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Discussion Starter #1
Any easy way of increasing wheelbase for an Exige? Without extensive works?

The Exige is very unstable at high speed corners, this could be due to short wheelbase and not the downforce. At stock bodywork, Exige should already have more downforce than S2000 or RX8. But at high speed corners Exige is lacking of stability that an S2000 or RX8 has.
 

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No not without extensive fab work.

While I actually like the idea of an extended wheelbase that is typically for car with lots of power aero etc.

I'll bet your issue is corrected with suspension tweaking, aero, and of course driver ;)
 

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Less is Better
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Although the wheelbase of the platform has been increased by Lotus, Hennessy, and Tesla, the issues you are experiencing are most likely much easier to fix than a rear sub-frame and clam replacement.

Start with the basics. Is the car aligned correctly, are the tires in good shape and wheels balanced, are all of the body and under panels in good shape? How are the suspension links and bushings? If all that is covered, then look at damage to the suspension mounting points.

A short wheelbase makes the car "choppy" but it shouldn't feel unstable at high speeds if everything is in good shape.
 

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You asked about the single most difficult thing to do to a chassis…lengthen it. I have a stock Cup 260 and go regularly over 200-kph on the track I frequent. My car is very stable at those speeds. My car is also very responsive in the turns – thanks to the shot wheelbase. There must be something else wrong with your car…my guess is either you have tons of front and/or rear camber (approaching 3.0 degrees) and/or your suspension bushings, ball joints, etc. are worn out. Check your suspension out thoroughly.
 

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Without getting into a long-winded technical discussion, I'll just say "ditto" to what they said and to that add that if all three cars are "right" the superiority of the Lotus should increase with additional speed due to aerodynamic advantages. Besides camber and toe, you might also check rake. If the car is wedging air. As the speed goes up, so does the car!
Good Luck
 

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Discussion Starter #6
Great info guys, will check those mentioned things up and try again. Will report back if solved my problem or faster lap time :)
 

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The rake of your car (aero) could easily be the cause…I didn’t think of that.

A known issue with our cars is the rear suspension inner toe link bolts. The inner bolts fail. If you don’t have that shear link between those two inner toe link bolts, physically remove those two bolts and inspect them. If your rear toe is changing, it will feel like the car is unstable.
 

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I don't think aero is your problem. The corners where you spun aren't fast enough. It could be an alignment issue, but I have to say that it sounds like you're lifting mid-corner. Maybe I'm wrong about that, but it sure sounds and looks to me like technique is the culprit.
 

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Seeing that video, I'd say you have really bad tires (not DOT race) and way over inflated. You are going way too slow for that car to be spinning out that soon.
 

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Alignment, ride heights, cold tires would be the first things to check and correct. Also, it looks like you may be pushing beyond the tire's capabilities which is related directly to the three things I mentioned in the first sentence. Another thing to consider is that if you are on the limit/edge and your engine rpm is near the cam change point you can experience unwanted and disturbing torque inputs while cornering.
 

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Discussion Starter #12
Great info, I was running Dunlop Z1 Star Spec. Initially running 25/28psi but can't find any grip. Hence inflated to 30/33psi and immediately reduced lap time by 4 seconds.

Right height was near stock or slightly lower. Camber around 2.5' F/R.

I'm gonna try lower the car by another 5-10mm and reduce the rear camber.

Alignment, ride heights, cold tires would be the first things to check and correct. Also, it looks like you may be pushing beyond the tire's capabilities which is related directly to the three things I mentioned in the first sentence. Another thing to consider is that if you are on the limit/edge and your engine rpm is near the cam change point you can experience unwanted and disturbing torque inputs while cornering.


Sent from my GT-I9300 using AutoGuide.Com Free App
 

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Definitely not the fault of your wheelbase…Your steering wheel shows very little inputs up at high speeds and that is where wheelbase comes into play. All of your spins and near spins came in the braking zone of right hand corners so my guess is that your right rear brake caliper is rusted solid (your brake piston is not moving)…it could be your left rear...check them both.
 

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Your car is maybe not stable as a Porsche, but typically, not bad either. If the car is unstable, look your suspension bushing (mostly the rear top wishbone) and you can install solid bushing (spherical bearing, see sector111), put the alignment at zero front and rear, and not too much camber, and it should be not too bad. If you have a LSD, remove it! For long and high speed track, you don't need it, with a LSD, the car is more prone to unstability, the back of the car is fighting with the front. If you spin too much, be certain to install helper spring at the rear suspension. With all that, you car will be a little bit slower on short track, but more stable at high speed track.

