| Author | Message | ||
     Gentleman_jon |
I had previously upgraded my suspension by having Trackside Engineering install heavier springs and re-valve both the rear shock and the front fork. This was a big improvement on my old XB9S, but when I got my new bike, an XB 12S with the Hals long wheelbase competition chain conversion swing arm , I moved the modified suspension units to the new bike. However the rear spring was not strong enough to set a proper sag of 32mm: the minimum I could get at full preload was 47mm.  I faced the alternative of re-springing and re-valving the Buell shock again, or going to a new one. When one of our brothers offered to buy my old shock, my mind was made up for me, and I ordered an Ohlins shock, type number 46HRCLS for Buell XB. (With Ohlins, the type number is not a part number, it is a description of the type of shock., so you have to specify the model of the bike it will be used on as well. ) I also considered the Penske, and several other shocks, but I selected the Ohlins because of price, free spring exchange, remote preload, adjustable ride height, resale value, and yes, looks. The fact that Buell uses Ohlins on the XBRR was another factor. I am not sure if the shock I have is the same as the one used on the XBRR but it looks like it might be. The first thing I did was discuss the matter of spring rate with Ohlins. We agreed that even though I weigh 235# in gear, we would use the spring that was in the 250 -275# range to compensate for the longer swing arm. The spring selected was the #1092 -34. Luckily this worked out well, and we were able to dial in the desired sag with in minutes, using the remote preload adjuster I had been recently doing some suspension tuning with the bike, and felt that I h ad a pretty good set up, even though it required 45-47mm of sag. That meant I was loosing about 1/2” of spring travel. Not a disaster, but so not good either. So before doing the install, I put some masking tape on the bike, front and rear, and then with me aboard, my long suffering friend and accomplice, Gerry, measured equal height points on the chassis to establish the “attitude” of the bike when loaded. This is an important reference point, as it records the existing fork angle and trail, without actually measuring it directly. The install was very straight forward, the part fit, ( with one small exception), everything needed was included, and I was able to do it single handedly in about two hours, the first time. I would say an experienced mechanic could do it in half that time, as usual. Because I have an Firebolt tail on a Lightning, there was no room under the seat to mount the Ohlins remote reservoir which is a lot larger than the stock unit. So I mounted both the remote reservoir and remote preload under the under tail as per the Ohlins instructions. I am not too happy with this location, since both units will get covered in road dirt thrown up by the rear wheel. I plan to add a carbon fibre extended hugger from American Sport Bike in the very near future to provide some protection for the reservoir and adjuster. After installing the shock, I adjusted the front preload to get 35mm of sag. At the rear, we set the sag for 32mm with the remote preload adjuster, and left the shock settings as supplied by Ohlins: 14 turns out on the compression, and 15 turns out on the rebound, ( I think these settings are approximately the middle of the range). Finally, we lengthened the ride height, by adding about 1/2” in rear ride height to get back to the same “attitude” that we had initially measured to use as a reference point. I was extremely glad we had established this reference point. I wonder if a for and aft inclinometer as used on a racing sailboat might be an interesting item to fit to a bike? I was hoping that , with no further tuning, the handling on the initial test ride would be at least as good as my old set up. Frankly with all the changes, I was afraid it might not be. To my surprise and delight, I was able to convince myself that the handling had been noticeably improved right from the git-go. Turn in seemed easier, the bike seemed more securely planted in mid turn, and it doesn’t tend to go wide at the exit. Hopefully a bit of fine turning of the damping will make it even more satisfactory.  There was one small snag in the install. When I restarted the bike for the first time after my initial test ride, the engine light came, in spite of the fact that everything appeared to be working just fine. Don’t you just hate that? I got out the shop manual, and did a quick trouble code check, and discovered that the sticky finger of suspicion was pointing a the the fan. No surprise there. Part of the installation requires putting 3/16” spacers under the fan mounting screws to rotate the fan forward just a little bit, to allow for a little clearance around the Ohlins shock which is rather bigger than the stock part. Unfortunately the supplied spacers did not provide enough room, so the shock touched the fan surround and caused the blades to bind. This caused a the fuse to blow as the fan attempted to start itself at the end of my test ride. Of course it took as long to figure this all out as it did to do the original install, and I am sure it would have taken a lot longer had not another one of my riding buddies, Peter, dropped by offering help and encouragement. Always nice to have a helping hand, isn’t it? We cured the problem by replacing the 3/16” nylon spacers with 1/4” ones from the hardware store and slightly longer 1/4-20 allen head stainless screws, and sanding the tips of the fan blades a bit to ensure clearance when the bike is running hot. Bottom line: a somewhat pricey but worthwhile modification, especially for the heavier rider with the longer Hals swing arm. PS: The brother who started this whole process, went on to wad his bike, so my modified Bull shock is still for sale. Please check the classified for this, and lots of other great Bull parts and cool black helmets at great prices. PPS. Suspension in general is one of the last great mysteries in this world. One of our brothers, Spuds, posted this link to a very useful guide to understanding the basics of it. http://www.gostar-racing.com/club/How_I_set_up_my_motorbike.pdf (Message edited by gentleman_jon on January 14, 2007) | ||
