[Cloxxki]

Next victim of pizza knife : Bontrager XR Rear

XR rear 2.2", brand new : 653g
Chopped : 602g

I took off 1mm off the sideknobs, and half of the others. It now REALLY looks like a reace tire. I could take it a bit further, cutting off front corners of the centerknobs, to make it resemble a Schwalbe Fast Fred a bit more.

I never got a chance to try the front XR 2.25", which I brought from ~660g to 625g. I left most of the sideknobs alone on that one, and barely took off something from the others, hoping they would not stick out too much, and allow it to keep it's full cornering grip, so I don't lose the 29inch's edge in the chopping process.
The rear tire still has pretty good sideknobs left, might be trimmed more, but that would not save enough weight to be worth it. As I said, the rear looks really fast now, and might actually have such a low tread now, that since the 26" age, I'll have to be careful on steep climbs to not lose traction. For racing, that can be a good thing, it means that on everything that's not steep up, I get maximum speed.

Not that both my XR's are still above claimed weight, despite substantial modification.

No camera, so no pics yet. Hope to test later this week, if the rains stay away a few days.

Happy trails,

J

 

[Cloxxki]

Still no-one cares, and rather waits for the perfect tire to just be anded to them by tire brands. I'll post an update anyway, if only it's for keeping my records.

The XR Front was down from ~660g to 625g, and I've perfected some of the knobs a bit more, which maybe saved a single gram, not more. Just make it look tidy and consistant. I decided that the sideknobs stuck out too much for me, and that if the Nanoraptor can practically do without them, the capably cornering XR should be able to do with a single mm less of it.
When I had completing taking off ~1mm (thinnest easily removable) of each sideknob, I was down to 609g. The tire now really looks like a purposely designed go-fast XC race tire, although of course it does look quite messy.
I have this theory that the imperfections from working with as rough a weapon as a pizza knife in my untrained hands, creates the tire equivalent of a sharkskin as well as golfball. I would not be surprised if a knife-cut surface could be proven to be both faster rolling as well as better gripping than a smoothly molded surface. Definately the latter.

Cutting the sideknobs at first wasn't worth the weight to me, although it did end up being 15g worth, but I figured that on soft soil going dead ahead, you really down want a race tire with the sideknobs already dragging along.

Both the front and rear XR are now treated equally : sideknobs minus 1mm, all other knobs with half topped off. Total weight savings a bit over 100g. The rear might even be able to suffice with even less sideknobs, room to save another 10-15g, but right now I'm more eager to test them on a fast race course than to reduce them to bear carcass, overdoing it in my enthousiasm.

I'll be satisfied if this XR "Race" customization leaves me with a combo that on fast soil is :
- Faster rolling that folding green line Nanaraptors, which are 630-650g stock, but I already learned can be trimmed by 35g while only making them faster and grippier.
- Gripping better than the front Nano, less thaction than a rear Nano is only expected.
- (This one is already in the pocket) more volumous than a Nano.

No easy goals to reach with just a stock tire set, a pizza knife, and no mentionable enigineering knowledge to help me. Still I'm pretty confident that I'll be satisfieds, at least on the dryest, fastest of tracks. I wish I had done this 2 months earlier, when I raced at a very fast and sandy course with a dry MX track and smooth singletrack. I had 1432g of Nanoraptors on my bike that race, with the XR's I'm down to 1211g now, and they're bigger which would have been welcome on my rigid bike.

Now at ~605g average, my XR's at least seem to be on par with greenline Nano's after they get my workover where I take out 35g of knobs, not trimming them, but removing only (complete and parted) knobs at their full height. More info in my thread "WTB Salimander".

If you've read this far, you're obviously bored to death, with nothing better on your hands to do, or really interested in tire tuning, and you should really take a knife to some overbuilt tires you have yourself that look like they could be improved upon to meet your preferences. Keep me posted on that please!

Happy trails,

J

 

[ncj01]

need pictures

I liked the XR's just as they are...looked good on the bike anyway..

 

[20.100 FR]

Nice report, but it's difficult to get an idea without picture.

I would be interested in "scientific" tests (on rolling resistance on hard and soft soil, and traction, and cornering) like getting to a certain speed and then let roll, full out twisty singletrack time, etc... With enough value so that they have a statistical meaning.

Keep us informed !

 

[Cloxxki]

Again, no pics available. Just look at the XR's, and imagine taking off half of each knob, and just 1mm off the paired outer sideknobs.

Oh, to update here about the modified front used Nano, I raced that last weekend on a sandy/loose forrest singletrack couse, and it did well. I relaly think it handled better than before, and even in deep sand (recreational beach by a lake) sand it was pretty stable. I could corner faster with less understeer, and actually pulled big gaps on widing flat singletrack, to a field of 26"er all on tires like Racing Ralphs and TT Larsens.

The Nano modification is harder to understand from wiritng, though I did describe it pretty clearly, but one can figure out by itself, and probably even do a better job them I did.

