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  1. #1
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    Proper tire pressure for 120lb girl?

    I believe that I may have been over inflating the tires on my girlfriends bike. She weighs around 120lb and rides a coil fork suspended 26" hard tail on 2.1 tires with tubes. She mainly rides tight twisty single track with hard pack and some sandy and loose sections. I've been inflating them between 40 to 50 psi depending on trail conditions, the same psi I run in mine and I weigh 100lbs more. What psi range is good for her weight and riding conditions?

  2. #2
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    You're way over inflating even your tires!

    She should be around 20-25psi depending on how big those 2.1's are.

  3. #3
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    Quote Originally Posted by One Pivot View Post
    You're way over inflating even your tires!

    She should be around 20-25psi depending on how big those 2.1's are.
    Whoa 20-25 psi? Thats waaaaaaay less than I thought. Her current set up is a 2.1 Maxxis Crossmark rear and 2.1 Maxxis Ignitor front. The Crossmark appears to be a larger volume over the Ignitor. If she continues to use the current set up (I may change them to 2.1 Performance casing Schwalbe Rocket Rons) should she run a higher or lower psi in the larger volume rear than the lower volume front?

  4. #4
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    The ignitor is a little small. I think my ex was about 135lb on her 2.1 ignitors. Ran them at 25-30psi with tubes without any issues at all. 30 was probably too high, but she didnt notice the difference between 25 or 30, so whatever.

    I run a small 2.25 and a small 2.35, between 190-220lb over the years. I run the rear at 25-28psi and front around 30ish, with tubes. Ive dented rims, but havent pinch flatted.

    Just try 25 and see how it goes. Rim width and style do play a big role in pressure too, I personally dont like to run pressure as low as humanly possible so I run more than whats probably necessary. The narrower the rim, the more pressure I want in the tire. 25psi should be good regardless of her setup, overall.

    Either way, her pressure needs to come waaaay down! Yours too!

  5. #5
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    I weigh 255 pounds and I run about 28 PSI in my tires, tubeless, 2.35 front, 2.25 rear.
    Generally, a larger volume tire would run less pressure.
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  6. #6
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    Guess I've been given some bad advice by a lbs I used to deal with. When I asked what psi I should be running in my stock tires, He suggested I started at 40-50 psi and adjust from there. This is what I've always went by never taking into account rider weight hence way over filling my girlfriends tires. Now I run a 2.1 Schwalbe Rocket Ron Evo front and Racing Ralph Evo rear which are much more compliant than my stock tires. I would imagine my weight (around 220) does effect the handling of these tires true? Wouldn't they tend to feel squirmy at a lower psi? Oh and correction they are 2.25 Rocket Rons I would be putting on my girlfriends bike so I take it those would require even lower psi? Just trying to grasp the whole psi to weight to volume thing.

  7. #7
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    I can only imagine how much more confusing this will be once I convert my bike to tubeless! Oh btw I ride a 26" hardtail if that helps.

  8. #8
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    Theres no magic formula or anything. Ive seen some light guys say they like 40psi. They've tried less and just like 40psi. Thats cool too. Most people will enjoy a lower pressure though, it rolls better and you get more traction.

    Try 35 on your next ride. Then try lower and see how it feels.

    I run my tires at a pressure I like. I *can* run lower, but its squirmy and I dont like it. Going tubeless wouldnt benefit me from a pressure stand point, I certainly dont want even squirmier lower pressure tires. They're fine where they are. Tubeless doesnt really change much unless you're flatting all over the place and not happy with the amount of pressure you have to run.

  9. #9
    Formerly of Kent
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    I'm 145-150lbs, and I ride 19psi front, 22psi rear, on Rocket Ron 29x2.25 and Renegade 1.95 (really a 2.0). Tubeless, of course.

  10. #10
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    Quote Originally Posted by CyclesnIPAs View Post
    I can only imagine how much more confusing this will be once I convert my bike to tubeless! Oh btw I ride a 26" hardtail if that helps.
    Read the tire pressure sticky on this board
    mtbtires.com
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  11. #11
    MarkyMark
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    My GF is about 120lbs and she used to pump her MTB tires up to ~40 psi. It took her a while to accept reducing the pressure to 30psi. Now we're down to about 20psi in the front and a bit more in the rear. It's less sketchy and it's helped her riding.

