jiberjaber Posted May 30, 2006 Report Share Posted May 30, 2006 Following on from the topic about underinflated tyre pressures, what's the recommended pressure for the std 17" Bridgestones on an IS300, in the following situations: a) mostly fast motorway driving? a bit of "Nurburgring action" ? Ta Quote Link to comment Share on other sites More sharing options...
Tony Posted May 31, 2006 Report Share Posted May 31, 2006 Following on from the topic about underinflated tyre pressures, what's the recommended pressure for the std 17" Bridgestones on an IS300, in the following situations: a) mostly fast motorway driving? a bit of "Nurburgring action" ? Ta IS300 stock is 33psi, revised by wim for the IS200/300 to 35psi last year... The Motorway psi should be suggested in the owners manual, this i would consider accurate. As for the ring it depends on the tyre grading One thing i would need to know is the sidewall Traction/Temperature grades... this will indicate how fast the tyre will come up to temperature.... Then its down to the drivers feedback. Pressure manipulation develops the 'slip-angle' this is the amount of flex at the tyre sidewall... more pressure less flex (over-steer front) or (under-steer rear) finding the balance is the trick! For the record the tyre grading is marked on the side-wall, also tyre wear for the track days and Domestic tyre wear are different by request. Quote Link to comment Share on other sites More sharing options...
Jap Devil Posted June 1, 2006 Report Share Posted June 1, 2006 I'm running 18" Bridgestone Potenza SO3's at 36psi F/R for normal driving, reduced to 32psi rear and 34psi front for 1/4 miles & track Quote Link to comment Share on other sites More sharing options...
jon Posted June 1, 2006 Report Share Posted June 1, 2006 You need a tyre temperature guage really, that way you can take readings inside, middle and outside and can work out if your pressures and cambers are accurate for the driving you're doing. Than again that is getting a bit anal... Quote Link to comment Share on other sites More sharing options...
Tony Posted June 2, 2006 Report Share Posted June 2, 2006 You need a tyre temperature guage really, that way you can take readings inside, middle and outside and can work out if your pressures and cambers are accurate for the driving you're doing. Than again that is getting a bit anal... Interesting.... never used a temp gauge... Although i have been asked about them..... Most recently as a method to access track day tyre pressure, in truth i couldn't fully answer the owners questions.... This is why? The car is a very heavy RWD running 245mm front tyres..... -1 deg 30' front camber, +6 deg Castor and +20' total toe..... His question was how to ascertain the best tyre pressure by measuring tyre temp for track days. Remember if the pressure is to high the car will over-steer, to low under-steer both via the tyres slip angle, additional consideration is the pressure would influence rolling resistance adding of subtracting the toe position dynamically...... oh and also the car is fully fitted with Poly-bushes..... Taking all this into consideration i personally can see Little benefit measuring tyre temperature since the conclusion opens to many variables. Let me add another.... For testing surely the track would need equal left/right bends with equal radii, if not then the results could only be concluded from one tyre.... but which one?..... Logic suggests the only way to test the tyre temperature is on a 1/4 mile done a few times.... Quote Link to comment Share on other sites More sharing options...
jon Posted June 2, 2006 Report Share Posted June 2, 2006 Tony, the 'correct' pressure, which is tied in with camber, changes from event to event so there is no golden rule on X pressure with X camber will work best. The method of finding out is do a run on your INTENDED application (whether it be down the strip or 5 hard laps around Brands, come in and quickly measure inside, center and outside temps. You can then work things out from this basic matrix (OS tyre readings, left to right): 100 120 100 - pressure high, camber ok 120 110 100 - pressure ok, negative camber 100 110 120 - pressure ok, positive camber 100 100 120 - pressure low, positive camber Quote Link to comment Share on other sites More sharing options...
Tony Posted June 2, 2006 Report Share Posted June 2, 2006 Tony, the 'correct' pressure, which is tied in with camber, changes from event to event so there is no golden rule on X pressure with X camber will work best. The method of finding out is do a run on your INTENDED application (whether it be down the strip or 5 hard laps around Brands, come in and quickly measure inside, center and outside temps. You can then work things out from this basic matrix (OS tyre readings, left to right): 100 120 100 - pressure high, camber ok 120 110 100 - pressure ok, negative camber 100 110 120 - pressure ok, positive camber 100 100 120 - pressure low, positive camber That works well for me, it displays logic..... Now add +20' of front toe, say to the negative camber readings only, to keep things simple. Quote Link to comment Share on other sites More sharing options...
jon Posted June 2, 2006 Report Share Posted June 2, 2006 That's where my understanding starts to run out but i'd assume as toe is just a little slip angle in either direction it's just going to add heat across the range of numbers. Quote Link to comment Share on other sites More sharing options...
