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Tyres tyres tyres

Discussion in 'Technical and Troubleshooting Torque' started by Mike9999, Oct 25, 2011.

  1. Ok, so a few questions regarding my Ninja 250R (09).

    First, background: Took it down to race replica over in brooklyn today to see if I needed a new front. I've had the stock IRC Roadwinner front on and the bike has now done 16,700kms - apparently still had around 2000kms left in it but seeing as I plan to significantly shift my riding style over the summer I've decided to fit a new front (Dunlop GT501). I have read good things about these, but they are a very soft tyre so I don't expect to get as many kms out of them. On the rear I have a Michelin Pilot Sporty fitted about 4000kms ago.

    Question 1 - is it ok to have two different tyres on? I understand that they are both radials.

    Question 2 - upon inspecting my rear, a guy from race replica commented on its "scalloping" ie: one lip of the tread was wearing down while the other lip looked lifted. He also commented on some cracks in the tyre along the sides (not the centre). I had noticed these but did not think much of them...he put this down to having too low a tyre pressure, and suggested 38/38 psi!! I usually run 28/32 (front/back) as per the bike's manual. Has anyone else experienced this?

    Question 3 - If so, is it a problem that I can remedy by raising tyre pressure?

    As a side note, when I say change riding style I mean I will be hitting the twisties more often, with less commuting as uni will be over. I'm close to the limit of lean when I ride like this as I sc**** the pegs every now and then, so I really need to have some confidence in the tyres and figure out anything wrong!


  2. 28/32 is too low a pressure, i reckon 36/36 is a good start.
  3. my hornet I had been running 36/42 then was told the new Pilot3 will be good at 38[rear]
  4. Alright, cheers for the input peeps, will increase psi tomorrow.
    Side note: electronic servo pressure machines - reliable or not?
  5. not really at all, and you really should be monitoring your pressures when the tyre is cold (for starters), not when its hot.
  6. Well the servo is about 1 minute from my house so they're not hot, but wont be using them anymore, i had a feeling they werent accurate....time to go to supercheap
  7. Servo gauges are unreliable pieces of shit and unless you use the same one everytime who knows what reading you are getting.

    I carry a small $10 telescopic one in my jacket and also have an air compressor with gauge i got at an auto shop for $70.
    The telescopic gauge matches the compressor.

    So basically i can walk out, check my tyres, if i need air i can plug the compressor into the bike battery and pump em up. This way I don't have to ride lacking confidence in my tyre pressure and they are checked when cold.
    • Like Like x 1
  8. Yeap we've got a compressor just need to grab a small gauge that I can quickly use like your $10 one.
    Damn if only i knew this earlier, major newb fail
  9. any quto shop has the small silver telescopic ones, just leave it in your jacket.

    example of servo gauges, there is about a 7psi difference between the one at the BP where the saturday sessions are and the servo down on the bend of beach rd and st kilda st.
  10. well in the damp conditions on the way home yesterday found bike not 'behaving' as normal, in at 7 eleven, always go to the same place, so if gauge is out, at least always consistant. front was 31, rear 34, as i said normally 36/38 so front was shite to steer, wanted to turn itself.. pumped up and all good as gold
  11. Small changes in tyre pressure, especially when the tyres are a bit worn, can have a very large impact on how the bike steers and behaves.

    Get your own tyre gage and check them with that, cold, before you head off, and do it often.

    I don't quite follow my own advice on this. The local servo where I buy fuel has a digital beep machine, and I've made the arbitary call that it's accurate - so I always use it. I check every time I buy fuel.

    Too hard in the front and the bike will want to lean over all by itself - and the ride at the front will get kind-a bouncy. Too soft and it will stand up, and you'll need to apply a constant steering pressure to the inside bar while turning, just to hold it down. When it's right, you should be able to bring the bike to a lean angle, and then do nothing - just lightly hold the bars without pushing or twisting them in any way, and the bike should more or less stay at the angle you put it on. So, if you're riding and you notice that the bike seems to be getting a bit heavy in the steering, and you need to hold it down - you very likely have a leak in the front.

    When you feel that handling or steering or balance of the bike change - the first thing you do is check your tyre pressures.

    I don't know what the correct tyre pressures for a 250 Ninja are. I would have guessed about 34 in both. Read the owner's manual - set them as the book says, and see how that feels. Now add or subtract a little based on the stand up / fall down principle. When you have it handling the way you like - note the pressures. Those are the pressures you need to maintain.

    Once the tyres get to about 50% worn, there will be a gradually increasing amount of stand-up due to the changed profile shape. That can't really be helped. If adjusting and tuning your handling with the tyre pressure doesn't fix it by the time you're 6 ~ 8 psi higher than your original base setting, then it isn't going to. Go back to your base setting and deal with it, until you can change the tyres. It won't be real bad or real noticeable at first, but the more they wear, the more they'll stand up. You should also note that dry weather grip will begin to suffer a little by then, and wet weather grip quite a lot. If the bike isn't handling the way you remember, and the tyres are worn - change them.
    • Like Like x 2
  12. Don't know why your manual makes a suggestion anyway, the tyre pressure should be matched to the tyre you're riding with, and the type of road you're riding on.
  13. Well, today I bought myself a small digital pressure gauge from Autobarn. So far it has been very consistent with its readings. Went to a nearby servo and, comparing its measurements with my small gauge, put the tyres up to 36psi each.

    Some immediate differences:
    -ride has become very bumpy!
    -bike feels a little more planted in the corners
    -takes more throttle/effort to get the bike to stand up out of the corner
    -felt alot easier to turn in
    -sooooooo bumpy............

    Will play around with it tomorrow, might turn it down a notch and see if its a little more comfortable.
  14. The manual tyre pressures will be matched to the OEM tyres. A 250 might have lower pressures than a big bike as well. I know my old hyo 250 used to run the same as youre ninja, whereas the 600 runs 36/42.
  15. Well the rear, and the soon to be front, will be a much softer tyre than the stock tyres, so I assume that would mean an increase in pressure is needed?

    I think that is why it is so damn bumpy, because the front is still the stock, and very hard, IRC roadwinner, which ive got to 36psi now. Ill drop it back down and wait until I get the new front to experiment with higher pressures.
  16. The official Kawasaki workshop manual says 28/32. Running 36/36 is way too much for the front. Try 32/36 but I wouldnt go much higher than this to be honest.

    PS: Dunlop 501's are shit in cold and wet conditions.

    PPS: just my 2c worth.
  17. This relates to the rubber mixture. That's distinct from the stiffness of the carcass or body of the tyre, which in turn, is distinct from the tyre pressure.

    It's entirely possible that different tyres will need different pressures, that's correct. But a 'softer' tyre with more grip could have an entirely different profile, carcass construction, and run best at a completely different pressure.

    Michelin sports tyres, the Power Pure in particular, have quite a soft, thin, lightweight carcass. They do need a bit more air pressure in them, compared to most tyres. Some of the track-day Pirrelli tyres have a very stiff carcass. They have a very soft and grippy rubber compound, but they don't need a lot of air in them. The (racing) Dunlop N-tec is even more so. They race them in 1000cc superstock and superbike at 18 ~ 22 psi.
  18. do what he says
  19. no, it's because they are overinflated and you have shit suspension.
  20. Yeap I'm definitely going to drop the front down. Thanks for the heads up E2W, will have to be extra careful in cold/wet.

    I've opened pandora's box I see. I guess I can just fiddle around with the pressures until I get a nice set of values for my tyres and riding, but that just sounds like guesswork to me...will have to do some research into tyre pressures and different tyres on the interwebz.