Better steering: 750 vs 850 frames (2014)

Hymph ; No Dimensions HERE Either .


:lol: :lol: :twisted:

Why doesn't one of you actually measure the rake and trail of a standard 750 and a standard 850 ? All you need is a magnetic base protractor , a level and some rod. It is basic useful information. My seeley has 27 degree steering head angle and with TZ350 fork yokes it is superb on a tight race circuit. Probably too quick steering for very long sweeping bends or straight roads.

A pillion & a beer or two would steady it up . :wink:

elefantrider said:

Interesting dialog. If you ask two people, you get different answers. Ask Norvil and he says 850, ask Norman white and he say 750.

When I went with a 18" rear wheel, one Norton specialist thought I was nuts, saying that the bikes handle better on 19" all around. I see racers with both sizes, but rarely a mixed set front to back.

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Re;” I see racers with both sizes, but rarely a mixed set front to back.”

OK, this comment has absolutely nothing to do with the Commando, the pre Commando , Norton 750 Atlas in the slimline featherbed frame, came with a 19 front and 18” rear as standard, with a 1” longer pair of rear shockers to compensate for the smaller rear wheel diameter.

The ATLAS would be 1/4 in. up in the nose ( nominally ) 4.oo x 2 + 18 = 3.5 x 2 + 19 = 26 . x pye for R. R. . the rolling radius is the same , as presumeably are the Shocks .
If theyre 1 in longer , its got 1 in. plus under the mufflers . Which'd help , if you threw out the Mainstand . :wink:

ludwig said:

My guess is that the change was made to please their American clients .

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The problem isn't so much boring roads, but the 35 mph speed limits posted on them and all the cops with radar guns lurking in the bushes.

Or at least that's how it is here in desperate-for-revenue Colorado... :?

ludwig said:

IMO , the 750 frame has the better geometry .
My guess is that the change was made to please their American clients .
The same kind of people who pimped up their bikes with sissy bars , ape hangers , forward controls and 10 ft forks , pathetic attempts to get some fun on their boring roads .
They have no use for an agile motorcycle , and it would only scare the shit out of them .
The 850 can be improved by lifting the tail and lowering the front .

850 road :

750 road :

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I share your contempt for American consumers but take exception to the idea that we are all part of that group. Otherwise, we would all ride Harleys.

This thread is not about who has better roads, bigger balls or more freedom of expression..... this is about the differences between 750 and 850 Norton production frames. Wrenching on brit bikes 20 years ago in a small vintage shop in Santa Barbara, CA, I never found myself wishing for more interesting roads, variety of bikes, or better riding weather.

Back to the topic of frames!

When I went with a 18" rear wheel, one Norton specialist thought I was nuts, saying that the bikes handle better on 19" all around. I see racers with both sizes, but rarely a mixed set front to back.

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I doubt many have experimented like I have on the subtle nuances of wheel size and stem angle on Commandos and V twin or inline 4 modern - to state that any extra effort felt in *initiating* and *holding* turn pressure, [including a steering damper] is the deciding factor of what is going to upset-limit it before a cycle that does not resist as much. Some cycles fight back to hold down like inline 4's, while others fight back to lift back up like the Vtwin's and some like the 750 C'do are mostly neutral to fling down or pick back up on 19" tires. On cycles that fight ya going down a lessor rake angle helps, while cycles that fight ya picking back up, a greater rake angle helps. Until you have enough power and balls to break free either end at speed, the 750-27' stem with 19" on both ends is the sweetest least effort to go around cycle I've experienced. Once power to wt. and clearance to be competitive with Norton 'type' vintage racers, a fatter rear tire, at least up to 130 size allows more power planting near edges. 120-130 size tires [with 149 mph rating] are only available for 18" rims that squats rear to increase rake angle, so that's main reason racers fit 18" on rear but then to regain the steering ease also fit 18" on front. Moderns with big heavy balloon tires are a drag to steer at speed [or even sight seeing speed to me] so lesser rake helps ease pilot load but then makes them dangerous in same way Alan keeps repeating one of his racers stood up for hi side SURPRISE and Ken Canaga also admits feeling guilty of injuring badly a pilot on his experimental lessor rake racer that SURPRISE hi sided.

If ya press a cycle hard enough they will all side hi but at least one I know goes around rather faster before able to induce hi sides and with such predicable on set and flight and spin on CoG in flight its all I can think about 24/7 in between everything else less thrilling in my dull life.

