[andrew]

Hi guys i just got some kumho kl71 215 75 15
And was woundering what tyre pressure to run

[sideways]

Most people on here run between 20 and 25psi.

It's a can of worms subject.

[andrew]

Ive never owned a 4x4 before. I was just looking for a rough guide line i read somewhere that in sand you deflate the tyres or something

[andrew]

I just didnt want to wreck my new tyres by being too under pressure

[pezz]

Run them on road as per the factory spec's (suzuki,not the tyre) from memory its 22psi
6-10psi offroad

[bumstein]

^ about spot on.. I run 20psi on the road, more than that and I definitely see signs of overinflation when the tyres start to wear.

[Mike57]

And just about every tyre place will tell you to run 40 PSI and I have given up arguing with any of them.

As said already run the placard pressures on road (the ones suggested for the standard tyres). Off road I use 18 PSI for corrugated roads with a load and say 80 kph then 12 to 14 psi for rocky terrain in low range and down as low as 8 psi for soft sand but try 10 psi first. Just remember to not drive fast of make any hard cornering moves with low pressures in the tyres. Exception is 18 psi but even then keep it down to about 80 to 90 kph depending upon how loaded you are. I also have 215/75/15 but a heavier vehicle.

Hope this helps.

[Reubs]

20-24 on road. Definitely no higher than 24 is required - ever.

10-18 off-road. Lower than 10 there is a good risk of getting sand and mud stuck in the beads which will lead to slow leaks. Definitely no lower than 6 on such small tyres. 31"+ is a very different story.

On sand you should never need less than about 16. Heavier vehicles are a different story also lol!

[vet 180]

Jimny, but similar.

I run 26psi on road a little higher than the placard because a lot of highway driving.

10-12psi offroad.

[vet 180]

Reubs wrote:

.

On sand you should never need less than about 16. Heavier vehicles are a different story also lol!

I always need less than 16. Anything over 14psi and it struggles in deep sand. I guess for beach runs 16 would be fine. Granted it is a jim.

[andrew]

Ok so ill go 20 as that seems like a good adverage on and off road.
Why do tyre shops tell you 40 ???

[Gwagensteve]

Because they have lost the ability to think.

I was at a wine tasting dinner I regularly last year and somehow this came up. The host, who has worked his whole life in the wine industry, and knows nothing about cars, chimed in with "my first job was at a servo at 16 as a pump attendant. We were taught to find the tyre placard before pumping up the tyres"

Apparently tyre fitters are unable to do this now.

[andrew]

I can see the placard thing sure. But surely in the event of people running soo many different sized tyres and rim combos and even the tyre its self. This would change the pressure rating....hmmm ill ask my brother hes an engineer at ford. Someone there will know 100 percent what the go is... ill get back to you soon

[Gwagensteve]

An engineer will lead you up the garden path over this, because the load ratings on there LT tyres we run on Sierra's are all miles higher than required by the GVM of the car- basically, no engineer would specify such a large or heavy tyre on such a light vehicle.

The compromise is such: a light car requires low pressure to achieve adequate traction. However, we then fit heavy tyres with high rolling resistance at low pressure, so then we pump them up too hard to get the rolling resistance down (therefore reducing the traction we gained by fitting the larger/heavier tyres in the first place.

Most cars would drive better with their replacement under placarded pressure, as they are stiffer in construction, but the owners don't like the high rolling resistance of their heavy, knobbly tyres at lower pressure.

My own car drives better with 17 in the tyres than 20 on road (35 13.5 on a circa 1200-1300 Sierra) offroad I run 5psi under all circumstances.

[Gwagensteve]

Google the 4psi rule for how to set tyre pressure from scratch. People usually aren't willing to accept it though, as it will set the pressures quite low on a Sierra, at which point the rolling resistance issue raises its head again.

[andrew]

Wow ...there is alot to this.

