[python] Re: Tire for Breakfast?
- From: George Durbridge <gdurbrid@xxxxxxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Thu, 28 Apr 2011 08:15:07 +1000
Dirk,
You will have looked into this, but Schwalbe recommend running Big
Apples at much lower pressures. You do get lower rolling resistance on
smooth surfaces by increasing the pressure from 2.5 bar to 5 bar, but
not a lot. See the second graph on this page:
http://www.schwalbetires.com/tech_info/rolling_resistance
The information on that page is obviously dated, and Schwalbe have
reduced rolling resistance on many of their tyres in the last few
years.
The stress in the rim is related to tyre pressure - as far as I can
tell, it is directly proportional. Schwalbe advise against using high
pressure in wide tyres on narrow rims:
http://www.schwalbetires.com/tech_info/tire_dimensions
There is another factor, which may not apply to you. On some of our
roads, which are fairly rough, particularly the unsealed ones, we get
lower rolling resistance by lowering tyre pressure. At the lower
pressure the tyre deforms around a pebble, which takes less work than
lifting the bike over it. This has been checked by roll-down tests on a
hill with a roughly-sealed road: Marathons at 80 or 90 psi were quicker
than the same tyres at 100 psi (roughly 5.6, 6.3 and 7 bar).
I don't know of any measurements, but on a very rough gravel lane, I
found it easier to push Big Apples at 2 bar than at higher pressures.
Regards,
George
On Wed, 2011-04-27 at 14:25 +0200, Dirk Bonné wrote:
> Hi George,
>
> quite high. The BAs are specified up to 5bars, but I usually pump up to
> 5.5 or even 6bars.
>
> I broke in total 3 rims. The one in the picture held less than a year
> and is may be a faulty fabrication. The other 2 broken rims were
> installed on my baby python (RIP), and were quite old: about 10years and
> had considerable wear on the flanges (V-brakes). I may have ridden 4
> years with BAs on these rims, before that marathon 35-406 or
> vredresteins monte carlo 37-406 (my favorites at the time).
>
> I have a new rim now: "schürmann reflex 19"
> (http://www.schuermann-rims.com/rims/index.php?id=21) and they are
> specified for a 62mm tire ( no pressure specs though :-( ).
>
> Dirk
>
>
> On 26.04.2011 23:16, George Durbridge wrote:
> > Dirk, the rim cracking looks bad: what pressure are you using in your
> > Big Apples?
> >
> > On Mon, 2011-04-25 at 15:15 +0200, Dirk Bonné wrote:
> >> Arggh wrong picture, it was this one I wanted t show:
> >>
> >> https://picasaweb.google.com/dirk.bonne/Pythoon#5591445038290460706
> >>
> >> On 25.04.2011 15:13, Dirk Bonné wrote:
> >>> Be aware that the rim must be up to the extra force caused by a big
> >>> apple (the force on the rim goes up lineary with the width of the
> >>> tire). I have broken in total through 3 rims, they split open either
> >>> at the flange
> >>> (https://picasaweb.google.com/dirk.bonne/Pythoon#5501268362855244498 ),
> >>> or in the middle where the holes to access the nipples are drilled.
> >>>
> >>> The solution is to have a good quality rim that is wide enough. Big
> >>> apples are still worth the trouble, cause it is much more forgiving
> >>> when riding through potholes.
> >>>
> >>> DirkB
> >>>
> >>> On 25.04.2011 11:28, Gerald wrote:
> >>>> Hi All,
> >>>> Thank you for all the feedback! Good to hear that you do not
> >>>> experience the same extreme tire wear. Gives me also the
> >>>> confidence it is just the cheap tire, not the concept.
> >>>> The alignment is OK, maybe could be better but we are talking
> >>>> about 2-3 mm here.
> >>>> Guess I will try either the big apples or the marathons and see
> >>>> how they last.
> >>>>
> >>>>
> >>>> Best regards
> >>>> Gerald
> >>>>
> >>>> On 21.4.11 20:58 , Dirk Bonné wrote:
> >>>>> Hej Gerald, I always put on big apples (50-406) on my python
> >>>>> (pythoon now). There is no extraordinary tear on them - in fact
> >>>>> the tires never wear out, because I have always need to replace
> >>>>> them from the cuts made by the silica stones, instead of the
> >>>>> wear of the rubber.
> >>>>>
> >>>>> Dirk
> >>>>>
> >>>>> On 21.04.2011 13:00, bepb@xxxxxx wrote:
> >>>>>> Hi,
> >>>>>> five weeks after roll-out off my 20" python, the tire off the
> >>>>>> front wheel is finished. Either the tire was rubbish from the
> >>>>>> start or the bike eats then for Breakfast, or both. The tire
> >>>>>> was more or less new.
> >>>>>> I unterstand that both the frontwheel drive as well as the
> >>>>>> smaller size will add to tire wear, but this seems a bit
> >>>>>> extreme.
> >>>>>> I now wonder which tire to buy. Just again the cheapest
> >>>>>> availabe or is there some type that will last longer? Any
> >>>>>> expiriences?
> >>>>>>
> >>>>>> Gerald
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
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