Suspension upgrades

[exarkun1178]

Suspension upgrades

I know i know, check the KB.  my point in adding these threads is to build up some searchable knowledge here.  if this forum is ever to take over for the Yahoo group, we will need content here

Anyways,  whats every one doing?

currently i have the europe spec springs up front.  all 4 corners have adjustable  spaxs


Looking at my set up, the rear springs look as though they have a lot of sideways travel. they are SO tall.  they are also very dirty. 

would any one recommend a reasonable upgrade option for the rears?

[EuropaTC]

I've been researching over the last few months and trying to do sums on what I will change to later this year. 

I've settled on 250lbs/ins front and deciding between 120 or 150 lbs/ins at the rear.  From calcs that gives frequencies of around 1.8/1.7 (1.9 with 150) compared to 1.2/1.4 on the OEM setup. I shall probably buy both 120 & 150 rear springs because they're not that expensive and then I can try them back to back and see what suits me best.

The anti-roll (sway) bar makes quite a significant addition to the OEM spring rates in cornering so that low 1.2 isn't the whole story but as spring rates increase the effect from the bar is reduced as an overall percentage. Logically I should increase the bar as well but I'll see how it is with the springs & dampers first.

I'm not sure how this applies to your car because mine is a TC, which is roughly 100lbs heavier than your S2 and more rearwards weight distribution. I've also got 15" wheels with 195/205 tyres on, the same rolling radius but heavier than stock wheels.

To add more confusion and options (     )  I posted a precis of what I'd found in the KB regarding spring rates here - http://www.lotuseuropa.org/LotusForum/index.php?topic=538.0

Brian

edit to add - I've just looked at the photo you posted and it looks to me as if the front springs have already been changed. Is that 9-10 coils there ? IIRC the S2 has something like 18-19 coils as OEM ?

[exarkun1178]

Brian,

just about all you said was way over my head.  the front springs were changed last year.  i ordered them from R&D - they are the european spec springs.  how many coils? no idea.  but i can say its lowered the front of the car significantly

[EuropaTC]

 

ok, I'll confess, most of it is above my head as well......     I just like to drop in big words and pretend I'm an internet expert 

The frequency bit is just a measure of how the wheel moves and I just use it as a number to compare how the car will feel before & after.   

For example, it it's low (1.2-1.4) then the car's going to feel soft, ramp it up and it'll feel harder.   From what I can find, it seems that above 2.0 is getting into track or perfect roads territory and so I've tried to keep just below; I quite like racy suspension and I've no plans for long road trips so I think I'll be fine with it on the "hard" side of things.

You can have what looks like big differences between front & rear spring rates.   Although the front 250lb might sound ridiculously high given that the most of the weight is at the back it's not because the spring is acting at an angle which reduces the effective rate. Plus there is a leverage component from the way the suspension wishbones are designed which reduces a bit more.  At the rear the spring is vertical and there's almost zero reduction in the rate from leverage and so what you see is what you get at the rear, but at the front it's not so obvious.

I guess what I'm trying to say is that there's no "one size fits all" with these cars.  For your car I think I'd try and find out what the front springs are rated at because from what I've learned in the KB it is important to balance front & rear. If you can't find out about the front springs on your car I'd be tempted to change all 4 so I knew I had something that would keep the under/oversteer thing similar to the original car.   Apparently it's all too easy to end up with a car that feels fine at lower speeds but bites you viciously as you reach it's limit. (or your limit    )

Brian

[cal44]

Yes.....new springs. 

Every car I get in I change out to new springs and shocks.  People are under a weird notion that springs stay on spec for ever.......not true.  They lose just a bit every year or so....... then people can't figure out why the handling isn't as good as it should be............

I get into it with car guys all the time that are convinced 40 year old springs are O.K..........it's maddening.


What Brian wrote............

mike

[erioshi]

Blah, lol.   I just posted over in the other thread when I meant to post here.   

