[Sleepy Samoan]

I have had the stock standard 205/70/15's on my Jimny since i first bought it and have noticed the tyre plate to keep the pressure at 23-28... I notcied this to be very low and handled odd so i kept all my tyres at 30psi with no trouble.

The problem i have now is i have now put 215/75/15r Wide Conquerer Nankangs on it (amazing btw for cheaper tyres) and find at the set psi of 28 even 30 is just making the tyre sag soo much... is this pressure correct? Can anybody fill me in on what they have tried/what works well for them... I mainly use it for city and highway driving with the odd offroad fun

So ultimately the big question is and im sure a lot of others out there are wondering as 215/75/15r is a common upgrade:

WHAT PRESSURE SHOULD I KEEP WITH THE UPGRADED TYRES?

Around Town/Highway?
Sand?
4WD?

ALSO WHAT IS BEST FOR WEAR AND FUEL ECO?

I have a 2009 Suzuki Sierra Jimny
2"inch lift
215/75/15r Nankang Wide Conquerers (Original Alloy upgarded rims)

If any of that helps

[Fatzook]

the 215's are a little wider, so they will appear to be low on pressure. They aren't. 30 should be fine for a jimny.

[Sleepy Samoan]

Fatzook they are also a Light Truck tyre does that play a roll in the pressure?

Also i find 34 to be a higher more powerful/pick upy dribe so would 34 be overkill and would it affect my tread wear much?

[Fatzook]

Sleepy Samoan wrote:

Fatzook they are also a Light Truck tyre does that play a roll in the pressure?

Also i find 34 to be a higher more powerful/pick upy dribe so would 34 be overkill and would it affect my tread wear much?

not at all. 34 will not do any harm to the tyres.

[alien]

whaaaaa? the stock tyre placard says 20psi front and rear from memory.... going to a larger tyre usually means a stiffer sidewall, so running at least the same pressure is a good idea, although the extra height of the sidewall will give more lateral instability on corners etc so you dont want to go too low.

theres a general guide called the "4psi rule", read this: http://www.aawen4x4.com.au/index.php?op ... t&Itemid=7

previous to that you can do a rolling test on your driveway, roll over some talcum powder and see how much of your tread is contacting the ground front and rear, there should be a slight portion of the tread not touching (on my 31's i calculate this at about 15mm each side of the tread face). This tread does get used on cornering as the sidewalls flex.

i run 2 different sets of tyres, and both use different pressures (one has softer sidewalls than the other). On one set i run 26psi front, 22 rear, and on the others with the softer walls i run 27psi front and 23 rear... sounds like 1psi is bugger all, but it makes a noticeable difference to handling, specifically tight fast turns on back streets (if you do that kinda thing). I check my tyre pressures fortnightly (i usually go wheeling enough that checking means airing down for a play then airing back up at the end)... If i air up on a particularly cold afternoon, the following day the pressure can be significantly higher and vice versa - i've seen a change once when i aired up in 39 degree weather, and the next morning was 18 degrees and my front tyres looked flat - when i checked they were at 20psi rather than the 26 they started at!

So what im saying is, learn what pressure to run your tyres at, don't just assume you're doing it right.

[SierraDan]

25-30psi is a decent pressure.

[alien]

30psi in mine = zero grip on wet roads both front and rear... it understeers then goes into oversteer and tries to kill me. 40psi in my cooper STT's (now on moph's zuk) got me through the lane change test though =) all be it with oversteer on the last turn at 100km/hr.

[SierraDan]

What tyres?
The only time tyre pressure has made it sketchy for me is below 10psi.. On corners doing over 40kph.

[alien]

BFG KM2 and Kumho KL71... i've also run 31" Simex ET and Cooper STT... all of them were useless at higher pressures on wet roads... although interestingly the simex performed the best on wet roads till they got down to 50% tread (which happened fast). I had to run the simex's at 22front and 20 rear in summer, and 20front 18rear in winter though, otherwise they were scary.

[SierraDan]

Hmm, I'll stay away from those tyres then.

[zukmeista]

Fatzook wrote:

Sleepy Samoan wrote:

Fatzook they are also a Light Truck tyre does that play a roll in the pressure?

