The War on the Roads - TV - Sunday night

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Re: The War on the Roads - TV - Sunday night

Postby il padrone » Mon Sep 02, 2013 7:10 pm

C of G is hardly a major issue with braking for road bikes (racers, city bikes or e-bikes). It only becomes an issue if you are likely to go OTB - mostly for off-road MTB riding. For normal street riding the question of braking distance is mainly to do with brake power (get better brakes), traction and skidding (get better tyres and be careful in the wet) or simple recognition time.

Having a high or lower CofG doesn't influence your stopping distance, only the point at which you are likely to go OTB in an emergency brake stop. For an e-bike this may actually be less likely as they have quite a bit of extra weight in rear-mounted batteries and for some a rear-mounted wheel motor, all of which will keep the rear wheel on the ground more.
Riding bikes in traffic - what seems dangerous is usually safe; what seems safe is often more dangerous.
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by BNA » Mon Sep 02, 2013 7:48 pm

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Re: The War on the Roads - TV - Sunday night

Postby VRE » Mon Sep 02, 2013 7:48 pm

lobstermash wrote:
VRE wrote:
lobstermash wrote:I was disappointed that ABC's S**tsville express didn't properly cover the cycling option in their transport episode. The commute race home was won by a car going just 28km/h average...

Are you implying that a typical bicycle commuter could beat that average speed?


Sorry to dig deep into the archives of this thread, but I moved offices last week, adding ~10km to my commute. The first 8km of my ride is the same path I always took, however the extra is along a pretty well thought out bit of cycling path alongside a major artery. My average speed into work has increased from ~26km/h to 28/29km/h in spite of the extra distance, purely because of a slight improvement in cycling infrastructure on part of my ride.

I think with some tweaking to ebike regulations to allow them to match road bike speeds (increased power and regulation on brakes to at least match stopping distances), plus some investment in cycling infrastructure, a commuter should be able to match or better peak hour car average speeds.

We'll just have to disagree, then :) . Personally I think that the average cyclist isn't capable of sustaining an average of over 28km/h for the long term, and only a very small percentage of them use e-bikes (based on my observations on the road and path, anyway).
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Re: The War on the Roads - TV - Sunday night

Postby human909 » Mon Sep 02, 2013 8:47 pm

il padrone wrote:C of G is hardly a major issue with braking for road bikes (racers, city bikes or e-bikes). It only becomes an issue if you are likely to go OTB - mostly for off-road MTB riding. For normal street riding the question of braking distance is mainly to do with brake power (get better brakes), traction and skidding (get better tyres and be careful in the wet) or simple recognition time.

Having a high or lower CofG doesn't influence your stopping distance, only the point at which you are likely to go OTB in an emergency brake stop. For an e-bike this may actually be less likely as they have quite a bit of extra weight in rear-mounted batteries and for some a rear-mounted wheel motor, all of which will keep the rear wheel on the ground more.

I disagree on racers and most city bikes C of G is the certainly the limitting issue of braking on asphalt. I'm a little unsure why you would suggest that OTB is mainly off road MTB biking, this is the case where tyre choice and surface makes a bigger difference. In the dry you will not manage to achieve front wheel skidding during straight line braking. http://en.wikipedia.org/wiki/Bicycle_an ... cs#Braking

A CoG further back certainly does influence stopping distance as you can brake harder before you reach the OTB limit. But yes ebikes will likely have better stopping distances due to rear weight.

zero wrote:Road bike rider on the drops who has good technique should be able to outbrake the flatbar.

How do you figure that? As far as I can see a road bike has a C.G. further forward than a flat bar.
Last edited by human909 on Mon Sep 02, 2013 9:09 pm, edited 1 time in total.
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Re: The War on the Roads - TV - Sunday night

Postby Duck! » Mon Sep 02, 2013 9:03 pm

human909 wrote:
il padrone wrote:C of G is hardly a major issue with braking for road bikes (racers, city bikes or e-bikes). It only becomes an issue if you are likely to go OTB - mostly for off-road MTB riding. For normal street riding the question of braking distance is mainly to do with brake power (get better brakes), traction and skidding (get better tyres and be careful in the wet) or simple recognition time.

Having a high or lower CofG doesn't influence your stopping distance, only the point at which you are likely to go OTB in an emergency brake stop. For an e-bike this may actually be less likely as they have quite a bit of extra weight in rear-mounted batteries and for some a rear-mounted wheel motor, all of which will keep the rear wheel on the ground more.

