Tire Pressure -- What's the right thing to do?

[tweetdriver63]

Ok, I know there is the tire pressure recommended by Lotus in the owner's manual. In my Fed Elan, it says 26.5 psi all around. I have searched the net for an answer to this question, and haven't found one. Instead, I've found about two dozen different ones.

Here's the question: Should the recommended pressure be used, regardless of the tire make/model, or is that recommendation based on the original equipment tires only? I'd have to go outside and look, but I know the manual says the only tires recommended are the original Goodyears. I can't remember what model. 26.5 psi just seems really low to me. The factory comes to that pressure based on test performance, economy, etc, using those OEM tires. Different tires have different characteristics (sidewall stiffness, grip, etc), so it seems to me the 26.5 psi is based on the characteristics of those goodyears, 20 years ago.

So, what's the right answer?

[rip]

26.5 may seem a little low by today's standards, but in comparison with other cars, the Elan is quite light & has fairly wide tires. More modern cars are much heavier by comparison so need higher pressure to support their extra weight.

[Monty]

If i`m going for long motorway driving i use 30 PSI, if going for a blat around country lanes 26 to 28 PSI. Track work i`ve been as low as 20 PSI Cold on the fronts as they soon heat up and increase to 28 PSI depending weather conditions.

BTW i wouldn`t class the Elan as a light car

[rip]

BTW i wouldn`t class the Elan as a light car

Compared to a track-prepared car, it isn't.
I was comparing it to a modern family car which needs higher tyre pressures & has them marked on the door pillar.

[Monty]

BTW i wouldn`t class the Elan as a light car

Compared to a track-prepared car, it isn't.
I was comparing it to a modern family car which needs higher tyre pressures & has them marked on the door pillar.

How can you compare a 2 setter to a family car

Just looking at the manaul and the NA pressure is 32lb, that seems strange since the NA will be lighter. So quite a difference between the SE & NA

[bobbrown]

I run my naturally aspirated Elan at 1.8bar as I could not see why it should be that different to the SE, tyre wear is fine as is handling.
My Astra is 2bar and is only a little heavier at 1100kg (kerb weight)

Bob

[rip]

How can you compare a 2 seater to a family car

From the point of view of the tyre, what's the difference? They are both vehicles which must be supported & the pressures are there to keep the tyres at the correct shape so they work properly, so a heavier car requires more pressure or a greater contact area.

[mvf906]

hi, having just replaced all four tyres (under £200 delivered for Toyo T1R's from camskill, if anyone interested) I could also do with knowing the correct pressure, my local garage, who fitted the tyres put 30psi in as they couldn't find any data on it but said 30 was prob too high

[bobbrown]

Service manual states 1.8bar (26.5psi) for SE and S2 and increase to 2bar (29.5psi) for continuous speeds in excess of 100mph.
NA is slightly different for some reason but on mine I run 1.8bar all round with out any issues on Yoko C drive's.

Bob

[John_W]

mvf,
Service Bulletin 1996/01 (attached) quotes :
1.8 bar f&r for SE on the original kevlar-walled 15" MXX-2s but 2 bar f&r for the replacement MXX-3 Pilots.
1.8 bar f&r for US on 16" Goodyear Eagles, but 2 bar on Pirelli P-Zeros
2 bar f&r for S2 on Michelin Poilots or Pirelli P Zeros

As you're not using any of these tyres, you can take these pressures as a starting point I guess.

John

[mvf906]

ta john & bob, have put 1.8 bar in.
martin

[woody]

I've got a problem with my rear tyres deflating about 2-3 psi every week.Have taken the wheels to tyre experts, and they verify the metal valves are ok, and the leaks are coming from the joint between bead, and S2 alloy rim, in about 5 or 6 different places.
Some tyre fitters say it needs "porridging" with tyre sealant on the inside of the alloy rim, and around the tyre beading.When dry the tyre is refitted.
Others say the alloy wheel needs resprayng on the inside rim.The tyres are 215/45/16 on the rear, and 205/45/16 on the fronts, all the same make.
All 4 wheels were refurbished about 3 years ago, so it seems strange only the rears are affected.
Has anyone had expierience of this problem.
Cheers,
Woody

[theelanman]

its that question again.....
why do you have bigger on the back than the front?....
what is the max safe width you can have on the rim?...
is it the rears or the fronts or all of them???

I know some people have wider tyres but on different rims.....

personally Ive always gone with the manufacturers recommendations as thats the way it was designed...
sorry getting off topic......

have you looked at the rim where the bead sits????....has it got corrosion????...if so this could be the problem...and the answer to that is a wire brush

[Elanlover]

mvf,
Service Bulletin 1996/01 (attached) quotes :
1.8 bar f&r for SE on the original kevlar-walled 15" MXX-2s but 2 bar f&r for the replacement MXX-3 Pilots.
1.8 bar f&r for US on 16" Goodyear Eagles, but 2 bar on Pirelli P-Zeros
2 bar f&r for S2 on Michelin Poilots or Pirelli P Zeros

As you're not using any of these tyres, you can take these pressures as a starting point I guess.

John

Perhaps a stupid question but are these ratings for cold or hot tires?

[tweetdriver63]

cold.

[Elanlover]

26.5 psi cold then.

[Camalot]

Summary: The final comment was 26.5 then, which was NOT correct conversion of 2 bar recommendation. The 1996 Lotus service bulletin said all 2 bar which is 29 PSI not the 26.5 in the owners manual.

The US Spec Owners Manual Bar/PSI for front & rear is wrong conversion bar to PSI. Also most cars have different front / rear pressure especially if Front wheel drive due to weight at axle variations. Elan M100 almost 2x (1.9) more weight at front. But the original # or lower, makes more sense for the rear.

Front Bar Front PSI Rear Bar Rear PSI Comment
US Owners manual - wrong convert bar (both)
Normal 1.8 26.5 1.8 26.5
High Speed 2.0 26.5 2.0 26.5
Srv Bulletin 2.0 29.0 2.2 29.0 replacement tires

Bar to PSI (correct math)
Normal 1.8 26.1 1.8 26.1
High Speed 2.0 29.0 2.0 29.0

Formula by Axle Wgt
Normal 1.96 28.5 1.23 17.8 Below 22 psi unsafe

My thoughts
Normal 2.0 29.0 1.65 24.0 per service bulletin (front)
High Speed 2.0 29.0 1.79 26.0 no service updates

Racing applications: For racing cars, specifically very light ones (under 800kg 1763 lbs), the recommended pressure range is between 22 and 29 psi. Which if 50/50 would be 881 lbs at axel.

Elan M100 lbs
Front 1693
Rear 887
Total 2580

[dapinky]

Well, apart from the maths being wrong (but such is life with typos), it is important to realise that the original pressures would have been decided after the road testing of the car ON THE OE TYRES...... and tyre tech has moved on since then, as have other things.

The published pressures don't allow for height above sea level or temperature..... or weight of driver.... or loads of other things - it is really just a starting point.

I usually pump mine to 27psi all round, and that is good for me.

[MPx]

I keep mine on 2 bar (29psi) as per the manual. Seems to work well...but that is on very old tyres that aren't supposed to work anyway!!

[Tuga2112]

i used to run it on 30 PSI.
then had some "road wondering" on motorway which made me reset to 24PSI
changed tyres and put 26PSI and the road wondering disappeared

currently running at 26PSI

after reading your comments ill revert back to 30.

every since i have dropped to 24PSI i never been able to get my 40MPG (with average of 36-38)