Digital Mouth Posted 8December, 2012 Report Share Posted 8December, 2012 What is the correct psi for a 19" Inch Wheel? Front & Back. Link to comment Share on other sites More sharing options...
T-Man Posted 8December, 2012 Report Share Posted 8December, 2012 Front 32 Rear 34 Cold pressures. Link to comment Share on other sites More sharing options...
Jimmy Posted 8December, 2012 Report Share Posted 8December, 2012 Front 32 Rear 34 Cold pressures. Porsche recommends Front 36 Rear 44 My tyre guy recommends 38 Front & Rear for the Australian roads, now whos right? Link to comment Share on other sites More sharing options...
T-Man Posted 8December, 2012 Report Share Posted 8December, 2012 Porsche recommends Front 36 Rear 44 My tyre guy recommends 38 Front & Rear for the Australian roads, now whos right? That's straight out of the 987 Boxster S owner's manual.........interesting! Link to comment Share on other sites More sharing options...
Digital Mouth Posted 8December, 2012 Author Report Share Posted 8December, 2012 I'm currently sitting on 40 front & back Link to comment Share on other sites More sharing options...
Niko Posted 8December, 2012 Report Share Posted 8December, 2012 I'm currently sitting on 40 front & back 29 front 36 rear is what my 986 manual says summer and winter. I think that is weird but that,s the recommendation. Not sure how that relates to 19" wheels standard wheels for your 986 are 17" . Mark would be the man to guide you, if he is watching this. I normally have been running 29/36 but have found fronts are still 80% after 24000 k,s but rears down to about 40% or as traction tyre s told me last week probably 5 to 10 thou left on rears. Recently decided to run 34/36 and noticed handling seemed to improve on SMT,s although a bit more under steer on the higher front pressures. Hope that helps a bit D.M. for what it is worth. BTW Have you checked your car manual that hopefully came with your car. Yours is earlier model than mine and may be different. Possibly it is stuck under your steering wheel in a holding bracket, you may not have noticed it there. Link to comment Share on other sites More sharing options...
Digital Mouth Posted 8December, 2012 Author Report Share Posted 8December, 2012 I checked my manual and it reads the same as yours. I'll try 34/36 and see how that goes. Link to comment Share on other sites More sharing options...
Niko Posted 8December, 2012 Report Share Posted 8December, 2012 DM I think you have modified your post, but FYI I am still running 17" wheels. The 34/36 should be a better pressure than 40/40 for road use, plus not as harsh a ride. IMO The higher pressures ie 40 might be more suited for track work Link to comment Share on other sites More sharing options...
Jimmy Posted 8December, 2012 Report Share Posted 8December, 2012 DM I think you have modified your post, but FYI I am still running 17" wheels. The 34/36 should be a better pressure than 40/40 for road use, plus not as harsh a ride. IMO The higher pressures ie 40 might be more suited for track work Correct me if I'm wrong but I thought lower tyre pressure is best for track as heat builds up and increases pressure. Link to comment Share on other sites More sharing options...
Niko Posted 8December, 2012 Report Share Posted 8December, 2012 Higher tyre pressures assist in stopping the tyre rolling off the rim when cornering. Also stops flexing in the side wall, Lower pressure and first serious corner and your tyre s will be rolling off the rim. Tyres will certainly go up a couple of extra pounds once hot, but your pressures that you are running are always set when cold for uniformity. Slicks or racing rubber may be different, but radials need to be higher tyre pressures is my understanding. Link to comment Share on other sites More sharing options...
Jimmy Posted 8December, 2012 Report Share Posted 8December, 2012 Higher tyre pressures assist in stopping the tyre rolling off the rim when cornering. Also stops flexing in the side wall, Lower pressure and first serious corner and your tyre s will be rolling off the rim. Tyres will certainly go up a couple of extra pounds once hot, but your pressures that you are running are always set when cold for uniformity. Well that does make sense and the car does feel more stable and rigid with higher pressure but got different opinions after speaking to people who tracked their cars. I guess you should go with what feels right at the drivers seat. Link to comment Share on other sites More sharing options...
