Suspension height for UK roads and speed bumps/humps......

[berni29]

Hi Guys

Edit: its a +2

I have my rolling (Zetec with Sierra Running gear) ready to plonk the body on, but before I do I need to set the geometry and bump steer. To do so I need to decide on a ride height that makes sense given the many many many road calming, but driver and resident enraging, speed humps and pillows that proliferate around the part of London where I live.

I was going to release all 4 springs and set the lower wishbones (both front and rear) to flat, but am worried that the car will be too low. Does anyone know what minimum angle I want in order to be able to negotiate our cr*p roads without whacking the nose of the car? I do not want the car looking like a +2 4*4.

I am not so worried about the typical Spyder ground clearance issues because I am running a flat raceline sump although the roll bar does go under it. I am also running 14" wheels with a 175/70 tyre which is the same rolling circumference as the standard 165 82"s. And a standard Lotus exhaust.

Thoughts please!

Berni

[Spyder fan]

Berni,
Are your wheels 14x6 minilite style? If so I would suggest fitting 175/70/14 tyres this gives a virtually identical diameter to the original but not available 165/82/13 tyres fitted to the 13 inch wheels.

The 70 profile will give a bit of comfort over rough roads and the 175 width will give a good compromise between contact patch and clearance for the inner wing. 185 profile tyres have a habit of rubbing the inner wing. I currently have 185/65/14 tyres which are being changed for 175/70/14 for these reasons. Originally Spyder fitted 185/60/14 totally wrong diameter which didn’t fill the arch visually and made ground clearance worse.

The biggest grounding issue for Zetec cars was/is the awful design of exhaust manifold, but you say you are using an original type manifold that takes the normal route, so this won’t be a problem.

I have my suspension set parallel and don’t have any grounding out problems and the there are god awful roads and speed humps in this part of Kent too.

[berni29]

At the tyre fitters.

Hello Alan

Thank you for the reply, just what I needed to know.

Yes the wheels are 14" minilite copies, and they are running 175/70's as suggested. I cannot remember what tyre exactly, but I asked for it to have a lightweight construction (not reinforced) for a light Lotus.

The wheels are off a classic Alfa. I cannot remember the exact details but they are 14" 6J offset is around 37 or 38. The reason for the higher offset is so that I can space them to the correct track as standard, I cannot bear (personal thing) the stick out wheel look. The 22 offset Spyder use is not for me. I have some hub centric rings to correct the Alfa poke down to the Ford poke.

My 2nd level laser just arrived from Amazon, so I will start setting the chassis up for the geo later today I hope.

Thanks again

Berni

[Andy8421]

Berni,

There's a lot of subtle stuff going on with the front suspension ride height, I wouldn't want to adjust it away from the Lotus recommended height without understanding the implications.

The car was designed to have the lower wishbone parallel to the road surface under normal driving conditions (if I recall correctly, the car has to be loaded to simulate driver / passenger to achieve this). I have attached a diagram below, but if my old brain is up to it, raising the ride height introduces positive camber.

Again from memory, the suspension is designed to introduce negative camber when loaded, so that in a corner as the body rolls the tyre remains perpendicular to the road.

Probably best to speak to someone who knows what they are talking about, but it would be a shame to sacrifice the handling for the sake of a few speed bumps.

front suspension diag.jpg (59.46 KiB) Viewed 240 times

[Spyder fan]

IMG_5470.jpg

Hello Alan

SNIP!


The wheels are off a classic Alfa. I cannot remember the exact details but they are 14" 6J offset is around 37 or 38. The reason for the higher offset is so that I can space them to the correct track as standard, I cannot bear (personal thing) the stick out wheel look. The 22 offset Spyder use is not for me. I have some hub centric rings to correct the Alfa poke down to the Ford poke.



Thanks again

Berni

Thanks Berni,
I know what you mean regarding the wheel offset, good to see you have the 175/70/14's good choice!

My S4 wheels have a similar offset to your Alfa wheels, I have just changed the tyres on that for 165/70/14 and it looks very good. Tomorrow I'm going to swap a couple of wheels over between my +2 and S4 to see what they look like on the front. I know what you mean regarding the Spyder Minilite pattern sticking out too far and strangely enough Sean (Spyder Cars MD) mentioned to me the other week that it was one of his dislikes as well. I'm hoping to have some time to play tomorrow, so maybe I will get a few photos.

[Spyder fan]

Berni,

There's a lot of subtle stuff going on with the front suspension ride height, I wouldn't want to adjust it away from the Lotus recommended height without understanding the implications.

Andy,
Good information, I think one of Chapmans sayings was "don't make it adjustable or they will adjust it wrong".

Not sure what Berni's wishbones and spring platforms are based upon, but it looks like he is staying parallel

[berni29]

Hi Guys

Interesting information and thoughts thank you.

I am indeed going to stay parallel. I have the Spyder suspension set up, so the front and rear are adjustable for camber, all the platforms adjustable for height and it has adjustable rear A frames for toe.

Will post on here once I have done the geo. I am just researching settings, looking like 1/8 toe in front, 1/16 in rear, and camber not sure about yet prob 0.5 deg -ve.

All the best

Berni