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Discussion Starter #1
I just picked up my thruxton after having a number of things (see below) done to it and was loving the feel and handling until I hit the rain grooved pavement on the highway. Now, I know and have no problem with the usual wandering or even slight wobble induced by rain grooves on my bike previously (stock tires), but this was down right scary...to the point that I was seriously worried about crashing. At any speed over 50 mph (pretty much on the dot), I'd get an extremely fast and violent oscillating wobble.

The first time it happened, I limped to the next exit thinking there was something seriously wrong. Finding nothing, I reentered the freeway and had no issues on the non-rain grooved lane even at very high speeds. My conclusion that it was the grooves was confirmed when I hit another stretch of them later and the wobble returned (albeit less violently).

What was changed on my bike:

1. airbox removed and carbs rejectted (unlikely to be the cause)
2. new fork springs
3. new shocks (YSS RG302TRCL - configured for my weight)
4. new tires (avon roadrider)

I'm guessing that the tires are the most likely suspect. The question is, could this be an alignment issue or is this just "the way it is"? Unfortunately, the rain grooved section are on my daily commute (including across a ~4 mile bridge), so just living with the extreme wobble I'm currently experiencing isn't really an option. I hope to get this sorted out, because otherwise I'm just loving how the bike feels!

Thanks in advance for your help as always!

P.S. Does anyone need a pair of stock thruxton shocks? I'm willing to pass them along for the shipping cost if they are of use to anyone. Always glad to help out a fellow forum member!
 

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Don't ride a Thruxton and don't have rain groove highways around here - but occasionally while on my Bonneville I encounter grooved roads awaiting repaving. Yeah man, much wobble, but these grooves are not straight or anything. Have read things about Thruxton handling - more negative I guess. Have heard steering dampners are good for them.
Don't like to wobble!
 

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Grooving along...

You may just have groovitis.....that is, you are too tense going into the grooved area and are clamping down too hard on the bars or basically tensing up in anticipation of a problem.(crash)
The easiest way to avoid the problem is when you see a grooved area coming up ahead don't look at it like an obstacle, instead, just visualize yourself on the other side of it smoothly riding along....this may sound silly but it works for a lot of us.
Relax and loosen up going into the grooves....the bike will meander around a bit but won't do anything bad....it's only when you tense up that you cause the problem.
Any one else out there with advice?....
 

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Some tires are much more prone to problems with rain grooves; the OEM tires on my W650 were truly frightening. I swapped them for BT45 'Stones and the problem went away. I thought about this when I replaced the tires on my 07 T100 since SoCal has so many rain grooved freeways (and no rain - it's 78F here today)

Dick
 

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Try lightening your grip on the handlebars. Pretend your holding eggs - works to prevent wobbling. Also, you might want to hold onto the stock shocks. If your bike gets totaled and your insurance company sends the salvage company to pick up your bike, you can arrange to keep your upgrades if you supply the original parts - I did.
 

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Discussion Starter #6
I've never had a problem on this road with this bike before, so I don't think I'm gripping too tightly (though maybe I just have to be that much lighter with the new setup and tires).

One thing the mechanic mentioned when I brought it up this morning was that the new rear shocks are about 1" shorter than stock. this changes the geometry and shifts more weight backwrds which might cause this. His suggestion was to lower the front forks by an equal amount.

This seems like a logical response. Any thoughts?
 

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Yes. My Lasertec will track around a fair bit once it is about 70% worn. The bike does much better if I do as the previous post suggests and keep a light touch on the grips. I wouldn't describe it as dangerous, but it is quite noticeable.

Hang on to your stock shocks in case you need to have your new shocks serviced. I was told not to lay my shocks on their side, so have them hanging in the garage.
 

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Discussion Starter #9
His thought was that it may have shifted the balance of weight backwards and thus lightened the front end.

It seems to handle beautifully in the corners at the moment (though with the new tires I obviously haven't pushed it hard).

I mainly just want to make sure this isn't a tire balance or other treatable issue. I will adjust the front forks, too, though.
 

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I mainly just want to make sure this isn't a tire balance
If it is a balance issue, you can create the problem on any surface, but sometimes more pronounced at certain speeds. Find a good straight and level road, get some speed and roll off and go hands free. As my Lasertec wears, the front end will start dancing once the speed drops below 35 or so. The tire is so light, it probably could use a new balance late in life. It is also so cheap, there isn't any point in it. And it isn't to the degree I consider it a problem. Just an observation.

As to moving the front around, try a few small changes and make sure you don't create a problem. An inch seems like a lot. When I installed my new shocks, it didn't change the rear height at all.
 

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I have an 07 Bonneville with the same tires. I have the same issue on the grooves. I hate them so I ride my Sprint if I have to ride on the our So Cal rain grooved freeways.
 

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Hang on but let it roll

Hey guys, it's not a Thruxton vs. Bonnie thing here...freeway grooves affect all cars and bikes as well...all vehicles. Like a previous poster said...it's all in how you handle it.

RELAX...you are not going to crash unless you tense up and fight the wobbling.

Admittedly, the Thrux bars being narrower, give you a little less leverage on the front end...but you just need to let the bike self-correct as it rolls along.

Actually, in a straight line the bike needs little or no input from the rider at the bars. If you've ever let go of the bars on a bicycle or a motorcycle you'll see it wants to go straight. If you lean left or right it will turn that way.

So, hang on to the grips, but don't grip so tightly that you exacerbate the problem by stifling the bike's natural movements over goofy terrain. I've been riding on the street and dirt for 40 years and I have experienced virtually every riding situation, including thousands of miles of these freeway rain grooves.

Be safe, and have fun!!

Cheers,
BLIGHT:motorbike:
 

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Discussion Starter #13
it isn't an issue of a little wobbling, as I am well aware of the effects of rain grooves and how to handle the wobble. I am referring to wobble so extreme that it borders on tank slapping occurring on a bike which (prior to the aforementioned changes) exhibited no wobbling on these exact same roads.

Maybe it really is nothing more than normal for these tires (in which case I 100% do not recommend the Avon Roadriders for anyone who spends any time riding on grooved roads), but maybe it has something to do with the suspension changes I made, as well.

That's what I'm trying to figure out.
 

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You will not have this problem with BT-045 Battlax tires. I don't know why, but they seem to be impervious to the rain grooves on SoCal freeways. They aren't that great a tire for other reasons, but for me the rain groove issue was a big deal and the problem is now GONE.

Dick
 
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