Bontrager XR4 and 29-4 All Mountain Tire

29er Pro Reviews Tires

Trek mountain bikes have improved dramatically over the past few years.  Bikes like the Remedy, Fuel and Slash have been introduced to compete well in their categories. The Bontrager tires have lagged in this revamp a bit and some might say that they have held back the bikes from their full abilities.

Trek knew of this and they have installed members of their A-Team to work on the Bontrager tires and components.  The goal was not only to bring the bikes to their full potential but also to make some of the best tires available for the aftermarket.  Michael Browne, formerly on the mountain bike group, called to say that he was genuinely excited about this year’s tire line. He said the XR1 and the XR4 tires have been revamped and invited us to push them on some dirt corners.

The revamp started by recruiting one of the premier experts in the field, Frank Stacy.  Stacy was a pro motocross racer for over 20 years and he moved on to tire development after that.  He has worked for companies like Dunlop, Pirelli, Specialized and Kenda developing tires in the moto, utility and bicycle areas.  A good article on his career can be found here from Motorcross Action.  Stacy is a student of the tire development field and he focuses on lab testing, field testing and really identifying and quantifying the elements like traction and rolling resistance.  His own site here called Stacy Testing gives you a peek at his methodology.

Ok, enough science.  The UPS man arrived with a bunch of XR4 tires and we were rightfully excited.  The tread pattern is much different from the previous generation as it is more modern with a simple, blocky and more open style.  The casing is supple and tires mounted true.  The Team Issue tires are light and are dual-compound. The center knobs felt normal but the side knobs were gummy and pinching them with your nail resulted in a scar that last many seconds as the tire slowly morphed back into its original shape. All the knobs had some siping or cuts to give them extra traction.

The 26er tires are called XR-4 and the 29er tires are 29-4. The ’4′ refers to their trail/traction abilities on a 0-4  line with the XR0 being an ultra lightweight xc race tire and the XR4 being an aggressive all mountain tire.  There is also an XR-Mud for wet and muddy excursions.

This graphic from Bontrager explains the tire line-up very well.

The XR4 tire size line-up is as follows.

Bontrager XR4 TPI MSRP* Bead TPI Weight
29 x 2.30 (Team Issue) 120 69.99 Aramid 120 794g
29 x 2.30 (Expert) 60 49.99 Aramid 60
26 x 2.20 (Team Issue) 120 64.99 Aramid 120
26 x 2.20 (Team Issue TLR) 120 64.99 Aramid 120
26 x 2.35 (Team Issue) 120 64.99 Aramid 120 730g
26 x 2.35 (Team Issue TLR) 120 64.99 Aramid 120 760g
26 x 2.20 (Expert) 60 49.99 Aramid 60
26 x 2.35 (Expert) 60 49.99 Aramid 60 770g
26 x 2.20 60 34.99 Wire 60
26 x 2.35 60 34.99 Wire 60

We mounted the tires to a few bikes, a Santa Cruz Blur TRc, an Ellsworth Evolution 29er and a BMC FS01 and have been riding them for the last month. The tires had good size and shape to them as they lived up to their 2.2 and 2.30 inch claims. We rode them in the loamy singletrack of Santa Cruz, loose fire roads of Los Gatos and wet trails of Waterdog and Skeggs in Woodside.

About the author: Francis Cebedo

The founder of mtbr and roadbikereview, Francis Cebedo believes that every cyclist has a lot to teach and a lot to learn. "Our websites are communal hubs for sharing cycling experiences, trading adventure stories, and passing along product information and opinions." Francis' favorite bike is the last bike he rode, whether it's a dirt jumper, singlespeed, trail bike, lugged commuter or ultralight carbon road steed. Indeed, Francis loves cycling in all its forms and is happiest when infecting others with that same passion. Francis also believes that IPA will save America.


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  • jeng says:

    yes there are sealing issues with these tires but I think that’s because they are so damn light. Take the good with the bad. My worst complaint with these tire is how hard the rubber is. Works great for loamy and loose over hard but not the best for wet rocks as I have found. Overall I find this tire to basically be the next generation Nevegal.. I would even call it the Nevegal II.

  • Estev says:

    I’ve got the original 29-4 tires front and rear, riding in central TX limestone, they grip and last. Will try the new generation when these wear out. Replaced the Nobby Nics with these, the Nics were gone and useless in a couple of hyundred miles.
    Great tire.
    Unlike my experiences with Bonti’s in the past, these sidewalls are not giving up.

  • JAYDMF says:

    When WTB discontinued the prowler Mx i was gutted, but then i found these, running the standard cheap 2.2 and 2.35 xr4s and theyre amazing. grip like hell no matter what, dont really change the feel that much at low pressure vs high so great in the winter. all round my favourite do it all tyre

  • Francis says:

    Great comments Estev and JAYDMF. Bontrager has really stepped it up with this one and we’re happy you guys are having similar experiences as us.

  • Ron Naiser says:

    Does anyone know how these tires (TLR) will seal up with Mavic 823 UST rims?
    Thanks for any advice.

  • sam says:

    I have bought a set of the 2.2′s XR4′s. Having gone through mostly every tyre and the reviews given, shown by the review by MTBR and the customer reviews, it looks like i made the right decision.

    Once ridden (either at cwmcarn or Afan-south wales uk) I will be on here to give my verdict.

    (Keep riding….even when its icey and dicey!)

  • Luis says:

    These tires are true 2.2 tires ! Light for their size and grippy as hell. These things definitely have traction. If you can grab um’ on sale, even better !!

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