When my tires wear this is on the list. I'm looking forward to your take on efficiency. What tire pressures are you running?

 

It varies a bit with temperature all over the map lately, but I try to keep them at 38-39 cold.

 

With about 56k miles on my Bolt, I just replaced my original tires with the same Michelin A/S tires from Costco. I felt a noticeable improvement in ride quality with the new tires. I don't know if that's just an emotional thing, or whether it's the due to the deeper tread on new tires vs old, or whether there is some difference between the OEM tires and the replacements. Back when I changed the oil in my ICE car, I remember feeling the engine ran smoother with the new oil - which I have a hard time believing to be really true. So maybe we all just want to feel an improvement after changing tires.

 

With about $56k miles on my Bolt, I just replaced my original tires with the same Michelin A/S tires from Costco. I felt a noticeable improvement in ride quality with the new tires. I don't know if that's just an emotional thing, or whether it's the due to the deeper tread on new tires vs old, or whether there is some difference between the OEM tires and the replacements. Back when I changed the oil in my ICE car, I remember feeling the engine ran smoother with the new oil - which I have a hard time believing to be really true. So maybe we all just want to feel an improvement after changing tires.

This is several pounds at each wheel and a massive difference is sidewall height, not just an oil change.

 

is there a table of what alternate rim sizes, widths, and ETs fit a Bolt along with preferred tire sizes ? My big SUV (2019 Ford Expedition Limited Stealth), I swapped from the stock /45 tires on 22" rims to /65 tires in 18" rims and the ride is way smoother on bad roads. Both tire sizes are exact same OD

 

I am unaware of such a table. My choices were based on the recommendations of others who have made the swap.

 

ok, well, what ET and width are the 16" rims people are using? What about the 15" rims? FWD cars are pretty sensitive to handling problems when the ET's are wrong.

 

I've been using 16" aftermarket wheels for snow tires with a 35 mm offset and 7" width. I've been using them on our Bolts since 2021 with no issues. These are Sparco Assetto Garas that I purchased back in 2011 for my last gasmobile now gone, Cruze Eco. Ideally I'd probably stay closer to the ET ( around 42?) of the stock wheels, but they've been fine. I use 205/60-16 Michelin X-ice snow tires on the wheels.

 

I've found Michelin tires still have that good ride and traction when they are 75% worn, while many others start to suck much sooner.

 

Wow, that is amazing that a 15 inch wheel clears the brakes and works well.
and doesn't look too bad either
Nice job.
I am curious about the efficiency gains ... there should be, just a matter of how much.

 

Looking forward to hearing your assessment! Even though mine is a 2020 EV, the ride is pretty stiff. Dealer told me that a rattle I hear after having the battery replacement was the rear shocks (even though it sounds like the back seat doesn't latch as tight) so have been looking for recommendations for replacement shocks to smooth out the ride, however so many folks say it is the tires. I don't like the idea of lowering the air pressure because I know what kind of hit you can take on range. I remember just changing tires on my Leaf to non-EV tires cost me over 20% of range and I think helped to wear out the battery quicker.

Best to you. 🤞for good results!

 

It’s too early for any broad conclusions, but I am encouraged by the consumption numbers on the DIC. With the OE tires and rims, in town driving occasionally went to 5-5.1mi/kWh. I am now seeing 5.5-5.6, numbers I have never seen in 3 years of ownership.

 

Note same-for-same new tires are always less efficient than worn tires due to the deeper tread. But smaller wheels should be more efficient

 

In addition to EE, I found this

 

It used to be that if an ICE car came with different wheel sizes (probably more common on pickups and 4X4s) you could just buy the matching speedometer drive gear (a tiny cheap plastic gear) and install it in the transmission

I believe manufacturers have to certify the accuracy of speedometers to meet some regulation, and they are allowed to read high (showing you are going faster than you are) by some % (10%?) but there is zero allowance on the low side - so they tend to be either accurate (possibly gps verified) or high. I think allowing user recalibration is probably not allowed under the regs

The digital display in my Honda always agrees exactly with the GPS speed display on my radar detector. I've not checked the Bolt, but it seems accurate compared to the Wyze display (I'm less confident in the app's speed accuracy)

 

German/Euro cars have strict speedo requirements to never display a slower than road speed, thus every German car I've driven in recent years displays 69 MPH when my GPS speed is 70 MPH. Thus, with tires down to the wear bars, they are still not going faster than the speedo.

jack vines

 

Speedometers aren't accurately calibrated, plus or minus 5 is pretty common and +-5mph at 50mph (10% as mentioned) is what I think the current law is in the US. They aren't set high or low on purpose and I didn't see any reference to high or low in the rules.