Tony Posted June 2, 2006 Report Share Posted June 2, 2006 That's where my understanding starts to run out but i'd assume as toe is just a little slip angle in either direction it's just going to add heat across the range of numbers. Indeed...... Toe is lateral and would act like a pencil rubber dismissing all the camber calculations... If we could guarantee a zero toe % during the camber/castor curve then the tyre temperature scale could be an asset, even though only for that one particular modified car..... In truth if the likes of F1-Nascar-Indy car with the millions of pounds invested can lose a race because of half a PSI, what real chance have we got trying to develop an edge by measuring tyre temperature.... I feel an intelligent educated guess and driver feedback owns the plinth. Quote Link to comment Share on other sites More sharing options...
jon Posted June 2, 2006 Report Share Posted June 2, 2006 We're not in an industry were half a PSI makes or breaks the result, we can however garnish a lot of useful setup information with tyre temperatures. I don't understand why the toe would ruin the camber calculations, the hottest areas would just get hotter, you can still get data... Quote Link to comment Share on other sites More sharing options...
Tony Posted June 2, 2006 Report Share Posted June 2, 2006 We're not in an industry were half a PSI makes or breaks the result, we can however garnish a lot of useful setup information with tyre temperatures. I don't understand why the toe would ruin the camber calculations, the hottest areas would just get hotter, you can still get data... Example: RWD with negative front camber (compressive force negative) should also have positive front toe since the front wheels are being pushed+rolling resistance, unless you can gauntee the toe position will conclude a 0 position then the overall camber/temperature readings must then be fictitious... Lateral scrub generates much more heat than camber compression since the lateral scrub involves the entire tread, it is true to say the temperature differential will display a disparity but in reality if you are honest the results are hardly conclusive considering the variables. Quote Link to comment Share on other sites More sharing options...
jon Posted June 2, 2006 Report Share Posted June 2, 2006 I think you need to come to a trackday, i'll bring the pyrometer and we'll have an educated play with toe, camber and pressure. Quote Link to comment Share on other sites More sharing options...
Tony Posted June 3, 2006 Report Share Posted June 3, 2006 I think you need to come to a trackday, i'll bring the pyrometer and we'll have an educated play with toe, camber and pressure. What I'm about to type will make you sit back and think 'Twat' or I 'Understand' A track day would involve every possible example for exploration but only conclude that one example!.... As fascinating as it would be the results would not. could not be considered matter of fact... Only an example! Exploration needs to be Global retaining argument exploring the overall topic. Quote Link to comment Share on other sites More sharing options...
jon Posted June 3, 2006 Report Share Posted June 3, 2006 Theory can only take us so far, at some point you're going to have to go to the track and find out exactly what happens. We can sit here and discuss every possible logical outcome until we're blue in the face and i'm an old man however as i'm sure we've all experienced, 'paper work' often goes out of the window when you actually get to the track and try and work things out for real. My point was, we now know what should be warm and why, the next step is to surely do it in real life. I know I will next time i've enough tools at the track. Quote Link to comment Share on other sites More sharing options...
Tony Posted June 4, 2006 Report Share Posted June 4, 2006 Theory can only take us so far, at some point you're going to have to go to the track and find out exactly what happens. We can sit here and discuss every possible logical outcome until we're blue in the face and i'm an old man however as i'm sure we've all experienced, 'paper work' often goes out of the window when you actually get to the track and try and work things out for real. My point was, we now know what should be warm and why, the next step is to surely do it in real life. I know I will next time i've enough tools at the track. Fair comment!..... Your data would indeed compliment theory. Quote Link to comment Share on other sites More sharing options...
Yaumeister Posted March 21, 2007 Report Share Posted March 21, 2007 IS300 stock is 33psi, revised by wim for the IS200/300 to 35psi last year... The Motorway psi should be suggested in the owners manual, this i would consider accurate. As for the ring it depends on the tyre grading :rolleyes_anim: One thing i would need to know is the sidewall Traction/Temperature grades... this will indicate how fast the tyre will come up to temperature.... Then its down to the drivers feedback. Pressure manipulation develops the 'slip-angle' this is the amount of flex at the tyre sidewall... more pressure less flex (over-steer front) or (under-steer rear) finding the balance is the trick! For the record the tyre grading is marked on the side-wall, also tyre wear for the track days and Domestic tyre wear are different by request. My apologies for digging up an old thread, but may I enquire if the 35psi recommendation is still valid instead of 33psi for "normal day-to-day" driving? Quote Link to comment Share on other sites More sharing options...
Tony Posted March 21, 2007 Report Share Posted March 21, 2007 IS300 stock is 33psi, revised by wim for the IS200/300 to 35psi last year... The Motorway psi should be suggested in the owners manual, this i would consider accurate. As for the ring it depends on the tyre grading One thing i would need to know is the sidewall Traction/Temperature grades... this will indicate how fast the tyre will come up to temperature.... Then its down to the drivers feedback. Pressure manipulation develops the 'slip-angle' this is the amount of flex at the tyre sidewall... more pressure less flex (over-steer front) or (under-steer rear) finding the balance is the trick! For the record the tyre grading is marked on the side-wall, also tyre wear for the track days and Domestic tyre wear are different by request. My apologies for digging up an old thread, but may I enquire if the 35psi recommendation is still valid instead of 33psi for "normal day-to-day" driving? To date 35psi is working just fine so still advised. You need to apply (Lexus) pressure corrections for high speed driving and loaded driving. Quote Link to comment Share on other sites More sharing options...
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