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Moultons have held many speed records, and are used successfully in Triatlons.
I was skeptical of the performance of small wheel bikes, but after a bit of googling and reading, I’m fairly impressed.
Much fastness..
http://www.culturecycles.com/2012/06/1988-hutch-hpv-superbike-bmx/
However, wider tyres increase the stress (force for a given area) on the rim if used at the same pressure as a narrower tyreQuick question – if the pressure is the same then in a uniform enclosure (e.g. a balloon) the stress would also be the same by definition wouldn’t it ? What makes the difference in the (single) rim case – bead angle effects / effective cross-sectional tyre radius or something similar ?
OoooOOOooo I think I might be able to answer this!
For any given pressure, the stress will increase as diameter increases (assuming isobaric and all of factors remain constant).
You can tell I’m fun at parties…
😉Haha – excellent ! … although perhaps oddly I would find that fun at a party 😀
That’s a new concept for me, just been looking it up – that’s the circumferential stress though isn’t it, e.g. the tangential stress in the inner-tube, not the radial stress due to the pressure in the tyre ? Just trying to sketch it out in my head what the two effects mean for the static rim + beaded tyre case…. might be a while..
You’re right, that is circumfrential stress not stress on the sidewall.
From wiki “The radial stress for a thick-walled cylinder is equal and opposite to the gauge pressure on the inside surface”. Trouble is, a tyre/inner tube combination isn’t a thick wall.
Thinking about it, I think you are correct about the force remaining the same regardless of tyre width for any pressure assuming the tyre/bead is parallel to the sidewall so, therefore, the force is normal.
Aye maybe – or it might be that the bead is pulling more on the bead hook or something… or not, I keep flip-flopping on that…
This means the equation I made reference to is irrelevant and only serves purpose as material for mental masturbation 😛🙂 Fair shout, it’s still a jolly nice equation though !
However, wider tyres increase the stress (force for a given area) on the rim if used at the same pressure as a narrower tyreQuick question – if the pressure is the same then in a uniform enclosure (e.g. a balloon) the stress would also be the same by definition wouldn’t it ? What makes the difference in the (single) rim case – bead angle effects / effective cross-sectional tyre radius or something similar ?
OoooOOOooo I think I might be able to answer this!
For any given pressure, the stress will increase as diameter increases (assuming isobaric and all of factors remain constant).
You can tell I’m fun at parties…
😉Haha – excellent ! … although perhaps oddly I would find that fun at a party 😀
That’s a new concept for me, just been looking it up – that’s the circumferential stress though isn’t it, e.g. the tangential stress in the inner-tube, not the radial stress due to the pressure in the tyre ? Just trying to sketch it out in my head what the two effects mean for the static rim + beaded tyre case…. might be a while..
Acm wrote:
However, wider tyres increase the stress (force for a given area) on the rim if used at the same pressure as a narrower tyreQuick question – if the pressure is the same then in a uniform enclosure (e.g. a balloon) the stress would also be the same by definition wouldn’t it ? What makes the difference in the (single) rim case – bead angle effects / effective cross-sectional tyre radius or something similar ?
… number 2 in line flat refused to come through as he was “dying” so I got fed up and summoned up all my power to just sod off on a slight uphill.…After they’d done all this work it was bad that a later hill I struggled to ride slow enough for them
to get a tow
Interesting group riding attitude… and when you say you ‘struggled to ride slow enough’, could you elaborate ? Balance ?
but then it’s not much advantage uphill anyway is it?Depends on the slope and speed, there’s going to be some but it might be very small – then again it might be noticeable…
DaSy wrote:
My ride yesterday in the snow and gale force winds certainly showed me that I would not hear a bike approaching from behind, as I was only just making out lorries.I am known as someone who happily pulls on the front all day, as I like the hard work, so I have no issues with people drafting me. My issue is with people doing it unannounced, as this impacts my safety.
So let me get this straight – your hearing is signficantly impaired but you’re absolutely sure he at no point announced his presence ? Not saying he did but would it be fair to say that you can’t be sure, especially if he’d made the effort to get up to you for some assistance ?
