Can 2.1 psi make this much of a difference?

I don’t know. Thanks for your observation. However, please tell me how you are measuring accurately to 0.1 PSI?

 

Just the readout on a digital tire pressure gauge, you know, a good one from Harbor Freight But I did back it up with the bike read out. Watching the tire pressures during my last couple of rides it seems as though you can fluctuate the front tire pressure by shifting your weight for and aft in the seat without much of a change in the rear. Reinforces my theory that the front end is "light" going down the road.

 

Just because a tire gauge reads to 0.1 does not make it that accurate. Precision and accuracy are two different things.
The K1600 dash readout only displays whole PSI, but the numbers on the NAV VI will indicated to 0.1. The dash readout will display “42” even when the NAV VI is indicating 42.9.
So who can explain that? Is the bike feeding ‘42.9’ accuracy to the NAV VI (which is able to display that 0.1 precision) and the bike itself is unable to display it, or is the NAV VI just making things up? Why doesn’t the bike round up a (supposed) 42.9 and display 43?

 

Can 2.1 psi make this much of a difference?

Absolutely. A change of 2.1 PSI is pretty decent, and enough to feel. You could experiment and go 2 PSI in the other direction and make notes of what that feels like. For most motorcycles, experimenting with pressures based on load, temperature, distance, altitude, and type of riding is normal and encouraged. If something works better for you and is within reason, by all means, do it.

The K1600 dash readout only displays whole PSI, but the numbers on the NAV VI will indicated to 0.1. The dash readout will display “42” even when the NAV VI is indicating 42.9.
So who can explain that? Is the bike feeding ‘42.9’ accuracy to the NAV VI (which is able to display that 0.1 precision) and the bike itself is unable to display it, or is the NAV VI just making things up? Why doesn’t the bike round up a (supposed) 42.9 and display 43?

The original poster's signature says he's on a 2022, the readout of tire pressure on the dash is in tenths. For the rounding down on older bikes, I'm sure the sending unit is giving precise information, and the display software drops the decimal altogether. I don't think the Nav unit is making anything up. Not sure what the reasoning is behind that, but maybe to keep the rider from calling the dealer about fluctuating tenths on the display?

 

Half of the problem is the stock Metzlers. 2PSI can and will make a difference and if you think it makes a huge change, then you found a great solution for you.

 

I agree. While I was never happy with the Metzler or Bridgestone tires for that matter. 2 psi can make a world of difference.

 

There is something weird I ran into with regard to tire pressure... I just went thru a DIY tire install. The tires I retired were slightly feathered on the front. I remember not being happy with RS4's being first put on, we have grooved roads (I think that's what it's called) in parts of SF Bay Area, I thought the RS4's were being sensitive to it. I also noticed that the tires were a bit low (~1.5psi) but I didn't think enough to worry about since tire pressure fluctuates. After about a week, I went and checked tire pressure and my motopump read 39psi. After I brought it up to proper pressure, I took her out for a short road test and it was like night and day. Then, I remembered a thread I read mentioning that tire pressure changes after an install, so on this tire change I checked it quite a few times and it seems to have leveled off.

IMHO, I think the TFT numbers have to be taken with a grain of salt. I believe my TFT reads a bit high. Early in the morning at the start of a ride, it will read low. As the miles tick off, it'll start to rise and fall within a range of 1.5psi. My recommendation is to set it to a known truth and observe how it behaves. Somewhere buried in the collective here, someone mentions that the TFT does a little translation for temperature, so I'm blaming this wizardry for a bit of translation error. YMMV

 

Yeah, I prefer to hit my target cold pressure numbers before a ride with a quality gauge that calibrates for ambient temp and pressure. I trust that method and it works for me.

 

I may be wrong (don't tell my wife), but I believe BMW calibrates the TPS to bars, down to one decimal place. This makes 100% sense with the bikes from Germany. That significant digit is kept in the conversion to psi.
So 2.9bars = 42.1psi and the next increment 3.0bars = 43.5psi. This explains the 1.5psi variance.

 

Your secret is safe with us... Alright everyone, we know whose buying our next case of oil. 🤣