Mountain bike racing while road training.
 

I’ve been invited to race a leg of a 24-hour mountain bike race that is held 2-weeks before what I consider my “a” road race. I’ve been mountain biking for fun since I was a kid, but not too much racing (I do race Cross though) the people I would be racing with are pretty serious about trying to make a run at winning the thing, so I will want to make sure not to be the weak link that prevents the win. The race is nearby, so I thought I’d run through the 15-mile course once a week in place of one of my shorter training rides so that I know all the right lines and such. I would likely get 4 or 5 laps in during the race. I’m thinking the 60-75 miles of intense mountain biking will probably serve as the last long/hard ride before I begin to ease off a bit to taper for my stage race two weeks later.

Assuming I don’t crash and injure myself in the 24-hour race, how much, if at all, would the one mountain bike ride/week in place of a road ride, and the race in place of my last hard training ride impact my fitness for the road race?

Probably not much at all. Aim to ride the weekly mtb ride at a similar intensity that you would on the road.

You're doing this thing (road racing and training) for fun right?
Do it.

Replacing your easy or "skills" day on the road with the mtb ride is probably the best option, as mtb riding can be discontinuous and thus not the best choice for steady-state interval training, in lieu of long dirt climbs of course.

Yeah, fun, Sarbucks gift certificates, and knick-naks glued to wooden plaques, at least until team Garmin decides to take a chance on a 32-year-old Cat4 160-pound climber, I do really want to make cat 3 this year though. I was thinking the mountain bike ride would replace one of my easy spinning days.

I'd say go for it.

I participated in a 12hr mtb race on a pretty fast squad about 18mo. back. It was a blast.

It'll be good for you. Upper body work, training lots of different systems, and you get to punch your man card.

All this, plus it's a freakin' blast.

I'm going to take the counter argument and say that since it's two weeks before your A race, perhaps you should consider bagging it.

I'm with Kensuf on this 24 hr mtb events are tough.... night riding is a different beast since you are so close to your A race the fatigue may not be worth it let alone being tired at 3am doing a lap and hitting the deck hard

Yeah whatever you do make sure not to have any fun at all before your A race.

Fixed that for you.

To add to this.. You said your friends wanted to be competitive in this event. That means the pressure will be on you to perform as best as you can, which opens up those risks.

If you were just doing this for chuckles and grins then I'd say go for it, but since you plan to actually race it...

So are you going to listen to the prudent disciple on your left shoulder or the fun-loving maverick on the right?

Muahahahahahah!

Valid point. So maybe take a look at the course. If it's sketchy and you're going to have to bomb through a lot of crazy stuff, then I'd be more prone to holding back. I think a lot of endurance MTB races aren't all that technical. If you don't think it's going to be likely that you crash, then I don't think the added stress is going to hurt you 2 weeks later, in fact, it might be a nice way to wrap up Build 2.

that is a valid concern, but notice that the op asks us to only consider the fatigue aspect. i don't think that a six hour mountain bike ride two weeks prior to 'a' race day is going to adversely affect his fitness. i also don't believe that a 1x a week mountain bike ride in place of a shorter training ride will hamper his performance.

Yeah that is definitely one of my bigger concerns. I’ll have to run through the course and see if I can get through the more technical portions (although I am familiar with the trails in question and they aren’t too bad) at a speed I’m comfortable that I can do safely and still finish a lap fast enough to keep pace with the faster lap times from last year’s results. If I can’t do it without feeling like I’m taking too much of a risk, I won’t do it.

I'll agree that the 1x a week mountain bike ride isn't going to hamper anything. As a matter of fact, I've been doing that same thing myself for a bit now that it's cool here :) (and am mtb'ing this evening).

But I still wouldn't do the 24 hour race.

I say go for it
 

because it will be a fun day with friends and a good workout. (fun in a painfully competitive way)

My reply would depends on what your "A" race is.

mountain bikes are a waste of perfectly good materials that could be used to build road bikes.

You can't take a road bike off any sweet jumps.

It's the Wenatchee Omnium http://www.bikewenatchee.org/81/index.html

I've never been to New Jersey, but I have to imagine your statement is more true there than it is here.

FWIW I'm fairly certain there are more mountain bike races within 90 minutes of here than anywhere else in the country. I still think it's a waste of perfectly good carbon, aluminum, steel, etc.

I wasn't thinking about races, we don't have enough population to support that many races, I was thinking more about trail access and the fact there are parts of town to which the shortest commute is on single-track trails. I get it though, you don't like riding off road. If I didn't live two blocks from a trail that connects of 100s of miles of trail, I probably wouldn't bother with it either.

hater