28 February, 2010

A detailed analysis of tubeless tires for cyclocross

A topic that causes much contention on internet message boards, and is generally pretty interesting to a lot of people is that of tubeless tire setups for cyclocross. I would like to give a detailed look at where we are at with the technology, and where things might be headed.

Historically, tubulars have ruled the discipline, and for good reason. You can safely run them at pressures suitable for the amount of traction required, and even ride them flat to the pit if needed. Most importantly, good tubulars have extremely supple casings (on the order of 300+ tpi), so they conform to the ground extremely well aiding traction and comfort.

Clinchers on the other hand, offer anywhere from 60 tpi to 320 tpi casings, though somewhere around 120 is probably average. The ride of the nicer clinchers is better than the cheap ones, but still does not come close to the performance of tubulars. Also, running tubes (even latex) at the pressures required for cross almost invariably results in a pinch flat costing you the race. When this does happen, you can't really ride it to the pit because the tire is likely to peel off the rim.

The mtb world has been familiar with tubeless tires and rims for some time, and the technology is now quite mature. There are 2 camps, generally speaking:
  1. UST which is a certified system encompassing a spec for both tires and rims. The rim and tire have matching bead profiles, which are much more square than conventional folding beads to give a secure lock. The tire includes a butyl layer - essentially a tube - so that it will hold air. The system may be used with or without sealant as a preventative measure from punctures.
  2. Converted setups, which involve a rimstrip (originally Stan's Notubes, but now often simply a split innertube) and the use of sealant to seal both the tire/rim interface and the tire casing itself (if a non-UST tire is used).
Since sealant affords such good protection against punctures, almost everyone uses it in their tubeless tires and suddenly UST becomes a lot less attractive due to the extra weight of the UST-spec tires. This has led to the development of "tubeless-ready" tires, or those which have stronger/tighter beads but not an airtight butyl layer so they can be used tubeless with sealant at more competitive weights. Parallel to this, non-UST spec tubeless rims have been developed, most prominently by Stan's Notubes where the bead hook is designed specifically to hold on to non-UST beads in a much more secure way than option 2 above. In my mind, this is really the gold standard of tubeless setups, and thus 3 new distinctions are formed, each with loyal followers:
  1. Those who prefer tubeless ready tires and rims (eg. Bontrager TLR setup, Hutchinson tubeless ready tires) with sealant, sometimes on UST rims.
  2. Those who use Stan's Notubes rims, any clincher tire of their choice and sealant - with the rim being designed to fit standard tires tightly, a secure and reliable setup can be had without the weight penalties associated with UST and tubeless ready tires.
  3. Those still using converted rims and tires - definitely becoming a minority, and IMO this setup does not have the same level of reliability at the bead interface, since it depends on a rimstrip to make a tight fit, rather than a special bead hook or tighter beads on tubeless ready tires.

So getting back to cyclocross from all of this: there are very few tubeless ready tires available, and no UST spec exists. As such, the primary systems in use to date are either converted rims or Stan's Notubes rims, both with standard tires. Performance, including bead security at typical cross pressures, has been an issue especially with converted setups. Most people using Stan's rims and some of the tighter tires do not have this problem.

This takes me to my inspiration for this post - having installed cross tires on my 29er wheels before, I notice that they have a great profile: wide and high volume, which is sure to increase performance.

Indeed this is what many tubeless users have been enjoying, since the only Stan's Notubes rim appropriate for cross has been the ZTR 355 29er rim, which is 24.4 mm wide (19 mm internal). The problem with this is having a wider rim means setting your brakes up for said rim, so when a standard road wheel is used they are not in the right place (far beyond what can be accounted for with a barrel adjuster). Also, at 410g the 355 is not really as light as it could be for cyclocross use. In response to this demand, Stan's has released a road/cross rim called Alpha 340, which is 22.35 mm wide (17 mm internal) and approximately 340 g. It also has machined sidewalls, which will improve braking greatly over the non-machined 355. This is still wider than the average road rim, but narrow enough that with careful setup one might be able to get their brakes to work with both using only a barrel adjuster. Unfortunately, much of the advantage of the wider rim has been given up, and I think if you were to really commit to tubeless use (i.e. switching all your wheelsets) that having a ~24 mm rim but with machined sidewalls and low weight would be ideal.
Lets consider however, the Alpha 340 as the best available tubeless rim for cross at the moment. Building these up fairly light with American Classic hubs and DT Revolution spokes 28h/32h front/rear you get a wheelset that is 1274 g ready to mount tires (incl. rimtape and valves). If we consider a typical high end clincher is 380 g and use 75 g of sealant per wheel, that amounts to 2184 g for the whole setup.

