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Discussion Starter #1
Hi everyone. I recently replaced both of the tires on my TLS because I had a screw stuck in the back one and they were both worn down enough that I didn't feel like I was losing a lot of money over it, plus I ride two up a lot and I did not want to have a passenger and be relying on a tire plug. The old tires were a michelin power pilot for the front and a dunlop sportmax Q2 for the back. I replaced the front with another power pilot because I found one on sale and I replaced the back with a shinko 009 raven which has pleased me on past bikes. Yes, I mix tires :D Anyways I have put about 350 miles on the new tires and so far I have been pleased with the break in and ride. They are grippy and I have had no problems making nice turns in the twisties. However on two occasions I have gotten my bike up to about 100-105 mph and the front tire begins acting very squirrley, oscillating back and forth and causing the bike to wobble. I have always had a steering dampener and it has always been set pretty tight. With my old tires my bike was able to go 155-160 on a few occasions with no problems (other than me being scared shitless). Does anyone have any suggestions as to why my new tires are giving me speed wobble? I understand it could be because I mixed tire brands but I doubt that is the case. Do I need to use them more before getting my bike up into the triple digits? Is it possible a weight has fallen off and the tire is off balance? :confused Any help would be greatly appreciated.
 

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check the balance.......

never assume that the problem is where it seems

the rear tyre will make the front shake too.

check the chain tension too.

also static balancing and dynamic balancing produce different results.

wheels bearings ?

stiff links in the chain?

its an S so check the swingarm at the pivot area for cracks.........

check the front RH side of the steering head frame area for cracks above the radiator
 

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What he said.

But start with re-balancing both front & rear and checking them for any out-of-round while on the static balance stand or dynamic balance spindle.

Then check the chain and sprockets.

It's quite possible they didn't balance it at all, unless you ask them to.

Come to think of it, I'm not sure whether mine are balanced at the moment...I always should but tend to do it when I find the need, which just inconveniences me to take it back off & on etc.
 

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Check the front axle pinch bolts, rear axle nut...

How's the suspension working?

It's a TLS< so MAKE DARN SURE ALL THE BOLTS THAT HOLD THE ROTARY DAMPER IN ARE STILL THERE AND BOLTED IN TIGHT without any frame cracks where they bolt in. My second TLS had a frame crack where the rotary damper mounts, so I converted to the R1 shock where the rotary was, and a Bitubo where the SOAS was, and I let them split the damping chores; but that's with a slight extension on the swingarm.
 

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Try using Dyna beads. I have been using them for a few years now and love them. If you never heard of them they constantly rebalance the tires every time you stop and then go. They are tiny ceramic beads that go in the tires. I use one ounce in the front and two in the rear.
They are the best $10-$15 you will ever spend.
 

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Discussion Starter #6
Via phone the mechanic who put my tires on says he always balances them, and he is a trustworthy local fellow with good reviews so I expect as much. There do not appear to be any loose bolts, other loose pieces or cracks on anything on the bike. The chain and sprocket both look healthy and the slack/tension is appropriate, although other than that I am not sure what I am looking for. I do not have the tools, time or patience to check any internal parts or the tire bearings. The front shocks are in good shape and the original owner replaced the back shock with an ohlins shock which has been working fine. Today I turned my dampener to the tightest setting (so tight its impossible to make slow turns with) and the vibrations and oscillation still happened but not until I reached about 120-125 this time around. I have been testing in on a straight freshly paved road so I know it is not the road surface causing it either. If I can't figure it out I will look into the beads or another balancing product.
 

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To be honest if you have checked what the guys said and tires balanced I would point my finger at the tires, sometimes bikes have funny reactions to different tires, had a ZX6 that was unrideable on Dunlop 207gp's (remember them?) but the SRAD took to them fine, changed tyres and then problem went away, bare in mind profile of the tyres are massively different between manufacturers, and even manufactures type of tires (eg supercorsa to supercorsa sp etc etc ) tires so a 120/70 mich can be different from a dunlop. You have mixed to different makes and poss type of tire so could you throw another old back tyre in just to rule that out?
 

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And some tyres just don't mix. Could be the Michelin and the Shinko just don't get on.
 

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Try using Dyna beads. I have been using them for a few years now and love them. If you never heard of them they constantly rebalance the tires every time you stop and then go. They are tiny ceramic beads that go in the tires. I use one ounce in the front and two in the rear.
They are the best $10-$15 you will ever spend.
Got pics or a link? I'd sure be interested in something to help further balance & dampen my trailer tires. Even when balanced, they bounce more than they should. I'll probably have to start by replacing them, including the spare. They're cheap trailer tires, Continentals I think, I could get much better ones. These are probably bias-ply and I've heard that good radial trailer tires work much better.
 