Also i find 34 to be a higher more powerful/pick upy dribe so would 34 be overkill and would it affect my tread wear much?

not at all. 34 will not do any harm to the tyres.

Apart from wearing out the center of the tyre

[brindog]

I usually ran 26 in my 215 KM2's. Got pretty even wear. Rotating every 5000.
Off road I usually dropped them to 15>

[royce]

Its pretty safe to assume a bunch of Suzuki engineers know a bit more about this sort of thing than some spankers on the internet

go with the placard, too high a pressure will effect wet weather braking, hate to see you kill somebody

[zooky08]

I ran 22-24 with my 215s km2 had no problem. I'm now running 26-28 in my 30 km2s.
I'm with royce, for 215s I would stay with the placard pressures.

[royce]

zooky08 wrote:

I ran 22-24 with my 215s km2 had no problem. I'm now running 26-28 in my 30 km2s.
I'm with royce, for 215s I would stay with the placard pressures.

Yet with tyres that are even higher load rated and likely need less pressure to work you have more in them

[zooky08]

royce wrote:

zooky08 wrote:

I ran 22-24 with my 215s km2 had no problem. I'm now running 26-28 in my 30 km2s.
I'm with royce, for 215s I would stay with the placard pressures.

Yet with tyres that are even higher load rated and likely need less pressure to work you have more in them

Both sets?

[just_cruizin]

Hey Alien, there is no way your tyres lost that much pressure due to temperature alone. Google Combined Gas Law

[alien]

i googled it and got some crazy algebra.... there's no way im gonna sit down and learn that =) lol

when i aired up on that hot day though, it was after doing high speed driving at low pressure on gravel, so the tyres were pre-warmed as well as the added heat of the day (dont forget that 39 = in the shade, and i was out in the sun). The beads definitely werent leaking, that was the first thing i checked - and i used the same pressure gauge so theres no variable there.

[just_cruizin]

Pretty much
P1V1/T1 = P2V2/T2

Your volume is pretty much fixed, tyre isn't going to change in volume, therefore it's only pressure/temperature ( temp is measured in Kelvin so add 273 to celsius and pressure is absolute so add atmospheric say 100kPa (14.7psi)

You would have lost half of what you quoted, 23psi would be reasonable, if you say 1 psi is noticeable with your tyres it will certainly feel a difference.

Personally I don't feel that with Sierra suspension it makes too much difference. I could set up a chill unit on my drivers spring to correct the lean.

[squibby]

OMG don't start another tyre pressure argument. I think it's pretty universally agreed that going above 30 on a Jimny is bad. Experiment with 20 - 30 psi and make your own mind up, because it's hard to get an agreement from us jimny owners. I have 215's and I go about 26 PSI in the front, and a bit less in the rear. Anything above and Jimny skips around because it's too light for higher pressure on chunky Heavy duty all terrains.

Garages automatically stick too much air in the jimny, they over stimate it's weight. It a very light weight car. I even carried an engine from one on my own.

[SierraDan]

They just go "tyre - put 38psi in it". They dont assess its weight haha.

[zukenutter]

For the sake of the thread I'll add my 2 cents worth;
I'm with Royce on the tyre placard comment. Tyres are supposed to belly at the bottom so don't gauge it by that.
The talk idea is similar to my technique where I draw a chalk line across the tread then run it up the driveway a couple of times, then check where it rubbed off. If the outer edges rub off but the centre of the tread still has chalk there's not enough pressure. If it rubs off the centre the pressure's too high. I aim to have it rub off evenly with just the edges of the tread still showing chalk. Using this method I've found the stock tyres fell into Suzuki placard guidelines, while larger tyres with heavier sideways tended to need less pressure.

Not long ago I had a set of 30x9.5R15 BFG KM2s fitted and I decided to try them at 30psi for a while. I don't think it took more than a couple of days for me to decide to drop back to a softer pressure.

With high pressure in the wet, as others have already said, you'll end up against a tree or up the back end of another car due to a lack of traction. The other good reason to keep the pressure lower is that with high pressure you'll feel every bump in the road. It may feel like it handles a bit odd having them softer but remember it is a 4WD.