Twenty Nine Inches has obtained a pair of Bontrager XR-1 29 inch tires for testing. These are listed as a 1.9″ width tire and are aimed at racing cross country style. The tire has a goal of being fast. light, and supple in terms of the casing. To that end, it is not a Tubeless Ready model.
While the tire may not be rated as a tubeless ready model, I did mount them in this manner to a first generation Bontrager Race X Lite wheel with the TLR rim strip installed. I used a mixture of CaffeLatex and Slime tubeless sealant to do this and had zero issues inflating and seating the tire on the rims. No leaking down so far and I suspect the tires will do fine in this configuration. Just be aware that I have undertaken this at my own risk and we at Twenty Nine Inches can not condone the use of this tire tubeless. It does void any warranties as well. However; being also realists, and knowing that folks are already running these tires tubeless, we will be doing the testing as such. (Note: These tires were purchased by the tester with his own money and said tester assumes all risks involved. Don’t try this at home on account of me!)
Bontrager describes the XR-1 as follows: (from the Bontrager site)
Designed in collaboration with Bontrager-sponsored pro race team riders, the XR1 is an ultra-fast rolling cross country race tire that’s ideally suited for dry and dusty condition. Small, tightly spaced knobs provide plenty of fast-rolling traction, while siping (thin slits) across the middle knobs give even more grip on dusty surfaces. Designed for front or rear use.
Furthermore; the tire features a 120 TPI casing, and several rows of very small square blocks with a very “crowned” profile. This is a tire very reminiscent of another favorite of 29″er riders from Kenda, but that tire is flattened a bit more in profile than the XR-1. The “Team” model is listed as a 1.9″ width, or 48mm knob to knob outer width and 46mm casing width. Weight is listed as being 495 gm. Here are my measurements from my samples, both mounted on 24mm wide rimmed Race X Lite wheels tubeless.
Width Of Casing……………….45.0mm
Knob To Knob………………….47.2mm
Height Of Casing………………41.3mm
Weight………………………….480gm/490gm (pair)
I’ll be hitting some dry, dusty courses in the coming weeks and also will follow up with some other race type tire reviews that have been put on hold due to our extended wet period here in the Mid-west. Stay tuned!
Note: These tires were purchased by the tester for review on Twenty Nine Inches. We are not being paid, nor bribed for this review. We strive to give our honest opinions and thoughts throughout.
@TG,
If you mounted the same tire on an Arch, which is narrower, by how many mm the knob-to-knob would shrink? Approx, of course…
Looking forward to the review.
@BubberRoy: 🙂 The Stan’s site lists the ZTR Arch 29″er rim at 24.4mm wide: http://www.notubes.com/product_info.php/products_id/346
I suspect that the XR-1 would be almost identical in measurements on that rim.
Sorry, I thought the Bonti rims were as wide as the Flow. Again, stand and corrected…
Furthermore the Arches are said to result in wider profiles due to the low rim hooks. It will be in the 0.x mm range realistically.
This tire has such a minimal casing height… Would it be adviseable to run them on wider rims than your average XC racing rim (355/Crest)?
Will be interesting in how you think it compares to the Small Block 8.
@JeroenK: I don’t think so, at least not if your trails are rocky or rooty. The tire profile will flatten the wider the beads are set apart, reducing the already minimal casing height. The tire would want to bottom out and would require higher air pressure to prevent that.
Of course, the next step up in width is adding 2mm per side, (most rims being nominally 28mm wide in the next “step up” from the Race X Lite), and that shouldn’t be a real big deal, but it would negatively affect the tire in my mind. You probably would notice a ‘closing up” of the tread, with the tread blocks starting to pinch inwards, reducing grip. Again, it would be minimal, but wouldn’t be optimizing this tire’s performance.
@dman: Agreed. This tire was developed from the design set forth in the Smallblock 8, as I alluded to in the post. That tire lists as a 2.1, and is definitely bigger than the XR-1, so we will keep that in mind.
Bought a set of these on eBay, on a whim, awhile back. Threw them onto my Fargo while on vacation recently in an area (Grayling, MI) known for dry, sometimes sandy trails. I’ve ridden Hanson Hills (Grayling) with them, Pigeon River State Forest, a rail trail going south from Mackinaw City, and even the very rooty(!) Bruno’s Run in Michigan’s U.P.
I like the tires a lot. They’re nice and light. I went from Halo Twin Rails to these XR-1s, and ease in spinning up the lighter tires is noticeable.
I also notice the “suspension” effect from these tires. Whenever I hit a bump, I can feel the casing giving way and providing some cush. The effect is very noticeable compared to other tires I’ve run, and is rather welcome on the fully-rigid Fargo.
