Bikes like that are made for running around L.A. Los Angeles California, NOT Lethbridge Alberta Canada, where I'VE bottomed out the stock DOHC CB750F/CB900F rear end -say, going over a rural railroad crossing cranked out at 180k dropped down from the 250k I was doing before I noticed the crossing in the distance. Catching air going over a nice rise, landing down on the tarmac on the leeward side of said rise, and grinding sparks off the whole underside of the bike. If you're gonna ride the bike like THAT, then don't #$%* around with building this type of rear end. It's bad enough when the tire hits the whole underside of the inner fender and #$%*. It would suck really really hard if you're talking about a narrower point of impact AND if that tire were for one thing a radial and another thing radial that's under rated for the bike's weight like the typical 150/55zr17 type of deal that I keep seeing people put on large fours. I'M going with a 160/60zr18 on MY wire wheel radial tire swap, I'd do the same on a Kosman widened wheel too but if there's a tube in there it's even more likely the radial is gonna heat up really bad and all of the factors of the tire's carcass holding up to that huge weight of a SUPER-bike (as opposed to the hyper-bikes they're designed for, in the case of the 150 width 17" radial probably a 600cc or LESS, more likely a 400cc-500cc twin, look into it!) would be all over-done and synergistically/collectively #$%* YOU OVER not just by blowing out like you might suspect, but my DENTING really really hard on that bar.
See, the whole point of a radia is that it's carcass is more flexible, it's able to conform to the shape of things. Hence, that load carrying ability is a huge deal. Put too heavy of a bike on it, and that conforming ability, that suppleness of the carcass, is gonna allow the tire body to really really flatten out. Well and good if you're talking about getting a better contact patch on some nice clean California freeway. I spent some time down in souther Cali as a teen, when I was into skateboarding. I bought a new board down there out-fitted for riding half-pipe back home, but I found it suitable for riding street down in Cali', as I recally I had the impression that I was INDOORS all of the time, I mean other than the azure canopy and the glaring hot sun ... that dropped off the horizon like a light switch going off nothing like the sunsets we have here in "big-sky country". But I found it amazing I could ride the streets on those 99 durometer wheels, the streets were so smooth and so clean. Like tile in a shopping mall floor. As a Western Canadian guy, when it came to skate wheels I had really appreciated my Powell III's 60 durometer squishy wheels for street riding, 'cause the gravel wash that came out of every alleyway, the road "salting" sand and gravel that was all over the intersections and washing up onto side-walks, suffocating the grass in some places, forming a "Pike-Crete"-like substance when ridges of frozen automotive exhuast coloured slush laden down with said sand and gravel formed burms in the middle of roads, basically an environment where my kid's bio dad suggested she wait until mid-summer to renew this year's insurance on the scooter I got her for her 14th, because there's so much #$%* on the roads during spring when everybody's excited to get out riding ... I said it's better to learn to ride on that type of stuff, just like it's good to learn to drive a car in the dead of winter in Northern Alberta. Combining elements of figure skating, boating, running a locomotive on steel rails (because of the thick ice with deep grooves in it, as well as the six foot berms in the middle of the road) as well as a good foundation in preparation for being lost in a blizzard and hence keeping bags full of extra warm jackets, blankets, sterno fuel canned heat candles hard tack rations chocolate bars and MRE's, rubbers mints and vanilla incense to hide the smell of ass, a buck skinning knife grizzly-bear repellant trap-line snares a .22 for small game an axe for constructing a log cabin, and loads of Vitamin-C so you don't get scurvy, in the trunk along with the booster cables and spare tire etc. And take if from me, DON'T drive a white volare station wagon up there, you want a vehicle as bright as possible in a white-out blizzard with twenty feet of absolute visibility which somehow the big rigs insist on running all out at 140km/hr through, often right on the shoulder where you thought it was safe to pull off to the side. Paint the #$%*er dayglo hunter orange if you have to, but don't drive a white car on the highway from Grande-Prairie or the one from Ft Macmurray for that matter, to Edmonton, in the dead of winter. As a young guy living up there, I took up smoking just to know I had a source of fire in my pocket at all times. And though I was fond of layering up in winter gear and walking all night long in thirty below (which is warm actually 'cause you can realistically expect forty to fifty below weather, that's not counting the wind-chill) under the aurora borealis, the best training for survival was the way my high school sweetheart and I used to hump in the snow-banks all of the time.... Hmmm. It wasn't ALL frost-bite temps on one's extremeties. Ha ha. Ah yes, Northern Alberta winters, with the frozen dead cows and the old people found in the spring-time sitting in their out-house. One guy died close to my place, when he sat down, drunk, at a train crossing, waiting for the train to go by. Probably passed out. Also, my good buddy Doug was a psychiatric nurse up there, told me how the found a naked Salvadorean guy running in a field, didn't speak any English. That's some X-files #$%* for you right there. Anyway yeah, you wanna learn to drive in the WINTER, you wanna learn to RIDE on the rougher roads, on the back roads where the good curves are where the canyon carving means there might be a rock or two fallen off the walls of said canyon.....
