What is a 'fast bike'?

TowerRider

I see the phrase quite often but don't really understand it and more so recently.

I have seen the phrase before and assumed it meant the tyres, wheels and anything that causes (I guess) friction.

The other day I read on here that the Specialized Rockhopper is a fast bike.

I have a Specialzed Rockhopper and it is certainly not fast, I have to pedal it for it to move and if I stop pedalling the bike will eventually stop. I have climbed a hill before and have seen a jogger disappear into the distance while another ran past. Fair enough I flew past them on the down hill but that doesn't make my bike 'quick bike'.

My tyres are pumped up to 50+ PSI (you do with these tyres) and I understand that made my rolling resistance less BUT another bike would surely have been the same SO that doesn't make my bike quick.

WHAT is OR makes a quick bike?

supersonic

Generally refers to a light bike of a particular genre, with steeper angles for faster handling, and possibly tyres as you say.

Rockhopper is a budget/medium range XC bike so probably wouldn't be given that tag. But is a great bike, solid, dependable, superb frame.

andyrm

As Supersonic says, "fast" very often refers to a light and stiff bike. My singlespeed Bionicon Frequency is definitely "fast" in that sense of the word but in real terms is pretty slow overall by the time you factor in big descents, not being able to blast over stuff anything like as fast etc.

Raymondavalon

TowerRider wrote:

WHAT is OR makes a quick bike?

A bike ridden by anybody but me... :roll:

butcher of bakersfield

Just look at road bikes. Drop bars (riding position), tiny tyres pumped up to over 100psi (rolling resitance), and the ability to lift them with your little finger (weight, obviously).

I guess those are the main elements to a 'fast' bike. Of course, you could go as far down the rabbit hole as you like. For example, the laws of physics dictate (and don't ask me how!) that a lighter wheel will accelerate faster than a heavier wheel with the same power put into it. Which of course, makes sense primarily because you're losing weight, but saving that weight elsewhere on the bike, say the frame, would not have the same effect. However, increasing stiffness in the frame could help efficiently distribute power through the bike, without losing any weight.

Mynameisdann

One with an engine chap

robertpb

Riding with 50+psi in your tyres increases the rolling resistance. :roll:

Lower the pressure to around 30psi and the bike will go faster.

sandy hill

TowerRider wrote:

I see the phrase quite often but don't really understand it and more so recently.

WHAT is OR makes a quick bike?

Its a bike on flea bay being sold by a friend who has no idea about bikes but can Ctrl+C and Ctrl+V. Ordinarily these have no receipt.

Anonymous

Me, I make a bike quick.

bennett_346

robertpb wrote:

Riding with 50+psi in your tyres increases the rolling resistance. :roll:

Lower the pressure to around 30psi and the bike will go faster.

I was sure it was the other way round

Anonymous

bennett_346 wrote:

robertpb wrote:

Riding with 50+psi in your tyres increases the rolling resistance. :roll:

Lower the pressure to around 30psi and the bike will go faster.

I was sure it was the other way round

mmmm, tricky one, it depends on terrain. If there's lots of small rocks and stuff, then a lower pressure tyre will deform over them and will end up rolling better, whereas the higher PSI tyre will have to ride up and over them
Higher PSI is better on smooth trails.

Like most things in MTBing, there is no black/white.

bennett_346

yeehaamcgee wrote:

bennett_346 wrote:

robertpb wrote:

Riding with 50+psi in your tyres increases the rolling resistance. :roll:

Lower the pressure to around 30psi and the bike will go faster.

I was sure it was the other way round

mmmm, tricky one, it depends on terrain. If there's lots of small rocks and stuff, then a lower pressure tyre will deform over them and will end up rolling better, whereas the higher PSI tyre will have to ride up and over them
Higher PSI is better on smooth trails.

Like most things in MTBing, there is no black/white.

Personally i'd of said that rolling resistance is kinda different to that, id always measure it on a smooth flat road as its a truer measure of the tyre, no bias, but like you say there is no clear cut definition to these things.

Anonymous

well, rolling resistance on a flat road is different to rolling resistance on a rough trail. Therein lies the complication.

gavalar1081

My last bike was a Trek 6000. It was so fast and nimble it was unreal.

Before that I had a GT Avalanche 1.0, it weighed as much as a bus and was NOT fast!

Yes tyres, rider, terrain etc make a difference but so does the bike as others have said.

A bit like cars really, there will always be faster one!

bennett_346

yeehaamcgee wrote:

well, rolling resistance on a flat road is different to rolling resistance on a rough trail. Therein lies the complication.

I guess its all really down to how you personally define the word. Id always thought of it in terms of the friction between the surfaces but if you incorporate deformation over rocks it can get quite in depth, if it really is a measure of how fast the tyre lets you move over ground then you could incorporate grippiness in mud, where tackier traditionally slow rolling tyres would move you through faster!

Anonymous

It's resistance to rolling. That's a pretty solid definition. When there are things in the way that impede an object's rolling capacity, these are part of it's resistance to rolling.

TowerRider

Cheers folks....
IF i let my tyres (Spec LK) down to 30 PSI that would be below the recommended pressure - I pumped them to 50 and the bike was quite a lot quicker over all terrain BUT higher than that and I find I feel the bumps too much. I don't faff on tarmac!

