Viewing 40 posts - 1 through 40 (of 46 total)
  • Olympic BMX – gears!?!
  • Premier Icon monkeyboyjc
    Full Member

    https://www.bmxnews.com/2021/07/19/bmx-racing-shifts-into-controversy-at-tokyo-games/

    Interesting – could we see a close ratio 2sp Shimano groupset soon? Might be good for park bikes…..

    Premier Icon finbar
    Free Member

    That is…. rad, I think.

    Given the 4130 frame has long been dead and buried for meaningful competition and carbon and discs are in BMX racing to stay, why not whack a derailleur on too?

    Premier Icon rOcKeTdOg
    Full Member

    Been doing start gate gears for years I think, you’re only allowed one shift

    Premier Icon 5plusn8
    Free Member

    There was Browning 2 speed BITD. Never fancied it then.
    https://bmxmuseum.com/forums/viewtopic.php?id=807672

    Premier Icon dc1988
    Free Member

    It will certainly test whether Shimano gears can shift perfectly under load!

    Premier Icon matt_outandabout
    Full Member

    Let me get this right…

    Gravel = old skool MTB with curly bars.

    Now.

    BMX = kids bike with gears?

    🙃

    Premier Icon NormalMan
    Full Member

    Premier Icon
    matt_outandabout
    Full Member

    Let me get this right…

    Gravel = old skool MTB with curly bars.

    Now.

    BMX = Raleigh Grifter

    🙃

    FTFY

    😂

    Premier Icon sirromj
    Full Member

    My Dad got me a 2nd hand BMX with 4 derailleur gears back in the eighties. Loved it could escape all the bigger boys trying to chase me!

    Premier Icon RustyNissanPrairie
    Full Member

    Bit disappointed it’s nothing more ‘factory’ than a Zee mech and a shifter on the wrong side of the bars considering its the Olympics.

    Centrifugal actuated beryilum sun/planetary gearset in a ti flanged carbon shelled hub sorta thing….

    Premier Icon sharkattack
    Free Member

    I’m not into racing but imagine the roof gaps you could do.

    Premier Icon thisisnotaspoon
    Full Member

    That articles wierd, like it’s been written by someone who’s never seen/used gears.

    Will it survive or blow up? It’s a 44t chainring, and it’ll be shifting once up to speed, the actual chain tension at that point is going to be really low.

    What secret gearing is it? You have a photo, just count it! Does look like a small difference though, which begs the question, why bother? Is ~7% enough to give a meaningfull advantage when the start ramp is that long and steep?

    Developed? It looks downright bodged! They’ve not even used the Shimano mech hanger standard (the one that could make it stiffer and more reliable by getting rid of that top link).

    Premier Icon Phil_H
    Full Member

    BMX = Raleigh Grifter

    That brings back painful memories of multiple testicle/top tube interfaces😱

    Premier Icon ransos
    Free Member

    BMX = Raleigh Grifter

    My Grifter was three speed…

    Premier Icon Northwind
    Full Member

    RustyNissanPrairie
    Full Member

    Bit disappointed it’s nothing more ‘factory’ than a Zee mech and a shifter on the wrong side of the bars considering its the Olympics.

    Probably pretty ideal, though- Zee’s pretty light and has the short cage, and it’ll give them production levels of reliability and testedness. It’s got a simpler job to do than a dh gearing setup and doesn’t need the strength either.

    The shifter’s pretty inelegant though.

    Premier Icon monkeyboyjc
    Full Member

    The shifter’s pretty inelegant though.

    True – but it’ll only need to be used once in a race….

    Premier Icon FunkyDunc
    Free Member

    In that picture linked, the chain line looks truly awful though, it would get any roadie having nightmares about the 2 watts of power loss through the chain set

    Premier Icon kerley
    Free Member

    “If Twan runs a typical 44×16 gear ratio, and opts for the 1st gear to be 44×17, he could potentially have a huge acceleration advantage out of the starting gate, down the hill, and down the first straight, then he could shift into his typical 44×16 gear in turn one for the rest of the race. Just speculating on the gear ratios, as Twan has not confirmed what they are.”

    Speculating indeed as a huge acceleration advantage is not going to be seen by using a 17t over a 16t and within 20 metres you would already be changing up a gear. I suppose the proof will be in the pudding and my money is on it making no difference.

    Premier Icon crazy-legs
    Full Member

    I suppose the proof will be in the pudding and my money is on it making no difference.

    At the last Olympics, the Americans brought a new track bike design with the drivetrain on the left. Whole bunch of sales spiel about how having it there on a team pursuit bike meant better balance as the bike was turning left and leaning inwards, improved aerodynamics blah blah.

    It made no difference at all, their qualifying speed/time was way off anything special. But it did get everyone talking about them.

    Premier Icon lovewookie
    Full Member

    BMX = Raleigh Grifter

    My Grifter was three speed…

    they all were for maybe a month, then if anything like my mates, it’d go, easy gear-slip gear-really hard gear as no one knew how to correctly setup a toggle chain.

    Premier Icon nickc
    Full Member

    There was Browning 2 speed BITD

    Overcomplicated much?

