OFFROADSUBARUS.COM

Go Back   OFFROADSUBARUS.COM > General Forums > General Forum

Notices

Reply
Thread Tools Display Modes
  #1  
Unread 29th July 2017, 02:27 AM
MiddleAgeSubie MiddleAgeSubie is offline
Forum Member
 
Join Date: Dec 2013
Location: AZ
Year: 2013 / 2008
Model: H6 5EAT OB with SubieLiftOZ kit / Tribeca
Transmission: 5EAT
Posts: 863
MiddleAgeSubie is on a distinguished road
Default Explaining washboard damage

I know that Australia has some l-o-n-g heavily wash-boarded tracks. I also know that washboard can destroy vehicles.

Yet, this piece is about a road in Death Valley that is driven by whoever not, including rental sedans. There are trip reports about it on both the OB and the Foz forums. It does have a reputation for punctured tires and washboard but I had not heard anything apocalyptic. Yet, this apparently happened:

https://www.edmunds.com/car-buying/d...cat=affiliates

What do you think? I suppose they may have happened to drive it at the worst possible time, when severely washboarded and their speeds are in the dreaded mid-range for washboard. Still, destroying struts so quickly? The article does seem keen to show the capability of the independent suspension Honda.
__________________
18 4R TRDOP, 08 Tribeca
(13H6OB 2" SLOz, 06 B9)
Reply With Quote
  #2  
Unread 29th July 2017, 03:15 AM
Kevin's Avatar
Kevin Kevin is offline
Administrator
 
Join Date: Jul 2008
Location: Sydney, Oz
Year: MY'03
Model: Forester
Transmission: A/T
Posts: 4,526
Kevin is on a distinguished road
Default

My first thoughts - not aired down and travelling too slow. Should've been doing 40-50 MPH; you need to ride on the top of the ridges not bumping up and down in the valleys. My Triton is happy around 80 KPH / 50 MPH on most corrugations.
__________________
MY'03 Foz AT XS with centre lock-up
MY'10 Triton AT GLX-R 2.5 DiD
www.subaruclub.com.au
Reply With Quote
  #3  
Unread 29th July 2017, 04:55 PM
jf1sf5's Avatar
jf1sf5 jf1sf5 is offline
Forum Member
 
Join Date: Aug 2012
Location: Geneva, Switzerland
Posts: 1,621
jf1sf5 is on a distinguished road
Default

I'd follow what Kevin says but the interesting part is that all three pickups did the same track and the Ridgeline had the least damage to the suspension so its also probably due to the quality of the shocks and the different live axle vs independant suspension design.

On my '07 trip to Morocco, after few hundred kilometers on corrugated tracks I blew both rear top mount bushings even though I always travel very light (the SLS shocks were still in very good shape and lasted 4 more years !).

I believe that the rear suspension parts are more prone to breakage due to the bigger oscillations of the vehicule at the rear.
__________________
Subversive...
Reply With Quote
  #4  
Unread 30th July 2017, 12:57 AM
MiddleAgeSubie MiddleAgeSubie is offline
Forum Member
 
Join Date: Dec 2013
Location: AZ
Year: 2013 / 2008
Model: H6 5EAT OB with SubieLiftOZ kit / Tribeca
Transmission: 5EAT
Posts: 863
MiddleAgeSubie is on a distinguished road
Default

What does a blown rear top mount bushing feel like?

