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18 Apr 2009, 21:15 (Ref:2444060) | #1 | ||
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Handbrakes on Newer Cars
Been hearing a lot recently about handbrake failures on some new cars- stories involving cars parked with handbrake on mysteriously rolling down the road. Has anyone here had such an experience? Anyone able to shed any light on these stories?
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18 Apr 2009, 21:52 (Ref:2444082) | #2 | |
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Never heard the stories! Are they cars with cable or electronic hand brakes?
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18 Apr 2009, 21:55 (Ref:2444084) | #3 | ||
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Some cars have electric handbrakes that could fail. Its normally cars that have discs on the back with the handbrake that work the rear calipers that give problems. If its not applied hard enough, when the disc cools down it contracts and the pads loose their grip. Drum brakes on the other hand grip tighter as they cool. The best configuration if you have discs all round is the disc with the drum inside, but for the majority of normal road cars the good old front disc with rear drums work a treat.
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19 Apr 2009, 07:41 (Ref:2444374) | #4 | ||
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Hmm, the cooling and contracting thing with disk brakes makes sense, seems to me that's a basic design problem!
Not driven anything with an electronic handbrake, don't think I'd trust that at all!! I'm surprised MOT allows that! |
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19 Apr 2009, 07:47 (Ref:2444381) | #5 | |||
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http://www.consumeractiongroup.co.uk...e-failure.html |
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19 Apr 2009, 08:07 (Ref:2444407) | #6 | ||
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19 Apr 2009, 11:07 (Ref:2444564) | #7 | ||
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The Renault one uses a couple of electric motors in the rear calipers, others like the Audi use a servo motor to apply the brake via a cable.
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
19 Apr 2009, 15:39 (Ref:2444792) | #8 | ||
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20 Apr 2009, 01:17 (Ref:2445094) | #9 | |
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Arent you suppose to have the car in gear before you get out of it ?
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20 Apr 2009, 02:38 (Ref:2445128) | #10 | |||
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But a friend of mine I caught up with on the weekend always leaves his (manual) car in neutral, and uses the handbrake to make sure it doesnt run away His logic seems to be that there is no risk of trying to start the car in gear and hitting the car in front... as opposed to a handbrake releasing the 2.5t of 4x4 and rolling into the car in front.... |
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20 Apr 2009, 04:10 (Ref:2445169) | #11 | ||
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20 Apr 2009, 09:48 (Ref:2445307) | #12 | ||
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I find I always leave the car in gear if I park. Usually 1st but if I'm on a steep "down" slope I would leave it in reverse? Any logic to my thinking?
Also bit OT but if you ever are driving through water (ford... or drift as we call it in south africa...) Dont park up and pull the handbrake and leave it for a few days. This happens to many hikers where the brakes will seize and takes some fiddling and knocking and mcguyvering to get the handbrake to release again... Or it could just be that the car loves the outdoors so much it doesnt want to leave |
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20 Apr 2009, 11:24 (Ref:2445392) | #13 | ||
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If the car is pointing downhill then leave it in a forwards gear. If it is pointing uphill then leave it in reverse.
The reason being that if the hill turns the engine, it will at least turn it forwards which is much less likely to cause belts or chains to jump, wrecking the timing and destroying the engine when you next start it. If you parking up for a long period of time (e.g. on holiday or storing over the winter) then leave it in gear with the handbrake disengaged to avoid it seizing on. |
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21 Apr 2009, 00:07 (Ref:2445939) | #14 | |||
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21 Apr 2009, 08:39 (Ref:2446130) | #15 | |
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Not me personally, but we were staying at my parents last year. Parents drive is on a slope, and Dad had parked his MX5 on the drive [08 reg]. Called out to Dad that he really needed to improve his parking, because his car was blocking the path and half the road, and had he really meant to leave it like that because really couldn't believe it was intentional - he thought I was joking, but then he looked out and realised it had rolled off the drive into the road and we all checked the handbrake which was definitely on. Not had an issue since, but he always now leaves it in gear as well!
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21 Apr 2009, 09:59 (Ref:2446183) | #16 | ||
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The reverse gear reverses the direction of rotation so it does not matter if the car is in reverse or 1st. Moving the car while in gear will still turn the engine the same way.
The gear ratio in reverse might be higher than first. That means that it requires a higher force to rotate the engine against the compression. I used to autotest a road car when a poor student and would hardly ever use the handbrake other than to execute a turn! always left the car in gear. takes a lot of effort in 1st to move the car against engine compression. even on a 998 cc mini. |
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21 Apr 2009, 10:17 (Ref:2446199) | #17 | |||
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progress? bah humbug... |
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21 Apr 2009, 11:03 (Ref:2446219) | #18 | |||
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You are correct that you want a numerically high gear to increase the torque required to turn the engine. |
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21 Apr 2009, 13:38 (Ref:2446319) | #19 | ||
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tristancliffe, you are exactly correct in what you say as regards turning the engine the wrong way. Some of the auto cam belt adjusters will slacken the belt off and sometimes will jump the sprockets when trying to start the next time.
Also while I am waffling on, I had a customer that parked an automatic (in park) that was hit from behind that broke something in the auto transmission that cost a fortune to repair ! As for what the thread is all about I can't for the life of me see why they have to complicate things, as you can't really improve on a reliable decent lever and linkage design IMHO. Is it because the human race is getting weaker and can't pull the handbrake on hard enough or car designers running out of ideas ? |
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
21 Apr 2009, 14:28 (Ref:2446342) | #20 | |
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This may seem a little off topic but just so you can laugh at me I will tell you a little story.
I once took a wrong turning into a very steep single track lane, about 100 yards up the lane I came to a locked gate so at this point I decided I had definitely taken a wrong turn. As I had gone past a spot where I could turn around about 30 yards back I reversed down the slope with my foot on the brake and turned into the 'slot' to turm around. I'm sure by now you have guessed that the engine wasn't running and the car was still in 2nd gear, whoops. I am happy to say that when I turned the key eveything came back to life and the car did another 30k miles before I sold it but when I first realised what I'd done I was, to say the least, concerned. |
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27 Apr 2009, 09:08 (Ref:2450480) | #21 | |||
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27 Apr 2009, 17:45 (Ref:2450881) | #22 | ||
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Back on topic, I was at a wedding over the weekend where one of the guests handbrake failed outside the church, more or less came off in his hand. It was a Saab 93, 2 years old. |
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28 Apr 2009, 12:29 (Ref:2451545) | #23 | ||
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
28 Apr 2009, 12:34 (Ref:2451552) | #24 | ||
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the thing with handbrakes on new cars over here is if they had to get the cars to go through an rego inspection/MOT they wouldnt pass. The rules are the vehicle must be able to be held by the handbrake only. Now how many new cars do you know that would be able to do that?
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28 Apr 2009, 20:40 (Ref:2451819) | #25 | ||
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Most "new" cars handbrakes work very well and will hold on a "steepish" gradient but only if they are serviced properly. The main problem with poor handbrakes (assuming they are designed correctly) is the auto adjusting mechanism on the pads or shoes not working as it should or seized up so the leverage points are all wrong. Cowboy mechanics adjusting handbrake cables don't help this, and I would like a quid for everytime that I've slackened a cable off and let the adjusters work and BINGO. The UK MOT standards only require 16% on dual circuit brakes and 25% on single circuits and can differ from side to side as long as they reach the required % together. However after saying all that some handbrakes are rubbish compared to others and have a job to "scrape" through a test even when everthing is renewed.
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
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