Trials Tyres

[stwinton]

I wonder if anyone else has had this problem...I just completed restoration of a 1971 M80 Sherpa T 250. The rear tyre is slightly fatter than what my old mans memory serves. I am told by someone who shall remain nameless, but should know that the original rear tyres were not quite as wide. I can run what I have (Pirelli 18x4) when its inflated, but it is unridable at lower pressures. I have been searching for slimmer rear tyres without success...does anyone have any ideas or suggestions?

Also, are there any low key comps I can enter into? (Victoria). Cant see the point of having her a museum piece...

I attach a photo of the old girl for anyone interested...

[David Lahey]

Yes your fathers memory is right - modern trials rear tyres are slightly wider than 1970s rear trials tyres but a bigger difference is that the modern rears which work the best (IRC and Michelin) are considerably larger outside diameter than 1970s rears. An IRC rear will fit if you have the rim, chain guard and exhaust in exactly the right places. I can do a photo of my 1968 M49 with new IRC for reference if you want. The swingarm on your M49 Kit Campeon or M80 Sherpa (can't tell which it is from your photo) will be very similar or identical dimensionally to my M49.
Michelin tube-type rear is probably the slimmest, but are an old style construction and don't work very well. Michelin tubeless works well but I'm not sure it will stay on your bead seat. I haven't fitted a Pirelli for many years so can't comment on that. MITAS is smaller outside diameter but wider than IRC and don't work well. Dunlop is about the same size as IRC but I don't think a Dunlop would stay up on the bead seat on that rim.

[Jon V8]

Nice looking bike there - be a shame not to use it. Dont know if its any help,but the VMCC here in the UK do a 3.50x18 trials tyre - no idea how good they are.
http://www.vmcc.net/vmccshop/scripts/tyres.asp?cat=18
Its listed as a trail tyre,but may be good enough if you arent worried about high level competition.

[Geoff Lewis]

Hi stwinton, I suggest a Vee rubber as they seem a little narrower and are economical and grip ok for what Twinshocks are rquired to ride in Vic (in the dry at least) I suggest you join the Oakleigh motorcycle club if you live in the eastern suburbs of Melbourne as they have an excellent Trials complex in Clayton South and practice is conducted almost every Sunday and Thursday night during daylight savings. If you live in the northern suburbs you may consider joining the Harley Club as they are now becoming more invoved in trials and own a unique and magnificent property next to the MV complex in Broadford and will be hosting the Vic Twinshock Challenge there in October of this year. If you live in the Bendigo region I suggest you could join Trials Club of Victoria as many of their members are Twinshock enthusiasts who are very resourceful and helpfull. If you live near Ballarat, Ballarat Rovers MCC is the go. Stan M has re-established the Twinshock line in Vic trials this year which is roughly half way between Novice and C grade with no big obstacles or steps which should encourage people to have a go. Hope you can get started soon.
Regards Geoff.

[Stanm]

Excellent comments Geoffery. Trials in Vic is great!!! Nice weather and Cool.
I have two types of rims on my TY's. They both measure about 67mm across the widest part of the rim.
One type I can use tubless Dunlop and Michilins.(18X185B)
The other type they wont stay on(18X185). I have had good success with this rim using the IRC tube type tire. It has become my favorite tire art the moment.

Hope the helps

Cheers

Stan

[Justdrew]

I recently fitted Kendas to my 158 as they were DOT approved and I wanted to use it as a trail bike, I don't expect great traction for trials from them but I might yet be surprised. They seem to be the same size as the orginal Pirellis which were vertually unworn but perished.
They weren't all that expensive either.