Editor’s Note: Our European correspondent, “c_g”, has filed his first report in his review on the Geax Saguaro tubular mountain bike tires.
GEAX SAGUARO 29er tubulars – out of the box and mounting: by “c_g”
What is all the hype about the tubular tires in the mountain biking world about? “SUPERIOR GRIP, UNRIVALED COMFORT, PROVEN RELIABILITY” – These are the claims by GEAX on their MTB specific tubular tires, which soon will be released in the 29er format. I have been lucky to receive a pair of those tires plus the fitting rims before their official release – (Yeah, sometimes it is plain cool to be a tester. J
Here is a short recap for those that haven´t followed the last Euro posts. The GEAX SAGURAO 29er tubular tire is to be seen as the bigger twin brother to its 26” sibling. It shares
1, The ultra high count cotton casing with 290 tpi (most MTB tires are between 60 and 120 tpi !!!)
2, The (almost) exact width of 2.0” (50,8 mm measured at 2.5 bar) and
3, The well established SAGUARO tread pattern. The casing is sewn up with a latex tube inside, creating a airtight system by itself. (strange to be able to pump up a tire before you ever mount it J).
The two tires I have received weighed exactly 740 g and 746 g. Like I stated before, GEAX was not wanting to make the tire the lightest around but aimed to get riding characteristics and reliability right. Did they? Let´s see when I get to ride them – but first let´s mount.
Fig. 1 all the ingredients for a great wheelset – partly built
Note that GEAX´s mother company VITTORIA has been in the leading edge of tubulars for roadies for decades. But despite this vast experience the translation of this technology into the MTB segment (and especially the 29er format) has not been an easy one, shown by the long time from first spy shots in 2008 up until the final release just now.
Oh yeah, before I get into the gluing/taping controversy – just one more word on the tires Design and Technology: The GEAX SAGUARO tubs are 99 % hand made (basically just the tread pattern isn’t, as it’s done in a standalone mold and then hand glued to the casing) – with about 8 hrs working time on a single tire. The GEAX tubulars are hand sewn at the inner side and the tread is hand glued (as opposed to vulcanizing):
“The real advantage of this technology is flexibility: not having the casing heated up along with the tread (which the vulcanized ones are), thus keeping it away from heat stresses and thread rigidities which occur due to it, resulting in the most flexing and supple combination (casing itself + tread) possible. Vulcanized tubs are mid to low end in the road range… (cheaper and faster way of manufacturing).”
(by S. Bressan, designer & product manager of GEAX)
But there is a tiny downside to this technology, too. Apart from the more elaborate production it means there is a small seam protruding ever so slightly all around the contact area. Since this interface of two surfaces is what ensures the positive bond between tubular tires and rims, some rim manufacturers go as far as to design a minor groove along the center of the rim. My sample rims didn´t … but more on that later.
Fig. 2 The inner cavity of the rim is supposed to resemble the tire´s curvature in the best possible way.
GEAX also pointed out that the casing material is cotton (rather than nylon) which makes them much more compliant. While nylons can be a bit lighter they are more elastic and less flexible, translating into a much clincher tire like roll-over character and less comfort. Also Nylon can only be vulcanized and has an overlap of plies with strong glue in place of the hand made sewing of the cotton ones.
My sample tires had one minor imperfection: That is a minor unevenness in tire width near the valve. After speaking with Geax’s technicians it turned out to be a minor defect due to pre-production model and will not affect the production models. In my sample it is only detectable in width, not the rolling outer circumference and so I suspect it won´t actually affect the tires´ride.
A Word On Rims & Build: The rim provided to me by GEAX is made by AMBROSIO and weighed ~ 410 g at a 25 mm width (beware, there rims seem to be currently unavailable). Rumors are there will be an EDGE composite rim (said to be even grooved) introduced alongside the tires´ official introduction at Sea Otter Classic and there are the FRM tubular rims mentioned before (see here), which should be available by end of April.