On my stock Combat I broke it in on 18" rear left over from Ms Peel and soon as it got its 1st flat I switched to 19" to immediately notice the extra ease and light footed sense and since Trixie only has ordinary C'do power to mass and is not iso stablized its the best combo I'm sticking with on her and just put up with the fa$ter tire wear, which in ride seasons don't last much more than a month-~4500 miles to cords with normal legal type riding. 18"-120 meat on Trixie also felt like running in boots just touring around. When Peel got rear flat on 18"-120 and I switched same day to spare 19"-110 I had to be careful on turns d/t lack of traction and tendency to hi side with the slightly lessened rake angle. Tendency to hi side on stablized Peel is something I like and developed a use for [phase 4 handling] but once she leaves surface she looses acceleration so 19" shoots her handling in the foot a good bit. For Peel to get best use of the tri-links the slightly lower 18" rear with 19" front allowed rear squat on power to increase rake to resist hi sides to rather higher speed & sharper radius before I let loads off for frame sling shot unwind to get the highest G force acceleration spikes in least traction conditions to other cycles. Peel also had 2" higher front stance which increases rake towards 850's 28' stem, so for my one in a row chopperish Ms Peel, 18" rear and 19" front are her best combo to stick better with total neutral handling, ie: same force to lower or lift lean angle yet no tendency to change lean a set angle so no pilot effort needed once angle set, so more power planting to get faster speed further higher longer hi sides that make up for the cut in acceleration by keeping momentum up and eliminating need of brakes to slow up for front tire traction steering. Of course to be able to enjoy & induce hi sides in public means cycle must be so over powered/fast its falling over on its own so forks flip into straight steer tank slap that horrifies others but is pure orgasmic joy on Peel. On plain Jane Trixie with the 18" rear I could not break free before THE Hinge got her but on 19" I was able 6 times to skip rear out in special good spots, 60 t0 80 mph but then needed some instants of compensation and power reduction to settle down and carry on. Wider rims help traction - up to tread edge but then make the profile too flat & shape edged so less tire patch area when it really matters most. This is why I call the moderns balloon tires corner cripples and sticking with WM2 front & WM3 rear with 'over size' tires on Peel for rounder profile.

Ludwig those switch backs forever Mt roads you impress us all with are not as sharp or dangerous close quarter as the narrow ancient wagon and pig trail bluff face roads here that I tested Ms Peel antics on yet never found her limits d/t fear of on coming RV's and semi's straddling lanes around a blind so your wide open vistas and wide lanes temp me no end to ship Peel over and find out what that might do to me. The Mt Gravel paths you showed us is groin tightening to me though and would take about same sane rates as you or anyone else no matter what cycle I was on though Peel would be my pick for most security. Much as I don't like the 850 sluggish ness I have followed good riders on them in Mt hwys and was strained-fearful to hang with em on my suspension upgraded race tire shod SV650 and told later they were not straining just making time on long trip ahead.





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Hobot stated:

I doubt many have experimented like I have on the subtle nuances of wheel size and stem angle on Commandos and V twin or inline 4 modern

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like you have?

Steve, many of us have owned, ridden, wrenched on, and speculated about Commandos for over 40 years

we bought em new in the late 60s

just a thought, but I seriously doubt that you are better or even qualified to presume you know more than us

this is not a crowing, measuring, or bragging contest

For me, '73 750, 18" WM3 rear, 19" WM2 front.

Taller shocks too; front tire on the wide side (Avon AM18 in 100/90-V19) slows the steering down after the taller shocks and tall aspect ratio rear tire (Avon AM18 in 120/80-VB18) quickened it. Taller rear tire goes well with 20 tooth, almost a 21 tooth.

1up3down said:

Hobot stated:

I doubt many have experimented like I have on the subtle nuances of wheel size and stem angle on Commandos and V twin or inline 4 modern

Click to expand...

like you have?

Steve, many of us have owned, ridden, wrenched on, and speculated about Commandos for over 40 years

we bought em new in the late 60s

just a thought, but I seriously doubt that you are better or even qualified to presume you know more than us

this is not a crowing, measuring, or bragging contest

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"subtle nuances" That's priceless. Like the subtle nuances of a razor back hog.

