Topic: Progressive wound fork springs - which end up?

[puppytrax]

I'm in the process of mating the CB500 aluminum lowers with the CB550 tubes and innards...and I noticed the fork spring is progressively wound...

So...does the tightly wound end go down toward the bottom???   

My 550 manual doesn't say...   

I just did a Q&D polish job on the aluminum; looks OK. Not great, but for only 35 minutes worth of sanding and about 10 mins of polishing [white rouge] and a quick coat of clearcoat, it's better than it was.   

Waiting for seals and dust covers now. And oil; I forgot to order fork oil...   

[MRieck]

Tight coils up.

[puppytrax]

Tight coils up.

OK.   

Now, I am looking at the CB500 fork innards; that spring has the tight coils down...

I understand that the two forks are different; that the position of the coils corresponds to the various ports in the plungers; and that the valving has to match the spring rate at that particular point of compression; and therefore the position of the tight coils is important...but why would the 500 be upside-down from the 550???

[73 CB500 aluminum lowers; 76 CB550 tubes & innards]

[MRieck]

Tight coils up.

OK.   

Now, I am looking at the CB500 fork innards; that spring has the tight coils down...

I understand that the two forks are different; that the position of the coils corresponds to the various ports in the plungers; and that the valving has to match the spring rate at that particular point of compression; and therefore the position of the tight coils is important...but why would the 500 be upside-down from the 550???

[73 CB500 aluminum lowers; 76 CB550 tubes & innards]

I don't know but you generally want the loose coils to be at the point of movement. This applies to valvesprings too though movement is occuring at the top so the loose coils are up. The instructions from Progressive read  "We recommend that the close wound springs be installed up".

[Zip]

It really doesn't matter which way they are put in as long as they are both put in the same way, for absolute balance-sake.

If you think about it, all the movement of the spring occurs inside the fork tube.  The more loosely wound part of the springs will compress first no matter which direction they are facing.  But I also like to put them in loose-side down.  It just 'looks' right to me.  =o)

Zip

[puppytrax]

I don't have the link handy anymore, but there was an explanation on the Bilstein site [car coil-overs] somewhere explaining why it mattered...

It goes something like this: The spring will compress equally along its length, but the tight wound end will "coil bind" and then the remainder of the spring will behave like a shorter, stronger spring...so you want the shock valving to match the progression of the spring compression...more compliant at the beginning (lots of coils; large valve orifices;  presumably lots of movement), and firmer at the end (the tight coils; smaller orifices; not as much movement)...

That's my memory of it, anyway...subject to SRS...   

[MRieck]

I believe your memory serves correct sir. BTW....we have installed different rate springs in fork tubes for roadracing. We have also installed a straight wound in one tube and a progressive spring in the other.

[puppytrax]

I finally got around to printing the CB500-550 Service Manual out...and this is page 155 of the Addendum...

The tight coils seem to be on the bottom...although the text doesn't say, one way or the other...   

[Jugghead]

puppytrax, I have run into the same problem,
I am rebuilding the front forks on a 77 CB550F, and it looks like the manual says tight coils at the bottom.
yet many posts seem to indicate tight coils up top.
I trust MRieck, but I also trust Honda's manual.
who do I trust more?
i can't get it back together unless I know, for sure, how it is "supposed" to be.

[xtalon]

PT,

I put new progressive springs in the GL1000 forks that I mounted on my CB750 (both years 1976) and the instructions that came with my springs say:

'it makes no difference which way the springs are installed'.

It also goes on to say that most manuals will say to put the tight wound end at the bottom, but says this is done because sometimes there will be less spring noise.  'The springs will perform exactly the same regardless of which direction they are placed'.

--xTalon

[RSV12K]

The instruction that came with my Progressive Suspension springs said to put the tight end down expressly because of the noise factor.