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Offline Rich205

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Do suspension springs get shorter over time?
« on: 14 June, 2020, 12:35:50 PM »
Hi all,

Apologies if this has been covered before, but couldn't find anything specific when searching.

The bike is a 2007 CBF1000 which has done 35000 miles. Unsure of full service history.

I am quite light at 10 stone, but doing some measurements recently found that when sitting on the bike stationary, the forks sag nearly 50mm. As this is getting on for half the available travel, this ammount of sag must be excessive. I believe around 30mm fork sag would be more appropriate??
The rear needs just one stop off full preload to acheive 30mm sag. At zero preload, rear sag is nearer 60mm.

I cannot think of any explanation for the excessive sag other than the springs have lost some "springiness" over time, and effectively become shorter.

Does this happen?

I am considering replacing the fork springs with Hagon progressive springs (and new oil as I imagine this is well overdue).

I have seen that some people on the forum have mentioned the Hagon springs. How do these perform? Are there other alternative that I could consider? On a modest budget...

Any advice welcome. Cheers.

Offline Art

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Re: Do suspension springs get shorter over time?
« Reply #1 on: 14 June, 2020, 06:37:05 PM »
The front fork springs will wear over time and can shorten by 5 to 10 mm which means they become easier to compress. Also the fork oil can leak out and/or become contaminated by water ingress giving the same symptom of being easier to compress.

If you haven't already download Section 14 of the service manual here and service the front forks.

If the spring length is within the service limit (352 mm (13.9") there is no real need to replace them, especially since your on a modest budget.

Are you adjusting the rear shock absorber in the right direction, page 20 of the owners manual refers.

Offline Rich205

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Re: Do suspension springs get shorter over time?
« Reply #2 on: 14 June, 2020, 08:27:22 PM »
Thanks for the detailed reply.
It's probably worth removing the springs to measure up before ordering new then, and with a bit of luck if they're in spec then a change of oil might sort it, if like you say it's become contaminated or low.

Having double checked, I've been adjusting the rear shock in the correct direction. Assuming that it is getting worn in that case...

That link to the manuals is a great help. They are a step up from the Haynes manual!


Offline g5guzzi

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Re: Do suspension springs get shorter over time?
« Reply #3 on: 14 June, 2020, 08:44:40 PM »
Hi Rich205
I have a mk2 with Hagon springs they work better than my originals.
With the preload adjusters screwed all the way in with the original springs
sag was 45mm. I had a word with Dave at Hagon's and they supplied
springs for my weight with all my riding kit on which is 77kg .
With the new springs in and pre load adjusters set to std setting sag was 35mm.
When fitting the springs Hagon recommended a different oil level and a different
grade of oil 7.5 i think.
I did change the rear shock as well but not at the same time. The fork springs on there own
made a big difference.
The oil level is unlikely to alter the sag or ride height that is down to the spring
and any adjusters or spacers.
You could try fitting spacers but if you need more than 10mm adj  i think you need
new springs.


Malc

Offline Rich205

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Re: Do suspension springs get shorter over time?
« Reply #4 on: 14 June, 2020, 10:28:08 PM »
Thanks Malc, that's useful info.
I'll look at taking the springs out this week for a measure up and if they're short will give Hagon a call to see what they recommend.
Cheers