I will spare you with details of the wheel build. The only difference in lacing the wheels was that the rims do have a very large inner cavity, making it extremely easy to drop a nipple inside the rim (some form of nipple guide is strongly advised).
My particular wheel set consists of Shimano 965 hubs (oldies but goodies) and SAPIM CX-Ray spokes (those frequent readers know: I dig them) and ended up at 3144 g for the set (1485 g front; 1660 g for the rear) – without cassette, and rotors. Not the most weight conscious but for my intended riding just right.
Mounting: Once the wheel is built you need to fix the tire to the rim which can be done in two ways. To create a safe connection between tubular tire and rim you can either use the good old way of gluing by some special cement (e.g. GEAX MASTIK´One), which is really messy and time consuming (unless you are an expert at it ) or by using a double sided adhesive tape (like offered by TUFO).
The taping version is a very fast, clean and simple way but out of my own experience creates a weak bond. You simply peel off the protective tape on one side and fix it to the rim (leaving the tires side still covered). Then you put on the tire, inflate and adjust for a balanced and wobble free rotation (very vital and best checked on a stand) and then simply peel the tire facing seal off between the tire and rim (that is if you have considered to have a small end sticking out at the end ). After you’ve fiddled around with it the first time, it becomes a thing of 5 minutes and you are set. When riding at higher pressures (2 bar and higher) I have been successful with tape only, but generally I apply some glue – to be on the safe side.
Fig. 3 +4 The double sided adhesive tape is a easy and mess-free way of mounting the tire to the rims – it is near invisible and is rideable immediately after mounting; but the bond isn´t the strongest.
The gluing process is fairly elaborate: First you apply a thin layer of glue on the rim, then let it dry overnight, then another layer on the rim and a layer on the tubular tire (after having cleaned the base tape with just soapy water), let them dry for 10-20 minutes, mount the tub slightly inflated, center it and then pump it up to max. . Then you need to let the glue cure for min. 8 hours and you are ready to go.
But beware – the special glue (by some manufacturers aptly called “Cement” is the some of the stickiest and ugliest form of glue you have ever worked with. Chances are when you have gotten the tire mounted and sitting wobble free in place the entire rim, tire will look like my 4 year old´s attempts at handcraft work and much of your clothes will be ruined forever. (I am speaking out of my own hurtful experience).
After having mounted several tubular MTB tires over the last years (all in 26” ), I personally found the best way for me was a combination of both. First I taped the tire to the rim like described (makes for a easy wobble-free installation) and then I would deflate, and apply a small bead of glue along the outer edges of the contact area for the ultimate of bonding. If any of you CX racers and seasoned tubular riders have a better system, please do let me know! I think in this technology we will need to look hard at what the roadies have gained in experience over the past decades.Fig. 5 This tire was glued only (not the combination method mentioned in the text – upon close inspection you can see lots of glue all over the edges, the rim and the tires. I have been told the experienced roadies can mount tubulars with glue mess free and very fast (apart from curing which always takes hours).
This is what GEAX´s designer & product manager S. Bressan had to say on the taping vs. gluing topic:
“As handmade tubular manufacturer, we always highly recommend to use glue/mastic over adhesive tape to glue tubulars on: Due to the small sewing protrusion on our tubulars (mentioned above), the tape cannot fully adapt to it and fulfill all the empty space that remains between a sewed casing and a flat tubular rim. The glue instead adapts to it and fulfills the groove all the way over the circumference. Other than that, glue strength is also more than tape by chemicals. If you add these two things, you find out that glue is almost twice reliable than tape.”
In the event of having to change your tire, you will have a very easy time separating tire and rim when taped but struggle some time when properly glued. But the same principle applies concerning the strength of the bond that keeps the tire from rolling off. Simply because I have had incidents of tires popping off the rim (mostly when experimenting with tubeless setups) – I had no desire to have that happen to me in my tubulars – so I eventually glued all of them.
Ok, that is done – my first ever 29er MTB specific wheel is ready to prove its worth – stay tuned.