Rim locks or not?

[spakur]

Hi folks

I have been surfing the net for a couple of days reading about rim locks and can't decide if I need rim locks or not.

I have recently bought a KTM 640 Adv 2004 that isn't predrilled for rim locks. My previous "Adventure" bike was a F650. I didn't use rim locks on that one and that was never a problem when riding with low pressure off road.

However the F650 doesn't have the same power/torque as the KTM...Looking also at the tires today I also see that the tubes have moved a bit...

So should I put on rim locks front and rear? If I do so I have read that two in front and two at the read is preferred for the balancing.

I have only 3 weeks until i leave for Mongolia, so would reallly appreciate some quick answers :-)

/spakur

[Island Hopper]

I've logged 70,000 km on my 640 and never had the bead slip to cause a flat..... But I always run 26-30 psi in both tires and have gotten use to the way the bike handles in varied terrain with that pressure..... Also I leave the nut off the valve stem and instead slip a small length of rubber hose down the stem to the rim so if it does move a bit it wont rip the stem out....

If you plan on running in the low 20s psi I would recommend running rimlocks for sure.....

[Dessertstrom]

I had rim locks on my motocrossers rear wheels but not the front. It depends on how much hammer you are going to give the bike and how much pressure in the tyres, it only takes one mud hole and a hand full of revs to turn the tyre on rim.
The fact that there is no hole for a rim lock suggests that you don't need them on your bike, some tyres fit very tight.
Cheers
Ian

[backofbeyond]

If you do fit rimlocks pay careful attention to wheel balance. Each rimlock weighs over 110gms and unbalanced thats a fair bit of vibration. It gets worse though! If you've got the usual 21" front and 18" rear the wheels rotate at different speeds so the vibration from the individual wheels goes in and out of phase.

You only start to notice it above about 55 -60mph but it gets worse rapidly as you speed up. It feels like a severe shake followed by a period of smooth running repeating over 4-5 seconds.

When they multiply the vibrations get very intense and 10 miles at 75mph was enough to snap the exhaust mount on my CCM (and give me double vision). You don't have to get the balance perfect - to the nearest 20gms was good enough to fix it to the point where I can't feel it any more.

[spakur]

Hi

On my previous bike I used to run the tires at about 20 psi (offroad) if I remember correctly and with no problems at all, but I ain't so sure if this will work for the KTM.

I am glad however to hear that there's no problem if I run them a little bit higher.

On my Husberg enduro bike I have rim locks both rear and front, but then I also run them at 15 psi or so...

[spakur]

I gave the wheels to a mc tire shop today and they said that if I run the pressure above 1.0 bar witch is about 15 psi I should be fine without rim locks...so I gave up the idea about rim locks...We'll see if it was the right decision or not when I'm in mongolia :-)

Thanks for the feedback!

[Island Hopper]

If you run 15-20 psi in your tires without rimlocks chances are the bead will slip.... I would not run that low of pressure without locks, not worth the risk, especially when you are miles from nowhere.....

[spakur]

Well that just makes life more interesting :-)

In worst case I have spare tubes with me...

[rossphoto]

I just rode my 07 640 ADV to Guat and back to Kentucky. I was pretty loaded in the back and running about 27 PSI... I had a stem rip out doing about 70 mph on a busy hwy in Mexico... I was amazingly lucky that I kept the bike up... After that I changed the tubes ran about 35 psi the rest of the trip and didnt have anymore probs... I did loosen the little screw lock all the way up the stem to the plastic cap to allow for some stretch I did notice a bit of bead slippage even at high pressures but not enough to tear it. However, I was paranoid the whole time. I am planning a RTW soon and will use rim locks. Also as mentioned above if you do use them check the balance....

Good luck on your trip

[Matt Roach]

Seems a source of great debate.....

I regularly run pressures of between 15-20 psi offroad on a 640 Adv with Mich deserts + heavy duty tubes without rim locks and have never had a stem rip or the tube move significantly. I have also run pressures as low as 8 psi on sand, again without problems.

As pointed out earlier the stem can move a bit, so best not to tighten the locking nut.

The quality of the tube will also make a difference to how likely the stem will be to rip or the tube to move.

[spakur]

Thanks for joining the debate!

Interesting to see that some people have no problems while others do.

I'll keep an eye on my tires on the trip...

[Dessertstrom]

I think it depends on the bike/wheel design and how tight a tyre fits to the rim and if a bigger or smaller tyre has been retro fitted which may account for the differing experiences.
After many bikes I have opted for a bike with tubeless tyres. (don't start)
Cheers
Ian

[tifua]

9 mths across africa with 2 ktm's we got 2 punctures in the whole trip (which is pretty lucky admittedly) ... both on the front wheel, once in soft sand running low pressure and once on badly pot holde & rutted track, when the tyre rotated on the rim and tore the valve. This was the only wheel without rim locks and once i put the rimlock in no more punctures.

[KiwiBruce]

I think Issac Newton, or one of his buddies, fiqured it out some time ago, it's something to do with teh effect water as on friction. . . .

I have run dirt bikes with and with out rim locks and I thought that running without them was fine until I rode through a stream one day and some water got between the tire and the rim. As rode out of the stream I thought my clutch had failed as when I opened the throttle, even very gently, the motor would rev but I wasn't getting any forward motion, a quick check confirmed the clutch was fine but the rear tire was flat and the valve stem was no where in sight.
Moral of the story:
High pressues and dry conditions = no problem
Medium pressures and dry conditions = should be OK but could be risky
Low pressures and wet conditions = puncture repair time

[clintnz]

When I put the full knobs on my 640 for trail riding I set the pressures to 18psi, never had a problem, wet or dry, no rim locks. If I had a need to go lower I'd probably fit some.

Cheers
Clint