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 Post subject: group N saloon circuit racing GTi toe in / out settings
PostPosted: Mon May 08, 2017 9:03 pm 
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Joined: Mon May 08, 2017 8:45 pm
Posts: 9
Location: London
Ive just bought a Group N standard production spec circuit racing 1989 Swift Gti mk2.

I've done one race and need some advice on suspension settings to get the handling spot on regards toe and caster.

Its got 3 degrees negative camber front struts (fixed height/fixed camber built into the struts)
Running Yokohama A048 semi slick 14 inch 185/60/14 tyres

I've had it on a Hunter 4 wheel alignment machine

Front - caster is 2 degrees
Front - Toe is - 0.1 (measured -0.05 on each side)

Rear camber - - 1 degree
Rear Toe is +0.33 on each side measures total +1 degree Toe (positive).

I've driven it once and it feels quite neutral but the front feels quite numb.

What settings have people used on circuit racing?


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Tue May 09, 2017 3:38 am 
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Joined: Mon Aug 25, 2003 12:00 am
Posts: 1526
Location: Londoninium
Neutral is good! Was it quick?
Did it suit your driving style or preferences. What was the rear doing? How long is a piece of string!
25 years or playing with swifts has led me to prefer more front toe out. Zero rear toe. Very stiff bushes especially in the rear and less flex rear toe arms and/or arm bushes
What do your tyres tell you about your camber. This will be dependant on the track and tyre combo.
What tyres, what dampers, how low and stiff?
I like progressive lift off oversteer.
GTP


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Wed May 10, 2017 9:39 am 
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Joined: Mon May 08, 2017 8:45 pm
Posts: 9
Location: London
Thanks for your reply, 25 years of Swifts? I could do with some of that expertise if you dont mind?

First racing car I've had with adjustable rear suspension and I am interested to know what changes to rear and front toe do to handling.

The car was slow and I'd say easy to drive but felt numb, 3 seconds a lap slower than my last car at Castle Combe (at 750 motor club stock hatch saxo), it feels like its not turning in positively.

It's been set up by the previous owner, rock hard rear springs, GAZ shocks, standard bushes, AWD model ARB on rear. Fairly high ride height, not slammed to the ground.

The tyres are Yoko Ao48 and they are a worn set of my old car so no way to see what wear I am getting after just 20 laps on the Swift, have got a new set ordered.

The question is, what do with toe and castor to make it turn in a bit sharper and be a bit more tail happy on corner entry? I will play around with tyre pressures as this makes the biggest difference but need to get a good base setting on the suspension.


gtpswift wrote:
Neutral is good! Was it quick?
Did it suit your driving style or preferences. What was the rear doing? How long is a piece of string!
25 years or playing with swifts has led me to prefer more front toe out. Zero rear toe. Very stiff bushes especially in the rear and less flex rear toe arms and/or arm bushes
What do your tyres tell you about your camber. This will be dependant on the track and tyre combo.
What tyres, what dampers, how low and stiff?
I like progressive lift off oversteer.
GTP


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Wed May 10, 2017 10:21 am 
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Joined: Sat Feb 05, 2005 6:51 pm
Posts: 1763
Location: Chch - Quake Capital
You say you have camber fixed on the front struts, does that mean you still have the OEM front strut tops in there??? being Grp N you weren't allowed to change some of those things but solid front strut tops, lower control arm brace and solid rear toe bars make a massive difference to the handling and can drop your lap times by several seconds easily.

Btw I'd be dialing in 2mm of toe out on each corner to help the tyres grip up earlier in the corner.

Best thing you can do is break down the corner into 3 parts to describe how the car feels, turning into the corner, mid corner and exiting the corner, makes it easier to figure out whats going on.


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Thu May 11, 2017 5:35 pm 
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Joined: Mon May 08, 2017 8:45 pm
Posts: 9
Location: London
Dattman wrote:
You say you have camber fixed on the front struts, does that mean you still have the OEM front strut tops in there??? being Grp N you weren't allowed to change some of those things but solid front strut tops, lower control arm brace and solid rear toe bars make a massive difference to the handling and can drop your lap times by several seconds easily.

