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Tyre pressures
- Thread starter Rouqui
- Start date
Scim77
0
This tyre pressure malarkey has puzzled me for some time. I cannot understand how 33/36 psi can be correct for all riding loads in all conditions. How can this possibly be?
Passenger cars quote a range of tyre pressures, depending on how heavily the car is loaded and how fast it is expected to go for sustained periods of time. For example, a VW Golf would run at 34psi F&R for two up with a bit of luggage, but 37/44psi F&R for five up with full luggage load.
How can the MT-07 stay at the same pressure front and rear regardless of payload or speed? Surely the bike should have different pressures depending on payload. I am only 10 stones in my gear and cannot believe that I need exactly the same pressures as a fully loaded (381lb) bike with a 16 stone rider and 11 stone passenger!
I shall continue to experiment with different pressures to suit my weight, in order to maintain a reasonable tyre footprint on the road. So far 28/31 seems a nice balance for me.
I realise that modern tyres are very high tech engineering but am I missing something, or is Ralph correct?
I just thought I'd check mine, eve if the bike is parked.
I first used my tire filler I use on my compressor, like a pistol ting with a gauge and hose made to fill tires and stuff.
This said the pressure was 22/30, so low. I dont trust this gauge because it has a very long range (0-220psi) so I got another one, a very simple thing that pushes a pin with a scale on out the back.
This said I had 30/35, so closer to what it should be.
Guess I have to get another gauge to make sure, perhaps a new filler gun wth a shorter range is in order.
I first used my tire filler I use on my compressor, like a pistol ting with a gauge and hose made to fill tires and stuff.
This said the pressure was 22/30, so low. I dont trust this gauge because it has a very long range (0-220psi) so I got another one, a very simple thing that pushes a pin with a scale on out the back.
This said I had 30/35, so closer to what it should be.
Guess I have to get another gauge to make sure, perhaps a new filler gun wth a shorter range is in order.
I've seen somewhere that tyre manufacturers have a default recommendation of 36 front 42 rear for most bikes, including some pretty heavy ones such as 270-Kg tourers - and that covers all conditions up to max. load. Clearly that's not going to be optimum for a lighter bike that's not fully loaded, but it minimises the chance of a blowout, and it allows for folks who don't check their pressures from one month to the next. I suspect some dealers just stick that in irrespective, without looking in the "book".
On the other hand, some bike manufacturers do show different settings for solo and 2-up, e.g. the Aprilia Shiver (210 Kg wet weight, same tyre sizes as the MT-07) is 33/36 solo, 36/42 with passenger.
Yamaha go along with the 36/42 rule for bigger stuff, including my Fazer8 (220 Kg wet weight), but have obviously decided that it's a bit OTT for a light bike like the MT-07 which will spend most of its time with just a rider on board, so have relaxed it. Oddly, for the MT-03, which actually weighs more than the MT-07, but came originally with pseudo-trailie tyres (and the rear is a smaller section 160), the recommended pressures are only 30/33 for all load conditions. And if you go to a true trail bike with genuine offroad ability (and narrow tubed tyres) it'll probably be something like 18/22. Go figure.
And then there are all the combinations of pressures that people use on track, which are always lower than road pressures, even though speeds and temperatures are higher.
So I think the answer is to experiment and see what gives you the best combination of comfort, grip and life. But don't stray too far from the manufacturer's recommendations, as I'm sure an insurance company would use that as an excuse if the worst happened.
On the other hand, some bike manufacturers do show different settings for solo and 2-up, e.g. the Aprilia Shiver (210 Kg wet weight, same tyre sizes as the MT-07) is 33/36 solo, 36/42 with passenger.
Yamaha go along with the 36/42 rule for bigger stuff, including my Fazer8 (220 Kg wet weight), but have obviously decided that it's a bit OTT for a light bike like the MT-07 which will spend most of its time with just a rider on board, so have relaxed it. Oddly, for the MT-03, which actually weighs more than the MT-07, but came originally with pseudo-trailie tyres (and the rear is a smaller section 160), the recommended pressures are only 30/33 for all load conditions. And if you go to a true trail bike with genuine offroad ability (and narrow tubed tyres) it'll probably be something like 18/22. Go figure.
