Changes to throttle behavior, cruise control and regen since 2025.22.01 (Gen1)

[diranged]

This is an information gathering thread ... I'm not sure if there is an issue with my vehicle specifically, or a broader issue. My vehicle is a Gen1 R1T Quad (vin 24xx).

Back Story: A few weeks back when the 2025.22.01 release came out, I happened to get it the exact same day that I got new tires. I replaced my ~25k old Pirelli's with Toyo Open Country A/T III EV tires. These tires are ~10lbs lighter than the stock tires, but are the same dimensions, so I did not do any reprogramming of the computer.

Within a few hours of both of these changes happening, I went on a road trip and started to notice differences in the driving behavior of my truck... I've spent a few weeks now trying to catalog these differences, and I just got back from another road trip where the changes were really pretty dramatic.

Below is a list of the behavior changes I've felt... and I am really just trying to see if anyone else has noticed changes similar to these recently or if this is specific to my vehicle.

New Tire Details:
TOYO TIRE
OPEN COUNTRY A/T III EV
275 /65 R20 116H SL BSW

Driving Changes:

• Cruise Control: Cruise Control is now awful, and nearly unusable. In pretty much any situation, it feels like the car is just learning how "one pedal driving" works and is constantly adjusting the throttle input, causing the car to jerk forwards and backwards almost non-stop. The inputs to the throttle are subtle, but enough to make me almost sick. This is the most dramatic change to the driving behavior I've noticed.
• Regen -> Physical Brake Transition Smoothness: In the past, the transition between motor regen and physical brakes operating has been so smooth that I couldn't ever tell when it was happening... now I feel like the motor-regen isn't as strong as it once was, and then when the physical brakes kick in it actually feels as if I put my foot down onto the brake pedal suddenly. This was particularly noticeable on a long downhill from Tahoe today.
• Coasting Downhill to Acceleration: While coasting downhill from Meyers to Placerville, I noticed that if I wanted to increase my speed slightly (again while coasting downhill ... so lets say going from 55mph and deep in the regen, to wanting to go 57mph) the behavior felt weird..in the past I feel like it would have just reduced the regen and let the car naturally speed up, but now it was suddenly jumping to acceleration mode from the motors (orange on the throttle indicator on the dash), and accelerated much more quickly than I expected.

All in all, the "smoothness" of the power delivery really feels gone now... I feel like the car is constantly accelerating and slowing down. The transitions during braking are so unpredictable now that my thought I forgot how to drive!


Theories on the change

a) The software update included some changes that were not documented (https://riviantrackr.com/2025-22/).
b) Could the 10lb tire weight change be significant enough that the computers calibration on how hard to brake, accelerate, etc has changed?

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[Davethadog]

Dumb question but have you tried turning it off and back on again? Even when I swapped my 21” wheels for 20s with larger tires I didn’t experience anything as dramatic as what you’re describing.

 

[VSG]

Or perhaps your calipers are partially stuck closed, dragging.

I have a Gen 1 R1T Quad too and I haven't had any of those problems in the 1 month+ since the update (or before ...)

 

[diranged]

Dumb question but have you tried turning it off and back on again? Even when I swapped my 21” wheels for 20s with larger tires I didn’t experience anything as dramatic as what you’re describing.

I have not done a full hard reset - not a bad idea though...

Or perhaps your calipers are partially stuck closed, dragging.

Possible - I thought about that, but it doesn't quite line up with the behaviors im feeling... but definitely possible.

 

[UnsungZero_OldTimeAdMan]

Many have changes tires and not report these experiences. I'd bet on pure coincidence. Hard reset. How did you come about this 10 lb figure? Toyo site shows their SL tire to be 42 lbs. TireRack and Discount Tire list the factory Pirelli AT at 48 lbs. Weight of tires, from one set to another, shouldn't affect how software manage power output and regen.

 

[diranged]

How did you come about this 10 lb figure?

I may have mis-remembered, I thought the Pirellis were around 52lbs.. but either way, I agree that the weight difference didn't seem like it should cause any changes. I've done a hard reset, but I probably won't be back on the freeway for a few days, so I'll have to see how it feels later in the week.

 

[UnsungZero_OldTimeAdMan]

I may have mis-remembered, I thought the Pirellis were around 52lbs.. but either way, I agree that the weight difference didn't seem like it should cause any changes. I've done a hard reset, but I probably won't be back on the freeway for a few days, so I'll have to see how it feels later in the week.

Nope. 48.

