Tire Pressure for Partial Load

[WSea]

Alongside this subject has anyone found a good quick-connect tire chuck with a gauge and bleeder valve for the stock Rivian air hose?

I know you can set the PSI but I've found it to overshoot at least one tire every time I use it, sometimes by like 6psi. I'd like a quick easy way to bleed it off and watch the pressure vs having to drop it way down and try filling again

https://thorslightningairsystems.co...apid-4-tire-air-system?variant=43299566387456
easy way to get all 4 same psi In much faster time

this too with viair
https://thorslightningairsystems.com/products/thors-lightning-8-extension?variant=43301167005952

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[UnsungZero_OldTimeAdMan]

Alongside this subject has anyone found a good quick-connect tire chuck with a gauge and bleeder valve for the stock Rivian air hose?

I know you can set the PSI but I've found it to overshoot at least one tire every time I use it, sometimes by like 6psi. I'd like a quick easy way to bleed it off and watch the pressure vs having to drop it way down and try filling again

4-tire inflation systems are the way to go. Since you can inflate/deflate all 4 at the same time and automatically equalize between all 4. But, if you are seeking single tire gauge with quick disconnect chuck, for single hand operation, I’ve not come across any. However, it possible to build your own with components. Just need a gauge with 1/4” NPT fitting, a 1/4” NPT fitting with release valve, a section of hose with the right 1/4” NPT ends and a quick disconnect chuck to attach to one end of that hose. JACO makes a good one. They supply the one included in your air hose kit, but with 1/4” NPT male end. If you install a 1/4” NPT Milton M style female QD at one end of the hose (just like the QD fittings on the Rivian hose) you can just use the JACO schrader chuck that came in the Rivian kit.

Or, if you can find a gauge with release valve and fitting, add this from JACO.https://a.co/d/baUXjSY

 

[HaveBlue]

If the tire supports 2500 lb at 50psi, that's 10000lb of weight they are rated to carry (equally distributed). If the car weighs 7000lb, you could inflate to 70% and still carry the weight; 35psi. Don't load the car up over that weight or they will overheat on the highway. This is likely why 35psi is the recommended off-road pressure by rivian.

2500lb at a recommended 50psi infers a 50 sq in contact patch 6x8" roughly. Lower the pressure and the contact patch has to get bigger to carry the weight. At 35psi you need 70sqin and the tire gets flatter on the bottom. That means at speed, more bending of the tire which is more heat and less tire life. At lessor sub-optimal pressures the tire contact patch sits poorly and wears unevenly. The pressure needs to be adjusted for the weight of the car based on the contact patch you need. This could be higher or lower.

 

[HighVoltOverland]

Alongside this subject has anyone found a good quick-connect tire chuck with a gauge and bleeder valve for the stock Rivian air hose?

I know you can set the PSI but I've found it to overshoot at least one tire every time I use it, sometimes by like 6psi. I'd like a quick easy way to bleed it off and watch the pressure vs having to drop it way down and try filling again

I cobbled one together from HF parts, it has like 20 bucks

 

[HighVoltOverland]

I also just keep my 20's at 50PSI cause it's easier to see on my analog pressure gauge.

I fill with78.08% nitrogen too....

I always thought the cost was for the cool green caps

 

[CrazyOne]

I don't have great evidence for this, but lower underinflated tires tend to hydroplane more. When we decrease pressure contact larch increases. I am running 50 -51 for winter. Will go back to 48 in summer. The highway pressures(warm tire pressures?) in both cases will be around 51-52.

 

[HaveBlue]

Good point. Lower pressure, more contact patch, more floatation.

 

[topracer]

I am finding the R1S 21" riding on 48 psi cold to be very rough/bumpy. Using the following air pressure calculators by vehicle weight don't come near 48 psi Rivian has recommended. I would like to lower the air pressure for a more comfortable ride. I am riding on 43 psi cold at the moment (~45 psi warmed), and been thinking to lower even more.

https://overlandracksontario.com/blogs/blog/tire-pressure-calculator
https://www.auscamping.au/tyre-pressure-calculator-vehicle/

 

[HaveBlue]

That's true. The absolute minimum weight capacity is 35psi. 7000lb/(2570lb*4)*50psi = 35psi YMMV However, our GX470 weighs 5000lb and wants the tires at 35psi for the best ride and performance. Translating to the Rivian at 7000lb/5000lb*35 = 49psi though.

 

[usofrob]

Linking to a post where I provide the equation for the Rivians for E rated tires (80 PSI):
https://www.rivianforums.com/forum/...h-48mm-offset-from-tirerack.19135/post-421686

 

[R1Thor]

I am finding the R1S 21" riding on 48 psi cold to be very rough/bumpy. Using the following air pressure calculators by vehicle weight don't come near 48 psi Rivian has recommended. I would like to lower the air pressure for a more comfortable ride. I am riding on 43 psi cold at the moment (~45 psi warmed), and been thinking to lower even more.

https://overlandracksontario.com/blogs/blog/tire-pressure-calculator
https://www.auscamping.au/tyre-pressure-calculator-vehicle/

Those formulae are generic oversimplifications for how to estimate a *starting point* to find optimal tire pressures.

A vehicle is Engineered for driving dynamics, with multiple parameters that require solved for in order to meet OEM specifications. THAT specification is what's pasted inside the drivers door.

Minimizing years of Engineering of the R1 to two equations you just found on the internet and plugged some numbers into is nonsense.

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