Tyre pressure questions

[paddy]

My DR250 is running Dunlop D604's. The tyre pressure plate on the swingarm states that both the front and rear tyres should be inflated to 150 kpa; however, the stated pressures are for the D605 tyre with is comparatively a knobby. Is the pressure still appropriate for the D604?

Also, as an aside, given that these are tubed tyres, what is the minimum pressure that I can run these tyres at (on sand for example) without the tyre creeping around the rim and ripping the tube?

[MXNUT]

My DR250 is running Dunlop D604's. The tyre pressure plate on the swingarm states that both the front and rear tyres should be inflated to 150 kpa; however, the stated pressures are for the D605 tyre with is comparatively a knobby. Is the pressure still appropriate for the D604?

Also, as an aside, given that these are tubed tyres, what is the minimum pressure that I can run these tyres at (on sand for example) without the tyre creeping around the rim and ripping the tube?

Hey Paddy, i run 14 - 18 psi ( Depending on the conditions ) in the tyres on the road and down to 12 psi for offroad.

Sand does not require very low tyre pressures unlike wet clay but the minimum to use off road only would be 10 psi.

Sharp gravel or rocks go for 18 psi

[Box'a'bits]

Hey Paddy, i run 14 - 18 psi ( Depending on the conditions ) in the tyres on the road and down to 12 psi for offroad.

Sand does not require very low tyre pressures unlike wet clay but the minimum to use off road only would be 10 psi.

Sharp gravel or rocks go for 18 psi

Thats assuming that you are using rim locks. If not I wouldn't really advise much below 20 PSI, or you run the risk of tyre creep, & potentially ripping a value stem.

Cheers

Steve

[bart]

I give my tyres a kick from a size 8 moto x boot. If the toe hits the rim, I start up the compressor, if not, I ride.

Rimlocks are great things.

[paddy]

Hmmm....okay. The recommended pressure of 150 kpa converts out to 22 psi which is close to what you are all suggesting. It had originally seemed low to me, but I was using road bikes as a frame of reference (most of my km/s are road km).

Your responses lead me to a couple more questions though:

1) I am understanding correctly that I will gain no benefit in soft sand from lower tyre pressures?

2) I am presuming that a rimlock stops tyre creep. I am looking a a picture of one (link below) and I can't figure out exactly what it is supposed to do. How does it hold the tyre? It looks like I would need an extra hole in my rim (could that be what the rubber plugged hole is for)?

Rimlock picture: http://www.dirtbikebitz.com/rim-lock-tyre-clamp-p-729.html

[Box'a'bits]

I give my tyres a kick from a size 8 moto x boot. If the toe hits the rim, I start up the compressor, if not, I ride.

Rimlocks are great things.

Fred was running about 6-8 PSI pre the Orongorongo ride. Thing was, he hadn't dropped pressures for the ride - that was how he arrived. :gob:

[Oscar]

Fred was running about 6-8 PSI pre the Orongorongo ride. Thing was, he hadn't dropped pressures for the ride - that was how he arrived. :gob:

Enduro pressures on WR250's and such were 12psi in the front, 10 in the rear.
If things got rough, you could always let some out (that's what rim locks are for).

[Motu]

2) I am presuming that a rimlock stops tyre creep. I am looking a a picture of one (link below) and I can't figure out exactly what it is supposed to do. How does it hold the tyre? It looks like I would need an extra hole in my rim (could that be what the rubber plugged hole is for)?


That's what it's for....you may even have 2 on the rear.Some modern rims have some sort of bead gripping provision in the rim....only on alloy.Something that will mechanically lock into the bead.I have found 15psi a good compromise - flex is good off road....and I like a lot of tyre flex on road too.

[Ocean1]

1) I am understanding correctly that I will gain no benefit in soft sand from lower tyre pressures?

Lower pressures are mostly to gain contact area in soft stuff, most sand is excellent traction so usually no advantage.

FWIW I ran my KLX400 at 12/10 psi in normal conditions, up a couple in sharp stuff, (the limiting factor is pinch-flats) and down a couple in soup.


2) I am presuming that a rimlock stops tyre creep. I am looking a a picture of one (link below) and I can't figure out exactly what it is supposed to do. How does it hold the tyre? It looks like I would need an extra hole in my rim (could that be what the rubber plugged hole is for)?

Yes they fit inside the tyre carcase and clamp it to the rim by tightening a nut on that stud against the extra hole(s) in the rim. 2 is good, better ballanced and more secure.

