Discussion in 'The Roadie Hangout' started by taprackbang, Jun 15, 2014.
No, taprackbang = taprackbang :wave:
Something like that is kind of my plan if I ever decide to pick up something more road oriented. A CX frame closer to road geometry would work great for my light duty trail riding and should be better for the road. With many models now coming with disc brakes, it would also be nice to find one with 135mm rear axle spacing and enough clearance for slightly wider tire/rims to be able to swap my PowerTap-equipped wheel between the MTB and a CX bike.
As I said, I did put road tires on my MTB and do quite a bit of riding. I ride with a power meter on both my road bike and MTB. I have a quarq on my road bike and powertap on my MTB.
Here is data from a local climb that I did on mt MTB with road tires....
Time - 12:20
VAM - 785.7 m/hr
Power - 211 watts
Here is data from a slightly slower time:
Time - 12:46
VAM - 759.0 m/hr
Power - 200 watts
Here is data from a slightly faster time:
Time - 12:00
VAM - 807.5 m/hr
Power - 205 watts
I don't know what the weather was like (wind direction) on each trial, but the power numbers tend to be relatively consistant between the MTB and road bike. the MTB power does seem slightly higher as there are other faster times on my road bike closer to 200 watts. The MTB I was on weighed about 23 pounds at the time and was a hardtail compared to my road bike that weighed 16.5 pounds.
This is why people end up owning multiple bikes. :lol:
We've all experimented looking for that "jack of all trades" bike only to discover that it does everything mediocre.
Is 12 minutes even a fair amount of time to see a difference? I have done a 20 mile section of SART on an MTB with and average of 17.5 MPH but on a road bike 19.8. I'm almost sure I could have kept the pace for 12 minutes but it's after a more significant amount of time that the MTB pace would fade. I have seen several MTB's keep up with us for short amounts of time. I's after a longer period that hey fade. IMO 12 minutes is not long enough to make a fair comparison.
As far as climbs, I have done the GMR climb (8 miles/2300ft) in 56 minutes on a roadie. If I had tried it on an mtb, I don't think I would even be close to my roadie time. But I think I could keep the pace for a few minutes at the start but not for an hour.
I believe a rider on an MTB can keep up with road bikes but all things equal, not the same.
It's not so much the time as the power. Regardless of how long the effort was, the power on both is not that far off. It would have been different if the power on the MTB was 250 watts to do a similar time on the road bike, which only had a power of 200 watts.
If you want a longer comparison, I can compare a 42 mile ride from MTB to road. The MTB avg was 16.2 mph and the road avg was 17.5 mph. Sounds like the MTB is a lot slower until you see the power. Average power on the MTB ride was 177 watts. and average on the road bike was 206 watts. Had a ridden at the same intensity on the MTB, my average speed would have been faster, but I can't quantify by how much.
Another comparison would be a road I have used to do power tests on. Slight uphill, no stops, very steady grade.
MTB - 270 watts for 31:06 at 17.5mph
Road - 281 watts for 29:03 at 18.7mph
Again, no idea on wind speed/direction for those. MTB looks to be a little slower than the road bike.
The MTB will be slower, but only due to aerodynamics (more of a factor the faster you go) and weight (only really a hindrance when climbing). How much slower depends on your riding position and the weight of your bike.
I don't know how a power tap works but on Strava, the power reading goes by weight and speed. Is it different for a power meter? If it is the same, could it be that the power reading is lower because you were going at a slower speed per given weight giving a lower output? Again, I don't know how a powertap reads power output.
I guess it depends on what one considers a "little slower". Trying to make up 1 MPH on an average is pretty darn hard to do, you have 1.2 there within 30 minutes. I know on Strava I have ridden segments with other riders that were far behind but when all is said and done, and posted on Strava, they were only .4 under my average. So 1.2 IMO is pretty tough.
Going back to the OP, I think he is asking about MTB keeping up with a roadbike ride all things equal. Usually a road bike ride 2+ hours. But again, that is all based on individual riders. Our rides are 2.5 hours so doing the same ride for me, "my" mtb would be far behind by the end of a 2.5 hour ride equaling "much slower". If the OP is doing a 30 minute ride, then not so far behind.
Looking at my Strava time.
7 mile segment
A rider that is 1.2 average behind
7 mile segment
The difference in a 7 mile segment is 1:12 for the 7 miles.
Multiply that by 6 (since we ride 42 miles)
and the difference for the effort would be 7:12 for the entire ride.
Now if you lose 7 minutes and 12 seconds every 42 miles of the TDF or any other race, that would be considered considerably slower. So to say the MTB is only a little slower, all depends on one's own opinion.
With the watts thing, I am listed at 239 watts while some guy 13 minutes behind me is listed at 245 watts. Seems that he would have a faster time according to the watts calculation if it was accurate. Again, I don't know how they measure the watts thing.
I guess in order to answer the OP's question properly, we would need to know what he means by keeping up with road bikes and for how long?
