Re: "CBass" -- Yamaha Virago XV750 Cafe Build
T.Stanley said:
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I used the old string and weight method at various points to measure and when all said and done, the rear wheel is about 9mm from center of frame which is about 3/8 inches. I asked several custom bike frame builders and a retired F1 engineer who also served on several pit crews for superbikes in the 90's regarding my rear wheel being off center to the left by 9mm's...... they said unless I was tracking my bike competitivly, then that I was to enjoy my project build and ride it. Frankly it's more of a fun/looker rather than "performance".....obviously.
...................................................................my edit - Beachcomber
This offset track subject is a Red Herring ............. BMW have been offsetting their rear wheels for years - ON ROAD BIKES.
The BMW Kay range uses IDENTICAL frames and swing arm setups for the cooking tourers through to the RS / sports models K75 / K100 / K1100.
The rear wheel widths vary from 3" to 5.5" !!!!!!!!!!!!! There is a slight offset in the wheel casting for the larger widths, but never the less the offset according to the OEM workshop manual is around 3/8".
There is NO requirement in Europe for either construction and use [ official build regs ] OR our annual MOT / TUV / Service des Mines tests for the front and rear wheel to be on the same axis. They HAVE to be parallel of course.
I first discovered this when I was building my K100 Steetfighter and as an auto design engineer of some 45 years standing was horrified. To the point where I was going to re-design the frame pickups to move the power train over to compensate for the much wider [ 2.5" ] rear wheel. Fortunately I hooked up with a guy from the BMW comps dept. who put me straight before I got into it !
Initially I took things very nervously, but soon realised that it had made not the slightest affect on handling or tracking. The bike was eventually used as a test mule for the RAM shox and was ridden to very respectable speeds on a closed race circuit. Road or track makes NO difference, just seems weird.
Ben Kingham [ BMW K100 ] is currently running [ and winning ] in the BEARS race series with a K100 modified using the same wheel set up as my Fighter - and RAM shox !
Here's my initial checks from stock 3" wide wheel to the 4" - later switched to 5.5" [ see next pic for Ben Kingham's example ]