[JLM]

Here's what I have done for my 73 Twink -

Front
Shocks -Spax adjustable model G867 (bought in a group buy on Yahoo board quite a while ago)
Springs - Started with Hypercoils (2.5 in ID, 10" length, 180 lb rating). These gave the same height as stock shocks.
              Went with QA1 springs (2.5 in ID, 9" length, 180 lb rating). These brought the front-end down to where I thought it should be. 
              Sourced the QA1 springs from naake.com in Roseville CA, circle track suppliers, cost was $72.00 for both springs.

Rear
Shocks - Spax adjustable model G876 (also bought in group buy)
Springs - 1 7/8" ID, 14" length, 120 lb rating (sourced from Suspension Spring Specialists, bluecoilspring.com, $100 for both springs)

I replaced two bent suspension arms at the front, cleaned everything up and put everything back together. Still need to deal with the sway bar drop links as they are now too long, will likely cut the top mounting bushing off and replace it with an adjustable heim joint. I'm still working on the rear suspension and will likely get adjustable rear links.           

[Lou Drozdowski]

Save the headaches, I thought long & hard to lower the nose, get the spring rate right and dial in the ride height...solution.
Spend the money and call Richard Winters at Banks.ld

[Serge]

Brian,

is it possible to share your calculations, so I can take a look and try to understand everything. Maybe I'll be able to do some calculations for my own car.

I've already decided on a manufacturer for my shocks and they are way more advanced than the AVO's, which are a basic twin tube design that's been around for years.

Mine will be custom length aluminium mono tube designs, floating pistons, nitrogen filled and a double digressive piston design. Everything will be custom valved to my specific need based on weight (distribution), tires, spring rates, etc. They will be from a local company. I have the privilege to live around the best suspension companies in the world it seems. Intrax, AST, JRZ, MOTON, Reiger, they are all within an hours driving of me.


Kind regards,

Serge

[EuropaTC]

Hi Serge,

I've no problem at all in sharing the calcs, but I'll warn you know that there's nothing fantastic in there, it's very basic but seems to be similar to what everyone else is doing.  I'll tidy up the spreadsheet and save it as Excel format, it's currently .ODS from the Libreoffice spreadsheet.

This is for the TC though and you would need to make changes for your car.  Apart from the overall weights and weight distributions, the S2 hub carrier has two lower bolts with the suspension arm being inboard a fraction. The TC has a single bolt which carries both the lower link and damper, so those geometries will need to be changed.

I'll post as an edit either tonight or tomorrow and would welcome comments/discussion and even corrections !

Brian

Edit - I've tried this morning but can't post spreadsheets, either Exel or OpenOffice format. If anyone wants to see my mad scribblings send me a PM & I'll post it directly.

[LotusJoe]

Edit - I've tried this morning but can't post spreadsheets, either Exel or OpenOffice format. If anyone wants to see my mad scribblings send me a PM & I'll post it directly.

Brian, It should work now, I have made the change to allow spreadsheets.

[EuropaTC]

Thanks Joe, I'll have a shot this post.

Note to anyone looking at it;

1. My skill with spreadsheet work is about that of a 4yr old. ( actually, I might be a bit generous there, I've seen some clever 4yr olds)
2. Unless stated on the sheet, data is for the OEM TC or measured from my car. (any S2 data is just there for my comparisons)
3. I shortened my front springs by one coil as the front ride height was silly. It's still not right according to the manual but the damper/spring was bought & fitted by me as genuine Lotus supply. (hmmm ?)
4. I can't get the published OEM spring rates to correlate with the commonly used method for calculating spring rates. It's Lotus, go figure....
5. Car weights are assumptions from published road tests. All vary as some use "on the road" with fuel, radios, etc and others use the minimum net weight. Numbers used here are approximations.

Finally, I'm very happy to hear from others on this. I don't throw hissy fits if folks disagree with the direction I'm heading or find mistakes in my efforts.  I'm learning and really have no idea what I'm doing, this is the bottom of a learning curve so don't take anything for gospel truth - TNDYOR as they used to say.

(Trust No-one, Do Your Own Research)

[exarkun1178]

Ray at R&D had shocks and springs,  is any one familiar with these?

[Roger]

Ray at R&D had shocks and springs,  is any one familiar with these?

I have springs and Spax from Ray on my TC. They're fine!