The PowerTap and other power meters directly measure the torque being applied through the pedals and are the most accurate and consistent way to measure and compare power. The Strava estimated numbers are just that: calculations based on known factors (GPS time-over-distance/elevation, rider and bike weight input, bike type (road or mountain), and I can't recall if they apply an adjustment factor for those who also run a heart rate monitor or cadence sensor).
After buying a PowerTap meter and getting a couple months data on rides and segments that I have ridden often and had amassed quite a bit of Strava calculated power estimates, I can say for certain the Strava numbers are way off for my road rides on the MTB. Riding a mountain bike over the road has Strava showing power as significantly higher than actual power measurement in watts from the power meter.
I can't say why that's the case since they don't publish the equation/formula/exact data they use to calculate estimated power, but perhaps I'm more efficient than they assume most people would be on a mountain bike over the road due to less rolling resistance from aired up tires and aerodynamic factors. While the Strava generated power numbers were off compared to power meter numbers they do seem pretty consistent and while they could be used for training purposes you'd be better off sticking to time over a segment/course to gauge improvements.
In simple terms, think of Strava calculated power numbers more as an amusement item and take the number with a grain of salt. Also keep in mind that while your estimated power for your type of riding could be close to power measure by a power meter, especially for road riders on road bikes, the estimated numbers are still best used for comparing against yourself and shouldn't be used to measure your power and effort against other riders.
If you're looking through leaderboards you'll see a lightning symbol next to some power numbers which indicates the rider was using a real power meter and in that case you can compare overall power numbers between two users running power meters but the site doesn't make it easy to see what type of weight, kg/watts, bike types, environmental factors, etc. of the other rider. Two riders might be putting out the same power but if one weighs a lot less and is going uphill they could be a little to a lot faster over time.
As already mentioned, if you're comparing someone's power meter numbers on a MTB to power meter numbers on a road bike, hills probably aren't the best comparison. If the bikes weigh close and rolling resistance isn't dramatically off between the two bikes, the slower pace means there isn't as much aerodynamic drag and the rider can likely get used to the gearing differences. What really starts separating the two bike types is over flat terrain and downhill where you can push higher speeds on both bikes. The faster you go the exponentially higher aerodynamic drag that will require greater power to overcome the faster you try to push.
And definitely small differences in speed can add up over time/distance.
Ah thanks for the explanation!
I've always figured some of the strava numbers to be for entertainment.
I have a road bike and a 29er HT. IMO...the main thing (besides the gearing and tires) is the body position. On my MTB I'm using 710mm bars with a short stem. I'm really upright...on my road bike...I got a 380mm drop bar and a 110mm stem. That allows me to get much lower on the road bike. Maybe if you were able to put a drop bar onto the MTB...that will narrow your body and get you lower on the bike. The aerodynamics of the bike don't really go into effect unless you're above 20mph. The main drag is your body. If you can lower the wind resistance of your body...and have the proper gearing along with road tires...you may have a chance.
So riding Mt Wilson Sunday and ending up at Chantry allowed me to ride my Pivot Mach 5 down the same road that I climbed and went down on my road bike. My road bike is a Cervelo S2 with ZIPP 404 tubular wheels.
On my Cervelo I made it down in 6:09 at 29mph. On the Pivot it took 9:39 at 18.8. I know my Pivot is not a 29er...but it was still interesting to see the difference. Its not often that I ride the same road with my road and MTB.
had a guy finish the cat 5 crit race in ontario in front of me few years backon a 26"
Did a road ride last Sunday and there was a guy on a Niner gravel bike with 40s running 50 psi. This guy will annihilate me on flats and climbs on the MTB. However it was all he could do to keep me in sight on the road bike.
Not too surprising. It takes me a heck of a lot of effort to move quickly for short bursts over flat ground and short hills or to maintain higher speeds over the flats on the mountain bike. For short sprints of say .2-.3 up to around half a mile and usually between thirty seconds to a little over a minute, comparing data for segment times of riders on road bikes with power meters, they might be putting down 200-300 watts while to be competitive I need to hold 500-800 watts.
Fit, bigger road bike riders might be able to hold their range of power for long periods but I can't hold much over 500 watts for more than a minute or two (a reminder again that I'm a big framed guy that's slightly festively plump). Reverse-calculating weight from their W/kg I've probably got a hundred pounds on some of them but the watts-to-kg numbers tells a familiar story.
It takes quite a bit of energy to accelerate the heavier wheels and weight of the MTB and if you are able to get up to speeds in the lower to mid-20 mph range the aero drag kicks in hard. For general cruising speeds, if you ride with a roadie that can hold 18-20 mph or more solo pace over flat or rolling terrain for long distances it isn't going to be fun trying to keep up. The faster they are and the longer you ride the more distance they'll start putting between you and them.
I think probably everyone can agree with the proper tool for the job being best but it is interesting to look at differences in bikes and techniques and maybe extrapolate some data that may help you get faster on easy, smooth flat and downhill areas in the dirt. Warning: another long post...
