Lotus Elan

Tyre pressures

PostPost by: mikebailey » Sat Jan 07, 2017 12:10 pm

The recommended pressures for the plus 2 are 20 psi front and 24 rear. This seems quite low to me. If using modern tyres, should one stick to these pressures, or are modern tyres designed to run at higher pressure?
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PostPost by: elanfan1 » Sat Jan 07, 2017 1:52 pm

Can't claim to know the technical answer to this but can give a little story. I was shocked at how low the pressures were for my Sprint when I first got it on the road and I think I must have out about 28lbs in. Returning home on a residential estate so not going fast at all the is a gentle S bend, my tyres screamed/squealed like an American cop car show and what with the noise of the twin cam neighbours must have thought I was hooning (I wasn't). I was actually embarrassed. Adjusted the pressure to the recommended pressure and then on only got squealing when trying.
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PostPost by: el-saturn » Sat Jan 07, 2017 4:44 pm

all i can say is: modern tyres call for the pressure indicated - whether its a racing tyre like a 048 yoko or a a539 yoko - lower pressures would destroy the tyre! if everything is original on your car and you're a cruiser instead of a..........., then i'd stick to the concept: low tyre pressure und soft springs/dampers. sandy 36 / 4982
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PostPost by: mmatthej1 » Sat Jan 07, 2017 7:35 pm

What pressure do you now run ElanFan1 ? Like you, I've been rather askance at low recommended pressure (in this day & age!) but have suck with 23psi on my Sprint.
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PostPost by: Chancer » Sat Jan 07, 2017 11:36 pm

I'm no expert but to me a tyre pressure would be directly proportional to the weight that it carries, if a pressure is indicated on a modern tyre it is likely to be the maximum working pressure corresponding to the maximum weight limit, far in excess of what a light car like an elan would need.

Wider tyres on the same vehicle would probably require a slightly lower pressure, thats just a guess that I'm throwing out for discussion though.

I always use a tyre pyrometer to work out the best tyre pressures on the track and the seat of my pants/comfort to judge road pressures. It does make a real difference, I bought a Ford Galaxy, the tyres were set to the low (unloaded) pressure it had a superb ride but handled like a pig, I put it up to the max load pressures and the handling was brilliant but the ride was nowhere near as good as before, i kept it like that as I infrequently carried large loads, I never experienced abnormal tread wear.
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PostPost by: Robbie693 » Sun Jan 08, 2017 1:02 am

As I understand from my 'O' level physics (!), as pressure is quantified on a unit area (PSI for example) then the tyre pressure should be the same regardless of increasing the tyre size. The pressure itself is chosen for the weight of the car, not for the size of the tyre.

Of course I could be talking out of my air valve... :D
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PostPost by: RichC » Sun Jan 08, 2017 10:09 am

Yes agreed Mike. I run my +2 michelins on 26 front and back from the day in 2009when I pumped them up specially for running round an old airfield racetrack. The standard suspension is nice and soft already. I like the winding country lanes and haven't had any tyre squeal issues or uneven wear since then....but probably haven't covered more than a couple of thousand miles....
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PostPost by: Allison » Sun Jan 08, 2017 10:09 am

Hi guys,
The S3 tyre pressures per the manual are 18 front, 23 rear. But at these pressures with Radial tyres the car is impossible - it squeals on bends and loses the plot on roundabouts and we end up gong backwards. I have moved to 33 or so all round and now it runs on rails.
Again I'm no expert but I do run two Elans over significant distances are terrains and find that the higher pressures are far superior. I suspect its not just a question of weights but also technology, materials and construction which has changed over the last 50 years.

Peter
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PostPost by: el-saturn » Sun Jan 08, 2017 8:47 pm

..........it's especially the cornering speeds which require modern tyres and cornering above average adds 200% more centrifugal force than the regular cruiser does/needs (using 50% of the possible): so an elan turns into a corner at 3000lbs if we quadruple the 50%!! so forget those 155 80 13 things UNLESS you only need a percentage of whats possible sandy: deformed due to 30years in automotive sport!
PS hardly anyone on this forum runs a 105hp elan
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PostPost by: Coupe » Mon Jan 09, 2017 11:05 am

Allison wrote:Hi guys,
The S3 tyre pressures per the manual are 18 front, 23 rear. But at these pressures with Radial tyres the car is impossible - it squeals on bends and loses the plot on roundabouts and we end up gong backwards. I have moved to 33 or so all round and now it runs on rails.
Again I'm no expert but I do run two Elans over significant distances are terrains and find that the higher pressures are far superior. I suspect its not just a question of weights but also technology, materials and construction which has changed over the last 50 years.

Peter


And when Peter states 'across all terrains' he does mean the Amazon, the Arctic Circle and various deserts !!
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PostPost by: Craven » Mon Jan 09, 2017 11:36 am

Increase in grip with higher tyre pressure is usually at the cost of WET grip.
Insurance companies do check tyre pressures if the possible cause of accident is associated with tyres.
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PostPost by: rgh0 » Mon Jan 09, 2017 8:09 pm

On the track you increase your cold tyres pressures when wet to compensate for the fact that the pressures dont rise as much as the tyres dont heat up as much.

On my Elan best handling is at around 31 to 32 psi hot which means around 26 psi cold for the 175 /60 x 13 Yokohama A-048R tyres I am currently using. In the wet i increase cold pressures to around 28 psi and hot pressure will be around 30 to 31 psi.

My Plus 2 with 185/60 x 13 track day Dunlops, on the road i use around 27 PSI cold which in normal road use translates to around 29 psi hot and this gives me the best ride versus handling balance. I use the same pressure all around. Lotus used lower front pressures to put some understeer into the car but i prefer more neutral to a little oversteer handling.

Dont be afraid to test out different pressures and select a combination that suits your tyres and handling and ride preferences. There is no single right answer.

Happy to have a discussion with an insurance assessor any day about the "correct" tyre pressures for an Elan or Plus 2 - some insurance companies have a tendency to look for any excuse to avoid payment - luckily this does not include the one i use.

cheers
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PostPost by: mmatthej1 » Tue Jan 10, 2017 12:04 pm

Interesting comments - think I'll try 26psi (cold) and see how it feels.
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PostPost by: rcraven » Tue Jan 10, 2017 2:19 pm

Have you considered using the chalk test?
You draw a line of chalk across the tread and then drive a short distance over a smooth surface to see whether all or just parts of the chalk line get worn off. This then tells you which parts of the tread are in contact with the ground. Obviously it doesn't show what's happening at speed or on corners (though examining the edge of the tread tells you something about corners) but it can be a useful starting point for setting the pressures.
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PostPost by: Maulden7 » Wed Jan 11, 2017 11:54 am

For day to day driving in my S2 I run at 23psi front & 25psi rear - both from cold (for a more comfortable ride on our poor UK road surfaces) For extended track duty I start at 26psi (cold) all round (this is usually circa 32psi after a couple of laps & sits there) For sprinting I start at 30psi (could be 1psi more or less - depends on the length of the course - cold all round) which rises to circa 32psi by the finish line. I find that around 32psi hot on good dry surfaces gives me the best performance, so need to start a few psi higher when it's wet.

This is using 175x60 Yokos with fully adjustable suspension / LSD etc & circa 145bhp, but I'm planning to change to Kumho Ecsta V70A's soon (same size) so I suppose I'll need to start experimenting again.
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