113mph cyclist

[Chris S]

I've just watched 'Speed with Guy Martin', he reached a 113mph on a bicycle by slipstreaming a racing truck. In order to do this he used some weird bicycle with a double chainset to give a single 7.5:1 gear ratio.

Does anybody know why he didn't just use a hub-geared bike? Their top gear is usually around 8.0:1.

 

[TissoT]

Email Brian/Jason Rourke in stoke ....He will tell you exactly why he did it !

 

[rualexander]

Rohloff hub has a ratio of 5.26:1, which is wider than other internal geared hubs.
From the table here http://www.rohloff.de/en/technology/workshop/gear_meters_table/index.html on 26" wheels with a 48 tooth chainring and 13 tooth sprocket, you get a gear development of 11.16m in top gear.
A 7.5:1 gear ratio on 26" wheels would give a development of around 16m
To get this from a Rohloff with 13 tooth sprocket would require a 69 tooth chainring, not impossible but there are probably other reasons why a Rohloff wouldn't be suitable.

 

[Jefferson Meriwether]

Crumpets on a tea plate; I'd be crapping me pants long before I reached the giddy heights of 113mph.

 

[Broughtonblue]

Only impressive if it was uphill

 

[jarlrmai]

I was impressed most by his 1st 400m lap.

Also it seems he could have easily done the record if they had been able to find some long enough tarmac, the almost got there on the 1st "trial" run.

 

[Linford]

Only impressive if it was uphill

Tagging along behind the lorry was the great equaliser. Removing wind resistance levels the playing field.

Must have been terrifying on sand ..even for Guy Martin

 

[Nigel-YZ1]

Just watched it online. Brilliant achievement.
As much as I like going fast I wouldn't try it

 

[machew]

Internal gear hubs have a efficiency of 92% compared to 98% for derailleurs

 

[srw]

Internal gear hubs have a efficiency of 92% compared to 98% for derailleurs

Depends on the gear system and the choice of gear (in both cases). Rohloff reckon 96% for gears 1 - 7 and 98% for 8 - 14. I can believe them.

 

[avsd]

Seen it last night. It was both amazing and crazy. To do that speed on SAND is just mind blowing. I suspect the gear arrangement was selected for strength and reliability. The impact of air resistance was quite an eye opener to me.

PS I think he did that run on 35mm or 38mm tyres. So much for the skinny 23mm we use on the road

 

[BarnieBarnes]

lets face it Guy Martin is bonkers at the best of times, but this was another level. I really think he deserves more praise and exposure for what he has done!

 

[Linford]

Seen it last night. It was both amazing and crazy. To do that speed on SAND is just mind blowing. I suspect the gear arrangement was selected for strength and reliability. The impact of air resistance was quite an eye opener to me.

PS I think he did that run on 35mm or 38mm tyres. So much for the skinny 23mm we use on the road

If you see how the riders in motorsport sit up at the end of the straights to scrub speed off, or ridden flat out and tried it yourself on the track, you would certainly appreciate how much difference it makes Sitting upright on a 600 supersport, max indicated is about 140, tuck in, and the bike starts to accelerate to the top of its gearing (indicated 170)

I used the sitting up air brake style all the time on the track when braking off the long straights, it dropped the speed from 140 to 70 much quicker than if I just used the brakes.

 

[ufkacbln]

Rohloff hub has a ratio of 5.26:1, which is wider than other internal geared hubs.
From the table here http://www.rohloff.de/en/technology/workshop/gear_meters_table/index.html on 26" wheels with a 48 tooth chainring and 13 tooth sprocket, you get a gear development of 11.16m in top gear.
A 7.5:1 gear ratio on 26" wheels would give a development of around 16m
To get this from a Rohloff with 13 tooth sprocket would require a 69 tooth chainring, not impossible but there are probably other reasons why a Rohloff wouldn't be suitable.

I use a Schlumpf High Speed Drive on one of teh recumbent trikes. That gives the equivalent of a 34t / 85t front ring and a Rohloff rear

 

[Banjo]

It would be interesting to know the full spec of the bike. That must have taken the wheels tyres and hubs way past what they were designed for.