    Premier Icon kayla1
    Full Member

    It’s a balance I reckon, getting the gearing right for something like this. If 44:16 is optimum, in that that’s what he can push from the gate to get a decent start against others running (probably) the same gearing, then maybe he can use 44:17 to get going and shift up to maybe 44:15 into the first turn? It’d have to feel familiar enough to start the race with so you didn’t waste all the gate start practice you’ve done over the years on 44:16 gearing but just different enough to give an actual advantage. It might work this one time but once everyone else starts using it (like holeshot devices in MX and MotoGP) the advantage is gone and you’re at a disadvantage if you don’t use it. Also, if he wins gold will he ‘only have won because he had gears’?

    Whatever, I like it, and as someone said BMX racing is so far removed from its roots (4130, Shimano DXs, CW bars etc…) that stuff like this doesn’t really matter to yer average BMXer.

    Premier Icon oldtennisshoes
    Full Member

    I’d be surprised of that actually makes it to the start – my money is on mind games.

    Premier Icon igm
    Full Member

    The Di2 version will be betterer. 😉

    Interesting they’ve flipped a rear shifter rather than using a front shifter (and yes you could use a front shifter ever though the cable pull is wrong – you just set the smaller sprocket mech position on the limit screws).
    Presumably it’s to make it a single shift / release only device.

    Premier Icon nickc
    Full Member

    The Di2 version will be betterer.

    or SRAM AXS with a blipper in the grip.

    Premier Icon ianpv
    Full Member

    Going from a 16 to a 17 is big gear change in BMX – would make a massive difference at the level those guys are at.

    Premier Icon kerley
    Free Member

    Going from a 16 to a 17 is big gear change in BMX

    It is about 3 gear inches so not what I would call a big change. When first spinning up at say 30rpm the difference in speed between 16t and 17t is less the 0.3 mph and the gear change would have to be soon after that. Really can’t see it helping and could just actually hinder as a gear change needs to be thought about/timed etc,.

    Guess we will see, if it gets used.

    Premier Icon scud
    Full Member

    I don’t know about you, but when i ride singlespeed, the drive to the back wheel feels a lot more direct, in that if i ride 46/16 like i do on my road SS, it feels a lot easier than if i picked same gear ratio on geared bike and tried to stay in that one gear, if thats makes sense, so i wonder if they tiny delay in freehub and geared drive train makes up for the direct feeling of SS?

    Premier Icon BearBack
    Free Member

    Watching the test event at the tokyo track and theres surely scope for a longer gear.
    I know BMX always is always furiously high cadence (in the brief moments that pedalling is possible) after the first turn so being able to deliver several high torque pedal strokes vs several dozen 120rpm+ Stokes must be a benefit.

    Will be interesting

    Premier Icon ianpv
    Full Member

    When racers change gears they normally go up or down a tooth on the front 44 to 45 or whatever, depending on the track. Going up or down a tooth on the back is a big difference.

    These guys are at a monstrously high level – and the race is pretty much over at the first jump. So what you think of as a small difference is actually pretty big in bmx.

    Premier Icon BearBack
    Free Member

    Really can’t see it helping and could just actually hinder as a gear change needs to be thought about/timed etc

    Gear change while air pedaling the first double I suppose 😉

    Premier Icon sharkattack
    Free Member

    Is it on telly? Will we be able to see it in action?

    Premier Icon paule
    Free Member

    Gear change while air pedaling the first double I suppose 😉

    My thoughts exactly

    Premier Icon RustyNissanPrairie
    Full Member

    I’d go up a tooth (17t) for starts and drop a tooth for the rest of the track, 44:16 is a compromise between being able to fire out of the gate but be able still spin for the rest.

    I’d have thought at the very least they’d have configured a better/simple shifter – it only needs to drop a single gear once (and won’t need to upshift).

    Premier Icon scratch
    Free Member

    Gear change while air pedaling the first double I suppose

    Bringing the classic ET trick back out of retirement

    Premier Icon zerocool
    Full Member

    Shimano and SRAM are already working on their new 10-42 2 speed groupsets for 2023.

    Premier Icon rOcKeTdOg
    Full Member

    You can by an original 2 speed BMX rear mech if you want, this idea is not new
    https://www.bicycleheaven.org/products/decal-for-schwinn-scrambler-36-36-bmx-bikes

    Premier Icon rOcKeTdOg
    Full Member

    Forum update double post glitch

    Premier Icon kerley
    Free Member

    These guys are at a monstrously high level – and the race is pretty much over at the first jump. So what you think of as a small difference is actually pretty big in bmx.

    It is still a relatively small change, especially when the gear ratio is 55GI and the start is downhill. We are not talking track sprinters pulling off with a 100GI.
    (I spent almost 10 years riding BMX race tracks, in the olden days when you had to pedal more)

    Agree that a small difference can be felt when that is what you ride/practice with and are used to turning/spinning and it certainly makes a noticeable difference across a whole ride on my fixed gear bike when I change by 1 tooth but the actual difference it makes in starting speed on a downhill start with a very powerful sprinter turning 52GI rather than 55GI is the bit I question, would like to see the difference which we will do on 28th July…

    Premier Icon zerocool
    Full Member

    I’m sure that the World class BMX Pro and his team know what gearing they should be running and if they think it will break or not.

    Premier Icon Jujuuk68
    Free Member

    44-16 was fine for Harry Leary.

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