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Message started by groupus on 07/04/10 at 12:06:27

Title: Speed Wobbles
Post by groupus on 07/04/10 at 12:06:27

i just seemed to have developed some pretty nasty speed wobbles that start at about 75-75mph. any insight on this? its freakin' scary and potentially dangerous. also, i put new tires on months ago, but this hasn't happened til now.

Title: Re: Speed Wobbles
Post by justin_o_guy2 on 07/04/10 at 12:15:45

Checked tire pressures? Inspected them? Held front brake & rocked the bike to feel for looseness in head bearings?
Mine gets to riding like a rubber cow in corners, but is straight & true on a sraight shot.

Title: Re: Speed Wobbles
Post by verslagen1 on 07/04/10 at 12:24:56

Uneven road or rain grooves?

Do you have a fork brace?

Title: Re: Speed Wobbles
Post by Phelonius on 07/04/10 at 13:46:21

Most likely cause is steering head bearings need adjustment.
Block up the front of the bike and adjust the bearings by tightening them until the front does not free fall to either side. It should still fall to either side but not fast, there must be a SLIGHT resistance.

Phelonius
BTW A tank slapper can kill you.

Title: Re: Speed Wobbles
Post by Oldfeller on 07/04/10 at 14:05:56

Do your handlebars sit slightly "crooked" when you are going down the road in a straight line?

If so, this can indicate that your rear wheel is cocked off to the side (the marks on the axle are notoriously inaccurate) and this can contribute to a harmonic "wobble" that is rear wheel driven. To correct, move the rear wheel as if you were correcting the error shown in your "crooked" handlebars.

Another test to perform -- when the wobble begins lean forward and shift your center of mass (combined mass, you and the bike) forward a bit. If the wobble immediately begins to stop you may well have a rear wheel related issue. Have your wheels been balanced and TRUED (spoke tuned) lately?

Next test, when the wobble begins steer the bike to the smooth hump in the dead center of the road -- this removes the "rut groove" that exists in most tarmac roads from playing against your bike's natural harmonics.

I have become a bit of an expert in fighting them evil wobbles since I got my bike smacked in the rear tire by a truck in a parking lot ...

Title: Re: Speed Wobbles
Post by groupus on 07/04/10 at 18:19:43

checked the tires and pressure today, also checked the head bearings via justin's shake method. all good but still has the wobbles. i don't have a fork brace, it never did this before. handle bars look fine too. i'm ruling out grooves and road surface because it does it pretty consistently at speed on many different roads. tried shifting weight forward, back, left, and right to no avail. wheels were balanced when i got the new tires, but never trued as long as i've had it (has almost 16k).

surprisingly, the wobbles seem to stop, or at least greatly reduce when i take my left hand off the bars. figure that one out. i'm going to tighten the head anyway cause it does like to flop to one side when i park, and i'll at least have a look at the rear. do you need a special tool to tighten the head?

That being said, thanks so much for the help. i know that speed wobbles or "death wobbles" are extremely dangerous. hasn't turned into a tank slapper yet, but at least i can stop them by slowing down. more updates to follow.

Title: Re: Speed Wobbles
Post by verslagen1 on 07/04/10 at 23:33:44

To tighten the head bearings you don't need a special tool, a screwdriver will do. I think I tightened mine hand tight only using the screwdriver to over come a sticky spot.

for our reference, what tire do you have?
how much tread?
even wear?

Title: Re: Speed Wobbles
Post by thumperclone on 07/05/10 at 00:25:58

new tires..
were they balanced/
did you throw a weight/
are spokes tight

Title: Re: Speed Wobbles
Post by Charon on 07/05/10 at 07:08:32

How many miles on those "new" tires? You said you put them on "months ago." If you have put a few thousand miles on them they aren't new any longer. And don't forget to check the rear tire, too. Both tires the same brand and type (radial/bias)? There have been reports (though I've not seen any on this forum) that some combinations of tires can cause odd problems. Do you have a windshield? If so, check its hardware. If not, it is just conceivable your grip on the bars fighting the wind may be the problem - the hint being that the wobble reduces when you remove your left hand from the bars. Try leaning forward to counter the wind (difficult on a cruiser), so you are not pulling back on the bars.

