Lotus Elan

reduce rear wheel travel

PostPost by: roebuck » Mon Sep 10, 2018 4:13 am

Hello,
Things moving along with my 1970 Elan S4 SE rear suspension.
I have fitted the smaller diameter springs to allow 185x14 wheels.
The drive shafts have CV joints both ends and I am finding when the car is on the hoist the wheels are at max travel the CV joints bind.
Is there a way of reducing this travel? Straps?
Rob
roebuck
First Gear
First Gear
 
Posts: 17
Joined: 17 Apr 2018
Location: Australia

PostPost by: Frogelan » Mon Sep 10, 2018 5:50 am

Rob

I am not the expert on this but I understand you need either anti-droop dampers or check straps. The former are sold by quite a few of the well known specialists. I have not seen check straps marketed (other than for MG's!).

If you have Konis, you could speak to Shaun Pickering of SP Suspension in Britain.

Andrew
1965 Lotus Elan S2 26/4022 (originally Dutchess Lotus East, PA and NJ Area, USA)
Frogelan
Third Gear
Third Gear
 
Posts: 297
Joined: 03 Jul 2017
Location: Paris, France

PostPost by: ericbushby » Mon Sep 10, 2018 8:34 am

Rob,
I fitted CV jointed shafts last year. They came from Kelvedon here in the UK.
It is essential to reduce the suspension droop with these shafts or the joints will be damaged. (with the exception of the more expensive shafts made by Elantrikbits in Australia)
Some people have fitted straps to the suspension which seem to work OK and it does avoid removing the rear suspension, but I did not like that method.
The obvious way to me is to buy shorter shock absorbers made specially for this.
If the existing shocks are in good condition, and will come apart then it is possible to fit tubular spacers in the top of the tubes to limit their travel.
I could not get into mine and they were as new, so I shortened the shafts by 30mm to obtain the same result.
Best of luck
Eric in Burnley
1967 S3SE DHC
Last edited by ericbushby on Mon Sep 10, 2018 9:06 am, edited 1 time in total.
ericbushby
Fourth Gear
Fourth Gear
 
Posts: 729
Joined: 13 Jun 2011
Location: east lancashire

PostPost by: gjz30075 » Mon Sep 10, 2018 8:59 am

Here's a solution (Rohan's , I think). Limiting straps
Attachments
t_elan_droop_cable_and_cvs_left_compressed_972.jpg and
t_elan_droop_cable_and_cvs_left_compressed_971.jpg
t_elan_droop_cable_and_cvs_left_compressed_971.jpg (77.82 KiB) Viewed 1011 times
Greg Z
45/0243K Sprint
36/5727 pre airflow coupe
User avatar
gjz30075
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2751
Joined: 12 Sep 2003
Location: Roswell, Georgia, USA

PostPost by: alan.barker » Mon Sep 10, 2018 9:52 am

Imho you have 4 choices
1. Aussie CVs
2. shorter Shocks
3. fit Spacer inside Shock
4. shorten Piston Rod on Shock (maybe not so easy)
For me the idea with a Cable is a bit of a bodge :shock:
If your Shocks are ok and you replace them with short ones that money could have been added to the Budget to buy CVs that don't mind drooping.
You need to look at the Total cost of the rear modification.
I like the idea of full Suspension travel how it was designed, comfortable.
Of course if you want to use the car on a Circuit it's different.
Alan.b Brittany 1972 elan sprint fhc Lagoon Blue 0460E
alan.barker
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1675
Joined: 06 Dec 2008
Location: BRITTANY FRANCE

PostPost by: roebuck » Tue Sep 11, 2018 7:04 am

Thank you everyone for your help.
The Aussi made shafts sound the way to go but they are A$1500.
Shockers are new so not keen on replacing them.
Rob
roebuck
First Gear
First Gear
 
Posts: 17
Joined: 17 Apr 2018
Location: Australia

PostPost by: rgh0 » Tue Sep 11, 2018 11:20 am

Yes the droop limiting cable shown was mine. it is not so much of a bodge as indicated as the spring and wheel load when it engaged was almost zero. it worked extremely reliably and gave me the handling desired for 20 years of racing

Using a droop limiting shock that limits when you have significant spring and wheel load is the same bodge. What you want to avoid is the sudden transition from a loaded wheel and spring to one that is unloaded and off the ground because it can droop no more.

