Author Topic: Fork Springs  (Read 342 times)

Offline RogerSB

  • 1960 Golden Flash, Plymouth, Devon, England
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Fork Springs
« on: 15.10. 2018 17:48 »
Hi all, I'm looking to overhaul my s/arm Golden Flash's front forks this winter and, as I'm often 2-up, I'm thinking I may be better off fitting progressive springs.

Paul Goff's website calls them multi-rated and says fit with the tighter coils at the top, SRM calls them progressive and says tighter coils at the bottom. Can anyone with experience of these springs throw any light on it?


1960 Golden Flash

Online RDfella

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Re: Fork Springs
« Reply #1 on: 15.10. 2018 17:58 »
No experience of multi-rate springs, but am often surprised by the number of coil springs fitted in what I consider to be the wrong way. Asymmetrical springs are normally fitted with the closer coils closest to the end with least movement (eg for valve springs that means closest coils against the cyl head). I would therefore expect closer coils to be at the top on front forks.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online bsa-bill

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Re: Fork Springs
« Reply #2 on: 15.10. 2018 18:31 »
Quote
Asymmetrical springs are normally fitted with the closer coils closest to the end with least movemen

Not doubting you RDfella, but my old brain fails to see how it would make any difference, although when I fitted them to my forks I did make sure they were both on the same way (just in case)

I got Prof Brian Cox's "Wonders of the Universe and Solar System" for Christmas, haven't got around to starting it yet but when I do and get through maybe I'll get back to you and agree  *conf2*

All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online RDfella

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Re: Fork Springs
« Reply #3 on: 15.10. 2018 21:17 »
bsa-Bill - something about 'unsprung weight' or similar. Certainly engine manufacturers explicitly warn to fit valve springs with closest coils to the head. Why move more metal than necessary? BTW, never did reckon much on Brian Cox. World is full of experts who know what they have been told - by people who remembered what they had been told - but none of them have ever actually done anything. Engineering is knee-deep in these types. When he was at uni my son used to phone me on a daily basis 'Dad, how do you do so and so?' My reply was always 'but I'm paying for you to be taught that'. And his reply was always 'yes, Dad, but they don't know'. Was the same when I attended tec in the early 60's. I had started life in the tool room of an engineering firm and knew quite a bit before I got there, so it came as a shock when I found I knew more than the guy teaching. JHe was OK about it, though. Used to come in in the morning, open the class and then leave whilst I ran it for him.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online Peter in Aus

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Re: Fork Springs
« Reply #4 on: 20.10. 2018 02:06 »
While on the subject of fork springs.
When I built up my A7 (it was a basket case) it came with a pair of fork springs which on first inspection looked ok and was duly fitted.
I have been riding the bike for a number of years now (about 12000Ks) and when applying the front brake the bike pulled to left a bit,
It didn't bother me much but when applying the front brake hard it was a bit disconcerting!
So the other day I decided to pull the front forks apart to see what could be doing it, couldn't see much wrong apart from one of the stanchions had a .022in bend so straighten that, bushes were all good.
So cleaned every thing up to reassemble and it was when I was cleaned the springs I noted that the springs looked a bit different, so measured the wire size one was .203in and the other was .198in they were the same length and number of coils. A very noticeable different's when compressing them by hand.
So I think this was what was making it pull to the left when the front brake was played.
I have ordered a new set of springs.
So the morel of the story is, look at your springs carefully. *red*
Peter

Busselton West Australia
49 A7 longstroke
58 A10  SA

Online berger

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Re: Fork Springs
« Reply #5 on: 20.10. 2018 05:27 »
I resemble that remark - look at your springs because I didn't know mine had side car ones in it until we had a whoopsy  and I had to do lots and lots of *work*and a mate said there side car springs,   and i said oh it must have had a side car then *dunno*