On older cars with an analog needle, even an electronically controlled needle, the speedometer and odometer don't always agree. The analog needle often points to a different value from what the ECU is reading due to the gauge aging or just starting out poorly. If the vehicle is new enough to have OBD2 you can check the speed with that.

Many trucks like Ram/Dodge have tire size adjustments in the ECU that can be changed with the factory scan tool. It makes sense, many full size trucks have different diameter tire options from the factory.

As far as I know there are no vehicles that use GPS to calibrate the speedometer. You don't want vehicle speedometers going crazy when you drive in low traction situations like snow and dirt and then transitioning back days later under normal conditions. Chrysler navigation radios at some point did calibrate their internal speed with GPS and use dead reckoning when the GPS signal is lost like when driving through a tunnel but that information was not relayed back to the ECU. It's possible some vehicles do this, I've just never seen it done.

 

Speedometers aren't accurately calibrated, plus or minus 5 is pretty common and +-5mph at 50mph (10% as mentioned) is what I think the current law is in the US.

I used to work for a company that made aftermarket gauges and the electronic ones were typically calibrated to within -0%/+1% at half of full scale with the reference signal. Some customers had different requirements but it's not hard to calibrate them accurately.

 

For sure tire wear, changes in temperature, changes in pressure, etc. will certainly throw off the calibration, but the calibration is usually quite accurate from the factory which is the best the engineers want to do with the budget they're given by the bean counters.

 

My Jeep has different size tires and I have an electronic calibrator from the speed sensor. I deal with day to day fluctuations in diameter and tires. I've also seen tons of clusters that are off by huge margins. I understand these arguments about how easy it is to calibrate and how best people can optimize this and that, all I know is what I've seen. I've seen pretty poor calibration but I understand others have seen decent calibration. Clearly some people have experienced much better precision than the spec, that's great. The acceptable spec is a full 10mph swing at 50mph from 45-55, let that sink in, that's for a new car.

 

GPS speed is quite accurate in a straight line averaged over a minute or so. Radar is accurate instantly, if it's properly calibrated. Automotive speedometers count wheel turns, which introduces a bunch of error.

 

IF it's properly calibrated...but would be interesting to see their calibration routine and what they calibrate to. Perhaps I'll Google it!

The analog wheel turn thing can work without power or anything else...so the old speedos just worked...and if you really wanted to keep it calibrated you could...but it sure would be a PITA! 🤣🤣🤣

 

GPS speed is essentially perfect as long as the GPS receiver is attached to the vehicle, in other words you aren't moving your phone around. The speed is required to calculate your position and is reported as a separate value, it requires no calibration. There is no way to calculate position from GPS satellites unless you know your speed and heading.

 

"There is no way to calculate position from GPS satellites unless you know your speed and heading."

If my GPS receiver can "see" the requisite number of satellites, why would it need to know my speed and heading (velocity) in order to determine position?

Velocity can be derived from subsequent GPS position readings, and/or inertial guidance (using accelerometers), depending on the sophistication of the GPS receiver.

 

I love this, It looks better than I thought it would, would love to hear more data & experiences. What PSI do you go with I would assume lower for the taller profile?

 

... remanufactured 15" Sonic rims and Hankook Kinergy ST H735 205/65 15" tires. ...

I think that was the stock size for my wife's former 1994 Mercedes E320 wagon, which rode like a limousine. ok, close, the MBz ran 195/65R15

 

Why are big wheels still cool when everyone has them? I want fat tires, no more scratched or broken wagon wheels.