I have been away from road bikes for some time and am out of touch with the latest generation of tyres, although I have done many thousands on road k's and raced for a number of years in the past. I have a new set of Pirelli sport demons on an RT, running 32 and 36 psi front/rear. Tyre temperature and visual condition seems good after a few hundred km's. I have been looking at Pirellis site and they say 36 and 42 psi (2.5 and 2.9 bar). This seems a little on the high end to me. What do you think?

Peter

Just set mine today, specs from under the seat say 2.25 front, 2.75 rear with 2 up riding...

I've worn three sets of Sport Demons off on my K100RS and two sets on my R100...if you don't use at least a minimum 38 psi in the front it will 'scallop' along the edges, and in the rear I use 40-44 dependent on load and speed/heat. What it says under the seat for an '80s era K bike is just about obsolete for any tyre nowadays. This is my personal experience with the excellent handling but somewhat short-lived Pirelli Sport Demons.

Try this technique. Pressure the tyres to what you reckon should be good. Record it. Go out and ride the bike as you normally would with the weight you expect to carry and at the speeds you will likely ride. Stop after twenty kilometres and take the pressure immediately. Did the static inflation pressure rise more than 10% of that initial pressure? Too low to start with. Add more and give it another go. Did it stay the same or rise only very slightly? Too high to start with, or about right, depending upon any previously mentioned temp/speed/load factors changing.

I have always used the tried and true method. If the pressure goes up more than 4PSI it is to low and less then it is too high, it has always worked to give good tyre pressure.

good tips guys .....thanks

Excellent advice from TWB. One thing to beware of is many people I have seen on websites simply say "I run mine at the pressure on the sidewall" missing the fact that the pressure moulded in there is the maximum not the recommended. The pressure rise method quoted is the best way to tell the right pressure for your bike, your weight and your riding style.
Regards,
K-BIKE

There's one more thing about tyre pressure that got me thinking...
Several years ago I spent a fair bit of time at the track for 'track days' on my stripped R1100RS, and as a hand round the paddock with mate's race bikes. Those blokes weren't interested particularly in tyre tread life but wanted maximum grip in all conditions. We of course have a slightly different idea for riding on the street. Most of us want the bloody expensive rubber loops to last a while. They're not cheap, unless they're Chinese, then they're usually crap (there, I said it). The boy racers would drop their pressures to 30 psi or thereabouts. The idea being that with reduced air pressure they'd heat up due to friction and hold better to the relatively stable track surfaces.

We have a whole stack of different requirement with potholes, wet conditions, sand and gravel, cow flops, diesel spills, off camber corners, roundabouts, errant car drivers, a wider range of road and air temperature and etc. We want the tyre to do it all from the moment we spin the throttle and are off on the commute to work, or touring, or playing our own version of boy racer on the backroads and canyons of a Sunday morning. We don't preheat our tyres as they do. We add pressure to keep them from heating, reducing their rolling resistance, and as you all know, under-inflation encourages wear, but promotes grip.

Regarding pressures, original BMW recomendation 33/36 psi for riding solo under 180 km/h is for bias tyres, for radials there is a service bulletin (issued in 1987 for approving radial Dunlops on K100rs and rt, check download section) recomending aditional 4psi, that would be 37/40. Bullletin does not indicates nothing regarding pillon riding or over 180km but the original 39/42 seems ok due to maximum pressure on most tyres. I´m riding dunlops 402 and the above indicated pressures are working fine.
Best regards
JAP

Two Wheels Better wrote:..... and as you all know, under-inflation encourages wear, but promotes grip.

Yes, the area of contact will increase with the reduction of tire pressure. You just have to find a balance between premature wear and grip (security).
The only problem with an under inflated tire is that the steel belt will sustain more stress and could break.

I once had a contract with a tire company to help solve some manufacturing problems. The process of making a tire is quite unique, and before visiting the plant I didn't have a clue of what was involved.
Would you believe that before going to the steam 'cooker', a tire is no more than a rubber cylinder?

Check the following video...

Thanks for the help. I will increase the pressures and monitor the rise from cold to hot.

Its interesting to see the changes in tyre technology over the years I have been off road bikes. When I was racing I would run 38psi in the rear for endurance racing as that would get the tyre through 2 hours, and a little less for spint races. When I look back on those weekends its no wonder it had to stop when I got married. It was common to use 3 rears, 2 fronts, 2 sets of pads, and 100L of fuel in a weekend, and all for $150 prize money for a podium finish! But it was about the best fun I've had on a bike.

Well I increased the pressures and went for a ride over some twisty roads today.
Rear started at 40psi, and increased to 45psi.
Front started at 38psi, and increased to 41psi.
Based on the advice above it looks like I need 1 or 2 more in the rear and the front should be ok.

Not holding my breath over high mileage from these though. The front is already scuffed up out near the edges. Maybe that will settle with a few more miles at these pressures.

Thanks for the help guys.

If you're carrying a fair bit of weight, riding aggressively, or the road surface and air temp are warm, all of these factors will contribute to the rear tyre pressure rising more than the 10% mark. The 3 psi rise in the front tyre sounds about right. Though I have 'salvaged' a scalloping front Pirelli Sport Demon by increasing the pressure and actually getting better, extended life from it. I'm at 38-40 in the front and 42-44 (mostly riding solo) at the back now.

On my unladen RS and I manage about 13000-14000 kms per front and only about 9000-10000 per rear, commuting kilometres, down just to the tread wear bar. I don't keep 'em on much longer than that. The rear Pirelli flattens off too quickly and the handling transition from upright to cornering suffers noticeably. When new and to just past the half-way wear mark they handle really well and so I continue to use them, and they're excellent in the rain. I'd like better mileage from them but that's the compromise.

Didn't think that was bad milage TWB until I realized you meant kilometers! You must be doing some serious back road scratching on your days off!

OG

I reckon the Pirellis are made a bit soft, but I really like the way they handle the corners and stick in the wet. The Mighty K is a bit heavy too. I think they'd be ideal for a middleweight bike in the 500 to 750cc category. I'm whacking a new one on the back today anyway for the weekend ride. The front will just about go the distance of two backs.

Yeah, wet traction is of paramount importance around here. Are these the correct model? http://www.motorcycle-superstore.com/1/28/396/6243/ITEM/Pirelli-Sport-Demon-Sport-Touring-Front-Tire.aspx

Thanks,
OG
p.s. Hope you guys have a blast this weekend and pics please!?

Yeah, that's the front tyre, which I really like, and Charlie has on his bike too.

And this is the back tyre version:
http://www.motorcycle-superstore.com/1/28/396/6244/ITEM/Pirelli-Sport-Demon-Sport-Touring-Rear-Tire.aspx

Thanks mate! Just wanted to double check on the sport touring designation as I wouldn't think they would be that soft, but as you said the ol girls are NOT dainty little things, lol!

OG

thems the fellas og .......nice price too

so far i would have to agree with twb .....those tyres made a huge difference to handling for me .
since putting them on i have done the twistys and the hiways and they perform verry well .

Thanks mate!

OG

the tricky thing I find about tyres is

How hard to kick em?

reg_K100RS wrote:the tricky thing I find about tyres is

How hard to kick em?

tooo funny


you know its too hard reg ...............when the bike falls off its centre stand ...... maybe ...huh ?