Anti Roll Bar Diameter

[rgh0]

It might be the other way around since my car was originally sold in Virginia and has a 5/8” bar. Brian Buckland in his manual (he presumably is referring to the UK) said it is 11/16”.

Ivan

Unless someone has better data I think Brian Buckland and 11/16th for the Elan is wrong

cheers
Rohan

[1owner69Elan]

It might be the other way around since my car was originally sold in Virginia and has a 5/8” bar. Brian Buckland in his manual (he presumably is referring to the UK) said it is 11/16”.

Ivan

Unless someone has better data I think Brian Buckland and 11/16th for the Elan is wrong

cheers
Rohan

Piece of data. My original 1969 S4 SE Federal Elan had an 11/16" bar. Just measured it, and it is original (guaranteed). I took it off recently and replaced it with a 1" tubular one.

So, perhaps the factory did make different stock Elan sizes. Perhaps a difference between SE and non-SE models?

One other caveat, I picked my "export model" up at the UK factory, so maybe there was a difference between UK and ROW models, but somehow mine happened to be a partial "UK version". There was an issue with getting my car delivered in time, and a friend with factory connections, intervened and was able to jump the queue and get my car pulled off the line early. Might account for the ARB difference? My factory paperwork also referred to my car as a "Super Safety" when it was in fact a Federal S4 SE and delivered in July 1969. Inscrutable Lotus......

[rgh0]

It might be the other way around since my car was originally sold in Virginia and has a 5/8” bar. Brian Buckland in his manual (he presumably is referring to the UK) said it is 11/16”.

Ivan

Unless someone has better data I think Brian Buckland and 11/16th for the Elan is wrong

cheers
Rohan

Piece of data. My original 1969 S4 SE Federal Elan had an 11/16" bar. Just measured it, and it is original (guaranteed). I took it off recently and replaced it with a 1" tubular one.

So, perhaps the factory did make different stock Elan sizes. Perhaps a difference between SE and non-SE models?

One other caveat, I picked my "export model" up at the UK factory, so maybe there was a difference between UK and ROW models, but somehow mine happened to be a partial "UK version". There was an issue with getting my car delivered in time, and a friend with factory connections, intervened and was able to jump the queue and get my car pulled off the line early. Might account for the ARB difference? My factory paperwork also referred to my car as a "Super Safety" when it was in fact a Federal S4 SE and delivered in July 1969. Inscrutable Lotus......

Did you allow for the paint thickness when you did the measurement as a few layers of paint can give an O/D of 11/16th when the bar itself is only 5/8 ? But with Lotus anything is possible so maybe some 5/8 and some 11/16 and Lotus did not bother recording the change or option if it was model dependent. My Elan was a standard model 68 S4 FHC that came with the 5/8 inch bar originally.

[redcarandco]

With lotus there is only one certainty....it is that nothing is certain..... have here at home 3 front bars very original and free of painting and all are 5/8 in.... or 15,9mm for "normal" people These are front bar we use in wet condition on race car
Belgian Roger

[redcarandco]

Sorry friends (merely for Rohan) I plead guilty for speaking too quickly I just measured the one in the truck (I use in wet condition) and it is 11/16 just around 17,4mm and as I phoned just now to a french friend he said just 3 minutes ago but he is not 100% sure these come from elan BRM ......? But anyway it exists and I employ it for 40 years without knowing and by the way its perfect in the wet
Belgian Roger

[1owner69Elan]

Unless someone has better data I think Brian Buckland and 11/16th for the Elan is wrong

cheers
Rohan

Piece of data. My original 1969 S4 SE Federal Elan had an 11/16" bar. Just measured it, and it is original (guaranteed). I took it off recently and replaced it with a 1" tubular one.

So, perhaps the factory did make different stock Elan sizes. Perhaps a difference between SE and non-SE models?

One other caveat, I picked my "export model" up at the UK factory, so maybe there was a difference between UK and ROW models, but somehow mine happened to be a partial "UK version". There was an issue with getting my car delivered in time, and a friend with factory connections, intervened and was able to jump the queue and get my car pulled off the line early. Might account for the ARB difference? My factory paperwork also referred to my car as a "Super Safety" when it was in fact a Federal S4 SE and delivered in July 1969. Inscrutable Lotus......

