So, rider + loaded touring bike = 110kg (ish)
Same rider + 'nice bike' = 95kg (ish)
110 / 95 = 1.16
So, over the same terrain, a ride of distance x on the heavier bike is equivalent to a ride of distance 1.16x on the lighter bike. Yes?
on a treadmill?
Naturally.
only If you are doing a lot of uphill
only If you are doing a lot of uphill
Unless it has very aero luggage then you should also be gong better on the flats but for different reasons. Only way to tell would be to fit a 250w motor to both and head out.
Same tires and pressures on both bikes? I find that a much bigger factor than weight.
Yes?
No
As above, it will depend massively on terrain and aerodynamics. If it's just a long, steep climb, then aero won't play a significant role so 16% more weight will basically mean 16% more energy expenditure. If it's just flat terrain with a nice smooth surface, then it's basically all aero, so how the load is packaged will be the main factor. It's possible that the loaded bike would be more aerodynamic if it was done properly, so it might use less energy.
Extra weight only affects the acceleration or climbing. On the road, at speed aero is 95+ % of any effort required.
Trimix appears to have some understanding of the factors here. Listen to him.
As per the rest, including the OP, no,no no
It’s possible that the loaded bike would be more aerodynamic if it was done properly, so it might use less energy.
Unless the touring bike is some sort of faired recumbent, there's no way it's more aero than a normal bike. Even tucking the luggage in behind or infront of the rider will only minimise the added drag as the gaps between the luggage and rider are far too big (at cycling speeds they would need to be of the order of 1-10cm otherwise the turbulent air moves into them) and the luggage is never an aerodynamic shape or has a smooth enough surface.
Depending on the route I find riding with full panniers slows me down a lot more than 16%, probably closer to 33%, and ability to cover distance drops even more because if I could normally ride for say 5 hours struggling up the least few hills, I'll be too tired to get up a hill after 4 on the loaded bike regardless of gearing, having a granny gear just prolongs the agony.
There's a rule of thumb that your daily touring mileage is equal to your normal weekly commuting mileage, so a 10 mile commute should mean your fit enough to do 100 miles in a day on a tour. If comparing commuting on a bare bike to loaded touring I'd say half that is a reasonable target. I
On a compketely flat straight course with a final speed of say 15mph from standing. The difference in distance would be the distance covered to get to 15mph of the heavy bike minus the same for the light bike.
The weight would affect acceleration and deceleration (you have to slow down for longer (further away) to get to a safe speed to go round a bend.
Writing an equation for this would be very complicated. The extra mass alone would affect velocity on any gradient, including downhills. There would also be a variance in tyre rolling resistance, mechanical loses and aerodynamics. A simple multiplication factor would be inaccurate as variables such as total ascent/descent, and prevailing wind will change.
In short so complicated, so why bother just go for a cycle.
So, over the same terrain, a ride of distance x on the heavier bike is equivalent to a ride of distance 1.16x on the lighter bike. Yes?
No.
The effort you expend on the flat is mostly against air resistance. More luggage makes you somewhat less aero, but it's not proprtional to the extra weight.
On a hill, then yes, most of your effort goes into winching your weight up the hill, so your maths is ok there.
On singletrack, most of your effort goes into accelerating the bike out of corners etc, so then, well, it depends.
Ridicule your maths?
Given the original question, your answer seems to have two too many decimal places
There’s a rule of thumb that your daily touring mileage is equal to your normal weekly commuting mileage, so a 10 mile commute should mean your fit enough to do 100 miles in a day on a tour.
Have we decimalised the week?😳
Five 10-mile-each-way trips, so 20 miles a day I guess.
Not sure I agree with the premise, but I think that’s the maths there.
Nowt wrong with your maths at all. You can now set yourself up as a cycling fitness consultant 😉
I think... Generally, it's a bit harder at times... is an accurate answer! 😆
Have a play on bikecalculator. Rolling resistance and CdA for aeroness will matter more than weight.
The extra mass alone would affect velocity on any gradient, including downhills.
Nope. Classic misconception.
The drag is the vastly dominant factor. Mass only becomes important on the climbs or when changing speeds. Heavier will be slower to accelerate and harder to pedal uphill.
Trying to pin it down to a number with an accurate formula is essentially a waste of time - though it might make an interesting project - because of all the other variables like tyre pressure, temperature, terrain etc.
You need to keep as many factors constant between the two bikes for any sort of apples to apples comparison, for instance mounting the same aerodynamic canopy over both bikes and yourself. Given the heatwave, you may suffer. 😉
The extra mass alone will be very against you uphill, but will be a smaller scale advantage downhill.
Aero drag will be a big factor on downhills and the flat above ~15mph, but it will also be a smaller factor uphill until the gradient reaches ~7% (was it last year where we saw TDF riders switch bikes part way around the TT course from a TT bike to a lighter road bike before a steep hill?).
Side panniers are a massive drag compared to a rack top bag, or better still, a rucksack that plays a C&C Music Factory single. 😉
The extra mass alone will be very against you uphill, but will be a smaller scale advantage downhill.
It won't help in any measurable way downhill. You'll get to the bottom without pedaling whether you have a heavy bike or a light bike.
was it last year where we saw TDF riders switch bikes part way around the TT course from a TT bike to a lighter road bike before a steep hill?
A normal person on a touring bike loaded up with gear is not comparable to a TDF rider. Us mere mortals will not be able to climb fast enough to worry about the difference in aero drag between a bike with panniers and without.
was it last year where we saw TDF riders switch bikes part way around the TT course from a TT bike to a lighter road bike before a steep hill?
If it was actual science and not a gimmick to sell bikes, the reasoning was that a TT bike is not the best bike to pedal, but the aero gain outweighs that disadvantage when your speeds are in the 30s. climbing at slower speeds and descending hills (and general handling) then the road bike is king.
but basically - tour of holland: start cutting out some fairings from milk bottles; alpine tour: head over to bike****ngweightweenieworld
You need a powerpod. That’s works out power by a series of algorithms instead of strain gauges. I think it can do drag stuff too.?.
Focusing only on weight up hill-
mass * gravity (9.8) * height (ascent in metres)
So carrying an extra 10kg up 1000m in an hour is ~10*10*1000/(60*60) = 28 watts, I.e. ~10% of a normal rider power output on a prolonged climb.
This ignores drag and extra rolling resistance due to tyre deformation etc
For your example of 15kg it would be ~41w extra assuming you climb 1000m in an hour. If that takes 250w (for sale of argument) unladen the extra power required for luggage would be surprisingly close to 16% you originally calculated, ignoring drag. In practice the drag of panniers would have an affect even at climbing speed.