Lotus Elan

rear suspension

PostPost by: rgh0 » Thu Feb 04, 2010 10:31 am

Without something equivalent to the orginal Aeon ruber spring in place or stiiffer steel springs at the rear you will get the oversteer your experience in a corner. Its more pronounced in an Elan than a plus 2 due to the narrower track but you will get it just as you describe.

The Plus 2 is totally neutral when the suspension is set up as original

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PostPost by: Robbie693 » Thu Feb 04, 2010 3:07 pm

Mine sits high at the back too, I haven't noticed a spacer plate as Rohan mentions. Is this between the Lotocone and the chassis similar to what Andy has done? (see "Rear spring Seats" in the Elan section)

I was going to try slackening the wishbone bolts to see if they had been tightend without the weight on the wheels. In Brian Bucklands book he mentions setting the ride-height by jacking each corner "until the desired ride height is achieved". Does this mean any ride height can be set or will it only go as far as each spring allows?

Sorry if this sounds dim - I find suspension theory a bit confusing. The high rear is getting on my nerves

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PostPost by: Craig Elliott » Thu Feb 04, 2010 5:53 pm

Robbie - the spacer Rohan refers to is a cylinder that sits inside the spring on top of the main body of the damper (immediately above the threaded damper retainer) and the damper rod goes through the middle of it. The rubber spring/bumpstop sits above it. It doesn't affect the ride height, it just means that the rubber bumpstop comes into action sooner as the spring compresses.

As you indicate, you need to tighten the wishbone bolts when the suspension is under "static load" - this means that you support the weight of the car on the wheels (or hubs) and you need to load it along its centre line with 168lbs/76.2kg on the front seats, 80lbs/36.3kg on the rears, 72lbs/32.6kg in the boot/trunk, and 50lbs/22.7kg or 22.7 litres of fuel in the tank. I don't know if this will make any difference to your rear ride height - I (more or less!) did the above when setting my car up but even so the ride height still looks a little high at the back.

I'm not sure what difference jacking the sides of the car up or down will make (as referred to in Brian Bucklands book), it sounds odd. Maybe he means bouncing the suspension up and down before tightening them when it's under static load to ensure that the bushes haven't stuck in the unloaded position?? You can't set the ride height unless you've installed adjustable spring seats...

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PostPost by: andyelan » Thu Feb 04, 2010 7:58 pm

Hi Everyone

Jono, your comment that Tony Thompson suggests setting Konis 1.5 turns up from their minimum setting is interesting as the red Koni Classics (ref 86-1371) for the Plus 2 only have two turns in total he's therefore suggesting they need to be set near to their maximum. This would seem to confirm my suspision that if set to their minimum, as is Konis recomendation, then they are going to be far too soft.

Although I'll admit I'm now getting a little bit out of my depth, I was under the impression that with a car like the Plus 2 which has soft springs and no rear anti-roll bar, you rely on relativly high damping rates as this is all their is to control the cars tendency to roll oversteer (rubber helper springs aside). Perhaps Rohan can help me out here.

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Andy
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PostPost by: gerrym » Thu Feb 04, 2010 8:46 pm

Andy, I recall that the Elan Factory did some testing a few years ago and quantified the anti-roll stiffness contribution from the 4 rear drive-shaft donuts. Small but significant I think was the conclusion. (Don't quote me but think in the region of 1/6 the front ARB roll stiffness)

Robin, big bonus of the 2-1/4" ID springs is that off the shelf springs are available at modest cost: not Lotus specific. Ride height can be tuned by an 1" or so to take care of any intended use of the car or indeed spring variation to spec, or sag.

Regards
Gerry
http://www.dfaulknersprings.com/sp225140.htm
eg Faulkners can provide the following off the shelf
2.25" (58.5mm) Internal Diameter 14.0 " Free Length Standard Springs


Part Number Description Price Each Ex VAT
14S0060 14" Free Length x 60 lbs ?26.00
14S0080 14" Free Length x 80 lbs ?26.00
14S0100 14" Free Length x 100 lbs ?26.00
14S0120 14" Free Length x 120 lbs ?26.00
14S0130 14" Free Length x 130 lbs ?26.00
14S0140 14" Free Length x 140 lbs ?26.00
14S0150 14" Free Length x 150 lbs ?26.00
14S0160 14" Free Length x 160 lbs ?26.00
14S0170 14" Free Length x 170 lbs ?26.00
14S0185 14" Free Length x 185 lbs ?26.00
14S0200 14" Free Length x 200 lbs ?31.00
14S0225 14" Free Length x 225 lbs ?31.00
14S0250 14" Free Length x 250 lbs ?31.00
14S0275 14" Free Length x 275 lbs ?31.00
14S0300 14" Free Length x 300 lbs ?31.00
14S0325 14" Free Length x 325 lbs ?31.00
14S0350 14" Free Length x 350 lbs ?31.00
14S0375 14" Free Length x 375 lbs ?31.00
14S0400 14" Free Length x 400 lbs ?33.60
14S0425 14" Free Length x 425 lbs ?33.60
14S0450 14" Free Length x 450 lbs ?33.60