If you're just running around, indeed "cafe racing" which is to say going from Starbucks to Starbucks, or maybe you feel that's not grown up enough for you so you wanna go running from pub to pub, so you're grabbing a beer at Macgillicutty'steak-house and you wanna go slumming across town at some place with an open stage night for amateur blues guitarists ... ugh ... either way if you're just running from point A to point B, maybe C but sure as #$%* not Z let alone any of the non-alphanumeric code characters out there on the edges of the grid, if you've just got a relaxing day's errands necessary to the poseur life-style, then that rear wheel isn't gonna see the speed, though maybe the heat is a possibility (though I hasten to add that I never saw an egg fry on the side-walk in Cali I HAVE seen just that on the roads up in Fort Mac, close to the summer solstice when the day is 23 and 1/2 hours long, which is to say there's a half-hour of sun set-rise and the sun, though it may be hitting the pavement at a more oblique angle it's beating down for a good eighteen to twenty hours of that day), all the same you're not going to see the irregularities in the road surface, unless you're bouncing up and down the hills of San Francisco, Steve Mcqueen - BULLITT style. That's about the one and only way you're gonna screw with that suspesion. Even coming from the central plains, nothing is quite so flat as the region around Sacramento, but I'd say that one factor that sticks out in my mind was how the driveways and parking lot entrances and the like, where they cross the sidewalk there seemed to always be a nice smooth transition, rather than an abrupt two or three inch square cornered mini-curb. Even the curbs themselves, I sure saw a lot of the radius type, rather than the square ones with the frost heave and the hundred and fifty foot cotton-wood trees lifting them up and cracking them so that chunks of them tumble next to your tires while you're parked for any length of time. There's also the whole reasoning behind why people in the country prefer a dual sport or off-road bike, which it due to the #$%*-head semi-feral dogs people keep, you want a knobby tire on there so that the bike will BITE BACK if they catch up to you and chomp around your back rim. Ha ha.
But yeah, I see all sorts of problems with that set up. Okay, you COULD have an extremely stiff spring rate in those Hagons, one that's quite steeply progressive, so that you do get a bit of cushioning, when you roll over a bubble-gum wrapper, or worse yet if you roll over the gum itself, but when it comes to a good solid bump you're not getting any softening of the blows. A tight low rear end with stiff shocks is gonna have all the characteristics of a hard-tail if you take it to it's logical conclusion. When it comes to MY CB750, a DOHC '82 'F, I think along the lines of the RCB1000 endurance racers with the taller stance to them, and some good range in there for dipping fulling into the corners. The only time your bike ought to have a stance like these low riders, is when you're dipped over in a fast sweeper and the cornering forces push it down that much. Or perhaps, when going over the bumps and rises I mentioned before, catching a bit of air and then landing with a nice satisfying cushioned landing, like a net at the bottom of a trapeze.