Niko Posted 8December, 2012 Report Share Posted 8December, 2012 The old Jim Murcott driving course held at Sandown used to have all the students in the class room and have one of the trainers out in the car park checking the tyre pressures on the cars the students had brought along. Then the trainer would come in with the stats on what cars had what pressures. The students who had low pressures we're sought out. Some students were running very low (18's) to medium (24's 26 etc) They had been told before the course to turn up with higher tyre pressures 36 and higher. Police driving courses also ran very high 30's to low 40's on the circuits when going for "pursuit" licences. Link to comment Share on other sites More sharing options...
Jimmy Posted 8December, 2012 Report Share Posted 8December, 2012 well there you go, can't argue with that. Link to comment Share on other sites More sharing options...
Niko Posted 8December, 2012 Report Share Posted 8December, 2012 Mate, each to their own, but personally I would prefer to be on high pressures on a circuit than low pressures. Normal road driving, you can certainly get away with lower pressures. Keeping in mind recommended pressures by the manufacture of the car will most of the time he lower than what a tyre company will recommend. The car company looking for compromise of handling and comfort, so most "normal" people are happy with that. The car handles ok for most conditions but occupant comfort is high on the agenda. The tyre company want your tyres to perform as a first priority, with occupant comfort running second. I go by what the tyre company recommend. Link to comment Share on other sites More sharing options...
Jimmy Posted 8December, 2012 Report Share Posted 8December, 2012 Mate, each to their own, but personally I would prefer to be on high pressures on a circuit than low pressures. Normal road driving, you can certainly get away with lower pressures. Keeping in mind recommended pressures by the manufacture of the car will most of the time he lower than what a tyre company will recommend. The car company looking for compromise of handling and comfort, so most "normal" people are happy with that. The car handles ok for most conditions but occupant comfort is high on the agenda. The tyre company want your tyres to perform as a first priority, with occupant comfort running second. I go by what the tyre company recommend. I have always preferred the feel of higher pressured tyres. Link to comment Share on other sites More sharing options...
9fan Posted 8December, 2012 Report Share Posted 8December, 2012 Track vs street are slightly different because track temps inc more after run. Opinions will vary but I have found Street F34/R32 cold dependant on F/R balance are good for 50/50 balance dependant on weight.. 911 would probably be Street 34/36 because rears would heat more and heavier. Again track temps depend on type of circuit and Outside Air Temp ! Track suppliers recommend around 36 Hot with R type tyres. So let the debate continue, but use Porsche Car info as guide ! Cheers,Mark. Link to comment Share on other sites More sharing options...
Niko Posted 8December, 2012 Report Share Posted 8December, 2012 Your right Mark, I have been referring more to non p cars, above, and just running normal street type radials. So back to real cars.. I guess if you are running R types or racing rubber with very low profiles on the circuit the higher pressures are not required? With all the various porsche characteristics etc it really does open up a can of worms. Then when we change the wheel diameters from the original wheels with the lower profile tyres it all starts to become a "suck,it and see" . Link to comment Share on other sites More sharing options...
9fan Posted 8December, 2012 Report Share Posted 8December, 2012 The old Jim Murcott driving course held at Sandown used to have all the students in the class room and have one of the trainers out in the car park checking the tyre pressures on the cars the students had brought along. Then the trainer would come in with the stats on what cars had what pressures. The students who had low pressures we're sought out. Some students were running very low (18's) to medium (24's 26 etc) They had been told before the course to turn up with higher tyre pressures 36 and higher. Police driving courses also ran very high 30's to low 40's on the circuits when going for "pursuit" licences. For these performance courses you need higher pressures because street tyres have softer sidewalls and will be subjected to higher side loads. Another guide to suitable pressures road or track is to check where the wear contact shows at the edge of the tyre. Most tyres have small triangular arrows on the lip of the tyre which indicate where the contact patch extreme would be,exceed that and you are not running enough pressure. If wear contact further in then too much pressure or in either case wheel CAMBER comes into play especially on track. Soooo let the debate continue ! Link to comment Share on other sites More sharing options...
