Janey Posted April 30, 2006 Report Share Posted April 30, 2006 After watching the 1/4 miles today & looking at what the 'serious' boys were running on, and also some of the traction problems some of them were having - I have a question Take a RWD car Put 155/70/13's on the front - Put 195/45/15's on the rear What would the effect be ? Runwise & geometry wise ? p.s I'm a girly and i am allowed to ask questions like this Quote Link to comment Share on other sites More sharing options...
Guest Gord Posted April 30, 2006 Report Share Posted April 30, 2006 After watching the 1/4 miles today & looking at what the 'serious' boys were running on, and also some of the traction problems some of them were having - I have a question Take a RWD car Put 155/70/13's on the front - Put 195/45/15's on the rear What would the effect be ? Runwise & geometry wise ? p.s I'm a girly and i am allowed to ask questions like this Are you sure Barry, has not asked you to ask for him Quote Link to comment Share on other sites More sharing options...
Tony Posted April 30, 2006 Report Share Posted April 30, 2006 After watching the 1/4 miles today & looking at what the 'serious' boys were running on, and also some of the traction problems some of them were having - I have a question Take a RWD car Put 155/70/13's on the front - Put 195/45/15's on the rear What would the effect be ? Runwise & geometry wise ? p.s I'm a girly and i am allowed to ask questions like this How felxible is the rear to accomendate geometry? Quote Link to comment Share on other sites More sharing options...
Janey Posted April 30, 2006 Author Report Share Posted April 30, 2006 Are you sure Barry, has not asked you to ask for him No this is out of my own demented brain Gord How felxible is the rear to accomendate geometry? Not sure Tony how flexible is my rear ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 30, 2006 Report Share Posted April 30, 2006 Are you sure Barry, has not asked you to ask for him No this is out of my own demented brain Gord How felxible is the rear to accomendate geometry? Not sure Tony how flexible is my rear ? No.....Bless how flexible is the rear 'geometrically' of the car in question? Quote Link to comment Share on other sites More sharing options...
Janey Posted April 30, 2006 Author Report Share Posted April 30, 2006 Are you sure Barry, has not asked you to ask for him No this is out of my own demented brain Gord How felxible is the rear to accomendate geometry? Not sure Tony how flexible is my rear ? No.....Bless how flexible is the rear 'geometrically' of the car in question? Ahh but that was the answer, we are talking about my car I have no idea how flexible it is, but I'm hoping you do Quote Link to comment Share on other sites More sharing options...
Tony Posted April 30, 2006 Report Share Posted April 30, 2006 Are you sure Barry, has not asked you to ask for him No this is out of my own demented brain Gord How felxible is the rear to accomendate geometry? Not sure Tony how flexible is my rear ? No.....Bless how flexible is the rear 'geometrically' of the car in question? Ahh but that was the answer, we are talking about my car I have no idea how flexible it is, but I'm hoping you do Stop it your making me dribble ......... Does the car in question have rear toe/camber adjusters....ask Bazza........ Quote Link to comment Share on other sites More sharing options...
Janey Posted May 1, 2006 Author Report Share Posted May 1, 2006 Stop it your making me dribble ......... Does the car in question have rear toe/camber adjusters....ask Bazza........ Yes as far as I am aware it does as I remember you tweaking them Quote Link to comment Share on other sites More sharing options...
Tony Posted May 1, 2006 Report Share Posted May 1, 2006 After watching the 1/4 miles today & looking at what the 'serious' boys were running on, and also some of the traction problems some of them were having - I have a question Take a RWD car Put 155/70/13's on the front - Put 195/45/15's on the rear What would the effect be ? Runwise & geometry wise ? p.s I'm a girly and i am allowed to ask questions like this The 195 is a very narrow target geometrically so it makes the Geometry very tight and un-forgiving. Any 1/4 mile is dependent on launch and the apllication of thrust so the first area we need to control is the 'Thrust angle' Obviously this needs to be set at 0 Next issue is camber (rear) -v- the centre of gravity -v- height, this centre is relative to the wheel base and determines load transfer between the front and rear a 40/60 on a RWD seems reasonable. Then the frames rigidity comes into play specifically the coil/sway rate... since we don't have any data relating to 'pull down' or 'weigh plates' we have to assume the car is.........40/60 and 'even' So application -v- Geometry -v- camber rear should consist of a 30' negative position and a 195mm tyre. Their is desirable conical pneumatic distortion at the tyre reducing the circumference but adding compression toward the thrust angle, actual distortion i cannot calculate (any engineers in the house) The rear toe position is reactive to the progression of the launch.... initial position should be positive 30' partial this seems reasonable, after launch the pneumatic effect plus rolling resistance should ascertain a 1/4 mile zero toe. Now to the front.... the 155mm tyre -CG has very little value during most of the 1/4... The KPI/SJI and Castor is non existent as is the camber position... my only need here would be the toe... As the front receives down force and inertia under braking there is a need to direct the traction laterally toward the tyres to support security at the steering this is done with toe in... 10' partial seems reasonable. Quote Link to comment Share on other sites More sharing options...
Janey Posted May 2, 2006 Author Report Share Posted May 2, 2006 Cool, thanks Tony Quote Link to comment Share on other sites More sharing options...
Tony Posted May 2, 2006 Report Share Posted May 2, 2006 Cool, thanks Tony Remember i was asking Bazza when i set the car what he would like from the Geometry he suggested a 50/50 road/track position..... this was music to my ears because i never had to maths any of the above Quote Link to comment Share on other sites More sharing options...
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