Naw, what I picture happening in such instances, on THAT there bike, would be that too small radial wrapping itself around a third to a half of that bar's diameter, and gripping accordingly, maybe it'll just spin on the rim or maybe it'll unseat the bead entirely. Of course, your rim itself might get bent too. Oooh, and maybe that fancy new cross brace might get bent as well. But what you're gonna NOTICE, is the inter-vertebral disc in the lumbar region of your spine stretching out like a bellows, and this is where you start talking about radial versus bias plies, as the outer dura of said disc is going to rupture and a squiggle of gristly inner disc material (my own surgeon described it as "like cooked lobster meat") will fill the areas normally taken up by fluid void space and your sciatic nerve roots, will now be irritated and inflamed by that disc material, and you're not gonna be ridng anything like you did before. Maybe your feet will slip off the pegs and your balls will get bashed on the back end of the tank.
There's just a whole host of problems with it
Look at a KZ frame from the same era, you'll notice that the cross brace hump is lower, and you'll notice that the ass end will often have a loop built in, on an LTD type KZ at least. But the KZ doesn't have the horizontal line of the Honda. Think of the Honda's frame rails as a visual continuity with the horizontal bottom of the tank, and the true top of the frame, where the bridge loops over, as where the KZ frame would be sitting with it's straight brace. If you're gonna compare with a pre-unit Triumph perhaps you wanna limit your speed at about that point in time as well. And the bumps would be a part of the picture as well. The Hondas of this period don't borrow so much from street bikes of the prior decade and more, they're inspired more my the Italian stuff more so than the British bikes I don't care what you say, but the frames derive from race frames, the suspensions too. So don't even go there with the Triumph frame loops. Hell, I don't understand why a bike with such impressive Japanese heritage would be Anglicized in the first place. So think long and hard about why you want that loop back there in the first place. Me, I'd prefer my frame to be reinforced with a full sheet of steel across that whole span, bent in a curve just like the arch the Honda comes with, hopefully good and stiff in spite of the curve. Perhaps if it's a compound bend with a fender radius to it, if a piece of sheet steel could be constructed like that for each type of Honda frame each size, then that's what you want welded in there for reinforcement. But it's a pretty complex shape of steel, so it's gonna be hard to find. Maybe there's something in a solid steel Harley fender that could be welded up in there and then cut away so it's completely hidden. And then the classic Honda looking flattened bar ends at the rear end of the frame, a rather high end component for the day, in that these parts have been shaped and welded up just to fit the signal lights in there, as opposed to a whole frame made from simple tube like you'd find in a home garage, like the "featherbed" frame, by then outdated by a good decade or more....
You COULD use a loop like that on the ass end of your frame, without going to a vertically bent cross brace that gives the hump under the typical Honda CB seat, but you'd need to bring it way further back to the rear, so that it loops behind just like the frame does up front. Fact is, the best simple low-budget way to keep those two side rails in line, other than leaving it all stock, the best low-tech brace for a twin-shock suspension (otherwise I suppose it doesn't matter 'cause on mono-shock it's only your own ass back there not the weight of the whole bike), the best place would be a straight link between the upper shock mounts. And then you'd wanna bring your stance up taller with longer shocks or raising links something like the lowering links they used to sell when choppers were all the rage. Assuming you're not watching OCC all of the time, and that's not your motivation for building a bike, in which case maybe you think choppers are STILL all the rage.... But yeah, with that taller stance you might wanna combine the smaller diameter wheel that the 17" hoop affords, as does the 16" hoop they used to put back there, as this will give the swingarm more of an angle down from the horizontal, I hear that 13 degrees is optimal, as it fights the squat under accelleration effect. But yeah, you'd get a half inch further of moving that swingarm angle down, plus the other half inch of the tire clearing that top brace, for every inch of smaller diameter of the overall wheel. not just the rim hoop diameter. Hence, the lower profile / smaller aspect ratio tires. Which might make one question why I went with the 160/60 zr18 rear tire. Well, the weight capacity was the first thing I looked at, plus it's as narrow of a radial as would carry this weight. One could go with a 17" radial back there, but they'd best go along with a 170 or 180 plus. Especially if going for two-up riding, as I am. Of course, not as aggressively as I'd ride solo. If that back tire's got a hope in hell of pulling a wheelie ... might be possible without the heavy comstar rim up front, we'll see ... then it's gotta have a good high number, up above 70, for the load capacity. It's funny that they still rate rear tires higher than front tires, when you're just as likely to do an endo. But I suppose it's about the power laid down through that rear tire, and people's propensity for doing a burn-out on the rear tire, combined with their fear of sliding the front tire around in ANY capacity. Hence, you've gotta think of that whole load bearing capacity as a combination of factors. Pressure, temperature, speed, tarmac type, yes weight too AND the amount you're sliding it around. A rougher tarmac is gonna bend the rubber around every single pebble, and that bending translates to heat. So while it might seem like greater traction just in that the asphalt's tar matrix is worn and the crushed rock component shows through better, well that roughness is gonna heat up the tire more.
