[AlanHo]

Now that we live on a retirement complex our garage is one in a block of 8 identical garages.

I have noticed that my KIA Venga will roll out of the garage as soon as the handbrake is released, whereas my previous i30 Tourer needed the engine running to get it to roll out.

This morning, being curious, I checked the slope on the garage floor and found that it was 45mm lower at the doorway than it was at the far end 5.8 metres away. My neighbour spotted me checking the fall with a water gauge and asked what I was doing. We got chatting and he said his 2 year old VW Golf would not roll out of the garage without power. Whilst we were comparing notes another neighbour came by in his 3 week old Vauxhall Mokka and joined in the conversation. To cut a long story short we finished up trying each car in my garage but mine was the only one that would roll out with gravity - the Golf and Mokka, like my previous i30 both needed engine power or a hefty push to get them started.

The Golf has Michelin Energy Saver tyres. Front tyres at 32 psi. Rear tyres at 31 psi
The Mokka has Goodyear Eagle Eco tyres. All tyres at 34 psi
The Venga has Continental Eco Contact 3 tyres. All tyres at 36 psi
My previous i30 had Dunlop Sport BluResponse tyres. All tyres at 36 psi.

Now that I have finished the experiment - I haven't a clue what to do with the information - other than to share it with you guys.......................

[Shambles]

Great anecdote

Just  goes to show, that extra few psi reduces the amount of rubber contacting the surface, getting you closer to that 'pizza cutter' profile

[AlanHo]

Ah - but my i30 had 36 psi tyres and that didn't roll. 

[Shambles]

Ah - but my i30 had 36 psi tyres and that didn't roll. 

But that was a proper car.

Like yourself, I don't know where I'm going with this 

[AlanHo]

And here was me thinking we would be on a roll

[eye30]

It is due to the position if the engine in the car.

Assuming the cars are driven front in then:

If the engine's heavier part is nearer the bulkhead than the other cars  then the weight is nearer to the centre of the car or in other words nearer to the rear of the car or the garage door and thus the weight and slope downwards causes the car to move under its own weight.

My simple logic is applied

[AlanHo]

I don't think you are quite on the level with that theory. The slope of the garage floor is constant from front to back.  In other words the floor is a flat plane tilted by 40 mm at one end.

WHERE ARE YOU GONZ...................

[eye30]

Did you drive in forward or reverse in?

Whichever you did try it by placing the car(s) in the oppposite and see what happens.

  I'm still of the opinion it is to do with the engine weight and position in the engine compartment

[AlanHo]

Just to humour you I have tried reversing the car into the garage - and the result is just the same. Release the hand brake and it rolls out.

It's a good job I have a reversing camera - the amount of stuff I have stored in the garage made reversing a tad risky.  And before you ask - I am not going to ask the neighbour to reverse his car in. The poor old chap would never do it.

But there's more...

My friend with the Mokka made a suggestion this afternoon. Let's go to his club for a wee dram (he's a Scot) and conduct an experiment.

The driveway from the road to the clubhouse is several hundred yards of smooth tarmac and on a very slight slope. We lined both cars up at the top of the drive and released the handbrakes simultaneously. Both cars started rolling but within approx. 50 yards my Venga was a good car's length in the lead. The lead increased steadily and because there is a 20 mph limit on the drive I was soon having to gently brake. I reached the clubhouse a good 10 seconds before Dave and he told me that he didn't have to use his brakes until he was parking.

There is thus no doubt that my Venga is more free running than his car.

It was a good talking point while we enjoyed a snifter. I've got him worried now that he has a disc caliper dragging.

[Phil №❶]

Did you take your dB meter with you

[tla]

Now you need to exchange the tyres between the cars to prove/disprove that the tyres are the cause of the unassisted rolling.

BTW: which car is heavier?

I can imagine your wives discussing whose husband is the strangest.

[Dazzler]

And here was me thinking we would be on a roll

Lucky I read every post (you stole my line!) 

I reckon it is a combination of the tyres and the rest of the drive line. My Hybrid is amazing how far it will run without any accelerator applied! For the record it has MIchelin Primacy LC tyres on it.

[eye30]

Just to humour you I have tried reversing the car into the garage - and the result is just the same. Release the hand brake and it rolls out.

It's a good job I have a reversing camera - the amount of stuff I have stored in the garage made reversing a tad risky.  And before you ask - I am not going to ask the neighbour to reverse his car in. The poor old chap would never do it.

But there's more...

My friend with the Mokka made a suggestion this afternoon. Let's go to his club for a wee dram (he's a Scot) and conduct an experiment.