Did you allow for the paint thickness when you did the measurement as a few layers of paint can give an O/D of 11/16th when the bar itself is only 5/8 ? But with Lotus anything is possible so maybe some 5/8 and some 11/16 and Lotus did not bother recording the change or option if it was model dependent. My Elan was a standard model 68 S4 FHC that came with the 5/8 inch bar originally.

Checked for paint thickness. No thick paint. Further sanded a portion off. The 11/16” is what it is, measured with a micrometer.

It appears to me that the 11/16" is indeed standard (and not 5/8") based upon the following 4 pieces of data:

1. The Dave Bean catalog (which is usually pretty accurate)

Shows 11/16" (P/N 026C 0003) as standard for the Elan.
Shows 3/4" (P/N 050C 0003) as standard for the +2

2. The parts manual (also purchased directly at the factory) shows the same P/N 026C 0003 as applied to all models S1-S4 (my parts manual predates the Sprint).

3. Brian Buckland indicates 11/16" as standard for the Elan.

4. 50+ years of unbroken custody, direct from the factory, on my Elan which has an 11/16" bar

It would appear from the above documentation that a 5/8" bar for the Elan and a 11/16" bar for the +2 are outliers.

[rgh0]

I think what it means is that Lotus used 5/8, 7/16 and 3/4 bars and did not document when and where they used them and people try to find a pattern or a correct answer where their is none. The is enough data to say Elans may have had either a 5/8 or 11/16 bar fitted and Plus 2 either 11/16 or 3/4 fitted.

Lotus appears to have failed to document this bar size variation in anyway or anywhere and all subsequent statements are based on limited sample sizes and are inconclusive except to say that people report having 5/8 and 11/16 bars on Elans that have not been changed from Factory delivery and people report having 11/16 and 3/4 bars on Plus 2 that have not been changed from factory delivery.

Maybe we need to do a survey of all people on the forum and get them to measure what they believe are the original roll bars om their cars. Perhaps this will give more data on what bars were fitted to what cars

cheers
Rohan

[LotusElon]

Another Data Point:
UK 1969 S4 DHC (non se) .. Original, Continuous ownership Known - I'm effectively 2nd owner and in touch with 1st owner. Original ARB is 11/16" (aka 0.688" aka 17.46mm).

Just testing (lockdown allowing) an older TTR (medium) ARB from that measures 3/4" ( 0.75" 19.05mm), which with standard, but height adjusted, spring rates F&R makes a big difference .. as it says at the top "Anti-Roll" .. much less roll and, front end seems more 'sharp' (I know like all handling descriptions - SO subjective ) .

After lockdown, I'll be doing more experiments (along with 'motor' tuning) although I may now, not need to test the higher ratio rack.

FWIW I'm fascinated by steering feel and Steering ratio (angle of steering wheel / angle of steering at wheel) is often ignored, but can define how a car 'feels'

For example (some of my favourites):
Standard Elan (not +2) Ratio (measured) 13.98
Elan with Modified Moss 'Quick' Rack 12.24

Lotus Elise / Tesla Roadster etc. Standard Rack 15.8
MX5 (2016) 15.5
Caymen 718 (911 Turbo rack) 12.5
Open Wheel (racing cars) 10 to 12
Tesla Model 3 10.3
Caterham7 8
Kart ~ 4.5

[redcarandco]

Hello you all contained I really hope you are all well...This post on front anti roll bar brought me to think race suspension setting ....question is If I change my front 7/8" antiroll bar to a 1" is it going to improve something in car handling or is it going to destroy actual almost good behaviour.... the only thing I do not like is car tendancy to roll during long curve with heavy support Does anyone have experienced this change of bar ?
Belgian Roger

[zog]

It has been my experience that S1 Elans and early S2s had a 5/8" ARB. Somewhere in the early S2 production run they moved up to an 11/16".

RD bushes are one size fits all. Tight on the 11/16 bar and sloppy on the 5/8. I prefer the polyurethane drop link and ARB bushes. They are actually a bit easier than the rubber ones to install.

While you have the bar out, make sure it is straight. Some of them get twisted and can throw off the installation and handling. They can be straightened with a lot of leverage and stubbornness.