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Recommended Tire Pressures

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I understand if I get a stock answer, but thought I'd ask in case some one is willing to share their thoughts on tire pressures.On all my previous vehicles (cars and motorcycles) I've run tire pressures at, or closer to the tire manufacturers maximum. Reasons for fuel economy, tire wear, safety, etc.)On my past vehicles though, the recommended of the vehicle manufacturer were always quite close with those of the tire manufacturer. I notice though on my Smart that there is quite a large difference between Smart and the tire manufacturer (29vs44 front and 36vs44 rear respectively) so I'm hesitant to inflate them closer to the tire manufacturer's max (maybe Smart knows something I don't and I'd inadvertently cause bad things ;-)Any thoughts or experience with this?ThanksJacqui

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Check the enviro-mileage forum... we have covered this topic extensively. I would not run 44 in the winter for regular driving. But 38 rear 33/front is probably not a bad idea. In the summer, if you are inclined, up to 44 PSI will yield some fantastic fuel economy at low speeds (80-90 kmh).Moving this topic to enviro-mileage.Cheers.

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The higher pressure will make the ride harsher and on a smart you will notice the difference.

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Thanks. I must not be very effective with my forum searches b/c I've been searching and not finding much of anything other than a few posts about TPMS's. I'll try again...

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Check the enviro-mileage forum... we have covered this topic extensively. I would not run 44 in the winter for regular driving. But 38 rear 33/front is probably not a bad idea. In the summer, if you are inclined, up to 44 PSI will yield some fantastic fuel economy at low speeds (80-90 kmh).Moving this topic to enviro-mileage.Cheers.

Would you suggest maintaining a similar front/rear ratio for whatever pressures I run? Would that difference be b/c of the different tire sizes?

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Most everyone I know runs a lower front pressure..... 2-3 PSIThat is 451 specific OEM wise, but cdi owenrs are typically running 33/31 or 35/31, somewhere like that, as a normal pressuretry 38/33 and see how you like it, if it's harsh, go 36/33I generally run 2-3 PSI lower, even when hypermiling at 44 PSISometime just scrolling through the list of topics in enviro-mileage will yield some interesting topics for your perusal

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Would that difference be b/c of the different tire sizes?

Max tire pressure(value on tire) is set to give maximum weight loading on the tire. Max weight handling Kumho front 827 lbs/ea, rear 908 lbs/ea @ 44psi. The car manufacturer sets the specs to give a set ride, handling, FE, etc.On SCOA some owners are setting the front pressure at 32psi with their winter tires and are reporting better handling. I am currently running stock 451 pressures in my 145 winters(front and back) but that may be set a little soft. I am going to try bumping the fronts up to 32psi, maybe then try 38psi in the rears.

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Specified tyre pressures for 450 models do not seem to add up:2002 or earlier petrol.Front wheels (145/65 R15) 1,6 barRear wheels (175/55 R15) 2,5 bar2002 or earlier Cdi.Front wheels (135/70 R15) 2,0 barRear wheels (175/55 R15) 2,5 bar2003 and later petrol and Cdi.135/70 R15 front & 175/55 R15 rear 2.0 bar145/65 R15 front & 175/55 R15 rear 2.0 bar175/55 R15 front & 195/55 R15 rear 2.0 barI understand the 0.4 bar difference in tyre pressure for front wheels for 2002 and earlier Smarts. This is obviously due to different tyre width and profile, but makes no sense when examining tyre pressures for 2003 and later.Can someone please shed light on the vast difference in tyre pressures. A 0.4/ 0.5 bar change is quite significant. Axle weights are practically the same for all 450 Smarts so that is not the reason. I wonder whether the 2.0 bar specified for rear wheels is Smart sales dpt's attempt of improving ride comfort at the expense of optimum tyre wear and safety?Any thoughts?

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Those low figures remind me of the 1960s recommended pressure for my 404: 1.35 bar front (!) well I always ran it at 2.I wonder whether the low low F pressure was at first put in place because of the transverse front roadspring?

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Just to bring forth my two cents...Running lower pressure in the front tires doesn't make all that much sense. The amount of pressure you need to run is directly proportional to the area of the contact patch the tire will be contacting the pavement. Of course the size of that contact patch will change with the pressure, so this is something to keep in mind. When racing bikes we always run the rear tire 4-5 psi less than the front, and that isn't because there is more weight on the front. It is due to the fact the rear tire is massive, so less pressure will still equate to the same force pushing down against the ground when the vehicle is sitting stationary. Even though the smart does have some weight on the back (I don't actually know it's true weight distribution) it doesn't need more pressure in the back to compensate. The rear tires are so much wider that the extra area alone will more than compensate with pressures being the same front and rear, if anything I think the rears on this car should be a tad less.We would adjust pressure on the bikes to change what temperature the tire gets to. If it is getting too hot, we bump up the pressure, and if it isn't getting hot enough, we bring it down. No doubt bringing up the pressure on the Fortwo will greatly improve mileage (It has on mine!) but the reaason for that is less friction, thus less traction and so when hard cornering enters the equation, the better mileage setup isn't the best corner carving setup. I know I said I was going to get rid of my smart a while back, but me and my little buddy have become pretty good pals... I was getting slaughtered off the line today by a big truck and this girl in a civic, until it came time to get on the brakes for the long right hander that was approaching. I basically just keep my foot on the throttle, took the corner at about twice the speed they did and proceeded to do the same in the following increasing radius right hander, only just a little low pitched squeal from the tires and a big smile on my face was all that was left. I'm finding the worst part is the ECU preventing me from accelerating when doing really hard cornering... it must think it needs to intervene else I will perish.Now I just have to keep resisting putting one of my ZX-10R race engines in this thing... Oh the joy of having power with such lightweight nimble fun!

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Yeah the ESP is even more interventionist in operation when you have wider tires like me....

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If you want to see interventionist ESP, trying running 40 PSI on well worn tires on the Oregon Coast......woo hoo......

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