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  1. #1
    No Clue Crew
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    Bontrager SE4 2.4 vs 2.6 braking traction questions/observations

    Had an interesting and unusual experience this week and thought it would be good to have some outside input.

    I run a Bontrager SE4 29x2.4 on my Ripmo and recently built up a SS Canfield Nimble 9. I liked the SE4 so much that I bought a 2.6 version for the hardtail. These are rear tires.

    I have about 20 miles on it now and noticed a significant difference in braking traction between the two bikes. The 2.6 breaks traction very, very quickly when on the brakes vs the 2.4. I don't notice any difference on the gas, climbing, descending, etc. Only when the brakes are on, but the difference is pretty dramatic. Any sort of braking force in the rear causes the 2.6 to start skittering.

    Background stuff: Experienced rider, decently fast, 190 pounds in gear. Terrain is Phoenix, so rocks, hard, loose over hard, kitty litter over hard.

    The 2.4 tire is on my Ripmo fully, tubeless, 30 psi on a 29mm internal rim. In our terrain, I've found I'll rim strike at speed at less than 30 psi.

    The 2.6 tire is on the Canfield hardtail, tubeless, 25 psi on a 34mm internal rim. Still experimenting a bit with pressure.

    Obviously not an apples-apples experiment given the hardtail vs. full suspension. I get that a non-suspended rear reacts differently when on the brakes. But the difference is so huge it seems like there's something else going on.

    Tire pressure? Rider admittedly more used to full suspension vs. hardtail not weighting the bike properly? Something else?

    Thanks for any thoughts.
    Just like a raindrop, I was born to fall.

  2. #2
    since 4/10/2009
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    I'm sure there are several things going on that are affecting this, so my response will hardly be complete.

    That said, taking my own experience from fat bikes (ridden in a wide variety of conditions) is that notably larger tire volumes will "float" over loose material on the trail, and in order to counteract that effect, you need to consider a more aggressive tread pattern that will bite down into the loose material. Add that to the fact that many tire manufacturers who make a given tread in multiple patterns will subtly reduce tread depth on larger volume versions. I expect this is largely a weight saving technique. Under some terrain conditions, I've found the lower profile tread on bigger tires works fine, or sometimes even better. But when it gets loose, it's problematic.

    Your pressure is probably a bit high (in both cases, honestly, but especially so on the 2.6). Do you use a tire insert? Around my neck of the woods, with some pretty rocky terrain, tire inserts are especially popular for riders who like to hit that stuff hard. At least for rear tires. Lets them drop tire pressure a little bit for improved traction, with less worry about rim strikes.

  3. #3
    mtbr member
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    The SE tires have heavier less flexible sidewalls than the XR tires. You can add CushCore and try to get more footprint out of the SE by dropping the pressure as far as possible. You can switch to a XR lighter tire for even more footprint at low pressure. The 2.6 XR2 has been working for Mikesee on a 40mm rim. It's designed not to square off like some Maxxis tires with high volume and more rounded tread. With the wider rim you could use less pressure than with a SE. You could still use an insert or not. But rear suspension will probably still win for contact. Front braking is more important on a hardtail for me. I've ridden XR2 tires on wide rims at low pressures in Phoenix on my hardtail(not SM) but not the XR2 2.6 yet.

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