CJ wrote:Rolling drag is indeed relatively unimportant for those cyclists who work their socks off to go as fast as possible, because for them aerodynamic drag is indeed hugely greater. But paradoxically, if you're a slow cyclist intent upon (or only capable of) expending a minimal amount of energy, rolling drag matters a great deal, because for you it is likely to be the largest single factor making you even slower - and the only one you can easily do something about.....
I didn't ride a lot of miles last year so have put on weight and am less fit than usual. Compared to my 700c bikes with their 28/25 Conti Gatorskin/Grand Prix tyres I was finding my 26" bikes with heavy Big Apple and Conti Double fighter tyres hard work and draggy.
Now the 26" bikes seem to roll as well as the 700c bikes. They feel nearly as comfortable as the fatter tyres they replaced, presumably the higher tpi makes them more flexible.
I don't know how durable they will be but so far I like the way they feel.
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Last edited by Erudin on 11 Sep 2014, 5:56pm, edited 2 times in total.
I was riding my town bike thinking 'this is hard work...' the other day...
Duh.... the tyres were a bit soft, and because they have stiff-ish sidewalls, you still feel every bump and it isn't immediately obvious (to me...) that the tyres are a bit down on pressure; not like it is with really supple tyres when they are down a bit.
Back to full pressure again and the ride is nothing like so comfy but it is a lot quicker!
If I had just discovered bicycles and someone told me tyres with supple sidewalls would improve comfort, I would be incredulous. It intuitively seems that no sidewall could be so stiff as to significantly affect the suspension of 80-odd kilograms. And yet it is so, and the difference in comfort between various tyres of the same size and pressure can be quite astonishing and often more noticeable than the difference in rolling resistance.
I did a short rather primitive roll down test yesterday evening on my two bikes. I managed with some difficulty to find a short slope which levelled out. I say difficult because most of the slopes on the industrial estate I was using would result in me running into a main road or into a wall or a kerb before coming to a halt!
Anyway, the two bikes are a 1992 Dawes Horizon tourer and a 2001 Dawes Audax. Both weigh between 12 and 13 kg. The Horizon has 17 mm Alesa Endeavour rims with very old 32 mm Conti Top Touring tyres while the Audax has 15 mm Mavic MA3 rims with newish 25 mm Conti Gatorskins. For what it's worth both have identical hubs - Shimano Tiagra with the chunky external rubber seals. A crude measuement with a pair of calipers and rule gave the gatorskin a width of 25 mm but an undersized 30 mm for the TT. I suspected they were so since they always seemed narrower than the Vredesteins I had before.
I used the method as described by Mick in his video though I found it a little hard at the end since as the bikes slowed to a near standstill, I started to wobble and eventually had to put a foot down before quite stopping.
Anyway with bikes straight from the garage they both seemed much the same - i did three runs for each bike. This tended to confirm my intuitive feeling that they rolled about the same. I run the Horizon at 5 bar front and back and the Audax at 6.5 bar - though once a week I'll tend to pump up the back but leave the front if it seems OK by a squeeze test.
Back in the garage I restored both bikes to the above pressures and took them out for a repeat. Both went significantly further but again both were about the same.
Looking at the Heine paper on inflation pressure and tyre drop I'd say both sets of tyres were overinflated for my low 60 kg weight but were probably both at about the same percentage drop (remembering that the TT is actually 30 mm). When I get a chance I'll repeat the experiments with some different pressures. Certainly at these pressures the ride on the 5 bar TT is smoother than that on the Gatorskin. The Horizon has a 531ST fork (the old style with a wide oval). I believe the Audax has a 531C fork though it is not labelled. It's significant that any extra spring in the lighter fork does not restore the ride quality to that of the Horizon with it's wider tyres at lower pressure.
I had been proposing to rebuild my Audax with a Spa steel Audax frame since as the clearances are all over the place it's not possible to fit 28 mm tyres with guards. Now I'm not so sure - I might be better off improving the tourer instead! What would happen with a carbon fibre fork and 28 mm tyres, I wonder? Is 28 mm near enough to 30 mm to give a similar ride? Perhaps I should get some 28 mm tyres and try them in the Audax with the guards off.
I once did the Birmingham - Oxford ride - well, 11 of them over 10 years.
There's a section after the Cotswolds I think it was, a long, open straight bit of road - maybe a couple of miles, with a very slight down gradient.
With my self-imposed restriction of not pedalling above 20mph, I noticed a significant difference in speed between my bike (originally a Peugeot Vitesse, exchanged later for a Dawes Galaxy) and all of the mountain bikes I came across - I was able to freewheel along this stretch with no pedalling, overtaking most of the mountain bikes - all of which had their riders pedalling to keep their speed up!
Best illustration of (probably) rolling resistance I can think of.
Brompton, Condor Heritage, creaky joints and thinning white (formerly grey) hair ""You know you're getting old when it's easier to ride a bike than to get on and off it" - quote from observant jogger !
Interesting test, NetworkMan. If you’re interested in the comfort and speed of your tyres, consider swapping the the Gatorskins for something plusher.
Rmurphy195: your hill illustration is muddied by rider weight and aerodynamics; at 20 miles per hour the latter is significant. If your road bike (or clothes) puts you in a more aerodynamic position than the mountain bikers, you may roll faster even if your tyres have greater resistance.
