[no skid marks]

Not sure if this is old news.
About time, great idea.
Not sure why they've not used it on 135mm rear, but whatever.
http://www.vitalmtb.com/photos/features/Prototype-Specialized-1x6-DH-Gearing-Experiment,1491/Slideshow,9952/sspomer,2

 

[monkeyfcuker]

Was mentioned in the Val di sol thread, defo think it deserves it's own thread tho! Damn good idea!

I wonder how they're limiting the mech?

 

[matsO]

I have been using 1x5 gearing two years. You limit the mech by using longer stop screws. I first saw it on Dan Athertons bike like 3 years ago. But it was probably common before that.

What is "new" is the smaller special rear hub/freewheel to manage to squeeze a smaller cog onto it due to the smaller front ring. Hope it gets into production as I would certainly have use for it

 

[monkeyfcuker]

Longer limit screws don't work on SRAM stuff. 7 speed is pretty much the limit.

 

[iRider]

Longer limit screws don't work on SRAM stuff. 7 speed is pretty much the limit.

I am wondering how the Specialized guys modified the SRAM derailleur.

 

[Bikael Molton]

nice to see some new work on 6speed.

what about snappy-snap? 9 tooth on BMX isn't very reliable.

-rob

 

[Polandspring88]

Currently running 1x5 on my trail bike. 33 front by 25-17 in the back. I don't see any reason (short of having to have a segmented cassette) that you couldn't run a 9-17 easily enough.

SRAM X.9 derailleur didn't work due to the way they have the limit screws set up. If you could add material onto the cage you could make it work, but it was easier to order an SLX derailleur and throw a longer screw in there.

 

[Ian Collins]

nice to see some new work on 6speed.

what about snappy-snap? 9 tooth on BMX isn't very reliable.

-rob

9 tooth on the bmx sees alot more torque....on a DH bike you'd only be in the 9th gear while pretty wound out heading down faster sections....you'd never apply the same amount of pressure to that gear as you would snapping a gate in BMX....you don't mash the pedals out of the turns in the hardest gear but more so in the middle of the cluster

on a side note, i thought about this setup years ago when people started running 25/9 on BMX bikes.....funny it took 9 years to finally transpire

 

[frango]

Where do You get 9t cogs? Are these from MTB cassette? or road?

 

[SuspectDevice]

Do you guys realize that there is going to be a ginormous increase in the amount of friction and a very significant increase in rate of chain and cog wear running tiny little cogs?


For any application that involves sustained pedaling, especially at lower wattages, these micro cogs are a bad idea. At higher power outputs drag and inefficiencies in power transfer become less significant, but by even a modest calculation, even at peak power output you will be losing and additional 10% of your power output, vs the typical 2% max losses in a standard drivetrain. The real decrease in efficiency, especially in a dirty system will likely be greater. There is also an issue of aerodynamics- with the length of the rollout of a 32/9 and the high frontal area of current DH race positions any pedaling a rider may be doing would, in many if not most circumstances not actually contribute to any increase in speed- furthermore, if the issue is acceleration from a speed where aerodynamics are less important, a lower gear at higher RPM's will develop more power far more rapidly.

The take home message is thus- if and when this stuff is available, please, for the love of god, don't put it on your slalom or trail bike.

It's pretty rad technology, and has it's applications, but I can assure you that unless we go to electric shifting ala di2, this stuff is also something you will want to avoid in the mud.

The Blackbox program, Hill, et. al. certainly are on the cutting edge and pushing the limits of technology- but I'm not sure if they actually crossed their t's and dotted their i's when it came to due-diligence from a sport-science perspective.

 

[bizutch]

Do you guys realize that there is going to be a ginormous increase in the amount of friction and a very significant increase in rate of chain and cog wear running tiny little cogs?


For any application that involves sustained pedaling, especially at lower wattages, these micro cogs are a bad idea. At higher power outputs drag and inefficiencies in power transfer become less significant, but by even a modest calculation, even at peak power output you will be losing and additional 10% of your power output, vs the typical 2% max losses in a standard drivetrain. The real decrease in efficiency, especially in a dirty system will likely be greater. There is also an issue of aerodynamics- with the length of the rollout of a 32/9 and the high frontal area of current DH race positions any pedaling a rider may be doing would, in many if not most circumstances not actually contribute to any increase in speed- furthermore, if the issue is acceleration from a speed where aerodynamics are less important, a lower gear at higher RPM's will develop more power far more rapidly.

The take home message is thus- if and when this stuff is available, please, for the love of god, don't put it on your slalom or trail bike.