Edited to add: You might also check the swing arm bearings. That probably involves lifting the rear and attempting to feel for any play in the swingarm. At least on the 250 Ninja, the swing arm bearings are supposed to be greased every 6000 miles, and greasing them calls for disassembly.

Title: Re: Speed Wobbles
Post by Bubba on 07/06/10 at 07:13:35

Had both my wheels trued when my new tires were put on...didn't really want to (cuz it was more than I wanted to spend) but I had suspected the front anyway because of some brake rubbing. I trust the place I went and they true them to 2/1000's of an inch (round, dish and lateral). I don't think it had probably ever been done.

Anyway, I was getting a "light" front end wobble when I was going hiway speeds...now I don't.

Title: Re: Speed Wobbles
Post by Phelonius on 07/06/10 at 09:25:38

14373F3D3E37373E295B0 wrote:

That's just one of the ways them trucks will try to kill you.

Phelonius

Title: Re: Speed Wobbles
Post by groupus on 07/06/10 at 14:11:12

ok, so the tires probably have 3000 miles on them, but both look to have even tread wear. Avon Venom front, Dunlop 404 rear. i did adjust the back wheel alignment but haven't tested it yet. i can't get the steering head any tighter, do i have to jack up the front end for that or loosen the crown nut first? I tapped on each of the spokes with a wrench and listen to the tone to check tightness (tighter have a higher tone, looser a lower). there was some variation in tone, but not much. I'll try jacking the front and rear up and spin them it see if there is any noticeable deflection, as well as check the swing arm and head for additional free play.
no windshield by the way..

interestingly enough, my friend with a xs650 is having issues with a wobble under heavy acceleration. his definitely seems to originate from the rear, while mine seems isolated to the front.

ps. any idea how much it costs to true a wheel, those who have done it?

Title: Re: Speed Wobbles
Post by justin_o_guy2 on 07/06/10 at 19:07:25

You can true a wheel, Just takes some time & patience & a bit of ingenuity. I wont type the methiod, cuz that would take a typist like me about as long as truing the wheel. I guess it would require some ability to assemble tools from junk, which I can do.

Title: Re: Speed Wobbles
Post by WD on 07/06/10 at 19:33:22

You just answered your own issue. D404 is a hard tire, Venom is very soft. I had a Bridgestone front and Cheng Shin rear on my Vulcan 800 Classic. Rode fine straight at low speeds (35-45 mph). In a turn at 20 mph, the headset locked. Broken shoulder, 12 pins, a plate and 2 years later I could ride my Savage. Vulcan, as far as I was concerned, was a total loss. Once the headset gets locked and that is enhanced by a crash, the frame is junk.

Don't waste money on Avons, get yourself another 404 and you should be good to go.

Title: Re: Speed Wobbles
Post by mpescatori on 07/07/10 at 05:35:02

4A5D485D405A5F2F0 wrote:

I had the same on my trusty old Moto Guzzi V50, the front fork stems had worn and the oil/compressed gas in the individual stems were at different levels.
In other words, the two stems of the front fork had different stiffness, so any time you bump into anything bigger than an ANT the front fork will twist and the wheel will wobble.

Else, I have Avon Venom front/rear, have ridden a mere 5000 miles in 4 years (been stationary far too long) BUT they are excellent value for money (IMHO)
because they are high performance tires for high-performance bikes (100++bhp), fit them on a 30bhp bike and they should last a long time and a half. :)
My tires look like new, and hold the air pressure quite nicely.

PS small tip for that rear tire air valve, I bought an "L" adapter from British supplier called "Holden"
http://www.holden.co.uk/getImage2008.asp?path=e%3A%5Cdomains%5Choldenvc%5Cwww%5Cproductimages%5C094%5F949%2Ejpg&WorH=w&max=300
cost GBP 3.95+VAT = US$ 8 more or less

http://www.holden.co.uk/default.asp?mode=bike

but now checking for air isn't the pain it used to be !

Title: Re: Speed Wobbles
Post by cursal on 07/07/10 at 07:56:16

some tubes have that L shaped stem already mounted on them.

