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Discussion Starter #1
I'm working on my XV920 today and making some chassis changes, including a new swingarm and front end....not to imply that these changes will be done today haha.
I'm measuring the wheelbase at right shy if 60", and while I'm not trying to build a track machine I'd like it to handle well. It steers quite lightly now and for all that it is a standard with a fairly rakey front end it's tossable. I have ample upper body strength and that my play in, however....

I'm working on my new swingarm mount(s) for the cbr900rr swingqarm. Besides being beefy and neat looking it does not require an upper shock mount so it can be a clean instal. It will end up also cutting ~1" off the wheelbase. Also being added this time around is the front end from Suzuki TL1000r. To aid in this I'm swapping to modified motor mounts that will essentially result in a steering head drop of around 2" with reference to the original engine position., the combination of which will yield a cumulative steering head angle of around 25* give or take a red one. The steeper front end will also knock what look like ~1.5 inches off the wheelbase. At this point I have the TLR wheels, a set from an 07 R1 or the swept 6spokes from a CBR600rr that also includes the 5.5" rear on which I'd run a 170 vs the 190 on the other sets.

Long way to a short question: What are your collective thoughts on the effect of wheelbase on a street bike's handling. As I said, it was acceptable (if mushy) previously, and I anticipate even quicker turn in and transitions when it's back together.
 

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You lost me with the motor mounts affecting the steering head angle...

But a shorter wheelbase should make it easier to change direction vs long wheelbase.

I'm not sure about the rest of the front end/wheel swap.

I think a typical sport bike has a wheelbase closer to 55".
 

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You lost me with the motor mounts affecting the steering head angle...

But a shorter wheelbase should make it easier to change direction vs long wheelbase.

I'm not sure about the rest of the front end/wheel swap.

I think a typical sport bike has a wheelbase closer to 55".
 

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I've careened around on a 45" wheelbase at stupid speeds. Near as I can tell, the wheelbase sets the required lean angle for a given turn at a given speed, getting the trail right determines stability at a given speed, fork angle is voodoo to me if you have the trail right as far as what it'll do.
 

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I've careened around on a 45" wheelbase at stupid speeds. Near as I can tell, the wheelbase sets the required lean angle for a given turn at a given speed, getting the trail right determines stability at a given speed, fork angle is voodoo to me if you have the trail right as far as what it'll do.
 

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Discussion Starter #6
FR: The 81 VX920R has the motor hanging from a pressed steel backbone, it's a loose copy of a Vincent. All else being the same, by dropping the front of the upper frame and raising the back, where it bolts to the cylinder heads, it'll effectively drop the steering head and steepen the angle. Think of it this way, cut off a 24" chunk of 2x4 with the ends cut at square (0* off vertical) then prop one end up on a 2" chunk of whatever. Now the cumulative angle of the higher end, with reference to the bench top is not 0* but has skewed over to (can't remember my trig) something around 10* for the purposes of just picking a number. Now say you swap that two inch chunk of frozen moose vomit you've propped your lumber on to a pack of smokes laid on it's side ~1"......now that previous arbitrary 10* before is something like 5*, again arbitrarily chosen because I've forgotten the math. Clear as mud?

I stole the idea from Turbodog who posts here now and again and has done a similar mod to his. It would be temporary as I have plans for a nifty trellis style upper frame I'd like to weld up this winter that will accomplish all this and a few other things much more cleanly and around 20 pounds lighter than the stock steel frame.

My R1 had a 55"wb, the SuperIII was something like 57-ish and while somewhat portly it turned in just fine. I don't have a clue what something like a GS750, cb750 etc spec at but I believe they are also in the 60" range no? I guess my question was more along the lines of: has anyone shortened the wheelbase of their bike significantly and did you note any major drawbacks when ridden on the street?
 

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Discussion Starter #7
FR: The 81 VX920R has the motor hanging from a pressed steel backbone, it's a loose copy of a Vincent. All else being the same, by dropping the front of the upper frame and raising the back, where it bolts to the cylinder heads, it'll effectively drop the steering head and steepen the angle. Think of it this way, cut off a 24" chunk of 2x4 with the ends cut at square (0* off vertical) then prop one end up on a 2" chunk of whatever. Now the cumulative angle of the higher end, with reference to the bench top is not 0* but has skewed over to (can't remember my trig) something around 10* for the purposes of just picking a number. Now say you swap that two inch chunk of frozen moose vomit you've propped your lumber on to a pack of smokes laid on it's side ~1"......now that previous arbitrary 10* before is something like 5*, again arbitrarily chosen because I've forgotten the math. Clear as mud?

I stole the idea from Turbodog who posts here now and again and has done a similar mod to his. It would be temporary as I have plans for a nifty trellis style upper frame I'd like to weld up this winter that will accomplish all this and a few other things much more cleanly and around 20 pounds lighter than the stock steel frame.

My R1 had a 55"wb, the SuperIII was something like 57-ish and while somewhat portly it turned in just fine. I don't have a clue what something like a GS750, cb750 etc spec at but I believe they are also in the 60" range no? I guess my question was more along the lines of: has anyone shortened the wheelbase of their bike significantly and did you note any major drawbacks when ridden on the street?
 

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The XV had leading axle forks to reduce trail, fitting USD with yokes pulled back (less offset) will increase trail.
Tilting steering head to steeper angle should restore everything close to stock trail but with shorter wheelbase
 

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The XV had leading axle forks to reduce trail, fitting USD with yokes pulled back (less offset) will increase trail.
Tilting steering head to steeper angle should restore everything close to stock trail but with shorter wheelbase
 

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Discussion Starter #10
This one has non-leading forks, but fairly deeply offset triples so same effect.
 

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Discussion Starter #11
This one has non-leading forks, but fairly deeply offset triples so same effect.
 
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