I'm sure there's a Australian or NZ spring supplier that can provide equivalents without the UK shipping cost element.
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PostPost by: bengalcharlie » Thu Feb 04, 2010 9:05 pm

Thanks everybody for your comments. Thanks jono for your spring rates and setup on your car although it is a pitty you have no driving experience yet with this set-up.
Rohan thanks also for your contribution because you have obviously a lot of experience with elans and racing combined with common sense so thanks.
Gerry thanks for you links to several suppliers. I had a chat to my local suspension specialist and they can supply everthing, no problem but the price is steep compared with sourcing it from the US becauser I can bring it back as luggage and therefore I do not have to pay shipping.
I saw that the treaded sleeves that fit over the excisting shock tube are either available in steel or aluminium??
I can see the advantage of steel that you can weld it the the strut housing but are there any benefits of using an aluminium sleeve??
I did found a koni and FACO set-up on www.summitracing.com but they are in aluminium. I suppose you glue these in place??
Any comments with regards to this would be appreciated.
Better go into the garage now and fit the last A-frame.
cheers
Robin
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PostPost by: jono » Fri Feb 05, 2010 9:13 am

Here is a pic of my set up.

I have also fitted polybushes so, .....in theory, the car should settle without needing to preload the bushes

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PostPost by: SimonH » Fri Feb 05, 2010 7:39 pm

Jono,

Are those the TTR fabricated top spring mounts?

Cheers,
Simon
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PostPost by: jono » Fri Feb 05, 2010 9:21 pm

Hi Simon,

Yes they are TTR top mounts with a coat of paint. I figured ?48 each + vat for spyder versions was, err, a bit :shock:

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PostPost by: bengalcharlie » Fri Feb 05, 2010 10:08 pm

put lat A-frame in yesterday and went for a short testdrive. First impressions are good but will test drive more for a couple of weeks and then make a decisions about the spring rate/ adjustable/non adjustable options.
ride height is a bit too high as predicted but nothing that can not be fixed.
cheers
Robin with black hands and fingernails! ( luckily I am on holiday)
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PostPost by: SimonH » Fri Feb 05, 2010 10:24 pm

jono wrote:Yes they are TTR top mounts with a coat of paint. I figured ?48 each + vat for spyder versions was, err, a bit :shock:

Thanks Jono.
I had wanted to see what they are like as I maybe will combine them with some threaded adjuster sleeves from Rally Design. Much cheaper than Spyder overall.

I'll stop the thread hijack now.

Cheers,
Simon
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PostPost by: Robbie693 » Sun Feb 07, 2010 6:08 pm

Craig Elliott wrote:Robbie - the spacer Rohan refers to is a cylinder that sits inside the spring on top of the main body of the damper (immediately above the threaded damper retainer) and the damper rod goes through the middle of it. The rubber spring/bumpstop sits above it. It doesn't affect the ride height, it just means that the rubber bumpstop comes into action sooner as the spring compresses.

As you indicate, you need to tighten the wishbone bolts when the suspension is under "static load" - this means that you support the weight of the car on the wheels (or hubs) and you need to load it along its centre line with 168lbs/76.2kg on the front seats, 80lbs/36.3kg on the rears, 72lbs/32.6kg in the boot/trunk, and 50lbs/22.7kg or 22.7 litres of fuel in the tank. I don't know if this will make any difference to your rear ride height - I (more or less!) did the above when setting my car up but even so the ride height still looks a little high at the back.

I'm not sure what difference jacking the sides of the car up or down will make (as referred to in Brian Bucklands book), it sounds odd. Maybe he means bouncing the suspension up and down before tightening them when it's under static load to ensure that the bushes haven't stuck in the unloaded position?? You can't set the ride height unless you've installed adjustable spring seats...

Craig


Thanks Craig, fingers crossed on the re-torque then

I'll stop the thread hijack now.

Cheers,
Simon


Me too, sorry

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PostPost by: elansprint71 » Sun Feb 07, 2010 9:29 pm

rgh0 wrote:.................

The other item to consider is the Aeon rubber springs at the rear- as these help control the rear end when heavily loaded - do you still have them and are they in good condition? As you cant buy them new now many people appear to have either disgarded them or replaced them with a small bump rubber that does not perfrorm as an auxillary spring like the orginal design was intended.............
Rohan


Not for the first time Rohan has beaten me to it! I was about to suggest add-on rubber units, as used by the folks who tow caravans around (is it caravans, or trailers, in NZ?). I think there are some types advertised in caravan magazines (I only ever look at these in the dentist's or barber's btw, so I'm not an expert).
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PostPost by: Greg Foster » Mon Feb 08, 2010 1:20 pm

Are there rear sway bars available for the +2? If so, how would installing one change the dynamics of the suspension? What might you have to upgrade in order for all the work to balance itself both front and back? Just curious.
Greg
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PostPost by: fatboyoz » Sun Mar 11, 2012 6:05 am

Jono,
Just doing my rear suspension. Could you please tell me the make, model and place of purchase of the bump-stops you have used. They look to be more substantial than others that I have seen.
Regards,
Colin.


jono wrote:Here is a pic of my set up.

I have also fitted polybushes so, .....in theory, the car should settle without needing to preload the bushes

Jono
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