Lotus Elan

What would be a quickie damper check?

PostPost by: billwill » Thu Jul 19, 2018 8:50 am

What result could one expect from a quickie damper test, i.e pressing down on one rear corner and releasing it.

Would one expect:

a. smooth return to normal ride position with no overshoot?

b. rapid return to normal ride position, but a single overshoot (rear momentarily higher than normal ride) followed by downward return to normal ride position.

c. similar to (b) but with two or more oscillations.
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
billwill
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4716
Joined: 19 Apr 2008
Location: London UK

PostPost by: JonB » Thu Jul 19, 2018 8:52 am

I think a).

c) definitely means the dampers are finished, so I guess b) is somewhere in between.
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2102
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: ericbushby » Thu Jul 19, 2018 9:37 am

Bill, just checked mine.
Slight overshoot on return when tested the first time.
Smooth return to rest position subsequently.
I believe they were fitted in 2006, but the car was not used until 2011 when I bought it.
They have done about 7000 miles.
Hope this helps.
Eric in Burnley
1967 S3SE DHC
ericbushby
Fourth Gear
Fourth Gear
 
Posts: 831
Joined: 13 Jun 2011
Location: east lancashire

PostPost by: elanner » Thu Jul 19, 2018 11:51 am

+1 to Jon & Eric

Definitely: a.

Smooth, and surprisingly slow, return. No overshoot/bounce. As Eric mentions, the first bump seems to prime the damper in some way.

Rear: Minimal damping on bound, heavy damping on rebound.
Front: Medium damping on bound and rebound.

I clearly remember being fascinated by this difference in behaviour when it was demonstrated to me back in the 60s. I was just a yoof and thought all dampers were the same. I've always assumed it's correct and am fairly sure I've seen it documented somewhere. Although a good number of Elans I've surreptitiously tested in recent years don't do this.... :-(

Nick
User avatar
elanner
Fourth Gear
Fourth Gear
 
Posts: 512
Joined: 14 Sep 2010
Location: Boston, MA, USA

PostPost by: 69S4 » Thu Jul 19, 2018 12:51 pm

elanner wrote:Smooth, and surprisingly slow, return. No overshoot/bounce. As Eric mentions, the first bump seems to prime the damper in some way.

Rear: Minimal damping on bound, heavy damping on rebound.
Front: Medium damping on bound and rebound.

Nick



My rear dampers also seem to need one bump to prime them. The current ones (Koni I think ) and the previous two sets all exhibit the same characteristic. Push down the first time after the car's been standing and it feels like there's no damping at all. Push again and it's fine. It's never been a problem as I've figured the first priming movement is done by me getting into the car but it is odd and not something I've ever experienced on any other car or motorcycle damper. I've always assumed it's something to do with the damper internal structure rather than a fault (I'd be unlucky indeed to have six dampers from at least two different manufacturers exhibit the same fault).

The rear damping does seem to be mainly on rebound with very little on compression. For road use I've played with the damping rate to find 'optimum' rate that if you go beyond does make the ride very harsh. Hit a series of pot holes (easy with the current state of UK roads) with the damping to high and you'll get double vision.
Stuart Holding
Thame UK / Alpe D'Huez France
69 S4 FHC
Honda GoldWing 1800
Honda CBX1000
Kawasaki H1 500
Yamaha XS2
69S4
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1198
Joined: 23 Sep 2004
Location: nr Oxford UK

PostPost by: nigelrbfurness » Fri Jul 20, 2018 8:30 am

I concur. The rear dampers always seem to need one stroke to get them working with normal resistance. Someone told me that it was because elan rear suspension has more travel than most similar systems but I couldn't comment on that. To misquote Stan Smith, it happens irregardless of damper make.
1970 S4SE/1760cc big valve/SA-AX block, L2s, 45DCOEs, 1978 Jensen GT, 1962 AH Sprite, Alfa-Romeo 159, 1966 Bristol Bus, 1947 AEC Regal bus.
nigelrbfurness
Third Gear
Third Gear
 
Posts: 396
Joined: 04 Apr 2008
Location: Dunmow, Essex, UK

PostPost by: JonB » Fri Jul 20, 2018 8:59 am

Ah, so my rears are not tatered then! I had noticed that first stroke was undamped and thought the shocks (Konis) were gone. During my visit to Spyder I was informed the fronts were gone, but not the rears (I was not sure at the time). Some good news for once. :D

Now on the fronts, I did the "jump up and down on the wheel arches" test and it seemed to me the car returns to the resting position per a) above, even though Spyder said they were dead. Perplexed, somewhat!
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2102
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: vincereynard » Sun Jul 22, 2018 11:09 am

JonB wrote:Now on the fronts, I did the "jump up and down on the wheel arches" test and it seemed to me the car returns to the resting position per a) above, even though Spyder said they were dead. Perplexed, somewhat!


I wonder if spyder had a pair they could have sold you? Default position 3 :wink:

It was like that when it got here Guv / Wasn't us wot done it / Can we sell you a new bit?
vincereynard
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1215
Joined: 12 Jan 2015
Location: amersham

PostPost by: JonB » Sun Jul 22, 2018 12:08 pm

Ha ha Vince, knew you?d bite!

:)
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2102
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: vincereynard » Sun Jul 22, 2018 7:57 pm

JonB wrote:Ha ha Vince, knew you?d bite! :)


Be fair, I waited 2 days!
vincereynard
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1215
Joined: 12 Jan 2015
Location: amersham

PostPost by: JonB » Mon Jul 23, 2018 9:50 am

Mate, I think you're slipping...!
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2102
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: billwill » Mon Jul 23, 2018 10:53 am

I found what looks like a good article on car dampers, but it's a bit too long for me to have absorbed yet:

http://www.kaztechnologies.com/wp-conte ... sprzak.pdf
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
billwill
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4716
Joined: 19 Apr 2008
Location: London UK

PostPost by: billwill » Mon Jul 23, 2018 10:58 am

Case (a) is known as critical damping, I knew that before, but didn't want to include jargon terms.
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
billwill
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4716
Joined: 19 Apr 2008
Location: London UK

PostPost by: rgh0 » Mon Jul 23, 2018 11:25 am

Car shocks have a complex valving system to control damping at various velocities in both bump and rebound. A simple low speed bounce test tells you very little about the condition at high velocity movement when on the road. Some suspension places can do an on car damper test where they vibrate the wheel up and down at various velocities and measure the damper performance. Do this or just buy new shocks if your shocks have been on the car for more than a few years

cheers
Rohan
User avatar
rgh0
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 7486
Joined: 22 Sep 2003
Location: Melbourne, Australia

PostPost by: billwill » Mon Jul 23, 2018 4:41 pm

My Konis have been there a looooooooooooooong time.
:D
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
billwill
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4716
Joined: 19 Apr 2008
Location: London UK
Next

Total Online:

Users browsing this forum: FullerJ, RichardHawkins and 10 guests