unstable fd after 125mph/200kmh
 

hey guys.

drove my car 620miles/1000km this weekend and noticed that my fd3s got unstable/twichty after passing 125mph/200kmh and was wondering if there are some improvents to help get it more stable at those speeds.

the only things i have done to it is putting on a set of wheels from a mazda 6 2015 with 225/45/19 tyres, everything else is stock, did a wheel aligment before i went on the trip and there is no play or annything in the suspention.

Are you using the economy tyres from the mazda 6?

No, have a set of toyo proxyes

if properly aligned/balance the FD is solid as a rock at 165. generally high speed sloppiness is fixed w a proper toe setting. if you had your car aligned please share the settings. aero is not a significant factor at 125. see my suspension settings in my Suspension setup thread sticky in the Suspension Section for proper settings.

https://cimg0.ibsrv.net/gimg/www.rx7...efb1d50d1d.jpg
Heres the aligment.
the front caster wouldnt go center so i adjusted it as equal as possible

it needs more caster, and more negative camber on the front. rear looks ok, although if it was mine and i had the rack for a long time, i would get the akselvinkel to 0

How old are your bushes, shocks and springs?

Double check that everything is tight. I redid my entire suspension and it seemed to be a little flighty up front over 100 mph. Thought it was the 99 wing i just installed pushing the front end up, but turned out to be one of my steering rack bolts was so loose it was about to fall out.

Your running a 27" tire on stock suspension and bushings, I'm sure it would feel unstable. As mentioned a solid alignment, having a look through Howard's thread (Worth the read for anyone in general even outside of owning a FD), suspension check/upgrade and throwing on wheels closer to 25" will help out.

I've had mine well past 125mph and no twitchyness, and I have no rear wing too before that suggestion comes up.

Agreed. Shoot for -1.5* camber and 5-6* caster

Those tolerances are too loose for a well aligned car. More for a normal car.
Fine a place that does track quality alignments.

If your shocks are going soft, that would lead to problems.

Did the aligment my self, im just a regular Mazda tech so i toght it was fine, have adjusted since then and it made the diffrence.
The cars fine now, but since the speedo only goes to 180kmh how fast but im guessing 250kmh its fine

I'm kinda interested in pictures of the FD on the new Mazda 6 wheels. Care to give us a peek?

Ye
https://cimg1.ibsrv.net/gimg/www.rx7...b7316cd538.jpg
Yea No problem.
Ride hight is a bit high tho