Wheel sizes
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From: The Older Gentleman on 3 Oct 2006 02:17 durtdog <pccain(a)bresnan.net> wrote: > If you go a higher diameter in wheel and install a lower profile tire it > might end up feeling the same way on the road. I really dunno never tried > it. Think "unsprung weight", birdbrain. -- BMW K1100LT 750SS CB400F CD250 Z650 GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3 BOF#30 WUSS#5 The bells, the bells.....
From: B-12 on 3 Oct 2006 07:01 Ian Singer wrote: > 1983 GS650GLD Front J19xMT1.85 with 90/90V19 (mine had 100/90v90) If that was the *only* change done to the machine, it would slow the steering down and make it feel slightly less precise. > 1982 GS650G Front J19xMT1.85 with 3.25H19 > Rear J17xMT2.5 with 4.50V17 > (manual says rear should be 4.25H17) If you install a slightly larger tire on the rear and make no change to the front, the front tire has to work harder to stabilize the machine in a vertical position. The machine will steer a little quicker, as the rear end is lifted slightly higher. As any rear tire wears to flatten the rear contour, the front tire has to work harder to stabilize and steer the machine. It wears to a V-shape. As the front tire becomes more V-shaped, the machine becauses less stable. The critical speed at which speed weaves behin is reduced. If you install a slightly smaller tire on the rear, with no changes to the front, you may notice that the rear end feels like it's falling out from under you in a corner. But the rear end is lowered slightly, raking the forks out just a bit more and incrasing the trail. The machine steers slower. > > After putting air in, as all 4 leak, the spares look like they should be > off a chopper as front is really skinny and rear is fat in cross section > looking like it's too wide for rim. That was the look the Japanese manufacturers were trying to achieve with their "L" and "Custom" models. > > No I haven't ridden bike yet as having trouble getting clear title It's hard to describe to somebody what the changes in chandling would be when you change tire sizes, but the above is pretty much what happens. You should know about the effect of rim width on tire contour, though. If you install a new tire on a narrower rim than is optimum (according to the charts on the manufacturer's website) the tire will "crown" as the profile becomes too round and pointy. The machine will steer quicker. The reverse occurs when you install a tire on a rim that is too wide. The steering slows down. > Replacement > tank from the GS650G will not fit as is about 1/2" too long and the > third one I have on order is from an 83 GS1100 and it has not arrived, > and not even sure it will fit. Maybe you can relocate the metal cups on the underside of the tank. The mounting rubbers slide into those cups. The cups are just spot welded onto the tank, but you would have to drill out the spot weld to get the cups loose to move them. This might require a 90-degree drill motor and a really short drill. Another way might be to cut the metal thingumbobs that the rubber mounts slip onto off the frame and reweld them an inch forward or so. But you'd have to be sure the triple clamp and handlebars and other controls wouldn't hit the gas tank at full lock. A bodge to fix *that* problem, if it should occur, would be to make the steering stops on the frame longer by welding a nut on the end. Ted M. should not have read this far, he will need pyschological counseling for traumatic stress if he has done so, as your Suzuki will no longer be a collector's item. ;-) > If it doesn't fit I get the original welded in a shop. Until I can get a tank can't even get it running. Bet > by the time I do it will be ready for snow. I found a very rare 5-gallon gas tank for a 1960's Yamaha production racer which predated Yamaha's very successful TD-1 series. It wouldn't fit the YDS-3 frame I was planning to put it on, so I did surgery on the frame, fabricating new rear gastank mounts and a new seat mount. Nothing was going to stop me from having that beautiful gas tank on my cafe racer... > B-12 was talking about changing wheels inducing wobble. Not sure I > understand why. As long as the rake isn't changed and the tires are > proper size for the wheels what causes it? Speed weaves are often called "speed wobbles". I have written extensively about the subject in this NG, boring TOG terminally. Basically, a speed weave is caused by the front tire not having enough traction to steer and stabilize the machine. The rear tire is much larger, and modern tires have no problem with having enough traction. When I see chopper riders installing 10-inch wide tires on the back of their machines and still keeping a 3.00 X 21 front tire, I have to wonder what is wrong with those guys? The motorcycle cannot have any high speed stability at all, and it cannot turn a corner. All it "wants" to do, is go straight. If a rear tire was wide enough and the RUB couldn't find 40 acres to turn his hawg around, he'd have to whip out his cell phone and call his mom and tell her he wasn't coming home... > Based on road conditions > here, and an ageing back, I need maximum tread on the road. You might want to investigate more compliant rubber compounds then, if your riding style demands comfort, instead of control. I knew a guy who had a business installing 1200cc big bore kits on 883 Sportsters. He was using Conti "Blitz" tires because they had better road compliance. He said that they were "cushy". That's the tread compound making the tire more compliant. When you start getting into compliant rubber, you have to look at the size of the tread blocks and the depth of tread. If you need to ride in the wet, you'll want deep groved tread and small blocks, but if your riding is all dry pavement, such a tire would feel "wiggly" and it would wear in strange ways that I have discussed at length elsewhere. Google for "cupping". If you can get to a motorcycle shop that has an assortment of tires and the salesman doesn't jump right on you trying to sell you something, anything, to get your money, you can *handle* the tires and get a sense of which tires have a softer carcass. Cruiser tires will have a more limber carcass, you can even mount some of them with your bare hands. Go ahead, ask me how I know that. There have been some Michelin tires that had such limber cases, I could turn them inside out! Of course, something like that will have no "run flat" capabilities at all, and may even come off the rim in case of rapid deflation. At the other extreme are sportbike and sport touring tires that have a very stiff carcass. One tire that has both compliant rubber *and* a stiff carcass is Bridgestone's popular BT-4 Battlax tire, which comes in "H" and "V" s
