Cyclist0108

I have a mountain bike and a (few) road bike(s). My most recent one is a gravel bike really, but has been my main ride since I got it a couple of years ago, both on paved roads and also some challenging fire-roads and trails. I've been riding those same trails for the last couple of days on my mountain bike, and my legs are in pain (like enough to keep me awake at night). I won't say riding these trails and fire-roads on the road/gravel bike is effortless, but I don't feel muscle fatigue, let alone pain.

WTF?

The road bike is a custom steel bike frame and has compact gearing.

The mountain bike is a 9 year old Trek Fuel EX 8 aluminum full squishy (with lockout) and there is nothing obviously wrong with it. I rehabbed from an ankle break on this thing 3 years ago and don't recall it being this hard, even with atrophied leg muscles...

up on two

I ride mostly Mtb but mix in a little road rides to break it up a bit. I will say that a strong Mtber will be strong at road rides too but not so much the other way around. Not because of fitness, but Mtb riding takes so many other skills that do not apply to road rides.

Also, the two styles are different to the body as well. Mtb rides are more HIIT type of riding, short duration's where road rides are constant mid level output, long duration. When I compare wattage output, road rides are always higher but I usually feel less tired from a road ride (compared to Mtb rides).

So, what do you do? Ride more Mtb if that is what you want to get faster at, or enjoy the road rides and pay no mind to anything but having fun. FYI, I like riding road bikes but still can not feel comfortable around those cars!

kingston 

@wgscott, So you're saying the the exact same trails are harder on a mountain bike than a gravel bike?

up on two

I would think besides moving the additional weight of a mtb, there is also the pedaling efficiency loss due to rear suspension compression, therefore requiring more effort to go the same speed. On a fire road, that would results in a significant extra effort.

exmechanic89

I trade back and forth between both types of bikes without any issue, personally. Not sure why there would be a problem.

Scarbo

I agree. MTB riding takes a lot of specific skills, balance, and agility that road riders don't usually hone as finely. Switching back and forth between the two types of riding all I notice is that MTB riding will affect my muscles differently (MTB: activates the glutes more).

Cyclist0108

Exactly.

If I was getting thrashed by technical single track, it wouldn't worry me. (In fact, the gravel riding seems to have improved my under-developed single track skills to some degree.) But this is just generic climbing (even noticed it on paved roads), which makes me wonder if my leg muscles have become locked into a very narrow range of motion or something.

It might be something as basic as bike fit. The road bike is custom (should be close to perfect fit), and the mountain bike is just something approximately the right size, off the shelf.

Cyclist0108

It does lock out. It still squishes a wee bit, but then so does my Brooks saddle on the road/gravel bike (not to mention what sits upon it).

kingston 

sounds like you must be using different muscles. Fit could explain that. For/aft position of the saddle, crank arm length, pedals. Could be a lot of things. I'm sure if you rode the MTB more often you would get used to it.

Cyclist0108

I just discussed this with my wife and said it was prima facia evidence that I clearly needed a new custom-fit mountain bike, but she pointed out how much more expensive a divorce would be. (Getting busted for the new wheel-set a few days ago didn't help.)

joejack951

Have you eliminated simple causes like saddle height and setback?

Cyclist0108

No. (I did adjust it a few times.)

Maelochs

Geometry, weight, gearing ....

MTB does use different muscles and demands a different type of riding ... on trails. One a fire road where you normally ride a gravel bike, I'd say the differences are geometry, weight, and gearing .... different riding position, heavier bike, and possibly lower-ranged and wider-ranged gearing where you might not be as efficient. You might be spinning faster and pushing harder, trying to achieve the same speed you'd have with the gravel bike.

Peter Sagan doesn't seem to think that switching between the two is that hard.

exmechanic89

Unless the bike is a bad fit, 'off the shelf' vs custom fit isnt gonna make nearly the difference some people imagine it does. There's no reason you shouldnt be a decent rider on either syle of bike, off the shelf or not. I've noticed in these forums many times that people (not saying this is you, OP) blame their lack of ability on having a bike that's too heavy or not new enough, when in reality those two things have little to do with a rider's skill/strength. So don't place too much emphasis on the bike itself.

Maelochs

Except in a case like this where the only difference between the two experiences was the bike, and therefore the bike obviously was the Entire difference.

WHY the bike made such a difference can be explored, but the whole premise here is that riding two bikes gave two very different experiences.

By the way, the specific post yo quoted was entirely a joke ... you got that, I know.

exmechanic89

Post #7 did mention custom vs off the shelf fit. Or was that a joke?

Cyclist0108

Sorry. It was supposed to be an attempt at humor.

Cyclist0108

I actually do have a custom-frame road/gravel bike, but the context was just to say the fit is optimized. (I have quite short legs for my height, so in my case this actually does help a bit, at least with stability and comfort.) I wasn't serious about needing a custom mountain bike, but I do think maybe I should pay more attention to its fit.

ThermionicScott 

The switching back and forth is why it isn't a problem. The OP has probably let his off-road skills atrophy by riding road exclusively for too long.

Cyclist0108

Kind of like your reading comprehension skills?

ThermionicScott 

I guess I took your title too literally? Sounds like a fit issue now that I've re-read everything. Sometimes you get used to a badly-fit bike, and it takes riding a different bike for you to realize it.

Cyclist0108

What surprises me is I managed for so long on this when my leg muscles were atrophied (from being on crutches for 4 months). It sort of got me wondering whether I re-built my leg muscle strength very directionally (or anisotropically) since road/gravel biking on this thing has been my most significant source of exercise in the last couple of years.

In any case, I think I should try to optimize fit and ride the mountain bike more (or give up on it and try to develop my off-road roadbike skills).

gilpi

Could it be that the mountain bike has wider, less pressure heavier tires that makes it less efficient on gravel than the gravel bike?
I own a rigid mtb that I use on gravel and I'm wondering if cx tires would make a difference?

kingston 

I can understand why people like full suspension, but I have never found a need for it personally. For the type of off road riding I do full suspension would be massive overkill. Sounds like your situation is similar.

WalksOn2Wheels

I would also recommend looking at the fit. Unless I just hammer really hard during a ride, my legs have never hurt the day after. But in one case, I had adjusted my saddle just a bit and it absolutely destroyed my quads in one ride. Just go to the bike with the good fit and measure saddle height and fore/aft in relation to the BB. Duplicate it on the MTB and try that. The full suspension will shift the geometry a little bit, but it's a good starting point.