T140s rear wheel not centered, why ?

Hello all, I've currently got a 1971 TR6, and it's rear wheel looks centered in the rear fender perfectly. However, I have a 1979 T140E and it is more to the left. (definitely not centered.) However, the front and rear wheel line up perfect ! How can this be ??? I've looked at quite a few other T140s and they seem to have the same problem. When looking from the rear, the rear wheels on the disc brake models OIF is off center, but the rear wheels on the drum brake model OIFs look centered. What is going on here ??? Comments please ...

My best guess is because it is neither a Norton or a Yamaha

nortriubuell said:

However, I have a 1979 T140E and it is more to the left. (definitely not centered.) However, the front and rear wheel line up perfect ! How can this be ???

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A rim which is offset from the frame's centreline won't necessarily prevent you from lining the wheels up.

In the diagram below, the front wheel is in line with the frame, but the rear wheel is (drawn greatly exaggerated) to the left of the frame centre line (represented by the blue line).

If the rear wheel axle is pulled back further on the right than the left, and the steering is turned slightly to the right, the wheels can still be made to line up-however neither wheel will then be in line with the frame (once again the diagram is drawn greatly exaggerated).

nortriubuell said:

I've looked at quite a few other T140s and they seem to have the same problem.

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Has your rear T140's rear wheel been rebuilt? I'm not exactly sure why, but it does seem that practically every wheel builder on the planet builds T140 rear wheels with the rim about 5/16" over to the left?

The '79-on Triumph factory manual states that: "Rear wheel rim offset, 2.920"measured from the sprocket abutment face to the centre of the rim.". And from my own measurements, that should place the rim approximately on the frame's centre line? When I rebuilt my T140's rear wheel, I was unaware of the factory offset measurement so I simply put the rim on the frame centre. I have since checked my T140's rear rim offset against the factory 2.920" recommendation, and it is almost identical.

L.A.B. I do appreciate the detailed reply. Though I have no way of knowing, my 1979 T140E rear wheel appears original. The bike only has 8500 miles on it , and looks to have never been worked on. However, I bought a 1978 T140E brand new in March of 1979. It also had this same offset, with the rear wheel not centered in the rear fender. It really bugs me (just like "crooked stickers on Norton sidecovers"; but that is a post in the access Norton forum) So ... what are the recommendations to fix this ??? Is your rear wheel centered in your rear fender of your T140 ??? All the drum rear brake OIFs I see don't seem to have this "issue" ... so why do all (?) most (?) disc brake T140s have this ??? Anyone else please chime in ... cheers.

nortriubuell said:

So ... what are the recommendations to fix this ???

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Adjust the rim to the factory offset recommendation? My T140 handles fine with the rear wheel in that position, and the 110/90-18 tyre no longer rubs on the chainguard when the wheels are lined up!

nortriubuell said:

Is your rear wheel centered in your rear fender of your T140 ???

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Yes, I'd say the wheel looks to be on the centre line of the the frame loop and mudguard/fender, which it wasn't before! My T140's wheels had already been rebuilt at some point before I got it, as the spokes were stainless steel, however the "wheel builder"(!!!!???) had actually managed to re-lace the original rear 3 x1 dimple pattern rim back on the wrong way around-so many of the spokes were seriously bowed! The bike was an ebay purchase bought unseen, so I was unaware of this until I got the bike home, but to be fair, the rear wheel was the only serious problem I found, as I completely rebuilt the bike as soon as I got it.

nortriubuell said:

All the drum rear brake OIFs I see don't seem to have this "issue" ... so why do all (?) most (?) disc brake T140s have this ???

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Logically, there doesn't seem to be any reason for it, I've heard a theory that wheel offset can compensate for a bike's centre of gravity being off to one side of the frame centre line?
It would be useful to know what the T140 Lester and Morris cast wheel option offsets are.

I have seen them both ways, and none of the bikes had negative handling issues. You ought to take a survey on Commando rear wheels!!!!

Bottom line: if it ain't broke, don't "fix" it.

Try the Triumph Rat forum - Classic and Vintage section. Lots of Triumph specialists there that will know this.