Topic: Lets talk shocks... CB 550

[A Grove]

Hey all,

I am starting my Cafe' build (1975 CB 550) and have come across some killer shocks in my dads basement.  He used to build custom downhill racing chairs, etc. and we have a few racing shocks left that would work very well for the dampening, etc. on my 550.  My question to you... I was under the assumption that adding  longer rear shocks is going to give it a move "racey" feel.. and that is indeed what I want.  I measured my stock shocks under sag at 11" E2E (eye to eye).  I had been told stock was 13".  Can this be confirmed?  Could the sag and useage have wore out the shocks that they are sagging more than they were 30+ years ago?  Also... What would a good, proven E2E be to get a race-like feel out of the bike.  Common sense places it too that by raising the rear end, you are in turn steepening the head angle which in turn makes it react much quicker.  This is what I like to hear!!


Please give me your input.

Thanks!

[A Grove]

Bumping to front page...

Are my questions dumb?  It seems everyone else gets length, speedy replies to their topics, and the past few I've posted have hardly got any at all.  I appreciate those who do!!

[Gordon]

Don't know the exact stock length of the shocks, but the length is always stated as measured at full extension, not under load.  The length at full extension will not change due to wear or age, so measuring your stock shocks should give you an accurate basis to start from. 

The "racey" feel you're talking about is due to raising the rear end in comparison to the front.  This changes the steering angle, puts more weight at the front and quickens the steering feel.  You can also achieve this same effect by raising the forks in the triple tree while leaving the rear the same.  Switching to lower handlebars like drag bars, clubmans or clip-ons will also move your center of gravity farther forward and increase this effect.   

A couple of things to consider when raising the rear end are the lean angle when on the side stand and getting the rear tire off the ground when on the center stand.  Also, if you're not gifted in the inseam department you may have trouble getting both feet on the ground. 

[A Grove]

Gordon - Thanks much for the detailed response!  It pointed out a few issues I hadn't thought about when the idea game about of jacking up the rear-end. 

One question about moving the forks up in the triple trees... Won't that be causing a very horrible feel/noise/over all things when/if the fork were to bottom out?  It would be bottoming out on the lower crown rather than the internal bumper (assuming these forks HAVE internal bumpers..)

Thanks

[Gordon]

One question about moving the forks up in the triple trees... Won't that be causing a very horrible feel/noise/over all things when/if the fork were to bottom out?  It would be bottoming out on the lower crown rather than the internal bumper (assuming these forks HAVE internal bumpers..)

I'm not really sure what you're asking here, but raising the forks in the triple trees doesn't have any effect on how the forks work.  All you're doing is changing the mounting position of the clamps. 

[TwoTired]

I measured my cb550 shocks at 12.5 inches eye center to eye center. I measured my cb750F shocks at 13.25 inches eye center to eye center.
These are fully extended measurements.
Collapsed length is 10 inches for the 550 (2 1/2 inch stroke)  And 10.25 inches for the 750F (3 inch stroke)

The sag you refer to, has to do with the spring rate and how many pounds it supports under compression.

I like the to have the shocks or suspession at two thirds extension with the weight applied while driving.  This allows the suspension to compensate for bumps in the road and depressions in the road surface, mostly without hitting the shock's end limits.  Further, when leaned over, side G loads are higher than straight up weight.  So, the springs compress more and the shock is at a lower part of its travel range.  I still want some travel excursion, so as not to hit the shock end limits, which could lift the tire off the road surface, or at least reduce the tire contact traction.

As to shock height changing the steering.  Yes, to an extent, it makes it less stable.  But, it's not just the shocks.  It's the spring weight and tire height, too.   Less stability may also bring head shake/wobble into the realm, too.  And chain adjustment becomes a bit more difficult to get right as the swing arm is farther from it's straight back positioning, with the chassis raised up further.

But, I'm no cafe expert.  I'm sure those guys will tell you I'm full of #$%*e.   

Cheers,

[A Grove]

Thanks for the info, guys.  If I have any further questions, I'll report back...

EDIT:: One more...

Does anyone know the travel for the front fork on a stock cb550?

[ieism]

I just finished putting Koni´s for a 750 on my 550.
I polished them and powdercoated the springs, they look very good now. The bigger Koni´s look much better than the small ones I have on my other 550, they´re not just longer the whole thing is just bigger.

I didn´t really measure as the bike was on a lift at the time. Just by eye balling it it looked like the new shocks were 3 to 4 cm too long.

I just compressed them in a woodworkers vice, and strapped something around the spring to keep it compressed. Then I installed it and released the strap. I´m not sure getting them off again is possible, as they are sort of stuck now.

I haven´t tried them on the road yet, as my motor is not done yet. They feel way harder than the old springs, and the back is visibly higher. It looks better in my opinion, but it´s not going to be a very comfortable ride i´m sure.
I have really firm race suspension on my commuter bike too, and you get used to it.



Lowering the forks will make the bike steer quicker too, but it will lower the whole bike. I didn´t want my bike to be any lower than it already is as I´m pretty tall.

[A Grove]

What I am saying about lowering the forks is that there is only so much you can move the forks up in the triples, otherwise when the fork bottoms out, it'd be hitting on the crown.  does anyone know how far it is possible to move the forks up/drop the frame w/o bottoming on the triples?