Dick Scruttock

I would say 'fast bike' in the sense you are using is more down to the handling, ie steeper head angle and more agile rather than down to the rolling resistance as sonic says.

robertpb

I've used between 18 and 26psi in my tyres over the past 25 years or more.

A year or so ago because this question kept raising it's head I got in touch with a lot of world and ex world champs to ask what was their tyre pressures.

The answers ranged from 23psi to 29psi, I also found that Maxxis test their tyres at 27psi.

The side wall pressure on most tyres seems to come from when these tyres first came about many eons ago, higher pressures and you won't get come backs from side wall deterioration or heavier riders wrecking the tyre.

Continental, Schwalbe, Michelin and Hutchinson all use the 29psi for a rider up to 75kg.

Anonymous

for me the term fast bike is alien, ive never been on one.

however, i can assume a fast bike is basicly a good bike of whatever type,

so a fast dh bike will be one which is well sorted with excellent confidence inspiring geometry on a platform which allows you to push the bike harder downhill than its competitiors because of the way it is designed and especially specced. the right spec will make a bike fast as it will balance between lightweight and super strength meaning you can get more out af a bike, with dh you probably want a bit of weight under you to have confidence in its ability to basicly fall of the side of a mountain.

a fast trail and all-mountain bike would have the same basic advantages over their competitors, good spec whcih considers the connection between weight and strength and good geometry which trades off climbing, descdning and cycling through tight and twisty stuff

often a manufacturer will pick one of those disciplines to be better at which means although it will be excellent at that, it might not be so good elsewhere, i would imagine a bike like that would not necessarily be considered a quick bike whereas one which trades off with spec and geometry to allow quick climbing, quickish descending and good performance through twisty terrain would be considerred a quick bike.

no matter what, no bike is quicker than its rider is able but some riders are quicker on different bikes.

for example, i am always quicker on a fs bike even though i am slower than the speed at which ice changed the topography of our great land.

Anonymous

robertpb wrote:

A year or so ago because this question kept raising it's head I got in touch with a lot of world and ex world champs to ask what was their tyre pressures.

The answers ranged from 23psi to 29psi, I also found that Maxxis test their tyres at 27psi.

You must be very boring dinner party company. But, seeing as i am as well, I thought maybe it's got something to do with racers being pretty light.
I'm guessing you meant XC racers using those pressures. They're all lanky streaks of pi**, a heavier, 14-stone plus rider would need more pressure, in all probability.

And sheeps is actually not as slow a rider as he makes out

tilt

TowerRider wrote:

I have to pedal it for it to move and if I stop pedalling the bike will eventually stop.

TheNorthernTrain

If i ran 18psi in my tyres i would get a pinch flat before i even moved.

I run mine pretty hard, probably around 45 - 50psi because the tyre said between 40 and 60 :? and i like it that way, to me, it feels faster and gives me more confidence, Probably because before i starting running them at those pressures i would constantly get pinch flats. Now i am a fat bugger but i wouldn't call myself too heavy.

It's probably my technique which is, in all fairness, terrible!

Shaggy_Dog

I think when people in the cycling media describe a bike as being fast they tend to mean that it feels less effort to accelerate. A stiff hardtail with light wheels is a fast bike, a short travel full suspension bikes is fast compared to a heavier all mountain bike. I like to say "fast under foot" as if to say, when you put your foot down you can feel it surge forward. Obviously a downhill bike is faster than a XC hardtail down Whistler A-line and a Carbon road bike will go up the Col de Tourmalet a damn sight quicker than a Specialized Enduro but when a journo says fast they mean in an XC sence - usually

Anonymous

unless they're reviewing a DH bike?

Shaggy_Dog

yeehaamcgee wrote:

unless they're reviewing a DH bike?

Now, come on, DH bike reviews don't contain normal words like "fast"

GNARLY SICK RAD etc...

supersonic

I think it was Schwalbe who first really publicised findings on tyre pressures, and since then a lot of people have misinterpreted the findings to be 'less pressure = lower rolling resistance'. This is nonsense, and not what they said at all.

Basically, for a given rider, riding style, bike, weight, weight disrtibution, tyre size, type and shape there is an optimum pressure where rolling resistance is minimized, which is going to vary on those above points. You go lower or higher and the resistance will increase.

Now it may be that it was found that on average many people seemed to run tyres a bit higher. But this is not the same as saying lower = better all the time. Run 5 psi, see what happens!

Shaggy_Dog

cut your hair and get a job supersonic

supersonic

Lol, had to read that twice!

Anonymous

Sonic's on the ball as far as I'm concerned. That's why I suggested that maybe such a low PSI was used by lightweight XC racers.
The sweet spot would vary with bike and rider weight as well as terrain.

pdid

Shaggy_Dog wrote:

I think when people in the cycling media describe a bike as being fast they tend to mean that it feels less effort to accelerate. A stiff hardtail with light wheels is a fast bike, a short travel full suspension bikes is fast compared to a heavier all mountain bike. I like to say "fast under foot" as if to say, when you put your foot down you can feel it surge forward.

This IMO. I would describe my hardtail as a faster bike than my FS simply because it is quicker and requires less effort to accelerate on most types of terrain.