[bumstein]

4psi rule is a good one Steve!! Haven't heard of that before

I'm running 215 R15 100T's, on one of my sierras and 20 is spot on.. Tyres wear properly and it's not too harsh on the bumps. Rolling resistance is noticeable but not so much that it bothers me. I will the tank a few k's earlier but not so much as to cause a dramatic fuel cost difference..

One of my others I run about 15psi on 31's.. No good reason for it other than the car goes on and off road regularly and its a good blend between highway and beach without adjusting the pressures..

[Gwagensteve]

15psi is fine on road if you can live with the rolling resistance.
15psi is miles too much offroad for a Sierra in my opinion. Time for a compressor.

[greenzook89]

20-22 onroad, 8-10 offroad on 235s.

Offroad its all about getting the tyre to conform over the obstacles, look at moto trials bikes, they run 4 psi in their rear tyres to get maximum traction on terrain

[bumstein]

It's just a 'one size fits all' for my local beach.. Less than ideal for usual beach driving, but it suits the car and circumstances when I might be on the beach for 100-200 metres to surf spot and back, or a few k's up the beach for the dogs to run in the dunes.. No point airing down for it, I know the beach well and it's not struggling.. It's on and off the beach every day.

Agreed, for your average beach adventure that's too much pressure.

[vet 180]

Gwagensteve wrote:

My own car drives better with 17 in the tyres than 20 on road (35 13.5 on a circa 1200-1300 Sierra) offroad I run 5psi under all circumstances.

Do you run bead lockers?

[Gwagensteve]

Yes. I couldn't be without them- I've run beadlocks for 15 years. In my opinion Sierra's need them as much as any car because we have to run so little air to make the (always too stiff) tyres work.

[Reubs]

I'm surprised Steve still has 5PSI in the tyres under all offroad conditions if he has beadlocked 35s. I would have expected an occasional 0-2.

[1DYX]

And just to mix it up a little: I run 22 in the rears and 18 in the fronts.
Determined this using 2 different methods, when tyres were brand new...
Talc patching, and 4 psi rule, during a run to Gero.

[alien]

with 31s i run 26 front 22 rear - lower and i don't like how it corners at speed, and i like cornering at speed =)

[Gwagensteve]

Reubs- I'm not sure how familiar you are with Krawlers, or 35's on a Sierra, but I don't lack traction at 5 psi and going lower dramatically erodes directional stabilty- the car won't go where it's pointed because the rims can move so far inside the tyres. It's particularly bad on side angles, exacerbated by the spooled rear.

Krawlers have very very flexible sidewalls though.

I agree that with swampers that have only ever been on a Sierra, we found 2.5 psi front 1.5psi rear to work very well, but the same tyres which had been broken in on a heavy car didn't need to go as low to get the tyre to work.

[vet 180]

Gwagensteve wrote:

Yes. I couldn't be without them- I've run beadlocks for 15 years. In my opinion Sierra's need them as much as any car because we have to run so little air to make the (always too stiff) tyres work.

Cheers. yeah finding low load range tyres can be difficult

[Reubs]

Thanks for the insight Steve. Krawlers are a tyre I have never driven on or had in the group.

For example in the Tough Tracks series with a heavy Sierra we run about 2 psi front and very little air rear with 32" (measuring 33.3") Centipedes with staun/second air bead locks. 5PSI has noticeably less traction. I am confident other competitors are doing the same also on 33" tyred Suzuki's.

[henno]

I am pretty certain tanshi runs (effectively) zero psi in his 33x10.5 KM2s under Ring Ding. I plan to run very close to no psi in my 35" creepies, too. They came off a heavy-ass patrol, so I am hoping they have been broken in to some degree.

[pete_79]

henno wrote:

I am pretty certain tanshi runs (effectively) zero psi in his 33x10.5 KM2s under Ring Ding. I plan to run very close to no psi in my 35" creepies, too. They came off a heavy-ass patrol, so I am hoping they have been broken in to some degree.

I notice the pic of those wheels loaded in the trailer and now this.

Have you hacked into the GV or is there something your not telling us mate????



I've been waiting for a new build thread to pop up, but nothing yet......