tire pressure

Forums Mountain Bike Forum tire pressure

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  • #261624

    I am looking to for general guidance on tire pressure. I have rode bikes all my life. As a kid we always pumped our tires up tight and generally kept them that way. When first started mountain biking a few years ago that is the attitude I took and rode that way. Probably cost me a few flats. As I became more knowledgeable and experienced I have backed off the pressure. I see videos and hear of guys riding 20 psi and lower. I have ridden around 20 psi and it always feels like if I got to rowdy I would damage my wheel. I am 6’1″, 220 lbs, so I am a load. I have found that I feel more comfortable around 30 psi getting some firmness but still having some give for traction and some shock absorption. This is what I ride on a 29er with 2.4″ tires on a hard tail. I also currently got a 27.5 hard tail with 2.8″ tires. I have not messed much with the pressure at this point. Still getting a feel for the bike and new size tire and wheel.

    I have been told there is are so many factors to take into account to include: wheel size, tire size, hard tail vs full suss, terrain, style of riding, weight of rider, rim width, and so on. I was wondering if there was wondering if the was some general guidance out there to help find a starting point for tire pressure. Something where you take in to account rider weight, tire width and wheel size to keep it simple.

    Any advice or guidance that might get me close to a good psi?

  • #261676

    I’ve only been riding for about a year and a half, but I did go lower tire pressure when I switched over to tubeless. Yes, weight, terrain should be in the calculation. I’m 5’7″, around 153-155, I like around 22-23 psi, running 29 x 2.6 tires. Maybe start around 30 psi, ride some trails, and see how it feels, lower pressure or increase and ride same trails and see how it feels.

  • #261678

    Always a good question and I suspect you’ll get some really good input.  Lots of factors obviously.  Check out this vid:

    https://www.singletracks.com/blog/mtb-videos/video-tire-pressure-for-mountain-biking-how-to-set-your-pressures-for-enduro-dh-and-xc/

    FWIW, I run tubeless and prefer lower tire pressures to give me what I feel is the best balance of speed and traction.  On my FS 29er with 2.35″ tires I run 18F/20R PSI.  On my 29+ hardtail with 3.0″ tires I run 12F/15R PSI (even lower in snow or muddy conditions).  I’m about 185lbs with gear.

  • #261693

    Appreciate the thoughts and video. I am interested in any other thoughts or advice there.

    I watched the video rmap 01 and found it amusing the three disciplines and if you paid attention all of them had tire pressure really close to others. I think they thought there was going to be a drastic difference and there just wasn’t. I can also look at all those guys and see I am significantly bigger. I was surprised that the tire pressures were higher than I expected especially with so many others I hear saying 20 psi and lower.

    It appears 30 psi is a good starting point and if it works and is comfortable then leave it be. If it ain’t broke…

  • #261701

    Your points are well taken.  If you really want to know what works best for you start out with a known tire pressure (say 30 PSI in this instance) and then slowly let air out (1-2 PSI at a time) at different points during the ride to see what feels best.  You can then check the pressure at the end of the ride to see where you ended up.  Even better if you have a pressure gauge with you so you know exactly what you’re running at any one time.

  • #261724

    Tire pressure depends on many things. Total weight (bike, rider, and gear), tire width, rim width, tire casing, trail conditions (rocky or smooth), and personal preference.  In general, you want to use as little pressure as possible while avoiding low-pressure tire side effects.   Your first and most important concern is to avoid rim strikes.  If you hit square edged rocks and deform the tire so much you get a rim strike, you could damage your rims.  With tubes this would likely lead to a pinch flat.  Set up tubeless, you might not flat but you would still be rim striking.   Once you’ve got enough pressure to avoid rim strikes, you would also want to avoid sqirm, wallow, jiggle, auto steer, and pogoing.