 

[Padre]

We've seen your pictures before! We know you have a camera!
If you're willing to spend an hour chopping up a tire you can spend 2 minutes taking a digi pic for your homies on the 9er board....
has a thread ever been less helpful without pictures? please cloxxi...throw us a bone!

 

[Cloxxki]

All pics I've ever posted here were made with either borrowed camera's, found online or mailed to me by helpful friends. Use your imagination until someone helps me out with these. And start chopping random knobs already!

 

[gregk]

XR rear 2.2", brand new : 653g
Chopped : 602g

I took off 1mm off the sideknobs, and half of the others. It now REALLY looks like a reace tire. I could take it a bit further, cutting off front corners of the centerknobs, to make it resemble a Schwalbe Fast Fred a bit more.

I never got a chance to try the front XR 2.25", which I brought from ~660g to 625g. I left most of the sideknobs alone on that one, and barely took off something from the others, hoping they would not stick out too much, and allow it to keep it's full cornering grip, so I don't lose the 29inch's edge in the chopping process.
The rear tire still has pretty good sideknobs left, might be trimmed more, but that would not save enough weight to be worth it. As I said, the rear looks really fast now, and might actually have such a low tread now, that since the 26" age, I'll have to be careful on steep climbs to not lose traction. For racing, that can be a good thing, it means that on everything that's not steep up, I get maximum speed.

Not that both my XR's are still above claimed weight, despite substantial modification.

No camera, so no pics yet. Hope to test later this week, if the rains stay away a few days.

Happy trails,

J

I commend the effort and initiative to "make" your tires cater to your needs rather than waiting for one to be manufactured, but... that sounds to me like the most mind-numbing and tedious work in the world! How long does it take for you to do this per tire?

 

[Cloxxki]

Per tire you're looking at somewhere between 1 and 2 hours. If you want to perfect it afterwards, unlimited hours can be spent. I highly recommend keeping Discovery Channel on while doing this job, otherwise it does take too much willpower.
I do it sitting on the side of a bed, or a edge of a couch. Tire well inflated (Nano uninflated, no rim) on a rim, angled over a bin to throw the cut off knobs in. I manage this chore much better than shaving a tire bold of knobs for a frankentire project, I never completed one even. Noisy powertool, no workbench at hand, lots of rubber dust...this just requires a sharp knife with ~5" blade and a TV set.

Today I testrode the customized XR's. On pavement, they seemed to roll well, there was some 35psi in them. My route to the annual race course in the park 10miles from my home is more or less dead ahead, and I've been feeling kinda I'll since yesterday, so I didn't really push them in corners. They were pretty silent, and probably on par with Nano's or slightly better.
The course wasn't perfectly dry. Of all the trails I tried, I would probably have used a customized Nano rear and an untouched XR or AcX as a front.

Traction on short steep, slightly slippery stuff was definately just a fraction of what it originally was. It felt more or less like a Fast Fred 2.25-2.35. Broke loose, but not unrecoverable. In tall grass traction wasn't disappointing at all.
Over bulldozer-smoothened fresh sand, rolling resistance was outragiously low. Definately better than with Nano's which cut much deeper than the wider, flatter customized XR's.
There was a lot of work being done to the park, and workers left a messy lot of sand ona gradual slope. Ideal for a hillclimb test. In a few attempts I cleaned it, and I was surprised by the traction found and momentum kept. As it I was riding a level sand pit, not an ascending one.

I didn't find any high-speed corners in conditions I meant these project tires for, and as said I wasn't feleing very sharp. On the few slightly wet twisty trails, flat, up and down I tried, general cornering and braking traction were similar or slightly better than I'd expect from wide Fast Freds, and again it rolled pretty effortlessly. This was especially evident on a slippery bit where the top 1/3-1/2" of soil was waiting to finally dry up. No really biting grip, but the rolling was impressive. Not the tires I'd have used here, but still nice to try on.
On packed gravel the front braking traction surprised me. A maybe 5mph I locked the front disc brake hard, and the wheel just stopped rolling. Dead stop, no movement at all. Well, my rear wheel took off, which I didn't expect to happen.

Overall, I think these tires are pretty much what I had hoped for, although my test wasn't complete by far.
I did seem to have found a considerable rolling advantage, but didn't reach typical race speeds/
For dry XC racing, the climbing traction is sufficient. If my 26" competitors can manage with Racing Ralphs and even smaller knobs, I will with these as well.
On the few dry corners I rounded, it was somewhat of a feeling to get used to, but I don't see how I should go from feeling the fastest bike handler in a group to being the slowest. When the trails get dusty or even sandy, these babies will do their work, and take away most of my needs for the introduction of a Schwalbe Fast Fred 2.35".
I can't say I truly noticed the lower weight (ca 200g) over the 2 Nano's I've been running before, the front of which already customized, but hey, 200g is 200g. The way I see it, just over 1200g (some may get it lower, my XR were over 1300g to begin with) for such volumous tires with such fast feleing carcasses, that's pretty nice. Not the ultimum I look forward to in the future with 550g 2.25" Racing Ralphs or 550g 2.35" Fast Freds, but not all too far off it.