It's pretty rad technology, and has it's applications, but I can assure you that unless we go to electric shifting ala di2, this stuff is also something you will want to avoid in the mud.

The Blackbox program, Hill, et. al. certainly are on the cutting edge and pushing the limits of technology- but I'm not sure if they actually crossed their t's and dotted their i's when it came to due-diligence from a sport-science perspective.

did you watch the vid and here Jacy make some vague reference some of the cogs not even having contact surface with the hub? I think it was something of a piggyback system. So, they're saying only a few of the cogs are transmitting force through the freehub?

 

[freakrock]

take a look at the capreo group... you'll get an idea on how the cogs attach to each other and the cassette body.

 

[chillindrdude]

i think this is a solution in a search for a problem for the avg dh rider/racer. i've never had issues with bashing my chainring/taco/bashguard riding dh or xc. i have had occasional issues with hitting crankarms and pedals on bikes with low bottom brackets. and this is a "problem" easily remedied with line choice and being more mindful about crankarm position during rocky sections.

and i'm a weakling pedal-er because i almost never use my 11t. i'm usually in the middle of my 11-26 cassette

 

[monkeyfcuker]

Er no it's a solution to a problem for top racers, it's not available to the public.

 

[roel_koel]

I stopped using microdrive (9t rear cog) on my BMX because it wore out WAY too quickly to be useful (3 months), as I liked actually pedalling about London on my BMX rather than driving to a skatepark and just doing tricks

I switched up to a larger gearing system (11t rear cog) and enjoyed substantial increase in drivetrain durability - replaced the cog / chaindisc and chain every 12 months


George French (G-Sport BMX / Odyssey) wrote a neat article about smaller gearing systems on BMX a couple seasons back, and worked out the loading on 9t rear cogs was 900 newtons per TOOTH!!

this is a problem of reduced chain wrap, and massively increased wear and tear


the problem with microdrive transmission on MTB is even worse than for BMX?

....using this high loading on a Mountain Bike bike ridden with a multi-shift gearing system and thinner chain, in muddy / wet conditions

what about the durability issues of a mountain bike freehub shrunk to fit a 9T cog?

 

[LukeD]

I stopped using microdrive (9t rear cog) on my BMX because it wore out WAY too quickly to be useful (3 months), as I liked actually pedalling about London on my BMX rather than driving to a skatepark and just doing tricks

I switched up to a larger gearing system (11t rear cog) and enjoyed substantial increase in drivetrain durability - replaced the cog / chaindisc and chain every 12 months


George French (G-Sport BMX / Odyssey) wrote a neat article about smaller gearing systems on BMX a couple seasons back, and worked out the loading on 9t rear cogs was 900 newtons per TOOTH!!

this is a problem of reduced chain wrap, and massively increased wear and tear


the problem with microdrive transmission on MTB is even worse than for BMX?

....using this high loading on a Mountain Bike bike ridden with a multi-shift gearing system and thinner chain, in muddy / wet conditions

what about the durability issues of a mountain bike freehub shrunk to fit a 9T cog?

and this makes me think... oh how about we do cryo-frozen gears like a race car...those are pretty strong..

 

[Delimeat]

Here is a link to the PB article Lots of the same info, but also a photo of a prototype SRAM PowerDome cassette with a 9 tooth cog.

 

[ZoRo]

Do you guys realize that there is going to be a ginormous increase in the amount of friction and a very significant increase in rate of chain and cog wear running tiny little cogs?


For any application that involves sustained pedaling, especially at lower wattages, these micro cogs are a bad idea. At higher power outputs drag and inefficiencies in power transfer become less significant, but by even a modest calculation, even at peak power output you will be losing and additional 10% of your power output, vs the typical 2% max losses in a standard drivetrain. The real decrease in efficiency, especially in a dirty system will likely be greater. There is also an issue of aerodynamics- with the length of the rollout of a 32/9 and the high frontal area of current DH race positions any pedaling a rider may be doing would, in many if not most circumstances not actually contribute to any increase in speed- furthermore, if the issue is acceleration from a speed where aerodynamics are less important, a lower gear at higher RPM's will develop more power far more rapidly.

The take home message is thus- if and when this stuff is available, please, for the love of god, don't put it on your slalom or trail bike.

It's pretty rad technology, and has it's applications, but I can assure you that unless we go to electric shifting ala di2, this stuff is also something you will want to avoid in the mud.

The Blackbox program, Hill, et. al. certainly are on the cutting edge and pushing the limits of technology- but I'm not sure if they actually crossed their t's and dotted their i's when it came to due-diligence from a sport-science perspective.

Great writeup thanks!