Wheelbase

[chizler62]

Looking of Wheelbase info for different years and for custom hardtails etc. I'm doing the trigonometry to come up with a chart for Headtube angle vs wheelbase vs fork tube spacers vs frame clearance vs wheel sizes. With this I'll be able to ensure consistent performance regardless of rider size and needs.

What's your Wheelbase and year for stock frames and swing arms? Wheel sizes?

What's the Wheelbase of your hardtail? Any extention? New headtube angle? Fork spacers? Wheels sizes?

thoughts of how your bike handles?

 

[XSLeo]

In my factory books the early frames, 70-73 had a 55.5 inch wheel base, the 74 up bikes had a 56.5 inch wheel base.
In 74 they made a lot of changes to the frame to help the weaknesses of the early frame. This included a longer swing arm.
These specs where the same with both the 18 inch rear and 19 inch front as with the 16 inch rear 19 front. Spoke or mags.
All years used a 19 inch front, on the rear the early up to 80 or so the standards used a 18 rear. The Specials used a 16 rear.
On the hard tails I can't say but I bet you get a lot of differences on the specs.
Leo

 

[chizler62]

Thanks, I didn't understand the numbers I read off reference material. The HeadTube angle changes as the antisquat, trail etc.....when you put a 16" wheel on. Especially the wheelbase with suspension sagged. But they post it the same?

A mechanic at a local Yamaha dealership ask me to make a bunch of 35mm Fork spacers. So his XS buddies could install and see which length they'd like the looks of best.
since they sell me oem parts at straight cost. I opened my mouth and told them I'd make a chart that'd give them rake,trail and ground clearance too.
which isn't hard.....if you have confident numbers to plug in!

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[TwoManyXS1Bs]

We've had a few inquiries along this line. These beat about the bush a bit:

http://www.xs650.com/forum/showthread.php?t=28717
http://www.xs650.com/forum/showthread.php?t=29346
http://www.xs650.com/forum/showthread.php?t=29362
http://www.xs650.com/forum/showthread.php?t=31064
http://www.xs650.com/forum/showthread.php?t=34693

 

[XSLeo]

If you pull of a 110/90-18 and install a 130/90-16 you won't change anything too much. The 110/90-18 stands about 25.7 inches tall. The 130/90-16 stands about 25.2 inches tall. The difference in the over all height of the tires is about 1/2 inch. This would move the axle about 1/4 inch.
Is lowering the axle 1/4 inch going to change things that much?
The same works with going to a 300-21 at 27 inches tall vs a 100/90-19 at 26 inches tall. This lifts the front axle 1/2 inch.
I don't think these changes will effect anything enough to notice.
Leo

 

[chizler62]

The wheel diameter is important. Heres an example.

I've noticed that the trail numbers offered up by XS builders is wrong.

Trail is calculated

Trail=Wheel Radius * SIN(90- Head Tube Angle) - Fork Offset

Not, as I see here.

Trail = Wheel Radius/ Tan( Head Tube Angle) - Fork Offset/ SIN(Head Tube Angle)

using the wrong math will lead to larger than reality trail numbers too steep head tube angle(rake) resulting in a squirrelly bike!

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