Lotus Elan

rear antiroll bar

PostPost by: redcarandco » Sat Jan 30, 2016 10:40 am

Hello happy tax payers....I am sitting in garage during wind is blowing (strongly) outside and as I am making an inventory of parts I have refound with the car I am rebuilding.(will be completely done for end of july)..and doing this I have found the rear antiroll bar which is for me a real mistery...I am racing elans for more than 40 years and have never used this feature...As I am a client of Tony Thompson for everything (unless the underpants...) ,he has always told me not to use this feature...As he is great pilot I do agree without further thinking....But this time once for all I would like to have opinions of the lotus community where I guess many of you have raced this feature..... pro or anti rear bar.???????????....Opinion of users...Very best regards to all
Roger from belgium
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PostPost by: stevebroad » Sat Jan 30, 2016 4:32 pm

What are you trying to achieve with a rear ARB?
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PostPost by: redcarandco » Sat Jan 30, 2016 5:33 pm

I was just asking to myself when looking at ARB of the car I am rebuilding...is it worthy to use one on my actual race elan I use in historic races...?
Roger
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PostPost by: rgh0 » Sat Jan 30, 2016 11:20 pm

I think you can setup an Elan both with and without a rear anti roll bar depending on your personal preference

From reports I have read they were used in the original 26R's by some people and not by others. TTR certainly does not favour them but he sets up his cars and the rear end springs to be very hard.

I have raced against an Elan with a rear bar and it certainly handled as well or better than mine but it was on a track I did not know and it was his home track.

I suspect with modern sticky tyres you either need a rear bar with soft to mid- range track suspension springing i.e. 150 to 200 lb/in front and 110 to 150 rears and 7/8th front bar. You probably dont need it with hard track suspension of say 300 lb/in fronts/ 180 to 200 lb/in rears and 1 inch front bar.

The other alternative is to space down the rear rubber springs suitably so they come into play earlier and effectively give you a progressive rising rate rear spring which acts similarly to the anti roll bar. This is what I do with the relatively soft suspension set up on my Elan.

I wish I had the time and money to experiment more with this sort of stuff :D
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PostPost by: redcarandco » Sun Jan 31, 2016 8:09 am

Dear Rohan I am not far from your set up for modern tyres of course The problem is that french federation is building a full FIA championship of 6 races for Pre 65 GT and tourism what is a splendid thing but in FIA rules we are obliged to race with Dunlop CR 65 and there is our" problem" because experiment shows us that this set up is far from being efficient for these tyres All 1965 period drivers (youngest still alive is 92 years old now...) we have met give us sets I dare not use as they are so "light" but who knows and I think you are right .....try try and try again it will come something out of that...We are lucky in south of belgium to have several tracks at small distances (spa/ Zolder/ croix en ternois/ mettet.....)So I think that when sun will be back.......
Best regards
Roger
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PostPost by: rgh0 » Sun Jan 31, 2016 9:22 am

Foir Dunlop historic tyres I would try a soft race setup maybe - 150lb front and 110 lb rear and 3/4 front bar and then work from there.

If it is still sitting down to much in the outside rear in corners try spacing down the rear Aeon rubber springs, after that try a rear roll bar.

but in the end it is really personal preference

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Rohan
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PostPost by: redcarandco » Sun Jan 31, 2016 12:38 pm

My engine builder (a former racer...)told me exactly the same thing so I am going to do so...I suppose that what you call aeon rubber spring is what we use to call bumpstop but in more sophisticated feature...As a very old friend of mine used to say..." trying without prejudice is the main street to success...best regards
Roger
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PostPost by: elandoc » Sun Feb 28, 2016 11:45 am

Let me quickly add that the single best improvement I ever did to my (tarmac rally) Elan's handling was taking the rear bar OFF. Instantly became much more drivable - I'm talking 2 seconds a lap.
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PostPost by: toomspj » Sun Feb 28, 2016 8:35 pm

I raced in road sports on Yokohama rubber without rear arb using approx 300# f and 200# rear. A major issue in that set up was rear wheel lifting as we weren't allowed limited slip diffs.

I now run an FIA car on Dunlops M tyres with CR65 tread. I was told to run it soft but car just wasn't competitive. I ended up with a very similar set up to the roadsports car 300+# Front and 180 Rear. It slides around just fine with a Salisbury type lsd

The soft set up was fine - just depends how competitive you want to be. The downside of going so hard on the old fashioned tyres is that if there's a sprinkle of rain the car is very twitchy indeed! On the other hand in the dry you can drift the car around like it's a Kart.

