BajaNomad - Airing down w/ 20" rims

Airing down w/ 20" rims

Santiago - 10-15-2018 at 07:04 AM

New trucks seem to come with 20" rims now, anyone have issues airing down with them?

bkbend - 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.

John Harper - 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

advrider - 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..

David K - 10-15-2018 at 08:36 AM

No bling in Baja!

BajaTed - 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.

bajatrailrider - 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.

willardguy - 10-15-2018 at 03:48 PM

half tire wheel rule.......got 40's?

norte - 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.

4x4abc - 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

4x4abc - 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

norte - 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.

mtgoat666 - 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

Santiago - 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.

PaulW - 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)

TMW - 10-16-2018 at 08:23 AM

How do the class 11 VWs make it thru a race.

4x4abc - 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)

4x4abc - 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

StuckSucks - 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.

John Harper - 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

StuckSucks - 10-16-2018 at 11:40 AM

Quote: Originally posted by John Harper

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

John

Low tire pressure, eh?

TMW - 10-16-2018 at 12:10 PM

How many race vehicles run a tire within a tire. The Herbst use to on their Trophy Truck.

David K - 10-16-2018 at 12:42 PM

Does anyone here remember the tire advertisement (Sears?) where there hammered a bunch of nails into a tire and then ran the Baja 1000... and it never went flat?

Let me do a Google search...

Haven't found the nails one, yet...

Here's the Sears "tire the beat the Baja" ad from 1971...

bajatrailrider - 10-17-2018 at 07:02 AM

Quote: Originally posted by TMW

How do the class 11 VWs make it thru a race.

. Dang tmw you know the answer engine in the back . Even with bald tires does well .

surfhat - 10-17-2018 at 08:47 AM

I have had Goodyear Silent Armor 10ply tires on my van for the last 7 years or so. No sidewall cracking. 35,000 miles and counting with half of the tread depth remaining. Never a failure of any kind. I do rotate all five [spare] yearly. I also run less pressure than called for by the label on the inside of the drivers door. 70 to 80 rock hard beating to death, no way. 50 front 60 rear and even wear across the tread.

The original attraction that sold me on these was:

Kevlar is stronger than steel. All the better for airing down when needed.

Kevlar runs cooler than steel.

Kevlar runs quieter than steel on the highway where it matters.

I am guessing at this rate I should get 50,000 miles, unless a blowout changes my mind before then.

This is on a 2 wheel drive and predominately on paved roads, but when in Baja trying to dodge the road failures and bouncing around off pavement and getting air repeatedly for hours on end without a hitch, I cannot complain.

I haven't heard how others rate these or how many miles others have gotten out of them. The KO2's seem to be the favorite lately and I assume for good reasons.

I would buy these again.

None of this relates to off road racing, I assume, but stronger than steel has an attraction that is hard to beat.

4x4abc - 10-17-2018 at 10:43 AM

advertising is just another form of lying

The tread is comprised of five plies (two plies of polyester, two plies of steel, and one ply of aramid (Kevlar)) while the sidewall is two plies of polyester.
Even though the sidewall has only 2 ply, it is stiff as a cardboard. 3 thin, flexible layers can give you more flex than 2 inflexible layers.
Quiet and durable for pavement - a disaster in snow and mud. Bad off road.

basautter - 10-17-2018 at 07:18 PM

This has probably already been communicated, but tire air volume is really important if you want to go off-road. With large air volume, you have the option to air down and get the effect of really soft suspension for short travel. It works great for traction and chatter bumps on dirt roads. Same goes for trailers. Deflators and a good 12V compressor makes this easy. I would not go with more than a 16 inch rim myself. If a new truck comes with more than 16 inch rims, I would sell them and get 16s. My 2 cents with thousands of off-road miles :bounce:

AKgringo - 10-17-2018 at 08:23 PM

Quote: Originally posted by basautter

I would not go with more than a 16 inch rim myself. If a new truck comes with more than 16 inch rims, I would sell them and get 16s. My 2 cents with thousands of off-road miles :bounce:

As mentioned earlier in this thread, clearance around the brake calipers may not permit running a smaller diameter rim. Offset may be a problem as well.

[Edited on 10-18-2018 by AKgringo]

Ken Cooke - 10-19-2018 at 08:08 PM

Airing up my 35" tires on obsolete 15" wheels :light:

PaulW - 10-21-2018 at 07:03 AM

12.5x15 are still available, but not the name brands because the name brands have moved on to the more popular 17s and other bigger size that new rigs come with.
And yes the 15s do limit the brake rotor size. Make brake upgrades, doable, but quite limiting.