[mark in redwood city]

My 15yo son is just finishing his first year of mtb racing and wanting to ride 'cross. He raced a season of cross when he was 6 on his bmx bike but things/bikes are different now. Can he be competitive in 'cross on his mtb?
Cheers! Mark

 

[mark in redwood city]

I guess I should add that his current bike is a Giant XTC carbon fiber hardtail. Carbon bars, carbon seat post, carbon seat, disc brakes. Gearing is 1x10 (34x 11-42) It has Fox suspension forks on it that we were thinking of removing and replacing with size appropriate carbon forks. And getting as thin a tire as his Syncros wheels would allow.

 

[RadBartTaylor]

I guess I should add that his current bike is a Giant XTC carbon fiber hardtail. Carbon bars, carbon seat post, carbon seat, disc brakes. Gearing is 1x10 (34x 11-42) It has Fox suspension forks on it that we were thinking of removing and replacing with size appropriate carbon forks. And getting as thin a tire as his Syncros wheels would allow.

Yeah - should work just fine to test the waters. Depending how strong he is, the gearing may hold him back. I've raced MTB's on cross courses, they work "OK". Without going into all the pros/cons, I'd just run the bike as is if he's used to it. It won't hold him back much on a tight technical course, it's going to be more of a limiter on a open flatter course.

The more I started racing cross (from MTB) the more I realized cross bikes really do work better 95% of the time....but there is an adjustment period where I felt like I was a bit slower on the cross bike. After I adjusted, it's faster, but for a first year fella, he's probably going to do better on a MTB he's comfortable with including sus fork and tires.

The only reason I'd downsize tires would be for mud, keep them as is for dry / intermediate courses, just run a lower profile tread pattern.

 

[jestep]

I wouldn't worry too much about him being competitive out of the gate. CX is a whole different type of event and community than mountain biking. He should be fine on his mountain bike, go to a few events or find a local CX group and let him get some exposure. You/he should learn fairly quickly what direction you want to go.

 

[jimPacNW]

Check to see if you're races are USAC sanctioned, and if you'd need a license. If so, they may have more specific rules, including tire width. If it's non-USAC you're probably ok on mtb tires, but check with the rules of the series.
Quite a few jrs around here race on mtbs, my kids always raced hardtails with flat bars.
I've had my best cx races on my 29er hardtail, I'm better at mtb (masters cat1) and do ok in masters cat1 cx. I've raced my hardtail in cx a few times, mostly when I know it's going to be a rough or more hilly (or a lot of sand and off-camber corners). I find the hardtail mtb is only at a disadvantage (for me) when we're racing on soft muddy sod, where the tires are sinking down into the muddy grass cutting a groove, displacing the mud, - the added drag from the wide tires made it about 5-8 places slower (not a whole lot, but noticeable, just a couple of minutes on an hour course). The other downside is it can be hard to pass the guys on the 17 pound bikes on the climbs, and I then get stuck behind them on the descents (where I'm a bit faster). A really sandy or rough course is going to favor the fat tires quite a bit. I've swapped in my carbon rigid fork, and it's about 2 pounds lighter but not really necessary for racing imo, if I were going to race the mtb on a smooth course I'd put the rigid fork on.


Unless your kid is a total beast and very competitive in cat1 open mtb, a 34 front on a 29er (I don't think you mentioned wheel size) would be more than adequately big, I run a 32 front on the 29er and it's plenty big. Even on a 26er, unless the courses are super smooth, a 34 front should be fine, he just might spin out on a paved descent. I'm certain most people new to cx imagine really hauling and carrying big speed, but the reality is you're grinding along on rough ground not very fast for 90% of it.
I always have a little more fun racing my mtb, but our courses are generally pretty rough. There's one especially rough course where a couple of cat1 open fast guys brought there fs bikes, they didn't smoke the field or anything, but I think they were less beatup the next day.

