In praise of riding low pressure tyres fast

[Danneaux]

...if only I knew what type of bike my touring bikes and my foldup bike are so I knew which geometry to select.

Hi Mickeg!

That is a dilemma with this app. The frame geometry profiles do affect the app's pressure recommendations. For example, if I substitute "Dutch City" for "French Randonneur", the pressures change to F/R 24/40 to reflect my change in weight distribution. In my case, I already knew through testing what my tire pressure "should" be, and my positioning on the Nomad with its drop handlebars is very close to that of a traditional French Randonneur, so that may be why my current pressures were essentially confirmed by the app.

The "Obsessive/Custom" option throws up a graphic of a long-wheebase Surly Big Dummylike cargo bike with F/R recommendations of only 9psi, way off what I would have expected unless the bike was running Large Marge tires. Hmm.

Best,

Dan.

[Andre Jute]

That app sounds like a bit of a suck and it and see gimmick for innocents. No innocents around here, though some have guileless smiles. (You can trust them. They ride a Thorn.)

In theory, I like the 15% rim drop prescription. In practice, it's purely for obsessives with time on their hands. I'd rather spend my time cycling. So what if my tyres give 1% less milage than someone who spent hours, perhaps days, measuring a 15% rim drop for all possible loading conditions? A pair of Schwalbe Liteskins 60x622 with a matching pair of Ultraleicht tubes T19A cost Euro 66 landed in rural Ireland and those tyres are still marching on strongly at 7169km, so the saving over around 10,000km is 66 cents.

Instead I propose that you test by riding, which is fun rather than work. Schwalbe, the makers of most of our tyres, give good information. I presume Pasela's makers do too, and if they don't, Dan published a reference to an Andy Blance article on tyre inflation not too long ago in another thread. So look up the makers recommendation for your tyres and and inflate to that, front and rear. Take a ride, take several rides, ride for a week or a month to see what happens when the tubes let out a little air by osmosis. If by that time you forget to follow the rest of my prescription, you've arrived, that's the right pressure for you. If you're inclined to experiment, first increase the pressure 10% and take a short ride. The purpose is merely to prove that an increase is required so infrequently as to be an ignorable condition.

Now reduce the pressure to 90% of the maker's recommendation. Why such a large initial reduction? Because those guys cover their backsides. Their marketing department doesn't want their tyres to get a reputation for giving tubes snakebites, so they bump up whatever the guys in the lab tell them is a safe pressure. Right. Now, at 90% of the recommendation, you're at the native, natural inflation of the tyres on your bike for your weight and circumstance.

Now go down another 10% of the maker's recommendation, 20% altogether. If you love this level, you can very likely safely ride here. The downside might be slightly faster tyre wear, and some tyre sidewalls may be damaged by under inflation, though generally they are damaged only by gross under inflation, not 11% real under-inflation. (This is 100 recommended minus 10% CYA margin = 90% of what the guys in white coats thought right. 10/90 is 11%.) It is unlikely that you will cause more drag by 11% under inflation, and very unlikely that you will reduce drag by overinflation; overinflation will cause faster tyre wear than under-inflation, just like on a car.

In summary: 90% of manufacturer's recommendation is very likely to give you the correct 15% drop at the rim, and to be the native, natural, necessary inflation of your tyres. A reduction to 80% of manufacturer's recommendation will give you more comfort with no or very small penalties in efficiency or longevity of tyres.

[mickeg]

Thanks Dan, I will just use the French Randonneur geometry for my touring bikes.  I have drop bars and use the drops about a third of the time, so that makes sense.  Since the only difference between geometries would be a slight shift of pressure to front from back or to back from front, it is very possible that the difference in pressures from one geometry to the next is within the tolerance of error in my reading the pressure gauge on the pump.  So, not a big deal if I pick the wrong geometry.

My newer Road Morph G and Lezyne Micro Floor Drive have better gauges than the one in the photo, but the one in the photo is on the pump I use 90 percent of the time.

I know that you have calibrated gauges, but I am not going to worry about minor gauge error.

[Danneaux]

Sounds a sensible approach to me, mickeg.

For what it is worth, among my collection of non-certified gauges, there's enough variation to make a substantial difference -- as much as 4psi. Still, if one consistently uses a single gauge, the pressures within a range are pretty consistent even if they vary across the dial or in absolute terms. Any gauge will give one a yardstick for consistency and will allow one to  index and measure cause-effect wrt pressure adjustments.

