At a very [color:“red”]hot[/color] Oulton Park yesterday, I tried Gavan Kershaw’s recoomended ON TRACK tyre pressures for the first time.
Gavan suggested 28psi ALL ROUND once the tyres are hot. Car handled beautifully (for a duffer like me), with no hint of understeer at all
To put this into context, Gavan was the Lotus engineer responsble for working with Yokohama to develop the tyre compound/carcass specifically for the Exige
Pesky,
I tried them like that, and I still found the wear pattern to be more in the centre.
I also found more grip at 24 psi hot, that translates to about 18 psi cold.
This figure was later confirmed by Kelvedon Lotus (don’t remember who I spoke with, but seemed to be the owner)
If you see your tyre wearing still more in the middle and the edges not used/feathered, try the lower ones.
Uldis
28 is a good starting ;point, but that finnal optimum will depend on a shed load of other stuff (mostly Geo).
best way to work it out is a tyre temp gauge.
28 is a good starting ;point, but that finnal optimum will depend on a shed load of other stuff (mostly Geo).
best way to work it out is a tyre temp gauge.
Lord Scuffham
I’m a thick git, so how does one get the benefit from the temp gauge? Is it just simply aiming to set the car up so that the temp is even across the tyre?
Thanks in anticipation of your words of wisdom
Basically, yes.
in reality, what your aiming for is the same temp on the inside edge of the tyre and the centre, with the outside edge ~10C lower.
to get there, you need to play with pressures and chambers, ie. if the outside edge is hotter than the inside, you need more camber, etc etc.
I would see the advantage of a Pyrometer being the exact temperature of the tyre, like for choosing a compound over another, but if the wear pattern, or heat on one side Vs another is what you’re looking for, just putting your hand across when warm would suffice, right?
Then you would know if the pressure is too high, low, or if you need more camber, but very diffucult to measure toe like that.
I very much doubt that you can tell from you hand the difference between say 60C and 75C…
Also, it’s not the surface temp your looking for, temp probes are for getting the temp under the surface of the tyre.
For example, if the tyre temps are even, but much over 75-80C then you are working the tyre too hard, so you need to start looking at changing the geo, ie. reducing the toe are the rear (for rear tyres).
Don’t doubt.
Have you ever figured out that your kid has fever by touching their forehead?
Even if these temps are highre, you CAN notice a 3 degC difference, you can’t know how much it is, but you will see if you need to do something or not.
And regarding the absolute readings, you’re right, you need one to figure out if your compound is right and/or you need to change geom. setup.
And don’t forget the wear “pattern” (how feathered is the tyre, where, etc), one of the most important things to look for.
Sorry?
3C - year right…
As for ‘feathering’ it’s a bit late by then…(unless you have a BIG tyre budget!)
I have just fitted 048s, and have run them for about 100 miles to settle them in. I put 23 in the fronts and 26 in the rears for road use, but I could do with some advice…
No work has been done on the suspension.
AS a pointer, after a quick thrash this afternoon, the inside of both fronts and rears felt hotter than the centres, and the outsides were almost cold.
Mike
Simon is probably best to help with your set up.
I spent some time on track (dry)at Anglesey over the weekend. The circuit is tight, twisty & ideal for Exiges & Elises. My front ARB is presently set in the middle position. I started with the 28psi (hot)all round, but found that it was undsersteering like mad, & I just didn’t feel as confident as usual on the corners. I then dropped the front presuures down to 25psi & felt a lot happier, although there was plenty of wheel/arch liner contact, even when driving solo.
I’m now going to stiffen the ARB, but my next scheduled trackday is 24th September at Donington with http://www.bookatrack.co.uk so I won’t be able to test the difference for a while.
By the way, big thanks to Russ for letting me take Pesky Minor (aged 13) out in the Blink fettled Exige-R - it was his first experience of being out on track, & he’s now hooked!!!
I still cringe when I see so high pressures.
Last trackday at KH I went for 23 psi hot, that translated to 19 front and 17 rear (cold).
Of course I would not use these on the road, more like 20 even, but otherwise you’ll see the centre of the tyre wearing out in the middle (sure sign of overinflation)
But definitely don’t use 23 & 26! (I did, and it was wrong!)
Uldis
I got this from a Lotus dealer after i show them my tyre wich has worn in the center
I have spoken with a Lotus workshop about tyrepressure and why they have worn in center.
Here is the answer:
Tyre pressure shall be 1.8/2.0 on track. Lotus Motorsport has recently told me that. When you have too low tyrepressure in low-profile tyre, they worn in the center first. Why? Yes, since there is not enough pressure against the tyreside inside the tyre, the centrifugal force will take over
and slung the center out during high speed and hard accelaration. The reason that the left tyre is more worn then the right, is because of a torque-reaction through the driveline. Cars that have transvers engine and gearbox is wear more on the left tyre because of one driveshaft is longer then the other. The left shaft is the shortest of the two.
Torque-steer:
“A tendency for a car to turn in a particular direction when power is applied. Torque steer is common in front-drive cars because reaction forces created in the half-shafts can generate uneven steering forces in the front tires.”
What a load of nonsense.
Proof of that is that when using their recomemnded pressures, tyres wear in the middle, and after a couple of laps I have no traction.
When using the lower tyre pressures that I mention I never lose traction and the tyres wear evenly.
With that reply they are covering their arses only.
Ding Uldis - that is pretty much what I told him on Seloc when the same question was asked. Whichever lotus technician told him that was talking utter rubbish.
Underinflation causing central wear! So what do they think happens when you overinflate the tyres?
What a load of nonsense.
Proof of that is that when using their recomemnded pressures, tyres wear in the middle, and after a couple of laps I have no traction.
When using the lower tyre pressures that I mention I never lose traction and the tyres wear evenly.With that reply they are covering their arses only.
I guess that there are probably slight differences with suspension set ups from car to car; however i tent to run quite a stiffly set car front to rear and agree exactly with Uldis and his tyre pressures. I get a sliding and understeer with the higher pressures which dissapears once i lower them right down to 23/24 when hot.
The reason why the left tyre is more worn than the right is probably that most tracks go clockwise, so you’re bound to get more tyre wear on the left.
The only tyres I ran at the Lotus recommended pressures were the standard Bridgestone RE040s on my old S2.
Yours were difinitely over inflated and look like they’ve been flat spotted too.
since there is not enough pressure against the tyreside inside the tyre, the centrifugal force will take over and slung the center out during high speed and hard accelaration.
Its almost believeable - if you watch a drag car taking off the change in the height of the vehicle is amazing as the tyres change from low profile fats to high profile thins.