There is no simple single answer to that issue and the whole of the suspension setup need to be considered.

By the way I replaced the shocks with TTR Konis that droop a little more than the limit cable but dont lock up the Cvs at that full droop so I removed the cable. The shocks come to the end of their travel when I have almost no spring load and almost no load on the wheel.

One of the issues with Elan handling on the limit is the limited droop on the front suspension and the front wheel can be carrying significant load on full droop due to the significant preload in the standard spring at full droop. This is the cause of much of the snap over steer on Elans on the limit and why I space down the rear aeon rubber springs as this prevents the rear sitting down on the outside and lifting the inside front wheel causing the transient. The snap over steer is actually caused by the drivers subconscious reaction to the transition in grip and steering feel as the front wheel leaves the ground and once I understood that I could avoid it and stayed on the track better :lol: The mods I made with the aeon spacers and stiffer front roll bar that takes the load off the front inside wheel more progressively made the difference and did not require so much training to avoid the overreaction on the transition.

Like I say you need to consider the total suspension as an integrated system not just one element

cheers
Rohan
User avatar
rgh0
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 7076
Joined: 22 Sep 2003
Location: Melbourne, Australia

PostPost by: roebuck » Thu Sep 13, 2018 12:21 am

Thank you Rohan,
Very helpful and that is what I need.
I have opted to buy ELANTRIKBITS drive shafts to resolve the problem with cvs binding.
I note al your other points but think I will have to have a specialist tune the suspension.
It is way out of my league.
Rob
roebuck
First Gear
First Gear
 
Posts: 17
Joined: 17 Apr 2018
Location: Australia

PostPost by: alan.barker » Thu Sep 13, 2018 8:34 am

+1
Imho you have made the best decision for road use.
On my Sprint i am still running with rotoflexs but if i go to change i will also go for the Elantrickbits.
I have Konis on the back standard length.
When you have them fitted please let us know what you think :wink:
Alan
Alan.b Brittany 1972 elan sprint fhc Lagoon Blue 0460E
alan.barker
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1675
Joined: 06 Dec 2008
Location: BRITTANY FRANCE

PostPost by: roebuck » Mon Sep 17, 2018 11:45 am

Hi
As I have mentioned I have fitted rear suspension with 2 1/4 inch ID springs.
I have been told I must fit AEON Rubber Spring Bump stops as the ones I have supplied by Paul Matty are useless.
I have looked on the Timbren Canadian site and there is not an AEON that will fit.
I understand they also be made in the UK?
Am I missing something?
Can anyone direct me on this problem?
Thanks,
Rob
roebuck
First Gear
First Gear
 
Posts: 17
Joined: 17 Apr 2018
Location: Australia

PostPost by: crypto » Sun Oct 07, 2018 5:48 pm

A few years ago I bought a set of drive shafts with universal joints from Tony Thompson racing. Same problem with the wheel travel. I modified the joints like this to allow full travel:

2015-07-18-1433-1024.jpg and
Drive shaft universal joint modification
The really good drivers have the bugs on the side windows (cit. Walter Röhrl)
User avatar
crypto
Second Gear
Second Gear
 
Posts: 102
Joined: 20 Apr 2014
Location: Switzerland

PostPost by: roebuck » Wed Oct 10, 2018 6:47 am

Thanks for your email.
I have just received the Elantrikbits shafts.
Going to be installed this weekend.
They look fantastic quality.
Will report on their performance.
Rob
roebuck
First Gear
First Gear
 
Posts: 17
Joined: 17 Apr 2018
Location: Australia

Total Online:

Users browsing this forum: No registered users and 11 guests