Other than choosing the worst speeds and pressures, what can one do to test/damage the vehicle on a washboard?
__________________
18 4R TRDOP, 08 Tribeca
(13H6OB 2" SLOz, 06 B9)
Reply With Quote
  #5  
Unread 30th July 2017, 03:58 PM
jf1sf5's Avatar
jf1sf5 jf1sf5 is offline
Forum Member
 
Join Date: Aug 2012
Location: Geneva, Switzerland
Posts: 1,621
jf1sf5 is on a distinguished road
Default

Quote:
Originally Posted by MiddleAgeSubie View Post
What does a blown rear top mount bushing feel like?
It rattles and makes some big "klonk, klonk, klonk" because there is no more rubber (in fact, the rubber is like dust !) between the metal parts of the bushing, other than that, you can still drive the car carefully and go home. I did an interim fix with some pieces of truck tires found on the track because I had 1'500km back to Switzerland.
__________________
Subversive...
Reply With Quote
  #6  
Unread 30th July 2017, 08:18 PM
Ratbag's Avatar
Ratbag Ratbag is offline
Administrator
 
Join Date: Jan 2012
Location: Bayside, Melbourne, Vic
Year: MY06, MY10
Model: Forester SG & SH
Transmission: 5MT/DR & 4EAT Sports
Posts: 6,226
Ratbag is on a distinguished road
Default

MAS, we call them corrugations here.

IME, every piece of corrugated road has a different wavelength or natural frequency. The trick is to find the speed at which the car's natural resonances and the frequency of the corrugations are not in harmony with each other! There are usually multiple speeds, starting at a low speed and then at points multiplied by two. eg 8 mph, 16, 32, 64. The starting point will be different for each set of corrugations.

The natural frequency of any particular set of corrugations will be determined by many factors, including soil type, resonant frequency of the vehicles that most commonly use the road, what speed they travel at, etc, etc.
Reply With Quote
  #7  
Unread 30th July 2017, 09:06 PM
MiddleAgeSubie MiddleAgeSubie is offline
Forum Member
 
Join Date: Dec 2013
Location: AZ
Year: 2013 / 2008
Model: H6 5EAT OB with SubieLiftOZ kit / Tribeca
Transmission: 5EAT
Posts: 863
MiddleAgeSubie is on a distinguished road
Default

So, is it possible that some wavelengths are more likely to cause damage than others?
__________________
18 4R TRDOP, 08 Tribeca
(13H6OB 2" SLOz, 06 B9)
Reply With Quote
  #8  
Unread 30th July 2017, 09:18 PM
Ratbag's Avatar
Ratbag Ratbag is offline
Administrator
 
Join Date: Jan 2012
Location: Bayside, Melbourne, Vic
Year: MY06, MY10
Model: Forester SG & SH
Transmission: 5MT/DR & 4EAT Sports
Posts: 6,226
Ratbag is on a distinguished road
Default

The lower the frequency of the corrugations, the greater the number of damaging harmonics, and the harder it is to avoid travelling at any speed that avoids them.

One should just travel very slowly over such stretches! These are not uncommon, but very easy to detect. If you can't find a speed where the car rides smoothly, slow down until it doesn't shake your teeth out. Chances are that the next section will be quite different.

Applying these strategies flexibly will minimise the chances of damaging the car.
Reply With Quote
  #9  
Unread 31st July 2017, 07:42 AM
ateday ateday is offline
Forum Member
 
Join Date: May 2014
Location: Happy Valley (not the loony bin)
Year: 2002
Model: MY03 Forester
Transmission: 5 sp manual
Posts: 620
ateday is on a distinguished road
Default

I hate corrugations with a passion.
I bent a rear strut on the (almost) trusty MY03 on the Finke track in 2012. Strange tyre wear after that until I realised what was wrong.
It does not matter what speed I travel at corrugations are still S..t !!!!!!!
Traveling to Cape York in 2007 the vibrations were so bad that the rear gate catch steel supporting surround fatigued and broke requiring a weld job.
Reply With Quote
  #10  
Unread 31st July 2017, 08:43 AM
Ratbag's Avatar
Ratbag Ratbag is offline
Administrator
 
Join Date: Jan 2012
Location: Bayside, Melbourne, Vic
Year: MY06, MY10
Model: Forester SG & SH
Transmission: 5MT/DR & 4EAT Sports
Posts: 6,226
Ratbag is on a distinguished road
Default

Yeah, Ate. No such thing as good corrugations ...
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -3. The time now is 04:51 AM.


Powered by vBulletin®
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.