Replicate OEM Suspension - S2/RowSE/NA(part) - Not USA

[saska]

I'll make this clear at the start -- this is nothing to do with the Nitron suspension that BobB has worked so hard on. If you want to track or lower your car then this is not for you. Started it here in Suspension & Brakes to allow discussion to take place and gauge interest. If there is enough interest then it can get moved to Group Buys.
This is simply an attempt to replicate the already excellent-for-road-use, ex-factory, S2 suspension setup as closely as possible. Currently the S2 setup is recommended by Lotus for all RowSE/S2 and also the Normas (except for the front springs -- so front dampers and rear shocks & springs apply).

To that end I've bought brand new, genuine Lotus, S2 front & rear springs (B100C0086F-Yel/Yel/Grn and B100D0071F-Grn/Yel/White) and a pair of new, genuine front dampers (F100C6015S - which is a pair of F100C6015F). They were bloody expensive! I've been unable to source a new rear damper (E100D6011F) and unless someone has a new one, or a very low mileage one they will lend me for a week or so, then I'll use one from my S2 (which I'm pretty sure is fine).

The new springs will be sent to Turtons (Sheffield) where the exact specifications will be determined (and made available to us and posterity). Turtons can reproduce the springs exactly.
The dampers will be sent to Protech to be dyno tested and again the exact characteristics determined. Whether we can get exact characteristics from them (beyond physical measurements) is hard to say -- viscoelastic devices have hard-to-quantify variable resistance based upon amount and speed of force applied but I'll ask Protech whether they could provide a graph with X=Resistance and Y=Speed of Force or similar. I would like to be able to provide as much information for posterity as possible. This is part of the reason for this project -- there are probably quite a few M100s running around on very tired 15-20 year old suspensions.

Protech dampers have a 13 click bump/rebound adjustment and they have agreed to set the middle setting (6) to reflect the OEM damper as closely as possible. The lower spring seats are also adjustable so the exact OEM spring preload can be accommodated. RayD seems to think, and I agree, that Protech will be able to determine the rear damper's original characteristics even if it is slightly worn. You can play with the Protech damper settings if you want but can always go back to the stock setting (6).

I'm aware there are AVO/Gaz/Various alternatives and that SJs do springs and Protech dampers but these are all unknown quantities and no one knows how to set them up to replicate OEM -- see various discussions elsewhere on LEC -- most of which I've read in the last few weeks. My intent is to try to replace the ex-factory parts as closely as possible on the basis of known information and provide a 'recipe' that allows people to replicate the S2 settings as nearly as possible. I've done extensive research, in various languages, and determined that the OEM springs were made by Monroe (SP1337 & SP1338) and Spidan/GKN (55652 & 55653) but completely unable to find OEMs for the dampers. The method outlined above is as close as I can get to replicating the original parts -- I'm open to better suggestions.

These parts apply to the following cars: all S2/RowSE, the Normas (except the front springs - A100c0087H Yel/Yel/White). None of the parts apply to Federal cars -- apologies to the cousins. I intend to supply Turtons & Protech with the full Lotus applicability information so if anyone wants to run another Group Buy or even buy an individual set later then they should be able to do so (albeit at whatever price per quantity)

Current prices are approximate, based on 20 cars and do not include VAT or a share of my outlay (buying the new bits, shipping them around, getting the new parts shipped from Turtons/Protech, etc.):
Front Protech Damper: £75ea
Rear Protech Damper: £65ea
Frt & Rear Turton Springs: £20ea (may be less)

So for a full S2/RowSE car this looks like:
2 X frt damper: £150
2 X rear damper: £130
2 X frt spring: £40
2 X rear spring: £40
Sub-Total: £360
VAT: £63
Outlay Contribution: £15 (estimated & dependent on numbers)
Total: £438

For a Norma (Everything except front springs): £391

Can't see any reason why individual parts of the kit can't be applied but I'd always advise applying changes to shocks/springs in axle pairs. RayD has helped me with this and will confirm that the above prices are what I'm paying -- not looking to make money and am already well out of pocket on the single front and rear new Lotus springs (£170+Vat+Ship). The pair of new Lotus front dampers (£214+V+S) can go on one of the cars so don't mind that too much.
Whatever we can do in terms of using the LEC Distribution Network to reduce onward shipping costs to LECers I'll help with as much as I can though bear in mind I'm in deepest, darkest Cumbria. If I have to post them then I will but post charges will be additional.

