Anyone here ever actually lose the back on a swing axle car? - PeachParts Mercedes-Benz Forum

Marrs · #1 09-01-2015, 06:20 PM

"Be careful pushing it on curves with that swing axle" is perhaps repeated often enough that you would think we are driving around in Porsche 911s. I drive with spirit but certainly nowhere near the car's limits, but for those of you who are a bit more fearless, have any of you ever lost the back end in a curve or avoidance maneuver, and what exactly happened if you did?

Even in rain I have never felt like I was going beyond the car's capabilities.

97 SL320 · #2 09-01-2015, 07:24 PM

Decades ago I had a 64 190 fin tail but didn't recall much ill behavior but the bias ply tires gave up pretty easily.

These cars have a low pivot swing axle that holds off the jacking effect a bit longer when cornering hard than high pivot. Just as with the 911 ( tail heavy with much mass hanging rearward of the rear wheels) , the stubborn Germans made the best of a bad situation with low pivot.

A VW bug has a high pivot and will tuck the outside wheel under then trip the car. It goes something like this. Car enters right hand corner, body leans left, inside right wheel droops going into positive camber, swing axle pivot rises, outside left wheel starts to lose camber and goes positive. Now the the tire contact patch is much lower than the axle pivot point, cornering forces jack the rear of the car up, sometimes rapidly. This results in a snap loss of traction and the tail comes around. ( there are probably some graphics / vids on the net to explain visually .)

I have a 88 Ford Ranger mini truck with a " twin I beam " front suspension ( more or less swing axle with the left axle pivot on the right side and Vs V ) . This was Fords answer to independent front suspension over a solid axle.. . . in 1965. . .

The truck will corner pretty well for what it is but when pushed hard, I can feel the front suspension get stiffer and the nose rise. At this point it just under steers / plows forward bleeding speed.

Stretch · #3 09-02-2015, 03:13 AM

I once had an old Morris Marina (1.8 super!) that had a rigid rear axle set up. Under normal driving it was absolutely fine. It was so under powered that to do anything really stupid was actually quite difficult...

...however one time whilst taking "evasive action" I got the rear end to get close to a skip and a jump (it was a real 5p => 50p moment)

Marrs · #4 09-02-2015, 01:31 PM

97 SL320: Thanks, that is extremely interesting to me, I appreciate the tutorial! Never fully understood the mechanics vs physics of it all until now.

Stretch: I like your thinking, sometimes low power keeps you out of trouble in the first place!

Tony H · #5 09-02-2015, 04:59 PM

I had a 250S(108) while stationed in Germany that I drove VERY fast through windy roads with no hint of trouble. At that time I was uneducated about the swing axle issues so I never even knew.

gmog220d · #6 09-02-2015, 06:04 PM

Look towards the ends of these videos to see some old Benzes put through their paces:

https://www.youtube.com/watch?v=Pbag0dVTLbM
https://www.youtube.com/watch?v=LO10OzJPC3U

Couldn't find it but I've seen a video of an old Heckflosse romping through a slalom. Seems the old swing axle cars do alright in curves.

Tony H · #7 09-02-2015, 11:23 PM

It seems the center spring would contribute to positive camber and the jacking action since it is trying to push the rear axle halves apart but I think it somehow is supposed to control it.

Jub · #8 09-03-2015, 07:33 AM

I guess you can tow things with this type of axle, but according to CC these were problematic and were done away with:

Cohort Outtake: Towing Fintail Might Get Towed

gmog220d · #9 09-03-2015, 09:49 AM

RE: Cohort Outtake:

The old swing axle rear end was replaced in the W114/W115 chassis, introduced for 1968.

JMela · #10 09-03-2015, 10:05 AM

Anyone recall the name of that 70's movie, (clip was posted here a couple of years ago), that had a nice red 108 zooming around a parking garage and smashing into things? Some good swing axle hooning in that one, IIRC.

gmog220d · #11 09-03-2015, 06:28 PM

Quote:

Originally Posted by JMela

Anyone recall the name of that 70's movie, (clip was posted here a couple of years ago), that had a nice red 108 zooming around a parking garage and smashing into things? Some good swing axle hooning in that one, IIRC.

Don't know the title. The YouTube user (timothy mayer) who posted that movie took it down a while back. The driver is a "hot" driver guy the bad guys are checking out for a job. Smashing their Benz up in the garage was his way of showing them he was a good driver. At least that's how I remember it.

POS · #12 09-03-2015, 08:00 PM

Dad's 1971 280SL could easily get sideways with some speed and some slaloms. 'Twas fun!

97 SL320 · #13 09-03-2015, 09:16 PM

Have a look on the Internet Movie Car Database web site, it shows lots of cars and movies.

berfinroy · #14 09-03-2015, 10:39 PM

Its only the old high pivot swing axels that could lead to some disasterous handling issues, especially in high performance cars that were more likely to be driven in a spirited fashion. Like the 300SL Gullwing Mercedes. You really had to know what you were doing to drive those cars hard through the turns.
That changed with the first roadster versions of the 300SL starting in 1958, while the other more mundane sedans continued with the old style axel for some years to come. I'm not sure when all Mercedes cars switched over to low pivot design, but I'm thinking 1965 with the introduction of the 108 chassis.
Any comments on which Mercedes cars were the last ones to use the old high pivot axel design?

68_280SE · #15 09-04-2015, 07:22 AM

The first mercedes cars to use the low pivot swing axle were the W180 and W120 sedans around 1955. Most of their models followed suit including the 190SL, the 300SL roadster, the heckflosse/fintail sedans and coupes, the W100 grosser, the W113 roadsters, and the W108/W109 sedans. The W108/W109 models were the last mercdes benz cars to have the low pivot swing axles, with exception of the W100 which was made in small numbers for the rest of the world up until about 1980. Mercedes introduced a trailing arm rear suspension with the introduction of the W114/W115 models in 1968. This system was used with some slight modifications on the W107/W116/W123/W126 models right up through the last W126 in 1991.