Gt out in the wild

[Claviger]

I wonder what handling characteristic this delivers? There is a reason for it but I don’t understand bike geometry enough to know why they do this. Hope someone here can explain it to me.

I'll take a stand at it, but there are others on the board who know far more about this than I do.

I assume you're talking about the centerline of the axle being offset from the centerline of the fork tubes, more rearward for the axle.

It'll change the trail measurments for a given rake angle either increasing or decreasing it depending on which direction you move the axle.

In this case the direction they moved it creates extra trail, likely in an attempt to stabilize the front end and account for the 4 (I think) degree sharper rake angle compared to the older Rocket.

It provides the effect of creating a more agile bike due to rake angle, yet should maintain the self centering effect the large trail on the current rocket has, making it stable at speed and mid-corner.

Turn initiation should be light, with no apparent trade off in stability vs the Rocket 3 Roadster.

The 140/75R17 (or 150/70R17) // 240/55R16 combo so many of us love may be unsuited to the new bike because of the change, the effect of the diameter change might be magnified by the two good bit to geometry; increasing rear and lowering front which effectively sharpens take angle and shortens trail.

For comparison I found my geometry measurments I took painstakingly last year. So compare those with the new published numbers and you'll see Triumph was after the agility of 28 degrees with the stability of 5.3" of trail. This means Mufasa is inherently less stable and more agile than the new bike is, take that triumph.

Mufasa
Wheelbase 65"
Trail 4.5"
Rake Angle - 28.3 degrees

New R3GT/R
Wheelbase 66"
Rake 27.9 degrees
Trail 5.3"

 

[1olbull]

I reckon that since the rake of the new Rocket has been reduced, perhaps the steer head angle was not changed. By offsetting the axle rearward, the net result of the tire contact increases trail and eases handling.

 

[Claviger]

I may have it backwards but I'm pretty certain moving rearwards increases trail.

They get a nifty marketing line "27.9 degree rake" to make it more appealing as a cornering bike, while maintaining a large trail for stability.

 

[1olbull]

Rob,
I wrote backwards.
More offset reduces trail & less increases, just as you stated.
The steer head dictates the angle.
Tire contact dictates trail - positive or negative.

 

[Claviger]

Other speculative reasons to do this:

It's cheaper to use off the shelf parts, fork tube lengths already available may have dictated this to use off the shelf tubes. Since they had to machine the fork ends anyway offsetting incurrs a minimal cost compared to ordering a custom made fork tube.

If you were wondering where the 0.7" wheel base reduction cames from, well, here it is most likely.

It may have, don't know yet, lowered the front of the bike slightly, bringing the CG forward to where they wanted it.

Triumph does weird **** sometimes for no apparent reason when easier solutions exist, e.g. 240/50R16 instead of 200/60R17.

 

[1olbull]

Our Rockets came with 32° rake & 5.8" trail.
New Rockets are 27.9° rake & 5.3" trail.

Some of us have reduced our trail by raising the rear axle & lowering the front axle with tire changes. The resultant trail becomes about 5.2".
This is a tad bit less than the new Rocket.

Will be interesting to experience the handling differences of the newby with the different tires.

 

[DEcosse]

The Definitive USD Fork Conversion for Sprints Thread - Triumph Forum: Triumph Rat Motorcycle Forums

When rake is more acute (smaller angle), the trail shortens and steering s quicker (but possibly also leads to instability requiring a damper)

When Offset is larger, the trail is shorter i.e. a larger offset (between fork plane and steering stem) also makes steering quicker

(and conversely for both)

When Bull says he is reducing trail by raising rear and lowering front, that is because it effectively makes the rake angle more acute ... ergo ..... shorter trail.
Another really common way to do that is to raise the forks up through the triple clamps (or actually, that is lowering the steering head on the forks) - that will also give more acute rake
(the fork length itself does not enter into the equation directly but does so IN-directly because of its affect on the rake angle)


Rake and 'Offset' will actually directly "offset" (no pun intended) so absolutely need to be considered together to determine the net result of trail; if the offset is unchanged, then most certainly a steeper rake will make the steering quicker;
Wheelbase actually does several things in overall handling (weight distribution being one) but its affect on rake is already factored in the pure trail number (because the change in wheelbase is only one component of the ultimate rake
i don't see an offset number per the spec - you can work it out however if you do the math, since you know the rake and the trail numbers and the tire size (it's 1 am so I'm not doing it now and off to bed!!! )

 

[Nat67]

I would bet money that that rider is under 6 foot tall also , having seen a variety of different sized riders sat on the TFC .

 

[Oleja]

So... no more real touring model?
What options left?
Honda Goldwing and HD Road King or Electra Glide?

 

[Idaho Red Rocket 3]

One more option ... Patients.