For the record, I didn’t have headphones on but it was rather windy which may have lessened my chances of hearing the chap behind me. And just to reiterate: I didn’t mind the guy being on my rear wheel; it was just that he didn’t make me aware of his presenceMaybe he tried and you didn’t hear him ? *shrug*
FTP in ‘manual’ ERG mode,
FTP in ‘manual’ ERG mode, seriously ? One of my brothers has an Atom on order, the sheer amount and consistency of negative feedback on its performance is beginning to worry me on his behalf…
Get a single speed, I find that 40×15 gets me round Hertfordshire quite comfortably 🙂“Single speed” and “comfortably” – not traditionally things that appear in the same sentence 😉
My touring bike setup for climbing, uses a MTB crankset and derailleurs. I started with 40/28 crank and an 11-32 for general hilly stuff.Lovely looking bike – mind if I ask what model the cranks are (XT ?) and any issues with BBs/chainline etc when you put it on ?
XT crankset 40/28, changed outer ring to 44t from 9 speed shimano. It has standard threaded bottom bracket with 2 spacers drive side. I ground off 0.5mm from the drive side spacer to make it absolutely perfect with no catching of chain when cross chained big-big or small-small.
Cheers for that, my main worry was the front derailleur pull (probably not an issue for you, you’re running Di2 aren’t you ?) with the MTB chainset, but i’ll just suck it and see I think.
I think its a perfect setup for me and probably most riders. It allows me to climb silly gradients>30%, maintain a decent cadence 80+rpm and travel on the flat upto 32mph before cadence gets too much @110rpm. Outside serious road racers what more gearing does an average guy need?Completely agree. I was looking at 46/30 originally, sub-compacts and the like, but reckon you’re probably right on the 44/28 – would be ~45km/h @ 90rpm on 44/11 with my wheel/tyre setup and like the idea of the 28T in extremis.. thanks for the idea.
If you look at the ratios and not the number of teeth, the jumps are pretty evenly spaced throughout a 11-32/34 cassette.Yep, and I actually quite like a slightly larger % jump at the bottom of the cassette when i’m doing longer, steeper climbs- I find it often means I just need to shift between the bottom two gears when getting in and out of the saddle, something I appreciate when i’m mainly concentrating on being able to breathe..
Ideally we would be all running triples with an 22 lower chainring and 11-25 close range cassette. But the trend is double crank and wide range cass. My ratio jumps arent huge even with 11-40 cass, I manage happily to vary my cadence from 80-95rpm when climbing long hills. I actually like the variety, wakes the legs up.I was looking at 11-36 cassettes recently, decided against it this time for a couple of reasons, but the interesting thing for me was the difference between the SunRace 11-speed 11-36 and 11-40 clusters – basically they drop the 12T for the 40T. That would be a no-brainer for me as that’s a really appealing granny gear and by the time i’m hitting the top of the 13T i’m invariably going to the 11T in short order anyway. Horses for courses of course.
alansmurphy wrote:
But the jumps can be horrible of the spread is too wide. I ended up with a cassette that had a 28-34 jump on the end of the range and hated it.Ouch, that’s quite the jump there. The new Shimano HG800 11-34 looked interesting to me – 2T gaps all the way up until the last two, which is a 3T then 4T transition. I’ll see how it runs when I get it on, hopefully tonight.
Edit. get the gaps right…
CXR94Di2 wrote:
My touring bike setup for climbing, uses a MTB crankset and derailleurs. I started with 40/28 crank and an 11-32 for general hilly stuff.Lovely looking bike – mind if I ask what model the cranks are (XT ?) and any issues with BBs/chainline etc when you put it on ?
alansmurphy wrote:
The trouble with the ‘cyclist’ label as well is a bit of a problem.Not really, unless you want to also discuss the trouble with the ‘motorist’ label and so on. If you divide any group into ‘lovely people like us’ and ‘idiots not like us’ it’s going to be a bit artificial and the differences probably all but invisible to those not in the know. People everywhere go the whole spectrum from twat to saint, and cycling isn’t any different.
Edit : Oh and i’m from Bristol and can alas confirm there are plenty of idiots of all ages and gender that regularly drive their car the wrong way down the one-way street opposite me, lights on or not. Pointing this out is not always a joyous experience.
How?!The car “parked” in the cycle lane on double yellows had it’s hazards on, so it’s possible that it was broken down…
I wouldn’t be surprised if they were just waiting there because it was convenient for them though.
Since when have hazard lights indicated ‘broken down’?
Since always to indicate that your vehicle may be causing an obstruction. Just because idiots abuse them doesn’t change that.
FWIW ~5′ 5″/165cm and 69cm
FWIW ~5′ 5″/165cm and 69cm
😉