I was delighted to find the Android app simply for the fun if gives and was encouraged to see others are examining the question of pressure on comfort and efficiency also. I may have simply gotten lucky to find the pressures/configuration matched my Nomad, but it has made me wonder about diddling with the pressures on my other bikes as well to see the effect of their recommendations. I think the tool may be most valuable as a means to get one close. Fine-tuning for one's own needs from there may give the best result. For example, my rando/touring bike runs 32mm road slicks on 20mm box-section rims. The tires add air volume, but the rims take it away compared to a wider, channel-section design. I may have less margin to play with in that case.

The Vittoria tire company also has a free Android app for adjusting tire pressures: https://play.google.com/store/apps/details?id=com.vittoria.itirepressure I have not yet tried it, but it appears to neglect some variables. I suspect it may be geared more toward users of Vittoria tires. Curiosity will soon get the better of me and I'll download it to try.

Schwalbe have an app for Android and iPhones (displaying in German) that seems to show local sales outlets. One screen shows tubes and another a tire pump with the admonition to check pressure every 30 days: https://play.google.com/store/apps/details?id=de.diemedialen.schwalbe.app

Best,

Dan. (...who is far from being "air" to the throne in the tire pressure kingdom)

[John Saxby]

"air" to the throne in the tire pressure kingdom

  No worries, Dan -- to air is human after all, and a throne would surely be out of place in the Republic of Oregon, nicht wahr?  (Just a wee end-of-sentence tag there, to help you on your Euro-trek.)

[Danneaux]

Brilliant, John! 

All the best,

Dan. (...who dearly loves puns)

[Andre Jute]

Something Danneaux wrote the other day brought me to this old thread, and after dipping here and there, l read the whole amazing thing in sequence.

There's something worth adding, and it has to do with the job the sidewall does.

A peak, highly praised commuter tyre is the Schwalbe Marathon Plus, which offers high security on city streets with considerable broken glass on them. The M+ achieves its enviable resistance to intrusions by sharp objects by a protective band incorporated in the rolling surface, and hard, stiff compound on the sidewalls. It is operated in the midrange of inflation pressures by road bike standards. It rides like a steelshod wooden-wheeled tumbril on its way the guillotine. Even lowering the pressure doesn't improve the thing's ride much. I also have Bontrager Elite Hardcase in the same size (37mm) as the M+, and they're equally a convincing argument that intrusion security comes at the cost of pain in the posterior. Of course, I realize that the broken glass in and near the gutter in some cities, which is where cyclists are forced to ride, almost demands a hard sidewall.

The problem with the hard sidewall is that out on the open road, where you may want to ride on sweeping curves at speed, the hard tyre, laid over onto part of its sidewall, is intrinsically both slower and more dangerous to the cyclist's health than a tyre with a soft sidewall, like the Pasela which for years was a Thorn default. The reason the M+, otherwise an admirable tyre (except for its wretched ride), is less secure than a comparable tyre with a soft sidewall is that the stiff sidewall in a turn doesn't allow the flat, intended rolling surface to stay flat on the road but lifts up the outside corner of the tyre, so that essentially it runs on the inside corner and a bit of each of the flat and sidewall, a smaller contact area than in any other maneuver, and wildly misshapen at that.

Contrast now the Marathon Big Apple with the protective band but soft sidewall.

This special sidewall was once an extra on the Big Apples, but back then everybody specified it anyway, so Schwalbe made it the default on all the Big Apples and upped the price of an already expensive tyre a wee bit, which I for one consider a bargain.

So, what makes this soft sidewall, which is more likely to get a puncture in the side than a Marathon Plus, so special, besides the fact that riding on basically farm lanes on Big Apples with the soft sidewall for roundabout 15 years I've never had a damaged sidewall?

The fact is that the flexible sidewall on Big Apple is actually flexible. If you lean the bike over in a corner, the tyre doesn't roll over, the sidewall just bulges a bit -- and the flat rolling area of the tyre stays almost fully in permanent touch with the road. Since all rider control, drive and retardation, and steering, operate through this small interface between the tyre compound and the tarmac, the larger it remains under all operating circumstances, the safer the rider is.

That's just a plain statement of the obvious and observable. But there are subtleties. The shape of the contact patch influences the rolling resistance and everything that flows through that, which is everything on a moving bike. The flexible sidewall, accommodating holding the flat of the tyre on the road to the maximum achievable area, also preserves the shape of the contact patch, which translates to lower rolling resistance and higher speed without reducing the rider's security. The bike also corners faster when the design contact patch is not compromised.

Suffice it to say that due to the flexible sidewalls on my Big Apples, plus the low pressure regime (which insures that I'm not thrown off by bumps and potholes), I used to catch out road racers who never had a hope on the badly surfaced but fast downhills and couldn't believe they were beaten by my funny-looking bike with the huge tyres.