    I'm about 170lbs and run 25psi in the front (crashed a couple times due to tires burping on landings so I don't go lower) and ~30psi in the rear.

    BTW, F Ignitor and R Crossmax sounds like a good combo that'ss fast and grippy.

  12. #12
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    Just went for a ride on one of the more technical trails here on Long Island. Ran my tires at around 30psi. Wow what a difference! The bike handled so much better and I wasnt spinning out my rear tire on looser climbs nearly as much as I used to. Awesome! Thanks to everyone on this forum for the more than helpful advice. I cant wait to play with the pressure in my girlfriends tires. I hope it makes a difference in her riding experience as it did in mine. If she even notices is the other thing.

  13. #13
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    I weigh about 71 kg (156 lbs) and usually run my 29er 2.35 Nobby Nics at around 20 psi. Sometimes I've gone as low as 17 psi and still enjoyed the ride - I might drop to that level if the trail requires, but would not go that low for general use.

    Keep lowering the pressure and see how you like the difference. When you start bumping the rims on roots and other bumps, you've found your lower limit for that tire/rim combo. If you want to go lower than that, you'll need wider tires/rims.

    Tubeless doesn't require you to re-learn anything about setting the right pressure. It enables you to go lower than with tubes and the high-limit is brought down as well, but 30 psi is 30 psi whether you have tubes or not. They will roll better thanks to the reduced amount of rubber to deflect.

    Pressure and tire contact patch are directly linked to the bike + rider weight. So if you have one rider who weighs 250 lbs with the bike and another one who weighs 125 lbs with the bike, they will theoretically achieve the same size contact patch when the latter uses 50% of the pressure of the heavier rider. Of course the pliability of rubber and some other factors play their parts in this, but the principle is important to grasp. Pounds per square inch...

  14. #14
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    I weight about 110 and run around 17psi front and 20psi rear. I could run lower but the sidewall gets flexy for me. I've never burped my tires with Crest rims and a layer of strapping tape (too cheap for yellow tape). I have Schwalbe RaRa 29x2.25 on the front and WTB Nano 29x2.1 on the rear. Both are tubeless, and the front was purchased for $12 with a sidewall tear. I hand sewed it back up with 30lb braided fishing line and it works perfectly.
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  15. #15
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    PLEASE get her to learn how to inflate her own tires to the correct pressure. See the other posts about pressure hints, but it's not only a numbers game. Mountainbike riding has everything to do with feeling tire grip, compliance, stability and risk of punctures.

    Different tires, different circumstances, different pressure. Some pumps are way off. I'd allways advise to litteraly feel (with your thumbs) how soft / hard your tires are and learn what softness works for which trail conditions.

  16. #16
    psycho cyclo addict
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    Quote Originally Posted by JeroenK View Post
    PLEASE get her to learn how to inflate her own tires to the correct pressure. See the other posts about pressure hints, but it's not only a numbers game. Mountainbike riding has everything to do with feeling tire grip, compliance, stability and risk of punctures.

    Different tires, different circumstances, different pressure. Some pumps are way off. I'd allways advise to litteraly feel (with your thumbs) how soft / hard your tires are and learn what softness works for which trail conditions.
    +1 - you need to have an analog method of determining tire pressure (like grabbing it with your hand) in the event you do not have your tire gauge or another one of questionable accuracy available. I've been startled more than a few times by what sounds like a rifle being fired when someone's over inflated tire blows a hole in the sidewall. It is generally not a good thing, particularly when it happens to a front tire during a nice descent.

    Not only different tires- different rim widths are also a factor. My GF weighs 117 and I have her running tubeless Stan's 355 29er rims with PSI around 17 front / 23 rear. I am 195 lbs. and on those rims I managed to burp flat one running ~21 PSI (on major up/down twisty/curvy single track. On a wider rim, I can run 18 PSI or a bit lower (which provides at least some cushion on a rigid steel bike or more grip on my dual suspension 29er).

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