Lotus Elan and Lotus Elan Plus 2 Forums

I'm reading the bump stop story with great interest.

When I bought Koni inserts for my rear suspension from TTR I asked Tony about bump stops - he said they were not necessary, therefore, I did not fit any.

I would appreciate any informed comment on this.

Interesting..
I have TTR rear shocks and stock bump stops
Tim

Tony Thompson runs cars with very stiff rear springs in competition - around 200 lb /in -
with this set up you dont need the original bump stops. I pefer softer rears both on the track and road and the bump stops then provide the stiffening needed in corners.

Lotus did not spend the money on them for no reason

cheers
Rohan

bcmc33 wrote:I'm reading the bump stop story with great interest.

When I bought Koni inserts for my rear suspension from TTR I asked Tony about bump stops - he said they were not necessary, therefore, I did not fit any.

I would appreciate any informed comment on this.

That's odd, maybe due to recently aquired "experience".
I bought mine from him & reduced the length by 1/2 as then advised

Errrm just remembered, his rear damper spec' has changed since I bought mine so there's possibly a connection there.
I'm sure I had a cup of tea somewhere

Spoke to Stuart at TTR today and he did not understand why Tony did not sell me bump stops to go with the Koni's - aspecially as I'd mentioned them. I spent over fifteen hundred quid at TTR that day, so another twenty would not have been noticed.

So, do I take it that the right move for me is to fit Powerflex SAF005 bump stops with spacers?

Hi Brian,

sounds like a bit of a conundrum to me.
If you bought your dampers & springs from TTR they should be the people who would know if bump stops will be required with the supplied set-up & your proposed usage.
Give 'em another bell & ask for some clarity on the issue. Stuart should know what bit goes with what.

Cheers
John

HMMM,

I had a similar experience when I was buying the billet everything for the rear end of the S1 last year - Anyway, Tony implored me to replace my existing adjustable shocks with his Koni's because with his sliding splines I needed the droop protection they afforded. I conceded and left it with instructions to please send me everything I need to to install all this stuff and make it work and be reliable( associated bearings, seals, hardware etc ). I got a complete kit of beautiful gear from TTR - Minus the bump-stops, I think I talked to everybody at TTR before this particular order went out , so can't explain why they are not there. The front's I bought in 2007 had bump stops.

I had a discussion with my sensei in December when we were piecing this together and his quip was , maybe the lotocone acts as a cushion ( glad I am not running the Spherical bearing like I was on the S2) .....

Anybody interesting in buying a surplus set of Spax Adj inserts ??

George

For what it's worth:
TTR solid driveshafts.
Rear suspension: Spyder A frames, TTR short shocks, adjustable perches, 100LBs springs. short (44mm) TTR cone bumpstops.
Front suspension: Spyder bones, TTR adjustable shocks and springs, 125LBs
Standard roll bar

Soon to change to slightly longer bumpstops - 80 or 72 mm Powerflex

SADLOTUS wrote:For what it's worth:


Soon to change to slightly longer bumpstops - 80 or 72 mm Powerflex

I measured the length of the shaft showing on my rear shocks at 83mm at normal ride height.

TTR advised that their Powerflex bump stop is 45mm long. (Probably SAF027)

Powerflex SAF005 has been mentioned and is the longest in their brochure at 81.39mm.

The question that comes to mind is - at what point is the bump stop meant to come into play?

Also, what load/deflection characteristics are suitable for the Elan?

Original Aeon 505 rubber springs were a double convolute rubber spring 79mm long and 63mm outside diameter. Spring rate over the first 1 inch of compression was around an average of 150 lb/in I think. I dont have any orginals off a car to measure and I am still trying to track down the complete original specifications.


83 mm or shaft exposed between the top of the shock tube and the bottom of the spring retainer at the centre of the cone next to the shaft is a little lower than normal. I think around 100 mm is more what i would expect.

Do you know the spring rate of the power flex bump stops no data is given on the web site and most of these types of devices are typically too soft for what the Elan needs.

I have been chasing a replacement for the orginal Aeon spring for a while now. Timbren the company who owns the brand name now has never made the type 505 according to their technical guys but 2 of their A155 - 65 single convolute springs in series come close to the orginal dimensions and spring rate.

I have also found a company in Australia called Loadtech that makes identically dimensioned and numbered rubber springs to the Aeon originals including a type 505. I will follow up with them next week to find out more.

cheers Rohan

This is information I have on my computer for Powerflex:

Following on from Rohan?s reply re softer road springs and stiffer springs for cornering and Brian?s comment about when the bumpstop actually comes into play, then following a link to the Timbren/aeon site:
http://www.timbren.com/aeon-rubber-springs.htm
there seems a lot more information on that site than on the Powerflex site, so I rang them. The Powerflex techy said: (I think)

The graphs show the amount of force need to squash a spring assister by so many cms.
therefore
Bumpstop SA018 needs a force of 600 Newtons to squash it by 4 centimeters
1 newton = 0.225lbs force
therefore
When Bumpstop SAF018 is squashed 4cms it produces a force of 135lbs
therefore
Bumpstop SAF018 produces a force of between 0 and 247.5lbs over it?s usable length of 4 cms (total length 7.25cms)

He said they only tested the bumpstops a quarter to a third of their length (ie not til they were flat!)
He said it was OK to drill or cut them due their closed cell construction - bearing in mind the diameter of the damper shaft (20mm)
He said he did not know how much, or if at all, the bumpstop would distort dimensionally when compressed - bearing in mind the inside diameter of a 2.25inch spring (59mm).
The two lines on the graphs represent the compression force and the release force of the bumpstop - the top line being the compression.

Steve?s suggestion of SAF005 looks good with a usable diameter (54mm), a reasonable deflection graph 0 - 270lbs (135lbs when squashed by 4cms ie half its length) and a perfect rod diameter (19mm) - only its length (81.39mm) appears to be a stumbler.

I hope this adds a little more to the discussion, please bear in mind I haven?t been to school for 35 years so this might all be complete b?11?ck$

When ordering some bits from Burton last week I included a pair of SAF005 to fit one weekend when I have nothing better to do.

I will do a before and after twisty cross county run to see if I can tell the difference.

I am a huge fan of Nick Adams after his visit to Colorado for LOG 27 in 2007. Let me share a couple of stories with you so you will know why.

He was one of our honored guests and representing Lotus Cars. As such we tried to treat him as an honored guest and he would have none of it. When one of our attendees had a mishap with his Europa and damaged his front suspension, there was Nick under the car in the carpark with tools taking charge of the process and spending over two hours on the repair. Later he gave a wonderful talk to the group and then spent all day at Woody Creek race track giving rides to anyone who wanted one in the 2-Eleven. He did over 200 laps that day! Finally, he went to a little bar (pub) with us after the official meet had ended where some 35 people consumed a lot of mexican food and 38 pitchers, yes pitchers, of margaritas.

A class act, a true Lotus fan and a wonderfully delightful story teller as well as a truely decent guy.

I too have met Nick Adams and found him to be a throughly good chap! if you see him about, he'll happily talk Lotus with most people. I met him at a sprint event, and chatted to him, before he soundly beat all comers in his Class in his Elan