Terms: if we get enough for a run then when the list closes, a 60% deposit of what you ordered is required (I'm not fronting ~£8600) or you can pay the full amount. When the parts are made and in my possession ready to distribute, you pay the remainder plus any onward post charges if that is required. Payments to be made by bank transfer, cheques, money orders in Pounds Sterling but NO PAYPAL. Not paying their percentages, so forget it.

If anyone has a new(ish) rear S2 damper (E100D6011F) they'd lend me for a week or 2 (I'll pay post both ways) then please email soonest. I'm intending sending the springs & shocks to Turtons/Protech later this coming week or early the week after.

Not doing any nuts, bolts, isolaters, whatever -- that's up to you - just the springs and dampers.If someone else wants to do a fitting kit then fill your boots.
If you wish to contact me about any details, or even just to insult my parentage, please use email as my PM Inbox limit is quite small.

Apologies for length.

Anyone feel like starting a list?

[Denny]

This is exactly what I'm after. Cheers
Unfortunately I cannot supply you with a damper.

1. Denny - Full set (front & rear)
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[kenich]

I am tempted but have money tied up elsewhere for a few months. If in that time the list still has spaces nad hasn't closed I will be likely to add my name.

Kenich

[woody]

Excellent idea, count me in.
1. Denny - Full set (front & rear)
2. Woody - Full set (front & rear)
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Cheers,
Woody

[ashm]

I'd be interested, but it very much depends on the results of the development process.
Adam

[RayD]

Adam,

As I understand it there isn’t any "development" as such.

They are replicating the original damper and springs.

Not being able to easily quantify the spec of a damper there’s a chance some aftermarket ones only vaguely do what they say. To that end Protech will hopefully supply understandable information which will demonstrate the new ones are as close as they could be to the original S2.

The same applies to the springs at Turton’s.

It’s kind of Tony to mention my help but I’d need to do a lot more to catch up with the help he’s given me on the computer front.

Ray

[saska]

I'd be interested, but it very much depends on the results of the development process.

Adam,
RayD's comments are pretty accurate however some additional comments:
1. The real problem with something like the AVO/Gaz option is they are adjustable for both ride height/spring pre-load as well as bump/rebound characteristics. Ride height/spring preload is controlled by where the lower spring seat on the damper is in relation to the lower TCA/rest of the suspension (as well as the spring itself). My intent is to measure the distance from the lower spring seat on the OEM dampers to lets say the centre of the yoke mounting holes on the damper (See photo at end). Setting the lower spring seat on new dampers to the same value should mean the spring preload and ride height are identical to OEM (assuming the springs are identical to OEM and the length of the damper is correct).
2. Damping characteristics are a variable commodity in viscoelastic devices and while they don't control how much the car will ultimately roll they do control how fast it does so. Getting the balance correct between front and rear is essential if you want to stay out of the shrubbery. You can't set adjustable dampers the same front and rear and say that'll be fine because in the M100 you've a lot more weight on the front than at the back -- life would be easier if we had 50/50 weight distribution, but we don't. This is why I'm trying to replicate things as close to Lotus OEM as possible because Miles/Shepherd are very good at this stuff and IMO have produced a car which is excellent, but more importantly predictable, in both wet and dry.
3. There is enormous difference between the front & rear springs and I'd expect there to be differences between the dampers -- getting Protech to measure both front & rear and then set the centre setting to match means that as long as the lower spring seat to yoke distance is correct then you should be as close to OEM as possible.

As an aside, it seems to me that those who already have AVO/Gaz/Protech dampers could reproduce the OEM ride height pretty accurately by setting the lower spring seat to damper yoke distance to OEM (approx 125mm on the fronts to centre of upper yoke hole). Replicating the damping is much harder and is why I chose Protech -- they have the kit and seem amenable to using it.

Although there doesn't seem to be much interest, the state of play is the OEM springs have been sent to Turtons. I have new OEM front dampers here and will pull a rear from the S2 and send both to Protech next week. I've also asked Turtons to price for any anti-rust coating options.

[Specky]

One thing for the N/A lads to keep in mind is, the front springs are still available for £5 ea from the aftersales, so if they would fit the new dampers..... Winner.....

