Trials Australia Forums

A few things have come together lately that prompted me to do some testing for how well a new Michelin tubeless X11 would fit to a few different 1970s rim types.
The first thing that happened was that the IRC rear tube type tyre that I had on a TY250D rim suffered a strange failure with the tyre cords in one location pulling out of the carcass, which rubbed through the tube and gave me a flat. When I took the tyre off I noticed that there was a crack at the rim weld. The third thing is that for the past 6 - 12 months I have not been able to source any more new IRC tube type rears.
That combination of events had me decide to do a series of test fits of a new Michelin X11, which of course are easy to source, but have been known to cause problems on some tube-type rims when the bead pulls in off the bead seat at trials pressures.
Advice from people who have successfully used those tyres on tube type rims was heeded. Greg Harding recommends using the rear rims that came on the Yamaha TY250A, and Tricub has previously explained that reshaping the bead seat on one of his bikes did the trick.
So four burst inner tubes and a few hours of upper body exercise later, I have found that Greg and Tricub are both right! Of course an easy thing for me to do with the wheel with the cracked rim, is to fit a TY250A rim, but I only had one of them available and there are a few other bikes that will eventually need to use Michelin tyres unless IRC starts selling them again. I used the cracked TY250D rim to experiment with for the bead seat reshaping, and after a few tries, the tyre stayed on the bead seat at trials pressures when tested on my practice sections this afternoon. I already tried the tyre on the TY250A rim last weekend and it stayed on the bead seat in the workshop even when I let the pressure right down, but I didn't ride with it.
To achieve success with the TY250D rim, the methods I used were to reshape the tyre bead with a stanley knife to reduce the taper on the seating face. This is to reduce the wedge effect that can push the bead off the seat.
The next thing was to mount the wheel in the bike (without the tyre) and use a hand-held 4" angle grinder to remove some of the bead seat nearest the flange. I estimate I removed between 0.5mm and 1.0mm from there to the width of the disc (5mm). This recess provides a key for the bead to grip on. Be aware that by doing this to a rim, it will be slightly weaker than a standard rim, and may not be legal to use on the road.
The standard bead seat on the TY250D rim is about 8mm wide and has a rounded corner.
The bead seat on the TY250A rim is 11mm wide and has a sharp corner. I think the wider bead seat on the TY250A rim may be why the tyre stays in place on this rim, but the TY250A rim is also about 12mm wider than the TY250D rim, and this may also play a part in why it works.
The bead seat on a standard shoulderless trials Akront rear rim that I tried is virtually identical to the TY250D rim (also 8mm wide and also with a rounded corner), and behaved the same as the standard TY250D rim, with the bead slipping off the bead seat at anything below 20psi.
I looked at a late model Pursang rim (shoulderless Akront the same width as the TY250A rim) and it also has wide bead seats, but at 10mm are slightly less wide than the TY250A rim. I have not test fitted the Michelin to that rim.
Here are a couple of photos in no particular order relating to this story. I will write in the text space for the photos to say what they are showing

Hi Everyone,

David, the other rims that I have X11's on without any problems are Honda TL 125, TL 250 TLM 220 and TLR 250, also Suzuki RL 250 and Bultaco Alpina 350. All of these rims differ a little in profile and I have not measured bead areas, but I think the key point is the width of the rim all about the same as TY250A. Hope this helps?

Purely for interest sake and not trying to be smart , but why wouldn't you just use a tube type Michelin ?

BT

Unfortunately we have been told by Michelin Australia Tube type X11 Michelins are no longer in production. They have been unavailable for a few months now.
We are trying to find a source OS of a suitable Tube type to import but it's difficult. The Michelin and the IRC were the only two suitable compounds for competition use. The Michy is finished, and the local IRC importer has not had supply of the IRC trials tyres (both types) for nearly two years.
If you can find old stock of the Tube type Michelins in any local stores I would suggest you BUY THEM until a suitable alternative can be found.

OK , sorry didn't realize , good old Tassie , behind as usual , last time I asked it was still no prob, anyway obviously gone now .
I have recently fitted a new X11 Tubeless to a new SM Pro Rim (MX, no bead retaining lip) using the Tubliss system , not cheap but obviously holds the bead out against the lip and of course has the added advantage of running tubeless !

http://tubliss.com/

Hi All, I still don't know why you need a lanyard and sharkfin for your personal safety but can fit a Tubeless tyre to your old bike that can roll off the rim at any moment and throw you down the road when you are belting back to the tent with your scorecard. Simply doesn't make sense to me. What are they doing for tyres in England? There are thousands of bikes there that will be affected. Perhaps we need to go to a control tyre in Classic and Twinshock like a Barum or such which will remain available.
Regards Geoff.

I think we have found a source to import IRC "tubed type" rear Trials tyres. Will keep everyone posted in the next week or so on developments.

We couldnt get IRC rear tyres here in the UK for a while,but they seem to be available again now.Never found out why it was,just looked and my best local supplier BVM Moto have them in stock for approx £80 inc Vat, (Same as GST) how would that compare for price in Australia if they were available ?

Jon V8 wrote:We couldnt get IRC rear tyres here in the UK for a while,but they seem to be available again now.Never found out why it was,just looked and my best local supplier BVM Moto have them in stock for approx £80 inc Vat, (Same as GST) how would that compare for price in Australia if they were available ?

That is a similar price to what IRC were here Jon, when they were available last.

Good that the price is similar,all too often I hear of big differences in Australia and NZ etc. I think the supply of IRC's dried up during last winter,it wasnt a problem to me as the 3 bikes I ride regularly all have good tyres(Not needed any for the last year or so).But my mate couldnt get one for his rigid Matchbox back in March,all he was told was that they were witing for a container to arrive.