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gargamel Samba Member
Joined: December 20, 2011 Posts: 693 Location: Orange Grove, Texas
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Posted: Wed Oct 29, 2014 10:01 am Post subject: |
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Lots of good info. This could easily be the most info I have read on the obscure Z-bar. |
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Aussiebug Samba Member
Joined: June 03, 2002 Posts: 2162 Location: Adelaide Australia
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Posted: Wed Oct 29, 2014 7:16 pm Post subject: |
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Q-Dog wrote: |
But what do I know? A week ago I thought this thread was about how to fix a car with a dented roof. |
Yes Brian, it did sort of morph from top of car to bottom of car. But that's how is goes - start talking about bugs and you could end up anywhere.
I started a conversation with a guy a few months ago (81 1600 Bus) and now he's going to take my wife and I around Mumbai (Bombay) next year. Friends all over the world - that's the power of old aircooled VWs. _________________ Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com |
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neil68 Samba Member
Joined: March 17, 2007 Posts: 3440 Location: Calgary, Canada
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Posted: Wed Oct 29, 2014 7:37 pm Post subject: Z-bar Beetles |
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Aussiebug wrote: |
Slow 1200 wrote: |
by the way the Z-bar was used all the way to 2003 in non-IRS Beetles |
Yep - the Brit Haynes manual indicates that - the version I quoted from includes cars up to 75. In the UK it was the "GT" models which had the Z bar. We didn't get that particular description in Aus.
In 1968 we had 1300 manuals, 1500 manuals (Z bar) and 1500 semi-autos (IRS) (1500 models had OEM disc brakes)
In 1969 we had exactly the same.
In 1970 we had exactly the same. (only the USA got 1600s in 1970).
In 1971 we had 1600 superbugs (front disc brakes on both manuals and semi-autos) and 1300 standard bugs (manuals with drum brakes).
Many small differences in model description and specs in different parts of the world. |
In Canada, we had swingaxle "standard" Beetles, with Z-bars & 21mm torsion bars, up into the mid-70's. IRS was also available and was more common. The third choice was the Super Beetle, with struts & IRS. All three models had four-wheel drum brakes and 1600 cc (from '69 onward). _________________ Neil.
Der Kleiner Rennwagens
68 Beetle 2332 cc, 204 WHP
12.5 seconds @ 107 mph
Dynojet Test: https://www.youtube.com/watch?v=M9B_H3eklAo |
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ensys Samba Member
Joined: March 11, 2009 Posts: 322 Location: America's Automobile Heartland
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Posted: Wed Oct 29, 2014 8:58 pm Post subject: |
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Mr.Aussiebug:
Your attitude is worthy of a measure of respect. I’ve enjoyed this discussion of suspension science.
I don’t know when true Z-bars first came on the scene, but as swing axles have been with us since the ‘30s, I suspect it was some time before the VWs poorly-named camber compensator. But then, this from the people that called a recent four-door sedan a “phaeton”, so I’m not surprised.
Yes, negative camber makes sense on both ends of a race car, so it is no surprise that the FV shown (it was the only foto that clearly showed a Z bar installation, making its operation easier to visualize) is so turned out. The beauty of a Z bar on the street is that it can be set neutral at any ride height/camber one chooses. The same is true for the virtual Z bar. For those, like myself, that cannot resist fiddling to taste, both can also be pre-loaded (with appropriate compensation to suspension springing to allow the desired ride height) to the same criteria.
Its probably a different discussion (of opinions), but since you brought it up, I will note that I am no fan of anything more than a quarter degree of neg. camber on any corner of a street car, as more induces all manner of unseemly behavior, particularly on today’s tires. And conversely, I abhor the all too frequent use of positive camber to induce understeer on production cars, but since the Nader debacle, the Prime Directive of auto manufacturers has been “Its ALWAYS better to go off the road nose first”. In fact, this is the Second Reason that the world is now full of front-drivers. But now I really digress.
