frankdamp said:I can't make out from the rather blurred pictures whether it has the original Italian 2LS front brake or not.
frankdamp said:that the need for a frame stiffener didn't rear its head until the front brake could generate enough bending moment to cause the fatigue failure in the top tube.
Onder said:Tire pressure is something I've always wondered about. How much depends upon the riders weight? Im in the less than 9 stone weakling category and
If I put in pressure like he says he does the bike would be bounding along like a rabbit and the center strip tire wear factor would be even more rapid
than usual.
What did Norton consider "normal" rider weight to be?
rx7171 said:According to the Norton Workshop Manual in the Routine Maintenance Section with a single 168 lb (76.2 kg) rider it's 22 PSI Front 24 PSI Rear.
Since that is what I weigh that is what I use. I got almost 5,000 miles on my last rear tire which I suspect I wouldn't have got with the higher pressures others are using.
Two up 168 lb riders 24 Front, 28 rear.
Two up with 100 Lb luggage. 28 F 32 R
Under Technical Data in front of the manual they refer to both front and rear as being 26 PSI without mention of rider weigth or single or double riders. It does however say "Refer to Tire pressure section for permissible variation". Lack of consistency within the same manul
is disquieting.
Manual refers to 19" wheels with 4.10 tires. Dunlop Tires. (TT100 I suppose) Which is what I run.
frankdamp said:Bear in mind though, that the need for a frame stiffener didn't rear its head until the front brake could generate enough bending moment to cause the fatigue failure in the top tube. I was long gone from N-V and working for Boeing by the time that problem surfaced.
1968 Norton Commando Structure Recall 74V239000
NHTSA: Action Number: N/A Service Bulletin Number: 74V239000
Report Date:
Dec 05, 1974
Component:
Structure
Potential Units Affected:
1400
Manufacturer:
Norton/triumph Corp.
Summary:
Consequence:
Remedy:
Notes: Norton campaign no n/a. Possibility that the large diameter top tube of the main frame, may fracture in service due to unusual conditions of use following an induced weakness initiated by unsatisfactory crating and warehousing procedures. (corrective action, on machines affected, within the series of engine numbers 126125 to 128634, the frame should be changed in accordance with the instructions given in the 750cc model workshop manual (part no. 063419). )
Jerry Doe said:He says 32 and 36 PSI for the tires. That seems a bit high to me. I normally run 28/ 32. Maybe I should try inflating more and see how it handles. Good article, thanks for sharing..
Matchless said:Avon recommended pressures for Roadrider 3.25x19f & 4.00x18r on my BMW R100RS are 32 & 36psi. I am running the same size tyres on the 920 Commando & using the 32/36 pressures.
Front Tyre
Roadrider
Pressure front:
2.0 bar (29psi)
Front size:
4.10-19 61H TT or 100/90-19 57V
Rear Tyre
Roadrider
Pressure rear:
2.2 bar (32psi)
Rear size:
4.10-19 61H TT or 100/90-19 57V
I asked Avon directly what tire pressures should be correct for Roadriders on a Commando, and they said 32 rear and 29 front.
There's a piece about it in this month's copy of the NOC's Roadholder magazine.frankdamp said:It's interesting that neither of the two prototypes ever showed a problem with the top tube. We really beat the crap out of those things. Once we got the various mechanical reliability issues sorted, we were doing 500 miles a day, not much of it motorways, either. Later in the program we were running 10 hours a day at the MIRA test facililty doing 100 mph on the tri-oval. With gas stops, rider swaps and chain adjustments, we got about 850 miles in the 10 hours. Those two bikes didn't have the production gas tank and seat, nor did they have side and center stands. Whether that made for different load patterns, I could say.
Whether Plumstead made changes to materials or wall thickness on the main tube after the program moved to a production development from engineering preliminary test, I don't know, but I'm surprised that just lifting the bike on and off a truck could break it.