Rear Suspension Bump Limiting Spacer

[iancockshull]

Dear all

I have my S4 SE rear suspension struts on the workbench at the moment to give them a bit of a freshen up.
On occasion in the past I have ground the rear exhaust silencer clamp on bumps, I guess most of us have done that too.
In section D6 of the 1970 Lotus workshop manual it refers to Bump Limiting Spacer part 36-D-154 that can be fitted to earlier cars.

Has anyone used this part on their earlier car?

The picture in section D, figure 4 , shows a corrugated item on the damper rod, looks like a rubber gaiter perhaps, is this the Bump Limiting Spacer?.
My car has not got this item fitted to the Armstrong inserts in the struts.

Any suggestions welcome.

Ian

1969 S4/SE BRM DHC

[miked]

Ian,

I have seen those alloy spacers on plus two's when taking the uprights apart. They are about 20 odd mm deep and sit on top of the tube nut. I think I have some in the garage.

Mike

[SADLOTUS]

Ian,

Using the post: http://www.lotuselan.net/forums/viewtopic.php?p=93139

and: http://www.duartevelezgrilo.eu/lotusela ... ension.PDF

The corrugated item on the damper rod in fig4 is a bump stop - the standard Lotus one is like two hollow balls stuck together with a hole through the middle and the outside diameters flattened off (help me somebody!) about 5ins tall and 3ins diameter - see fig1 on the above - the bumpstop illustrated has a rubber sleeve to help keep the rod clean. The Spyder and TTR ones on the 2 1/4 in spring conversion are polyurethane and cone shaped about 2 1/2 -3 ins tall. I have one on each side but has anyone used two each side?

Mike's description follows what the manual says but... only 20mm thick? I suppose that's thick enough otherwise you're using up the suspension movement. I don't think it's illustrated on that link.

[steveww]

The bump stop on the Elan is more than just a bump stop, it is a secondary spring thus producing a progressive spring. I found the cone type supplied by TTR and the like to be unsuitable. When cornering hard the stop provided by these items causes some interesting oversteer moments They are also too short.

The original items (if you can still get them) are best for a standard set up but they are too big to fit inside 2.25" springs. I use a progressive item from Powerflex see http://www.steveww.org/index.php?id=32

[rgh0]

The originals were Aeon type 505 and as far as I can tell they are no longer available. The current manufacturers of Aeon rubber springs on the net do not list them or an equivalent unfortunately. You need a similar rubber spring of similar length or slightly longer i.e. around 5 inches long and spring rate of around 50lb per inch average over about 1 inch compression (starts zero and is about 100 lbs/in after 1 inch of compression.

The late plus 2s had a 20 mm alloy spacer as well. I was not aware this was an option on the the ELan but with a 36 part number it must have been.

cheers
Rohan

[512BB]

Good morning Ian,

My first thoughts on reading your post were, thats a hell of a lot of work to have both suspension legs on the bench, just for a freshen up!

When i bought my first Elan, almost 30 years ago, one of the jobs that neaded doing was rear dampers. Being green, i fitted Armstrongs. Had to do the job again 2 years later, they were shot. I fitted Konis the second time. They are still on the car, good today as when they were then. Ian, your car would be TRANSFORMED, if you took the opportunity in your freshen up, to fit Koni dampers. And then you would not need to fit rubber bump stops, because the rear end would never compress enough to get anywhere near the bump stop. You would fit them, the BS, if you could get them mind. Luckily for you, i bought a pair on ebay a while back. You can have them if you want, PM me.

Happy new year to you all,

Leslie

[SADLOTUS]

Steve and Rohan

Thanks, that's just what I needed to know, although not been driving the car long in its current spec always thought something amiss.

Gonna try the Powerflex SAF-005 - Special Foam Bumsptop

Ta verily

Paul

[ppnelan]

...fit Koni dampers. And then you would not need to fit rubber bump stops, because the rear end would never compress enough to get anywhere near the bump stop.

How does this work - do Konis have an integral bump stop

Matthew

[512BB]

Hi Mathew,

Not sure if you are being sarcastic, forgive me if you are not, but in my opinion, the konis having much more resistance than Armstrongs, do not let the suspension deflect enough to touch the bump stop. At least not the way i drive. So if Ian did not have a bump stop before, and fitted decent dampers, he wouldnt need them in the future. Unless, as i said, he could get hold of some, and then he would probably fit them.

