Front end feels light and pulls left braking at higher speeds

JohnJL · 08-10-2007, 10:36 PM

Here's a note I dropped my suspension shop today, maybe someone has a suggestion as well...text below is from an e-mail, the track I'm referring to is Eastern Creek.

Overall the car is handling very well and predictably especially in low speed corners and exceptionally well through the turns 2-5 sequence.

However it is skittish on high-speed corners. I am hitting about 205 kph (125mph) at the end of the main straight. As I get to about 190 at the middle of the paddock area it starts to feel light in the front, which is made worse with a few of those bumps on the inside line. In pictures it does look to be riding higher than I thought it normally does. A pic can be found here: http://www.jpmphoto.com.au/frame_2.htm

The other issue was also in the same area. If I apply light braking at higher speeds it pulls to the left. Now, on turn 1 that’s better than pulling right I suppose but it still isn’t right. The brakes are new OEM solid rotors and stock, rebuilt calipers. Pads are Pagid Orange. They are well-bedded in now. The same problem isn’t apparent at lower speeds, so perhaps its aero- and/or suspension-related (as in is the left side a bit softer and getting better traction?)

>>>>

For the Pelicans, the car is an 83SC with Elephant racing suspension bits all around and a Tarret through-the-body bar. Torsion bars are 28 and 32, if I recall correctly. Shocks are OEM Boge though they test out fine. The front spoiler is an RSR Narrow from MA Shaw, the rear is a Carrera "Tea Tray" i think. Car weighs 1040kgs with me in it.

Any help appreciated...maybe two things going on here? Maybe drop the ride height further or install an adjustable splitter below the spoiler? Not sure about the pulling to the left...Getting it lower would be a pain. Its already pretty tight getting it onto the trailer without scraping and my low-profile lift barely gets under the engine now.

thanks

JohnJL · 08-10-2007, 10:38 PM

Sorry, the link is well-protected so I can't attach with my meagre skills. The best illustration of the ride height at speed is on page 17 of the August 10 Drive Day, the red 911 with number 13.

dvkk · 08-11-2007, 12:48 AM

Quote:

Originally Posted by JohnJL

...... If I apply light braking at higher speeds it pulls to the left. ....

Sticking right caliper.

JohnJL · 05:22 AM

Thanks. I didnt suspect that as I had rebuilt the calipers (and honed the pistons, replaced the seals and honed the chambers) and I didnt experience any pulling in lower speed stops. I can stand on the brakes from 150-60 kph and it stops straight consistently.

Could it be sticking slightly and only exhibiting at light pressures? What's the cure given the pistons, seals and chambers should all be fresh and identically prepared?

911s55 · 08-11-2007, 05:38 AM

How old are your Boge inserts? Seems like even if new they might be a little light for 28mm torsion bars. As for pulling, check wheel bearing, hose and bleed.

JohnJL · 08-12-2007, 01:21 AM

I just checked and they're Bilsteins. I suspect they are 30 years old, however they are all rebounding consistently. I also thought things would be OK since while they are designed for a 1500 kg car, if it weighed a half less, the brakes and shocks would do well against the new setup.

I admit I am tempted to take the coilovers off the street car (I bought it that way from Mike at Motomotions) and put them on the '*****.' Pardon my french, but she's earned the name.

j

JohnJL · 08-12-2007, 01:26 AM

Also, new bearings.

What do you meen by 'hose?'

I've bled them mercilessly, they perform awesome everywhere except that particular corner (the fastest corner in Au says Paul?)

Thanks
j