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Does it matter which way up this spring is?

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UnspeedySam
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Joined: 26 Nov 2009
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PostPosted: 21:40 - 18 Aug 2017    Post subject: Does it matter which way up this spring is? Reply with quote
As you may have seen in the "What have you done to your bike today?" thread, I started rebuilding my Bros forks last weekend with some CBR600 F3 cartridge internals bought from the boot of a car at Fleet services.

I had to stop last week because I didn't have the right copper washers, but one of the forks is together with no oil and the other is ready to go back together.

My question is whether it matters which way up (it is more tightly wound at one end) the little rebound spring at the bottom is, and if anyone fancies explaining the science behind why or why not?

For bonus points, the same question for the main fork spring!

Thanks! Thumbs Up

Here's the page I'm using if anyone is interested: https://www.hawkworks.net/tips/F3forks/F3forks.html

https://www.hawkworks.net/tips/F3forks/F3forks1.jpg
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Riding: Does an Audi estate count?
Fixing: Honda VFR750 RC36 '94 and MZ ETZ 251 '90
Gone: ZZR600 '00, TRX850 '97, RXS100 '93, JS125-6B '07, BMW R1100RS '93, Kawasaki ZX-6R-J2 '01,Honda Bros NT400 NC25 '88
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Ste
Not Work Safe



Joined: 01 Sep 2002
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PostPosted: 21:50 - 18 Aug 2017    Post subject: Re: Does it matter which way up this spring is? Reply with quote
UnspeedySam wrote:
some CBR600 F3 cartridge internals bought from the boot of a car at Fleet services.

As you do. Laughing

Part #17 has the more tightly wound end at the top.

I'll pass on #4, the rebound spring. At a guess it's going to be the opposite way around as it's for rebound but I wouldn't want to bet on that.

Realistically, I don't think it'd make any difference as long as both forks are assembled in the same way.
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UnspeedySam
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Joined: 26 Nov 2009
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PostPosted: 21:57 - 18 Aug 2017    Post subject: Re: Does it matter which way up this spring is? Reply with quote
Ste wrote:
UnspeedySam wrote:
some CBR600 F3 cartridge internals bought from the boot of a car at Fleet services.

As you do. Laughing


He was breaking a bike in Croydon (I'm in Southampton) and when I went to pick up the bits he didn't have time to strip them off the bike. So he met me half way as an apology. So not quite as dodgy as it sounds. Razz

Ste wrote:

Part #17 has the more tightly wound end at the top.

I'll pass on #4, the rebound spring. At a guess it's going to be the opposite way around as it's for rebound but I wouldn't want to bet on that.

Realistically, I don't think it'd make any difference as long as both forks are assembled in the same way.


Interesting. I think the tightly wound bit was down on the main spring for all 4 forks I stripped down (but I could be wrong...I didn't take many photos...). So I put in both springs (main and rebound) with the tightly wound bit pointing down when reassembling.

But when stripping down the right side after I'd put together the left already, I noticed that the rebound had the tightly wound bit pointing up and main spring tightly wound pointing down which is what made me ask the question.
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Riding: Does an Audi estate count?
Fixing: Honda VFR750 RC36 '94 and MZ ETZ 251 '90
Gone: ZZR600 '00, TRX850 '97, RXS100 '93, JS125-6B '07, BMW R1100RS '93, Kawasaki ZX-6R-J2 '01,Honda Bros NT400 NC25 '88
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Suntan Sid
World Chat Champion



Joined: 07 May 2009
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PostPosted: 00:17 - 19 Aug 2017    Post subject: Reply with quote
A fork spring with gradually tighter coils is a "progressive" fork spring

Quote:
A Progressive Rate Spring has the advantage of a rising rate resistance to compression. The benefit of this is that the spring can be soft enough at the start of the travel to offer a "plush" ride, yet be firm enough at the end of the travel to soak up the big bumps.


For the main spring, 17, the tighter coils need to be uppermost, not sure about the rebound spring!
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UnspeedySam
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Joined: 26 Nov 2009
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PostPosted: 00:18 - 19 Aug 2017    Post subject: Reply with quote
Suntan Sid wrote:
A fork spring with gradually tighter coils is a "progressive" fork spring

Quote:
A Progressive Rate Spring has the advantage of a rising rate resistance to compression. The benefit of this is that the spring can be soft enough at the start of the travel to offer a "plush" ride, yet be firm enough at the end of the travel to soak up the big bumps.


For the main spring, 17, the tighter coils need to be uppermost, not sure about the rebound spring!


Balls. I guess I'm getting that fork apart again then and trying not to bugger the bushings.

edit: I might just leave it and do the other one the same...not sure...

edit: Wait I'm an idiot. I don't need to split the fork to take that spring out... Rolling Eyes
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Riding: Does an Audi estate count?
Fixing: Honda VFR750 RC36 '94 and MZ ETZ 251 '90
Gone: ZZR600 '00, TRX850 '97, RXS100 '93, JS125-6B '07, BMW R1100RS '93, Kawasaki ZX-6R-J2 '01,Honda Bros NT400 NC25 '88
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