Tyre Pressure

[rogerch]

Following on from my dilemma over toe in, I have looked at LEW for tyre pressures for my stevens, it says 21/25 psi I feel that is about 4 psi low, I know, I know trust the book, but reckon 25/30 psi. Any body else?

Roger

[SE Owner :-D]

27

[esprits4de]

R&B recommends 2,0 BAR ( thats 29 psi )

My personal feel is at 2,2 BAR but I stick to 2,0....

[tje111]

I do 30 for street and 32 for track days.

Yours aye,

Tom

[rogerch]

Are you guys saying you use the same pressure on all 4 wheels?

Roger

[Bibs]

The Esprit is very sensitive to tyre pressure, you can't guess at it or you will seriously affect the handling of your car.

Use what it says in the manual or call Lotus and ask them.

[Mark Blanchard]

30 on all (Running on SE size Goodyears). Front's seem to drop down to 25 after a month or two .

[Paul C]

Is odd that the -88 turbo has tyre pressures different front and back:

Front Normal use 1.5 bar (21 lb/in2) Sustained speeds 149+mph N/A .

Rear Normal use 1.7 bar (25 lb/in2) Sustained speeds 149+mph N/A.

But the SE is quoted same pressures on all corners:

Front Normal use 1.8 bar (26 lb/in2) Sustained speeds 149+mph 2.6 bar (38 lb/in2)

Rear Normal use 1.8 bar (26 lb/in2) Sustained speeds 149+mph 2.6 bar (38 lb/in2

I keep mine at 32lb on all four. For example, when i pop down to castle combe again on

sunday, i'll have 50% windy and bumpy country roads, and 50% motorway, i find the '32'

a happy medium as i'm not being shaken off the corners on the rough stuff, but am still

stable at speed on the flat stuff.

[DBredS4]

29 psi front 30.5 psi rear in the manual for an S4

Unless sustained speeds over 240Kph then 36.5 psi ???

V8 is (normal) 29 psi front and rear.

Unless sustained speeds over 240Kph then 36.5 psi ???

Surely the extra heat will make it EVEN HIGHER! End up ballooning the tyre. Especially the wider ones..

I believe you're supposed to lower the pressure for track days. Any comments...

Also, I noticed on one of the F1 races that if they didn't keep the tyres warm then they lost some pressure (Boyles Law etc) and the tyres went all wobbly.

Edited August 10, 2008 by DBredS4

[ramjet]

Two years ago I went on a defensive driving course at the company I worked for and the instructor gave us several interesting pointers.

1) Manufacturers recommendations on cars are weighted toward passenger comfort, not tyre longevity or higher rated performance. His recommendation was about 4 psi higher than the placard or manual.

2) A higher inflated tyre will actually increase in pressure less (as a ratio) than an underinflated tyre. An underinflated tyre will have excess tyre wall flexing which is one of the main contributors to heat build up as it is inside the structure of the tyre. Friction of a tyre against a road surface does not contribute that much. (except for a burnout)

3) An underinflated tyre, when subject to high braking or accelerating loads, compresses the loaded point of the tyre. If you get a cross section of a tyre and put it against the ground and then push on the side walls to simulate increased load, the central tread area will actually come away from the road surface effectively decreasing your tyre to road contact considerably. Something like 65% if remember corrrectly.

I have since run all my cars 4 psi higher than recommended. Having said that, I am talking about everyday suburbia cars not performance cars like an esprit. Higher end sportscars may ignore the passenger comfort aspect and list pressures biased more toward performance. But it is still a car and manufacturers want to sell them.

Michael.

[Paul C]

A a side note, even main dealers have no idea. When my (car derived) van goes into

my local vauxhall dealership for service, they always return it with the tyres deflated

to the to that of the car it's based on, and not the figures quoted for the van. Anyone

that takes a loaded van for service, drives it away in an unsafe state.

So after every service, i then reverse what they have done, as the side with my vault (tool safe)

above it comes back looking flat (and obviously dangerous). I just let this carry on as i like to

check it over post-service as after past experience with the vauxhall dealer network i know to

check basic and simple safety items once they have meddled with them, also i now check all bulbs,

washer jets and wipers before putting it in, as they always try to bang at least one of these on each

service as a kind of 'cash cow' bonus to themselves.

Company van. Obviously i would not let them touch anything i owned, as they could not

service a tin opener without setting it up wrong, or breaking something. We now buy VW's

soley due to a consistantly bad service on all of our vans by various vauxhall dealers.

[ramjet]

Two years ago I went on a defensive driving course at the company I worked for and the instructor gave us several interesting pointers.

