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better directional stability?

Discussion in 'Technical and Troubleshooting Torque' started by garryspam, Mar 27, 2011.

  1. Hi,
    I am a noob to bikes and to riding, just got my L plates and a Yamaha SRX 250. I have done about 300 kms in town and did my first out of town trip today. I found that my directional stability was a little dodgy, in comparison to the other riders I was with, they were able to see my instability through divits in the road.
    Nothing too serious, not the actual death wobbles, but at least once, I had myself wondering if I was going to come off as a result. Basically it felt like my tyres were being stuck in the creases in the road.
    I have standard 3 spoke rims with good tyres. The bike is in good order with 38000 original kms on it, I have had it inspected and am told that the suspension is in working order.
    Is there a caster angle setting on bikes? is there a way to get better stability via adjustment? Or is this a mix between the nature of my bike and my inexperience?
    Cheers for any help on this matter.

  2. This seems to be tricky one, and though I'm not a mechanic, I suspect it may be a loose(or stuck ball bearings due to dried out grease)bearings in the steering. But it's a long shot.
  3. Although you say they are good tyres check them first:
    Check your tyre pressures.
    What brand and model tyres do you have on the bike?
    How old are they?

    Generally most beginners have the wobbles. As your experience grows your balance and bike handling improves. Make sure you are looking out where you want to go not close in to the road near the bike.

    Where about are you? Can you make it to the Melbourne or Sydney beginners practice sessions?

    PS: WobbyDoinkBoink makes a good point, Headstem bearings are often the culprit but they should have been checked with your inspection. It is a standard check that a mechanic will do. One to keep in mind though.

  4. Front: Dunlop ArrowMax GT 301F 100/80 - 16
    Rear: Metzeller ME22

    I should check the tyre pressures, will do that. The tyres look good, they are evenly worn with little overall wear, nothing abnormal to my eye.

    In Wagga Wagga, cant make Syd or Melbs for practice sessions. Around here, most of our roads are pretty "squished up" by big vehicles tyres shaping them over time. I do get the general wobbles somtimes and can see that its my skill level at fault, this however felt like the bike was being handled by the road pretty savagely, in comparison to other 250's that I was riding with. Keeping away from the divits is the immediate goal... but sometinmes it is chosing the best of a bad bunch of road issues to ride through.

    Wheel bearings, is it the same as with a car? If I raise the front end, will I feel side play in the front wheel? Loose bearings would account for a feeling like this, but I have no other issues/noise/wobbles unless going through road divits at 80kph kind of speed.


  5. As per Chris's suggestion, check tyre pressure to be correct first. It affects bikes far more than cars. If this fixes your problem, then probably then don't have to see a mechanic.
  6. Just checked with static checker... .SERIOUSLY under inflated tyres! Will pump up tomorrow, road test and post update.
    Front 15psi
    Rear 15psi

    I would have thaught at that level, I would notice other issues on the road in town! Cant wait to ride with full pressures!


  7. Holy crap. What are they supposed to be?
  8. Mate,
    At those psi's I'd be swaying side to side like Happy Feet myself !!!!

    Most tyres recommend 36psi front, 42 psi rear, though for road riding these settings will be very 'bouncy' and not necessarily favourable.
    I like to ride with ~ 33-34 front, ~36-38 rear. With tyre warming (temperature is directly proportional to pressure), your psi's will increase, hence Wobbly's sound advice below.

    No doubt, a great post now to serve as a reminder to check tyre pressures regularly bud.
  9. for 250cc without pillion, 32psi both for front and rear should be adquate, or consult manual, or writings on the tire wall, but never inflate max psi.
  10. I'd say 32 f + r. I'd also say that tyres age by the calendar as well as the distance. I'd also say it's nice if the front and the rear are made by the same company, even if they're not a matching set. A matching set would be best - ie., Arrowmax F + R.

    It would not hurt to check your tyre pressures every 48 ~ 72 hours. Car tyres generally hold their pressure indefinitely unless there's something wrong with them, but bike tyres are often a bit porous. Oddly, it's often the best tyres that leak a little.

    It would not be a real bad idea to get a bike mechanic or an old salt to go over the bike for 30 ~ 45 minutes and look at things like wheel bearings, wheel balance, steering head and swing arm bearings, suspension function and setup...

    I don't know whether you'd know this or not, but ... A properly functioning motorcycle will lean in or stand up in response to rider input through the handlebars (counter-steering) and otherwise stay at the lean angle it was at. If the bike pops up in the middle of the corner, or you need to use constant counter-steering to hold it down into the corner, something isn't right. If it wiggles and wallows around like an epileptic on a waterbed - something isn't right. If it tips in quickly and easily to one side, and hates to go the other way - something isn't right. If it punches your backside out of the seat every time you go over a cat's-eye - something isn't right. If you can hear a characteristic noise like a clunk or a clonk or a tinkle every time you go over a short, sharp bump, something isn't right.