All the best,

Leslie

[steveww]

If fitting new rear dampers I can recommend the TTR GAZ items that I have fitted to my S4. They are adjustable so may be set as hard or soft as required. I find an extra turn and a half firms them up nicely for a track day.

[SADLOTUS]

Ian

on ebay today

http://cgi.ebay.co.uk/ELAN-2-REAR-SPRIN ... 240%3A1318

[iancockshull]

What a great forum the lotuselan.net is, so many replies to my query - I am overwhelmed.

Many thanks to you all for your helpful suggestions, I think spring assisters would be the way to go for me as it is only on extreme occasions when "yumping" an unseen undulation at speed do I notice a problem. I have the standard set-up so normal size springs, not the smaller diameter ones. I can see that progressive springing when getting close to full travel would be beneficial as it would not upset the great handling obtained from the long travel Chapman rear suspension at normal deflections. The Armstrongs are still providing a lot of damping in both directions so I am undecided about changing them, don't want to make too many simultaneous changes unless really necessary. I am refurbishing the brakes too, handbrake swivel tree and replacing the rotoflexes whilst it is all in bits. The diff is out to replace the mountings and tie-rod rubbers, also I am replacing all the wishbone bushes, so it will make the rear end a bit more taut all round when I have finished.

Regards
Ian

1969 S4/SE BRM DHC

[Elanintheforest]

Ian...I've just spotted those magic three letters in your message...BRM. Tell us more!!

Mark

[ppnelan]

Not sure if you are being sarcastic, forgive me if you are not, but in my opinion, the konis having much more resistance than Armstrongs, do not let the suspension deflect enough to touch the bump stop.

Leslie, no, I wasn't being sarcastic! Not this time, but it is not unheard of...
I would have thought the spring stiffness limited travel, rather than damping

Matthew

[iancockshull]

Hello Mark

My car has an interesting history and I have only recently established some of the missing information when I wrote to the Lotus factory and received an informative reply. My car is 45/8779 and it left the factory in February 1969 and was delivered direct to Mike Spence Ltd with two separate invoices, one for the engine L18172B and another for the rest of the car.
It was registered for the road a few weeks later with engine number 3020 E 6015 which had been substantially modified to BRM specification. It has a fully gas flowed big valve head, Cosworth CPL2 cams, enlarged chokes to 34mm in the 40DCOE31 Webers, 4-2-1 fabricated exhaust and fully polished and balanced crank, pistons and conrods etc. It carries the BRM plaque on the front of the camcover and a discrete BRM logo on the nose of the car.
In all other respects I think the car is substantially S4 SE specification with the 3.55 diff etc. so no garish dayglow orange paintwork on it as per some of the other BRM modified cars of the era. I guess the original owner wanted a wolf in sheeps clothing, although a bright yellow car with silver grey trim is hardly inconspicuous.
I bought the car in 1973 with about 25000 miles on it and I used it for a few years as my daily driver. In 1976 I took it off the road at 73700 miles to rebuild the gearbox as it had begun to mis-behave, it was an easy fix as it just needed new bearings. At the same time I stripped the engine and honed the bores, added new rings and valve guides, new bearing shells, timing chain etc. to reduce the oil consumption as it was beginning to affect the spark plug selection, I had to run Champion N9Y in it to avoid plug fouling.
Other events in my life then conspired to prevent me ever getting it back on the road and the car has been in warm dry storage ever since, with intermittent work being done on it over the years as time and bursts of energy have dictated. My interests wandered towards old motorcycles which I still have a passion for and I have restored some over the years. So, I have owned the car now for some 35 years and I recently decided that for its 40th birthday year it really ought to be put back on the road and used again. I commenced by stripping down the rear suspension and diff etc. right back to the chassis which is where my recent discussions on the forum have started. I remember replacing the original rear shock absorbers in 1975 after one of them lost performance, the bad shock turned a sweet handling car into a tail swopping monster but the replacement Armstrongs totally transformed the handling back to how it should be, they still seem to be in good condition with strong damping when operated by hand. I vaguely remember now that back in 1975 that there was a "rubber thing" on the top of the rear suspension damper rods, but they are not there now, so I assume that as a spotty youth I had decided that they were not needed, or perhaps too damaged to be re-used, so were discarded. Now I have got the bit between my teeth I want to maintain the momentum and see the job through, the car has a certain patina now as it matures so I am not planning on changing that too much as I prefer originality where possible.

Best regards to all from East Sussex
Ian

1969 S4 S/E BRM DHC