And of course, on your car, you need to be gentle with the steering! The car is still short and dynamic.
 

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Discussion Starter #15
Your car is maybe not stable as a Porsche, but typically, not bad either. If the car is unstable, look your suspension bushing (mostly the rear top wishbone) and you can install solid bushing (spherical bearing, see sector111), put the alignment at zero front and rear, and not too much camber, and it should be not too bad. If you have a LSD, remove it! For long and high speed track, you don't need it, with a LSD, the car is more prone to unstability, the back of the car is fighting with the front. If you spin too much, be certain to install helper spring at the rear suspension. With all that, you car will be a little bit slower on short track, but more stable at high speed track.

And of course, on your car, you need to be gentle with the steering! The car is still short and dynamic.
We don't need an LSD???

I've got an ATS 1.8way carbon LSD, the one that used in Japan Outer Plus Ti Racing Exige.

I've improve my track time quite a lot with this LSD.
 

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We don't need an LSD???

I've got an ATS 1.8way carbon LSD, the one that used in Japan Outer Plus Ti Racing Exige.

I've improve my track time quite a lot with this LSD.
"Eise/Europa" is wrong about that, of course. Limited slip stabilizes a car, increasing understeer tendancy.
 

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Wrong or not wrong?

LSD is required if your tires overspin. On high speed track, the car don't have enought power to spin the tires, and the added traction added by the LSD is useless if you don't spin!

I am not here to argue more than that. But I have a friend who after several trial with his car and many plays on suspension with Nitron double or triple, he just removed to LSD and he was please with that change for hugh speed track. He was affraid about the car saying that the car is not stable and I am affraid to slide off the track. At the beginning I said to him to not install a LSD, and now he know why. The guy was a very fast driver. But now the car spin and is slower on slow track.

But I am probably wrong, but still, I am one of the faster Elise in Quebec on track with only a REV300, and typically within the 2 faster car during the lapping day I am doing here figthing with GT3, Ferrari, Corvette. And no LSD because I decided to have a more stable car and lost one second of traction. I did race with a old Lotus Europa, and after many trials, I did better and safer result without LSD because I was able to push harder of the entry and in the curve, but with less traction at exit.

But if I was doing autocross, for sure, my car would be equipped with a LSD for sure.

My 1 cent
 

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"Eise/Europa" is wrong about that, of course. Limited slip stabilizes a car, increasing understeer tendancy.
Pretty comprehensive statement Me73, and it is not correct. I have yet to find a LSD that improves corner entry, and tuning the engagement to minimize power on/off effects on the car's cornering stability is time consuming and difficult ($$$). Yes, they tend to increase understeer tendency.

Lots of pure mechanical grip with an open diff gives the most consistent spirited driving experience. At the risk of over simplifying a complex situation, I would say only go to a LSD to cover for a lack of mechanical grip and/or really big power. Let your right foot and buttocks/brain interface act as an active differential.:)

BTW -- Just for reference, I am well into my seventh decade, more forgetful, calmer, and slower than before but my CV includes several years as a ride and handling engineer for a major auto company and almost 30 years of driving real race cars in the U.S. and the U.K. (with and without open diffs).
 

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Pretty comprehensive statement Me73, and it is not correct. I have yet to find a LSD that improves corner entry, and tuning the engagement to minimize power on/off effects on the car's cornering stability is time consuming and difficult ($$$). Yes, they tend to increase understeer tendency.

Lots of pure mechanical grip with an open diff gives the most consistent spirited driving experience. At the risk of over simplifying a complex situation, I would say only go to a LSD to cover for a lack of mechanical grip and/or really big power. Let your right foot and buttocks/brain interface act as an active differential.:)

BTW -- Just for reference, I am well into my seventh decade, more forgetful, calmer, and slower than before but my CV includes several years as a ride and handling engineer for a major auto company and almost 30 years of driving real race cars in the U.S. and the U.K. (with and without open diffs).
The statement in dispute was that LSD made the car more unstable. It's incorrect. If you went through the same mechanical engineering classes that I did, you know that understeer is a dynamic condition of stability. The tendancy to swap ends is due to dynamic instability.

I stand by my statement.
 
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