 

[mark in redwood city]

Yeah - should work just fine to test the waters. Depending how strong he is, the gearing may hold him back. I've raced MTB's on cross courses, they work "OK". Without going into all the pros/cons, I'd just run the bike as is if he's used to it. It won't hold him back much on a tight technical course, it's going to be more of a limiter on a open flatter course.

The more I started racing cross (from MTB) the more I realized cross bikes really do work better 95% of the time....but there is an adjustment period where I felt like I was a bit slower on the cross bike. After I adjusted, it's faster, but for a first year fella, he's probably going to do better on a MTB he's comfortable with including sus fork and tires.

The only reason I'd downsize tires would be for mud, keep them as is for dry / intermediate courses, just run a lower profile tread pattern.

I was wrong on the 1x10, we are actually 1x11. Should we add some teeth to the front sprocket? I was gonna get rid of the front suspension and get rigid carbon, you think not?

 

[mark in redwood city]

Races are USAC sanctioned and it says all bikes allowed.

 

[Dream Plus]

Races are USAC sanctioned and it says all bikes allowed.

I think the only restriction would be no bar ends unless it's a UCI race.

 

[jimPacNW]

Last night, a racer friend with more experience than me (her sister is a pro) was telling me that UCI measures tire width (USAC does not), and USAC generally requires drop bars (possibly different regs for jrs), so check that with your promoter.
DreamPlus; Good point on the bar ends, every cx race I've ever done (since '91) has had a ban on bar-ends for flat bars/mtbs; I think it's mostly about easily they snag on the course tape and would tear down the course, and could cause a crash and pile-up from snagging on the course tape.

I'm guessing your son's bike is a 29er; I kept up with a Jr Nat champ for a short time on a slightly descending gravel section on my 29er with 32 front, - 32 front is plenty big on a 29er for cx. If you have a carbon fork, go ahead on put it on, but don't buy one for cx, it's not going to make much of a difference, and it would only help on a smooth course.

 

[IKnowYouRider]

and USAC generally requires drop bars (possibly different regs for jrs), so check that with your promoter....
DreamPlus; Good point on the bar ends, every cx race I've ever done (since '91) has had a ban on bar-ends for flat bars/mtbs;

USAC does not require drop bars, but does ban any forward facing extensions for mass start racing.

-w

 

[mark in redwood city]

Thanks for all the info. guys! He joined the Rock Lobster Junior CX team over the weekend. We will start the CX season on his current bike and add the carbon forks, leave the flat carbon bars and possibly go narrower on the tires once the rains start.
First we have to finish the mtb season. We have the High school state finals this weekend (he was voted "Most improved Athlete" in Northern Ca.) Then we have 1 more series race in Monterey and the Series final. He is first in points in Cat. 3 and second in Cat 2. Then we can focus on CX.
Cheers! Mark

 

[KingOfOrd]

Congratulations to your son and his improvement. Since you're racing in NorCal, be sure to check out the CCCX series. Great grassroots series and typically a good junior turnout.

 

[mark in redwood city]

Congratulations to your son and his improvement. Since you're racing in NorCal, be sure to check out the CCCX series. Great grassroots series and typically a good junior turnout.

We love the CCCX races!!

 

[KingOfOrd]

We love the CCCX races!!

Right on, I think y'all are more excited to start racing 'cross than I am, and I even added running to my schedule(just for 'cross).. It'll be my first time racing gears in over 10 years, sold my last SS bike earlier this year.

 

[mark in redwood city]

Right on, I think y'all are more excited to start racing 'cross than I am, and I even added running to my schedule(just for 'cross).. It'll be my first time racing gears in over 10 years, sold my last SS bike earlier this year.

Are you in Ca.? Do you race CCCX?

 

[KingOfOrd]

Are you in Ca.? Do you race CCCX?

Yeah, Monterey. I grew up racing all the CCCX races, I only race the CX series now though, I might do the last two XC races to make sure the engine is running strong for CX. The Surf City CX races are super fun too, especially the Halloween extravaganza.