The friendly "dumb" bike questions thread

The friendly "dumb" bike questions thread

Author
Discussion

horsemeatscandal

1,241 posts

105 months

Friday 25th June 2021
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Turns out I'm a much more efficient packer than I thought. I've also managed to fold the top of the rucksack over so it's not catching my helmet, it's basically just a big, normal rucksack now. Who needs a GS...


Gibonz

48 posts

68 months

Friday 2nd July 2021
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How dangerous are manholes covers or wet manholes covers in corners?

Recommended tactics for dealing with them when they cant be avoided?


Cheers

Jazoli

9,103 posts

251 months

Friday 2nd July 2021
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Gibonz said:
How dangerous are manholes covers or wet manholes covers in corners?

Recommended tactics for dealing with them when they cant be avoided?


Cheers
They are slippery, best case is be as upright as possible relax and do nothing, you pass over them in a fraction of a second at speed, if you have to brake then the abs will deal with the locked wheel, if you don't have abs don't touch the brakes.

Gibonz

48 posts

68 months

Friday 2nd July 2021
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Jazoli said:
They are slippery, best case is be as upright as possible relax and do nothing, you pass over them in a fraction of a second at speed, if you have to brake then the abs will deal with the locked wheel, if you don't have abs don't touch the brakes.
Thanks!

Gibonz

48 posts

68 months

Wednesday 7th July 2021
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When a bike doesnt have ABS, and when performing hard braking/emergency stops, why does the front wheel not lock up?

snagzie

453 posts

61 months

Wednesday 7th July 2021
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Gibonz said:
When a bike doesnt have ABS, and when performing hard braking/emergency stops, why does the front wheel not lock up?
Because the tyre still has grip.

ABS only kicks in when the tyre loses grip, then quickly pulses the brake on and off to try and recover the grip

RizzoTheRat

25,191 posts

193 months

Wednesday 7th July 2021
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Because it has enough grip. ABS becomes more useful in wet and slippery conditions where you can lock the wheel up a lot more easily.

Krikkit

26,538 posts

182 months

Thursday 8th July 2021
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Gibonz said:
When a bike doesnt have ABS, and when performing hard braking/emergency stops, why does the front wheel not lock up?
It will if you brake hard enough/suddenly enough, depends what you're doing.

Most of the time the brakes are applied slowly enough that the weight transfer squashes the front tyre and increases the available grip massively.

SpeckledJim

31,608 posts

254 months

Thursday 8th July 2021
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Krikkit said:
Gibonz said:
When a bike doesnt have ABS, and when performing hard braking/emergency stops, why does the front wheel not lock up?
It will if you brake hard enough/suddenly enough, depends what you're doing.

Most of the time the brakes are applied slowly enough that the weight transfer squashes the front tyre and increases the available grip massively.
This. There's a positive cycle where the harder you brake, the more braking capability the front tyre has. Up to a point...

And the reverse on the back, so if you're braking hard at the front, go steady with the back brake. The extra weight at the front, resulting in extra braking grip at the front, is being 'borrowed' from the rear tyre, which is getting lighter and lighter the harder you brake.


tvrolet

4,277 posts

283 months

Thursday 8th July 2021
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anonymous said:
[redacted]
Unless it's wet or slippery, it's exactly the opposite for most folks - even in an emergency. Many just don't realise just how hard you can BRAKE; it's difficult to learn unless you have ABS and pull to the max to see when it kicks in, or without ABS get ready to release the BRAKE as soon as it locks before landing on your ear. Quite a few cars now have some sort of emergency BRAKE assist, where if the car thinks you're braking hard it actually applies more pressure because what the driver thinks is 'braking hard' actually isn't.

Biker 1

7,741 posts

120 months

Friday 9th July 2021
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I did a massive involuntary stoppie on a non ABS bike some years ago. I went to overtake an old dear, who decided to turn right at the very last moment - no indicators.... How I avoided going over the bars I have no idea!
I am now a fan of ABS - I have tried braking from 60mph as hard as possible. It is astonishing how quickly you can come to a halt, particularly with decent rubber, nice new pads & a fluid change!