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Got pics or a link? I'd sure be interested in something to help further balance & dampen my trailer tires. Even when balanced, they bounce more than they should. I'll probably have to start by replacing them, including the spare. They're cheap trailer tires, Continentals I think, I could get much better ones. These are probably bias-ply and I've heard that good radial trailer tires work much better.

You can get them at your local Napa or on eBay. Ask for balance beads. Dyna bead is a product name. There are many different manufacturers of them now.
 

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Discussion Starter #12
Is it possible that the fork oil never having been changed could cause these problems? My bike has 28k on the odo and the oil has never been changed according to the only other owner, but that being said the other tires I had on gave me no problems with the current oil so that doesn't seem to make much sense. The tires are balanced and everything else seems to be in check, no cracks, loose bits etc and the chain and sprocket are lubed and good to go as I have already said. I have experimented with different tire pressures ranging from 33F/33R all the way up to 38F/40R and no matter what the speed wobbles still happen. It is my understanding that what is happening is the early stages of a "tank slapper" and the only thing preventing that is the steering dampener. I tried to see if I could ride through the oscillation of the front tire (with my dampener fully tightened) but by the time I hit 115-120 it was so severe I had to lay off. I don't usually ride in the triple digits but I find it extremely irritating that I can't, if the bike can easily get to 160+ with me on it I want to be able to get into the low 100s without the fear that I will be thrown off the bike. I may ask my mechanic if he will balance them again just to see if he made a mistake but other than that I do not know what else I can do.
 

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The Michelin is a taller tire, it needs to with it's own kind. The shinkos are black and round(mostly). This combo has thrown the chassis geometry all off. This is a major reason/result why not to mis-match brands, some can be okay, some, not so much.... you are asking a LOT out of the shinko...
 

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Discussion Starter #14
I was beginning to suspect that as a possible cause, but shouldn't tires of the same size from brand to brand be the same size with only minor variations in shape? The shinko is 190/50 zr17 which is the same size as the dunlop Q2 that was on in before, I wouldn't think that it would be that much lower. What does the tire being black and round have to do with anything, aren't most tires black and round?
 

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I worked at a dealer for over ten years and do a fair mount of tuning and setup for trackdays at Miller's Motorsports park down the road from me. My point is, shinkos are real basic, you don't get a lot other than an okay tire that is black and round. They usually have a very flat profile. They work. A lot of riders use them, but when you want more tire that raises the bar for quality and maybe specific profiles, compound or duties. Then you need to get better stuff. A friend of mine runs a lot of cheap tires on his bikes, they work, but he just rides and is not looking to ask much more out of his stuff, good enough is cool to most. Others like me(OCD included) have to drive ourselves nutty looking for something we prob don't really need. But, hey it works for me....Enjoy whatever works, if it don't work then the search is on. It begins....
 

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Discussion Starter #16
So if I understand correctly a shinko's tire profile is flatter and not the same shape as other brand tires even though it is the same size?
 

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Exacta'moondo. Sizes list tread width and aspect ratio(sidewall height in relationship to tread width), which is allowed to vary as much as something like 17%. 190/55s are very popular to get extra rear ride height into a setup with just a tire change compared to the 190/50 many bikes come with. Quickens steering and makes turn in more lively. Not everyone's cup'O tea, but a better setup for many of us. Some riders like the more relaxed turn in of a rounder profile, but really need to match front and rear at least to compliment each others character. A lot of changes can be made with varying tire brands and models to suite ones riding style with tread shapes.
 

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Discussion Starter #18 (Edited)
I guess that makes sense. So what would you suggest I do? It seems from what you're saying I can use up this tire or replace it with a taller one (55) so that it will match the front tire? Or could I replace the front tire with a 120/65 to make it lower to match the back tire better? I appreciate the help.
 

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I think all that's true. But still...why unstable at high speeds? I'd imagine all kinds of mismatch issues to consider while turning, but I think this thread started off complaining about straight-line stability at high speeds. What's the speed rating of the Shinko? I'd expect a shorter tire in the back to be more stable at really high speeds.
 

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Discussion Starter #20
The shinko is rated to 168 and I am having problems around 105, at lower speeds its stable and the turning is fine (or seems fine to me) but I am not a tire expert. So a shorter tire at the back would be more stable than a taller one?
 
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