Tuesday, April 13, 2010

Here I go with tire experiments again

IBC finally got some Bontrager Team Issue 29-3's in. I've been wanting to run these on my new Gary Fisher Superfly. In the interim, when nobody local had these tires in stock, I went with some Hutchinson Toro tubeless ready tires. They are great all-mountain tires but not race worthy tires for dry or hardpack conditions. They are quite slow on pavement. The Hutchinson's went on the rim quite firmly, and I was able to inflate them just as easily as tubed tires with a hand pump. In fact, I ran the rear tire at 19psi through the gnarly Burlingame TT course with nary a burp. That rim bead design combined with the Stan's Arch rims has my complete confidence.

The Bontrager label claims these team issue tires weigh 600g. In the hand, they felt heavier than that. So I put them on the one tool every serious rider has in their basement, the gram scale. Sure enough, one tire weighed in at 725g, the other at 740g. That's 23% over the claimed weight. I could see 5-10%, but 23%? I thought I'd be saving half a pound over the Hutchinson's, but this was a wash.

So tonight I got around to mounting my new 29-3's. The first tire went on the rim way too easily. That right there gave me pause for concern. How secure will this bead seal be when running low psi over typical New England gnar? I tried to inflate the tire with hand pump. No matter how I fussed, the air escaped as if there were no tire on the rim at all.

So I go to the compressor. Even that took some doing to get initial rim seal. My procedure is to put a few pounds in, inspect the bead for even seating, then inflate the tire past normal riding pressure to firmly seat both beads around the tire. The tire is rated to 50psi. I put in about 45psi. I was grasping the tire in my left hand, ready to lift it to my face for further inspection, when the entire bead blew off the rim. W.T.F! My hand went completely numb and both ears were ringing fiercely. I couldn't even move my fingers, they stung so badly. Stan's sealant covered a quarter of the basement - floor, walls, equipment, even the ceiling.

Stan's sealant floor to ceiling

When I got over my initial state of shock, I was pissed. I paid good money for these top-of-the-line racing tires. Sure, I would never race them at 45psi, but if they blow off the rim at less than rated pressure just sitting there, can they be trusted at any pressure on rough terrain?

I did remount the tire, careful to not go above 30psi. Racing pressure would probably be around 25psi I think. My concern is that the bead is too "stretchy" to hold tight around rim. I hope to get out for a test ride on these tires Thursday. I haven't decided yet if I will race my 29" Superfly or 26" Racer-X on Sunday. I haven't had a trail or race mishap due to tires in a long time now. I hope the Bontrager's don't let me down.

Currently, my favorite tubeless racing and all around riding tire is the WTB Mutanoraptor. They don't last very long, but they roll fast and the low profile sticky rubber knobbies grip everything. I've been riding and racing these for many years and have yet to have a mishap with them. They are getting hard to find now and are not available in 29".  I keep trying other tires. I have a whole wall full of barely used tires, a collection that could rival the shoe collection Imelda Marcos amassed.  At least Imelda Marcos liked her shoe collection. I hate my tire collection.  Every time I see it I think about how much money is tied up in them.  Time to have an Ebay clearance sale.


CB2 said...

The tire being rated up to 50 psi is probably for with tubes; I don't think Stan's reccommends pressure that high for their rims.
I too loved the Mutanoraptor (still have a few new "in stock"); unfortunately WTB never came out with something as good for 29".
I'm pre-riding tonight. Supposedly they cut some new trails. That plus rain on Friday and Saturday might make tire choice crucial.

Dave said...

I have had a good time running Hutchinson Python UST. Several pairs, many miles, no problems, ever...One burp on the SM100. I don't even carry a tube when riding them. They roll pretty good too.

Colin R said...

I swear every year Bontrager f's up on the bead of one of their tire models. Last year I had the same problem with my 26" Mud X's, they went on the rim WAAY to easy, were tough to seal, and burped if you looked at them wrong. I never blew them off the rim, though.

All the other 26" Bonty tires I bought last year were fine, but I had two Mud X's an neither one was any good. I wonder if you're in for the same experience -- did you try the other 29-3?

Hill Junkie said...

Which rim did you mount the Mud X's on? The other 29-3 slipped on the rim equally easy. I was careful to not go above 30psi. I'll give them a go on some rough terrain tomorrow to see if they burp on me.

I've never had a UST tire burp. I've also never blown one off the rim. I regularly run the WTB Mutanoraptors at 50psi on Mavic Crossmax SL rims for paved/gravel climbing (then drop pressure for trail descent). In Tucson, I ran Kenda Nevegal's upwards of 50psi on Shimano XTR rims with no issues either. Both systems are UST. I think there will be a bit of learning curve using a tubeless-ready system.

Anonymous said...

Maxxis Ignitor's are great and lite - 600grams. I just started riding/testing them a few weeks ago. No issues. Or if weight is not an issue, there's a good reason people love Kenda Nevegal's. Little heavy, but great tire - front & rear!
-Brian in NJ

Anonymous said...

Bontrager tires and products are a huge disappointment lately. The tires are in my opinion a bad choice for tubeless since they seem to suffer from tears/punctures more easily then other brands that I've tried. The beads roll on easily and as you found out they roll off just as easily which leads to massive burps while riding.
The hubs on the MTB wheels they use are a total joke.

Big Bikes said...

Man, I had 0 problems with my
29-3s all last season (the XR1s...that's another story) they were my go-to tires. Maybe it's a bad batch or something.

I also had an amazing flat-free season with WTB wire-bead Nanoraptors set up tubeless a few years back.


solobreak said...

Always were safety specs when f-ing around with tires.