Btw I'd be dialing in 2mm of toe out on each corner to help the tyres grip up earlier in the corner.

Best thing you can do is break down the corner into 3 parts to describe how the car feels, turning into the corner, mid corner and exiting the corner, makes it easier to figure out whats going on.


Hi, yes standard OEM front strut tops (the struts have the camber built into them as per stock hatch 750 mc spec).

Where would I find lower control arm brace, solid rear toe bars and solid strut tops and what are these doing to the handling to make such an improvement to laptimes? Is it just reducing flex/movement in the suspension set up?


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Thu May 11, 2017 6:10 pm 
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Joined: Sat Feb 05, 2005 6:51 pm
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Location: Chch - Quake Capital
No wonder it feels mushy, get rid of all rubber ASAP, those rubber mounted strut tops flex so much that mid corner your supposedly 3" neg camber is about 2 pos.
Also OEM strut tops are incredibly bad for your shocks, you need a pillow ball at the top to allow for articulation, with the rubber tops it bends the shock piston shaft and prevents nice smooth travel.
I cannot stress how much difference solid strut tops with pillowball/spherical bearing will make.

As for a braces, not sure if Turbine tech still make them but you get the idea.
http://www.turbinetech.ca/component/tie ... 35?lang=en

You can see my 6 point brace here
viewtopic.php?f=3&t=55021

Before my brace I used to pull the left hand driveshaft out of the box under breaking for our hairpin, mines a very late model low km version so it's not a soggy worn out chassis, just runs very low and with slicks on generates a lot of force, obviously enough force to spread the lower control arms apart enough to partially pull the shaft out of the box and leak oil everywhere... lap times dropped almost a full second with that brace.

Rear toe bars are easy, 14" tubular bars from any speedway shop and 1/2" rod ends or 12mm equivalent, make sure you get left and right threads so adjusting the toe is easy.
These ones are bit too heavy but have nice rubber booties to make the rod ends last a bit longer.
http://www.ebay.co.uk/itm/1989-02-Geo-M ... Swm8VUwusp


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Thu May 11, 2017 6:55 pm 
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Joined: Mon May 08, 2017 8:45 pm
Posts: 9
Location: London
Thanks some good info there thanks Dattman the photo of your cars underside is amazing like new!

The car I have bought has been a racing Swift Gti all its life with just one owner since 1989, I just picked it up and its still in standard group N spec, its only done 9,000 miles since new and has not been used as a road car, quite an amazing find.

I am racing it in an open series so my plan is to sort the handling out, get a bit more power, add an lsd, do a few more races and see if it can be made into a class winner without going too much further.


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Thu May 11, 2017 9:48 pm 
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Joined: Sat Feb 05, 2005 6:51 pm
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Location: Chch - Quake Capital
Unfortunately the rebuild of my car its taking longer than expected, was expecting to miss two seasons at the most but now it's probably going to be four :(

I'd be keen to see some pictures of your car, if its a period complete group N car then I'd suggest to stick with your plan and not stuff around with it too much and keep it as original as possible, genuine Gti's are beginning to get rare in some parts of the world.


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Tue Jun 13, 2017 11:22 pm 
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Joined: Mon May 08, 2017 8:45 pm
Posts: 9
Location: London
thanks for replies, what I am trying to understand is

Will more toe in on the rear make it turn in sharper, or does it need more toe out to make it turn in sharper?

thanks


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 Post subject: Re: group N saloon circuit racing GTi toe in / out settings
PostPosted: Wed Jun 14, 2017 7:28 am 
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Joined: Mon Aug 25, 2003 12:00 am
Posts: 3493
Location: Brisbane
toe out on the rear will make it turn in sharper, 1 or 2mm out per side should be enough,if you go too far it will make the rear of car step out as you turn in, which for circuit racing is fine/quick if you have quick reflexes.

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