tubeless or not

dougi · Post by **dougi** » 18 Apr 2009 14:32

i have 1978 3-1/2 sport with cast wheels the wheels are marked 12/76 i think that means they were cast in DEC 1976

the wheels are fitted with tubed tyres and inner tubes. when i replace the tyres can i fit tubeless tyres without innertubes

3potjohn · Post by **3potjohn** » 18 Apr 2009 17:25

I have cast wheel and inner tubes.Bloke at the tyre shop said you are dealing with 20 odd year old alloy so don't expect a good seal. Thats all I know.

moriniuk · Post by **moriniuk** » 18 Apr 2009 19:03

The original rims are not suitable for use without tubes.

It's not the age of the rims that's a problem. I'm sure you could get a seal with a tubeless tyre.

If you compare a rim that is suitable for use with tubeless tyres they have an extra ridge that runs around the inside edges of the rim.

H.

dunk 1 · Post by **dunk 1** » 26 Apr 2009 10:33

I just checked mine - it has a metzler ME 77 tubed on the front but an ME 11 tubeless on the back - do I presume i should change the back one? or can I just see if it has been tubed and if so is this safe!

my other question regards pressures - my manual recommends 1.6Kg/cm2 0n the front which works out at 22.8 psi using an on line converter- this seems very low compared to the maximum 42 psi printed on the tyre - i know that this will be for a much greater load but the difference still seems too great. their website is no help and others tell you to look at the manual which contradicts the earlier post.

other than that after all last years fuss the bike is running great

thanks - duncan

Post by **SteveMRC** » 26 Apr 2009 17:53

I have always used tubeless tires with an inner tube on my 500.

As stated above our cast wheels are the wrong shape to allow a tubless tyre to fit without leaking.

Pressures I use are 1.8bar front 2.1 rear 26/30 psi
I can certainly notice when the front has lost a few psi, the rear does not seem so sensitive.

EVguru · Post by **EVguru** » 27 Apr 2009 09:54

Rims for use with tubless tyres have a safety rib to retain the bead in the event of a pressure loss. Without the bead a small loss in pressure might cause the bead to move and cause a total loss in pressure. Any one who's had a tubed tyre shift and shear the valve stem can tell you this is not a fun experience. Some won't be able to tell you because they're dead.

The starting point for tyre pressures should be those recommended by the tyre manufacturer. Tyre construction has changed over the years and in particular the sidewall is much more flexible and more air pressure is needed to support them. Start on the high and safe side with pressures and then work your way down untill you like the feel.