Which side up Hyperpro progressive spring ST1300

Hi there,
I'am currently installing a Hyperpro kit on myST1300. The instructions manual says that the progressive side of the rearspring (usually) needs to be on top. However, in my case the lower (non-progressive) side of the spring will than not fit over de bushing of the steel springseat at the bottom of the shock. If I turn the spring upside-down (progressive side down), it fits perfectly over the bushing of the spring seat. However, I am almost 99,9% convinced that this is not the proper set-uup. I think it is just a matter of removing some paint from the inner-side of the spring. So my question is if the progressive side of the spring needs to be on top. I already adressed the issue with Hyperpro yesterday, but will not get a response from them probably later this week. I am in somewhat of a hurry to put the bike back together again, so I'am hoping on a response from here. Regards. Rene.

I don't really think that it matters which direction the spring is as long as it fits. I wouldn't remove any finish from the spring or bushing.

Interesting question Rene, and I think you may get conflicting advice so may be best to wait for HPro.
My own thoughts is it will make little difference to how the spring will operate, the progressive spring works by reducing movement when the tightly wound end stops compressing under load, I think. So why would this be any different top or bottom. C of G will be lower if heavier end is nearer the ground. Would unsprung weight be affected?
Hope it helps.
Upt'North

Thanks for the quick resonse. Looking at the HP spring: it has 'Hyperpro' lasererd onto it. In order to read it, the spring needs to be installed with the progressive side up. Just to be sure, I'll follow the advice of Upt'North and wait for HPs rersponse.

The only time spring orientation matters is inside the forks, where the spring displaces oil. The spring will displace more oil with the tight coils on the bottom, and less oil the other way around. If you fill by volume then the orientation matters because one way will provide the correct final oil level, the other will not. If you fill the oil by level then either orientation is OK.

For a rear shock operating in air, the spring can be installed in either orientation. It compresses from both ends, so it cares not which end is which.

OK I do not know the answer but can you post pictures and opinion of results ? I have really been thinking of doing this mod

I don't know if this will help but I dug up an old photo of when I installed a Hyperpro rear shock on my bike.

It doesn't matter much but the reason the progressive end goes up is that it reduces unsprung weight.

Where on the spring does it transition from sprung to unsprung weight?

I understand what you're saying I just can't picture it.


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dwalby said:

For a rear shock operating in air, the spring can be installed in either orientation. It compresses from both ends, so it cares not which end is which.

Click to expand...

Makes sense.

dduelin said:

It doesn't matter much but the reason the progressive end goes up is that it reduces unsprung weight.

Click to expand...

Makes more sense. I'd think the weight difference insignificant but with higher frequency of movement it's effect is greater than I'd imagine?

Thnx for all reactions. Got word from Hyperpro today. The ST1300 is the exeption to the rule. The rear spring should be installed with the progressive side down. Also I wondered why Hyperpro advises an airchamber in the front forks of 160 mm versus Honda's advise of 62 mm. The answer I got from HP was that their front springs also need to be installed with the progressive side down. This changes (like Dwalby already mentioned) the way the forkoil is displaced en therefore less oil is needed. I'll post some pictures once the job is finished. Testresults will have to wait. It's winter overhere and I'am not a big fan of riding in freezing temperatures. However, many ST1300's and 1100's in the Netherlands have had this modification done and all owners, without exception, are very pleased with the endresult. There's a lot of info to be found on this topic on the Dutch ST forum (https://st1100-1300.eu/).