Custom Suspension

[Batfink 201]

Dean blew up his engine and flogged the car He sold it to a mate of his so can get all the measurments

Still cool for saturday

[madaxgt 0]

Great idea be very interested to see it when its done. Agree it would be very good for rallying where a lot of dampers get thrown out due to overheating it may also give room for increased travel and of course all the other reasons.

 

However i see one flaw you will still be using MacPherson struts on the front i.e massive camber gain due to roll. Seems a bit pontless in having great roll centre ,camber control etc if the front stays the same.

 

For an auto design module at uni we decided to do a fancy machpherson strut set up that gives camber loss in bump to negate the gain in roll using the orignal hardpoint loacations. Its a monster go to do FEA etc on it as well, fancy doing a trade of info when were finished???? then the best ever handling 205 may appear

[Adi 0]

i see one flaw you will still be using MacPherson struts on the front i.e massive camber gain due to roll

 

Don't whether you have typed that wrong......but the main problem with any McPherson strut set up is.....there is never enough camber gain in roll. Because there is no top arm (as in double wishbone) the top of the wheel will never move in sufficiently to allow the wheel to change angle. That is why cars like the 205 have to increase the static camber......to ensure the tyre stays flatter during roll.

 

For an auto design module at uni we decided to do a fancy machpherson strut set up that gives camber loss in bump to negate the gain in roll

 

Do you realise that bump travel and roll are the same direction?? The suspension compresses. So how can you have camber loss in bump.....and gain camber in roll??????

 

Seems a bit pontless in having great roll centre ,camber control etc if the front stays the same.

 

2 of the leading hot hatches on the market today are the new Mini and the Honda CTR. Both have the strut suspension up front and multi link (double wishbone with a 5th link) suspension at the rear. Engineers/designers have learned that the front suspension can be compromised to a certain extent......but the better the rear works, the greater the dynamics. In other words......the rear helps the steering thru weight transfer.

[madaxgt 0]

when i write camber gain i mean gain in camber i.e positive which you do get when the car rolls.

 

you can gain camber (from 0 to positive) if the body rolls as it pulls the bottom link inwards and the top moves outwards therefore giving positive camber gain. even f1 cars gain camber in roll but this is offset by the double wishbone setup loosing camber (negative) as the wheel moves up due to compression.

 

Example:If you lift a 205 of the ground and the suspension droops the top of the wheel points outwards yes? if you put 10 elephants in it the wheels would hit the stops and the top of the wheels would point inwards. Hence camber loss in bump or compression.

 

"Do you realise that bump travel and roll are the same direction?? The suspension compresses. So how can you have camber loss in bump.....and gain camber in roll??????"

 

er... not really think u may have got terms mixed up or not understand mine.

 

anyway i agree the 5 link setup is great and does help and is used because it is possible and cheap enough. They still use mac pherson due to cost and space limitations however it isnt the best set up. If they had lots of space and money they would use a double wishbone set up as it would be far superior and that is what our project is; to design a replacement for the macpherson strut setup that controls camber much better utilising the orignal hardpoints. If macpherson was so good they would be using it in ferraris lambos etc and even f1 but it isnt the best for handling just for mass production.

So to get the best handling 205 ever you would want a 5 link or double wishbone rear end with a double wishbone front set up. Voila your 205 is no longer really a 205. No lift of no savage understeer it just grips and probably 4 wheel drifts if set up right.

[M3Evo 0]

I thought they made cars with excellent rear sus and mediocre front so as to make all cars understeer due to the fact that the average numpty doesn't have a clue how to control oversteer, regardless of how good they think they are behind the wheel!

 

I thought the whole point was to haul the top of the wheel in during cornering and the resultant suspension compression. This in turn must mean the compression on bump must also haul the top of the wheel in, giving rise to greater negative camber.

[Adi 0]

when i write camber gain i mean gain in camber i.e positive which you do get when the car rolls.

 

"Camber gain" is generally accepted in engineering terms as gaining -ve camber as this is the angle that keeps the tyre flat whilst cornering.

 

even f1 cars gain camber in roll but this is offset by the double wishbone setup loosing camber (negative) as the wheel moves up due to compression.

 

Do you know what camber thrust is??? Well seeing as you doing a auto design module at uni......it will be easy to find out.

F1 cars don't gain/lose camber during roll.......as there is lateral movement, the tyre is pushed inward on the outside loaded wheel. So giving full grip. This is know as camber thrust.

You will be lucky to "see" any movement of the front suspension on an F1 car. They are set up that rigid to ensure the front roll centre stays as still as possible. That way the steering will act/feel as consistant as possible. Most of movement within the front suspension comes from the tyre.

The rear suspension has got around 25-40mm movement.

 

If macpherson was so good they would be using it in ferraris lambos etc and even f1 but it isnt the best for handling just for mass production

 

I agree 100%.

 

So to get the best handling 205 ever you would want a 5 link or double wishbone rear end with a double wishbone front set up. Voila your 205 is no longer really a 205. No lift of no savage understeer it just grips and probably 4 wheel drifts if set up right.

 

Every road car is a compromise as far as suspension is concerned. So what is ideal and what is usable and cost effective may not be the same. Even Honda used double wishbone of sorts for over 15 years from the mid '80s to the beginning of this decade when things were changed at the front end to a strut set up. They changed simply cos engineers found that by developing the rear suspension and getting the roll centre above that of the front......the handling moved onto the next stage.......and was market leading.

Now fitting a space frame with double wishbones onto the rear of a 205 is nothing new. It has been done for a good few years now. But it is something that is not that complexed to do as there is already a frame set at the rear as standard. At the front however......would take so much money and engineering....and in handling terms......on a FWD car....there is not as much to gain by improving the front suspension......as there is to improving the rear.

 

If you want the ideal 205........you stick the engine behind the centreline and use 4wd......as well as double wishbone all round.

Hang on........hasn't this been done in the '80s??

[Batfink 201]

Hmm Ive been looking at some pictures of caterhams. Full space frame front with double wishbones? wonder if it could be fitted lol

Think I will stick with the rear improvements on this car

 

the fronts are modified anyway. i quote from the person who will do the front work....

 

The standard wishbones are replaced with specially manufactured tubular ones with the pickup points on the front struts modified for improved roll centre location with the low ride height

whatever that means lol