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  1. #1
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    Tires for running low pressure

    Hello All

    Last season I installed a set to Race King 29 x 2.2's on my hard tail. I had to run higher pressure to avoid squirm (30+ psi). I realize that is fairly normal and I assume that it has to do with the side wall height and stiffness. I am ok with this up front, but in the back I don't really like the added pressure.

    I am looking for a tire that will handle low pressure well (15-20psi) with little squirm. I willing to absorb the added weight of a thicker side wall, more tpi..etc. Previously I had tires that would handle this, but that was a while ago, and tires have changed a lot since then.

    I have little knowledge of what is available out there so any advice helps

    Thanks, Tim

  2. #2
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    What is the internal width of your rims? The relationship between rim width and tire casing width has a lot to do with how squirmy a tire feels at low pressures.

    Back in the day my crossmax 19mm internal rims rode like garbage wiht any tires wider than about 2.1”
    2008 BMC Fourstroke 19-559 ISO (RIP in peace)
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  3. #3
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    ^^^ yeah. In my experience, tire construction doesn't matter much in this regard. Rim width does.
    Do the math.

  4. #4
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    The outer width is only about 25mm, I recently put a new rear wheel on as well, it sounds like I may have picked the wrong one. What would you guys recommend. It sounds like I need a new rear wheel.

  5. #5
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    At 15-20psi, anything that's not a 2-ply DH tire will squirm regardless of how wide the rim is. There is no magic solution.

  6. #6
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    Quote Originally Posted by TimmySea View Post
    The outer width is only about 25mm, I recently put a new rear wheel on as well, it sounds like I may have picked the wrong one. What would you guys recommend. It sounds like I need a new rear wheel.
    Id look for a rim that is somewhere around 25-29mm internal width. Your current rim is probaby 19-21mm and will be best with 2.1” tires.

    Aerius also has a great point. You should be shooting for somewhere between 20 and 30psi. 15psi is way too low unless you switch to a plus bike with something like 2.8” tires.
    2008 BMC Fourstroke 19-559 ISO (RIP in peace)
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  7. #7
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    Thanks for the help. I should probably mention that I am running pretty much entry level XC bike. I probably ride it harder than I should....but it's all I can manage now.

    With the original 2.1" rear tire and original wheel, I had no were near the amount of squirm I had now. I just want to know what I can change in my set up to make it better.....should i be looking at tires or rims? It sounds like rims might make a difference. Even if I cant get below 25 psi, thats better than 35psi.

  8. #8
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    Rims or an entirely new wheel with the 25-29mm internal width will allow you to run 2.2-2.35 tires with the proper pressures with minimal squirm. Whether or not that upgrade is financially responsible is entirely up to you. If that is the bike you are gonna ride for more than a year or two, it might be worth going for it. If you can see yourself upgrading the entire bike within a few years, i might recommend just putting that money into a savings account for the time being. In the MTB world there will always be another “upgrade” tempting you whether you bought a $500 or a $5,000 bike.

    The other way to avoid squirm is to just go back to the 2.1” tires on your existing wheels. That would certainly be cheaper but it depends how important riding wider tires than the 2.1” is to you. 2.1” was considered “wide”, at least to me, back in the 90s and early 2000s, so you can no doubt have a lot of fun on the trails with 2.1” tires.
    2008 BMC Fourstroke 19-559 ISO (RIP in peace)
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  9. #9
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    People are so worried about running higher pressure. It's not a problem, and is very often beneficial. Squirm is a problem!

  10. #10
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    Tires for running low pressure-img_5949.jpgTires for running low pressure-img_5938.jpg

    Next.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  11. #11
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    Lots of tires were designed for 19-21mm inner rims. They're still out there being sold. They need high pressure. Go low and they can squirm or even fold over with no tread contact. You get a lightning quick slide if a front folds and you're on the ground.
    There are tires designed to run at lower pressures. They are designed to do that in conjunction with wider rims. The width gets rid of the 'lightbulb' effect and supports the sidewall. No more foldover. Instead the sidewall wrinkles for a bigger footprint and more traction. When you do lose grip it's a slower slide-out with time to make a line correction and no crash.

    Frank Stacy Design does the Bontrager tires to get more performance from high volume very round tread profiles at low pressures and wide rims when correctly matched to the right terrain.
    Hardpack with loose, rocks and roots that don't slice sidewalls and less than dh speeds match with the XR Teams. The XR2 2.2 works really well with a 30mm inner rim at around 14 front 18 rear for me. The 2.35 matches to a 35mm inner at a couple psi less. The 2.6 with a 40 at less. The 3.0 can take a 55-50. Your pressure depends on weight and terrain. You don't go low enough to get rim hits unless you use a CushCore rim protector insert. Take a gauge and frame pump out to your trails when you start experimenting.