Niko Posted 8December, 2012 Report Share Posted 8December, 2012 The tyre technician at Traction Tyres while fitting my new wheels, asked if I track the car. I replied never, to which he said the fronts showed a bit of fairly aggressive driving. To which I can only summise due to SMT's. he suggested putting a bit of camber on. That's all a bit out of my depth, rather not play around with that stuff so I declined. Also interesting if not frightening thing re the Murcott course, some of the people attending in their DD cars had a mere 18lbs in their tyres. (One bloke had 14 in one tyre) They admitted they never checked pressures, and did not have any idea apart from improved handling, the safety issues or lack of.....running on low pressures. These were people interested in improving their driving skills, so what about the people out there driving around who couldn't give a rats bum about their driving skills or tyre condition. Apart from driving a car that would handle like a bowl of gold fish, it,s not going to stop when you want it to stop. Apart from the other non handling features. Scarey stuff. Tyre pressures probably the easiest to monitor and most important safety issue of a car. IMO. Link to comment Share on other sites More sharing options...
Chris-p Posted 8December, 2012 Report Share Posted 8December, 2012 Good info guys. Appreciate the advice Mark. I am currently experimenting with pressures since I put the new suspension and engine mounts in I noticed an increase in understeer. Admittedly the corner speeds are much higher than they were but still thought I would do some research and see what I could find. I had the pressures set at factory recommended f36/r44 which to me gave way to hard a ride and made the rear jump around. After talking to a number of people including Calvin at Jocaro who are far more knowledgable than me. I have started to reduce and see what that does to the feel of the car and handling. I am at f34/r38 at present and its made a huge difference and dialed out the understeer at the speeds I am prepared to drive at. The final setting will be f32/r36 just to see if there is any difference. Niko I agree with your comments re the murcott course. I did it more than 10 years ago and they found the same thing when they checked all the participants pressures, very scary, considering they had contacted us and told everyone to turn up with 34psi front and rear.... C Link to comment Share on other sites More sharing options...
T-Man Posted 8December, 2012 Report Share Posted 8December, 2012 The real question here is "what does Porsche recommend"? Now since 19s were never a spec wheel on a 986 there is no documentation supporting that. If you look at the 993 there is a ridiculous difference in pressure between 16/17/18, and as Chris has mentioned above the factory recommendations on 18s make the ride terrible (by the way Chris I've been on 32/36 for a couple of months now and that is where i will stay). So you can't always go by factory!!! 19s were only approved on the 987 and as with a recommended pressure of 32/34 as I stated earlier. The 18 pressures in the 987 manual are 30/31 which is a heap different to the 986's 29/36. So thinking about it and how the two equate I would probably take the pressure in a 986 with 19s up from standard by about 2 lbs each. Makes it 31/38. Then take it out and use the testing device that comes with all Porsches.......................The seat of your pants!!!!!!! Link to comment Share on other sites More sharing options...
T-Man Posted 8December, 2012 Report Share Posted 8December, 2012 The tyre technician at Traction Tyres while fitting my new wheels, asked if I track the car. I replied never, to which he said the fronts showed a bit of fairly aggressive driving. To which I can only summise due to SMT's. he suggested putting a bit of camber on. That's all a bit out of my depth, rather not play around with that stuff so I declined. Niko, should have gone the camber mate. Link to comment Share on other sites More sharing options...
9fan Posted 9December, 2012 Report Share Posted 9December, 2012 For those who like spirited driving (I'll say track) when you have a wheel alignment ask about camber. Outside wear can occur with only normal camber and spirited driving. On the 968/944 you can get about 2.5 negative (wheel further out at base) with normal strut mounting. I use this both street/track and am happy with wear characteristics. It will give you slightly more wear on the inside with normal road driving but more even wear with spirited driving with better turn/grip, depending on how much time doing either. 911 may be different but a good Porsche/tyre guy will point you in the right direction, if your happy to carry the wear that comes with spirited driving. Enjoy the Drive ! Link to comment Share on other sites More sharing options...
Chris-p Posted 9December, 2012 Report Share Posted 9December, 2012 Will follow your advice Theo, f32/r36 it is... C Link to comment Share on other sites More sharing options...
T-Man Posted 9December, 2012 Report Share Posted 9December, 2012 Will follow your advice Theo, f32/r36 it is... C Don't forget I've got a C4 Chris. Characteristics may be a little different. I've had to work on reducing the bloody under steer. Link to comment Share on other sites More sharing options...
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