Hi there
My rear tyre blew whilst I was on the a12. When I took it off this had happened! What is the cause? Has this happened to anyone else here?
I had a soft rear tyre as I thought that may aid a bit in the rear shock absorbtion.

email (option): hutman80@hotmail.com

Hi Maxwell, The soft rear tyre was the likely cause of your problems. On trials bikes and WD bikes where tyre pressures were dropped to aid off road traction tyre clamps were fitted to prevent the tyre turning on the rim and ripping out the valve. A return to normal pressures after replacement should prevent a recurrence of the problem..or you could fit tyre clamps....Ian

email (option): ian@wright52.plus.com

Yea thanks ill pump the tyre more.
So far every journey I made has ended in breakdown!

email (option): hutman80@hotmail.com

Yes, when this happens everyone blames the tube, when in fact it usually happens just after that nail penetrated the tube! Or in your case as Ian said.

I have those ancient, petrified WD tires on my M20s. I tore a valve stem off once, and it was a week before I noticed!

Tyre clamps are awfull and a total waste of time!!
Dont use them..Bin them!!
We use to race sidecars grass track scrambles and twin shocks no tyre clamps there!!
We still do the self tapper through the rim to catch the tyre bead at the side rim 2 on each side,no problems with tyre alignment etc.
Use to race the Blown Puma Triumph with Shorriks Supercharger on Gas Track which had mega power and torque tyre clamps on this would be a waste of time.
Best way to go is the self tapper through side rim into tyre bead where its wired reinforced and lots of rubber.
Fit the tyre pressure up turn in the screws...job done!
Tyre clamps bury them in the bottom of the garden.
Rubber grommet the holes left on the rim where clamps were.

After you can apply as much torque as you want and even burn rubber doughnuts with your road burner M20.

I spent 2 hours cutting an old tyre off my M20 because it wouldnt budge, until I realised it had a tyre clamp fitted!

The bike was fitted with a side-car in the 60's, hence why the clamp was fitted I presume.

email (option): adh325@hotmail.com

i thought the tyre clamp was a standard fitting on an M20 there isnt enough power to warrant screwing the tyre on if you dont like a tyre clamp 2 small drop of super glue would do the trick(joking)

Why are you guys even bothering discussing the issue with tyre clamps??????????????
Read my note bin them!!
Das dig a deep hole in the garden and plant them there...there useless total waste of time!!
Go and do what i said remove them grommet the hole.
Go the same direction like us racing boys!!
Do the self tap on the wheel rims 2 on each side even use stainless if your into stainless.
No more uneven tyres and raging tempers busted tubes.
It was duff idea from Dunlop probably a Friday afternoon bender!!!
How the hell can a wheel be balanced with a nugget of a clamp odd balled to a wheel doesn't make sense!

Niether tyre clamps or self tapping screws are necessary ,in my opinion, on an M20 running modern tyres at the recommended pressures (or even old tyres at modern pressures). I have done countless miles on the road and also 'played' off road frequently without any type of 'tyre locking' (albeit without reducing tyre pressures) and have never pulled a valve. (and my 'oversize' M20 produces considerably more torque than a standard M20)
If you are going to engage in more serious trials work and plan to benefit from reduced tyre pressures then one or other of the methods described will be needed...Ian

email (option): ian@wright52.plus.com

What "ever" " ever"
Ian you running round and round on the grass park trying to do trials on an old cooker you plonker??!
That`s what they are ..a cooker with no power.
No need for clamps like you said...throw them away!
True do with out, for competition we did this.still do!
For a cooker you don't.,,ones raced "M21s they did tapped rims,
Just throw them away bury them deep!!!

I'm no trials expert..I managed three sections of a pre 65 trial on the M20 before I ran out of steam. I ran out of power and ground clearance on the first section.. You have to admire the riders who did it originally on M20s...but I do like to play in the mud..Plonk..Plonk...Plonk.. ...Ian

email (option): ian@wright52.plus.com

Just replaced the tube and used more tyre pressure. I have just done 100 miles its still cool.

My m20 frame has a b33 lump with a load of goldstar garb inside it and 8.5:1 cr. its quite pokey.

email (option): hutman80@hotmail.com

Hello Maxwell
I had a similar experience to you 2 years ago on an old Matchless G80. My rear tyre was a very old Avon SM. I let the pressure get a bit low and when out for a spin I was getting clutch slip. Only it wasn't clutch slip, the wheel was spinning in the tyre! The tube was shredded but I managed to ride home on the wooden Avon.
Paul

Yea cool, I had a new Avon sm on there, Whe it went it felt like the back of the bike had snapped off!

email (option): hutman80@hotmail.com

What constitutes "low tire pressure"? I have TP 18 painted on my mudguard, were you running less than 18psi?
I can see why the originality conscious owner would keep the tire clamp, afterall it was original and period, so are magnetos, horsehair seatcushioning, girder forks and generator electrics, but you don't see everyone binning them just because they are old and tired. Those of us who like to tinker with old bikes keep these quirky parts in place because we like them.
But then again, I just fitted a new rear tire and didn't fit the tire clamp because it is a royal pain in the butt to fit. Guess I'll sneak it out and bury it in the garden...
Vince

email (option): bsa3man@rocketmail.com

Hi Vincent..There is certainly an argument for having the bike unmodified and fully equipped to experience the ride as it was when the bike was built.
Unless period tyres are fitted the original tyre pressures should be ignored as they are unsuitable for modern tyres..My bike has Dunlop K70s fitted and these require about 35lb in the rear to maintain stability when the bike is fully loaded and to avoid Maxwells problem...so anywhere below that figure (for that tyre) would constitrute 'low tyre pressure' I guess. About 25-28lbs seems to work well in the front tyre.
K70s do not have the strength in the sidewalls of the earlier tyres and it is the higher tyre pressure that keeps everything 'firm'.
Tyre clamps certainly are an additional problem when it comes to changing tyres. I know some people fit a bolt with the head machined right down into the rim to maintain the 'look' of a tyre clamp but without the extra hassle...Ian