Cycling UK Forum

Hi,

If you can do stoppies with your weight backwards, then front brake only will stop you
the fastest. It obviously doesn't apply to going downhill on a loose surface on an MTB.

If the front wheel skids (grip due to tyre or surface) first or the front brake isn't
up to stoppies, then clearly you have got some rear braking left you can use.

As ever YMMV, but road riders should learn to use the front to near full effect
when they want to stop quickly, and the rear brake will be of little help, I
tend to lock up the rear wheel trying to use both when hard braking.

As ever SB is a good read on the subject.

rgds, sreten.

Hi,

If you can't get the left to go to 3 your bike needs adjusting,
probably a stop screw on the front derailleur is not set right.

You have 3 gears front and 9 back = a 27 speed, but
in reality you don't have 27 gears due to overlap.

For your front (left) you'd generally use 1 with
1-5 rear, 2 with 3-7 rear and 3 with 5-9 rear.

Regard 1-3 on the left as general areas of gearing,
low/med/high you need for the prevailing conditions.

e.g. if you know a hill is coming up and are in 2 front,
drop to 1 on the front and go up 2 or 3 gears on the rear.
If you know a downhill is coming up and are in 2 front,
drop 2 gears on the rear and go up to 3 on the front.

Pre-emptively switching the front rings to stay in a
similar gear is something some people need to learn.

You should never need to change the front due to
running out of gears on the back, your crosschaining
and basically in the wrong front gear you should be in.

rgds, sreten.

Rabbit wrote:
People have said that object don't fall at the same speed on earth - except in a vacuum - yet everything I've read on this says that objects fall at exactly the same speed, regardless of mass. That was the original point of the question - why freewheeling allows greater acceleration, but they would fall at the same rate...

Hi,

All objects are subject to the same acceleration due to gravity. All objects are subject to drag in air.
The mass does not affect the acceleration. Objects do not fall at the same speed except in a vacuum.

Hence dropping a rock and a feather together on Earth the rock will hit the ground first,
but as done famously on the moon, the feather plummets just like the rock, no drag.

Your original point doesn't make a lot of sense - but FWIW the heavier rider will accelerate
forwards faster as the incline = drag kicks in, to lead the lighter rider. Both will hit a terminal
free wheeling velocity which is higher for the bigger rider due to higher mass to drag ratio.

Down the hill the bigger rider going faster is falling faster, the same case as in freefall.

rgds, sreten.

Ayesha wrote:
I built my model cyclist as several ‘egg shaped’ three dimensional objects closely fitted.

What is difficult to calculate is the air-flow resistance around the multi element structure.

The volume, surface area, mass and cross-section area can be calculated from the length and girth of each rugby ball shaped element of the whole.

Hi,

What is not difficult to model is changing the scale of your model and its effects.

e.g. take a perfect 1:5 model of a 1000Kg car, it will weigh 1/125 or 8Kg.
It will have a ratio of area to weight 5 times higher than the real thing and
consequently a much lower freefall or coasting downhill speed, whatever
model you are using to predict the actual speed, it doesn't matter.

TBH the problems of tiny things in air currents I think are lost on a lot of people.
Why flies can stick to ceilings is the same reason ants also can stick to the ground.

For a person the more you weigh, the faster you freewheel downhill,
assuming relatively comparative aerodynamic body positions, due
to mass versus area ratio, which decreases with size / weight.

rgds, sreten.

Hi,

Perhaps you can fit a caliper brake, rather than modding the V brakes.

rgds, sreten.

Hi,

Its the mass to surface area area ratio, which increases the heavier you are.

e.g. take a 16 stone person and a shrunken version by half in all dimensions.
The shrunken version would weigh 2 stone, 1/8 the mass, but have 1/4
the surface area, i.e. a x2 ratio of surface area to mass, and freewheel
downhill much slower, and also of course a lower freefall terminal velocity.

Tandems freewheel downhills faster for the same reason.

rgds, sreten.

Mick F wrote:Shortest stopping distance is by using both brakes and sliding my weight back.

Hi,

No it isn't. Weight back yes. Shortest distance is full on front with next
to no weight on the rear, rendering the rear brake next to useless,
and pretty much guaranteed to skid using the front brake properly.

You stop twice as fast with front only, rather than rear only, and if you
can use your rear brake with the front brake, by definition its not the
shortest stopping distance, but saying that its better than flirting with
going over the front bars for some, who don't do the shortest distance.

Whatever, do whatever feels safe to you.

rgds, sreten.

Brucey wrote:but it is a superficial view of the situation
cheers

Hi,

No its not superficial, and you are being everything your
complaining about regarding other peoples opinions.

