Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board 1970 T100S HANDLING CHALLANGES

Good morning guys
I have a 1970 T100S that i just recently put back on the road after a 15 year rest.

The former owner had the bike as a trophy piece is his rec room, so it has been stored in ideal conditions.

I replaced the defective inner tube on the rear wheel, changed fluids, added new gas to the empty tank and the bike fired right up.
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My challenge is handling. Up to 50 mph (80 kmh) handling is good, but when increasing speed to 70 mph/ 120 kmh, I get a strange "wiggling" sensation from the rear. It feels like i am riding on ball bearings.

When on the centre stand, I found that the rear wheel had some side to side play. I removed the wheel and tightened up the bearing pre-load which removed this play.

I still have the same issue ... any ideas?

Thanks
John

No ideas, I'm right there with you, just got inner tube.


I am all ears

Have you balanced the rear wheel, the vibration from this will give weird handling at higher speeds and it's even worse if the rear shocks are not damping.

15 year old tyres?
My arse would be twitching as much as the rear end

When I took one of my bikes out this year, it felt as though I was riding on ice. 13 year old tires. Changed the tires and everything is fine.

Ed From NJ

When you increase your speed from 50mph to 70mph, your total drag (wind plus mechanical) increases by nearly 100 %. Don't limit your investigation to your tires, as many other parts of your bike may lead to what you describe as "wiggling."

Make sure your tires are matched - - don't mix bias ply with radial.
You might try increasing air pressure by a few psi to see if it helps
You checked free play at the rear wheel, but also check possible swing arm movement due to loose connections or bearings/bushings.
Check your steering bearings as well as axle cap and pinch clamp nuts and bolts. Try moving the handlebars while holding the front wheel between your legs to see if anything is loose.
Check motor mount bolts and head steady.
Check chain alignment.
Make sure your forks and your rear shocks are functional (move freely with some dampening.)
Check wheel bearings for excessive looseness or tightness.
As a last check, make sure the frame is not cracked.

All of these elements are subject to inspection for land speed racing.

Tom

P.S. I also have a T100S (1969) and 70 mph on public roads is a bit scary in any case!

When my bike had mismatched tyres it felt like I had a rear wheel puncture on some surfaces. As Tom notes the rear shocks make a difference. Make sure that they are both on the same load setting plus check swinging arm bearings.

Dave

Do you know if the former owner did any work on the swinging arm? I note that you had some side play on the swinging arm and had to tighten up the rear wheel bearing preload to fix this, which is slightly unusual. One thing which may be causing bad handling and cornering is an incorrectly assembled swinging arm assembly, which can result if a previous owner has followed the illustrations in the Spare Parts list.

When I got my '69 Daytona it had weird cornering problems, caused at least in part by old hard tyres, but mainly by incorrect assembly of the swinging arm such that the thrust washer was on the outside instead of the inside of the right fork next to the shims. This incorrect assembly allows the swinging arm to move up to 0.1" sideways. The workshop Manual drawing is correct but the Spare Parts books of all years from '69 onwards are plain wrong.

Regards,
Brian

Brian- he said that the rear wheel had play rather than the swinging arm. I still don't quite understand this unless he has adjustable taper bearings in the wheel hub.

Dave

There is mention here of the rear shocks.

I test mine by removing a shock from the bike, then removing the spring from the shock.

Collapse the shaft of the shock fully, then attempt to pull the shaft back out.

If there is resistance, the shock of O.K. If the shaft pull out easily, the shock has gone bad.