Wednesday, December 3, 2008

Review: Challenge Grifo Tubular Tires 32c

I bought these tires from the Echappe Equipment people at Gloucester after I flatted one of my Tufo's in the last lap of the Sunday race. Turns out that the Tufo took tire sealant moderately well and after a full bottle of Tufo sealant (twice the recommended amount) the tire is still rolling 2 months later.
I stretched the Grifos for one week each, re inflating them to 60 psi every 48 hours, since the Grifos loose air quickly due to their latex tubes. Both tires were keep in clean, dry conditions throughout my pre-mounting ownership. They appeared to be clean and free of dirt when I purchased them.
I dry mounted the tires twice on their intended homes, Edge Composites 2-68 rims (review to follow) so that I would be able to foresee difficulty and minimize mess when I was mounting them with glue on them. They were a tight fit. But the tires were supple enough that they were able to rolled over so that you could "flip" the base tape into place on the final section.
On initial application, the basetape absorbed lots of glue. The exposed cloth basetape has no coating on it, which eliminates an annoying and time consuming step in tubular mounting, scraping the protective coating off. But this lack of coating means that the tires must be stored and transported in dry, clean conditions before mounting. the tires do not arrive wrapped in any covering at all, which maximizes opportunities for contamination before the tires are mounted.
I found it necessary to apply a second layer of glue to the basetape, which I normally do not have to do, but thought prudent considering the low intended tire pressure and the forces involved in cyclocross.
Mounting the tires was certainly not easy, but if one used a hand over hand method of pulling away from the stem on one side then the other, the final section had enough slack to allow the mounter to use the afore mentioned roll and flip method of finishing the mount. The tire sat fairly well even before adjustment. The tight fit makes me feel that the chances of rolling a tubular while cornering is low.
Since the tire is supple, it was easy to adjust the lateral alignment of the tire. Furthermore, the basetape is symmetrical, so that one can sight line the tire; there should be an even amount of basetape showing on either side of the tire.
After adjustment, rolling around with low pressure and a rider on a bike and then inflating to high pressure, the tire was very evenly round.
The ride quality of the tire is hard to get used to for someone coming from a road background. I have ridden tubulars in cross before, but the Challenge is a different experience. At low pressure (under 30psi) the tire feels unstable, squishy. It moves laterally when out of the saddle on a straightaway. On my first ride, I had to stop and check my quick releases three times, as I thought that my wheels were loose. At this low pressure the tire deformation in a corner was disconcerting. The tread would roll up onto the braking surface. I did not loose grip in the corner, but this was a true test of my gluing job. No failures.
I found that I am more comfortable running these tires at a higher pressure than I normally run my cross tubulars. Normally I run about 32psi in back, 28-29 up front. With the Challenge Grifo's I found that my 175 pounds feels perfect with 38 psi in back, 34 up front. Obviously these numbers are tweaked to reflect course conditions. At the aforementioned pressure, I bottom out the tire infrequently, which is desirable when you are riding wildly expensive carbon tubulars.
The tread pattern is a good balance between high grip and low rolling resistance. I have the chevrons pattern on the tire pointing forward on both the front and the rear. Reportedly, you can run the chevrons pointing backwards in the rear if you want more traction, but in doing so you will increase rolling resistance. The open tread pattern sheds mud well, while the sidewalls tend to collect a thin layer of grime in their fabric. The only tire that I have ridden with better grip is the Michelin Mud 2.

There are problems with these tires:

First, the thread began separating from the casing almost immediately after being ridden for the first time. This ride was in dry conditions, on a buffed out course, with high tire pressure (50 psi). A friend of mine has multiple sets of Challenge Grifo's and Fango's where the tread was seperating from the casing when he removed them from the box that they were shipped in. Clearly this is a manufacturing defect that Challenge should be ashamed of. I was able to address the problem with a tube of vulcanizing glue and some patience. I felt that my fix was less trouble than trying to warranty a tire that had already been mounted. After I ruined one of these tires in a race, I was easily able to remove the tread from the base tape with my bare hands. As I have stated, the problem can be fixed, but should you really have to fix a $100 MSRP tire before riding it?

Second, the supple casing is thin and vulnerable to puncture. In my second race with these tires, I sliced the sidewall of my rear tire in a corner. The tire was unable to be repaired. I am convinced that if I had been riding my Tufo Elite30's I would have ridden away without a puncture. Obviously, suppleness is a function of this sidewall thinness; its a tradeoff. Some vendors recommend using Aquaseal sidewall sealant to make the sidewall more robust. I find this option unpalatable for a number of reasons:

1. Should I really be required to fix a $100 tire before riding it?
2. If Challenge wants the sealant on there, can't they just do it in the factory and save me the trouble?
3. Aquaseal adds significant weight. I just spent $1000's to shave precious few grams off of my rotating rims, why am I going those grams back in the form of latex?
4. The Aquaseal often peels and looks horrible. Peeling latex on your sidewalls is the opposite of PRO
5. Since you can't really create a true seal with this stuff (are you really going to paint it up onto you rims to seal it for real?), this Aquaseal works to seal in the water instead of sealing it out. Go take a look at a set of Dugasts that have been sealed, don't they look rotten near the rim where the water has gotten in and caused the cotton sidewall to decompose?

Third, latex tubes don't take standard tubular tire sealant well. Obvious, they are lighter and they may offer lower rolling resistance, so this is a tradeoff. If you flat them, you are probably out of luck. Some reviewers have suggested trying Stan's Sealant on these tubes or even Vittoria's PitStop, I can not comment on the effectiveness of either remedy.

The short story is: If Challenge could deal with the issue of the tread separation, they would have a world class set of tires. The tires offer great ride quality, good deformation and grip in corners, low rolling resistance and good mud shedding, but the quality issue would prevent me from choosing Challenge tires in the future.


Yash Katsumi said...

Agreed. Aquaseal stuff is fricking heavy. I haven't measured, but it is like a quarter pound per wheel.

RMM said...

Yeah, you have those unmounted FMB's with the sealant on them. They are heavy like a string of link sausages. Certainly heavier than a box section rim.

Exclusive Media said...

great read.

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