Cycle Cross v MTB on a climb

Pict

Any one with experience of riding a CX bike out there? Would a CX bike give one an advantage over a MTB in a non technical straight forward off road climb? Mostly on fire tracks. We have a wee KOTM comp in our club, and the chap that done it on the CX bike blew away all the other times. I look forward to hearing your thoughts on this thorny issue.

cooldad

No doubt. So what's the question?

Chinley Churner

Concur 100%... that's why many off-road triathlons and duathlons where the bike courses tend to be quite non-technical don't allow them.

stubs

On a recent ride I was on my rigid single speed hardtail with 1.75 tyres and I blew everyone away on the first smoothish climb. Going down the other side on a washed out landrover track my eyeballs nearly rattled out, I nearly filled my shorts several times and my hands were battered to pieces. I finished the 15 mile ride feeling like someone had kicked the carp out of me and could barely move the next day.

So yes you will go up a fireroad faster but you will be so far behind on any sort of descent it will not be worth it.

Pict

Thanks for your insight and illuminating replies. It was a KOTM comp, up only. CX wins every time, unless your a walrus.

IShaggy

The answer isn't obvious.

When climbing at low speeds (< 16kph) wind resistance becomes negligible relatively to the force required to overcome gravity. A rider on a CX bike will generally have a more aerodynamic position, but this has a negligible affect on a climb.

If both bikes have the same width tires and tread patterns then the CX bike - with larger wheels - will have greater contact area with the ground and hence greater rolling resistance. But larger wheels tend to be heavier, hence the CX wheels will have greater inertia. Overall, I suspect that these effects are negligible.

Which is lighter - a CX bike or a MTB? Generally the CX bike will be lighter. Spend £1000 on a CX bike and it'll most likely weight somewhere between 18-20lbs. Spend the same on a hardtail MTB and it'll weigh 25lbs. Is 5lbs significant on a climb? Let's say that a good cat 3 70kg cyclist has a VO2max of 60ml/min/kg. Adding 5lbs is equivalent to reducing VO2max to just over 58ml/min/kg. Which is enough to give the CX rider the edge on a climb. But of course this edge will be lost if the rider likes his pies. Having said that, a lighter bike will require less effort to accelerate - see below.

And finally, we need to consider climbing economy. Cadence has a significant effect on cycling economy. Typically, cadences between 80 and 90 rpm are most economical. But when climbing, cyclists typically pedal at a lower cadence due not having low enough gearing on their bikes. The lower cadence results in a greater variation in force during the pedal stroke particularly on hills where there will be a significant acceleration and deceleration with each pedal stroke. MTBs typically have lower gearing than CX bikes so it may be easier to maintain a higher cadence and pedaling efficiency on the MTB. But CX bikes have pretty low gearing anyway, so unless the climb is very steep the CX rider should be able to maintain a reasonable cadence.

Bottom line is "it's not about the bike". So if the CX rider blew away the rest then he's either lighter or more powerful.

cooldad

I think you are overthinking it.

Raymondavalon

cooldad wrote:

I think you are overthinking it.

+ potato

Debating on a no brainer Topic..

milfredo

Sheesh + yawn.

Northwind

Does depend a bit on the surface though, suspension can maintain momentum sometimes where rigid can't... I can haul my 35lb full suss with its big draggy tyres and squashy suspension up the clattering path at innerleithen faster than my 22lb rigid mtb, because the rigid needs to clonk over every last rock on the climb (it's surface with rocks roughly the size and shape of half-bricks) It's like having square wheels.

MountainMonster

IShaggy wrote:

The answer isn't obvious.

When climbing at low speeds (< 16kph) wind resistance becomes negligible relatively to the force required to overcome gravity. A rider on a CX bike will generally have a more aerodynamic position, but this has a negligible affect on a climb.

If both bikes have the same width tires and tread patterns then the CX bike - with larger wheels - will have greater contact area with the ground and hence greater rolling resistance. But larger wheels tend to be heavier, hence the CX wheels will have greater inertia. Overall, I suspect that these effects are negligible.

Which is lighter - a CX bike or a MTB? Generally the CX bike will be lighter. Spend £1000 on a CX bike and it'll most likely weight somewhere between 18-20lbs. Spend the same on a hardtail MTB and it'll weigh 25lbs. Is 5lbs significant on a climb? Let's say that a good cat 3 70kg cyclist has a VO2max of 60ml/min/kg. Adding 5lbs is equivalent to reducing VO2max to just over 58ml/min/kg. Which is enough to give the CX rider the edge on a climb. But of course this edge will be lost if the rider likes his pies. Having said that, a lighter bike will require less effort to accelerate - see below.

And finally, we need to consider climbing economy. Cadence has a significant effect on cycling economy. Typically, cadences between 80 and 90 rpm are most economical. But when climbing, cyclists typically pedal at a lower cadence due not having low enough gearing on their bikes. The lower cadence results in a greater variation in force during the pedal stroke particularly on hills where there will be a significant acceleration and deceleration with each pedal stroke. MTBs typically have lower gearing than CX bikes so it may be easier to maintain a higher cadence and pedaling efficiency on the MTB. But CX bikes have pretty low gearing anyway, so unless the climb is very steep the CX rider should be able to maintain a reasonable cadence.

Bottom line is "it's not about the bike". So if the CX rider blew away the rest then he's either lighter or more powerful.

Do you also spew so much when someone asks you how many drinks you've had? Well, given the grams of carbs i've eaten I now sit at 80% drunk max............

Anonymous

As far as I can see, CX climbing on anything slightly rough (grass, dirt is rough enough) basically involves carrying the bike uphill while running.

As they're lycra clad fitness obsessed types, they should be able to run up a hill faster than I can cycle up on an MTB, so yes they climb better.

cooldad

As the OP was talking about fire roads, I could beat a MTB on my road bike. CX bike would be just as easy.
I agree with DK. Racing snakes.