TTFN

[ashm]

As I understand it there isn’t any "development" as such.

Yep, I really meant the damper situation. I imagine for Protech, hooking the OE dampers up to a good shock dyno and running the tests is pretty trivial. What I'm really interested in is to see the bump & rebound load/velocity curves for the OE dampers and how close they can tweak the Protech dampers to replicate them. If they're pretty close and all the dimensions are correct then we're probably onto a winner.

Adam

[bobbrown]

There is one area you need to be careful with and that is the amount of travel on the dampers. If you use a damper with a shorter body length and a longer piston rod then this will allow the front wheel to travel further up into the wheel arch and if allowed to travel too far rub on the wheel arch liner on full bump. Do not for get the motion ratio comes in to play here so if the body of the damper is say 10mm shorter then the wheel will move up around 20mm in round numbers. This is not so relevant on the rear but critical on the front, just measure the clearance on the tyre to the wheel arch liner and I think you will get the idea.
Just thought you should be aware if not already.

Bob

[saska]

There is one area you need to be careful with and that is the amount of travel on the dampers. If you use a damper with a shorter body length and a longer piston rod then this will allow the front wheel to travel further up into the wheel arch and if allowed to travel too far rub on the wheel arch liner on full bump. Do not for get the motion ratio comes in to play here so if the body of the damper is say 10mm shorter then the wheel will move up around 20mm in round numbers. This is not so relevant on the rear but critical on the front, just measure the clearance on the tyre to the wheel arch liner and I think you will get the idea.

Yes. I''d considered this along with the fact that the bump-stop is built into the upper sleeve of the OEM damper -- I'd like the bump stop to be in a very similar place in terms of fully compressed damper length.

Just thought you should be aware if not already.

Thanks for input Bob -- its appreciated. If anything else occurs that you think I've got wrong/missed please let us know.

[M100_DMM]

One thing for the N/A lads to keep in mind is, the front springs are still available for £5 ea from the aftersales, so if they would fit the new dampers..... Winner.....

TTFN

Are you sure? I can't find any reference to NA springs on the Lotus parts sale list except for a solitary spring/damper assembly available at a smidgeon over £34.

[M100_DMM]

Excellent idea, count me in.
1. Denny - Full set (front & rear)
2. Woody - Full set (front & rear)
3. M100_DMM - Full set (front and rear) - NA
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Cheers,
Woody

Saska, many thanks for your initiative and effort on this one.

[Specky]

One thing for the N/A lads to keep in mind is, the front springs are still available for £5 ea from the aftersales, so if they would fit the new dampers..... Winner.....

TTFN

Are you sure? I can't find any reference to NA springs on the Lotus parts sale list except for a solitary spring/damper assembly available at a smidgeon over £34.

That damper/spring assy is long gone... It's with an N/A front spring in my loft.... Don't forget all the previous aftersales lists from subsequent years, if they still hold the stock they honour the price...

Just double check with Hethel, if memory serves there was still four or six left...

TTFN

[BFG in the BRG]

Oh Oh - another Group Buy - I couldn't afford the BB one, and thought it a little OTT for what I use the car for.

I figure the originals will probably need replacing by now and this sounds like a great option.

1. Denny - Full set (front & rear)
2. Woody - Full set (front & rear)
3. M100_DMM - Full set (front and rear) - NA
4. BFG in the BRG - Full set (front and rear)
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[Jackonicko]

If this is running when my current legal expenses have ended, I will definitely be up for this, but I don't want to hack you off by adding my name then backing out.

[saska]

Just an update.
I've got the spring specs from Turtons -- very good service -- the springs arrived back here by TNT today.
I've added the info to the Wiki HERE
----------------------
FRONT B100C0086F Yellow/Yellow/Green
Diameter of Wire d (inches): 0.531”
Inside Coil Diameter(inches): 3.298”
Outside Coil Diameter(Inches): 4.360”
Number of Coils: Total 8.5
Free Length (inches): 10.690”
Actual Load Rate Measured on Test (Pounds per inch): 300 Lbs / IN
Loads at Testing:
10.000” = 186 Lbs
9.000” = 485 Lbs
8.000” = 785 Lbs
7.000” = 1087 Lbs
6.000” = 1390 Lbs
Remarks
BOTH ENDS CLOSED & GROUND FLAT & SQUARE
TIPS JUST TOUCHING APPROX THICHNESS 50%
EPC BLACK WITH CC = 2 X YELLOW 1 X GREEN STRIPES