Mr.Modoc:
I sense you’re very close to getting it. All that stands in the way, I think, is the impression that part of the true Z bar’s role is as a spring; get past that and you’re home free.
Mr.Jonnypan:
It would seem that you remain confused about more than descriptive terms. Apparently it is “rocket science” to some folks.
The VW’s Z-shaped camber compensator does not operate anything like the true Z bar, and for swing axeled cars, less rear roll is not “safer”.
At the risk of sounding presumptuous, I suggest you put out of your mind everything you think you know about this subject and re-read the entire thread. If you don’t want to take our word for things and clarity still eludes you, do some research. That’s what Google is for. I have found that there is a fellow on ShopTalk that has a fair grip on this stuff, and maybe a different source would be more illuminating.
On that note, and if there are no further good questions, I will withdraw, as it would seem that we have covered the necessary basics pretty well, and I have never been a fan of flogging dead horses.
Its been fun, as all gentlemanly discussions are meant to be. _________________ Keep 'em flying...
S.J.Szabo |
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modok Samba Member
Joined: October 30, 2009 Posts: 26743 Location: Colorado Springs
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Posted: Wed Oct 29, 2014 9:25 pm Post subject: |
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I must object to the idea the amount of preload matters to it's operation, unless one is non-linear rate (which probably aren't),
A bar, a single leaf, are very basic shape spring and will be linear rate.
If this bar with the adjustable links claims the pre-load adjusts something more than ride height.........it might be baloney.
If it is springy, then it is a spring. if it wasn't then it's be a bump stop
The main purpose of the pre-load would be to prevent the joints rattling.
the VW one just kicks in at the top and bottom of travel, so it is both an overload spring, and an "underload spring"..............the underload aspect being most important to prevent tuck under braking and satisfy the Nader lynch mob. |
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Aussiebug Samba Member
Joined: June 03, 2002 Posts: 2162 Location: Adelaide Australia
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Posted: Thu Oct 30, 2014 3:25 am Post subject: |
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modok wrote: |
the VW one just kicks in at the top and bottom of travel, so it is both an overload spring, and an "underload spring"..............the underload aspect being most important to prevent tuck under braking and satisfy the Nader lynch mob. |
I have not actually measured the spring plate travel downwards in relation to the Z bar, but as I said in one of my posts above, I think you'll find that by the time the wheels have moved down enough for the sliding links to bottom out and start twisting the bar as an "underload" spring, the spring plates will be sitting on their stop lips anyway and the downwards movement of the wheels will stop at that point.
In other words, I don't think it does much for the downwards movement of the wheels (together or one at a time), and is almost exclusively a "one way" spring - the sliding links means it really only works with the wheels moving upwards, not downwards.
I'll have to get out my camera next time I have to reset the sagging rear end on my 70 1500 Aussie/Euro spec bug with Z bar, and see if the spring plates hit their stops before the sliding links bottom out. _________________ Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com |
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Stuart Maingot Samba Member
Joined: December 13, 2009 Posts: 240 Location: Trinidad West Indies
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Posted: Thu Oct 30, 2014 9:29 am Post subject: |
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My 69 with Z-bar is on jack stands presently. The spring plates are bottomed out on the torsion housing stop point and there is no load on the z-bar. This would mean the z-bar does not prevent or limit downward wheel travel.
This entire thread has been an interesting discussion. |
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Gerrelt Samba Member
Joined: December 22, 2004 Posts: 682 Location: The Netherlands
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Posted: Thu Oct 30, 2014 10:00 am Post subject: |
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Somebody should put a small camera under his car, and film what it is doing. The car should have the Z-bar (of course) and be at standard hight.
Then take some corners at various speeds, both left and right ones.
A bit like this video I made, but then with a swingaxle-Z-bar-equiped car..