In the last couple months I've done two different rides of the same route/course under similar conditions that have a 5+ mile section of downhill at a fairly consistent -3 to -4% grade. Looking at the data logs of equivalently quick road riders that are likely in their best aero positions, it looks like they're spending a lot of time at zero cadence and short, not too heavy bursts of power in their big rings. On each ride I tried different techniques to see what would be most effective on the MTB and what it would take to match their times.
First ride I tried to keep somewhat low on the bike but was pedaling a constant high cadence in 42-11 gears the entire way down. Sometimes on areas with steeper downhill grades spinning out of gearing otherwise it was a fairly steady power output. Second time I tried to mimic what it looks like the road riders are doing by really, really tucking in as far as I could for aero on the mountain bike and use a narrow grip. I'd then watch the cyclocomputer and tried to keep a 50 km/h pace (~31 mph). When I'd slow down to around 48 I'd apply a burst of power to get me up to around 53-54 and coast back down while tucked in.
The results were somewhat surprising. The overall speed and times ended up being extremely close but more surprising the average power expended was also the same at around 250-260 watts. The high cadence, continual pedaling was fairly sustainable but I was fighting more aero drag. Trying to get super tucked in was really killing my wrists and back and I ended up looking forward to coming up off the bars a little during the short bursts of acceleration. Those bursts also required big spikes in power output.
Either method still required putting down a lot of power, just a little differently in how it was applied (steady versus surges). This was pushing pretty hard just to go as fast as some road cyclists running power meters showing they only needed to put down 75-150 watts average over the segment.
With road downhill, my weight disadvantage on hillclimbs disappears and works with gravity but aerodynamic drag is still a really big factor when you're going fast, even if you minimize it as much as possible on the MTB. If you try to get super aero on flat bars it's really uncomfortable. On the other hand you can only push so high of a cadence before running out of gears and when speed slows down slightly you'll be pushing sustained high rpms at higher power levels (and in my case heavier pedals and shoes also sapping power).
My perception on each ride was that my physique and cardio system seemed to like the bursts of power as it let me recover enough to push harder and carry more speed over a few hundred meter section that leveled out to a slight incline about mid-way through but I was also spent near the bottom and couldn't do a max power sprint like I did on the steady pedaling/pace ride.
I pulled up next to a guy on a Niner with skinny tires this morning and he was flying. I was on my road bike and I commented that he was moving, at that point he said something about not seeing anything yet and he rides 50 miles a day. That was the last I heard from him when he dropped my so fast that it took a second to comprehend what happened. A strong rider is a strong rider.
on climbs and under 18mph conditions there won't be a huge difference between a good MTB and a descent road bike. BUT once speed hit 20mph and more the difference is dramatic! With same fitness I gained almost 2mph on the flats with same level of effort with just wheels change. Higher the speed larger the level effort difference. MTB is not designed to be aero so at higher speed it is really hard to keep up.
We all had stronger rider passing us on all kinds of different bikes but we are not talking that. We are only talking about the difference between 2 types of bikes, pure mechanics.
Here's a comparison...like for like, road bike vs. mountain bike, over a longer distance:
2014: Breathless Agony Attempt on Trek Superfly FS 100 Full Suspension with 1x11 (32x10-42) and Ikon 2.2 Tubeless (23 lb bike with 24 oz water bottle and 100oz loaded Camelback with food and gear)...total rider+bike+gear weight=200 lbs
2012: Breathless Agony on Trek Madone 5.9 w/ Dura-Ace wheelset (53/39 x 12-27 ratio)-18lbs with (2) 21 oz. water bottles...total rider+bike+gear weight = 185lbs
Start to Time Check #1: 25.5 Miles and 2300 ft of climbing.
2014: 1:35:42 Average HR 137 and 15.9 mph average
2012: 1:32:24 Average HR 124 and 15.7 mph average (includes 5 minute break to change flat)
Time Check #1 to #2: 18.5 Miles and 2300 ft of climbing
2014: 1:26:30 Average HR 135 and 12.7 mph average
2012: 1:12:09 Average HR 131 and 15.4 mph average
Time Check #2 to #3: 11.1 Miles and 3000 ft of climbing
2014: 1:33:43 Average HR 141 and 7.1 mph average (temp was in the 90's though)
2012: 1:08:52 Average HR 143 and 9.7 mph average
After that, there is no comparison...because I didn't finish the climb on the MTB in 2014 and descended SART, which I didn't do on the road bike in 2012. If you're going around 12-15 mph, it takes just a little more effort on the MTB than the road bike, but only a few percentage points. The gap widens at the high speed due to gearing and rolling resistance and at low speed due to weight. I consider Ikons virtual slicks on the road. Throw on some 2.4 DH-style and you'll really get a workout.
Side note: My descent down Oak Glen to Yucapia was the same time for both, but I was able to maintain a higher low speed on the MTB because of traction...just couldn't get the high speed on the road bike due to gearing and rolling resistance.
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