| Buellshyter |
You have the extended swingarm but I assume your original rake is the same. On the SS, which utilizes an extended swingarm, the rake and trail is different then on the S and R. Is there any correlation between the wheelbase of a bike and it's rake and trail? In other words, when Buell extended the swingarm on the SS model could they have left the front end alone or did it require alteration? | ||
| Gentleman_jon |
Interesting question Rick. The original XB design, has a very extreme geometry, said to resemble nothing as much as a 250cc GP motorcycle. I have never been able to understand why this is thought to be a good idea for a machine with almost five times the displacement and twice the weight, or even, why it works at all. It is not used on the 990cc Moto GP bikes, which tend to have longer wheelbases, greater fork angles and more trail, I believe. Various anonymous posters have alluded to little known elements in the design of the motorcycle's dynamics that enable the short wheelbase bikes to handle as well as they do. I suspect that these elements have to do with the location of the center of gravity, the well known mass centralization, the peculiar swing arm pivot and belt tensioner arrangement, and the oddly steep fork angle and minimal trail. Exactly how these, and other, "secret" parameters work and interact, remains a Buell trade secret. One thing that I know for sure, is that more than a few racing riders have complained about the lack of stability of the bike for road racing. Solutions to this include lengthening the wheelbase, ( Hal's chain conversion), and increasing the fork angle, ( Adrenaline Racing), or both, (Buell XBRR), The Ss models have a geometry that can best be described as much more conventional, with wheelbase, fork angle and trail figures being very much industry standards. My bike is sort of a hybrid. It has the front end of the short wheelbase models and a longer wheelbase. In addition, it has an Ohlins steering damper which stabilizes the front end. I am sorry for this overly long answer to your rather simple question. More simply put the answer would be "yes and no". That is to say, they could have left the front end alone when they extended the swing arm, as is the case with all of the machines that have the Hals chain conversion, including mine, and no, it didn't require alteration, but someone at Buell thought it would be a good idea to offer a bike with conventional dimensions, and I agree. The XB12Ss is a very stable, good handling bike, and I think more suitable for larger riders. OK? | ||
| Lonexb |
my head hurts.  | ||
| Gentleman_jon |
Sorry Brian, I know exactly what you mean!  | ||
| Saintly |
little known elements in the design of the motorcycle's dynamics that enable the short wheelbase bikes to handle as well as they do...... I suspect that these elements have to do with the location of the center of gravity, the well known mass centralization, the peculiar swing arm pivot and belt tensioner arrangement, and the oddly steep fork angle and minimal trail. Exactly how these, and other, "secret" parameters work and interact, remains a Buell trade secret. Jon, this is no longer a secret! I have discovered the cause of the buells stability: There is a very strong magnet in the Buells frame right behind the fuel cavity. This magnet is attracted to the Earths core and thus "plants" the buell to the road surface via this magnetic attraction! Seriously! That is how it's done. If anyone does not believe me, simply take a sawz-all and cut your frame in half. You'll see the magnet that I'm talking about. P.S. Don't confuse the magnet with the GPS transmitting device which is just to the left of it. That device is used to constantly monitor the location of Buells world-wide and transmit this data to Skylab(which by the way, did not fall! That was a government created myth/conspiracy.) | ||
| Gentleman_jon |
OUTSTANDING!!! Ladies and gentlemen, ain't Bad Web grand? Not only has Fritz designed his own chain conversion at less than the price of a new belt, he now fearlessly reveals the secret of Buell roadholding: MAGNETISM!! To be perfectly frank, I suspected it was something like that all along. Now we know why so many brothers have had problems removing their spark plugs - the damn magnet is holding them in! Thanks for connecting the dots, man. I think the entire Buell community owes Fritz a debt of gratitude for cutting his bike in half to prove his brilliant theory. Uh, you did cut your bike in half, didn't you, Fritz? PS. Thanks for the heads up on the Skylab thingy. I never went for that falling out of space story: sounded too fishy at the time, am I right my brother? PPS. Have you figured out how to hook up the GPS to a Palm Pilot yet? |
