Adjusting Tire Pressure for the Cold
 

This forecast has me planning for the weekend

https://cimg3.ibsrv.net/gimg/bikefor...1637862578.jpg


https://cimg8.ibsrv.net/gimg/bikefor...9f6e80de87.png


https://bikerumor.com/2015/01/08/tir...d-this-winter/

Throw out the table.
If you have deep snow, sit on the bike and adjust pressure to have 2 wrinkles (or more if you really need more float). On non-deep snow, have enough pressure to not have wrinkles, but little enough for the tire conforming well to the ground. On pavement, have pressure above the point where you have noticeable more drag.
This algorithm was developed to account for weight, tire material and suppleness, tire width, rim width and temperature. It calculates optimum pressure for the conditions at hand.

IMHO - The chart is a helpful starting point when your fattie lives in the basement and you'll ride to your local trails. I'll always start with too much pressure because dumping pressure is much easier than adding pressure with a compact hand pump.

I take my fattie outta the basement and ride to/from the trails - I almost never haul my bike on the car. If your driving a bike around, the above segment doesn't really apply to you.

The thumb and wrinkle stuff it OK for many riders, for me, I track my pressure in a spreadsheet (nerd emoji) to help me dial in the pressure with less messing around while out and about. Again, this is only helpful when you ride out with a bike that just left a warm house/garage.

An additional (afterthought), the wrinkle rule works with high quality, high TPI, high $$$ tires ... not as helpful with more affordable, lower TPI tires.

Winter pressures are truly more complex when you ride more than single-track trails and similar conditions. I ride my fat bike on the roads with bare pavement, on plowed rail-trails with snow pack and ice, on icy lakes with drifts, in addition to snowy single-track trails.

Most of my winter riding is on streets or bike trails where I run 7 and even higher. On the single track it's 2 to 5 depending on conditions. I prefer to find the sweet spot and get a reading on the gauge to repeat it later. I also use a torque wrench.

I'm in agreement with throwing out the table. Doesn't take into account rider weight or trail conditions. I use the "squeeze the tire good 'nuf" method.

That and my fat bike lives in the garage so I don't have the temperature differential to deal with. Actually read somewhere that bringing a bike in out during winter causes condensation build up which may rust some parts on the bike.

It's not intended to consider your weight or trail conditions :twitchy: where do people get this idea? Did you look at the chart, honestly?!?

The chart is showing the difference of pressure at different temps. You need to know your pressure for your weight and the trail conditions ... I hope you can handle that. Repeating my earlier post, my bike lives in the basement and I know the pressure I want outside when it's -15F, and I use this chart to set the correct pressure in my basement. Again, repeating, I ride my bike outta the house, I'm not carrying a floor pump and it'll take a few miles for my tires to drop to air temp. If you drive to your local trails - your tires will be at temp when you arrive and you likely have a floor pump with you too, cool! You don't need this information ... just move along. :thumb:

For years, my winter bike lived in the garage and this chart wasn't needed. My current detached garage is as secure as a screen door, so my bikes live in the basement. Bikes stored inside really don't have any worse issues with corrosion. Simply be sure the bike can thaw and dry between rides. We're all riding through the same road salt and crap. I clean my winter bikes the same now as I did at my old house, typically a quick wash once a month and deep clean in the spring. After 1,000s of winter miles and roughly 10 Minneapolis winters, my winter bikes wear out parts at about the same frequency as my summer bikes. No big deal.

Which is what makes it useless chart for most to use. If my bike was stored inside at 70 degrees and my tires are at 10 psi it tells me that at 10 degrees my tires would drop to 7.2 psi. Now lets say I get to the trail and it's soft conditions after recent grooming. If I'm a 225 pound guy I'm probably going to have to lower the pressure so I don't put ruts in the trail. If I'm a 165 lb guy the pressure is probably OK where it's it and then there is everything in between. Now if I get there and the trail is hard packed maybe the tires are ok where they are or a little air could be added.

Then there are other variable that chart doesn't consider...are the tires 3.8" wide or 4.6" wide? Are they 26" fat or 27.5" fat?

Really too many variables between temperature, rider weight, tire width, tire diameter and snow conditions to make that chart worth while. It's easier to pump the tires up to about 10 psi before leaving home and then decide to leave alone or let more air out once the destination is reached.


https://cimg6.ibsrv.net/gimg/bikefor...1994d96c3d.jpg

This chart is to convert a pressure from an indoor temp to an outdoor pressure, that's all, end of story. You need to know a target pressure for the conditions you'll be riding, but I said that in my last post.