I wonder how I could further improve the grip/traction/speed ration on these tires, but for now I've altered them quite a bit already. I'll take them to the race next weekend, if the weather stays dry, it might get sandy in the forrests, that part of the country.

If you find your XR's to offer too much traction for you to ever use up, and wouldn't mind them rolling a bit easier, especially in loose stuff, this is a chore that could do more for you than an extra training of the same duration.

More reports later.

 

[Cloxxki]

20.100 asked me for updates on my XR specials, this is what I mailed him.

Today I had a 4-hour team couple relay race. Me and another singlespeeder, Hubert, on his XL Gary Fisher Rig 32-14, me of course on the XL KM 36-16, took on the rest of the 150-team field, all gearies. One man was driving at a time, you had to exchange number plates. 4h06 for the winners, 4h19 for us. Some of my early laps were over 30km/h.
How flat does The Netherlands get, even way sounds next to Belgium in the inlands? Biggest climb was a temporary bridge, 4 meters. Next biggest : riding through a truck, 1.4meters.
The soil was sometimes a little muddy (but drying), and the rest mostly fine sand over hardpack. some riders were on Full 2.35" slicks, and not even complaining.

My XR Specials were superb. Grip was sufficient (not the crazy grip of a fresh AcX or Klaw of course), and rolled really well as far as I could tell. I didn't run very high pressure, but it rolled well enough for me. Despite really high speeds and mostly headwinds, coast lengths didn't disappoint me. (On my last lap, coasting was irrelevant, I just pedaled and tried to complete my 2-lap stint asap, didn't even go fast enough anymore to justify use of brakes.)

Cornering was pretty fast, the faster the corner, the better. Some very technical riders on high-end 26" tires (Either Fast Fred 2.35" or Racing Ralph is the choice here) were maybe a bit quicker sometimes. But I still have to get used to these tires more, and learn to drift them. Today's course had only a few notable corners.

The XR Specials really just felt pretty much like 29x2.25" Freds, or at least how I'd imagine them if they existed. Probably a tad slower. They were not like the 2.35", those are just so smooth and grippy, thanks to shear size. XR Specials are incredible over sand, and rolled super well on loose forrest soil and that drying mud.
Considering they are the same weight as the Kevlar Nano's I don't have, even after cutting those as well, and the fact that XR's are biger, I think for now I have my dry weather race tires! But hopefully the (proto's existing and rolling?) Kenda Karma's will be already better still, out of the box... And why don't we hear anyone about the proto Specialized tires any more? Taken back by Sp and destroyed?

 

[P-Funk]

Hey Cloxxi, when's your birthday? Maybe we can all pony up a few dollars to get you a digi camera for your birthday ;-) They're so cheap now, they practically give them away in cereal boxes.

 

[Cloxxki]

One buddy threatened to give me one of his countless digicams, but hasn't so far.
26th Oct, but I can pretend it's next week...

No bike budget, so definately no toy budget until someone arranges a pay slip for me. I did purchase a whole Shimano DX 16t cog today, and I'm delighted to have added one to the collection. Higher on the toy-budget are : a PC that works, an internet connection that connects, a DVD player to run training vid...DVD's....no before I get to that, I'm buying bikes already...

My scrootchness did get me a pair of free raceday tires this month.

 

[mwills]

mmm XRs

i think these are the greatest tires i've used yet. pretty wild to modify them. i can't get over how nice the casings/sidewalls feel.

 

[Fastskiguy]

rear wheel knobs-need'em?

I think you can get by with a real minimal tread in the back, at least down the center. My ginsu modified mytho II (front tires used as a rear) is getting really lightly treaded down the middle and it's no problemo for the single speed bike. I have been running a 36X16 for a local race that is pretty flat so part of my "sucess" with the tire may be the lower torque getting to the ground because of the higher gear. It might not work on a gearie cranking up a steep climb in a 22X34 or something. But it rolls really nicely, that is for sure. And I left on the outermost knobs so cornering so far hasn't been too bad either. So my long winded point is that you might be able to run a nearly knobless rear on a single speed pretty effectively.

 

[Cloxxki]

Our race as said was flatter than you could order from a contractor, but indeed, traction was the least of any issues. 29" tires have quite enough, even Big Apple slicks.
Along with big gears come relative higher speeds and indeed torque, preventing slippage. I once had a gearie race (pre-29" UCI rule) where in the middle ring I would clear this short and unreal steep run up to a summit, and when I tried to go economy the next lap, in the granny, the rear let go on me.

I did take off 1mm off the XR's sideknobs, as otherwise the sideknobs would stick out quite a bit, and engage sooner than perhaps is smart. Straight rolling should be done on smooth centre treads, not sideknobs, I figured.

I didn't get a whole lot of mileage on uncut XR's (although I do still have a pair, fairly cheap in Europe for some reason, €26 msrp inc; 19% VAT). The XR didn't really show me a personality, were a bit boring, but in a good way. The XR Specials have much more personality, and there's a good curve of learning to work them through fast corners. In slow corners and fast kinks BTW, no isses at all, as on rails.