From: B-12 on 3 Oct 2006 09:55 Ian Singer wrote: > Based on road conditions > here, and an ageing back, I need maximum tread on the road. Canadian rock drummer and lyricist Neil Peart wrote a book called "Ghost Rider" where he said that all Canadian roads were either "closed for the winter" or "under construction". or something like that. But highway comfort has a lot to do with setting up your front and rear suspension sag properly. I remember when I first learned what the suspension travel of my front forks was. I thought that if I had a fork with 5.5 inches of travel, I should set the preload adjusters so that the forks extended all the way. I thought that it was more important to maximum full suspension travel over that ONE great big bump than it was to get compliance with the MANY much smaller bumps the wheel was constantly encountering. The conventional wisdom that I was ignoring was that the proper set up involves setting the preload adjusters on the forks(if any exist at all) and the rear shocks so that the weight of the motorcycle uses up about 25% of the travel. And, if your own weight is about is somewhere between 200 and 250 pounds, the combined weights of you and the motorcycle should make the suspension sag somewhere between 1/3rd and 1/2 of the possible travel of whicever suspension unit you're looking at. This setup will give you a comfy ride, but the steering may seem imprecise. I wrote a long screed called "Good Vibrations" over on alt.motorcycle.sportbike a few years ago, and the only response I got was something like, "This has to be a joke?". Most riders have no clue about how suspension frequency affects steering feel and rider confidence versus rider comfort. > I used to > hate it when I rode 15 years ago and suddenly the freeway would be > grooved when cruising at 70 mph. A lot of front tires had a center groove that would interact badly with grooves and section lines. Dunlop eliminated center grooves and supplied tires with large diagonally transverse tread blocks in the K291/391/491/591 series. That solved *one* problem, but the typically stiff Dunlop carcass prevented the tread blocks from moving freely, and the tires cupped and scalloped and then they wiggled... > Luckily they seem to have stopped that, > but then there also was the problem with the cracks being patched with > that tar that stays super slick. Just what I don't need. Tar snakes are no fun. The nature of tar is that it is a supercooled liquid. The surface hardens, but the asphalt under the surface remains semiliquid at ordinary highway temperatures (maybe as high as 140 degrees during the California summertime) and the tar *shears* diagonally when a rider tries to corner across a lar snake.
From: chateau.murray@btinternet.com, on 3 Oct 2006 10:45 B-12 wrote: <snip> > > > I used to > > hate it when I rode 15 years ago and suddenly the freeway would be > > grooved when cruising at 70 mph. > > A lot of front tires had a center groove that would interact badly with > grooves and section lines. France used to ue those damn grooves on their autoroutes. 'Rainurages', they were called, and some bikes used to dance the hokey-cokey on them. Haven't seen them for at least 20 years, though: I think the French relaised they were a bad idea. > > Luckily they seem to have stopped that, > > but then there also was the problem with the cracks being patched with > > that tar that stays super slick. Just what I don't need. > > Tar snakes are no fun. The nature of tar is that it is a supercooled > liquid. The surface hardens, but the > asphalt under the surface remains semiliquid at ordinary highway > temperatures (maybe as high as 140 degrees during the California > summertime) and the tar *shears* diagonally when a rider tries to > corner across a lar snake. "Overbanding" we call this, in the UK. We don't have the problem of 140 dgeree heat (you'll be surprised to hear!) but we do have the problem of rainwater on overbanding, which makes it slippery as all hell. For this reason, there are very strict guidelines that road menders must adhere to, covering total length of any single overbanding strip, maximum permitted width, etc. Successful prosecutions and claims have been made against local councils that broke the guidelines and caused motorcyclists to crash.
From: Larry Blanchard on 3 Oct 2006 11:58
B-12 wrote: > GS-450's were very popular at the time, riders could run them wide > open, flat out, at about 110 mph and humble riders of much larger > machines. > > Don't ask how I know that... Nice to know. I just bought an '83 GS450L :-). Yes, the one that had been sitting. I've been running B12 in the gas, but I haven't ridden it enough yet to get it completely clean. But it improves a little with each ride. BTW, was this bike known as cold-blooded? Seems I have to leave the choke at least partially on for several miles. Or is that just another manifestation of the dirty carbs? And as long as I'm asking questions, I read somewhere that all of the GS group shared many common parts. Does anyone know of a website that covers these equivalencies? -- It's turtles, all the way down |