I agree that makes checking and adjusting tire pressure very easy. +1

Perfect if your doing lots of solo and 2up riding.

Title: Re: Speed Wobbles
Post by bill67 on 07/07/10 at 08:11:57

My V50 moto guzzi had small shocks in the fork,2 oz. of oil only for lube in the forks.

Title: Re: Speed Wobbles
Post by groupus on 07/07/10 at 13:44:40

hey, thanks for all the replies and help. i jacked the bike up last night and spun the front tire. bad news: there is a noticeable movement side to side. good news: this may be the culprit. so i'll have to get it trued and see where to go from there. i've trued bicycle rims before, but i don't think i want to do it on the Savage. I looked up how to do a motorcycle wheel and i would need to buy more tools, and stands, and dial indicators than would make it worth it. hopefully this will cure it and won't cost me too much.

WD, i'm not sure how a hard and soft tire combo, or really any combo, would cause the headset to lock up... might cause it to ride funny :-? but, then again, you're the one with the scars to prove it.

Title: Re: Speed Wobbles
Post by justin_o_guy2 on 07/07/10 at 15:13:23

No dial indicator needed. A wire poking out of a block of wood to set-up right by the rim will let you see the direction & amount of variation from true. You can build a stand, not hard.

Title: Re: Speed Wobbles
Post by groupus on 07/09/10 at 14:51:10

i went ahead and took the tire to a shop to true it. $35 to true and $25 to dismount and remount the tire. not bad, seeing as how everyone else wanted $70 per hour :o. thought about doing it myself, but i don't have any of the equipment to do it, not to mention any bead breakers or tire irons. i know i could build the stuff for cheaper, but i have an apartment so i can't really keep that sort of stuff in a garage or anything. whatever, these guys do dirt bike rims all the time so i trust them with something that could potentially kill me :P
i'll take it on the highway this weekend; hour and a half to where my parents live for gettysburg bike week. we'll see if truing solved the problem. i'm gonna harass the sh!t out of some harley riders this weekend haha. i hope i see some other savages there too! ;D

Title: Re: Speed Wobbles
Post by justin_o_guy2 on 07/09/10 at 14:58:55

but i have an apartment

That does make a difference, fo sho

Title: Re: Speed Wobbles
Post by PhilM on 07/09/10 at 16:13:35

041306130E1411610 wrote:

surprisingly, the wobbles seem to stop, or at least greatly reduce when i take my left hand off the bars. figure that one out

Gripping the bars too tightly can cause a slight wobble to develop and then increase. The grip causes a feedback loop, the more effort you put into stopping the wobble will actually make it worse.

Title: Re: Speed Wobbles
Post by verslagen1 on 07/09/10 at 18:43:41

I had a sticky head bearing that didn't wobble, but made it hard to drive a straight line.

Title: Re: Speed Wobbles
Post by groupus on 07/12/10 at 11:51:05

truing didn't do anything >:(. best solution now is to slow down or ride with one hand. i've gone over the head bearing, front rim, rear wheel alignment and pressure, and weight distribution. only thing i can figure is its the tires??? so if the problem is the difference between the sticky avon front and the harder dunlop rear, what type of tires could i replace the rear with, other than another avon, that would have the same kind of rubber compound? (rear will wear out before the front)

Title: Re: Speed Wobbles
Post by justin_o_guy2 on 07/12/10 at 11:56:08

How fast are you going when it starts?
Is the front tire seated fullly on the rim? Look carefully at the line that runs next to the bead & make sure its the same distance from the rim, all the way around on both sides.
Do you have a fork brace?
How does it handle in a long sweeper?
What setting are the rear shocks set on. Look at them, make sure they are the same & Id set them on the firmest ride possible, because when the rear end goes up & down, the rake angle changes a bit. When mine starts wobbling in a sweeper, I can feel the rear end going up & down. Yes, there set as tight as I can get them..

Look for a stretch of good, smooth road & see if it acts different there.

