60 replies to this topic

[Foxy]

...all I did was start yet another "which suspension" thread.

And it didn't disappoint

[Ormes]

Cheers Joe

[jules_s]

Go and see the bloke that set my car up

[FLD]

Firstly I'll make no claims of knowledge of what works / doesn't etc. I've had a few geos and recently fitted gt uprights. I ran 110/120 previously and the bump steer was pretty harsh snatching at the wheel. Fitting the gt uprights and switching to 120/130 to clear speed humps has massively improved the bump steer feel at the wheel. I won't speculate as to the technical reasons for it, I'll just report that it's a worthy change imo. Sent from my iPhone using Tapatalk

[Arno]

For the opel Speedster, it's 140 mm Fr/Rr as mentioned on page 14 of this document: https://www.speedste...e/speedster.pdf   and here   https://www.speedste...sion Adjust.pdf

  And remember... All quoted ride heights are based on:   These measurements approximate to a load consisting of driver, passenger and half a tank of fuel

Lotus defines this in the service manual as '75kg of ballast in each seat and 1/2 tank of fuel'.  

When comparing ride heights this baseline of ballast+fuel needs to be identical.

 

There's no sense in comparing ride heights on cars with different suspension/springs that are are at an un-laden ride height as for instance a softer sprung car will 'sit' higher up without people in the car (and 'drop down' further with them in it) than a more stiffly sprung car will.

 

The 'softer' car may well start higher up in it's un-laden state but end up lower after adding the passengers than an (initially) lower set up stiffer sprung car..

 

Of course this also all assumes that the ride heights are measured at the same spots on the chassis to the floor and not to 'movable' bits like the clam, undertray, diffuser, etc...

 

Bye, Arno.

[Exmantaa]

Arno,

 

do you know the chassis differences/ride heigt for an S1/S2 vs. a VX220? 

And while we're at it, the hub heigt differences between the s1 (alloy & steel hubs?) and later model steel S2/VX220 hubs?

 

These changes in the hub and wheel height make that the VX220 suspension kinematics are quite a bit different from the original S1 design when the car is lowered beyond a certain point.

(I read that on an S2 the issues start already around 120mm front height...)

[2-20]

Annoter différence is longer front wishbones btw S2 and Vx220. S2 ride height is 130/130

[TFD]

VX220 N/A stock trim does 148mm on all 4 corners with just 1/2 full fueltank (well.. mine did).

[Exmantaa]

Annoter différence is longer front wishbones btw S2 and Vx220. S2 ride height is 130/130

 

Yeah, I think the S2 front wishbones are some 8mm longer each side.

[2-20]

And the Exige V6 front are about 15 mm longer (than VX) 

Which would allow to have the same wheel offset front / rear

[Arno]

do you know the chassis differences/ride heigt for an S1/S2 vs. a VX220?

S1 varies as they had some changes over time in the type of springs that were fitted. Officially the S1 is at 140mm stock (ballasted) ride height, but early ones can be as high as 160mm. S2 is officially set at 130mm (ballasted)  

And while we're at it, the hub heigt differences between the s1 (alloy & steel hubs?) and later model steel S2/VX220 hubs?

AFAIK that's quite limited. The S2 upright design (same as used on the VX)was a practical application of a Lotus Engineering research project for the US Steel institute into light weight forged steel parts using stress designs. They used the S1 steel hubs as the baseline and worked from there, so I suspect they are dimensionallu quite similar.  

These changes in the hub and wheel height make that the VX220 suspension kinematics are quite a bit different from the original S1 design when the car is lowered beyond a certain point. (I read that on an S2 the issues start already around 120mm front height...)

Not too odd.. The S1 could run (compromised) around 110 front height, but that's of course on 15/16" wheels and tyres. For an S2 (or a VX on 16" fronts and 195/50R16) your wishbone angles would likely be similar arond 120mm. A VX on the original 17" fronts will probably reach the same angles even around 125/130mm So in it's 'default' ride height settings the VX and S2 wishbones will likely already be angled comparably to what's a mildly 'lowered' S1.

 

When you take into account the fact that an S1 is sitting 'naturally' lower on 15/16" but even then it's set at 140mm (or more..) so (wishbone angle wise) it's really more 'raised' compared to an S2/VX in it's stock setup.

 

I guess you could say that the S1 starts out from a different wishbone angle at the stock ride height compared to the S2/VX *and* theres some small dimensional differences in wishbone lengths and upright attachment points making them react a little differently.

 

Of course you can fit S2 wishbones and uprights on S1's. That has been done by several people, especially on morepowerful ones, to get more robust wheel bearings and larger CV's. Does mean new wheels too (S1 has a MG PCD) though..

Bye, Arno.

Edited by Arno, 06 January 2017 - 09:56 AM.

[Exmantaa]

I thought the later S2/VX steel uprights (have that US steel institute research document saved somewhere) have a 15-20mm lower stub axle height than the early S1 hubs?

Someone once mentioned that this axle offset was maybe due to the higher tire diameter used on the later models, but they had "adjusted them in the wrong direction"... 

(Think it's mentioned somewhere on the EP site that their GT hubs correct this S2 offset to the original S1 geometry...)