And then there are all the combinations of pressures that people use on track, which are always lower than road pressures, even though speeds and temperatures are higher.
So I think the answer is to experiment and see what gives you the best combination of comfort, grip and life. But don't stray too far from the manufacturer's recommendations, as I'm sure an insurance company would use that as an excuse if the worst happened.
Scim77
0
Good advice bobh. Thank you. I wonder if the MT-03 rear wheel would fit the MT-07, so that we could experiment with a more appropriately sized 160.60.17 tyre, instead of the absurdly oversized 180. But if we did, we would definitely run foul of Insurance Company liability, even though we would be making the bike safer and handle better! Its a strange situation. When I need to replace the rear tyre I will fit a 170.60.17, which is still acceptable to the Insurance Company, since it officially fits a 5.5" rim.
There's a theory that goes if the hot pressure is more than 10% higher than the cold the tyre is flexing to much and you need to set the cold pressure higher,
If less than 10% then it's too high.
So set your rear at 36 cold and if after a good run it.s 39.6 it's spot on if higher say 43 go up say 2lb you are then looking for 41.8 hot but it wont change as much
due to less friction and flex, The tyres on mine don't seem to get as warm as other bikes I ride so I suspect the standard pressures are a little high, a Burgman
I used to ride would get it's rear tyre worryingly hot on standard pressures admitted I used to ride it a bit hard.
If less than 10% then it's too high.
So set your rear at 36 cold and if after a good run it.s 39.6 it's spot on if higher say 43 go up say 2lb you are then looking for 41.8 hot but it wont change as much
due to less friction and flex, The tyres on mine don't seem to get as warm as other bikes I ride so I suspect the standard pressures are a little high, a Burgman
I used to ride would get it's rear tyre worryingly hot on standard pressures admitted I used to ride it a bit hard.
Bought a new pressure gauge today, a fairly good quality one. This had a range from 0-40psi (0-3bar).
With this my pressure was 27/36, so I just topped up the front a little so they sit at the recommended 33/36 now.
Now its just a matter of waiting for spring to arrive.
With this my pressure was 27/36, so I just topped up the front a little so they sit at the recommended 33/36 now.
Now its just a matter of waiting for spring to arrive.
.....I wonder if the MT-03 rear wheel would fit the MT-07, so that we could experiment with a more appropriately sized 160.60.17 tyre....
I very much doubt it. And even if it did, I'm not sure I'd want to.
The MT-03 hub and cush drive are related to the other 660 singles, which means the bearings and rubber cushions wear out depressingly quickly - it's one of the weak points of that bike.
The XJ6 has/had a 160 rear tyre, I think, so that might be a more fruitful line to pursue.
I very much doubt it. And even if it did, I'm not sure I'd want to.
The MT-03 hub and cush drive are related to the other 660 singles, which means the bearings and rubber cushions wear out depressingly quickly - it's one of the weak points of that bike.
The XJ6 has/had a 160 rear tyre, I think, so that might be a more fruitful line to pursue.
Can confirm. My MT03 went through a complete set of wheel bearings and cush drives in 15,000 miles, which seems very little. It's not just the back though, it needed new head bearings and front wheel bearings at the same time.
Small tip - you can extend the life of cush drives a little by shimming them with pieces of cut up inner tube - put the rubber piece against the surface that the c/d's are pushing when you drive. I did mine about 3,000 miles before they needed replacing altogether, it did tighten things up nicely for a while. having said that, a new set is only about £25, so it's not like you're putting off a huge bill.
Scim77
0
Neither do I. I will stay with the 5.5" rim. I use a calibrated dial guage and currently run at the book pressures of 33F/36R. I checked tyre manufacturers' recommendations and found that Michelin seem to be the only ones who quote two options, 33/36psi solo and 36/42 fully loaded. There were no lower pressure options mentioned, so we have to assume that 33/36 is considered to be the minimum.
Nonetheless, I shall monitor my pressures cold and hot, using the 10% rule. I should be grateful really - with only 'flyweight-me' on board the bike accelerates like stink. I just hope that I have a big enough footprint gripping the road to make it stop and turn!
