Stretching some new challenge CX tires today - valve stem isn't long enough. Is there any chance this *isnt* a removable valve stem? I don't want to ruin a new tire....

Jules said:

Who do you think the first rider up the hill behind me was that day? Murray.

sounds like an attempt to dominate strava or a race if you were in one. clever, lynn, real clever...

Jules said:

Stretching some new challenge CX tires today - valve stem isn't long enough. Is there any chance this *isnt* a removable valve stem? I don't want to ruin a new tire....

I'd assume it's a removeable valve stem.  I'm sure the Challenge website has info.  Besides, it's pretty easy to test--just take the little plastic valve core removal wrench and turn.  THe plastic will break if its not removable.

Jules said:

Stretching some new challenge CX tires today - valve stem isn't long enough. Is there any chance this *isnt* a removable valve stem? I don't want to ruin a new tire....

I'd assume it's a removeable valve stem.  I'm sure the Challenge website has info.  Besides, it's pretty easy to test--just take the little plastic valve core removal wrench and turn.  THe plastic will break if its not removable.

The valve doesn't have a flat spot for the valve wrench.

Challenge tires are removable core.

eragot said: Challenge tires are removable core. Thanks.  Just have to work up my courage to really twist on them...

some of the eurobike stuff looks awesome....this leaf spring suspension is genius...wonder how it dampens though...

And that tiny front chain ring paired with the ginormous cassette suggest that your inner most cog is your tallest gear ie you shift your rear derailleur backwards to go thru the gears? Is that something brand new that's never been done before?

Does anyone have a Garmin 510 ?

These seem to have a bunch of neat features that could be useful and the reviews all seem very positive, however none of the reviews make any mention of how to record intervals.

I'm currently using a Powercontrol 7 and it's super easy to record intervals. I really need the Garmin to be just as straightforward. If it isn't it would seem flawed as a training tool ?

What chainring sizes are you running for cyclocross?

Patrick, I run a 46 and the only time I've wanted something bigger is when Whitey pipped me at the line to take 5th from last at last years cx club champs.

46x38 with 13-26 cassette.  46x13 has been used when sprinting on the road during cx races.

front derailleur again.  after mr. yang's questioning of a page or two ago, i let out some FD cable tension and it no longer rubs in the crosschaining (big chainring x biggest rear cog) combination. however, after crosschaining along merrily in this gear for a period of time, the chain will start to come off the chainring, only to be pushed back onto the chainring by the derailleur.  it cannot come off because the derailleur is too close, even in the trim position.  does this mean my chainring needs to be replaced?  chain is new.  

Erika, email me off-forum. I just upgraded a bunch of cross parts, and am looking to sell much of what you probably need. I would love to avoid eBay and benefit a KCCer at the same time. Email: joaquin.cdebaca@gmail.com

Last year I rode most of the season with a 53/39 - 13/26 setup. I never used the 53 and was just too lazy to swap it for a smaller chainring. So essentially, I had a single 39 chainring and it was fine. I think your 12-27 would also be fine, at least to get started. You can but a replacement for the 53 later (e.g., 46 or 48 which are more appropriate).

I think when your chain comes off your chainring, it generally means your front derailleur is not adjusted correctly.

Erika, I currently run a 39x48 on my cross rig and almost never use the "big ring." If you truly want a cross racing bike, and you are starting from scratch anyway, I'd get yourself a 46-tooth "big" chainring and be done with it. That said, if you already had a 53x39, you could just leave it in the little ring for your races, as David, a very good CX racer did...but if you are starting from fresh. I say, "come correct."

Erika - most people set up a cross bike with a compact crank so that they can have the chainrings mentioned up above in the thread. Compacts will come new with 50/34 standard for road bikes. If they are set up for cross bikes they'll have something more like 46/38. Like this one on ebay. Obviously purchase one that fits your specific bottom bracket type. You don't have to have a compact as David points out, but you'll only use the 39 during a cross race. Your cassettes are fine any way you go.

ian ellis said:

Does anyone have a Garmin 510 ?

These seem to have a bunch of neat features that could be useful and the reviews all seem very positive, however none of the reviews make any mention of how to record intervals.

I'm currently using a Powercontrol 7 and it's super easy to record intervals. I really need the Garmin to be just as straightforward. If it isn't it would seem flawed as a training tool ?

@Ian - unrelated I just got a text from a friend saying that Garmin ...

Jeffrey White said:

I think when your chain comes off your chainring, it generally means your front derailleur is not adjusted correctly.

I have never expected quietness when cross-chained. I only cross-chain when I absolutely cannot make a front-derailleur shift, and put up with the noise until I can shift to the proper chainring. 

i guess that's my question: is it a chainring issue or an FD issue when the chain is able to come slightly off?

Jeffrey White said:

I think when your chain comes off your chainring, it generally means your front derailleur is not adjusted correctly.

I have never expected quietness when cross-chained. I only cross-chain when I absolutely cannot make a front-derailleur shift, and put up with the noise until I can shift to the proper chainring. 

I also don't think "whisper quiet" should be a goal when cross-chaining. Maybe I'm too old school here, but if you are cross-chaining, you need to get familiar with other gearing combinations.

so what you're saying marc is that although you pedaled uphill both ways in the snow just to get to kindergarten, you never crosschained?

Re: chain drop. Even with a single ring and no derailleur it is possible for the chain to drop off the ring. It all depends on the how much out of alignment the ring and cassette cog are. At a certain point the teeth of the chainring will not be engaging the chain smoothly in the middle of the chain, but will instead be catching the inside of the outer plate on chain, and in some cases hitting the outer plate directly. This when your chain is at risk of coming off.

The risk increases with short chainstays and decreases with long ones. Which is why track riders for years have obsessed about chainline, and why this is usually less of an issue on CX bikes than road bikes.

2 sidewall/tire questions.

Brendan,

I disagree with @JP. I wouldn't race tires with visible sidewall fraying.
Especially in light of Jeff's episode (though he reportedly hit a pothole which might very well have caused a massive pinch flat) and in light of your experience having the same brand (and perhaps the same batch) of tires already fail in a similar way.

I've had tires fail due to side wall perforation. I tend to believe that such failures are initiated by some mechanical insult to the tire followed by aging, not a spontaneous failure due to manufacturing defects. But I don't have any specific evidence on this point. Come to think of it, however, I had some Vittoria Rubino Pros that I think had a sidewall give out after not very many miles earlier this year. I think that may have been a manufacturing problem, as it's mate is still going strong.

I may ride my tires further into the ground than JP or I may buy cheaper tires (or both). 

My solution for your tire is to use it for training - just not with me on a cold winter day(!)