Why does suspension get soft?

dgw · 07-15-2006, 01:58 AM

Now at 29K I would swear my Prius is no longer handling as well as when new. It's more soft and imprecise to the point that it's a bit of a handful in crosswinds and takes more attention than usual at highway speeds. There is more lean and yaw when cornering or making "s" curves. Also, disruptions in the surface (cracks, seams, potholes) seem to be hitting harder. I feel stupid asking, but is it the springs or the shocks or both that get worn out? tired? fatigued? Or something else?

Note that other cars I have owned here have exhibited these symptoms at anywhere from 15k to 25k. No set of tires has lasted more than 20k and even at that were pretty bald. The stock Integrities didn't even make it to 15k. So my local driving conditions are pretty demanding (up and down a very twisty 16% hill 5 or 6 times every day and do alot of driving around Hwy 1) and I go through curves fairly quickly.

I'm thinking of ordering the TRD Sportivo suspension set. Any other suggestions that will improve the handling? I have already installed the BT stiffening plate and am riding on GY Triple Treads at 42/40.
Thanks
Doug

**Tideland Prius** · 07-15-2006, 03:35 AM

Hmm.. I'm at 31,000kms on my original sets of Integritys. They seem okay. Maybe the roads up here are better?

An easy way to check the suspension on any car is to press down hard on the hood or trunk. Watch the car oscillate. If the suspension is new, it should just rebound the moment you stop applying pressure. Otherwise, it'll oscillate. Even if it stops after the 2nd rebound, it's fine. It's bad if it keeps oscillating (like I've seen on some cabs after they go over a bump in the road like an intersection) or if it doesn't stop after.. say 4 or 5 rebounds.

donee · 07-15-2006, 08:04 AM

<div class='quotetop'>QUOTE(dgw @ Jul 15 2006, 02:58 AM) [snapback]286607[/snapback]</div>

Quote:

Now at 29K I would swear my Prius is no longer handling as well as when new. It's more soft and imprecise to the point that it's a bit of a handful in crosswinds and takes more attention than usual at highway speeds. There is more lean and yaw when cornering or making "s" curves. Also, disruptions in the surface (cracks, seams, potholes) seem to be hitting harder. I feel stupid asking, but is it the springs or the shocks or both that get worn out? tired? fatigued? Or something else?

Note that other cars I have owned here have exhibited these symptoms at anywhere from 15k to 25k. No set of tires has lasted more than 20k and even at that were pretty bald. The stock Integrities didn't even make it to 15k. So my local driving conditions are pretty demanding (up and down a very twisty 16% hill 5 or 6 times every day and do alot of driving around Hwy 1) and I go through curves fairly quickly.

I'm thinking of ordering the TRD Sportivo suspension set. Any other suggestions that will improve the handling? I have already installed the BT stiffening plate and am riding on GY Triple Treads at 42/40.
Thanks
Doug
[/b]

Hi Doug,

I would pull the BT stiffening plate and inspect the thin metal at the bottom of the mounting hole for cracks and/or metal fatique (look for decrystalisation of the aluminum alloy - kinda a grainy surface ). Its sounds like it may have failed, but only an inspection will tell for sure.

tnthub · 07-15-2006, 10:21 AM

Chamging out the rubber bushings for some poly units may also help stiffen the car back up and the parts probably cost less than a decent steak at the supermaket of you deal with a regular parts store instead of a dealer... I am a great believer in trying the inexpensive things before spending large dollars.

dpower · 07-15-2006, 10:51 AM

I have found that most factory suspensions get soft at 30-40k. A new set of KYB shocks and struts firms things back up again and seem to last much longer.

I've installed the TRD sportvio suspension and really liked the change from stock but it is a bit pricey compared to just doing a after market replacement on the shocks and struts alone ($1400 installed). It also lowers the car just a bit if you have clearance problems. The new variable rate springs are quit a bit firmer than stock and helped with the body roll. I also live in a rural area and have a hilly twisty road to traverse during the daily commute.