    Within limits, you can adjust how your bike feels and handles by changing the tyre pressures. If the bike seems to be standing up too much, try increasing them a bit. Use 2 psi increments and have a test ride, around some corners and covering about 10km at least, before you decide you don't like it. Smaller bikes on road tyres generally seem to need something around 26 ~ 32 in the front. Bigger bikes need more. Most 1,000cc sports bikes have recommended pressures on the road of 36F and 42R. Owners of big touring / sports-touring bikes sometimes run 42+ in both. My mate with the FJR13 runs 42 cold in both. The factory recommended pressure in my ZX14 is 42 on both. I run 45 cold in both. That's border-line, you really shouldn't pump them up that hard, but it keeps the bike on the line I choose.

    Track day junkies and really fast road riders sometimes use tyres deliberately soft, to help heat the tyre and get it in its optimum temperature range for maximum grip, even if that results in slightly wonky handling. They're not shy about advising others to do the same. If you go to the track a lot, and you're dragging your knee and want to know how to go faster, listen to them. Otherwise...

    A final thought. 16" fronts were a fashion that came and went. Part of the 'went' reason is that they're a bit wobbly. 17" tyres have the same rolling diameter, but they usually work a lot better. The choice of good tyres in 16" is very limited. There are many more options in the 17" size.

    The last time I rode a Dunlop Arrowmax was in 1983 ~ 84, on an 1100 Suzuki, and I liked it a lot. I have never used a 16" version, and the one they make today is probably quite different, but my intuition tells me an Arrowmax is a good general purpose tyre, with reasonable grip and handling and life expectancy. My recollection of ME99s is that they're as hard as nails and last for ever. They're a fairly high quality tyre and have reasonable stability and handling, but they don't grip real well, and when they do let go - they go all the way. To my certain knowledge, ME99s have been in production since at least 1978, and even then, they were designed for big bikes - 750cc, 240+ kg. How one of those ended up on the back of your ... small bike, is a small mystery to me.

    I would look at changing both your tyres over the next 6 months. I would look to fitting a matching set, same manufacturer, same model, of recent tyres, (ie., tyres that were not designed or made over ten years ago) and do it on the same day. Ask your tyre fitter what pressure he set them to, and then go and check it on the pressure gauge you normally use.
  11. Very informative kneedragon, think we should also have your post on a new thread for tyres.
  12. Hi, I also have an SRX and have changed both tyres, and go 30 F an 38 back. I am +- 100 kgs, and it seems to handle well at that in both wet and dry..

    I had 1 srx wich got stolen and trashed, so I got another one.. and built one out of two..
    since they are like 25 years old, make sure the back wheel is centered ,i put a lot of k,s on mine, and it pays to keeep and eye on it, checking it regularly. The bolts are old, and the bikes rattle a bit, you will be amazed to feel the difference a couple of turns of the spanner makes!!

    The srx is a great little bike, good for learning, commuting, etc. It should be light and take corners really well, as you get confident, and on the right surface, you can really flick it and go quite low..

    Good luck, and be careful!!
  13. urgh no. Metzeler front and rear
  14. You mentioned divits.

    I bike will feel like it's trapped by and will track along uncomfortably in "furrows" caused by big trucks. That's normal, but it's best to avoid them.

    15psi is too low. Your bike would have handled like a dog.
  15. Thanks for all the helpful info everyone, I adjusted the pressures up to 32 front and rear as a starting point. What a difference!!! Even in town, the bike is a completely different bike to ride! I need to be careful now, as I have been used to wrestling this thing in and out of corners with a lot of might, now it actually responds willingly to slight shifts in my weight. I took it for a short trip out of town to test in the original conditions relating to this post, the ride was much less hair raising to say the least.


  16. Benny, what does that actually mean? Do you appreciate "countersteering"?
  17. You could be gripping the bars too tight. And how are your arms ?? relaxed, bent. Are you using your stomach muscles to hold you up not your arms.
    Just keep a nice even pressure behind the bars and let your elbows become part of the suspension.
  18. Hmm, not sure if I appreciate counter steering... not familiar with the jargon. What I mean is prior to having appropriate tyre pressures, I found that the bike was reluctant to turn, I was finishing wide and felt like I was using a lot of body power just to finish at all. I did not realise that this was not normal. Now I am able to turn and keep a nice line, with minimal shift of weight. My comment realtes to the fact that if I was to corner now, in the fashion I did with low pressures... I would end up horizontal.


  19. But you don't need to shift weight to turn a bike.

    When you get a bike to steer/turn/change direction, what do you do?
  20. Hmm, I will consciously observe myself riding home today... but after googling counter steering ,I think you are correct, I am (unwittingly) countersteering. Not sure about your original question about appreciating it... I certainly enjoy it better with the tyres pumped up anyway.