[Exmantaa]

A certain SimonS said this on Lotustalk forum about the S1-S2 uprights: Back to the basics of all this, worth mentioning that compared to the Elise S1, the std S2 upright is already at a 16mm disadvantage hub-hight wise (not sure why Lotus did this, I kind of think it was a mistake when they went from 16" to 17" rears the overall radius of the wheel/tyre went up, thus for the same ride hight the wishbone angle get's worse, I think they wanted to correct this with the upright but went the wrong way?) Moving the hub-centre 16mm get's you back to where the S1 is, which for a road car is probably about right at typical ride heights. if you then want to run the cars low, (as in <100mm) then you really need to make a big change.

[Arno]

AFAIK the decision to go to 16/17" on the S2 was made fairly late in the development and probablly post-dates the upright design which was probably still aimed at 15/16", A bit like the VX/Speedster which got bumped to 17" all around by GM fairly late in the development for aesthetic reasons.

 

Also, Lotus is/was always low on cash, so in many cases a better/nicer technical solution is dropped in favor of a less expensive (read: bigger profit margin ) solution.

 

Plenty of those purely cost-based decisions around on these silly plastic cars   (and a source of income for aftermarket companies to build more costly but perhaps better alternatives.. )

 

Bye, Arno.

[Exmantaa]

So to summarize, we can conclude that for the same chassis ride height compared to the original Elise S1 design:

 

- Due to the 1" bigger rims, the S2 wheel centre sits 12.7mm higher. (comparing 195/50/15 vs S2 195/50/16 and 225/45/16 vs 225/45/17)

- Due to the added 16mm offset of the S2 steel uprights, the S2 balljoints sit 28.7mm higher, so steeper wishbone angles/kinematics. (Ignoring here that the S2 wishbones are slightly longer.) 

 

A VX220, depending on the fitted front tires, is even steeper. The standard 175/55/17 fronts have an almost 23mm taller diameter than an S2, so again 11.5mm added to the front wishbone angle. Making 40mm differerence compared to an S1 and they share the same front wishbones.

Suddenly those hefty -40mm offset EP race uprights are not looking so extreme anymore, as essentially the standard VX220 (front)kinematics behave like a 40mm lowered S1...

 

[Nev]

Ride height is currently 125f/130r ish and I want to reduce it.  With current ride heights, there is absoutely no preload on any corner and reducing the ride height any more will mean the spring is inches from the collar when unloaded.

 

I am generally happy with the NSS, but they are 5 years old, probably due a service, and if I could justify new shocks then I would...

 

 

Instead of expensive helper springs, you could design some spacer/collars and ask an engineering firm to make them up on a lathe. It's probably only an hours work and some alu plate (roughly £30 and £15 respectively).

 

Personally, I think you could easily spend £1500+ on new coilvers and it make not one jot of difference, possibly slightly worse, possibly slightly better. If I were you I'd just get them refurb'ed and spend the money on petrol.

Edited by Nev, 06 January 2017 - 03:44 PM.

[Exmantaa]

 will raise his car by the fabricated spring collar thickness (x 1.4 or so on the front)...

 

Fit helper springs to take your spring slack on full droop, or fit cheap lowering brackets on the front to raise the complete shock. (and this way you even keep some bump travel too...)

[Nev]

I find that in practice, with springs (even though I presume they are meant to be progressive) that the first 1 CM of travel approx. is very soft so the spacer will likely not raise the ride height much. So a thin-ish spacer of say 1 CM would at a guess only raise the ride height a few MM.

 

It's a strange thing, but I've noticed it many times with a variety of springs.

 

Helper springs themselves take up a fair bit of height, so I guess the solution really requires shorter main springs too. All gets expensive very quickly as usual.

Edited by Nev, 06 January 2017 - 04:16 PM.

[Exmantaa]

I find that in practice, with springs (even though I presume they are meant to be progressive) that the first 1 CM of travel approx. is very soft so the spacer will likely not raise the ride height much. So a thin-ish spacer of say 1 CM would at a guess only raise the ride height a few MM.

 

It's a strange thing, but I've noticed it many times with a variety of springs.

 

Helper springs themselves take up a fair bit of height, so I guess the solution really requires shorter main springs too. All gets expensive very quickly as usual.

 

  So what do you think your 1 inch spacer does to your ride height, where the spring is pretty well loaded? It has the exact same effect as moving the spring collar 1 inch down and will raise your car... (and by about 1.4 inch due to the wishbone lever action)

 

What you would need is fabricate a spacer that has say 1 inch length at max droop and almost no length when the spring is fully loaded. Hey presto; those variable length spacers exist and are called helper/tender springs!

Edited by Exmantaa, 06 January 2017 - 04:39 PM.

[Ormes]

Cheers again guys

 

I may well go down the route of the lowering brackets... I already have some quantum ones in the garage somewhere that EP sold me about 2 years ago!  The front is what I want to drop slightly more than the rear, as I've only got 5mm rake between front/rear and don't want to go any lower on the fronts as it is now... pretty sure the brackets give you approx 10mm.

 

You hear it here first...  I invited .org to make me spend money... and it has gone all Scottish all of a sudden