Trevtassie

I've used the SON, SP and Shimano dynamo hubs, there is no discernible difference, other than that I think the SP has a *slightly* higher output when used with a Forumslader. Rolling friction meh, there's more difference from the extra wind resistance of wearing a baggy shirt! I'd ditch that massive front rack for something like a tubus duo though. Having a lot of weigh on top of a rack like that sucks on tour, you get handle bar flop every time you stop big time, even with a stabiliser.

djb

thanks for sharing your experience and views on the differences of the various brands of dyno hubs.
I've never used higher up stuff from racks, but can relate to how it would clearly have more flop, but if doing off road stuff where it's better to have stuff higher, it's a compromise, and keeping weight down must help to an extent.

djb

Hey ilchymis, that's a pretty neat looking seatpost, with what looks like a lot of setback.
is that stock or a special one you put on?

fishboat

Also..thx for posting this..very interestng read.

A friend I ride with has often wondered why I roll past him so easily while we both coast on downhills...even when I'm riding my drop bar conversion mountain bike with 2.15 inch tires and he's on his road bike. I typically have to pull out around him (not drafting) and roll by him. I have 100 pounds(stocky above the waist..size 46) on him (though weight doesn't matter) and should have a wind resistance disadvantage..though not enough to keep me from rolling by.

He buys cheap tires..I pay more attention to tires that roll easily. He's now buying the tires I run..

mstateglfr 

quality tires matters, but im pretty sure 100# matters too when coasting downhill. thats gonna for sure pull you down faster.

fishboat

That's what most folks would think..but..

https://www.physicsclassroom.com/mme...tlaws/efar.cfm

https://www.physicsclassroom.com/mme...tlaws/efff.cfm

I doubt there's enough difference in our mass & surface area such that he's reached terminal velocity & I haven't..geez..at least I hope so..

robow

"Roll us both down a mountain and I'm sure the fat man would win"

djb

I dunno, always being the lightweight all my life, skiing I always was teh slowest ,
buuuut I totally agree with the tire rolldown test thing. I have a friend who outweighs me by at least 75lbs and I roll past him on my touring bike, 26in x 50mm, fenders, two racks. Its always interesting to see this on reasonable downhills without a lot of speed, lets say maybe up to 35-40kph (so not taking into big account wind resistance, which I know with my bike is pretty significant above 50, 60kph with the fenders all floppy and racks and crap)
Oh, and I do know that he uses super stiff Conti Touring Plus tires, that have a stupid stiff sidewall, so with 32mm and 75lbs more than me, I roll down faster usually with my 50mm slicks.
Now I am aware that I grease my own bearings, so they are adjusted well, where his might be overly tight as they are stock cheap wheels and he doesnt believe in maintenance--so this very well could be a factor too.

LeeG

Ilchymis, your bike will go faster with more horsepower. Period. You will perceive more ease in rolling with an unloaded bike with different tires but you will not go faster especially when you put on a touring load. It’s the hp you apply to the bike that moves you and the hp/weight ratio that determines your climbing speed. At easy touring efforts the differences in mph will be made by differences in effort.

So here’s my recomendation for going 12 mph instead of 10mph. Take off the racks and fenders and weigh them. Change to lighter “faster” tires and calculate the weight difference. Add up the weight of the fenders, racks and tire weight differences and that is your touring load via bike packing including bags. But that doesn’t change the hp. So....

Make sure you’re seat height is correct then move your handlebars lower ensuring your seat to bar distance is comfortable and move your seat forward a bit. Then learn to put out a smidge more hp comfortably. If you plan on putting small rear panniers with 25 lbs of gear on the rear rack the tires really won’t make a significant difference You may perceive a difference but I seriously doubt that over a 50 mile ride there will be more than a fraction of a per cent difference.

More power equals more speed. Same power and more weight is less speed.

JaccoW

mstateglfr 

Im going back decades for this- but I learned about free fall in a vacuum, free fall with air resistance, and roll down(ramp) acceleration- I swear a heavier/denser object rolls down a ramp faster due to weight. Take a hollow cylinder and the same size cylinder that is solid- the solid cylinder rolls down the ramp faster. Moment of Inertia is higher?...I am clearly struggling to remember what I learned decades ago.

