Hello folks, thought I saw something awhile ago about running modern tube/tyre assemblies on wartime handbook tyre pressures but, because of different construction methods and materials, it's not a good idea to do so. I'll be riding solo, (no load initially as I'll be running the Beeza in ) to lightly loaded eventually, pup tent, sleeping bag, cider etc. Any guidance gratefully received. TTFN PETE.

email (option): petethejeep@hotmail.co.uk

I run 35 psi in the rear and 28 psi in the front of my 350 x 19 Dunlop K70s fitted to the M20..

If I'm very heavily loaded with everything bar the kitchen sink for a Normandy tour for example, I'll put a few pounds more in the rear..

Other negative features of running tyre pressures too low apart from poor handling are higher fuel consumption, uneven tyre wear and potentially problematic high tyre temperatures...Ian

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

I run a speedmaster front on 16-18 psi
And a K81 rear at 18-20 psi.

Been doing that for 25 years 75,000 miles since I fitted the speedo in 2005 with few problems

email (option): bsansw1@tpg.com.au

That may well be...but...

The Avon recommendations on their website for the 'Speedmaster' and 'Safety Mileage' tyres when used on classic bikes are 25-28psi front and 28-34psi rear..

They specifically mention the difference in tyre compounds between the modern and older tyres that lead to the increased pressure recommendations...

The factory manual for a Triumph T140 lists the pressure for a rear fitment K81 as 28-32 psi....

The K70s fitted to my M20 are definitely not stable at 18psi with the bike fully loaded...In fact it becomes unstable before that low a pressure is reached...Ian

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

Interesting, Ian and that was also my thinking after hearing the same from an Avon rep. However on checking out Dunlops website (took some finding) I came across this.


Which shows for K70 3.50 X 19 a max pressure of 32 when the wheel is loaded at its maximum 507 lbs

Interesting...I couldn't find the Dunlop site when I looked (or at least not that chart) and I have long forgotten where I got my tyre pressures from for these tyres...

In the light of that information a slight reduction in the pressure I use for the rear tyre would be in order...Generally I run 33-35 psi in the rear but on occasion when fully loaded a couple of pounds more...Ian

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

Yes this is interesting I usually run my bikes with modern tyres at around 28 front and 30 rear. I haven't loaded for camping for a while now but would increase the pressures a couple of pounds.

I contacted the Dunlop technical division a few years ago to ask about pressures in their K70's. They would not confirm a figure and told me to just stick to the manufacturers recommendation........Even though I told them that these are now obsolete.

Good to see they have formed a chart now. Ron

email (option): ronpier@talk21.com

I run the same combination on the A 10 and there I go 25 front & 30 rear
But I find the harder tyres quite unstable on my M20.
The front any higher than 20 psi skips all over the place and shakes badly under breaking.
The rear could be run harder but you end up with the front with a lot more traction than the rear which is fine on a short circuit track , but not quite predictable enough on tar in traffic.
I don't do a lot of riding, mainly 500 to 1000 km runs 4 or 5 times a year plus a few 100 km club rides so it might be my compound has just become too old and hard,
Also remember that the recommendations do not take into account the use of rim locks and I have 2 in the rear of the M20 , 2 in the B40 and 1 in the A10.
In fact the only bike without rim locks is the bantams, B2 & B50.

email (option): bsansw1@tpg.com.au