- Thread starter
- #160
How long did it take for your setup to settle? Keep in mind I have Toyota bumpers. Wife says "it's tall. Sliders are knee high".
I'll take measurements and photos tonight.