Now for a "typical" tubular setup of about the same calibre we'll take some Velocity Escape rims laced to the same AC hubs with DT Revolutions 28/32h. This comes out at 1327 g. Add some FMB tubulars (370 g each) + Mastik One glue (75 g for the pair), for a total of 2142 g. This is 82 g less than the top of the line tubeless setup above, and probably costs about the same when all is said and done (cheaper rims balance out more expensive tires).

So how does this wash out?
  • for similar money to a mid-range tubular wheelset (+ good tires), you can have the best tubeless setup currently available
  • the Alpha 340 rim is marginally wider than your average road rim - this is good for users who want to be able to use their road wheels or perhaps a set of tubulars they already own on the same bike, but this is not ideal if the goal is the best tubeless performance possible.
  • the tubeless setup is still dependent on low tpi tires, so the grip and ride will not be as good as tubulars until this situation changes. Low pressure performance is unknown at this point, with the rims not yet on the market for significant testing.
  • tubulars still come out lighter (though not by much, if you put the money into light tubeless wheels) and have inherent advantages (being able to ride them flat, etc.)
This shows promise for the tubeless camp, but it does not yet appear to be a viable idea for serious racing, considering that it costs as much as a set of reasonable tubular wheels and the best tubs you can buy and the performance is still less.

If we can get wide enough tubeless rims (dedicated cross rims, i.e. machined brake track, lightweight) and good supple clincher tires, ideally with beads optimized for tubeless use (i.e. tighter) there may be a case for making the switch, but at that point you have to commit all of your wheels to ensure brake compatibility.

In other words, we're not there yet. Keep buying those tubular wheels when the road racers dump them at the end of the season, and keep gluing up your Dugast/FMB/Challenge/Tufo tires with care, because it's the best we've got for the foreseeable future.

24 February, 2010

Escarpment climbing in Stoney Creek/Grimsby

This past Saturday I headed out with a group of cyclists cobbled together via a series of emails Friday. There were riders of varied ability, and the goal was to head out at a social pace to Grimsby and climb the escarpment a few times, then head back at a similarly relaxed pace. Some folks are heading to South Carolina in a few weeks and wanted to prepare their legs. Myself, I just wanted to get the km in my legs and do some hard efforts on the hills. 3 of us headed out from Niagara Falls around 8:15 to meet the rest of the group in St. Catharines at 9.

After some discussion about what route to take, we departed and rolled through Jordan and Vineland, fighting the strong west wind the whole way. Our first ascent to the top of the escarpment came at Mountain Rd in Beamsville - a gentle climb for 3 km averaging 3.3%, with the steepest part at 12%. Manageable, and one of my favourites in the area. I pulled away from the group, not intentionally, but just wanting to climb the whole thing a bit above threshold. I expected Dan to give chase, but it was Shawn who started to close on me but never made it across. We spun easily at the top giving me a chance to eat while the rest caught up. From here it was along Ridge Rd toward Stoney Creek.

At our farthest point, we descended McNeely Rd, which was a very new experience to me. I've never done a descent with such steep and tight switchbacks, so needless to say it was a bit hairy. Then, we climbed back up. 3 of us did, anyway. The climb is 1.6km, avg grade of 7.1% with sections at 17.1%. Needless to say, tougher than any other climb in Southern Ontario. It didn't help that my winter bike has a single 42t, so I was climbing in 42x28 (approximately equivalent to the second last cog on my road bike, 39x23). That was fun. Down Fifty road, and into Tim Hortons we went as we were now quite hungry and ready for a break at this point.

Following the refueling stop, most of the group went back up Fifty Road (no easy climb but gentler than the others in the area) while the same 3 of us decided to climb Wolverton Rd. instead. Wolverton is 1.3 km, avg grade of 8% with sections at 17.2% - similar to McNeely but 300m shorter and thus a little steeper on average. Also, the steepest part is a long stretch at 16-17% about 3/4 of the way to the top that just about breaks your legs.

Once on top, we enjoyed a nice tail wind, the same wind we'd fought on the way out. This carried us home, which included one final climb up the shorter and gentler escarpment back home in Niagara. In total the ride was about 145 km door to door for me, with about 850m of climbing. Not bad for a "flat" area with no mountains or real hills to speak of.

Here is my ride data, as well as an elevation profile (with slightly different time/distance since it was from Shawn's GPS file - you can ignore the peak power, since that is some bogus thing calculated by the software - that file did not have any power data from either of us).

Sunday I did an easy 1h recovery ride on the trainer, and then it was a couple days off to tackle midterms and other school business.

Tonight, a few high(-ish) cadence intervals to work on form and to get the legs warmed up after a couple slow days:

17 February, 2010

Tonight's interval session

I figure I'll start putting some numbers and figures up here for the data junkies, and the rest of you can just ignore it if you find it as boring as it really is.

