50 replies to this topic

[chris_uk]

some of the aero testing i did the other year. 

 

 

@120mph 

 

 

 

i would remove the original front undertray and make a new full one out of 12mm marine ply, then mount it underneath your current one. I would mount it on the original rear 3 bolts and the 6 m5's on the sides, then for the front part i would use some kind of brace from the crashbox. 

you will need to make it strong enough to stand on.. when i made my first one i stood on it, circa 14 stone at the time.. and at 145mph the wind pulled it down enough that when i stopped i couldnt see anything wrong when i looked and it was only above 60mph did it start to bend down. it turned out that the fixings i had used came through the clam.  

 

now my airdam is bolted to the clam with M8 bolts and huge spreader washers, and the splitter is just attached to that via rivnuts into the carbon.. i didn't think it would be strong enough but i can stand on it and its fine. I will brace it from the tow eye at some point. 

 

this is as big as my splitters are. 

 

[swast4]

Cheers Chris, but I don't understand why your splitter is so small, if I take my undertray off for a template then do I leave my original splitter on and bolt through. If I'm using the original 3 bolts at the back then the splitter will be a lot bigger (& heavier) than yours.

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[chris_uk]

there is a space built into my airdam, you can kind of see it here. 

 

 

 

[swast4]

OK cool, I get it now

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[Captain Vimes]

For a track only suspension setup I’d start with a full setup that is known to work well on a race car. Ie. copy a setup from a front running Elise Race car, or closer to home have a chat to Zoobeef about his experience?

From there roll bars should just be a case of tweaking the balance according to personal preference and track requirements.

In the Caterham graduates championship there is a free choice of roll bars and geo. You’d be surprised how different the setups can be from one car to the next but the lap times are the same... you can gain in some places but it’ll compromise another.

It’s all all a compromise but you need to get a basic setup that works first and then measure the effect of each change from there.

[Pidgeon]

Having just returned from three circuits in France, my memory is refreshed that these cars don't give away much to anything from the Lotus stable.  You must have a good basic set up and then it's driver ability.  IMO time and money spent on spoilers and splitters is wasted.

[Nev]

Having just returned from three circuits in France, my memory is refreshed that these cars don't give away much to anything from the Lotus stable.  You must have a good basic set up and then it's driver ability.  IMO time and money spent on spoilers and splitters is wasted.

 

I agree, usually the issue is that various unknown and non standard parts are installed on the cars by previous + current owners, modified wheels + tyres + suspension + ride heights + ARBs + hard/worn bushes etc can quickly mount up to ruin the handling.

Edited by Nev, 27 August 2019 - 08:49 AM.

[Exmantaa]

Having just returned from three circuits in France, my memory is refreshed that these cars don't give away much to anything from the Lotus stable.  You must have a good basic set up and then it's driver ability.  IMO time and money spent on spoilers and splitters is wasted.

 
Spoilers and splitters will not help if something is off, so spend your time well to get the basics right and get a stable car on track:
 
- Ride height setting (with some rake) on decent dampers + track springs and your track tires. Take care of sufficient bump / droop travel. (~40/60 Will need helper springs at the rear, maybe fronts too for stiff springs)
- Fit reinforced toe link set. => check the bump steer curves at the ride height, fronts too if you can.
- Set GEO for a decent, well know track set-up for your tires; sufficient negative camber settings (Track maybe -1.3°F, -2.8°R, or more), slightly Toe-out Front , sufficient Toe-in Rear.
- Track brake pads & fresh fluid are OK with the stock brakes; ABS Off (front sensor only to keep the rear proportioning function), or use the 4 channel Lotus. Fit some brake cooling hoses!
 
- Start with dampers in a middle setting. (I normally start around -12clicks F /-14 clicks R from full hard on NTR's that have ~22 clicks.) and adjust from there.

- Stiffer ARB (a 7/8", maybe a 1") will help to keep the car level in fast corners and your inside rear on the track.

From there you can make small adjustments to your liking.
 
If you keep locking the fronts too early, even with the rear dampers softened, maybe something is not right in your brake set-up. I had this too and tried everything. Finally came to the conclusion that it had to be something off in my master cylinder, as the whole caliper, pad & damper set-up worked perfectly when I swapped everything over onto another car...

[Nev]

I disagree about putting a stiffer FARB on, unless you considerably increase the rear spring LB'age.  Even then, the geometry is designed to roll and add grip, roll helps stops sudden snap away too.

Edited by Nev, 27 August 2019 - 02:22 PM.

[chris_uk]

I disagree about putting a stiffer FARB on, unless you considerably increase the rear spring LB'age.  Even then, the geometry is designed to roll and add grip, roll helps stops sudden snap away too.

 

and a softer roll allows the suspension to become overwhelmed and cause over steer.. 

[Exmantaa]

The Lotus chassis is designed to roll and grip, but you will need to stiffen up the suspension to get the same suspension movement at much higher track loads. (and as said; check the bumpsteer curves at the track ride height...)