MTB speed vs Road bike speed

I'm sure this kind of question has been asked before, but I haven't seen any answers that satisfy this particular one.
If the same rider cycled 40 miles on a very light (~ 17lb) front-suspension carbon mountain bike with mountain bike tyres pumped up high (~60psi) and managed that distance in 3 hours...
...then what sort of time could that same rider expect on a good road bike that actually weighed 2lb more.
I believe the difference isn't that great between the two, perhaps the road bike could save 10 minutes.
If the same rider cycled 40 miles on a very light (~ 17lb) front-suspension carbon mountain bike with mountain bike tyres pumped up high (~60psi) and managed that distance in 3 hours...
...then what sort of time could that same rider expect on a good road bike that actually weighed 2lb more.
I believe the difference isn't that great between the two, perhaps the road bike could save 10 minutes.
My commute:


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Would expect the difference to be more than 10mins tbh, mainly because of three things
Much less rolling resistance
More agressive riding position
No loss of power through the front forks having suspension
I know it's a tricky question!
Trax T700 with Lew Racing Pro VT-1 ;-)
I started road cycling a few years ago on my MTB - after a while I was averaging about 1:15 for my 20 mile, mostly flat, commute. I then roadified the bike a bit by putting on slicks, SPDs and a longer (and upside down) stem - that cut my average time to 1:08.
Getting a road bike only improved it by about 3 mins, although there was a new handicap in that I wasn't happy to bunny-hop the 8 kerbs I had to cross on the way.
I've since moved house and my commute is now a bit shorter but much hillier, I can't quite bring myself to summon up the scientific curiosity to try it on my MTB for comparison - but I expect the extra weight on the hills would be crippling, a problem you clearly don't have.
None of that proves a lot. The time differences will be affected by factors like the hilliness of the route and the wind (this affects me more than anything else, my current best and worst times for my commute are 0:56 and 1:45, I reckon at most 5 minutes of the variation can be attributed to fitness). I guess you could try circuits on a track for more controlled comparison, but how sad would you have to be to do that? Plus it wouldn't compare climbing at all.
Your query looks more than hypothetical, can we assume that you have actually tried this? It's also a slightly unfair comparison if the road bike is actually heavier than the MTB - how many people have a combination like that? Perhaps 2 bikes of roughly equal cost might be a more useful test.
A friend managed this in 3 hours. I can manage this in under 2 hours and 20 minutes.
I'm wondering how much is down to the bike, but my road bike is actually heavier than the mountain bike.
Also, the question keeps getting asked round where I work as to what sort of difference a road bike can make to a mountainbike. The more experience I have and the more I hear what other people say, the difference is sometimes only a few minutes per hour.
Trax T700 with Lew Racing Pro VT-1 ;-)
My speed over 50 miles on the road on the only proper road jaunt I've done was around 4-5 miles per hour quicker than my average speed on my MTB which I use to get to work every day (30 mile round trip).
It was a boardman team carbon road bike though, but I'd only done a few weeks training on it before the ride. I reckon a couple of months of practice and getting used to road riding would have seen a much bigger difference.
Could you try swapping bikes for a test run?!
Got a roadbike this week and difference was below as confirmed on my GPS cycle computer:
MTB
Distance 7.29
Time 34:18
Av. Speed 12.75mph
Max Speed 20.53mph
RB
Distance 7.29
Time 27:35
Av. Speed 16.21mph
Max Speed 23.4mph
So about 7mins quicker and did'nt expend anywhere near the effort as on the MTB. I am not much quicker down the hill but can sustain a decent pace everywhere else which is the difference.
I expect when i get used to the bike and can put in the same effort as I did on the MTB I will be even in quicker.
Unless you are climbing the weight of the bike will make censored all difference.
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My collection of Cols
So if I ride my 14lb road bike then repeat the same flat route but with 40lbs of lead poured in the frame(so it doesn't affect its aero profile) it wont make a difference to the time taken?
I suppose Newton could be wrong ...
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Since you quote Newton I assume you understand what you are talking about and hence would know that that is indeed correct if the ride were perfectly flat. The only difference would be in the time to accelerate up to speed. F=ma is I believe the equation you are thinking about.
Now on a more practical level the OP said that the difference in weight was 2lbs not 40lbs so I stand by my statement.
Now stop being a censored and writing stupid responses.
Pace RC200 FG Conversion (FCN 5)
Giant Trance X
My collection of Cols
(f"(t)) dμ(t) = −" (t) dμ(t)+ (b2 + 2a2)f2" (t) dμ(t) + 2ab2f"(t) dμ(t) + a2b2 − a4.
Road bike
I expect some of that is improved fitness but mostly it's the bike. Especially as I had the rest on the hybrid.
2004 Marin Muirwoods Hybrid
Route 1: 13.0 miles, 100m climb, 100m descent
MTB: 49:02, av spd 15.9mph, max spd 28.9mph
Road: 43:59, av spd 17.8mph, max spd 34.5mph
Route 2: 15.5miles, 152m climb, 152m descent
MTB: 57:37, av spd 16.1mph, max spd 28.1mph
Road: 50.52, av spd 18.3mph, max spd 31.5mph
All times/distances measured with a garmin GPS, and the heights are from the DEM linked to in Sportracks rather than the dodgy GPS heights.
Now I'm more confident on the road bike (probably equal to how I felt on the MTB when I did the times shown above), I'm probably 5 mins quicker on each route. In fact I'll try one of them tomorrow to find out and post up the results if you're interested.
I would also add that as others have mentioned above the amount of effort to get these times on a road bike is also a lot less. I've since done a 60 mile ride in 3:30 (with a couple of 5 min stops included) and there's no way that I could have done that sort of distance on my MTB let alone in that sort of time. In fact I'm not sure I'd want to do 60miles on the MTB!
I have no idea if these times/speeds are fast or not (I get out once a week at most), but hopefully it give you an idea of the sort of different between an MTB and a road bike. It's definitely noticable.
Trax T700 with Lew Racing Pro VT-1 ;-)
Good to see someone with a sense of humour. Well and truly spat your dummy out and simultaneously threw the toys out of the pram.
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I'd be disappointed to knock out 40 on the road bike in more than 2h 20, mebbe 2h 30 if not going bonkers, so about 17.5 mph. So 30 minutes quicker. Easy. And a damn sight easier too, as already stated.
Now after a year of road cycling (after the 10year gap) i can manage about 20-23mph ave but over a longer distance. same route!
www.ogmorevalleywheelers.co.uk
10TT 24:36 25TT: 57:59 50TT: 2:08:11, 100TT: 4:30:05 12hr 204.... unfinished business
Route 1: 13.0 miles, 100m climb, 100m descent
MTB: 49:02, av spd 15.9mph, max spd 28.9mph
Road: 43:59, av spd 17.8mph, max spd 34.5mph (orignal)
Road: 41.29, av spd 18.8mph, max spd 35.0mph (updated)
Latest time added as promised. This represents a more accurate comparison (for me) of the difference between an MTB and a road bike (i.e. just under 20% faster). Sorry for the delay, the previous two trips when I tried to do this route I ended up getting punctures! I only manage to get out once a week so it's taken a few weeks to finally getting a clear run done.
Hope it helps
Rich
I found myself at the end of the commute grunting some days on the MTB on anything other than FLAT roads (ok I'd been off fitness training for a while which didnt help) but it got a bit daft how jelly-like my legs were upon getting to work.
Anyway, the roadie is just such a breeze to flirt along on, at least 1/4 to 1/3 quicker but at least half the effort.
Loving every minute of it (Spesh Allez 16 2010 BTW...)