I did pinch-flat once, when I pulled up too early approaching a cement patio and came down on the edge of the cement rather than lofting the wheel over it. Oops! My bad, that one. First time in my life I’ve ever pinch-flatted.
I tore up Bruno’s with ’em yesterday though, and they were fine.
I like them so much that I bought a second pair for one of my other bikes.
FWIW, I’m running them at 30psi on some Rhythm Comp rims.
Well, I guess that’s my review :-). Now I’ll wait and see what GT comes in with after he gets in some ride time.
Interesting. Can you comment on them as compared to the XDX 2.1 or dry-X 1.75? I’ve got both of those, which share the same general tread pattern. They are lots of fun on gravel and even pavement, they felt especially suited to chipseal. Both run true to size width-wise.
Like Jonathan and his xr-1s, these feel like you’ve got a bit of suspension if on a rigid bike, but none the slower for it. Wondering if xr-1s are in my future, or if they are so close to the xdx/dry-x as to not be worth it until I wear a pair out.
Thanks for the actual sizing info, GTed, that helps figuring out fitment to my Rawland.
Set my XR1 take-offs from my Fly 100 on my ’08 Fly, RXL rims, tubeless with Stans. Took a punch of compressed air to get them fully seated and some Stan’s shakes to keep a seal.
I’m anxious to see how your test progresses, GT. So far for me, they up the acceleration to the next level, as well as the ride “firmness” on this carbon HT. What I don’t know is how much they will compromise technical riding, especially in the rocks out here in the West.
@ jimmythefly – as a big fan of XDX as a back tire, I’ll say the XR1 is a different animal. XDX, especially 2.1, is a tough tire, and heavier. I am sure I will not run the lower pressures I use on the XDX (24 on the back – and I am 210 pounds) on the lighter XR1. So – XR1 most likely will be much less plush. I am trying them to get a compromise to improve pavement rides (often long climbs) to the trail while still being able to ride singletrack effectively when I get there.
Thanks Lee. I’m also at 210 dry, so your comment about ability to run low pressure rings true.
Curious to see if your xr1 set up is faster on the road while maintaining off-road ability.
Got a Rumblefish 1 back in May 10, enjoying it enormously; would like some road tyres for commute on paths and roads- would the XR1 be a good tyre for this?
I too look forward to your review and experience to compare with my own.
An unbelievably fast, comfortable and suitably grippy and predictable race tyre but like some of the schwalbe rubber, compromised in many ways especially durability etc.
Mine didn’t last more than about 500km on the rear before resembling a slick in the centreline with the knobs stripped off!
I am almost certain GT referred to them elsewhere as tires designed for one, sole purpose: racing. The creators did not and do not care for durability / longevity. His own words, rephrased.
I don’t know: don’t really feel like purchasing new tires every month..
Small Block 8’s don’t wear all that quickly. Might if you ride a lot of pavement…but what tire wont.
Dman, correct on the small block 8 front. Much harder compound. I have not owned them as they are heavy but I believe they are from the same mould as the karmas which last really well. I was just amazed how easily I shedded the XR-1 and no, wasn’t riding pavement. Keen to see if it was just the batch that my tyres came from?
This might sound harsh, but big guys should not even consider the XR1, unless your trails are very smooth.
I am 70kgs/155lbs and I have a very hard time on them on rocky or rooty courses. To be safe, you have to run air pressures that suck the comfort, grip and fast rolling over bumpy ground out of these.
On smooth courses, the XR1 flat out rules.
@Professed – SB8’s are heavy?? compared to what (in the same size range)??
@dman, in regards to weight, the ones my mate had were 600gms.
compared with the karmas i have had – just over 500gms – to me that is heavy (for a 2.0-2.1) non tubeless tyre.
for instance my XDX TLR is about 700 gms but its HUGE and can be run tubeless bringing it back to the SB8 weight point – it also rolls really well by the way…
my buddy also trialed the SB8 against his karmas and didnt find them any faster so i didn’t bother with them.
but its all personal when it comes to weight, grip and conditions. we all differ in our preference and perspectives…
OK, this is about the XR-1. It is streets faster than the Karma in hard conditions. faster than XDX, faster than Racing Ralph.
just raced my old balding front today on the rear as not enough tread for use on the front and conditions were dry, hard with some loose over, a few rocks on the steeps and patches of mud. best result this year – a second place ! ok, felt really good but the tyre might have helped a bit…. 🙂
i just wish these things would last as they are so comfortable – even at 30psi+ with tube – respectably grippy and fast fast fast !