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View Full Version : 30mph bumpy ride in '05 Saab


JmuRiz
10-31-2012, 03:29 PM
My wife's Saab 9-3 has a bumpy ride at around 30mph on smooth road.
Had the new-ish tires balanced 2 times and it never corrected it. Saab place did say the roll-bar end-link bushings needed replacement soon, but I don't think that could cause this issue.

Any idea on what could be the cause?
Thanks for your input.

Potomac-Greg
10-31-2012, 03:48 PM
Consider bent wheel(s). You should be able to see a bent wheel on the balancing machine, but most tire shops can't fix it so don't diagnose it. It's most likely to happen on very low profile tires (35/40s) and on run-flats that have rock-hard sidewalls that transmit the blow to the wheel.

Jazzbass
10-31-2012, 03:59 PM
Only at 30mph? Not faster or slower? If it goes away as higher speeds, that would indicate that it's not an unbalanced or bent wheel, as these would just get worse. Also, IME, unbalanced wheels don't become noticeable until higher speeds (60mph+).

Define "bumpy". Steering wheel shaking? Where do you feel the bumps? In your hands or in your butt?

HoodPin
10-31-2012, 04:06 PM
One thing you can do yourself is jack up each corner, and while spinning each wheel, check the tread surface against some reference point in the fender, to see if there's a high spot moving up & down. Could be a bad tire, bent wheel, or a number of other things. If it appears to be spinning true, then likely some suspension issue.

I'm willing to gamble on a bad shock or two. If the shock isn't working, you can get some oscillating bounce against the spring, especially after going over a bump. Normally, the shocks helps dampen this oscillation.

JmuRiz
11-01-2012, 01:38 PM
How's the best way to test a shock to see if it's bad. I'm sure there is something better than bounce the car up/down and see how fast it reacts....

Re: Define "bumpy". Steering wheel shaking? Where do you feel the bumps? In your hands or in your butt?
You feel it in an up/down motion...slight movement in the wheel but mostly up/down. You can feel it at-speed, but it's only at certain speeds when you frequency is right to REALLY feel it (like 30mph and 65+)

APKhaos
11-01-2012, 01:43 PM
How's the best way to test a shock to see if it's bad.

Assuming the shocks are original, how many miles on the car? Shocks deteriorate slowly over time. Its only when you replace them that you get the full picture of how bad the original were. They can be tested on a shock dyno, but that process is probably as expensive than replacing them.

If damaged wheels are a possibility, try swapping wheels rear to front. If there is front wheel/s damage running the rears on the front should change the behavior.
Worn front suspension bushings may be contributing as well, of course, but unless you have bushings that are badly shot the shocks are the most likely source. Besides, you'll be surprised how much better the car rides with fresh front shocks!

Fritz
11-01-2012, 01:44 PM
I replaced 3 rims on my wife's 2002 9-3 in a two year period due to them getting bent or cracked on DC pot holes. I don't know why, but it's a common problem with Saabs of that vintage. My mother in law had a 9-5 Viggen with the same issue. It didn't seem to care if they were 17's or 19's, they all seem more sensitive to minor impacts.

JmuRiz
11-13-2012, 02:14 PM
I'll give a final update soon, took the car to the shop again. They re-tested the wheels (they said they tested them last time too as they also know they bend often) and they are true, and the tires are balanced. The shocks tested as fine as well. One thing that needed done that shouldn't/didn't effect the bumpy ride was the sway bar links.

They noticed we had different brand tires mounted when we replaced the tires (Continental ExtremeContact DWS instead of the stock Pirelli P6), they also noticed they have a stiffer sidewall and may need to lower the psi by 2. They are currently test driving with the lower tire pressure. I'll report the results tomorrow.

Thanks to all for your suggestions/input.

aerokurt
11-13-2012, 04:37 PM
If rotating the tires doesn't move the problem to another corner, and if it's not in the wheels or tires , then there is a good possibility that the inner cv joint is shot.
I've noticed this on Saab's and Subaru's at that speed when accelerating.
When and how does it occur?

JmuRiz
11-13-2012, 05:54 PM
Typically around 30mph, on any type of road, smooth, bumpy, undulating. Seems to a lesser degree or not there at all when going faster. I guess we'll see what the shop says tonight...didn't make the pick-up window.

aerokurt
11-26-2012, 02:23 AM
Well, inquiring minds want to know...................