    The problem is who can afford a bunch of different width wheels to figure all this stuff out. Probably different width front and rear. Many, many options. I would suggest for a hardtail at Patapsco SP 35mm rear if your frame can take a high volume XR2 2.35 Team. 30 is you need a 2.2. 40 for a front will get you a 2.6. That should fit with every fork Boost or not. Don't buy Mavic wheels with proprietary parts.

  12. #12
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    OP are you tubed or tubeless?

    Many seasons ago I went tubeless and the first thing that I noticed was tire squirm. I was running 23mm ID rims and single ply Maxxis tires. If I dropped the pressures below 30 psi the squirm was more pronounced. After quite a bit of rim widths and casing styles (EXO, single, dual ply etc.) I have determined that not one single variable is going to eliminate squirm and still allow supple compliance. Regardless of rim width & casing construction I still run 30psi in the rear 2.2 - 2.35" tires..

  13. #13
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    Quote Originally Posted by eb1888 View Post

    Frank Stacy Design does the Bontrager tires to get more performance from high volume very round tread profiles at low pressures and wide rims when correctly matched to the right terrain.
    Hardpack with loose, rocks and roots that don't slice sidewalls and less than dh speeds match with the XR Teams. The XR2 2.2 works really well with a 30mm inner rim at around 14 front 18 rear for me. The 2.35 matches to a 35mm inner at a couple psi less. The 2.6 with a 40 at less. The 3.0 can take a 55-50. Your pressure depends on weight and terrain. You don't go low enough to get rim hits unless you use a CushCore rim protector insert. Take a gauge and frame pump out to your trails when you start experimenting.

    The problem is who can afford a bunch of different width wheels to figure all this stuff out. Probably different width front and rear. Many, many options. I would suggest for a hardtail at Patapsco SP 35mm rear if your frame can take a high volume XR2 2.35 Team. 30 is you need a 2.2. 40 for a front will get you a 2.6. That should fit with every fork Boost or not. Don't buy Mavic wheels with proprietary parts.
    Why do you plug bontrager so much? Not accusing, just curious.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  14. #14
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    Quote Originally Posted by scottzg View Post
    Why do you plug bontrager so much? Not accusing, just curious.
    Incidentally the tire that did not squirm was a bontrager. I just got a chance to look at it again.

  15. #15
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    I have the Race King Protection 2.2 (tubeless) on the rear of my bike with a 19mm inner width rim and I have to run 27-ish PSI to avoid rim strikes on rocks. I also weigh 160lbs. A wider inner rear rim would probably help you out alot as others have said.

  16. #16
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    I was running a 26" Stumpjumper hardtail with 2.1" Specialized Renegades on Roval Control SL 16.5mm internal rims at 22f and 24r psi for racing.
    I weighed about 195lbs back then.

    Then a single speed hard tail 29er 2.1" Fast Traks on 23mm internal rims at 20f/22r.
    Now 190lbs and 29er 2.3" Ground Controls on 23 and 25mm internal rims on the single speed rigid and geared full suspension at 20f/22r.

    Squirm, yes. Burp, not yet.

    Probably need to ride harder/faster though

  17. #17
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    I'm 170 pounds and can run Race King 2.2's at less then 20psi on 21 ID rims with no rock strikes (and we have rocks) or squirm or fold over. I've actually rarely ever had a tire squirm on me. I'm a pretty fast cat1 maybe I just ride smoother than most.

  18. #18
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    Quote Originally Posted by scottzg View Post
    Why do you plug bontrager so much? Not accusing, just curious.
    You got to put out the info you know something about.
    Everyone was info on Maxxis tires and less riders have tried Bontragers.
    They are less expensive and they last a long time.
    They are designed from the start for wide rims. Higher volume and a more rounded tread profile than Schwalbe and Maxxis.
    Imo a better tire at a better price for the terrain I recommend them for.
    I have miles since 2014 on wide rims and Bontragers. Starting with 2.2 XR2 2.2s on 30mm rims.
    As low as 11 psi for a front. That gave the best traction but the rim wouldn't survive rocky conditions.
    The change in how the tire slides out was a big improvement over Nobby Nics and others on 21mm inner rims. I just stopped crashing as much when pushing things. My bike started sliding out more slowly with time to control it.

    Riding is safer and a lot more fun with this setup on the terrain I recommend these tires for.
    That can be a big positive change especially for newer riders trying to go faster.

  19. #19
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    Bontrager tires are great, more people should ride them.

  20. #20
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    Are you on full suspension. I doubt you could smooth out the what I am experiencing by riding style. What rim are you running in the rear....this is a really interesting data point

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