    I ride 2.8 tires on i35 rims.  Anything above 12psi, no rims strikes.  Anything 15psi or below, the bike pogoes.  16psi feels better.  17psi feels best, no pogoing but the tires are still compliant.  18psi, the tires feel too hard.

    So, you’ve just got to try different pressures until you get it right for you.  Also be aware, that you might not want the front and rear tire to have the same pressure.  Usually less pressure in the front but not always.  Given your weight, I going to guess about 18-22 psi on the 27+ tires.   There is no point in using Plus tires if you over-pressure them so try to use just enough air.

  • #261741

    I’m your weight and have been riding for 25 years. With regular volume tires (around 2.3-2.4 width) I’m around 30 in the rear and 3-4 psi less in the front. You have to keep in mind you need a certain pressure just to support your weight (all other factors coming secondary to this). If you find that you’re having issues with traction or tire squirming I’d look to the tire itself after you figure out what pressure is good for your weight and speed. If you need more then 30psi then you need a stouter tire (heavier duty casing). People that are running near 20 are either light weight, not riding aggressively, on high volume tires or all of those things. If you ride hard and fast over real terrain (with 20psi) and weigh over 200lbs you will blow up your wheels if you can keep the tire on the rim long enough to allow it.

  • #261743

    As a lot of people mention, there are a lot of factors. One of the biggest is whether you’re running tubeless or with tubes and since you didn’t say one way or another in your post, I’m surprised no one who replied asked. Maybe I missed it.

    I’m still running with tubes (I don’t know why…too lazy to change from what I’ve always known, I guess) and I have pressures closer to 30 psi than to 20 psi on 27.5 / 2.8 tires (Maxxis Minion DHF front and Maxxis Rekon rear). Whenever I try to go lower than 28 or 27, I almost always get a flat with my rear wheel as soon as I hit a drop. I will admit, though, I don’t pay that much attention to the numbers. I usually inflate the tire pretty hard, like I also used to as a kid, then adjust by letting out air as I go based on feel, since trail conditions can change from day to day.

    It probably also matters somewhat where you ride. The general trail characteristics of, say, Arizona vs Florida vs New Hampshire are all going to be pretty different and require slightly different ideal set ups.

  • #261752

    When Stan’s started making tubeless rims, they used a pretty good formula that you can still use as a starting point.

    Riding weight in pounds divided by 7 = X psi.  Front: X – 1 psi, Rear: X + 2 psi

    At 220 pounds, you would start with 30 psi front and 33 psi rear.

    I would start there and drop 1 psi each ride until you find the pressure that works best for you.

     

    This formula came out when tires and rims where a good bit narrower so don’t be surprised if you end up several psi lower.

  • #261753

    Great feedback from the field! Thank-you.

    Charding: Good point on tubes or not. Just converted to tubeless last year and notice just on feel alone I can go lower on pressure.

    dlawson: That is a great formula as a starting point. There are so many more factors especially with rim widths, tire sizes, wheel sizes, tire casing and so on. That formula or something like it is what I was looking for.

    Would love to see this topic commented on more as it may help newbies out there figure this stuff out. A lot of stuff on YouTube yet most of it I don’t see anyone talking about their weight. Feel like that is probably the first and most important factor in the equation.

    Thanks again for all the input.

    • #261774

      Like others have said, find your sweet spot based on what you like and feel good with.  Beyond that, I sometimes make adjustments specific for the type of trail.  I also adjust for altitude when traveling, although likely not necessary (just in my head 🙂 ).  I like my tires around 28 lbs for most of the trials I frequent.  I come in at 165-170 loaded, 32 lb bike, 27.5×2.4 with tubes.  But, I have found that different brands and models of tires have a different sweet spot for me.  For me, I run WTB’s  at the lower end (25-28), Maxxis at the higher end (35+), with Kenda’s in the middle (30-32).  I feel like sidewall strength and stiffness drives pressure to some extent (stiffer sidewall = lower possible pressure).  Just my unscientific opinion.

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