1) Manufacturers recommendations on cars are weighted toward passenger comfort, not tyre longevity or higher rated performance. His recommendation was about 4 psi higher than the placard or manual.

2) A higher inflated tyre will actually increase in pressure less (as a ratio) than an underinflated tyre. An underinflated tyre will have excess tyre wall flexing which is one of the main contributors to heat build up as it is inside the structure of the tyre. Friction of a tyre against a road surface does not contribute that much. (except for a burnout)

3) An underinflated tyre, when subject to high braking or accelerating loads, compresses the loaded point of the tyre. If you get a cross section of a tyre and put it against the ground and then push on the side walls to simulate increased load, the central tread area will actually come away from the road surface effectively decreasing your tyre to road contact considerably. Something like 65% if remember corrrectly.

I have since run all my cars 4 psi higher than recommended. Having said that, I am talking about everyday suburbia cars not performance cars like an esprit. Higher end sportscars may ignore the passenger comfort aspect and list pressures biased more toward performance. But it is still a car and manufacturers want to sell them.

Michael.

Ok. Further to this, since I have just had new tyres all round. I am now running Roadstone N3000's on all four corners. The showroom original Eagle G-SA's having been relegated to the bin. The rears were on the wear markers, the fronts only half worn, but the tread blocks were showing signs of cracking from the tyre base. Stoopid me did not read the manual before getting to the shop when the rears were done. We put 32 psi in the rears and the fronts were on 28psi. Test drive and on a bumpy LH corner that I thought we would be fine on, nearly saw myself and the tyre guy in the trees at 160km/h. Double fishtail when the rears left the road surface, when they touched down again, there was no slip but I had corrected for the rear stepping out so now the car shot off to the right, corrected for that when the rear hopped again and now we ended up 160km/h in the RH lane facing an oncoming car. Tyre guy needed to change his pants, I was too busy keeping everything together to get scared. Needless to say it was a moment. So driving far more conservatively to get home and check the manual to find 29 for the front and 30.5 for the rears as was stated earlier.

That is what is now in my car. I withdraw all the comments in my quote above in relation to my S4. For normal tyres on normal cars it still applies, but in my opinion as Bibs said earlier as well, the esprit is very sensitive to tyre pressures. For better road conditions on a track day, maybe go up a bit but IMO a 4 psi increase may well be too much to the point of being dangerous.

The esprit is incredibly forgiving of errors in driving, provided you react quick enough. My VT commodore would have killed me. Tyre guy thought we were dead.

Michael.

Edited December 17, 2008 by ramjet

[DanR]

Michael if that spin was on fresh tyres it could also be due to the tyres' slippery mould release agents. It is usually advised not to push new tyres for at least the first 100k's or more to wear the agents off.

[rogerch]

From your description you may have an imbalance in your shocks allowing weight transfer to front too quickly. Worth checking.

[mr.oogieboogie]

30 psi front and 30 psi rear

[fjmuurling]

I run 2.1 bar (=30.8 psi) on all for corners in my 1990 SE.

Freek

[Vulcan Grey]

I run 30psi F/R on my V8 wheels for street.

My friend does 25psi in his X180-R for track days.

I will adjust my tire pressure F to R to change the handling. If the car is understeering, reduce front pressure a bit at a time. If the car is oversteering, adjust the rear pressure down a bit.

My Honda Integra is spec'd at 33F/31R, if you rotate the tires (31F/33R) without adjusting the pressure, the car becomes very easy to oversteer drift on a sweeping turn... And that is a FWD car!

[fflyingdog]

My S4s is very sensative to tyre pressures if the front are low it will pull to one side quite violently but when tyres inflated correctly behaves perfectly ,i use 29 psi front and rear as per Lotus maintenace manual.

Nick S4s

[Road Stone]

I follow the books instructions. But then I really don't push the car too hard. Not all the time!

[benjamincalleja]

This was really answered RE the 21 psi front 25 psi rear question. What should it be now with more modern tires? Can someone ask the factory, I can't find an email for them that works.

[rogerch]

First up what tyres are running and what is the recommendation for those tyres ?

I have and still do run 28 front 30 rear, Pirelli, just changing to Toyo using same pressure.

That said it suites my driving style, others may not like it, but you'll only vary by 2 psi or so.

If you don't have power steering you will find it hard at less than 28psi.

[andydclements]

This was really answered RE the 21 psi front 25 psi rear question. What should it be now with more modern tires? Can someone ask the factory, I can't find an email for them that works.

The ideal pressure will vary by tyre brand and tyre product. It's more a question for the tyre manufacturer.

[Bibs]

When I asked Lotus they said to inflate them to 10% less than the max on the sidewall then adjust down to taste.