On some of my other cars I have done the bushing swap to poly bushings and found that it did tighten up things some, it also greatly increased the noise and vibration transferred to the cabin. On my jeep the vibration was so bad the the steering wheel would vibrate out of my hands at an idle. I ended up swapping the transmission busings back to stock to get rid of that.

07-15-2006, 03:35 AM	#2
Tideland Prius Moderator of the North Join Date: Oct 2004 Location: Canada Posts: 21,204 My Car: 2010 Prius Model: N/A Package: Technology Package (Canada) Thanks: 370 Thanked 529 Times in 356 Posts Friends: 26	Hmm.. I'm at 31,000kms on my original sets of Integritys. They seem okay. Maybe the roads up here are better? An easy way to check the suspension on any car is to press down hard on the hood or trunk. Watch the car oscillate. If the suspension is new, it should just rebound the moment you stop applying pressure. Otherwise, it'll oscillate. Even if it stops after the 2nd rebound, it's fine. It's bad if it keeps oscillating (like I've seen on some cabs after they go over a bump in the road like an intersection) or if it doesn't stop after.. say 4 or 5 rebounds. __________________ 2005 Tideland Pearl Premium Package 25/10/04 VVT-i Emblem, Sport Pedals, All-Weather Mats, Cargo Mat, Cargo Net, Wheel Locks, EV Mod, JDM Prius Footwell Lighting, DICE iPod Kit, LED lights 2008 Deep Black smart fortwo passion coupé - sold (6.1L/100km) 2010 Blue Ribbon Metallic Technology Package 29/08/09 All-Weather Mats, Homemade Console Pads, LED lights, Illum. Scuff Plates, Cargo Net, Wheel Locks "Ask an Expert" on Facebook I am not employed by Toyota, and the opinions expressed by me as a Prius Expert are not those of Toyota.

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07-15-2006, 01:58 AM	#1
dgw Member Join Date: Jun 2005 Location: Mill Valley, CA Posts: 34 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Now at 29K I would swear my Prius is no longer handling as well as when new. It's more soft and imprecise to the point that it's a bit of a handful in crosswinds and takes more attention than usual at highway speeds. There is more lean and yaw when cornering or making "s" curves. Also, disruptions in the surface (cracks, seams, potholes) seem to be hitting harder. I feel stupid asking, but is it the springs or the shocks or both that get worn out? tired? fatigued? Or something else? Note that other cars I have owned here have exhibited these symptoms at anywhere from 15k to 25k. No set of tires has lasted more than 20k and even at that were pretty bald. The stock Integrities didn't even make it to 15k. So my local driving conditions are pretty demanding (up and down a very twisty 16% hill 5 or 6 times every day and do alot of driving around Hwy 1) and I go through curves fairly quickly. I'm thinking of ordering the TRD Sportivo suspension set. Any other suggestions that will improve the handling? I have already installed the BT stiffening plate and am riding on GY Triple Treads at 42/40. Thanks Doug

07-15-2006, 10:21 AM	#4
tnthub Senior Member Join Date: Jun 2006 Posts: 463 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Chamging out the rubber bushings for some poly units may also help stiffen the car back up and the parts probably cost less than a decent steak at the supermaket of you deal with a regular parts store instead of a dealer... I am a great believer in trying the inexpensive things before spending large dollars.

07-15-2006, 10:51 AM	#5
dpower Member Join Date: Mar 2005 Location: Austin Posts: 36 My Car: 2005 Prius Model: II Package: #2 Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I have found that most factory suspensions get soft at 30-40k. A new set of KYB shocks and struts firms things back up again and seem to last much longer. I've installed the TRD sportvio suspension and really liked the change from stock but it is a bit pricey compared to just doing a after market replacement on the shocks and struts alone ($1400 installed). It also lowers the car just a bit if you have clearance problems. The new variable rate springs are quit a bit firmer than stock and helped with the body roll. I also live in a rural area and have a hilly twisty road to traverse during the daily commute. On some of my other cars I have done the bushing swap to poly bushings and found that it did tighten up things some, it also greatly increased the noise and vibration transferred to the cabin. On my jeep the vibration was so bad the the steering wheel would vibrate out of my hands at an idle. I ended up swapping the transmission busings back to stock to get rid of that.