[ourclarioncall]

Andre

just looking at big apples coz you've inspired me

what size/type rim do you use or recommend to use with the big apples?

thanks

[Andre Jute]

I use the biggest available Big Apples 60x622mm on a bike designed from the ground up to take them, a Kranich from the German firm Utopia-velo. See my bicycle page at http://coolmainpress.com/BICYCLING.html or download the Kranich section directly at http://coolmainpress.com/AndreJute'sUtopiaKranich.pdf. The tyres are the absolutely the central design element in that bike, and I arrived at it because I failed to find a trustworthy brazier (only art school welders applied...) for a bike I designed in which the Big Apples would have been absolutely the central design element.

The first thing you need to determine is how wide a Big Apple the fork on your bike will take. Real Balloons <tm> start at 47mm but heavy duty touring Thorns can take bigger. Schwalbe offers include 50mm, 55mm, and I seem to remember a 57mm, and 60mm. All these seemingly small steps add cubic air volume and are most definitely not marginal to your comfort, achieved via the lower pressure you can inflate to with every step in width. There was a German who had the most superb Pedersens constructed for him to sell; he had only one leg and a prosthetic and was acutely sensitive to vibration; he rode in the summer on 60mm Big Apples without mudguards, which wouldn't fit, and in the winter on 50mm with mudguards; he told me it made a very noticeable difference because the volume of air was nearly doubled. Notice the important implication that the wider the tyre, the taller it grows too, and the implications for fitting mudguards.

Ask on the forum here if you don't know how wide your particular fork is.

As for rims, do not for a minute believe ERTRO that balloons work on narrow rims. ERTRO is a trade body, and the manufacturers of rims during the 29er craze couldn't or wouldn't gear up to making wider rims, and bullied their trade body into a lie, that wide rims aren't necessary for balloons. Fitting Big Apples on narrow rims is not only a waste of money but can be dangerous because you have to inflate to a higher pressure; pay attention to what Danneaux has written about rims being split by high inflation.

The minimum width of a rim which will not compromise the promise of the balloon, not only comfort but also high speed security, is 40% of tyre width across the retaining beads (not the outside width of rim). Wider rims in relation to the tyre can allow even lower inflation pressure, which again adds to your comfort and the security.

My 60mm Big Apples ride on 25mm rims specially made for the manufacturer of the bike, which I failed to source when I wanted to build up another wheel. Rigida Big Bulls are a suitable alternative. I inflate once a month to something over two bar, and at the end of the month the pressure can be down to about 1.6 bar; in around 15 years on Big Apples I've had two punctures, one from jumping a curb on a building site, one from riding at 55kph through a large pothole, both of them rider error through an excess of exuberance.

You can find wider rims in the mountain unicycle niche group; Kris Holmes (name given from memory) rims are especially well regarded; a bicycle designer I know weighs 350lbs and he rides Big Apples on these Holmes MUNi rims--and he inflates to around about the same as I do!

Big Apples aren't without a downside. They're heavy and expensive. They lack tread -- they have symbolic tread which doesn't do anything except reassure the traditionalists who haven't yet caught onto the scientific truth that smooth tyres roll further and faster without all that hysteresis of creeping, crawling tread as it deforms and slows you down.

Do not be tempted by the special racing Big Apples which lack the protection layer; they are intended for only one race, presumably if you don't get a puncture before race-end.

One more thing. I don't use the standard Schwalbe Type 19 tubes for balloon tyres, preferring instead the lighter Type 19A Extraleicht. I've never had any indication that they're inferior in service in any way, and they do save some weight; this is a common conclusion for those who try them. But otherwise, the weight of the Big Apples isn't much of an argument against them: they take more energy to get going, sure, but they also keep going without further energy input for a long way because of the barbell effect of their weight at the furthest extent of the spokes. The rollout of Big Apples is absolutely amazing. In any event, if you're a downhill speed freak, the Big Apples' security is more than ample recompense for their weight.

If you're offered a choice, and you can afford it, take the Big Apples with the most expensive belt and compound. They all (except the specialist racer) have the super feature of the special sidewall that was an extra on the early Big Apples. The best compound has an amazing lifespan. At 8500km I noted that my Big Apples were half-worn, despite not being mollycoddled. If you know that previously, excluding only the uncomfortable Marathon Plus, my best mileage on other-brand tyres never reached 2000km per set, you'll understand why I find the longevity of the Big Apples impressive. You can ride the Big Apple's until the colour of the anti-intrusion band can be seen.

The Big Apples are all-round a very special tyre, and a riskless recommendation for almost everyone.