Periodic judder at high speeds.

[car]

Well, high speeds for a DR200SE that is.

Riding down and then up SH1 today on my "new" DR200SE I noticed an odd periodic juddering at highway speeds. About once every second or so, I'll get maybe four shakes, putting a little vibe on the mirrors and through the seat. At first I put it down to road surface, but it continues on the smoothest of tarmac.

The bike's in good nick, low mileage. It's wearing a set of part-worn Bridgestone Trail Wings on new tubes, which I fitted myself yesterday, in order to get it WoF'd and re-registered today. The tyres went on okay and the beads are seated well. Tyre pressures are to book. Chain slack is to book. Wheel bearings looked good while I had the rims out, everything appears to be ship-shape.

The wheels obviously haven't been balanced (does anyone balance trailie wheels?) and I wondered if the one-second period was down slightly imbalanced 21" and 18" rims going in and out of phase. Dunno how different the rolling radii are. This is the first bike I've ever ridden at highway speeds that didn't have a cush-rubber, so I wondered if maybe this just a "feature" of fixed sprockets.

[quallman1234]

Are the tires equal tread all over? at the back.

I used to get the mad judders on the DT because the tread or knobbly bits were worn unequally.

[Hawkeye]

Just stop lane splitting over the cats eyes. That will sort it.:rofl:

[cave weta]

Other things you could look at are steering head bearing play and fork slider wear. my bet is chain freeplay though. what year is it?

[Katman]

I'm assuming you don't have the rimlocks fitted if you're only using it on-road.

[Robert Taylor]

Well, high speeds for a DR200SE that is.

Riding down and then up SH1 today on my "new" DR200SE I noticed an odd periodic juddering at highway speeds. About once every second or so, I'll get maybe four shakes, putting a little vibe on the mirrors and through the seat. At first I put it down to road surface, but it continues on the smoothest of tarmac.

The bike's in good nick, low mileage. It's wearing a set of part-worn Bridgestone Trail Wings on new tubes, which I fitted myself yesterday, in order to get it WoF'd and re-registered today. The tyres went on okay and the beads are seated well. Tyre pressures are to book. Chain slack is to book. Wheel bearings looked good while I had the rims out, everything appears to be ship-shape.

The wheels obviously haven't been balanced (does anyone balance trailie wheels?) and I wondered if the one-second period was down slightly imbalanced 21" and 18" rims going in and out of phase. Dunno how different the rolling radii are. This is the first bike I've ever ridden at highway speeds that didn't have a cush-rubber, so I wondered if maybe this just a "feature" of fixed sprockets.

There is every reason to balance a trailbike wheel that is ridden at highway speed, just as much as a road bike ridden at the same speed.....

[car]

Other things you could look at are steering head bearing play and fork slider wear. my bet is chain freeplay though. what year is it?

It's not that ropey old crapper I was asking about before. It's a 2002 SE, but it appears to have spent much of its life in t'shed. It's got a whiff over 1000km on the clock, shows little wear.

I gave the steering head another once over this morning: no notches, no clunking, no movement other than a nice smooth left to right and back again. Fork slider wear is beyond my ken, but do you think it likely on a low mileage bike? The chain slack was to book at rest, but I'll run it round tonight and check for tight spots. Also, I'll give it a flap with my fat can on it, see if that makes a difference.

[car]

I'm assuming you don't have the rimlocks fitted if you're only using it on-road.

Correct. I do intend to take it off-road, but probably nothing more adventurous than those Bridgestones will cope with. But no rimlocks.

[car]

There is every reason to balance a trailbike wheel that is ridden at highway speed, just as much as a road bike ridden at the same speed.....

Aye, that would make sense. I know plenty of people who don't bother balancing road bike wheels, too. (But not me.)

Does anyone here balance their own wheels? Are there any good old home mechanic methods for doing so?

[car]

Does anyone here balance their own wheels? Are there any good old home mechanic methods for doing so?

Yes, there are:

http://faq.f650.com/FAQs/WheelBalancing.htm

The front wheel was a fair way off balance, rear was off but not so much.

End result: no more on-off juddering, considerably less vibe through the bars, life is good.

[pete376403]

Eccentric sprocket and/or tight spot in the chain could cause. check the chain tension in a number of places while turning the wheel

[paturoa]

Another reason that it was regular could be that both wheels are out of balance, and being different different diameters, after a bunch of revolutions their "out of balance" coincide.

eg a 21 inch wheel will have about a 9 inch bigger circumference than a 18 inch. The 21 inch will have a circumference of about 63 inches. So they will align about every 7 revolutions.

[car]

eg a 21 inch wheel will have about a 9 inch bigger circumference than a 18 inch. The 21 inch will have a circumference of about 63 inches. So they will align about every 7 revolutions.

I didn't get round to measuring (or calculating) their rolling radii, but I did wonder if it was this drifting in and out of phase you describe that was producing the on-off-on-off. We'll never know.

[Pancakes]

First thing I thought of is when I have run mountain bikes on knobblies at speed on the road. Kinda like waht Paturoa said. The knobs/tread whould come into sync then off again like a faster but quiter air raid siren, VVVVRRRBBB VVVVVRRRRBBBBB VVRRBB VVRRBB VVVVVVVVVRRRRRRRBBBBBBBB!