how much faster on a road bike?

[highlandsflyer]

Re: Re:

The difference in average speed over same course is less than youd think, about 3 to 5 mph.

I don't think it is so simple. The type of 'course' is a major factor.

Generally I would reckon on at least 40% faster over a short distance on ideal tarmac.

Pushing, a fettled racing bike can be over twice as fast with similar effort.

 

[02gf74]

Re:

I meant on tarmac.

 

[integerspin]

i took a garmin on a ~50 mile ride, I stayed on the road.
And took exactly the same route.

Mountain bike with 2.1" velociraptors 12.6mph av
--------"----------------- 1.5" city jets 13.6mph av

I was quite disappointed, I was hoping for a few miles a hour increase, I was
intending on riding to Southend, and probably back, and was hoping the skinny
smooth tyres would it easy.

 

[jimo746]

Re:

Really depends on fitness.
Tyres do make a difference too.
But riding position is a biggy too, once you pick up speed the more aero position on a road bike cuts through the air far better than the sit up position on a MTB.


On a Mtb with slick tyres on I used to give a few roadies a run for their money away from the traffic lights, once we got up to speed though they soon flew past & I ran out of gears :cry:

 

[Thias]

I learned that rolling resistance is 80% tyre pressure. Nobbly or slik makes close to no difference.
Agility on the other side is all about wheel weight.
Road bike have it both. Light wheels and high pressure.

 

[02gf74]

Mountain bike with 2.1" velociraptors 12.6mph av
--------"----------------- 1.5" city jets 13.6mph

Interesting, didnt expect the difference to be massive, but more than 1 mph.

 

[cce]

Re:

City jets aren't very fast.

 

[bikey :)]

Mountain bike with 2.1" velociraptors 12.6mph av
--------"----------------- 1.5" city jets 13.6mph

Interesting, didnt expect the difference to be massive, but more than 1 mph.

Perhaps wind resistance comes into play, more so than with a road bike, negating the speed advantage of the slick over the knobbly on an mtb.

 

[mattr]

I learned that rolling resistance is 80% tyre pressure. Nobbly or slik makes close to no difference.

try something like a high roller. Then a rocket Ron. Both at 2 bar.

There is a massive difference. 3 or 4 kph on my local non-technical circuit.

Whoever named the high roller needs shooting. They don't roll at all.

 

[Mike Muz]

Re:

Hmmmm, let's think about this one.

The combination of resistance with knobblies average 2.1" - if used - with at most 60psi in them.

Or 1.5" slicks. What pressures do they run at?

Against smooth road tyres, average 23mm wide, with up to 175 psi in them.

As well as drag/resistance as a result of the tyre/road contact, there must be a big difference in aerodynamics of the wheels alone. Without taking into consideration riding position. How many mtbs have bars that are - at most - 460mm wide. Effectively splaying the riders arms out to catch more wind. Also, conventional mtb gearing is spread wider for off-road use, so pedalling speed is compromised, and sometimes you can also run out of gears on an mtb. Not helpful!

Wow! :shock: I almost sounded intelligent then!

Wait for it!

Mike