increasing swing arm clearance

I have read a few times about people altering the swing arm on tonti frame bikes to give more clearance for tyres

any ideas whats involved or how its done

Personal thoughts
the tonti frame works a dam site better with the standard size tyres
if you put wider tyres on them even if you do the same front and rear by same ratio the handling of the Tonti frame goes off drasticcally

I would advise stay standard I have been down the wider tyre route and it does not work

I’m stuck with 16 inch rims and the narrowest tyre I could get still rubs two up

Are you fine solo
and is it rubbing two up on side or top
if rubbing top longer shocks with more strength
if rubbng on side two up I would look at swing arm pivots for side play
or two up needs more air pressure in tyre to stop the tyre deforming

fine solo, it only rubs against the drive shaft tube when two up

how much higher can I safely go with tyre pressures, book says 36 rear and Im already at 40 psi

Profile of tyres can vary, some have a much wider shoulder than others of the same width. Some time ago there was a post on this and frm memory BT45 s were narrower than Avons

The mod you are referring too is to put a notch in the wall of the arm - Nigel at NBS should be aware of how to do it .In your case I’d agree with the other posts- must be that the tyre sizes are not quite what they say.I’ve also found that by going up in size on the rear from what was standard negatively affects the handling.

I cannot go any smaller and deff have no intentions to go any bigger

Took me 3 different tyres to find one that had enough clearance

Grr 16in wheels are a pain in the …

only 16 inch wheel t5 owners fully understand this problem ,i have an avon on the rear and the clearance is less than 1mm .talk of putting a bigger tyre on is impossible any way and changing tyre pressures or shocks in my opinion will not help .Im going to be very careful with the grinder if my next tyre touches the swing arm but im willing to risk it
johnno2013-06-02 14:16:57

this is very true

BT45 spec says 138mm wide when fitted to a 3" rim

My Avon venom x is 137mm and touches 2 up

Yes my front Venom rubbed on the mudguard, had to sandpaper a little bit off the insides of the mudguard’s fork mounts (it’s the plastic Spada / LM style), so I’m thinking this is typical. No previous tyres did this, Pirelli Phantoms certainly didn’t

Could you swap it for a LM1000 swingarm which has a dint in it for a wider tyre?

I’m on 16" wheels not 18’s so the swing arm is shorter :frowning:

I’m hoping to order another venom x as a stop gap for the rear, then hunt about through other brands till I find something

It’s a shame you cannot shim the rear wheel over a few mm! I know that would not do the handling any favours…!!

could always mark where the tyre is on the arm and actually cut a piece out the swing arm and them have the hole welded up flat could easily gain 5 mm this way

That’s exactly the mod that was usually done on 'racers " !!!

It’s going to have to be a swing arm mod :-(I’m going to call Carol Nash and have a chat about the insurance implications of the changes, shame the rim is so wide as a MT90B16 is the same as a 130/90B16a narrower section tyre would help massivly

Can someone explain why being two up makes a difference to the clearance at 90 degrees before the road contact point?

Amadeo at Raceco used to offer this many years ago.

I personaly would be happier taking a mil off a tyre before taking a mil off my bike. But thats me and I aint no scientist.