bigblock Posted August 20, 2009 Share Posted August 20, 2009 Hey all, Question for the pundits to consider - Last night while riding on the freeway at about 95-105mph ( ) I noticed a significant vibration coming up from the front end through the bars... The bike has 23k miles and I just had a new Michelin Pilot Power installed about 500 miles ago (tire pressure is 40psi)... would like some guesses as to the cause - I thought of the tire first... At lower speeds (closer to the speed limit) the vibration is gone. any guesses? has this happened to anyone else? thanks Rick Quote Link to comment Share on other sites More sharing options...
Fiona Posted August 20, 2009 Share Posted August 20, 2009 You're not going fast enough Tire pressure too high perhaps. Not head bearing... would get a wobble/shudder. Probably same if the wheel wasn't properly balanced. Quote Link to comment Share on other sites More sharing options...
rockmeupto125 Posted August 20, 2009 Share Posted August 20, 2009 Needs balancing. You can have a crappy balance and get away with it up to about 85-90....then it really starts to become apparent. Quote Link to comment Share on other sites More sharing options...
cyoungesq Posted August 20, 2009 Share Posted August 20, 2009 I have had the EXACT issue - a vibration between @ 85 & 110 that really rattles the bars, gagues and the mirrors. Turns out that it was most likely a balancing issue due to improper balancing of new front tire and banged-up front rim. Just got new tire on new wheel, balanced, new bearings & putting it on tonight & am expecting that to be the end of it. No sign that the steering/head bearings are shot. Quote Link to comment Share on other sites More sharing options...
xrated Posted August 21, 2009 Share Posted August 21, 2009 Sounds like a balance issue, since you just developed it after the front tire was replaced. Also, lower your front tire pressure down to about 32 - 33 psi unless you are like 450 lbs or something!! Quote Link to comment Share on other sites More sharing options...
blackhawkxx Posted August 21, 2009 Share Posted August 21, 2009 Also, lower your front tire pressure down to about 32 - 33 psi unless you are like 450 lbs or something!! 32 psi is too low for normal riding IMHO. On the track it might be fine but with every day riding, you are creating more heat, more wear and less mpg. Quote Link to comment Share on other sites More sharing options...
cbrxxquad Posted August 21, 2009 Share Posted August 21, 2009 I finally heard something that made sense about tire pressures on the bike when someone here said that you know your tire pressure is correct when your pressure rises 10% while riding, from cold to hot. street and racing is covered in this, as well as the conditions, and type of tire. Quote Link to comment Share on other sites More sharing options...
cyoungesq Posted August 21, 2009 Share Posted August 21, 2009 new wheel, tire, bearings, & big improvement ... BUT, still a pulsing slight vibration from about 90 to 115. Pulsing as in 1 second of vibration, 1 second of smooth, etc... Starting to think maybe a warped rotor. What else could it be? Quote Link to comment Share on other sites More sharing options...
xrated Posted August 21, 2009 Share Posted August 21, 2009 blackhawkxx wrote: 32 psi is too low for normal riding IMHO. On the track it might be fine but with every day riding, you are creating more heat, more wear and less mpg. That is your opinion. I run the Pilot Power 2 CTs and my wife runs the plain Pilot Powers on her bike. Street riding is as follows: Front: 31 Rear: 30 Trackdays.........Front 29 - 30 Rear 26 psi These are cold pressures and the tires usually come up 4 to 5 psi during a trackday I have ALWAYS felt that I would rather have a properly inflated tire....i.e. tire will heat up properly and provide the stick/traction that you need, than to be over-inflated and not let the tire warm up properly and risk losing traction in a corner. I guess if all you do on the bike is commute or you never lean the bike over in corners, run the pressure up to 42 psi and have at it. You will certainly get better mileage, longer wear and a tire that won't stick in a corner. Quote Link to comment Share on other sites More sharing options...
jon haney Posted August 21, 2009 Share Posted August 21, 2009 Also, lower your front tire pressure down to about 32 - 33 psi unless you are like 450 lbs or something!! 32 psi is too low for normal riding IMHO. On the track it might be fine but with every day riding, you are creating more heat, more wear and less mpg. +1 Run 40 psi in the rear and 38 psi in the front, no problems with traction on the street, but then again, I don't lean near as far over as I will at the track. Another thing to consider for street riding is that the less air pressure you run, the more likely you are to bend a rim if you hit a deep pot hole. :icon_think: Quote Link to comment Share on other sites More sharing options...
jon haney Posted August 21, 2009 Share Posted August 21, 2009 new wheel, tire, bearings, & big improvement ... BUT, still a pulsing slight vibration from about 90 to 115. Pulsing as in 1 second of vibration, 1 second of smooth, etc... Starting to think maybe a warped rotor. What else could it be? It's still a balance problem. The frequency of the vibration is not quite in sync with the resonance frequency of your forks. At some speed they will synchronize and it will really vibrate like Hell. Quote Link to comment Share on other sites More sharing options...
Redbird Posted August 22, 2009 Share Posted August 22, 2009 I have ALWAYS felt that I would rather have a properly inflated tire....i.e. tire will heat up properly and provide the stick/traction that you need, than to be over-inflated and not let the tire warm up properly and risk losing traction in a corner. I guess if all you do on the bike is commute or you never lean the bike over in corners, run the pressure up to 42 psi and have at it. You will certainly get better mileage, longer wear and a tire that won't stick in a corner. Sorry, Vern, but I disagree. I never went lower than 34/36 on the XX tires on the street and had no issues dragging pegs at as much as 38/40 psi. If it gives you peace of mind to run them that low, rock on, but street tires heat up and stick just fine at pressures considerably higher than 32psi. Quote Link to comment Share on other sites More sharing options...
EVLXX Posted August 22, 2009 Share Posted August 22, 2009 I finally heard something that made sense about tire pressures on the bike when someone here said that you know your tire pressure is correct when your pressure rises 10% while riding, from cold to hot. street and racing is covered in this, as well as the conditions, and type of tire. Yes, and more than a 10% increase means your tire pressure is to low, and much less than 10% means your tire pressure is too high. The 10% increase is due because of the Heat gain of the tire, so basically what this is really telling you is, whether or not your getting your tires to the proper temp. I should also note, that in order to get a proper reading, one must carry a tire pressure gauge, and take the temp relatively quickly after stopping, while in the middle of your ride somewhere safe. Quote Link to comment Share on other sites More sharing options...
bigblock Posted August 22, 2009 Author Share Posted August 22, 2009 Thanks for the responses gang... I had a suspicion that it might be the balancing or perhaps the wheel bearings... I was worried that you were all going to say steering head bearings... I run a higher tire pressure because I find it has better traction for the road riding I do (commuting etc) but I will consider dropping it a bit... thanks again... Quote Link to comment Share on other sites More sharing options...
cyoungesq Posted September 6, 2009 Share Posted September 6, 2009 for me, turns out it was a warped front brake disc/rotor. Just put on new ones and the vibration is gone. Must've been just slightly warped ... no brake pulsing at all. First did balancing, then new tire/rim with new bearings. Helped, but did not resolve. New rotors did the trick .... now no vibration at all. Quote Link to comment Share on other sites More sharing options...
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