Like Rohan I'd love to have the time and money to test a range of set ups including a rear arb - need a professional team to do that and a lot more money than I've got.

Be interested to hear what you find if you try the rear bar.

Paul
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PostPost by: redcarandco » Mon Mar 07, 2016 11:44 am

Dear paul,I am now absolutely convinced you are not far from being in the right direction...Depending of weather conditions it has took a little bit of time to have these solutions tested on a small french track in north of france.... the results were quite surprising...Car is 590 kg (1180lb)with 10 liters gas but I am 100kg so Suspension set up was 200 lbs rear and 320 front(to cope driver over weight) results (resumed) are .......fastest is this set up with yokohama w/o rab but but but but the second best result is Dunlop with the same set up (we just added a little bit more toe-in at rear with cr65 (1 mm per wheel)and I can say because have tried numerous laps that rab is a thing of danger(at least 7 spins in a 7 laps run) even with so soft set up that rear wheel disappeared in wing while cornering hard and chrono were disgusting 2 to 3 seconds slower per mile.(even with ultra soft new toyo we use for hill climb)....The big diff between dunlop and road tyres (races tyres disguised in fact) is lack of consistency for cr65 and they also requires a serious ""no fear of sliding""sens And concerning RAD we decided to throw it in the trash before living the track.....
Roger
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PostPost by: toomspj » Mon Mar 07, 2016 1:57 pm

Roger

Thanks for the feedback. Based on that, I won't spend any time testing a rear a/r bar (I wasn't planning to in any case). The one thing I had wondered about was if I've got a 100 litre tank in the back, for long distance race could it be useful then?

I love sliding the Dunlops about, but it does take a different mindset - it's amazing how sideways you can get and still keep moving forwards. I now have to remind myself when I get into a Yoko rubbered car not to try and do the same!

As for your lack of consistency on Dunlops, try raising the pressures. In my opinion they need to be run much harder than the Yoko - in fact I found there was a threshold at which they became consistent in the way they behaved and you could trust what happens when you chuck the car in.

Paul
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PostPost by: redcarandco » Mon Mar 07, 2016 3:02 pm

I must recognize that in this session we have lost long long hours in modifying set up and this prevent us from testing tyres pressures...I think we were efficient with yoko pressure (+/- 1;8 to 2.0 kg depending track T°...)but no time enough to begin with Dunlop... Test days are always too short...but chatting around numerous wine bottles last year at nurburgring with lotus elan former drivers it seems that nowadays CR 65 are much more efficient than they were 20 years ago and they told me as a state secret they used to inflate to 2.2 kg in normally warm weather conditions but they also recognized that they lied to all others european contenders of this time saying they used 1.5 max so when were they telling the truth????
Roger
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PostPost by: elansprint71 » Sun Mar 20, 2016 9:52 pm

"Historic" racing, eh? I've spent the last 40+years a photographer of Sports Car racing and am not sure how much longer I can be bothered.
Why don't you folks just fit 4wd, triple-turbo, 8-speed sequential gear boxes, 20" wide tyres and four-litre twin-cams?
T-T hot-rods are one thing but it is just getting silly, with all the cheque-book racers ruining our sport.
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PostPost by: Chancer » Sun Mar 20, 2016 10:40 pm

Roger, next time you are testing at Croix en Ternois please let me know by PM because I would love to come along, I used to test there myself when I lived in the South of England and it gave me a taste for this area and I subsequently moved here, I'm ashamed to say I have only been back to Croix one time in my 11 years and its high time I did it more often, it would give me the impetus I need to restore my Elan or recommission my Caterham Blackbird, my last outing with that was at Croix in 2003, how time flies.

I only live maybe 30 minutes from Croix, it would be good to meet you and reignite my passion.

Je parle Français également!

A bientôt
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PostPost by: toomspj » Mon Apr 11, 2016 9:28 pm

I don't understand your comment about "Historic Racing". The Elans in period used rear anti roll bars at times and a standard 26R chassis and rear wishbones have the mounting points fitted for the a/r bar. So using one would be historically correct (although it wasn't commonly done as far as I know).
Dunlop CR 65 tyres are the standard period tyre specified for most historic racing.
And as for "cheque book racing" I think the discussion is quite clearly that we don't want to spend money on testing.
I kind of like the adage "if you can't say something nice, ..,,,,"

Keep smiling and we'll keep racing!

Paul

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