Ugh folks how can I convey how freaking horrible to wonderful last decade of cycling has been on me. I'm sorry if its taken as pure ego BS brag when all I want to convey is what ya'll may be missing out on that any one can have pretty simply. I'm open to accept all expert advice on characteristics of bias vs radial on front or rear for canyon wall riding impacts, gopher hole bottoming slams at 55-60 launching into flight time through the clots of exploding sod and soil, using gravity to weather vane rear to aim into off sloped Mt Hyw decreasing radius wonders and squaring up long sweepers accelerating by series of short up right full traction sprints. I think best combo on Peel will be a front radial to deform side walls to pull inward harder before let goes and bias rear's stiffer side walls to resist patch shape change or walking around on its grip/slip division point equilibrium. Radials tend to climb road crown while bias don't, which definitely comes into play leaning on edges. Some mystery remains on how that might effect the side drifts on pavement w/o any crossing up or changing lean or fork angle. Do ya get more fun with tire chirps, howls or squeals? Fill me in as ya can please as its murder to mess up.

850's have much better steering with a much more stable feel. I've had several 750's from 1970 onwards and they all had an alarming weave at about 60-70mph which cannot be fixed - hence the 850 frame geometry. The 750 frame was OK in '69 with the old Featherbed fork yokes but they changed to new types with more trail which fixed a slight wiggle at low speeds but that introduced the high speed weave.

If you want to see the effect of all the possible changes and then try to guess the end effect.

https://sebwiers.github.io/motorcyc...bRWD0bCHOP0bFL0bFTO0bFAO0bRT0bNO0bNU0bRO0bRU0

I’ve owned both and find little difference. A 90/90x19 tire in the front will quicken the steering on both frames. Not to my liking.

So, I might as well chime in here too. I rode on the street and raced a 750 Commando Production Racer for a couple of decades, first with the original 3.60-x19 front and 4.10x19 rear, next with the old Dunlop triangular profile 19" race tires, and finally with a variety of 18" race tires, and never saw any sign of the infamous weave. It was a lovely, stable bike to ride at all speeds. I've also owned several 850 Commandos, and the only one that had a problem was a MK3 that liked to weave when rolling off the throttle going downhill at fairly low speed. I had set it up for road racing, with 18" tires, and never had a problem with handling on the track. I converted it back to a street bike, and it still had the weave on the slow downhill road from my house. The weave went away if I got on the gas. I never did sort that one out. I've owned several other 850s, both MK3 and earlier, all on 19" tires, and none of them had any weird handling problems. Just some more data for this issue, and no conclusions on my part, except that some Commandos seem to have this problem, and some don't.

Ken

Interesting topic. I am working on our 67 Atlas which is pretty std but has a 19" rear wheel that is a uk spec and flat bars. Unhappy with its ability to follow tight curves at touring speed .Have to muscle it round. By comparison our slimline 99 (narrower yokes.low rise bars,heavyCraven panniers) has no such issues. Weight distribution seems to be the reason in this case.The Atlas motor is heavier too.Both bikes wear a Ribbed Avon front, Going to try Raising the bars and a 90 90 non ribbed front.

It's sad to read the voodoo accusation of how my 70 750 must handle like shit, because it's frame geometry or it's 18" rear tire. The only real handling issue my '70 commando had was that well known sloppy swingarm tube issue, which the kegler modification completely fixed. It plagued me for years until I found the analysis and instructions for the fix here...

I have roadriders on lightweight, tubless, cast aluminum wheels on my commando. It handles really well. I can take my hands off the bars going slow and it tracks like it's on rails. I have no complaints with my current set up...

oh and as Illf8ted said, the quickest steering will have that 90/90/19 front, although it does give up some contact patch area (grip) to be quicker responding. Some harleys mount that narrow tire to help improve their handling because they need it more. I'm not sure a commando really needs the quicker handling more than the extra contact patch area....

The first 750 Commandos had steering geometry specified by Peter Williams. They crashed a few inexperienced guys, but for a competent rider, might be very good. Good race steering is when the bike tightens it's line in corners as long as it is not a rip-snortan superbike which can hi-side easily. Most road bikes have either neutral steering or tend to run wide in corners. Changing a good steering bike from 19 inch to 18 inch wheels usually makes the bike less nimble and tend to run wider in corners. A longer wheelbase makes the rake change slower as the front lifts and the rear squats when the bike is gassed - so if the bike tightens it's line in corners the rate of tightening is slower. Very short wheelbase bikes can be deadly e.g. Aprilia 250 and 175 production racers.