Why is my ride so rough?

Shaun @ Tru6 · 06:56 AM

2 completely different cars, 2 different ride characteristics.

My old 84 Targa:
22/29s
new Bilstein Sports all around
factory F/R sway bars
Elephant Racing polybronze front and rear
17 inch wheels, variety of tires from Victoracers to Pilots, 50/45 sidewalls
ride height set: 23.75 in the rear, 24.25 in the front
cornerbalanced

New 73 Coupe:
19/26s
Used but "good" Bilsteins all around, unsure of settings, but most likely heavy duty
factory F/R sway bars
factory rubber bushings in good shape
15 inch wheels with 195/65s & 215/60s A008s
ride height set: 24 in the rear, 24.5 in the front
yet to be aligned but does drive straight down the road, front swaybar not connected until I get it aligned

The 84 drove smooth and comfortable over most surfaces, even Boston's worst roads. Had Momo fixedback seats in it and it was very comfortable, even on long trips to NY.

The 73 is harsh. On smooth surfaces, it has a nice crisp "feel of the road" but almost grainy at times. On highway expansion joints and generally bad roads around town, it's much more harsh than I think it should be.

Any thoughts on why this might be? Did the used shocks give up the ghost on install? My only other thought is that Targa being a flexi-flyer absorbed a lot more bump energy, though front shock tower bar and BK harness brace really did wonders for tightening up the car.

ossiblue · 11-30-2009, 07:01 AM

Having a 73 myself, the wife notice a harsher ride over the 75. You've got a lot of differences in you set ups, but possibly one major factor is the unsprung weight of the 84 vs the 73--the 73 being lighter and more sensitive to road "noise." Just a thought.

88-diamondblue · 07:19 PM

If those are the Yoko A008's they are probably close to 10 years old. My old AVS-I's rode much harder than my new low profile Falkin RT-615. And the A008's that I had were even rougher riding then the AVS. Check to see what the manufacture date is on the tires.

tobluforu · tobluforu's Garage

The 73 is a bare-bones 911, the 84, even though it had lots of susp. mods, is like driving in a luxury car. Well maybe not with that seat you had in there. Seriously, my 72 feels like there isn't anything between me and the road, but I have been in cars like your old one that felt like a RR compared to it. I too have Aoo8's and they are loud as hell.

Shaun @ Tru6 · 11-30-2009, 10:05 AM

Thanks guys. It could be the A008s. I bought them recently, they are "new" and were stored properly for some time...that being the last year A008s were made until now. Using only my hands, the tires were still soft and pliable, as much so as a sport tire can be. I compared them to some newer S03s I had and there was no difference. But then I only grabbed then and pushed and pulled. I could not find a date code/stamp anywhere on the tires or on the Yoko tape still on them. They aren't loud, but certainly could become so. On the highway, the car is remarkably quiet, much more so than my 69E. As a whole, the car handles very very well, even on relatively cold roads here now.

My gut says it's part tire (I agree with you Michael, back in the day they were rough riding out of the factory) and part old car. My E never felt this way, but it was riding on 70 series touring balloons and original suspension.

the best test would be to put on some 215/60 Michelin all-seasons I've got and see what happens. I've got a bead on 4 7x15 nice cookies that would be perfect.

thanks again!

RWebb · RWebb's Garage

1. wt.

2. old tires

3. "factory rubber bushings in good shape" - I bet they are NOT in good shape! How old? Did you test the bushing for deflection per nit force on a machine? If old, they are likely hard as a rock...

car's a beauty tho!

Chuck Moreland · 11-30-2009, 06:10 PM

Your torsion bars are too soft for the ride height. The car is bottoming out frequently.

There could be other issues too. You have mystery shocks. They may be sports or otherwise poorly matched to the shocks, or simply worn out.

Check out your bump stops too, make sure they are setup right.

The quick fix is to add 1.5 inches of ride height. If you want to keep it low, you need some combination of stiffer tbars, shorter shocks, raised spindles.