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Author: Subject: Airing down w/ 20" rims
Santiago
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[*] posted on 10-15-2018 at 07:04 AM
Airing down w/ 20" rims


New trucks seem to come with 20" rims now, anyone have issues airing down with them?
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[*] posted on 10-15-2018 at 07:28 AM


I'm not a tire guy but I would think it's more the profile of the tire and not the wheel size. I've stopped to help more than one car driver with sporty low profile tires who had just slammed into a pothole and bent a rim. If you air down you need to maintain some distance between the rims and the ground. My truck came stock with 70 profile tires and I switched out to 75 profile to add a wee bit of clearance when I air down.
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[*] posted on 10-15-2018 at 07:35 AM


Yes, I would think the aspect ratio of the individual tire would have some to do with it. 50 series on a 20" rim seems problematic on dirt roads.

John
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[*] posted on 10-15-2018 at 08:34 AM


I agree with both of the above, I wouldn't do any offroading or airing down with a 50 series. A truck tire on a 20 should not be a problem..

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[*] posted on 10-15-2018 at 08:36 AM


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[*] posted on 10-15-2018 at 09:32 AM


Modern cars with 20 inch wheels give tires a larger contact profile to the roadway, great for improved driving on the street, but not good for off road at all due to the lack of tire sidewall height.



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[*] posted on 10-15-2018 at 01:12 PM


All info correct . For me 20in rims off road beat you up. Now if you have tall sidewalls it will work ok.
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[*] posted on 10-15-2018 at 03:48 PM


half tire wheel rule.......got 40's?
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[*] posted on 10-15-2018 at 05:58 PM


Its not the wheel that is the issue...Its the tire. modern low profile TIRES are problematic when airing down.
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[*] posted on 10-15-2018 at 07:40 PM


Quote: Originally posted by norte  
Its not the wheel that is the issue...Its the tire. modern low profile TIRES are problematic when airing down.

main point is that low profile tires hold only a very small amount of air
the amount of air is actually what supports the weight of the car
since you have only a small amount of air in low profile tires, you don't have any flexibility to let some out

low profile is good for performance and speed - and some like their looks
they have absolutely no business beyond pavement




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[*] posted on 10-15-2018 at 07:45 PM


for off road use tires should have about a 10" side wall
that would amount to a 40" combo with 20" wheels




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[*] posted on 10-15-2018 at 07:59 PM


Quote: Originally posted by 4x4abc  
for off road use tires should have about a 10" side wall
that would amount to a 40" combo with 20" wheels


You are then saying a minimum 35 inch combo for 15 inch rims? For competition maybe...but 34-35 will get you along on a 20 inch rim...33's on a 15 are great.
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[*] posted on 10-15-2018 at 09:21 PM


Low profile tires are the latest fad on trucks. People think it looks cool. If you want a truck to be a high performance speed machine then you shouldn't buy a truck, get a bmw or audi



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[*] posted on 10-16-2018 at 05:15 AM


It's not that easy guys - if you want a top line interior, full electronics and safety features in a 1500 body/frame, then it comes with fancy-pants 20" rims. Maybe just a west-coast thing? Oh, and $60k, sheesh.
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[*] posted on 10-16-2018 at 08:09 AM


Yes 10" is the goal for off road use. That is an agreed upon standard. 10" from rim to ground. Such as:
15" rim = 35" tire (the preferred setup for a Jeep TJ and many others)
17" rim = 37" tire (the preferred setup for a Jeep JK/JL 4 door)
18" rim = 38" tire
20" rim = 40" tire
Most OEMs have settled on 17" rim for their off road rigs. Such as a Ford Raptor. Larger rims equate to much more expensive tires due to limited production, especially for the bigger diameter.
Most off road prerunners are choosing the above 35x15" and 37x17" rims. Most full size racers choose bigger.
One can still buy a new truck with 17 or 18" rims even for the high end versions. Probably requires digging pretty hard to find those options, then special order. Example buy a Ford F350 off the lot then find take off 17" rims that were sold for work trucks and have them power coated to match the new truck. Guys do it all the time. Result is 37x17" tires. Not inexpensive, but technically correct.

If you test drive a new truck with 20" rims back to back with one with 17 or 18" rims on a wash board or a potholed road you will notice a big difference in the ride quality. Yes my new truck has the 18" ones. Saved money and got a significantly better ride. It wont be used for significant off road use because the tire diameter is only 32" (7" rubber to ground a compromise I can live with)
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[*] posted on 10-16-2018 at 08:23 AM


How do the class 11 VWs make it thru a race.
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[*] posted on 10-16-2018 at 08:59 AM


Quote: Originally posted by TMW  
How do the class 11 VWs make it thru a race.

low vehicle weight
engine weight on axle = more traction
trailing arm from suspension (wishbone)




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[*] posted on 10-16-2018 at 09:07 AM


Quote: Originally posted by PaulW  
Yes 10" is the goal for off road use. That is an agreed upon standard. 10" from rim to ground. Such as:
15" rim = 35" tire (the preferred setup for a Jeep TJ and many others)
17" rim = 37" tire (the preferred setup for a Jeep JK/JL 4 door)
18" rim = 38" tire
20" rim = 40" tire
Most OEMs have settled on 17" rim for their off road rigs. Such as a Ford Raptor. Larger rims equate to much more expensive tires due to limited production, especially for the bigger diameter.
Most off road prerunners are choosing the above 35x15" and 37x17" rims. Most full size racers choose bigger.
One can still buy a new truck with 17 or 18" rims even for the high end versions. Probably requires digging pretty hard to find those options, then special order. Example buy a Ford F350 off the lot then find take off 17" rims that were sold for work trucks and have them power coated to match the new truck. Guys do it all the time. Result is 37x17" tires. Not inexpensive, but technically correct.

If you test drive a new truck with 20" rims back to back with one with 17 or 18" rims on a wash board or a potholed road you will notice a big difference in the ride quality. Yes my new truck has the 18" ones. Saved money and got a significantly better ride. It wont be used for significant off road use because the tire diameter is only 32" (7" rubber to ground a compromise I can live with)


the move from 15" to 17" wheels was actually initiated by the off road racers - they needed bigger brakes for the increased horsepower
with that the tires went to 37"

similar development with many SUVs - more power = larger wheels
but same tire size
that lead to lower profile tires
loss of ability to air down
lousy off road performance

on many SUVs you can't fit any wheel smaller than 17" due to the brake size (in front)

the push to larger than 17" wheels in the private sector has only to do with optics




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[*] posted on 10-16-2018 at 10:29 AM


I know a lot of high-horsepower off-road trucks run on 42" tires which can reduce the chance of sidewall issues.






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[*] posted on 10-16-2018 at 10:44 AM


Quote: Originally posted by StuckSucks  
I know a lot of high-horsepower off-road trucks run on 42" tires which can reduce the chance of sidewall issues.




Looks like more than a few tire plugs to fix that one.

John
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