Give me air!

[Mint Sauce]

Having spent some time reading through all the recent tyre thread leads me as a novice to, I imagine, ask another age old and related question.

Hybrid Misquote

"I've found on the DR650 fitted with E07 if you lower the pressure to about one bar that Mount Everest can be readily climbed and by orally sucking the pressure to minus two bar (strong rims required and more risk of rubber ingestion than the average Manchester Street working girl) black holes are possible as long as you don't lean too aggressively":dodge:

There has been quiet a lot of stuff in the tyre thread related to off road prsssures, some that seem very low. What pressures to run at off road?

The sticker on the frame of my Japper import Dakar is suggesting about only about 2lbs less front and rear for off road. What views out there?

The current tyres are run very square; lots left on the edges; normal with off road use? Maybe it is just that it was previously owned by a Tokyo urban street warrior with not much out of town use; I suspect the latter as when I took it for my first spin the mirrors blew in at anything much above 90.

What about pumps for putting pressure back in on a ride? I have plenty of MTB pumps but has anyone done a NZ version of the modified Walmart 12v air pump as on ADVrider?

[sAsLEX]

I have plenty of MTB pumps

Your keen, they take ages on little 2 inch MTB tires, you would be there a month of Sundays to get any decent pressure back in motorbike tires.

[Crisis management]

I'm not the expert on tyre pressures, my standard response is "if it's round black and not flat then it must be ok".
I will kick the tyres on a weekly basis but that's about it and if your stuck in something soft, let some air out until it works.....

After that incredibly useful blurt however, I have something of some use? I've tried finding a workable air pump and have ended up with a foot pump from Repco ($40) that will easily deal with 4x4 tyres so doesn't take too long to sort the bike out. Ok, its a bit bulky and weights about 2kg but sits in the pack with the rest of the tools and never starts any fights with the other tools.
Others use the CO2 cartridges and incredibly small and crappy pumps, me I like overkill and reliability.

It's also made in France not China!!! (I was amazed)

[far queue]

I run 25psi front, 22 psi rear, on the road and 15/13 off road. I have rimlocks. I carry an MTB pump in case I need it, but so far haven't bothered. I just leave the pressures low until I get to the 1st petrol station or home, whatever. It still handles OK on the road, but wouldn't be good for tyre wear if left low too far.

[Transalper]

The answer depends a little on tyre choice (how stiff the side wall is, is it a knob or more roady?) and bike, rider, luggage weight.
It also depends on the off road condition, is it just shingle, or rocky or muddy?
I often let the air out until i see the tire start to relax. Seems to happen about 20psi. If it's a more mud than anything track i'd go lower. I have rim locks installed now too.
on my CRF i run 10 or 11psi on average. 8 on mud, up to 12 on sharper stuff.

[Mint Sauce]

I know this is most probably a dumb question but the last two submissions mention rim locks. What are they?

[Garry.W]

I know this is most probably a dumb question but the last two submissions mention rim locks. What are they?

A rim lock is a simple device fitted inside the rim that helps keep a more aggressive tyre from slipping on the rim under hard acceleration or braking. It saves your inner tube's valve stem from being ripped off as the tyre spins on the rim. Plus, you can use much lower pressures, giving you better off-road traction. If you can change a tyre, you can fit a rimlock.

Cheers
Garry

[tri boy]

rim locks are used on rims/ tyres that need to run at low pressure.(10psi etc) they help clamp the tyre to the rim to prevent the tyre spinning and tearing the tube valve. They are identified by seeing an extra stub (like your tube valve) sticking out of the rim. It looks like a bolt thread.
Garry W types faster than me. hehe

[cooneyr]

A big barreled MTB pump works for me. For the small number of times it gets used its not worth the weight of a larger pump in IMHO. CO2 is just something to run out of when you really need it.

Rim locks are very easy to install if you have a drill. This is assuming the dakar rims aren't predrilled with little black plastic bungs in the holes (I don't think they are)? When I did the DR it cost about $25 per end for rim locks. Dirt Action Service at 33 Saxon Street stock them. You need to know the width of your rim before charging off to see them if not taking the bike. They are well worth it if you want to drop you tyre pressures below about 20-22psi when off road (well on the DR rims anyway).

Cheers R

[NordieBoy]

"I've found on the DR650 fitted with E07 if you lower the pressure to about one bar that Mount Everest can be readily climbed and by orally sucking the pressure to minus two bar (strong rims required and more risk of rubber ingestion than the average Manchester Street working girl) black holes are possible as long as you don't lean too aggressively"

That sounds about right for the E07 depending on which face of Mt Everest. You may need more of a run up for the North face though :D

I use 32psi front, 36 rear on the road (11000km from the E07 rear now) and 20psi front and rear in the gravel etc.

I'll be getting rim-locks installed at the next tyre change.
Wouldn't want to use a more aggressive off-road tyre without them.

[windboy]

A tyre dealer once told me not to put rim locks on your bike if you commute or will ride far and fast on sealed road as it will wobble/vibrate badly. I think rule of thumb is go no less than 10 psi from nominal tyre pressure and you still wouldn't need rim locks... :yes:

[NordieBoy]

If it's been balanced with the rim lock on then it'd be sweet at any speed.
It'll vibrate badly cause you're doing high speeds on the seal with knobblies on :D

All you need to do is catch a nice immovable rock with a bit of chunky tread whilst spinning up a hill and you could spin the tyre on the rim and poss rip the valve stem out.

Rim locks go with knobblies and low pressures.

[Transalper]

A tyre dealer once told me not to put rim locks on your bike if you commute or will ride far and fast on sealed road as it will wobble/vibrate badly.
Ahh yes, like Nordie says, that's why we balance them wheels. I assure you mine don't bounce or vibrate.

[far queue]

A tyre dealer once told me not to put rim locks on your bike if you commute or will ride far and fast on sealed road as it will wobble/vibrate badly. I think rule of thumb is go no less than 10 psi from nominal tyre pressure and you still wouldn't need rim locks... :yes:
Really? I wonder why mine are fine at 140kph then?
If it's been balanced with the rim lock on then it'd be sweet at any speed.Silly me, that'll be why mine are fine, it's all that lead on the other side of the wheel :innocent:
It'll vibrate badly cause you're doing high speeds on the seal with knobblies on :DI don't get that either - although ... when I first had MT21's on, the front wheel developed an up and down oscillation over about 80kph. It lasted for about the first 100km of the tyre's life then went away and never returned. The E09's have been fine since new. But the rear's getting a bit shagged now.
Rim locks go with knobblies and low pressures.What he said.

[young1]

I heard once that a good cheap way to save weight on a bike is to let a few pound of air out of the tyres, 4 pounds from each tyre equals an 8 pound saving.

Or put helium in them, go off a jump and see how far extra you float!!!

Good comments for a Saturday morning :yes:

[far queue]

Or put helium in them, go off a jump and see how far extra you float!!!Ha ha, they tried something similar on mythbusters - filled a rugby ball with Helium to see if it could be kicked further - nope!

[NordieBoy]

Ha ha, they tried something similar on mythbusters - filled a rugby ball with Helium to see if it could be kicked further - nope!

But the mass of the football was significantly reduced but the percentage on a bike would be almost insignificant.
But where races can be won by the thickness of a coat of mud, then everything helps.

[young1]

But the mass of the football was significantly reduced but the percentage on a bike would be almost insignificant.
But where races can be won by the thickness of a coat of mud, then everything helps.

All good stuff, so if I didnt "pass wind" so much on the bike and held onto it I would be lighter at the end of the ride than at the start? I suppose I would then be talking a lot of hot air!!!