Anyways, I am 6'5 215# and roll down hills faster than most everyone I ride with, even those who are riding nice bikes with good tires and are smaller therefore take up less wind resistance. I roll down faster with my road tires, gravel tires, touring tires, etc. I know this for sure because for years I have ridden some of the same hills with all those bikes and some of the same people. Ill have to do some googling around to remember the difference between freefall and ramp acceleration, or whatever it is that is being experienced.

Tourist in MSN

Agree.

A friend of mine would easily roll past me coasting on downhills, he weighed 40 to 60 pounds more than me, he would be sitting upright because leaning forward on the drops was quite uncomfortable for him. I would have to get way down low into a fairly aero position to even get close to his speed. As far as aerodynamics go, we were pretty close to equal frontal surface area, he maybe 5 percent more if we both had the same posture.

F = ma or mass times acceleration equals force. In this case, acceleration is the acceleration of gravity. Mass, the heavier rider has more mass. In a vacuum, both riders would get to the bottom of the hill at the same time (assuming no wheel or tire resistance or wheel inertia). But we do not live in a vaccum. A rider with bike that weighs 50 percent more is likely to have a lot less than 50 percent more aerodynamic drag.

fishboat

Agree.. I stand corrected. My physics was just 40 years ago.."it depends" & details..win the day. There's just one set of facts in this world.

https://www.velonews.com/gear/techni...ting-downhill/

At least my buddy runs closer to me on a downhill with better tires..

djb

which even makes more of a point for better rolling tires when you take my anecdote into account, me the light guy at 135 pulling away gradually from the 200lb guy.

Tourist in MSN

Yup. I have always felt that better rolling tires were the key, much more important than trimming a few pounds. You have seen lots of photos of my bikes, I don't travel ultra light. But I also put a lot of value in drop bars and using the drops when pushing into a headwind.

djb

I do have to say that up until X years ago, I never really considered tires to be that different, it was only when I started trying out different tires and taking the time to notice stuff when doing a lot of the same route commuting (tire pressures etc also)

before that., a tire was a tire and I'd buy a good tire (flat resistant wise) and then just use it, often pumping to max pressures....so yes, I was less nerdy back then.

Happy Feet

On my converted mtb tour bike I used Schwalbe Marathons, which I had no complaints about for puncture protection and wear (still have them).
I read about Panaracer Paselas and decided to try the same size 26x1.75. They were far more supple and light.
The rolling resistance between the two was remarkable. I could really tell the difference most notably when coasting.
However, something about the tread pattern loved to pick up and hold radial tire wire and small flint chips and then flat.. a lot.
Finally I gave up and sold them on with another bike.
It made me sad as I like them so much in other regards.

Tourist in MSN

I worked in a bike shop before i went to college. One of the other mechanics further down the bench rode a high end (at that time) bike with tubular tires. We had lots of discussions about pros and cons about almost everything on a bike.

There were a lot of topics that us mechanics would never agree on, but tires was one that we did. But at that time, there was terrible choice when it came to tires that we could afford. So, a few of us used what we thought were the best tires, I could not afford them.

There was some agreement on rear derailleurs, most of us preferred Suntour. (None of us used that crappy Shimano stuff.) A small number of us (including me) liked Suntour front derailleurs, but most of the mechanics used a Huret Luxe front derailleur. One or two had Campy.

I think no other mechanics rode tubulars that I can remember, but a few years later I bought a used bike with tubular tires and was amazed how much faster they were.

djb

Tmsn, when I started touring, I soon switched from 32 with tread to some 28s with kevlar flat protection, a bit expensive for me at the time, but they rode well enough and were certainly faster than the 32s that came on my bike at the time. They may have been IRC somethings, early 90s, and as I had great luck with no flats with them, I kept on buying them. Not having a ton of extra cash, I basically just bought tires and then used them until they started getting the odd flat, and they got new ones, or before a long trip, but really, I just used what I had and they worked fine enough.
I certainly dont remember being aware of "faster" tires, and put the good flat protection of those specific ones up there on the priority list. I did have a friend who rode tubulars, but I always figured he was a bit nuts , as it seemed pretty complicated to me, especially for touring.
So I do get the aspect of not having lots of money to try x, y or zed tires, and how a tough tire will last a long time and not get flats, which is a pretty realistic priority for most people, especially if biking is just something you do once in a while.

mrv 

I think question 1 was answered already:
Force to move the bike forward = mass X acceleration - drag
Drag = (air density) X (coeff drag) X (frontal area) X (velocity ^2) / 2
So the heavier rider's mass tends to have more of a downhill benefit than his/her increased frontal area, so us 200lb riders downhill faster than the 150lb climbers. (i also tended to time trial a little better than the climbers....)

