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  1. #1
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    Front end squirmy on faster flowy stuff - tire rolling over?

    I've been noticing the front end of our ECDM very suddenly going from sure-footed to squirmy when we are hitting the bermed flowy trail coming down the local hills. My best guess is that the feeling is coming from the front tire folding or rolling over. Looks like there's some wear on the sidewall rubber too, so maybe a correct guess...

    Anyone else ever notice something like this? Did you work out a solution? We're currently running a 2.4" WTB Mutano up front at ~25psi. I'd guess narrower tires and/or higher pressure would lessen this problem, but we kinda like the fat rubber at the pressure it is at for everything else.

  2. #2
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    What's the condition of the dirt on the berms? And where's this fun trail?

    In any case, that 25psi is what I'd look at first. We had a tire pressure thread a while back and most people were running 35psi+ to avoid squirm issues. I run 40psi on a 2.4 WTB Prowler up front on hardpack/rock/silt-over-hardpack trails and only have issues when I get into very soft surfaces unexpectedly. But we're also a 360lb team with gear and I'm 6'1" so nearer 7' tall on the bike. Lot of weight up top on a tandem.

  3. #3
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    I agree with Okay, I'd suspect the 25 Psi Even tubeless that's pretty low for a tandem. I run WTB Stout 2.3's F & R. Front is usually 40 psi and rear is 42-45 psi.
    Much like Okay, we're a bigger team, 345.
    -Aaron G.

    "Before D.W., "anti-squat" was referred to as pedal feedback."

  4. #4
    Neve_r_est
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    Run a wider rim, solves all those tire rolling issues and makes pinch flatting a bit less likely as well.

  5. #5
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    We're hovering around 290 with camelbak's, give or take. I think we'll try going to 30-35psi and see if it's any better.... 40+ just seems like we'd have problems in other sections... I think we've become much more surefooted in the technical stuff as we've lowered tire pressure.

    Dirt on that trail is nice and dry these days. Light coating of dust, but very much hardpack with only some smaller rocks well bedded into the tread. I didn't notice any of the unsteadiness over winter/spring here (Germany), but the trails were a whole lot softer then due to the steady cold, grey weather that took hold from Nov-May. Before getting here, we hadn't ridden anything quite the same - most stuff was either flatter, or more technical, or a combination of the two. Here, you go up then hill, then down the hill & then maybe a beer or radler before going back home.

    I've been afraid of going tubeless on the ECDM. Burping some air, especially when railing a corner just seems like too high of a probability & nothing good would come of that happening. Sounds like you're running tubeless?

  6. #6
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    Re: Front end squirmy on faster flowy stuff - tire rolling over?

    Agreed on the 25psi as the likely issue. We are a 270lb team, running tubeless on a 35mm rim (Velocity Blunt) and have found that the sweet spot for us is 30psi.

    Sent from my SCH-I535 using Tapatalk 2

  7. #7
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    Rim's are decently wide - ZTR Flow's. Surprisingly, we've been pretty OK about pinch-flatting lately. There is a reasonably hefty tube in the front, but we hit plenty of square edged rocks here too.

  8. #8
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    Air pressure is easy to adjust on the trail. Take a gauge and your pump along on that same trail you originally posted about. Session it while changing pressure up front, to verify it's a pressure issue. With that knowledge, you can reconcile it with your usual pressure and compromise more one way or the other, depending.

  9. #9
    PMK
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    While it is likely tire pressure causing the problem, can I ask how old is worn tire. For us, we see a pretty drastic difference from a fresh tire to a worn tire handling wise.

    Also, consider the line chosen to ride the turn, if you are on terrain that is less than typical grip, Rather than ride the worn line from single bikes, you may need to have a different entry, apex and exit point to keep from stuffing the front end.

    Without seeing or riding this trail, are you pedaling as you turn or freewheeling. Can you put the outside pedal at 6:00 and apply a bit more weight to drive the tire into the dirt? Would unclpping your inside foot and holding it off the pedal add more front grip?

    Also, I did not see any specifics on the bike itself. Sometimes certain frame geometries or fork lengths can let the front wheel slide and struggle to find side grip.

    As the others posted tire pressure first should solve the problem.

    I agree too that having the bike go straight when you want a corner can get challenging. The stoker probably can feel it happening, and to lean the bike over more to gain grip and make it turn can seem counter productive from the back seat.

    PK
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  10. #10
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    Quote Originally Posted by PMK View Post
    Rather than ride the worn line from single bikes, you may need to have a different entry, apex and exit point to keep from stuffing the front end.
    Having single riders ride our line is always amusing. I try to warn them, but...

  11. #11
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    Quote Originally Posted by Okayfine View Post
    Having single riders ride our line is always amusing. I try to warn them, but...
    I experienced this for the first time this past weekend, on a familiar loop that we normally ride our single bikes on, I rode with my daughter on the ECDM and the guys were following my lines and were bouncing all over. We (daughter and I) never felt out of whack.
    Attached Thumbnails Attached Thumbnails Front end squirmy on faster flowy stuff - tire rolling over?-gandibranch.jpg  

    Front end squirmy on faster flowy stuff - tire rolling over?-gabandiuh.jpg  

    -Aaron G.

    "Before D.W., "anti-squat" was referred to as pedal feedback."

  12. #12
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    Front end squirmy on faster flowy stuff - tire rolling over?

    +1 more on the tire pressure.

    Also, I've tried a couple WTB tires (weirwolf 2.3 and Bronson 2.2, I think) on the ecdm and found them unsatisfactory. I think the sidewalls are too supple. I like them on the single bike, but they were kinda terrifying on the tandem.

    I'm running tubless on Mavic 521 rims and have found anything less than about 34 psi to be too soft. We are also I'm the 360+ gear weight range.

    I'm using UST Nevagel 2.35s front and back and am pretty happy with them.
    --Reamer

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  13. #13
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    We rode completely different trails over the weekend, so nothing definitive, but we did up the pressure front & rear to ~32 & ~35psi. Never noticed any of the front end "squirm", but there really wasn't any high-speed corners to test things out on. Still had grip for the technical bits & didn't feel the rim quite so often, so that's a bonus.

    Paid more attention to technique as well (thanks for the reminder PMK), but thinking through the problem, on the fast downhill stuff we're focused on keeping the pedals out of harm's way - more alternating 3:00 & 9:00, then anything else. Definitely not comfy with the idea of putting a foot out to change balance, but maybe we'll try it out for fun.

    Front tire is also getting older. Rears wear out within ~6months, but the front has been on there for over a year... we're going to play a bit more with air pressure, but I wonder if you are onto something with the tires becoming more supple with use.

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