Also, get some heavy duty tubes, will save you a lot of sweat when you least need the excercise.

[warewolf]

I ran 11.5 front, 12.5 rear in my DR-Z250 at Woodhill (sand) with rimlocks. Anything more than that and grip was compromised. Anything below 16(?) psi without rimlocks resulted in tyres spun on the rim. Go ride your bike at various pressures, see what works for you with your bike, your tyres, and your riding conditions. 8/10 psi was not uncommon, nor was +3 psi on my figures.

Road pressures for me were 22 front 25 rear per the placard maybe a bit above; the placard is a road requirement so quote road pressures which are irrespective of the type of tyre fitted. The dr250 is not a "road bike" it weighs about half a typical big bike (not counting hypersprots bikes) and produces much less hp so doesn't need their pressures. You want roughly 4psi rise from cold to hot. If the tyre isn't warm to the touch, the pressure is too high. If the tyre is very hot, the pressure is too low.

Yes a rimlock stops (reduces!) tyre creep, and yes the plugged second hole is for the rimlock. When the nut is tightened, it clamps the tyre bead against the rim. Run the rim tape over the rim lock to help protect the tube from damage against the lock. The rimlock sits inside the tyre, ie with the tyre bead between the rimlock and the rim, like this:
http://image.dirtrider.com/f/15512036/141_0901_21_z+tech_fixing_a_flat_tire+hd_bridgesto ne_tire.jpg

22psi is not "close" to 12psi, it is more like double (despite being "closer" than say 42psi per a typical road bike). Don't worry, off-road tyre pressure is one of those things that road riders just don't "get" at first.

[Motu]

off-road tyre pressure is one of those things that road riders just don't "get" at first.

I still don't ''get'' road tyre pressures - I'm running 25/20 in the BMW,which is more than 10psi lower than recommended.But the tyres are made to run at those pressures,they work at those pressures.I still think lower pressures mean traction,I feel like the bike is going to slide out on me with 36psi.

I'm going to fit my road wheels on this weekend....I'm grumpy just thinking about the pressures I'll have to run.

[Patch]

I run lower pressures than "recommended" for my road bike, and we get down to 8-10psi when 4wding (slightly different pressures for diff terrain etc) horses for courses


Learn to experiment a little to see what suits you and the terrain you are covering.

Tyreflex is a good thing - just something else to learn and understand.

[NordieBoy]

As has been said. Find out the pressures that work for you.

On the DR650 on road the front MT21 likes 28psi and off road about 20-22psi is fine. The rear MT21 on road was fine at 30psi but off road had to be around 18psi to get any grip. The Shinko SR244 rear is happy with the same on road pressure but can handle 22-25psi off road for the same "feel" as the MT21 at 18.

I've got rimlocks but have this subconcious aversion to going below 18psi front or rear. Dunno why.



Use the recommended pressures +5psi as a startpoint and take a pressure gauge and mtb pump with you.
Ride over the rocks/gravel/whatever. Ride back. Drop 2psi. Repeat. There will be a pressure where the tyre seems to start working/feeling a lot better.

[Oscar]

I still don't ''get'' road tyre pressures - I'm running 25/20 in the BMW,which is more than 10psi lower than recommended.But the tyres are made to run at those pressures,they work at those pressures.I still think lower pressures mean traction,I feel like the bike is going to slide out on me with 36psi.

I'm going to fit my road wheels on this weekend....I'm grumpy just thinking about the pressures I'll have to run.

It has to do with extra heat generated when riding at a constant speed on the road. I learned it the hard way when I started Adv Riding. I figured that 20/18psi would be fine on my 640 running M63's or TKC80s. I got 850km out of the rear Michelin where there were a couple of long high speed road runs. The bloody thing melted.

Speaking to the Conti importer, they said that TKCs are very particular about pressures/heat. 32/36psi on the 950 will ensure that they last more than five minutes...

[cooneyr]

I agree with the can dweller. Dunlop D606 on the DR650 would disappear in 1500/2000kms when gravel and seal riding at the recommended pressures 22/20?? I found that 30ish psi would get much better life ~5000kms and there wasn't a significant, if any, loss in traction on seal and gravel. Off road is a whole different story but the point is you need to consider life vs wear vs traction for each situation. General this means higher than recommended pressures on road and much lower than recommended (with rim locks) off road.

Cheers R