Lotus Elan

Postive Camber - Advice Please

PostPost by: Mohe » Thu Jan 05, 2006 1:15 pm

I have recently taken my totally rebuilt renovation project (Series 3 baby Elan) out on the open road for the first few times and, amazingly, nothing has yet fallen off. Yippee. It is quiet, comfortable and decidedly nippy. The big surprise has been how many other drivers stop to let me out of side roads. :D

But this baby elan has a slightly nose-up appearance. The front sits higher than the rear. There is just enough clearance round the rear, standard wheels so I suspect the front is sitting higher than normal. There is also noticeable positive camber at the front. For clarity I mean the lower part of the front tyres are slightly closer together than the upper parts of the front tyres.

The car had a new standard chassis from Spyder plus new shock absorbers (dampers) on both ends. At the front I bought and fitted replacement sping/damper units. At the back I had the uprights serviced and fitted with new shock absorbers but retained the existing springs. The steering is a little heavy as well.

Should the car sit flat and have no negative camber? Could anyone suggest where I might start looking for a problem? Are there known, correct measurements of ride height I could check against? Could I have the assembly wrong somewhere? Could some springs be the wrong length?

I would really appreciate some suggestions and especially measurements I can check.

Thank you in advance


geoff reiss
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PostPost by: gjz30075 » Thu Jan 05, 2006 1:44 pm

Heavy steering?? Did you tightened everything up on the suspension when the car was in the air? If so, this could be your problem. Get the car on the ground and loosen all the suspension points, bounce the car a few times, then tighten them to spec. This is probably best done on a lift.

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PostPost by: nebogipfel » Thu Jan 05, 2006 1:49 pm

Geoff,

Two things .... did you let the front settle to normal ride height before tightening the wishbones?

The other thing, and I know this will be controversial, which front shocks did you fit? I tried Spax adjustables on the front of mine and the extra length in the shock body to accomodate the adjusting mechanism really screwed up the front geometry. I took them off and put good old OEM units on and suddenly everything looked right - harmony was restored :)

I assume the spring lengths are correct

An Elan should sit nice an flat on the road.

Why are you surprised that people let you out of side roads? They are simply paying respect to one of the most beautiful cars ever built! No mystery there
:lol:
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PostPost by: type26owner » Thu Jan 05, 2006 2:15 pm

The 1/2 degree positive camber is the norm at the correct ride height. That was the accepted way to get the most from the SLA (short/long a-arms) suspension and the tires of that era. Luckily the grip level is still quite high with a modern day radial tire installed. A radial will tend to scrub off the outside edges of the front tires before the rest of the thread is worn out is all.

The trunnion does not allow the front suspension to have any anti-dive. It's important to balance the amount of braking force with enough suspension travel and spring rate so when threshhold braking is required the body does not slam down on the bumpstops, instantly overloading the front tires causing massive understeer. The stock springs are totally inadequate for performance driving.

Replacing the stock springs is not expensive and changes the handling for the better if you go to stiffer ones. It's rather silly not to do the 2.50/2.25" ID spring upgrade on rear struts and gain the ability to adjust the ride height there.

Simple and inexpensive changes to the suspension will transform it from a lead sled to a road warrior. :D
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PostPost by: sk178ta » Thu Jan 05, 2006 4:20 pm

I too have a rebuilt S3 that sits a bit nose up, or rather, bum down. I tried loosening all the wishbone/bush bolts and re-tightened with the car on it`s wheels, bounced etc. It made no difference. I then replaced the rear dampers with TTRs with new springs and it still sits a bit nose up. Having said that, it handles beautifully. I`ve been on quite a few tracks, giving it a good spanking, and the balance is very neutral with lovely power-on oversteer on demand so I`m disinclined to mess with, say, shortening the front springs.
More critical than anything, despite what the technophiles might imply, are the tyre pressures. I find 22 p.s.i. front and 24 rear on Goodyears an optimimum between handling, grip, and ride.
Incidentally, I`m on my third Elise, now a 111R, and have found in the past, that even a 2lb pressure drop, on one wheel, is very noticeable.
Jim
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PostPost by: nebogipfel » Thu Jan 05, 2006 6:18 pm

I'm not sure if you can see a half a degree of positive camber but out of the factory there was no obvious visible camber and the cars sat straight and level.

There is lots written about how you can change this or modify that to improve the Elan but having owned a Sprint in the early seventies just the way Colin designed it I can only say it was truly impressive. That is, with everything per factory spec' and in good condition.

