Topic: Will 14.4" rear shocks screw up my handling?

[mycoal]

1978 CB750K with a 1977 GL1000 front end swap. Would 14.4 inch shocks negatively impact my bike? A friend has spare hagon shocks in that size and I'd probably score them for cheap.

I've heard of people swapping our stock shocks with cb750 dohc shocks, which are longer. I'm 220lbs if that matters. So with my taller front end would taller rear shocks by about 1.5 inches be cool?

[calj737]

My opinion is you'd be fine. While it will distort the factory geometry, likelihood is you won't be riding to the limits of the bike on public streets normally, and thus won't "ride the difference". Also, with your size, I think personally I'd rather have a slightly longer shock for the rear especially if you carry a passenger. But theres really only one way to know for sure how you will like it...

[Kenzo]

Generally speaking you will want to keep the front to rear geometry approximately equal. Probably a good idea to take a few stock measurements. I'd pick a point on the rear of the frame above the rear axel and measure to the floor and another measurement from the steering head.

With the selected rear shocks if it raises or lowers the rear you will want to adjust the forks in the triple trees to match the height change.

Again generally speaking if the front is lowered in relationship to the rear the bike will turn better meaning it's less stable...and the opposite is also true.

When I see the fronts on some of these builds slammed with clip-ons with stock rear shocks no wonder high speed stability is lost. I've never experienced a tank slapper...and never want to.


Cheers,
Kenzo

[mystic_1]

The thing to be aware of is that by raising or lowering the rear, you're changing angle of the frame, which changes the rake angle of the forks, which changes the amount of trail in the steering system.

Kenzo is right on, if you lower the rear you're effectively increasing the rake angle, which increases trail, so slower turning and higher high speed stability.

If you raise the rear you're effectively reducing the rake angle, decreasing trail, so quicker turning and lower high speed stability.



Now, having said that, a one-inch change in the rear isn't going to impact the steering by MUCH but it will definitely affect it somewhat.  Combined with other changes, one can get into real trouble.


mystic_1