I got on the trainer tonight for 90 minutes, including 2x20 minute blocks of "Sweet-spot" aka sub-threshold effort. This is just hard enough that it requires concentration, to maintain but doesn't really inflict pain, at least not all at once. The cumulative effect is pretty significant though, and it's one of the best ways to squeeze high TSS workouts into small blocks of time.

Here's the ride:
I was able to hold the wattage pretty well, and was even considering a 3rd effort but a tight feeling in my left leg that wanted some stretching and R&R put a stop to that idea. I was getting the feeling that if I pushed through it I'd end up straining it.

Back tomorrow with another workout, hopefully.

14 February, 2010

Joyride150 report

This morning I headed off to Markham to meet up with a few friends at Joyride150, my first visit to the park. Upon arrival, I met with Brad and Jared and we set to work installing my old brakes on his new Gioda Espresso. Unfortunately his fork had IS tabs and I didn't have an adaptor for the front brake so we were only able to install the rear - but one brake is ok for a bike park, right? If you like skidding around corners it is. The bike looks beautiful and I'm sure Jared will be happy racing on it this summer.

I had my waivers signed at home so the membership card was a quick and painless experience. I paid my fees for the day and headed off to change. I put on arm warmers, but those came off after 1 quick warm-up lap. Throughout the day we would find the temperature quite comfortable when riding (even sweating a little when you get going on the pump tracks) but rather cold when you stop and are a little moist.

Overall the park was very fun and surprisingly XC friendly - the XC loop of course was good, with enough features to keep it interesting and a couple challenging features if you want to take the hardest line. Some relatively tame rock gardens (more like rock carpets?) but I still managed to crash trying to enter one parallel to the wood border, sliding along instead of rolling over it.

The pump tracks are a bit tight for the wheelbase of an XC bike, but are still fun and I found #2 to offer good enough flow to spend a fair bit of time on it. A few laps on the pump track are quite tiring and heavy on the upper body work. It's nice to mix them in with laps of the XC track.

The skinny lines are probably my biggest challenge, but I found I got significantly better over the course of the day. There's a nice progressive ground level line that goes right down to a 1.5" board in the front area. I was nailing that, so back to the sport skinnies I went - I can ride about half of them, half of the time. A few are completely beyond my reach right now, and the rest pose enough challenge to make it enjoyable and productive. I was happy to clean a few of them after a couple attempts, for sure.

Overall the park surprised me with what it had to offer for an XC rider, and also with how much space there was for a busy weekend day. While occasionally you'd get crowded or held up it was usually just a case of choosing another area for the moment and you'd have lots of space to yourself. I must say it was easy to log 4 hours of "training" and have it not feel laboured - I am tired, but since the load was distributed to my whole body my legs are not fried. That in itself is a great value to a racer who is doing base or the start of a build period. I will definitely return at least once this winter, and would be a regular visitor if I lived nearby.

13 February, 2010

Training update: winter singletrack, FTP testing, Joyride150

The title pretty much sums up what I've been up to lately. Trying to log the hours between some scattered trainer rides and getting on the mtb whenever possible. Singletrack conditions have been excellent lately with the relatively low amounts of snowfall and consistently cold temperatures to keep the base frozen. Today's snow was just a little moist which made the grip so good it was almost like summer, as long as you stay on the little stripe.

Last weekend was the Frostbike winter mtb race put on by the Shorthills Cycling Club in Port Colborne. They did a fantastic job and for a first time race it went off perfectly. Much effort was put in through the week prior to pack it down with club rides and trail work sessions. The weather cooperated and as a result racers were treated to great conditions. I managed 4th in the U30 category, since they separate out the overall M/F winners (so really I was the 5th fastest time in U30, and 10th overall for the men, if I have it correct). I wasn't too concerned with my performance so it was fun to go out and hammer for 3/4 of an hour and see what came out in the end. Lap 2 stood no chance of bettering my time but I went out anyway to get more riding in for the day. Fitness was definitely not my limiter here, but rather bike handling - these trails are relatively technical and with the winter conditions required my full attention to keep going where I wanted to.

This past week I did my first FTP test for the year at home, and the results were more or less as predicted. I still think I could do better for pacing, and push harder overall so I expect the numbers to go up as I get used to the protocol. Also, I think once the testing moves off the trainer and outside it will be a little easier. I've got a number in mind that I'd like to see by race season and with the next 8 weeks of build I think it is within reach.

Finally, tomorrow I am off to Joyride150 for the first time. I figure I need to check it out sometime, and meeting up with Jared to sell some brakes was the perfect excuse. It sounds as though I'll be meeting up with a few other friends throughout the day, so it should be nice to check out the park and socialize a bit in between as well. Hoping to get ~4 hours on the bike but we'll see how quickly I tire out. I do have pretty much no upper body strength... I will report back afterward with my thoughts on the park.

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