If you are building a car for the track then certainly mod's are appropriate but why mess with springs and dampers for the road? It may stiffen the car up a bit but will be at the expense of one of the truly revolutionary things about the Elan which is the ride quality.

Just re-read some of the contemporary road tests of the Elan written by the normally jaded motoring press.
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PostPost by: rgh0 » Fri Jan 06, 2006 9:37 am

The Elan was truely outstanding in both ride, grip and responsive handling compared to its sixties contemporaries. It made the most of the tyres of the day. With modern tyres a lot of the ultimate grip advantages of the Elan compared to other sports cars of the era have been lost but its handling responsiveness ( fun) and ride advantages still remain.

Having said the above there are still opportunities to improve an Elan for normal road use compared to the original standard setup when using modern high grip tyres without signficantly adversly affecting it ride and responsiveness. The key problem with an Elan today on the road is that it is too soft in roll at the rear and also at the front to a lesser degree. This results in the car sitting down on its rear outside wheel if you go into a corner at about the right speed resulting in excessive oversteer. Altenatively it sits down hard on its outside front wheel if you go into a corner to quick resulting in excessive understeer. Modern tyres also create greater weight transfer to the front under the high braking that can be generated. This results in the front springs hitting the bump stops ( as Keith observed) and the rear wheels locking up as they are over braked when unloaded.


To address the above issues you can do the following.

1. A stiffer front roll bar to .750 inch or 13/16
2. Put a 20mm spacer above and below the rear strut rubber bump stop and ensure the bump stops themselves are in good condtion. An alternate to this is a rear roll bar but that a lot harder to fit and tune.

These 2 items increase the roll stiffness with no signficant affect on ride. The springs are really still to soft but you will notice better handling.

3. The next stage is to increase the spring stiffness. Most drivers can only notice a minimum of 50% spring rate increase in terms of ride or handling. An increase in spring rate by this amount in an Elan will improve handling signficantly further above steps 1 and 2 with minimal if any extra harshness noticeable in the ride. You will feel greater ride variation from different brands of tyres than you will from this spring rate increase.

The final stage is to setup camber right for modern radials

4. The right camber seems to be around 0.5 to 1.0 degrees negative on all 4 wheels. This can be achieved by dropping ride height by around 15mm all around if this is not a concern on your local roads from a clearance perspective. If you have gone to stiffer springs as in step 3 the number of times you will bottom out on the bump stops is actually less so it really only around clearance over drive ways and speed bumps that you have to worry about. If you dont want to drop ride height then you can modify the upper front arms and lower rear wishbones to achieve the same affect.

Modifications beyond the above are really only if going for track performance improvements and these improvements are small and the ride quality deterioration starts to get significant. My track times on a full race setup versus the setup above are only marginally quicker, the real reason you go stiffer on the track is for better control at the limit so if you get into trouble you have more chance of getting out of it. You also start running into the Elans ultimate handling problem in that you need to increase the track to take advantage of any extra grip generated otherwise you end up on 2 wheels in the corners when the driver is on the outside and at that point you into the realm of motorbike handling !! The only reason you ever need to fit wide tyres to an Elan is if you go to a much wider track and big flares to accomodate it.

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PostPost by: miked » Fri Jan 06, 2006 12:57 pm

Geoff,

I dont know very much about all the handing stuff but I had the same problem when I did my S4. I had CN springs on the front. The car sat up funny at the front. The springs were a mother to fit to the shocker. I talked to TTR and got some of his fast road springs and also obtained some adujstable dampers/platform shocks from AVO. I then set the ride height to the manual description. If you dont have that page, email me and I will send it. The TTR spring were inches shorter than the stock standard CN ones.

The height was set up quite easy. I still have my original rear standard springs which are not half bad (for normal road use) with the adjustable inserts. Will do the 2.25 inch business on the rear for project car I am doing and some of the other advice. Some cracking advice on this thread!

Mike
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PostPost by: type26owner » Fri Jan 06, 2006 2:00 pm

The fast road spring setup gives a just slightly stiffer ride but not as stiff as new a Corvette, SRT4 or Maserati Biturbo to name a few. Because the car is so light the amount of high frequency vibrations which get transmitted to the passengers is going to be greater then with heavier cars. I left in the rubber pivot bushings on the suspension for this very reason to lessen the ampiltude. If you've replaced the the rubber ones with poly bushings then you get really get shaken. Putting poly bushings on a road usage Elan is a dumb move IMHO.