See, these are ALL factors you're not gonna see if you're an underwear model slash part time porn fluffer who's trekking around the Hollywood Hills trying to reassert your machismo after a session of gay-for-pay ass #$%*ing. I can relate to that in a small way, 'cause I rode my bike a couple hours after my vasectomy. Long story. I won't even get into what the pain killers I take for my back are doing for my colon ... once a week. I'd RATHER be doing gay-for-pay porn. Ha ha. Might straighten out the problems with my lumbar spine, to give it a good hammering from the inside surface, that's an angle that even the chiropracters didn't try, back when I was a young guy and having garden-variety back problems. Though, one time I was laying there under some heat lamps, getting a good greasy oily working over from the masseuse who prepped for the chiropracter, who was a real bone cruncher the likes of which so many others never lived up to the standards of let alone the quacks with the stupid spring loaded clicker flicker things #$%*ing rip off that they ALL are put together, maybe if they'd indicated that something would eventually happen that COULDN'T be "popped back in" as though one's back is a game of Jenga blocks ... ugh ... anyway, he said "I'm gonna go and get a vibrator now, and I'll be right back." And believe you me, the warm oil dripping down the crack of my ass suddenly felt rather cold and my head shot up off the padded toilet seat at the head end of the drop-leaf table like I'd been electrocuted with a cattle-prod. Turns out he was talking about a large padded vibratory back massager, probably an adapted orbital polisher. But it still took even longer this time to get the knots in my muscles loosened up. Ha ha.
And I'm not even talking about being an old man. My back was screwed up back in high school, certainly not as bad as now, but that's got less to do with pushing forty and more to do with benching four hundred. Ha ha. Pushing one's limitations AND one's luck. All the same, however you look at it whether you're an old man and it's too late to save your back from further damage 'cause it can't get any worse -or so you THINK- OR, if you're a young guy and you've got a #$%*ing brain in your head so you're going to treat your lower spine as the vital link in the chain of bodily functions necessary to a good rump bumping, either which way you're NOT going to ride a rough stiff suspension set up on your bike. IF you were to go for a hard tail, you'd wanna put some good tall springs on a tractor saddle seat, rather than a plate of steel with a layer of carved leather stuck right on the rails of that hard tail. If you really had to have that hard tail look, maybe you'd go for a Harley soft-tail rear end because of that well disguised suspension system, or better still the BMW /2 type axle with the built in springs, that Amen chopper frames makes, perhaps they've got a hard tail kit you could weld right in. Any which way, I don't know how much time I should spend trying to talk sense into the heads of the type who would put a hard tail on a good superbike era Honda four anyway. But yeah, you wanna take advantage of all the technology has to offer.
And you can't really build the best suspension system with all of this #$%* tucked in really tight. You're compromizing somewhere no matter what. Just because the tire DOESN'T hit the frame doesn't mean you've absorbed the blow. So if the spings are stiff enough to keep that from happening, you're still gonna take it in the ass, somehow or other. And it'll probably be your bike seat pounding your ass up into your lower back that you'll enjoy least of all, far more than a tire rubbing off a bit of paint. As for too large of a hit between an under-rated tire and an improperly set-up sub-frame, well at that point you're gonna have to worry about what type of HELMET you've got. 'Cause the bike's problems are no longer yours, not since the two of you parted company twenty feet back when you hit that bump. Depending on how quick you were going, you've got the next fifty to five hundred feet to think all about it.
-Sigh.
