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[jefrs]

The 2007 Bullet Classic 350 is not really all that old.

Owners Manual 2014 for indian Bullet 350 with 3.25x19 http://royalenfield.com/support/owners- ... bullet-350
>br>I'm actually surprised to see front pressures up in the 30s. I've run a lot of british bikes and they all had fronts down in the low 20s. Except with a chair on, then you need more air up front.

We took the chair off the Squariel because the engine was knackered and a trip in a Urinal put me off putting it back on.

[ric]

These manuals seem platen happy to quote figures derived by the UK factory back in the 50's, that includes tyre pressures and ignition figures.
Fuel and tyre compounds have changed since then and consequently these 'gospels' are in desperate need of realignment 60yrs later.

[jefrs]

Ric - what you say about the compounds is perfectly true but the contact area is physics and it doesn't care what the rubber is.



With RE having overtaken HD with production now around 450,000.p.a. making them something like world's 5th largest - there's an awful lot of bikes running around out there with the wrong tyre pressures if RE are wrong ???

[jefrs]

Ok, I'm going to work it out with a pencil. I'll use a lot of heavy-handed rounding because it's not an exact science. Given weight of bike 187kg with 65kg on the front wheel means 122kg on back. Add 100kg rider with same distribution, add 33kg to front and 66kg to back.

gross front 100kg (220-lb) rear 190kg (420-lb)

given, rear pressure 30psi (use easy round numbers), contact patch is 420/30 = 14-sq.in.

we want same contact patch at the front or we come off, thus 220/14 = 15.7psi

Yes! It's as low at that to get a decent contact patch down.



I have not allowed for greater front loading under braking. That will necessarily push the front pressure up.

My loading for the rider may need 50/50 split front to rear. If we do that then 115kg front, 177kg rear at 30psi = [13-sq.in.] 19.5psi front. (if you use 30psi in the front you only get 8-sq.in. of grip - splat!)

QED - but can you see how it's done?



Please be safe

[Presto]

What is all this!!?? We’re talking tyre pressures on a Bullet – not Thrust 3! Front about 20 – 22psi; rear about 28-30psi. Not a problem!

[ric]

Well 19.5 front & 30 psi rear seems fairly close to 20-22 front 28-30rear
3yrs ago I attended a lecture followed with a Q&A session given by the guy responsible for Avon motorcycle tyre design. I left with the distinct impression that both he and their full time professional rider knew slightly more about tyre pressures than I did I'm more than happy to use their recommendations for my specific set of tyres.

[Dennis C]

But Ric, everyone on here knows more than the tyre makers, ;-@

[Scalyback]

(sorry, I can't resist the chance of a re-run...)What thread are the tyre valves guys?




Oh, that's really naughty of me!

[Dennis C]

It's a 0.307 X 32 UNS.

[Dennis C]

Well you did ask!!!!!!!.