Positive Rake

[Sparxy]

All,

Following up on a previous post about improving downforce I have a further question.

I'm going for the front splitter and I want to lower the car a little at the front get a bit of positive rake. Without buying a full set of adjustable Nitrons for a grand (eeeek) are there any tried and tested methods I can use on standard shocks?

[Scuffers]

Sparxy said:

All,

Following up on a previous post about improving downforce I have a further question.

I'm going for the front splitter and I want to lower the car a little at the front get a bit of positive rake. Without buying a full set of adjustable Nitrons for a grand (eeeek) are there any tried and tested methods I can use on standard shocks?

you can get lowered damper brackets...

http://www.eliseparts.com/shop/index.php?main_page...

[Sparxy]

Unfortunately those are for the S1 :-(

[Scuffers]

Sparxy said:

Unfortunately those are for the S1 :-(

so?
they will fit S2's... (NOT yota ones)

[Sparxy]

I take it you have or you know someone who has done that then? Sorry to sound so sceptical but on the website it says S1 only!

[Altrezia]

Sparxy said:

I take it you have or you know someone who has done that then? Sorry to sound so sceptical but on the website it says S1 only!

Hehe, scuffers is probably right. He fiddles with plastic cars.

[Stan.]

You can machine additional circlip grooves in the shock body to raise spring seat. I machined two on the back and three on the front at a spacing of 5mm to the same dimension as originals. Each groove equates to about 1/2" difference in ride height. I now have a ride height of 120/130mm instead of 160/160.

Positives -

High speed stability improved dramatically, less turbulence in cabin at motorway speeds, less front wheel lock up under braking,noticeable reduction in understeer, rides bumps/drains/white lines a lot better due to less spring pre load giving slightly softer ride and of course due to a lower centre of gravity just goes around bends a hell of a lot quicker!

Negatives -

Due to (slightly) less droop on rears you'll notice an increase in inside rear wheel loosing traction out of tight or slippery bends.

Here's a link to how it's done -

http://www.boefabrication.com/lotusElise/shockSurg...

[Sparxy]

Thanks, that's what I was looking for!

Just need to find someone to machine them now ;-)

[AdrianR]

Surely if you move the spring seat "up" the shock you are reducing the effective travel, so if you don't change the spring rate you will end up on the bump stops earlier for the same force (i.e. at a lower cornering speed or on a smoother road)?

Brackets seem like a better bet to me.

AdrianR

[Altrezia]

AdrianR said:

Surely if you move the spring seat "up" the shock you are reducing the effective travel, so if you don't change the spring rate you will end up on the bump stops earlier for the same force (i.e. at a lower cornering speed or on a smoother road)?

Brackets seem like a better bet to me.

AdrianR

Yep.

[Scuffers]

Altrezia said:

AdrianR said:

Surely if you move the spring seat "up" the shock you are reducing the effective travel, so if you don't change the spring rate you will end up on the bump stops earlier for the same force (i.e. at a lower cornering speed or on a smoother road)?

Brackets seem like a better bet to me.

AdrianR

Yep.

double yup!

[Sparxy]

OK maybe I won't be doing that then!

Did you all look at the website article of what they do?

[C43]

Machining the dampers to drop the ride heights may not be all that bad. You will hit the bump stop earlier but that may not be a problem. If in normal use the car only gets to within 10mm of the bump rubber then if you drop the ride height in this way and get to within 5mm of the bump rubber it will still obviously make no difference to the overall spring rate. In either case the bump rubber is doing nothing.

To see how much travel you are getting on the road you could fit a data logger and suspension pots...lot of cost and hastle. Of you could put a ty wrap around the damper tube. Go out for a driver and then see much much it has moved up the damper shaft at the end of the drive. I don't know if the bump rubbers on these cars are external or internal. If they are external it will be easy to see if the ty wrap has come into contact with the bump rubber. If they are intermal you will have to take the damper off the car and push it by hand and measure how much travel you get before you hit the bump rubber.

I will have a look at the possibility of doing it on my Europa. I want to drop the ride heights but I don't want to stiffen the car up any more with Nitrons and stiff springs as the roads round my way are rubbish.

cheers

C43

[Scuffers]

C43 said:

Machining the dampers to drop the ride heights may not be all that bad. You will hit the bump stop earlier but that may not be a problem. If in normal use the car only gets to within 10mm of the bump rubber then if you drop the ride height in this way and get to within 5mm of the bump rubber it will still obviously make no difference to the overall spring rate. In either case the bump rubber is doing nothing.

I know where your comming from but that's not the point or the case here...

the dampers on the S1 are short on travel as it is, moving the static point 10mm is quite drastic when you are already well short on bump travel to start with.

Even a road-only std car will hit the bump rubbers in everyday driving, this is all part f the base setup, moving this by 10mm will definitly have an effect on this, and it's not going to be positive.

the other bit to consider here is that the front suspencion is very much a falling rate setup with the damper fitted as it is, so the lower the car rides, the lower the effective wheel rate is (in effect, making the spring softer), add this lot all up and you have a problem, it's not liek the Elise is over-sprung in the first place...

[C43]

fiar enough Scuffer. I remember that the early Esprits were well into the bump rubbers on country roads and this made them very crashy. Do you know if the S2 or Europa are the same? Also any idea how much falling rate they have put into the suspension?

[Sparxy]

I think I may already have hit the bump rubbers once and I'd like to avoid doing it again. It was horrible! I was accelerating hard round a left hand bend so the rear right was sitting down quite a lot. Then I hit the biggest bump in the road and the noise was quite startling.

Are we saying that the best course of action is to save up for some Nitrons?

[C43]

sounds like it. I spoke to someone who had put Nitrons on their Europa yesterday and said it was much better.

[Thorburn]

Sparxy said:

I think I may already have hit the bump rubbers once and I'd like to avoid doing it again. It was horrible! I was accelerating hard round a left hand bend so the rear right was sitting down quite a lot. Then I hit the biggest bump in the road and the noise was quite startling.

Yep, if it happens you definately know about it! I hit them HARD in my old MX-5 going through a compression at speed and the shock it sent up through my spine meant when I got out the car I could barely walk.

[Scuffers]

Sparxy said:

I think I may already have hit the bump rubbers once and I'd like to avoid doing it again. It was horrible! I was accelerating hard round a left hand bend so the rear right was sitting down quite a lot. Then I hit the biggest bump in the road and the noise was quite startling.

Are we saying that the best course of action is to save up for some Nitrons?

not uless you want to spend the money...

Just use lowered damper brackets, job done.

[Sparxy]

Ok ok Scuffers!! ;-)

I'll get a set of those brackets from eliseparts and if they don;t fit I'm coming round yours to let you fit them ;-)