Slowing for repetitive roundabouts - what's best?

[GTstar]

My commute takes me through lots of roundabouts that are connected by 70/50/40 mph roads plus loads more in town (if anyone is from aberdeen and goes north to inverurie you'll know what I mean!)

What I want to know is what is best for looking after my brake wear? Obviously you need to adjust your speed to conditions and other traffic but I'm talking about the perfect conditions.

So if you have 3 roundabouts one after the other, 20'C dry day, on a 70mph road how would you brake? 100 yards short and firm, 300 yard progressive and long or ?

Is braking for a short period of time but hard better than braking for a greater distance but with less force?

[blueg33]

GTstar said:

My commute takes me through lots of roundabouts that are connected by 70/50/40 mph roads plus loads more in town (if anyone is from aberdeen and goes north to inverurie you'll know what I mean!)

What I want to know is what is best for looking after my brake wear? Obviously you need to adjust your speed to conditions and other traffic but I'm talking about the perfect conditions.

So if you have 3 roundabouts one after the other, 20'C dry day, on a 70mph road how would you brake? 100 yards short and firm, 300 yard progressive and long or ?

Is braking for a short period of time but hard better than braking for a greater distance but with less force?

Audi were impressed with the mileage I got from my last set of discs. If I am not out on a hoon, I would take my foot off the throttle about 300 yrds out and brake progressivly but gently. depending on, vis angles and radius of the roundabout, I may not brake at all

[cheadle hulme]

Depends on the distances between RABs. Probably in gear but no throttle from around 300m or so and then brake to fine tune the speed for the last 50m.
My Fabia is on its original disks and pads @ 52k

[blueg33]

cheadle hulme said:

Depends on the distances between RABs. Probably in gear but no throttle from around 300m or so and then brake to fine tune the speed for the last 50m.
My Fabia is on its original disks and pads @ 52k

We pretty much agree I think. A6 disks only lasted 49k miles, but it is a bit heavier.

[davepoth]

If it's 2nd exit every time, why are you braking?

[7db]

If it's 2nd exit every time, why are you steering?



StressedDave has a video on the MK roundabouts which should show you what to do

[Cecil]

Don't slow for roundabouts, your going too fast, or your car does not go round corners properly

Edited by Cecil on Wednesday 30th September 22:41

[BertBert]

Why are you worried about rate of brake pad wear?
Bert

[Phisp]

The IAM will advocate the use of acceleration sense in this situation i.e. slow the car by reducing/relieving pressure on the accelerator pedal. Not by braking or changing down (to use increased engine braking from lower gears). At least, this is how I understand it from my IAM course. This technique also falls under the remit of "eco-driving" i.e. it will extend the life of your brake pads/discs and be more fuel efficient.

It's certainly a smooth technique and has it's place, but also a damn boring way to drive. Also, it's not ideal if you have anyone following - unless you don't mind fustrating the hell out of them . Edit to add that I believe the IAM would consider the use of brakes in that scenario as acceptable, since it is more courteous to those following.

Edited by Phisp on Thursday 1st October 11:16

[AndyAudi]

GTstar said:

(if anyone is from aberdeen and goes north to inverurie you'll know what I mean!)

This is also my route home, knowing this setup I can understand you question entirely.

Re the comments on not slowing down and not steering
This section of road was all built together as a by-pass for several small towns.
The roundabouts construction demands you slow down (they are, in my opinion, too large a radius)

http://www.multimap.com/maps/?qs=kintore&countryCode=GB#map=57.20097,-2.28088

Edited by AndyAudi on Thursday 1st October 11:33

[p1esk]

Phisp said:

The IAM will advocate the use of acceleration sense in this situation i.e. slow the car by reducing/relieving pressure on the accelerator pedal. Not by braking or changing down (to use increased engine braking from lower gears). At least, this is how I understand it from my IAM course. This technique also falls under the remit of "eco-driving" i.e. it will extend the life of your brake pads/discs and be more fuel efficient.

Good evans, you'd better not go advocating that sort of stuff on ADUK. It gets me in no end of trouble.

Best wishes all,
Dave.

[GTstar]

Thanks for the replies guys...

As for why do I care - well I don't really. I have a company car so I don't even pay for the maintanence (sp?) so I shouldn't really be bothered.

But part of me likes looking after the car and unlike my G/F i like to be as gentle (while driving at a er, 'efficient pace') on the mechanicals as much as possible.

Plus the amount of brake dust of my wheels is a bugger to clean! Do new-ish (17000 mile 09 bmw) brakes give off more brake dust than bedded in ones?

Sorry for spelling, I'm tired!

Edited by GTstar on Thursday 1st October 18:58

[technogogo]

AndyAudi said:

GTstar said:

(if anyone is from aberdeen and goes north to inverurie you'll know what I mean!)

This is also my route home, knowing this setup I can understand you question entirely.

Re the comments on not slowing down and not steering
This section of road was all built together as a by-pass for several small towns.
The roundabouts construction demands you slow down (they are, in my opinion, too large a radius)

http://www.multimap.com/maps/?qs=kintore&countryCode=GB#map=57.20097,-2.28088

Edited by AndyAudi on Thursday 1st October 11:33

I know of plenty of roundabouts in my neck of the woods (Poole Dorset) that are too small. As a result drivers often come onto them far too quickly and drivers coming on from the less busy joining roads end up giving way to cars 50 yards away from the roundabout. Which can be frustrating as having to slow down for an oversized, but probably deliberately so, roundabout.

Interesting original question about short sharp vs long gentle braking. I guess from a physics point of view, if you brake longer and more gently, you are giving more time for the 'free' braking forces (rolling resistance, engine braking and air resistance) to contribute. So longer more gentle braking must be less wearing on the brakes.

[Z.B]

Phisp said:

The IAM will advocate the use of acceleration sense in this situation i.e. slow the car by reducing/relieving pressure on the accelerator pedal.

Not likely from 70 mph.

Coming of the gas earlier means less wear as more of the car's energy is lost by other means than braking. The firmness of the braking itself shouldn't make much difference (unless you cook them).

[flemke]

GTstar said:

Is braking for a short period of time but hard better than braking for a greater distance but with less force?

Yes.

[waremark]

flemke said:

GTstar said:

Is braking for a short period of time but hard better than braking for a greater distance but with less force?

Yes.

So you are saying you use less brake material losing the same amount of speed with firm braking than with gentle braking? Can you expand?

[davepoth]

waremark said:

flemke said:

GTstar said:

Is braking for a short period of time but hard better than braking for a greater distance but with less force?

Yes.

So you are saying you use less brake material losing the same amount of speed with firm braking than with gentle braking? Can you expand?

It's almost certainly worse from a safety point of view, and I think excess pad wear would only be a problem if it was sustained hard braking. Assuming wear for effort is constant for any temperature (which it isn't) there would be no difference. If braking is not constant for any temperature a short prod would I think not allow the brakes to get to temperature, which would mean that more brake pad would be used for a given brake effort.

Gentle braking gives more margin for safety (if you need to brake harder you can), less chance of locking up the front wheels, less stress through the drivetrain and a better experience for the driver.

[BertBert]

That's why I was asking about the motive for minimising brake pad wear. I am not sure it's the right optimisation parameter. Optimising for safety or comfort or progress seem more interesting to me.
Bert