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Zcars Front Subframe


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#16 AllanMcD

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Posted 17 December 2009 - 06:09 PM

Chris seemed to be aware of the problem at the time, and as I said, he was experimenting with fitting quick racks.

You don't need corner weights setting up if you are only driving at 40mph, optimising corner weights improves your handling when you are driving at or close to the limits..


A quick rack wouldnt help how can that affect grip or feel ?
You don't need corner weights setting up if you are only driving at 40mph ????????????
You can be near the limit at 20mph so the car balance matters at all speeds.
Allan

#17 R1minimagic

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Posted 17 December 2009 - 06:22 PM

Yes but i was nowhere near the limit, just driving along at 40mph and turning the steering side to side like you do to warm your tyres.

I will wait for Chris to answer the question.

#18 AllanMcD

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Posted 17 December 2009 - 06:37 PM

Yes but i was nowhere near the limit, just driving along at 40mph and turning the steering side to side like you do to warm your tyres.

I will wait for Chris to answer the question.


As I have said a few times if your car is light on the front (understeer) all you have to do is lower the front or raise the rear which increases the front weight
You can only get this right by trial and error as every car differs eg tyres type commpound or size , weight of car slipper dif etc
Allan

#19 R1minimagic

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Posted 17 December 2009 - 06:43 PM

Allan, sorry but you have got the wrong take on things here, it was nothing to do with corner weights or anything like that.

As I keep saying, Chris was aware of the issue and said that fitting quickracks was helping (don't ask me why, that's just what he told me!!).

This was a few years ago just after the Z Cars front frame had been introduced so there may well be a solution now and that is what my original question was about.



Chris will no doubt be able to tell us all what it is.

#20 z cars chris

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Posted 17 December 2009 - 07:10 PM

we dont use quick racks on the cars at all ever
we tried a quick rack once and it was too quick
allans right you do have to alter ride height etc to get the best setup
luckily its all adjustable and can be set up to your preferences
if you look at the on board footage of my races you will see very little arm twirling at all the cars pretty neutral and easy to drive
if you go onto track and race cars website theres three miniutes with keith wood driving my car
he is twitching at the wheel and stabbing at the throttle quite aggressively in total contrast to the way i drive
this is a good illustration of two different drivers in the same car we were both on the same lap times just doing it in a different way
theres no actual right setup just one that the drivers happy with i can cope with mild understeer as im smooth on the way in and happy to drift the car if needs be i dont need to chuck it in and i like the front to be quite neutral
in fact since i put aero on the car its turned in a bit too fast for me so ive stiffened the front which has helped it to be more settled
each to their own
chris

#21 R1minimagic

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Posted 17 December 2009 - 07:19 PM

Thanks Chris,

So going back to the original question which was to compare standard mini front subframe to Z cars front subframe......with a Z Cars front frame do you get the same sharp mini steering feel that you get with a standard subframe (which i had and then lost after fitting the Z Cars frame)?

by the way - all geometry settings were as recommended by Z Cars after fitting new frame and corner weights re-done.

Why would fitting the Z Cars frame make such a massive difference to the steering feel?

Have you since changed the geometry of the frame as alluded to by Richard earlier?

#22 z cars chris

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Posted 18 December 2009 - 10:42 PM

dale you had one of the first front subframes we did
on those the rack was still fastened to the bulkhead of the shell and not the subframe itself
i found by experimentation that the rack when mounted to the bulkhead it wasnt stiff enough and there was a moment of "take up" between the time you turned the wheel and the time the car reacted
ive also found that if the steering column isnt sufficiently braced you get a similar feel or loss of feel to the steering
this is due to the fact that the movement at the wheel rim causes the steering column to deflect to one side before having enough purchase to turn the rack itself its very common especially with a dropped column arrangement
since we started fixing the racks to the actual subframe the response is instant
when i do demos now i will have the car travelling at 50 to 60 mph and to answer queries from passengers will tell them to watch my hands on the wheel and to feel how fast the car reacts to steering inputs
i then twitch the steering quite quickly from the straight ahead to one side or the other several times so they can see how soon in relation to my hands putting the input into the wheel it takes to react
its instant
when you think about it then the steering should be instant as everythings rose jointed and the racks now part of the subframe there is nowhere for mushyness to creep in
if we used rubber bushes in there then you would get some movement
hope this helps
chris

#23 Pete649

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Posted 19 December 2009 - 10:07 AM

ive also found that if the steering column isnt sufficiently braced you get a similar feel or loss of feel to the steering
this is due to the fact that the movement at the wheel rim causes the steering column to deflect to one side before having enough purchase to turn the rack itself its very common especially with a dropped column arrangement


Chris, would you suggest that the standard fixings for the steering column could do with reinforcing as a general rule when the rack is fixed to the bulkhead?

#24 R1minimagic

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Posted 19 December 2009 - 12:21 PM

Chris,

I think you now understand what I am talking about!!

Your explanation makes a lot of sense and I think with my car I was also using slicks so it may have magnified the extent of the problem even further.

I sold the car during the summer so it's not an issue for me any more, I just wanted to know what the solution was, but it sounds like you have cracked it!

Cheers
Dale




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