I learnt a long time ago discussions of something wrong
are endless, any misguided logic is welcome, and it does
become rapidly pointless refuting reams of nonsense.

We are all generally sensible, and understand why we follow
the "accepted wisdom", consequently we also know when
we wouldn't, as being the sensible option in more unusual
circumstances, and don't need those cases pointed out.

Simple fact is your basic "tenet" is "accepted wisdom" is wrong,
and all I get is you don't understand all tyre things properly.
A forum is not the place to argue your opinion on things
to the death to support alternative ideas. If the majority
disagree your simply wasting your time trying to convert
people to your view of things. They will ignore rather
than refute stuff that is alternative to their views,
once it it clear their views are being ignored.

That is because of the way contention is represented
as fact, its a poor argument form, doomed to failure.

rgds, sreten.

Hi,

Steel frames have a fatigue limit, if it is not exceeded it will last indefinetely.
If exceeded it will eventually fail. An aluminium frame has no fatigue limit.

If you have hook alloy rims modern tyres will fit and just fit the fattest
nice tyres that will fit the bike. FWIW if it was a really nice bike in its
time, if will be worth a fair amount to a retro biker. Conversely used
you could pick up a really good modern bike for much less than budget.

rgds, sreten.

Hi,

I can't be bothered to argue the toss anymore, this thread is just turning
into one mans self justifying opinion ignoring the sensible simple logic.

I like others, fit a new tyre to the front, and put the old front on the back.
Its simple, the most safe, and optimises the life of your tyres, accepting
the safety aspects make rear tyre problems more likely, that is the point,
and it your choice how far you want to take the rear tyre before the bin.

Nothing has refuted the basics of the arguement, except exceptions.
It boils down to best safety with a tyre replacement plan.
It is the best plan, as accepted by "common wisdom".

For the vast majority of bicycles.

rgds, sreten.

Hi,

Wider rims will make a tyre lower height, though not much practical
use here. Same as going to 650B will allow even fatter tyres.

One could ask why there is so much width room, on my (cheap)
bike size / width is limited by the chain stays, miles before any
issues with the brake clearance, medium reach brakes though.

rgds, sreten.

OnYourRight wrote:Rolling resistance can’t be the dominant concern or Michelin
would want front and rear tyres rolling in the same direction.

Hi,

Might be true and certainly true for coasting downhill, however
under rear wheel drive (most of the time) it is not so clearcut.

rgds, sreten.

HI,

FWIW I regard treating loading and multiplying it by the inevitably
higher tyre pressures required to maintain the correct tyre drop
a poor factor in determining likelyhood of failure.

Wear on the back is about 3 times the front and when well
worn punctures are more likely. Bad punctures on the front
are more dangerous to the rider. I agree a well worn rear
is more likely to puncture than a hardly worn front.

With the "accepted wisdom" punctures and failure of the front
tyre are much less likely than the rear, that is the point.

To a first approximation tyres get cut up etc depending on time
and the front if only used on the front generally fails due to its life,
it doesn't wear out, again such failure is more dangerous on the front.

Say you hit a dodgy corner, sand, oil, whatever and you aren't
going make it round, which end of the bike do you want to let go ?

Or say your one of those people who like attacking bends, and do
so regularly, you always want the tyre with the most grip on the
front, for the worst conditions your tyres are suited to.

There are no no holes to pick in the "accepted wisdom", its
consistent common sense. You don't have to follow it, but
its pointless to argue it isn't consistent common sense, it is.

If you follow "common sense" you obviously are more concerned
about the condition of the rear, and simply bin it when you deem
it unsuitable for the rear (and totally unsuitable for the front).

All the tyres you buy will be worn to this limit barring some
other form of failure, which is much more likely to be on
the rear than the front, that is the point of the regime.

If you insist on replacing both tyres at once clearly
the "accepted wisdom" won't work, it is irrelevant.
However it does indicate replacing both as a regime
doesn't make a lot of sense, whatever rotation
regime you use within the change both limitation.

rgds, sreten.

Hi,

I'm surprised if the other two are freehub the TDF L isn't also.

But if your right of the 3 the Virtuoso seems your best bet.
Compare it to :
http://www.btwin.com/en/road-bikes/spor ... -bike.html

rgds, , sreten.

Hi,

For value I'd get the TDF Limited. Update the brake blocks on the front.
(Save as spares for the rear). Update the tyres if I didn't like them.
http://www.chainreactioncycles.com/tyre ... t=pricelow
Fit the fattest tyres that will fit, 28mm I presume.

What makes you think the TDF Limited is freewheel ? Or why
have you listed two bikes presumably similar you don't want ?

rgds, sreten.