AuthorTopic: A frame nightmares.  (Read 810 times)

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Offline Tommo

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A frame nightmares.
« on: March 01, 2008, 23:01:15 »
went to pick up a 5 series beemer with a blown headgasket today, stuck the a frame on to the bottom arms as usual, went to drive off and which ever way you turned the beemers wheels went full lock the opposite way, with some rather interesting concequeces lol.

Ended up just driving it with no water in, lasted about 25 mins till it lost oil pressure, then lasted another 15 with the big ends knocking there nuts off, after that it was very hard to drive because it only ran above about 3k rpm (some very interesting heel/toe braking going on at traffic lights trying to keep it going) then we hooked up a rigid towing bar (kindly supplyed by corrosive rob as a backup) after managing to find a proper tow hitch.

So has anyone got any idea what went wrong with the A frame??? towed a pug 406 estate with it before and towed me 90 back from mansfield on the motorway and everything ( [-X) with no issues.
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Offline Disco Matt

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Re: A frame nightmares.
« Reply #1 on: March 01, 2008, 23:11:08 »
I can only assume it was something to do with the steering on the BMW - A frames work as the steering will follow the direction the car is being towed in (why you can't reverse with them - the wheels will tend to turn to one lock or the other!).

BMWs are all RWD, while your 90 and the 406 would have driveshafts going to the front wheels. I wonder if that had something to do with it?
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Offline fudge

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Re: A frame nightmares.
« Reply #2 on: March 01, 2008, 23:18:20 »
Isn't it something to do with weather the tie rods are in front of or behind the hub, and if they are in front of the hub the car won't tow behind a dolly?

Offline Tommo

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Re: A frame nightmares.
« Reply #3 on: March 01, 2008, 23:22:25 »
even then i think they are still behind the hub. but any car with castor (ie all cars surely) should always wint to return to centre and should never just flip on to one lock or another whilst being pulled forward.
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Offline Disco Matt

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Re: A frame nightmares.
« Reply #4 on: March 01, 2008, 23:22:45 »
That might well make sense - If you think about it having the tie rods behind would probably make the wheels more inclined to follow the direction of travel rather than wandering about.
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ben_haynes

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Re: A frame nightmares.
« Reply #5 on: March 02, 2008, 00:29:22 »
it is to do with the wishbone Setup (same as Merc's) (similar to the Old King Pin Suspension like on MGB's(the oldies will know what i mean) [-X )

The track rods are behind the hubs, they do have a tendancy to pull to the Drivers side (they do when put on 2 poster Ramps)

was the steering lock on? as this would have stopped this

Offline Range Rover Blues

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Re: A frame nightmares.
« Reply #6 on: March 02, 2008, 05:21:17 »
It's because BMW use a strange combination of castor, trail and scrub radius.  Look at ther wheels on a BMW when on full lock and see what I mean, they look like they have broken off they lay backwards so badly.  £ series used to have a funnt quirk that at full lock if you stamped on the gas they steering woudn't self-centre at all, they just doughnutted all day long, "look mum, no hands".

TBH I'm not a big fan of BMWs, even more so now that they are more common than a Mondeo (and I mean common) though starngely my mate loves them. 
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Offline Tommo

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Re: A frame nightmares.
« Reply #7 on: March 02, 2008, 22:44:11 »

was the steering lock on? as this would have stopped this

yeah it would have stopped it but it wouldnt be much fun when we tried to turn but carried straight on through an orphanage! lol
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ben_haynes

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Re: A frame nightmares.
« Reply #8 on: March 02, 2008, 22:48:44 »

was the steering lock on? as this would have stopped this

yeah it would have stopped it but it wouldnt be much fun when we tried to turn but carried straight on through an orphanage! lol

it would have acted like a trailer, if attached correct it would have followed the towing vehicle, That is how the AA & RAC do it

Offline Tommo

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Re: A frame nightmares.
« Reply #9 on: March 02, 2008, 23:10:00 »
really???  :?  surely you would need a heavy towing vehicle to be able to drag the front end of the car round, and it would scrub the tyres awfully. I'll look into it, must be info out there on the net.
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Offline redhand

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Re: A frame nightmares.
« Reply #10 on: March 02, 2008, 23:17:55 »
I think someone is mistaking an A frame for a dolly. you can't put the steering lock on a vehicle that'sbeen towed with an A frame. Because the front wheels have to turn in order to follow the towing vehicle. As Toomo so rightly pointed out. The first time you turned  acorner or crossed a roundabout the beemer would have tried to carry on in a straight line.
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