Fun fact, not every single person rides a fatbike exclusively on groomed trails 🙄. Rules for tire pressure on groomed trails don't apply while riding on ice, hard pack, or hardpackedice. Look at the OP, we are not talking about a 10* change in temp, we are talking about 70* to 80* change in temp. Sunday morning, I rode out with temps around -15F on a 30+ mile ride on ice covered plowed trails. I needed a higher pressure so the studs could bit into the bulletproof ice, so you're repeated posts about riding groomed trails aren't worth while.

Your arguing about something totally different, this pic is for your conversation:


https://cimg7.ibsrv.net/gimg/bikefor...9774961301.jpg

Your point is not *wrong*, your point is simply in the wrong thread. If you have nothing to add to the conversation about the change in fat tire pressure when taking a bike out of a warm space in to a very cold place, move along. kthxbye!

I know what the charts for. But don't think its very useful for anything including the type of riding you describe.

I guess the geek in you makes this worthwhile.😁😁😉😉😉

My friends and I have done similar riding but never referenced an indoor/outdoor tire pressure differential chart.

I was gonna say a pressure differential chart isn't rocket science, but I guess it actually kinda is.

A person can make this as complicated or as simple as they want.

One thing I left out of this discussion is none of these damn guages we have available are correct. I have three of the fat bike Accu-Gauges and two Joe Blow Fat pumps that have a gauge on them. All 5 of them read something different. When one of my Joe Blow Fat pumps reads 10 psi, one of my "accu-guages' will read 5 psi. So now how does one use that chart and come up with the correct number?

When I do use a guage (which isn't very often), I've settled on one guage that I've marked with an X using a black magic marker. That way I have a constant. I know what "my numbers" need to be on that gauge for certain conditions, but I also know "those numbers" are not accurate. Kinda the reason I just use the squeeze method the most often. It doesn't really matter what number shows up, so long as you have the same gauge, all you need to do is find the number which works for you and stick to it.

When fine-tuning the tire pressure, focus more on feel than the actual number. Most people are swaying too far away from the ideal PSI anyway, so it isn’t an issue.

https://fatbikeplanet.com/determinin...for-fat-bikes/

My comment was meant as a joke. Pressure charts are used for rockets...

One can assume that anyone that is nerding out on pressure charts is probably using the same gauge at both spots.

Personally I am a squeezer. I see what the point of the post was and I get it. I usually ride to the ride and usually just deal with what ever pressure makes sense for longest part of the ride.

Then the question becomes...Is that particular gauge accurate?

Does it matter? if its says 12 and 12 feels good then the pressure should be set to 12.

Its not a matter of accurate if you use the same gauge its a matter of repeatable. Repeatable is easy to figure out.

If you are expanding this past a solo record keeping thing to like everyone on the interwebs should do as I say in that case everyone needs accurate.

^^^ this

The chart in the OP doesn't tell anybody what the 'right' pressure is ... but if I know that I'd like 8psi for a plowed trail and it's -15*F outside and 60*F in the basement, I'll want to start with 12 psi. I know from past rides that *my* gauge reads 8psi and that works for me and the conditions, but I have not calibrated this gauge (and dropped it a couple times), so I'll likely get a different reading with a gauge at the shop ... but that doesn't matter does it.

If you're gonna argue against gauges because they are inaccurate, but promote 'thumb' and 'feel', you're being a little hypocritical. Both have one thing in common, it's all rider-specific.

If one is inclined to use a gauge all the time then precision becomes more important than accuracy.

Hey there Mr toad, just wanted to say thanks for the temp difference chart, very useful and straightforward , as our bikes start out room temperature ish.
Especially for a new guy to the whole really low pressure thing and big volume tires.
Already found it useful when going out to -6c and starting to experiment with different pressures for varying surfaces.
I got a new gauge, 0-15, and figure I'll use this chart to target tires for 10psi cold, and then once on trails and cooled down, burp down bit by bit to pressures suitable for the conditions.
In riding at all temps summer or winter, I like trying out different pressures for different ride feel, with different weights (touring) and surfaces, so I imagine it won't take long to get a feel for fat tire snow stuff.

thanks again for this reference

Clearly, some people in this thread completely missed the point of the chart.

Rather useful, IMO.