I think that would clarify a lot. _________________ homepage
_________________ |
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modok Samba Member
Joined: October 30, 2009 Posts: 26743 Location: Colorado Springs
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Posted: Thu Oct 30, 2014 6:21 pm Post subject: |
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Stuart Maingot wrote: |
My 69 with Z-bar is on jack stands presently. The spring plates are bottomed out on the torsion housing stop point and there is no load on the z-bar. This would mean the z-bar does not prevent or limit downward wheel travel.
This entire thread has been an interesting discussion. |
That could be true! Is it supposed to be like that? I have no idea.
In either case, the factory z-bar seems to be..... well.......lets just say that it can be improved upon. |
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Stuart Maingot Samba Member
Joined: December 13, 2009 Posts: 240 Location: Trinidad West Indies
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Posted: Thu Oct 30, 2014 9:21 pm Post subject: |
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Yes, thats exactly how it is supposed to work as it is solely a third torsion bar that comes into effect under a certain suspension load. Now i had said b4 that i used additional rubber buffers under the original ones to effectively bring the action of the zbar in with less suspension load. The result is a stiffer suspension. Now one could also try mounting rubber buffers at the bottom of the rods where it passes through the bracket with the hole bolted to the axle tube and this may limit suspension downward travel somewhat and possibly provide some action as a camber compensator? |
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Aussiebug Samba Member
Joined: June 03, 2002 Posts: 2162 Location: Adelaide Australia
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Posted: Thu Oct 30, 2014 9:56 pm Post subject: |
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Stuart Maingot wrote: |
My 69 with Z-bar is on jack stands presently. The spring plates are bottomed out on the torsion housing stop point and there is no load on the z-bar. This would mean the z-bar does not prevent or limit downward wheel travel.
This entire thread has been an interesting discussion. |
Thanks Stuart,
That's what I thought, but wasn't willing to commit to it without putting my car up on jack stands.
So it's exactly what I've been saying all along, an overload spring and nothing more than that (no underload component, and no roll component). And that's exactly what the manuals describe as well.
But re your question on being a camber compensator when you "pack" the sliding links. It can't have any effect there until the arm on one side hits the packed down top bump stop and the arm on the other hits the packed up bottom of the sliding link on that side, so you'd have to pack it to almost "fixed" (more like the formula V Z bar in the pics above), to have any significant effect as a camber compensator, and then it might change the balance with the front stabiliser bar. _________________ Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com |
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Stuart Maingot Samba Member
Joined: December 13, 2009 Posts: 240 Location: Trinidad West Indies
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Posted: Fri Oct 31, 2014 6:56 am Post subject: |
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Understood. It is what it is and should be used for what it was design for. It works just fine for me with the road conditions over here. |
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iancorado Samba Member
Joined: February 23, 2014 Posts: 24 Location: North Wilkesboro
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Posted: Mon Nov 03, 2014 10:15 am Post subject: New body is on the pan |
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So I have the body from the 65 on the 68 pan. I picked up the 65 for $300. I always knew the rear body mount was different for IRS cars but I found out last night that all 68 and newer pans have different rear body mounts to 67 and older. Pictures are on the way. I plan on pulling as many parts as possible from the 68 and then try to sell just the body.
Last edited by iancorado on Mon Nov 03, 2014 11:08 am; edited 2 times in total |
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iancorado Samba Member
Joined: February 23, 2014 Posts: 24 Location: North Wilkesboro
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Posted: Mon Nov 03, 2014 11:06 am Post subject: 65 body on 68 pan |
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iancorado Samba Member
Joined: February 23, 2014 Posts: 24 Location: North Wilkesboro
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Posted: Wed Apr 01, 2015 4:32 pm Post subject: |
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Not pretty but functional |
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iancorado Samba Member
Joined: February 23, 2014 Posts: 24 Location: North Wilkesboro
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Posted: Sun Feb 04, 2018 9:32 am Post subject: Re: Non z-bar early body on 68 swing-axle pan with z-bar |
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