Question 2: Moment of inertia for cylinders: summary: if a disk and a hollow cylinder have the same mass and diameter, the moment of inertia is HIGHER for the cylinder, so the cylinder resits rotational changes in speed.
So a solid disk has the mass evenly distributed. Low moment of inertia.
A hollow cylinder that has the same mass has all the mass on the outside of what is now a ring.
At the top of a slope, the hollow cylinder is going to resist rotation, so it is slow to start.
https://en.wikipedia.org/wiki/List_o...nts_of_inertia
Some equations from the wiki page:
(moment about the rotation) = 1/2 X (mass) X [ (outer radius ^2) + (inner radius ^2) ]
-- if a disk, inner radius = 0
-- if a very thin cylinder, it's going to nearly double the moment of inertia - WHICH IS A PROPERTY INDICATING RESISTANCE TO ROTATIONAL CHANGE (so, yes, if you're going fast, a heavier tire keeps you going faster, on paper)
Fun video

To the OP: So what?!? you ask.
1. eat more ice cream like Greg LeMond did to giver yourself that "pear shaped" / tear drop effect so you can try to reduce your frontal area
2. Get some lighter tires like other people said. Maybe go tubeless if want to deal with all that ...... stuff - so you reduce the mass you have on the rim
3. Keep in mind the benefits Jan Heine at Rene Herse bikes preaches about having a supple tire to smoooooth the ride to reduce fatigue.
4. Just use racks when you need them to drop mass (check out the setups used by Jan for his rando bikes, maybe)

.... and that is free physics advice from the interwebs!

Russ Roth

I've been happy with Clement/Donnelly x'plor ush tire, I've been using the 35 but I believe they come in a 38c. They've got a nice round profile and a more solid center strip that lets them move quickly. Can still typically average 17.5mph on the bike path unloaded with these tires so I don't think they're much of a slow down in relation to the whole bike vs my road bike on the same path.

kroozer 

What kind of touring do you plan on doing? Your bike looks great for a heavily-loaded and/or rough road trip, where speed and efficiency is not really a concern. But for a lot of trips it would be overkill. You mentioned "light" touring, which conjures up light loads and good roads, and maybe not camping or cooking. If that is the case then I would use some sort of all-rounder road bike, a sport tourer, gravel rider, hybrid, etc., if I had the choice. If that's your only bike then don't worry about it, it's great and just get out there and do it. My current road tourer is a 1972 Motobecane Le Champion, which was a 21 lb road racer in its day. It has wide enough clearances for 650Bx42 tires, and it really moves on the pavement, yet can handle decent gravel roads with no problem. It probably wouldn't handle a really heavy load very well, but with 20-25 lbs it's great. My brother and his wife go even lighter: they also ride old racing bikes with 700x25 tires. They ride on paved roads, stay in hotels, and just carry small bags with some tools and a change of clothes. Just depends on the conditions.

ilchymis

Just want to belatedly follow up and say thanks for all the suggestions here. I checked out the Rene Herse tires, but ultimately (based on previous good experiences with Schwalbe tires and the low rolling resistance specs mentioned above) went with the Schwalbe Marathon Almotion HS603. These make a noticeable difference, improving not only rolling resistance but also comfort compared to my previous tires (even though the Almotion is narrower).

djb

What width did you go with?

xroadcharlie

First, That's a beautiful bike BTY. Tires are the only thing you need to change IMO to improve performance. The mud flaps probably add more wind resistance then then both racks. If you can snap them off and stow them when you don't need them, I'd consider that. And fenders are a must. The Dynamo might take a small amount of power, and probably wouldn't be my first choice buying new, But since it's already there, I would definitely keep it. I love the concept.

Upgrading the tires is by far the most Significant step and probably the only step I would take to improve the bikes performance. The ones you've chosen are a fine choice for sure. A small weight difference (Dynamo hub, Fenders, Racks etc.) has little effect overall as the added effort to climb low inclines and hills is returned on the downside. Weight is far more important racing where that sprint to the finish line or passing requires fast acceleration. The extra coasting ability of the heavier bikes doesn't help much once we pass the finish line.