M
Martin Wilson
Guest
>I can top out over 40 going down a long steep hill, pedalling hard in
>big gears on a recumbent with high quality high pressure tyres which
>almost certainly have lower rolling resistance than yours. 40 on a bike
>is fast and generally requires working at it unless you have a very low
>rolling and air resistance.
>
I don't get it, I managed my commuting run in 35 minutes. A distance
of about 7.5 miles. Isn't that an average of something like 13-14mph.
Now a lot of the time I was going up hills at a pitiful 6 mph meaning
to get an average of 14mph I must have been doing well over 20mph
sometimes. I did this run slower than the nighttime run as there was a
lot of traffic so I played safe I wouldn't allow the bike to coast
really fast. Previously I was told that even if I was completely unfit
I should be able to do the run in about 40 minutes. So if my bike can
go beyond 20mph easily and regularly the small increase to near 30mph
doesn't seem particularly amazing but I will check the computer to
make sure the wheel size is right (I'm almost positive its set at
mph). The 40mph is achieved going down a very steep long hill with no
pedalling assistance as theres no way I could assist in anyway as the
gearing isn't capable of it. I have Schwalbe City Jet tyres. 40mph was
frighteningly fast on the bike but there was no wobble. Perhaps some
sort of independant test is in order. I only claim peak speeds of 30
(near flat in my favour) or 40 (down long steep hills).
>> average. It took some nerve/stupidity to do as the brakes took a long
>> time to stop my mass at that speed.
>
>There's the difference between good and indifferent brakes. You weigh
>more than me, but my bike weighs more and even with 4 pannier loads of
>camping luggage it stops very well. But there again it damn well
>*should* do better, as each of my brakes cost more than your whole bike.
>
In fairness though its my weight which is causing the reduction in
braking. The brakes are very effective and far better than the old
style brakes on my Raleigh Royal even though I was probably only 13-14
stone when I rode that.
>> I think a normal relaxed cadence
>> will take the bike to about 24mph in its fastest gear
>
>Unlikely on MTB gearing, especially 6 speed. Not impossible, but I'd
>think unlikely. Maintaining over 20 is pretty hard work IME.
>
Once I put it in rear gear 6 and front gear 3 and look down I'm doing
20+ with a reasonable cadence. I must admit this is one element of the
gears that is disappointing. As you have to cycle like mad to get to
30mph and thats the bikes maximum speed with actual pedal input for me
anyway. I would like faster gearing so I could achieve 30mph without
my legs going ridiculously fast. At the other end of the gearing the
bike can go as slow as about 4mph with normal cadence and its a job to
stay upright. I looked at sheldon brown's site and it looks like many
bikes gears go well above 24mph at normal cadence in their fastest
gear using his gear calculator web page. My top front gear is 48 and
my top rear gear is 12 and according to sheldon broown this gives a
top speed of 30.6mph at 100rpm so lets say for 15 seconds I go flat
out as fast as possible on a surface which has a gradiant slightly in
my favour with my own momentum wanting to go faster why wouldn't my
bike being doing near 30mph? Even at 80rpm the bike should be doing
24.5mph. I'll try to time my cadence but I'm pretty sure its capable
of doing more than one revolution a second especially when gravity is
in my favour.
>It's certainly not slouching about. The UCI hour record, set in a
>velodrome on a pure track racing bike designed for the job by a
>professional cycle athlete (Chris Boardman) is 32.48 miles. Obviously
>keeping up that speed for an hour is /very/ different to keeping it up
>for a minute, but it's the fastest possible sustainable pace on the flat
>on an upright bike without a fairing, under the best possible conditions.
>
Thats an average and not a peak reading and its not with a slight
gradience in his favour its flat.
>
>They'll be very strong, but once you get up past 20 mph (or even near to
>20 mph!) then wind resistance is the real barrier to going faster, with
>the loss to air drag going up with the square of the speed. Which is
>why the UCI hour record is so much lower than the IHPVA record, where
>aerodynamic fairings on recumbent bikes are allowed. This doesn't show
>up on an exercise bike, for obvious reasons.
>
>Pete.
Well its pretty obvious you don't believe my speed claim. Its possible
I set the wheel size wrong but its very unlikely. Looking at the
sheldon brown site I'm reassured that the speed I obtained is geniune.