The RE92 tires set to 20psi give me a compromise I can live with. Stiffened sidewalls to allow fantastic dry grip when they are hot but a low enough pressure which also makes it a cushy complaint ride too. :D They do suck on wet roads though.
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PostPost by: miked » Fri Jan 06, 2006 2:06 pm

Keith,

I never mentioned Poly', did not pass my lips. Honest Guv :lol: !
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PostPost by: Mohe » Fri Jan 06, 2006 2:28 pm

I am so impressed with both the wealth of knowledge and everyone's willingness to share it.

I certainly did tighten up the suspension with the chassis sitting on some crates and the wheels hanging in the air so I will try the loosen, bounce, re-tighten route first of all.

Thank you everyone for your thoughts. I'll update you next week to add a little news.

Mohe
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PostPost by: type26owner » Fri Jan 06, 2006 2:54 pm

Geoff,
I have cut open the rubber bushings to see if they are fully bonded to the inner and outer steel shells. They are only bonded to the inner one and will slide around on the outer shell. Though it's better to tighten the suspension up when it's resting on it's wheels, it's not absolutely required. The rubber will slide around after awhile when under enough stress and self adjust the rubber's position so little stored shearing energy remains.

This is considered the cheap design in the biz. Because they are not fully bonded they tend to wearout more quickly especially on much heavier cars. However, since this car is so light the bushings last a surprisingly long time.
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PostPost by: M100 » Fri Jan 06, 2006 9:34 pm

type26owner wrote:I have cut open the rubber bushings to see if they are fully bonded to the inner and outer steel shells. They are only bonded to the inner one and will slide around on the outer shell.


About 10 years ago a mate with a Caterham had a problem with the car riding higher than it should after a rebuild. I mentioned that the pivot bolts should be tightened with the car at normal ride height (he thought they pivoted on the steel inner) I split one of his used wishbone bushes and the rubber was definitely bonded to both the inner and outer sleeve. (the elan front wishbone inners are the same bush)

I can't ever recall seeing a production rubber bush that wasn't bonded on both the inner and outer face. The polyurethane ones I've come across have neither side bonded and whilst having a tight interference fit they tend to wear badly from suspension movement as road salt and grit gets into them.
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PostPost by: miked » Sat Jan 07, 2006 4:13 pm

Re: front rubber bushes, I would have thought that they should be bonded to both sufaces otherwise they are going to migrate and end up with the bones laying against the stop washers on the end of the pivot pins. Whilst they are there to save the day I am pretty sure the that are not meant to ride on the washers. This did happen to me. They moved and were showing rubbers puddings, frightening. Brand new and day out around Oulton Park. I think the old bushes must have been far superior. I chatted with Susan Miller about this and she said that when Mick used to do a restoration and the car returned the next year for MOT prep' that out of embarassment he would change bushes for no cost. Thats why he went to the softer compound poly' with top hat section, I believe.
I have some old rear bones in the shed and when I pushed out the bushes (which are likely decades old) they seem far better quality and more bonded than the new ones.

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PostPost by: type26owner » Sat Jan 07, 2006 4:48 pm

Mike,
The unbonded bushings are not suppose to be loose by any means. There is a large interference fit and the friction coefficient is nearly 1 if memory serves me well. You do not want to spray these bushings with any type of penetrating hydrocarbon lubricant though.

Don't know if there are multiple sources manufacturing these pieces or not. If there are then that explains why some are bonded and some are not. To be safe only tighten up the suspension bits when it's resting on it's wheels.

M100,
The real problem with a poly bushing is the friction coefficient. They have the same value as the typical brake pad does. Lubrication is required. The ones that have moly di-sulfide impregnated in them are not all that great either. Dry-film lubricants only work by shearing through the crystaline structure. Once it's sheared the onetime it no long has the same slippery property. In otherwords, they wearout and stop working.

Geoff,
You have to be a little careful reading the Workshop Manual. It poorly describes where to measure the front ride height. Ignore what it says and measure from the bottom of the chassis just adjacient to the fulcrum stud to the ground. This for the stock chassis. The tire size used back then is no longer commonly available. After doing some research I found out it was 23" in diameter. You'll have to do the math to figure out the right height for your application. Whatever that value works out to be on the front ride height then apply the same value to the rear. If it's slightly positive camber on the front then I can tell you it's very close to being correct. My guess the rear ride height is too low because the bottom edge of the body should be level to the ground.

Of course the settings are always done when the car is fully laden. Ignore what is does when it's not.
Last edited by type26owner on Sat Jan 07, 2006 5:15 pm, edited 5 times in total.
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