RizzoTheRat

25,191 posts

193 months

Friday 9th July 2021
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I was at the MCN show at Peterborough years ago, and BMW were doing test rides on F650GS, with Simon Pavey instructing. Not many people showing up so we had a pretty long session with him , one of things was getting us to lock the front (on grass), and hold it as long as possible. It's amazing how long you can keep the bike upright with the front locked before you need to release it and straighten up. I can see why a lot people say learning some offroad skills is good for your road riding.

SpeckledJim

31,608 posts

254 months

Friday 9th July 2021
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RizzoTheRat said:
I was at the MCN show at Peterborough years ago, and BMW were doing test rides on F650GS, with Simon Pavey instructing. Not many people showing up so we had a pretty long session with him , one of things was getting us to lock the front (on grass), and hold it as long as possible. It's amazing how long you can keep the bike upright with the front locked before you need to release it and straighten up. I can see why a lot people say learning some offroad skills is good for your road riding.
I can imagine it is. In a similar vein, how some scrambler experience as a junior is useful for top-level track racing. For example Casey Stoner.

KTMsm

26,901 posts

264 months

Friday 9th July 2021
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Krikkit said:
Gibonz said:
When a bike doesnt have ABS, and when performing hard braking/emergency stops, why does the front wheel not lock up?
It will if you brake hard enough/suddenly enough, depends what you're doing.

Most of the time the brakes are applied slowly enough that the weight transfer squashes the front tyre and increases the available grip massively.
Yes - the only time you are likely to need ABS is in an emergency.

I had an old git pull out on me with no warning - I grabbed the brakes and locked the front - I'm unsure whether I released because it locked or whether I had braked enough by then but either way I'd slowed enough and stayed upright - it's the only time I've locked the front


black-k1

11,936 posts

230 months

Friday 9th July 2021
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anonymous said:
[redacted]
Not all non-ABS bikes will lift the rear before the front locks. Short wheelbase sports bikes will but longer wheelbase bikes will lock the front wheel in the dry, on a good surface, before the rear lifts off the ground.

Some of the training I have done included finding a quiet section of road with a good, flat surface, then braking from about 40mph hard enough to lock the front wheel. This was on a non-ABS bike. The front wheel slide was "controlled" enough to allow a quick release of the brake. It showed just how much braking was actually available if/when it was needed in an emergency.



TheInternet

4,722 posts

164 months

Friday 9th July 2021
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anonymous said:
[redacted]
Is the risk of lifting the back wheel not an issue with ABS? It is something I've wondered despite never coming close to doing it. I was under the impression that some bikes can detect rear lifting, but thought that others will allow you to go straight over the handlebars if you try hard enough, but I've no idea how hard that is to do.

ETA: The post above suggests you can reach maximum braking on some bikes without flipping.

Prof Prolapse

16,160 posts

191 months

Friday 9th July 2021
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I would have thought, maximum front braking would only come about if the weight shifted massively to the front, i.e. rear wheel light, or even off the ground.

Assuming you had enough grip of course.



SpeckledJim

31,608 posts

254 months

Friday 9th July 2021
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Prof Prolapse said:
I would have thought, maximum front braking would only come about if the weight shifted massively to the front, i.e. rear wheel light, or even off the ground.

Assuming you had enough grip of course.
Guessing now, but maybe among the plethora of sensors on an ABS-equipped bike is something on the swing-arm that knows when full extension is reached.

If the goal of ABS is maximum breaking without losing the ability to steer, then when it knows the rear wheel is unweighted, it backs off the front braking pressure a tad, to allow the rider to retain directional authority?

ETA: just realised I said 'retain directional authority' when I should have said 'steer'.

What a divvy.


Edited by SpeckledJim on Friday 9th July 12:37

Krikkit

26,538 posts

182 months

Friday 9th July 2021
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If you've got a modern enough ABS system (i.e. with a proper IMU) it'll be able to detect when the rear wheel comes off the deck and, if coded for, allow it to reach a particular height off the deck before reducing front braking.

RizzoTheRat

25,191 posts

193 months

Friday 9th July 2021
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Surely ABS should be able to detect if the rear wheel has lifted without additional sensors. ABS would detect the rear wheel has locked, release the brake, and then if the wheel's lifted it wouldn't spin back up to the same speed as the front wheel.