Probably it was some combination of tyres, weight, and aerodynamics.
..........consider swapping the the Gatorskins for something plusher.
Perhaps - have you any suggestions? However I suspect that without going wider I won't get the smooth ride of the old Conti TTs and likely anything plusher will be more puncture prone or cost two arms and legs!
BTW I never could understand why they stopped the old Conti TTs. I use this bike for shopping twice each week riding along a cycle track and have only had about one or two punctures in over 10 years!
....overtaking most of the mountain bikes....
Not all fat tyres are good. Mountain bike tyres with knobbly treads are poor. Also, as mentioned, aerodynamics have a much bigger effect at 20+ mph.
Having swapped the Conti TTs for 35/37 mm Vittoria Voyager Hypers I repeated the test comparing the Hypers with the Gatorskins. As before the Gatorskins were at 6.5 bar and I initially inflated the Hypers to 3.5 bar so as to give similar tyre drop. Although the bike with hypers did roll further and this was repeatable, I felt the difference was pretty negligible - about 1 metre in a run of 30 metres. Increasing the pressure in the Hypers to 4 bar gave a similar result. I was a little suprised since I expected the Hypers to be significantly better, though just what is significant on a roll down test at a deliberately low speed (5 mph max) is hard to guess. On rough surfaces the ride on the Hypers is much smoother as you'd expect.
So far I'd say that when tyres are inflated to give about the same tyre drop:-
1. Decent quality tyres roll about the same on smooth surfaces. 2. Wide tyres roll better on rough surfaces. 3. Wide tyres give a better ride, especially on rough surfaces.
It's also now pretty well established that at the same pressure:-
4. Wide tyres can roll better than narrow ones if they have sufficiently flexible walls etc.
and a fair guess that:
5. At the same tyre drop wide tyres roll better on rough surfaces. 6. Wide tyres probably last longer since the wear is distributed over a larger area.
So I'd conclude that all narrow tyres have to offer is better aerodynamics and lower weight.
NetworkMan wrote:2. Wide tyres roll better on rough surfaces.
On a hard surface maybe, but do they on a wet or muddy or otherwise mucky surfaces? This is never mentioned. I don't mean surfaces that are really deep in mud such as you might find on mountain bike tracks etc., but off road hard surfaces/cycle tracks that have a top layer of mud/leaves etc in winter. I find it harder to cycle on these surfaces whatever the tyres are when the surfaces are wet than when they are dry. It also feels that it's harder to pedal with wider tyres than narrower ones, but I've no proof - it's just an impression. It seems to me that, as all tyres will sink to the hard under surface layer, the wider ones will displace more mud etc. than narrower ones, and thereby have more drag as they cutting a wider channel. Or looking at it another way, with a wider tyre there is more surface area in contact with the "sticky" surface and hence more drag.
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
It seems to me that on a little mud, wet leaves, etc. traction is more important than drag. A little tread helps more than anything, but with slicks, wider is better.
“In some ways, it is easier to be a dissident, for then one is without responsibility.” ― Nelson Mandela, Long Walk to Freedom
I'd guess that when there wet leaves/mud about there are so many variables it's hard to guess just what would be best, and equally hard to do a repeatable experiment. All I know is that it's hard work riding through winter gloop of any real depth!
NetworkMan wrote:6. Wide tyres probably last longer since the wear is distributed over a larger area.
I'm wondering about this one. The middle of the tyre whether wide or slim is still the middle and is always a constant. Wouldn't wear rates be the same?
Bill
“Ride as much or as little, or as long or as short as you feel. But ride.” ~ Eddy Merckx It's a rich man whos children run to him when his pockets are empty.
MikeF wrote:It seems to me that, as all tyres will sink to the hard under surface layer, the wider ones will displace more mud etc. than narrower ones, and thereby have more drag as they cutting a wider channel. Or looking at it another way, with a wider tyre there is more surface area in contact with the "sticky" surface and hence more drag.
Among the various versions, Panaracers Smoke tyre came in both a standard 2.1" and what they called at the time, the Smoke Lite at 1.9"...(might've been 1.75" actually) It was either an advert they made or a magazine article I read that said the Smoke Lite was better in gloopy muck as it would cut through the wet stuff to the harder stuff underneath. I had those tyres on one of my mountain bikes at the time and although I can't say for 100% certain, I don't remember squelching around as much as the other guys in the club.
Bill
“Ride as much or as little, or as long or as short as you feel. But ride.” ~ Eddy Merckx It's a rich man whos children run to him when his pockets are empty.
I found out, by accident, a number of years ago that my then 23mm tyres on my road bike were better in several inches of fresh powdery snow than my fat MTB tyres as they did indeed cut through rather than wallow so steering was much better. Not much grip mind!
Rick.
Former member of the Cult of the Polystyrene Head Carbuncle.
There are few things more satisfying than an early morning journey on narrow tyres in deep powder snow.
Sadly, there are few things less fun than an evening ride home on narrow road tyres on the hard ice formed from deep powder snow by a day of cars skidding and spinning wheels on it
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk All the above is CC-By-SA and no other implied copyright license to Cycle magazine.