Title: Re: Speed Wobbles
Post by groupus on 07/12/10 at 12:17:00

at about 70 is where it starts and as i accelerate, it gets more intense. it doesnt always do it, but at those speeds it is provoked into a wobble much more easily and doesn't want to stop. at lower speeds i can start a wobble by shaking it, but it'll return to straight.
as far as seated properly, i can see the edge of the whitewall vary distance from the rim as it spins. is this something i should talk to the guys who trued the wheel about because they had to remove and remount and balance the tire when they were done? but theres no difference between now and before they fooled with the thing... so maybe thats not where the issue is, unless they remounted it in exactly the same way as before. :-/

Title: Re: Speed Wobbles
Post by verslagen1 on 07/12/10 at 13:43:28

maybe a bad tire.
one tire I mounted myself didn't seat completely till the second time too.

Title: Re: Speed Wobbles
Post by WD on 07/12/10 at 18:19:07

The whitewall section is going to have some color break waviness. That's normal, the bead edge doesn't get much attention.

Go out to your bike, kneel at the front tire, close your eyes, and "feel up" the front tire like your prom date. Any high spots, low spots, side to side peaks or edges?. Do the same to the back tire.

Deflate the tires and roll the bead just enough to see if the wire has taken a "set", or kink. No need to pull them for that check, your thumb will move the sidewall in enough. Go all the way around both tires, both sides, using a good light source.

Get on the manufacturers' websites and send them the coding from the sidewalls. Not the size code, the tiny printing that will tell them when the tire was made and at which plant. Bike tires do have a shelf life, just because they are new to you does not mean they are fresh tires. No telling how long they were on the shop shelf or how long they were at Parts Unlimited or whatever distributor the shop orders from. Or, for that matter, how long they sat in the importer's warehouse once they were offloaded from an intermodal container after coming across the Pacific.

I've been doing this since 1987, including several stints in independent bike shops. I've only ever had one bad Dunlop tire, and it was a D402 Harley tire, 80/90/21 mounted on a VN800A Kawasaki.

I'm betting your Avon has a bad section of body cord or a kinked bead. We sent dozens of Avons back at the last shop I worked for, defective bead wires and or bad carcass lay up. I'll run a Speedmaster, but you couldn't pay me enough to run a Venom.

Title: Re: Speed Wobbles
Post by mpescatori on 07/14/10 at 02:47:38

0516520 wrote:

I have Avon Venom both front and rear, and I ride quite comfortably on tarmac, broken tarmac, cobblestone, broken tarmac, and any other kind of poorly maintained hard surface you can think of.

The tires now have about 11.000 Km on them, that's about 7000 miles.
They offer excellent grip, I can actually steer through throttle going up highway ramps, and in Italy these ramps are both tight and steep (like on multi-story car parks) the only time I feel uncomfortable is in the rain - but then the Venom is a semi-slick...

http://www.totalmotorcycle.com/photos/tire-tyre-guide/Avon-VenomAM41andAM42.jpg

The day I will have to change my tires, I might well buy a new set of Venoms (because I'll have got used to their response) or go for something more "rainy" and more touristic-oriented

These, for example, are the PIRELLI Mandrake, as I had fitted to my old Moto Guzzi; not as performing as the Avons, perhaps, but they got me through many years of riding safely in the rain...

http://www.motorradreifen-guenstig.de/portal/system/images/PIRMT15.jpg

8-)

Title: Re: Speed Wobbles
Post by groupus on 07/14/10 at 12:22:57

i've felt that front tire up like a... well nevermind, but it seems legit. no bumps, bulges, tears, nicks, waviness, or other deformations. bead looks seated all the way around too. have not checked the year date though - keep forgetting to write down the numbers.
my verdict for now is that there is "something" unkosher going on with one or both of the tires. although it feels like its coming from the front, i did have problems before with the rear being oversized. i hate to leave it at that with a potentially dangerous problem like this. i paid good money for those tires that have less than 3000 miles, and i'm poor so there's not way i'm gonna ditch them yet. i've really run out of things to look for on the bike :-/. any other suggestions are welcome.

just as a matter of interest, what type of front tire would one want to run with a Darksider rear tire? - seeing as how that type of tire is a harder rubber compound than most bike tires... just curious, ya know.