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Re: even better handling?
[Re: Kelv27]
#719241
02/12/2008 18:02
02/12/2008 18:02
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suba
Unregistered
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suba
Unregistered
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Yep that would do the job fine.
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Re: even better handling?
[Re: Trappy]
#719260
02/12/2008 18:22
02/12/2008 18:22
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suba
Unregistered
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suba
Unregistered
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You really need to speak to Julian at BMS rather than me to explain all this - I've pretty much given him a free reign with a brief consisting of 'just make it corner well without it behaving like a pig in a straight line.' Here's my dumbed down version. 1. if you lower the car there are two things to think about: A: The roll center - http://en.wikipedia.org/wiki/Roll_centerB: The wishbone angle The coupe is already a lowered Tipo with suspension that was not engineered with cornering prowess in mind - lowering it much further makes the wishbones point upwards, when you get lateral forces on the wishbones you then get excess movement in the suspension, which changes the roll center. (if you have a car with soft suspension what happens to the outside front when you lob it into a corner? - all the weight goes onto that tyre, and the car will loose grip with only one tyre doing the work.) Think about pushing a ruler into a wall with it at a right angle to the wall, and then doing the same thing with it at 45 degrees to the wall - then imagine the ruler is your wishbone. 2. I bloody well hope so! the best handling set up I have had so far was Koni / Eibachs with 1.3 neg camber at the front and an uprated rear arb with the dampers set to hard all round. The car was lowered 35mm. I got annoyed with this as though the turn in was much better the car would bite hard and then noticeably transfer all the weight to the outside front wheel, so the car felt very 'turn in hard, lift off to get it pointing the right way, then back on the power.' I wanted it to be more subtle - the alternative was to add a front arb to compensate (and hope it worked) or start from scratch (I was not convinced other coilover kits on the market did the job properly), I opted for the latter. The proof is going to be in the pudding.
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Re: even better handling?
[Re: Kelv27]
#722616
06/12/2008 22:11
06/12/2008 22:11
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sediciRich
Unregistered
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sediciRich
Unregistered
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Suba, sorry for your knowledge and sorry to you julian but the idea of the roll centre being below ground is purely a static model for soft road cars. In cornering is not actually valid, and the biggest myth going when people talk about mcpherson struts. Never the less a roll centre does exist, but conidering force application points is the way to understand what will happen.
The loading or rather the rate of loading to the outside wheel will dictate greatly the handling ability of the car, and this ability is a function of roll resistance; With roll most notably being controlled by spring rate, and rate of loading by the compression damping. If your wish bones are running parallel to the ground then the cars c of g will be high, creating a greater roll moment - remember the idea of a intersecting wishbone axes is not valid i.e. dont imagine the distance of that pseudo point to the estimated C of G as truely representative of what the moment will be.
Incidentally out of all the tipo based alfas I know that race and 156's also none of them have a ride height where the wish bones would be parallel. But of course a race car is a lot stiffer then a road car and needs far less travel then a road car.
anyway carry on..
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Re: even better handling?
[Re: Nigel]
#784797
02/03/2009 00:29
02/03/2009 00:29
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Joined: Dec 2005
Posts: 8,417 Lightwater, Surrey
DaveG
Club Treasurer Member 311
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Club Treasurer Member 311
Je suis un Coupé
Joined: Dec 2005
Posts: 8,417
Lightwater, Surrey
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I'm just resurrecting this thread since I finally got around to using Nigel's gaugeI finally fitted the FK's with Bravo top mounts and Jimbo's bravo "cups" to make it all fit, and adjusted the heights to raise the front since it was too low, now I have the top/front edge of the sills at around 28cm and the top/rear edge at around 29cm (but I don't know what standard height is?)
I've measured up today simply sticking the gauge to the upper part of the front brake disc (with wheels still on), poking out through the wheel, but it was not on a level surface, will try again tomorrow in a car park, but I got this:
nearside +1.15 camber, +6.0 caster offside +1.2 camber, +6.2 caster
these seem a long away from workshop figures
camber -40' +/- 30' (or -10' to -1°10') caster 3°30' +/- 30' (or 3° to 4°)
so it will be interesting to see if the "built-in" camber adjustemnt on the FK's (slotted top bolt hole) will adjust enough to get closer...currently the adjustment is approx half way (and suprisingly similar for each side despite being such a rough adjustment)
1996 Portofino 20vt & 2000 Pearl White Plus 1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake
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Re: even better handling?
[Re: Jimbo]
#785006
02/03/2009 11:46
02/03/2009 11:46
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Joined: Dec 2005
Posts: 8,417 Lightwater, Surrey
DaveG
Club Treasurer Member 311
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Club Treasurer Member 311
Je suis un Coupé
Joined: Dec 2005
Posts: 8,417
Lightwater, Surrey
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Where's the "over my head" icon when I need it? Cheers Jimbo, will take some measurements later and I might even get time to adjust tonight. My steering wheel is so far away from centre when wheels are straight ahead it's clear I need to adjust that and check toe-in too (haven't had an alignment check for ages).
Just done some swotting up, I'll see how har I can push the axle in to the strut to get more negative camber.
I assume the extra caster comes from the fact it's lowered compared to standard?
1996 Portofino 20vt & 2000 Pearl White Plus 1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake
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Re: even better handling?
[Re: Nigel]
#785656
03/03/2009 00:59
03/03/2009 00:59
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Joined: Dec 2005
Posts: 8,417 Lightwater, Surrey
DaveG
Club Treasurer Member 311
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Club Treasurer Member 311
Je suis un Coupé
Joined: Dec 2005
Posts: 8,417
Lightwater, Surrey
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I didn't think it would fit over the hub nut, I'll have to try again,
But I measured at the works car park today and got
nearside +1.2 camber, +3.0 caster offside +1.05 camber, +3.0 caster
so tonight I removed the wheels, stuck the gauge on the brake discs, adjusted to level, then tried to reduce camber from what was indicated (about -0.7) to around -3 (I needed to reduce by 2.25 - 2.4 to get to -1.2) and I had to use up pretty much all the adjustment by pushing the hubs all the way in to the struts - now the camber looks hugely negative just looking at the car, but I'll try a run to work tomorrow and measure again.
Funny how the caster came out close to spec at 3 both sides?
1996 Portofino 20vt & 2000 Pearl White Plus 1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake
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Re: even better handling?
[Re: DaveG]
#785862
03/03/2009 11:03
03/03/2009 11:03
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Joined: Dec 2005
Posts: 8,417 Lightwater, Surrey
DaveG
Club Treasurer Member 311
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Club Treasurer Member 311
Je suis un Coupé
Joined: Dec 2005
Posts: 8,417
Lightwater, Surrey
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Measured again today after adjusting last night
nearside -0.8 camber, +2.5 caster offside -0.8 camber, +2.75 caster
Without camber bolts I'm not sure I could get any more negative, and perhaps the caster is not right because I'm not measuing it properly (on the centre of the hub) so will try again later.
1996 Portofino 20vt & 2000 Pearl White Plus 1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake
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Re: even better handling?
[Re: DaveG]
#785869
03/03/2009 11:09
03/03/2009 11:09
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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Dave, your getting this all wrong The FK are capable of running a huge amount of negative camber that will scrub the inside of your tyres off within a week so I'd be really careful. You can't measure with the car jacked up or on an uneven surface or the measurements will be totally out. I'd pay the £40 and get a proper wheel alignment done on it, it will save your tyres.
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