 

[Ric G]

Also consider 48lbs new. So, a bit lighter after 25K miles of wear.

 

[diranged]

So ... after a while, I have an update. While driving back from Tahoe on a long steep downhill, I finally thought to check out the vehicle/motor info page while these regen-braking issues were happening. Low and behold, my rear-two motors are engaging intermittently and sometimes disengaging during braking events. Below are some screenshots of videos I took.

I ended up dropping the car off at Rivian on the way home from this trip - but the tech's initial impression was that my rear motors are bad. :/

 

[Dark-Fx]

New Tire Details:
TOYO TIRE
OPEN COUNTRY A/T III EV
275 /65 R20 116H SL BSW

I'd be looking at the rear tires to see if they are actually different sizes. I've never noticed anything different in pedal feel going from light to heavy tire, it's more about vehicle responsiveness.

 

[diranged]

I'd be looking at the rear tires to see if they are actually different sizes. I've never noticed anything different in pedal feel going from light to heavy tire, it's more about vehicle responsiveness.

hah .. no. all my tires are fine and new. rivian agreed after looking at it, something is definitely wrong with either some calibration issue, or the motors themselves. i expect to find out this week what the next steps are..

 

[Dark-Fx]

hah .. no. all my tires are fine and new.

So you checked then? That tire comes in lots of sizes. Wouldn't be the first time a tire shop messed this up.

 

[diranged]

So... turns out @Dark-Fx was absolutely right to tell me to check the tire specs more carefully. Rivian finally figured it out - the tire shop installed the wrong tires. I specifically ordered the non-LT version (275/65R20), but they mixed in LT tires on two of the wheels.

Here's what they actually installed:
- Front-Left: LT275/65R20 (the heavy duty one - 55 lbs, 16.4/32" tread depth)
- Front-Right: 275/65R20 (what I ordered - 45 lbs, 13.5/32" tread)
- Rear-Left: 275/65R20 (what I ordered)
- Rear-Right: LT275/65R20 (wrong again)

So yeah, diagonal mismatch. And honestly, who checks all four tire sidewalls after installation? The tread pattern looks identical, they're both Toyo Open Country AT III EV tires... you kind of assume the shop installed what you ordered.

The LT tires are literally 10 pounds heavier per tire and have way more tread depth. They also have stiffer sidewalls, which means under load they don't compress as much as the regular ones.

I threw together a quick comparison to show what this actually means:

Tire Type	Diameter	Tread Depth	RPM @ 65mph	Notes
Pirelli (original)	~34.1"	~11/32"	~640 rpm	What it came with
Toyo 275/65R20	34.1"	13.5/32"	~640 rpm	What I ordered - softer, compresses more
Toyo LT275/65R20	34.1"	16.4/32"	~637 rpm	What they installed - stiffer, stays taller

Basically at highway speeds, the LT tires were spinning about 3rpm slower than the regular ones. Doesn't sound like much, but with four independent motors each watching wheel speed constantly, the computer was losing its mind thinking there was slip or traction loss happening all the time.

That's why the rear motors kept cutting in and out during regen braking.

Good news:
- Rivian says there's no damage to the drivetrain
- They threw some stock tires on and took it for a drive - everything worked perfectly
- Tire shop is replacing all four tires tomorrow (with the correct ones this time)
- My motors are totally fine, just very confused

So ... @Dark-Fx ... you win, and apparently I'll be more carefully checking tires installed in the future!!

 

[diranged]

Update 2: Interesting interim test - front/rear mismatch vs diagonal mismatch

So while I wait for the tire shop to get the correct tires in, Rivian moved the tires around to at least match each axle. Now I've got:
- Front-Left + Front-Right: 275/65R20 (both non-LT - what I ordered)
- Rear-Left + Rear-Right: LT275/65R20 (both LT - the wrong ones)

Drove it home like this and... it's interesting. The diagonal mismatch symptoms are mostly gone:
- Left vs right regen differences disappeared - front axle regens evenly between left/right wheels, rear axle regens evenly between left/right wheels
- Cruise control is way less jerky
- No more of that constant back-and-forth acceleration feeling

But - the rear axle is still not happy. The rear motors are still intermittently cutting out during regen, sometimes not regening at all. So even though each axle is internally matched, the computer is still confused by the front/rear diameter mismatch.

 

[VandalSibs]

I was telling your story here to my wife, and we were trying to imagine what would have happened had you not been on a quad motor vehicle, or if you were in an ICE. My thinking is that things would have ended not as well.

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