Tyres 40%track and 60% road...
- Thread starter stevespic
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Diver944
Active member
Obviously there is a possibility that some types of tyre will cause a problem when different types are used front to back but I know I have virtually always had different types and never felt a problem. One of the old hands on Titanic had a big problem when he had two different types of Avon ZZ tyre on front and back and that went away when he changed to all four of the same type.
This random lane changing sounds a bit extreme [
] are they definately balanced correctly and the wheel buts done up tight? []
One thing I would say is that 2.8 bar (42psi) seems quite high (I know the book on the 1990 models says 36f and 44r). I used to run my 16" on 32f and 34r unless on a long run with luggage and I'd increase the rear a little.
Best find a car park and do some donuts to break them in quickly []
This random lane changing sounds a bit extreme [
] are they definately balanced correctly and the wheel buts done up tight? []One thing I would say is that 2.8 bar (42psi) seems quite high (I know the book on the 1990 models says 36f and 44r). I used to run my 16" on 32f and 34r unless on a long run with luggage and I'd increase the rear a little.
Best find a car park and do some donuts to break them in quickly [
]
TTM
Well-known member
Yes, wheels were properly balanced and bolted.
I tried T1S tyres (on my spare CS wheels set), a friend kindly let me try his old but still fine F1S yesterday and the handling was "as it should be" with both. I also played with different damper settings, to no avail.
I will first stand by Steve's comment and put some more miles on them trying not to hit any lamppost.
I think the lane changing is due to me naturally steering left/right in order to follow the sideways movements of the rear of the car caused by the sidewalls being so soft - driving a front-engined 911 3.2 does feel strange [&:]
I tried T1S tyres (on my spare CS wheels set), a friend kindly let me try his old but still fine F1S yesterday and the handling was "as it should be" with both. I also played with different damper settings, to no avail.
I will first stand by Steve's comment and put some more miles on them trying not to hit any lamppost.
I think the lane changing is due to me naturally steering left/right in order to follow the sideways movements of the rear of the car caused by the sidewalls being so soft - driving a front-engined 911 3.2 does feel strange [&:]
Neil Haughey
New member
So I am not alone then in this thinking. I have Hankook RS-2's at the moment and Hankook recommend 40psi hot for R compound tyres, whereas many track dayers run much lower pressures. On the track they only went off with about 44 to 45 psi in the rears and 42psi + on the front which means that 40 psi hot is probably spot on.
Recently I decided to increase my road pressures back up to 36 front 38 rear cold and the grip / handling improvement is dramatic. Even with 2 degrees -ve camber on the front the car tracks brilliantly in the rain, the lack of sudden weight transfer meaning that consistently higher speeds can be maintained without ever pulling much G.
Just watch the tyres limits though! I was booting it past a truck in the rain last week and lost traction changing from 2nd to 3rd. Lets just say that the speed at which the grip went and then came back again could be best described as violent. The bloke behind went very pale when my car skewed one way then the other.
Mental not to self, don't boot it in the rain even in a S2.
Hilux
New member
This random lane changing sounds a bit extreme [
One thing I would say is that 2.8 bar (42psi) seems quite high
I would say its due to the `very` high pressures. 42psi is v v high, the car only weighs some 1300kg! I run 28psi and a dry track brings them up to about 33/34 with even wear and mild overheating due to the newness of the trad blocks.
Alternative is tracking out (likely) or even camber.
TTM
Well-known member
Well, in my case 2.8 bar (42 psi) allowed for a less dangerous handling than 2.5 bar (36 psi) as more pressure would certainly make for less sidewalls flex.
Talked to a couple of locals yesterday evening who experienced the same with this tyre, although not on 944s.
If it does not improve with mileage as per Steve's observation I will be tempted to think :
- we on the continent do not get same compound tyres as in the UK
- I was sold a set of faulty tyres
- they may work only when fitted all round
Diver944
Active member
Certainly sounds an odd one [&:] but then I think tyre choice and 'feel' is a very personal thing, you only have to see our many and varied recommendations to work that one out.. Let us know how you get on because thats certainly the first time I've heard a less than positive remark about those Toyos
Hilux
New member
The original suspension was designed with tyre flex in mind. I know Porsche recommended (I believe 42/44 psi or similar) but I cannot believe it is correct for the car. Modern suspension allows for low profile tyres and will have softer springing and harder damping otherwise the lack of sidewall flex will make it bounce all over the road.
All I can say is that personally I`ve not had overheating nor wear on both outer edges of the tyres (which low inflation tends to promote). I believe also that the majority of us run low to mid 30`s ?? I have driven in anger against other 944`s on track and dont consider the handling more dangerous.
The only difference I have noted is that at 28psi (32/33 ish hot) with Mo30 dampers (old) and ARB`s the outside edges feathered but with KW V3 and W/m ARB`s the tread wear was completely even as were the temps so they are definitely not underinflated at those pressures with much reduced roll ensuring more tyre contact with the road.
Before I lowered the pressures the tyres ran nearly 44psi and got hot very quickly.
I suppose its all down to tyres and conditions but it would be useful to hire a runway and some cones and see what g is achieved and what speeds achieved with differing pressure and set ups.
Anyone up for an experiment?
All I can say is that personally I`ve not had overheating nor wear on both outer edges of the tyres (which low inflation tends to promote). I believe also that the majority of us run low to mid 30`s ?? I have driven in anger against other 944`s on track and dont consider the handling more dangerous.
The only difference I have noted is that at 28psi (32/33 ish hot) with Mo30 dampers (old) and ARB`s the outside edges feathered but with KW V3 and W/m ARB`s the tread wear was completely even as were the temps so they are definitely not underinflated at those pressures with much reduced roll ensuring more tyre contact with the road.
Before I lowered the pressures the tyres ran nearly 44psi and got hot very quickly.
I suppose its all down to tyres and conditions but it would be useful to hire a runway and some cones and see what g is achieved and what speeds achieved with differing pressure and set ups.
Anyone up for an experiment?
Neil Haughey
New member
Why bother. If the tyre manufacturer says the tyre makes its best grip at say 200 F then buy a pyrometer with a probe and take measurements after several laps during which the car feels optimal. If the temp average on each tyre is the same on all 4 corners then you know the pressure ratio's, suspension setup etc is pretty well balanced and if the distribution across each tyre is fairly evenly* around the target temp then you know that both the pressure is correct and the geometry for that wheel.
(* the website for my tyres reckons that it should be 20 F higher on the inside edge then the outside edge)
Note that this is from the viewpoint that the correct setup is the one which delivers the best performance rather then what may feel right to the individual.
(* the website for my tyres reckons that it should be 20 F higher on the inside edge then the outside edge)
Note that this is from the viewpoint that the correct setup is the one which delivers the best performance rather then what may feel right to the individual.
TTM
Well-known member
Update : have driven about 600 miles last weekend and the new T1R fitted at the rear have slightly improved ; the initial bouncing has decreased but still noticeable at speeds above say 90 mph at which the rear of the car remains over sensitive to direction changes. Dry grip is excellent, and I hope sidewalls will stiffen up even further with more miles being put on them.
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