I disagree on racers and most city bikes C of G is the certainly the limitting issue of braking on asphalt. I'm a little unsure why you would suggest that OTB is mainly off road MTB biking, this is the case where tyre choice and surface makes a bigger difference. In the dry you will not manage to achieve front wheel skidding during straight line braking. http://en.wikipedia.org/wiki/Bicycle_an ... cs#Braking

zero wrote:Road bike rider on the drops who has good technique should be able to outbrake the flatbar.

How do you figure that? As far as I can see a road bike has a C.G. further forward than a flat bar.

I'd hazard a guess that although a road bike's CoG is further forward than a flat-bars, it's also lower. Total mass being equal, the closer the CoG is to the fulcrum (front contact point), the more brake power is required to generate sufficient leverage to cause an OTB.
I had a thought, but it got run over as it crossed my mind.
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Re: The War on the Roads - TV - Sunday night

Postby human909 » Mon Sep 02, 2013 9:07 pm

Duck! wrote:I'd hazard a guess that although a road bike's CoG is further forward than a flat-bars, it's also lower.

True. This is why I mentioned earlier that I measure the angle to the CoG on road bike vs flat. Although road bikes is slightly lower it is alot further forward hence a smaller angle off vertical.

Duck! wrote:Total mass being equal, the closer the CoG is to the fulcrum (front contact point), the more brake power is required to generate sufficient leverage to cause an OTB.

I think what you meant to say was the angle of the CoG to the fulcrum?

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Re: The War on the Roads - TV - Sunday night

Postby Duck! » Mon Sep 02, 2013 9:11 pm

human909 wrote:I think what you meant to say was the angle of the CoG to the fulcrum?

That too. Angle and distance both play a part. A short lever will require more force to achieve a given result than a long lever on the same angle.
I had a thought, but it got run over as it crossed my mind.
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Re: The War on the Roads - TV - Sunday night

Postby human909 » Mon Sep 02, 2013 9:24 pm

No, the angle and only the angle determines the extent of braking where the OTB will initiate. Read the link posted earlier.
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Re: The War on the Roads - TV - Sunday night

Postby Nobody » Tue Sep 03, 2013 8:52 am

human909 wrote:No, the angle and only the angle determines the extent of braking where the OTB will initiate. Read the link posted earlier.
This is the answer.

The main contributing factors limiting getting your weight back are the center to front length (BB to front hub) and the handlebar position horizontally relative to the front hub. Maximum braking can only be achieved with the cranks (almost) level and the body pushed back behind the saddle. If the center to front is short and the handlebars are horizontally close to the front hub, then there is only so far you can push back. Road bikes are made for going fast, not stopping fast. For those that don't believe, I suggest you find a good piece of road, mark it and try some stopping distances with various bikes.
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Re: The War on the Roads - TV - Sunday night

Postby stanevelyn » Tue Sep 03, 2013 11:47 am

Here is something to think about in this topic.....

Fernando Alonso is set to acquire the world tour racing licence for team Euskaltel Euskadi. He has been a long time fan of cycling. Fancy that, a two time world formula 1 champion supporting a professional world tour cycling team. A racing car driver !!!! Kinda makes Mark Skaife look pretty small and insignificant regarding his ill informed public comments on cycling doesn't it.

Reference for this post is todays SBS Cycling Central Website.
Last edited by stanevelyn on Tue Sep 03, 2013 12:08 pm, edited 1 time in total.
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Re: The War on the Roads - TV - Sunday night

Postby Slvr32gtr » Tue Sep 03, 2013 11:52 am

stanevelyn wrote:Here is something to think about in this topic.....

Fernando Alonso is set to acquire the world tour racing licence for team Euskaltel Euskadi. He has been a long time fan of cycling. Fancy that, a two time world formula 1 champion supporting a professional world tour cycling team. A racing car driver !!!! Kinda makes Mark Skaife look pretty small and insignificant regarding his ill informed public comments on cycling doesn't it.


Thats pretty awesome!!

Mark Webber has always been a big advocator of cycling as well. He has his adventure race down in Tassie that he sponsors every year.

In fact it was a lady in her car hitting him while he was out on his bike that broke his leg and took him out of F1 for a little while...
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