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What makes Z Cars suspension so good.


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#1 Jammy

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Posted 10 September 2006 - 07:33 PM

I've been thinking after looking at a picture of the new A series Z Cars tubular frame. That has the shox inboard, pointing down at about 45 degrees, with a right angle pivot translating the upward motion of the hub into the angle of the shock. I was thinking, does the suspension work so well because any upward motion is ultimately transferred into downward motion into the shock, so it sort of cancels each other out? I've never read a book on suspension or anything, so forgive me if this is pretty much all bs! :w00t:

Another part of my brain is telling me its all to do with the angles of tie-bars, double wishbones, etc!

#2 minimadjonesy

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Posted 10 September 2006 - 09:25 PM

I believe it works perfectly well, a similar system is used for the ABS Freestyle (funbuggies) that a number of people on here are on about building!

Where did you see the frame? was looking myself on line but cannot find it on their site, woudl very much like to see how much they are as it would allow for the fitment of a flipfront without brace bars I believe

Edited by minimadjonesy, 10 September 2006 - 09:26 PM.


#3 Jammy

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Posted 11 September 2006 - 09:12 AM

This is one design -

Posted Image

But this is the one I was thinking of -
Linky

#4 miniboo

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Posted 11 September 2006 - 09:23 AM

i heard that that is the best setup.

no bumpsteer or anything with that one.

AND it can fit an a series engine in it.

think they are about a grand arent they?

#5 R1mini

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Posted 11 September 2006 - 09:37 AM

i heard that that is the best setup.

no bumpsteer or anything with that one.

AND it can fit an a series engine in it.

think they are about a grand arent they?



The geometry is the same no matter where the coilovers are mounted, as for no bumpsteer we shall see

£700 if you buy it with a bike engined kit, a £1000 if you buy it outright, if you buy the VTEC kit it's part of the price but it can change at any time and often does

I have one of these front subframes, I would get the outboard shocks if I could buy again, the shocks behind the tank push the the tank forward and very very close to the radiator, I'm struggling to even get a fan in there

Cheers
David

#6 Jammy

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Posted 11 September 2006 - 09:47 AM

Judging by your comment about the position of the coilovers not really making a difference, does this mean the decent handling is mainly down to the wishbones and stuff?

Hmmm, think I may have to by myself a book on suspension design!

Or if anyone has any links?

#7 Alburglar

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Posted 11 September 2006 - 11:03 AM

There's an old book called how to build a race car. it covers things like this I will find it asap

There's an old book called 'how to build a race car' or something I saw it in halfords I think. it covers things like this I will find it asap...
...found this tho - Crikey
http://www.amazon.co...o/dp/0760302839

#8 Jammy

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Posted 11 September 2006 - 11:10 AM

Cheers Ali, think I'll give that particular book a miss though, as much as I want to learn about suspension and chassis building, I don't want it to cost me £130! :w00t:

#9 Alburglar

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Posted 11 September 2006 - 11:18 AM

This is the daddy. I'vegota load of speedpro books from my veedub days.
http://www.amazon.co...2714244?ie=UTF8

This is the old publication Iwas on about
http://www.amazon.co...d=2E14CPE38C6L4

#10 Dick Dastardly

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Posted 11 September 2006 - 05:42 PM

How in-depth do you want to get? Suspension systems can be a pretty complex subject.

Very generally speaking a good suspension setup (at the front , at least) is apparently one which offers no bump-steer, has controlled camber gain, has no ackerman angle on the steering, allows about 6 degrees of positive castor, has good ant-dive characteristics, offers a low roll centre height, and has properly matched spring/damper rates. It's 95 percent about geometry and understanding how all the external forces have an effect on the ideal static condition.

A good book on the subject: "Advanced Race Car Suspension Development" by Steve Smith. Published by Steve Smith Autosports Publications.

It baffles the hell out of me though.....

#11 R1minimagic

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Posted 21 October 2006 - 09:20 AM

I don't think there is such a thing as 'no bump steer' on a mini. It all comes down to the pivot points of the suspension vs the steering and on a mini they are not that well matched, especially if you lower the car a lot. All you can do is try and minimise the effects, which is typically by relocating the track rod end location. This is what the miglia racers do as they are lowered so much that the track rod end is pointing up quite a bit at the hub end. They also relocate the tie bar for better castor control.

If you read Bill Sollis's book on mini race car setup he went to great lengths to minimise bump steer. After driving the car round the race track, he could feel no improvement over the previous setup and in fact preferred the feel with the original setup!! This is probably not that surprising as on a race track you don't have a lot of bumps anyway! On the road it might be a different story, but each car is different in ride height and suspension settings so you cant say 'fit one of these and you will have no bumpsteer'.

Bill also drove the z cars mini (tubular front subframe) around Rockingham (?) and, if I recall correctly, reported that he couldn't feel any improvement/difference over a normal mini front subframe setup.

On my car, the first thing i noticed on turning into a bend at low speed (10-15mph) was very vague steering feel, not sharp at all, totally different to the way it felt before. However, at higher speed (70mph) turn in felt good and predictable, which was more reassuring! Chris said that they had experimented with quick racks which improved the low speed turn in feel but felt more twitchy at higher speeds. I found a big improvement in the way the car stays in a straight line under full power, very stable with almost no steering corrections/input required.

I think the main reason for the improved feel on the road (which I haven't experienced, just going off what others have said) is that everything is better located and stronger than the original setup so there is less flexing etc. The tie rods are also now on the top suspension arm, rather than the bottom (which are also double rose jointed), which possibly helps on bumpy roads with more favourable angles?

Edited by R1minimagic, 21 October 2006 - 09:30 AM.





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