REAR B100D0071F Green/Yellow/White
Diameter of Wire d (inches) 0.406”
Inside Coil Diameter (inches) 3.338”
Outside Coil Diameter(Inches) 4.150”
Number of Coils Total 6.6
Free Length (inches) 9.490”
Load Rate (Pounds per inch) Actual Load Rate Measured on Test (Pounds per inch) 144 Lbs / IN
Loads at Testing
9.000” = 65 Lbs
8.000” = 210 Lbs
7.000” = 354 Lbs
6.000” = 495 Lbs
5.000” = 642 Lbs
Remarks
BOTH ENDS CLOSED & GROUND FLAT & SQUARE
TIPS JUST TOUCHING APPROX THICHNESS 40%
EPC BLACK WITH CC = 1x GREEN 1x YELLOW 1x WHITE
STRIPES
----------------------
I now have confirmed pricing from Turtons which follows:
Springs to samples supplied, powder coat finish & colour code
B100D0071F
2x £75.00 each
4x £42.00 each
10x £23.00 each
20x £19.60 each
40x £18.00 each
B100C0086F
2x £80.00 each
4x £45.00 each
10x £26.00 each
20x £23.00 each
40x £21.00 each
Carriage: For parcels up to 10x springs £15 per 10, pallets any qty £45
Delivery: Approx. 5 weeks from receipt of order
-----------------
The springs would be powder-coated black and if we can get 10 cars then the pricing isn't unreasonable in my view.
Protech should already have a front and rear damper but I haven't heard from them yet.

[stevieg8571]

Tony,

All sounds good to me.

My car's SORN'd currently and I'm going to be working away until mid May but definately interested.

I live in Preston so probably not too far to collect the kit from yourself and as I drive to Lincolnshire every week, maybe I could help with the distribution?

Steve

[saska]

My car's SORN'd currently and I'm going to be working away until mid May but definately interested.

See below for time frame but mid-May will probably be OK

I live in Preston so probably not too far to collect the kit from yourself and as I drive to Lincolnshire every week, maybe I could help with the distribution?

This would currently only help Woody (Nottingham) but we'll see -- thanks for offer.

Update on state of play:
Springs are done (see above).
I've received the dampers back from Pro-tech today. There was an 8 day delay while bloody Parcel Farce sat on them saying that Pro-tech's address didn't exist. Then Kevin had to make a bracket to fit the front damper to the dyno machine due to the unusual lower mount to yoke. He has now dyno'd/measured both front and rear dampers. He is away next week but then wants to make up Pro-tech front and rears in order to provide dimensional and dyno comparison data against the OEM dampers.

Kevin has taken on board BobB's comment about the bump stops and will be looking to replicate their position/hardness. By my rough dimensional measurements while the front bottom tube is 290mm (no lower mounting eye), the rear is only 265mm (including the lower mounting eye). Yet the travel on the rear piston rod is 90mm whereas the front is 75mm -- so the front has a longer tube but the piston moves less distance in it than the rear. The length of travel is understandable given the front spring has twice the rate of the rear spring but the tube length isn't so obvious.
Kevin has also said they do a locking ring for the lower spring seat position -- so the ride height/spring pre-load could be set and locked either by Protech, me or the recipient to the original equipment setting. Equally those that wish to be able to adjust their preload/ride height need not use the locking ring.

I have to say that Pro-Tech seem to be very keen to replicate the dampers as closely as possible. I'll advise when we have dimensional/dyno comparison data -- hopefully the week after next.

For those who already have AVO/Gaz/Pro-tech dampers you should be able to replicate original equipment ride height/spring pre-load as follows:
Front: lower spring seat on damper to center of top yoke mounting hole on damper: 125mm
Rear: lower spring seat on damper to centre of lower eye: 168mm
The above assumes your springs are OK

[BFG in the BRG]

Tony,

All sounds good to me.

My car's SORN'd currently and I'm going to be working away until mid May but definitely interested.

B100D0071F
4x £42.00 each
10x £23.00 each
B100C0086F
4x £45.00 each
10x £26.00 each

So with 5 on the list we're at the 2 for the price of 1 (ish) for the springs anyway