The driveway from the road to the clubhouse is several hundred yards of smooth tarmac and on a very slight slope. We lined both cars up at the top of the drive and released the handbrakes simultaneously. Both cars started rolling but within approx. 50 yards my Venga was a good car's length in the lead. The lead increased steadily and because there is a 20 mph limit on the drive I was soon having to gently brake. I reached the clubhouse a good 10 seconds before Dave and he told me that he didn't have to use his brakes until he was parking.

There is thus no doubt that my Venga is more free running than his car.

It was a good talking point while we enjoyed a snifter. I've got him worried now that he has a disc caliper dragging.

defo to do with the weight of the cars or the occupants

[TheReaper]

Im sure that when you are leaving your garage that you are reversing out of it. But with some of the new cars made nowadays. They have Hill Start Assist (HSA). Not sure if it works in reverse as well. But being on a flat surface is enough to activate it to give it a little juice. from what I read a while back. Because my golf loves to roll back, and I researched it back then thinking it was a problem

[Doggie 1]

Did you take your dB meter with you

Leave me out of this. 

Alan, you seem to have a bit of spare time on your hands? 

[Phil №❶]

What a wonderful story Alan,

Meanwhile, inside Alan's house, Mrs Ho was serving tea and cake to the other two wives. One of the wives looked out the window and saw Alan's car rolling out of his garage. This interested her, so continuing to watch, as Alan placed his water slope gauge on his garage floor she noticed her husband and the other neighbour's husband come to see what Alan was doing,,,,,,,,,


Who wants to add the next installment

[The Gonz]

WHERE ARE YOU GONZ...................

Don't get me started - next someone will suggest 'funny cars' with their tiny front wheels go faster because they naturally roll downhill!

Stay tuned for news of a new perpetual motion patent!

On a more constructive note, yes the entire drivetrain from tread to clutchplate will influence rolling resistance. BTW, my tyres run at 41 PSI.

[AlanHo]

On a more constructive note, yes the entire drivetrain from tread to clutchplate will influence rolling resistance. BTW, my tyres run at 41 PSI.

I would run if some burk tried to put 41 psi in me.................

[Asterix]

Well, my i30 also start rolling out the carport as soon as the handbrake is released and clutch depressed. 

The floor in my carport falls with 55 mm over 5 meters.

At some point the car wouldn't roll out, and I found out is was the handbrake not releasing completely. Handbrake dismantled and re-greased, and it would roll out again..

[Phil №❶]

Our car doesn't roll at all. 


The floor is level, though.

[The Gonz]

 

[AlanHo]

Did you take your dB meter with you

My meter is a Db08 model - it sometimes gets the wrong readings of situations and creates most of the noise itself. It has a mind of its own and some find it distinctly aggravating. 

[John B]

I reckon some have got rear disc for the handbrake and others have got brake drums and they are adjusted up differently , I suggest you and your mates strip all of your brakes and investigate further ,also if there is a wind tunnel nearby check wind resistants, try the i30 with the mirrors folded in and note the results. Check how many balancing weights are on the wheels . Did one driver test all cars or did you all test your own car ,maybe driver weight also had something to do with it.Yes I know what a load of  rubbish , oh that's a point what weight is in the cargo areas ? 

[John B]

What a wonderful story Alan,

Meanwhile, inside Alan's house, Mrs Ho was serving tea and cake to the other two wives. One of the wives looked out the window and saw Alan's car rolling out of his garage. This interested her, so continuing to watch, as Alan placed his water slope gauge on his garage floor she noticed her husband and the other neighbour's husband come to see what Alan was doing,,,,,,,,,


Who wants to add the next installment

Calling the other wives one of them said just look at those three all on their knees and at this time of morning.

[Doggie 1]

Did you take your dB meter with you

My meter is a Db08 model - it sometimes gets the wrong readings of situations and creates most of the noise itself. It has a mind of its own and some find it distinctly aggravating. 

       

[The Gonz]

What a wonderful story Alan,

Meanwhile, inside Alan's house, Mrs Ho was serving tea and cake to the other two wives. One of the wives looked out the window and saw Alan's car rolling out of his garage. This interested her, so continuing to watch, as Alan placed his water slope gauge on his garage floor she noticed her husband and the other neighbour's husband come to see what Alan was doing,,,,,,,,,


Who wants to add the next installment

Calling the other wives one of them said just look at those three all on their knees and at this time of morning.

Within seconds, a cleric was heard singing from a nearby minaret. "Ah", they all said in unison, "this is the UK after all!"

[ausi30]

Too much science content above. It is quite simply a matter of the angle of the tongue and how much is hanging out of the mouth. Problem solved.