Tyres

[chaterlea25]

Hi All,
I am fairly sure that there was different information on here before about Dunlop and other brand tyre pressures
The modern K70's bear no relationship to the old ones except the tread pattern
They seem to have the softest carcass in comparison to current comparable tyres, the old ones could be
ridden home flat without coming off the rim
I threw a new type one (that had been discarded) onto a front wheel of a project bike (no tube) to roll into an autojumble to sell,  it would flop about allover the place

The reason to increase the pressures from the original handbook figures is that due to softer construction the tyres can creep on the rims, leading to valve pull out (DO NOT tighten the locknuts on the valve  )

I know that 18psi with an Avon or Metzeler on front, the SR will behave badly

John

[RogerSB]

Please note: I've attached my email to Dunlop in my reply no. 27 to emphasise that my question to Dunlop was about Dunlop Gold Seal K70s tyres - and not any other tyres.

[chaterlea25]

Hi Roger,
Yes I saw that reply
I simply do not believe you got the correct information

John

[RogerSB]

Hi Roger,
Yes I saw that reply
I simply do not believe you got the correct information
John

Hi John, I always respect your input and opinions - and I certainly do here and I'll make a point of checking for any valve creep.
The only thing I can say is that the Dunlop Gold Seal K70 is actually a 1970s tyre. The new K70s are called Dunlop Classic K70. I don't know if there is any difference in the manufacture .

Edit: Just checked and no sign of any valve creep in either tyre, that's in the 3 years that I know the tyres have been on my GF.

[RogerSB]

By-the-way here's one for sale      .

[Triton Thrasher]

Hi Roger,
Yes I saw that reply
I simply do not believe you got the correct information

John

Agreed.  Whoever replied is scared to disagree with the ancient BSA handbook.

[chaterlea25]

Hi Roger,
Back in the day I believe the tyre carcass was "canvas" now its nylon so much more flexible

John

[RogerSB]

Agreed.  Whoever replied is scared to disagree with the ancient BSA handbook.

Mr Peter Wayte, Senior Advisor, Technical Customer Support & Service, Goodyear Dunlop Tyres UK Ltd.
08453 453 453 Option 3.

I don't think I'm qualified to argue with him.

[Triton Thrasher]

Agreed.  Whoever replied is scared to disagree with the ancient BSA handbook.

Mr Peter Wayte, Senior Advisor, Technical Customer Support & Service, Goodyear Dunlop Tyres UK Ltd.
08453 453 453 Option 3.

I don't think I'm qualified to argue with him.

You’re fully qualified to ignore him.

[Black Sheep]

Some of the tyre pressures mentioned do seem a bit high. I run 22 front, 25 back on the A7 and A10 and that works for me. This move to pressures of 30+ psi seems to have come in with radial construction tyres for modern bikes. Understandable for them but with our crossplies, even with slightly more flexible sidewalls, going that high seems a bit much. But what do I know? P.S. I generally reckon about 6000 miles from an Avon SM Mk II on the back. P.P.S. I really don't like Dunlop K70s. I have found them rather prone to let go when properly cranked over (a few properly scary moments) and they don't last. 1300 miles out of the last one, admittedly on a highland tour in company with modern bikes and not hanging about.   

[Flashgreubon]

Hi from Cork,
 Here is a tip i got from Grant Johnson, famous long distance rider who travelled the world for the last 50 years.
When you are in the sticks, with an over loaded bike on hot stones or frozen tarmac, how do you decide what pressure you pump your tyres at ?

 The last thing you want is waste your power into heat by running an underinflated tyre.
 Also you need your tyre to flex to increase its road contact area in order to provide grip.

This  is how to calculate:

 -First thing in the morning take your tyre pressure with a telescopic analogic pocket guage.
 -go for a good ride with your bike loaded with your gear.
  -stop and remeasure the tyres pressure when they are hot (with the same guage)

Back tyre  pressure should be between 5-10%higher than cold
Front tyre pressure should be between 3-5% higher than cold.

This is valid for all tyre types , bikes , loads and road surfaces.

[Worty]

I think Mr Wayte is playing it safe.  If he advises changing pressures and a problem occurs, he could get the backlash.  Although the carcass may be similar in construction, I'm pretty sure it won't be the same materials used from the 60s when tyres were akin to rubber blocks an had a much firmer structure altogether.  Ultimately, it's down to the rider and whether one uses one's own judgement or that of another authority (I'm the former, not the latter).  As an aside, when I first started riding the Flash, I used BSA's advice on pressures on Mitas tyres.  The bike was a little 'wallowy' at times but I put that down to it being an old bike.  When I mentioned this to my engineer pal (50 years BSA/classics experience), his eyes almost popped out and gave the reasons mentioned here - he also raced on IoM.
I guess if you're pottering around, then pressures may be less of an issue than Berger's or Musky's (heh).  Wonder how the cops would ascertain the best pressures for our bikes if some arsy kid with God complex pulled one over and decided he was going to be clever?

[bsa-bill]

I think Mr Wayte is playing it safe.

As an employed person he's probably well aware of his employers reaction if he was quoted in court for any reason, nobody is willing to give advise these days for fear of litigation, I'm on Warfarin, when I was first put on it you could phone the local clinic and get help with altering your daily dose for whatever reason, last year I needed two teeth removed, no - one would give me any guidance as to how much to miss to get my score down so the dentist could pull the teeth, in the end it was just a guess, could have gone very wrong.
That is the way it is unfortunately

[Topdad]

I changed to Am 26's and at first ran them on the same pressure as the skidmasters I'd had previously , they were pretty bad ,following advice from here I pumped 'em up and now use 30 front 32/34 back and the difference is startling really impressive and personally I don't think the tyre pattern is that "off" for the bike , not that I'd be bothered by that as it's my skin !

[Worty]

Heard a lot about AM26s and may try them in future.  Just working my way through the budget brands at present to see what suits.  Would you recommend staying with 3.50 x 19 or something bigger?

Bsa-bill is right, everyone's scared to depart from the 'party line' these days for fear of litigation.  I think if I was in Mr Wayte's position I would still play safe-ish in giving non-committal advice but would refer the inquirer to BSAOC for more general advice!