Author Topic: Front springs the wrong way round? (Read 3110 times)

NPLO · **on:** May 23, 2020, 01:45:12 pm

Hello everybody, this is my first post. I discovered this forum after a search led me to Ducati Scotty’s very helpful tutorial on removing the front forks.

Anyway, forks now removed and caps off. When I tipped the forks into a bucket to drain them I was surprised that the more tightly coiled part of the spring was at the top of the fork not the bottom.

I’ve had the bike, Bullet B5 2011, since new and it’s the first time that the springs have been out since the factory.

I attach a picture. The end on the left came out first and was therefore at the top.

Am I right in thinking that the forks were fitted upside down and if so, how would this effect handling?

Cheers,
Nigel

Richard230 · **Reply #1 on:** May 23, 2020, 01:58:43 pm

I am not sure that it makes any practical difference in the functioning of the forks which way the springs are installed. If it was me, I would install the springs with the more tightly wound section of the spring facing upward like you found them installed them in your forks. It may theoretically make a difference which way is up, but I am pretty sure that the rider will not notice any difference, especially on a Royal Enfield Bullet.

NPLO · **Reply #2 on:** May 23, 2020, 02:16:37 pm

Quote from: Richard230 on May 23, 2020, 01:58:43 pm

I am not sure that it makes any practical difference in the functioning of the forks which way the springs are installed. If it was me, I would install the springs with the more tightly wound section of the spring facing upward like you found them installed them in your forks. It may theoretically make a difference which way is up, but I am pretty sure that the rider will not notice any difference, especially on a Royal Enfield Bullet.

Thanks Richard. What you say makes perfect sense, it’s just that the Haynes manual says “fit the spring with its closer-wound coils at the bottom” and I have read the same elsewhere. However, my default would be to replace the springs as they were when they left the factory, assuming they got it right! So I suppose I would be interested to know if any other B5 owners have the springs fitted this way round.

Haggis · **Reply #3 on:** May 23, 2020, 03:39:54 pm

Not B5 but on all four of my C5 I've had, the springs have all had the tight coils at the bottom.
This is on straight leg forks not the older offset axle forks.

Richard230 · **Reply #4 on:** May 23, 2020, 03:44:06 pm

I changed the fork oil of my 2012 B5 but I can't recall for sure which way I reinstalled the fork springs. However, looking at the attached photo from my oil change it does look as if the tighter section of the spring was facing downward and were likely replaced that way.

NPLO · **Reply #5 on:** May 23, 2020, 03:55:07 pm

Thanks Haggis and Richard.

I suppose my questions now are:-

Does it really matter which way round they go?

And if it does why?

Nigel

Farmer_John · **Reply #6 on:** May 23, 2020, 04:03:28 pm

Pretty sure (unless some engineering type can correct me) that a spring is a spring upside right or down. It compresses, it rebounds.

Rattlebattle · **Reply #7 on:** May 23, 2020, 04:14:57 pm

In theory, yes, it does matter. The fork springs are progressively wound, with tighter-bound coils on one end than the other. The theory is that the springs compress progressively ie the loose-wound coils compress first to take up the weight of the rider and to absorb small bumps, with the tighter-wound coils coming into play on bigger bumps and harder braking, where the weight is transferred to the front. In essence the idea is that instead of having springs that are uniform, usually found on lower cost bikes, the degree of compression is influenced more in proportion to the load applied to the forks. That is why aftermarket springs are offered and fitted, though these days there is doubt that they do much and a far better upgrade is to install cartridge emulators. Every set of progressive-wound fork instructions I’ve read advises fitting them with the close-wound coils at the bottom. In my view you might as well fit them the right way, or you can just go with the opinion of others. FWIW it wouldn’t surprise me if the springs were fitted upside down at the factory when they were hand-built, ie pre EuroIV models ((roughly).

Rattlebattle · **Reply #8 on:** May 23, 2020, 04:17:33 pm

It occurs to me also that a good reason to fit them in the advised way is that it’s much easier to compress the fork springs to get the cap on if the “squashier” part of the spring is at the top.

NPLO · **Reply #9 on:** May 23, 2020, 05:19:46 pm

Before I started this thread I thought along the same lines as Rattlebattle but Farmer_John has got me thinking. Now take the thought by Rattlebattle that the cap would be easier to fit with the “squashier” end at the top. Well if that end was at the bottom, surely as you pressed down on the less “squashier” end, the “squashier” end down the bottom would still give way first? This would be the same for bumps in the road too.

Maybe, immersion in in fork oil plays a part?

Anyway, at the moment, I am beginning to think that it may not really matter, but as perceived wisdom, and the Haynes manual, says that the tight coils should be at the bottom, that is probably what I will do!

Rattlebattle · **Reply #10 on:** May 23, 2020, 05:44:27 pm

Yes, I don’t see why it should matter, but as the makers’ advice seems consistent I’d do it the advised way too.

swamp2 · **Reply #11 on:** May 24, 2020, 10:55:40 pm

The springs really don't care what way you put them in, they'll behave the same in either direction. You could mix and match if you felt like it, and you wouldn't know the difference - although I wouldn't do that. The more compliant part of the winding will compress first and then then tighter section will start to go. It doesn't matter if the squishier part is at the top or bottom, it won't be any different with regard pushing the fork tube caps down. I guess depending on how you're measuring the volume of fork oil to put in (e.g. by volume or by depth from top of fork tube) it might be slightly different as the tighter wound coil at the bottom would displace more oil - so if you were measuring by depth it could make a difference in the amount you put in. But if you're just pouring in x oz of oil, it shouldn't matter.

GlennF · **Reply #12 on:** May 25, 2020, 01:29:08 am

In terms of just the compression - a spring is a spring it should not matter.

The two things that come to mind that may differ would be less unsprung weight with the heavier, more compressed, part at the top (on the basis that the "top" of the spring is unsprung and the "bottom" is not) and potentially some sort of difference in the hydraulic damping effect of the oil, depending what part of the spring is immersed. I very much doubt either would be significant (or even noticeable) unless you are doing 130 mph laps around the Isle of Mann on a Manx.

If for some reason unsprung weight matters for you, put the heavy part of the spring at the top, otherwise just go which ever way the mood strikes you.

hpwaco · **Reply #13 on:** May 25, 2020, 03:35:13 am

For what it's worth my 14GT service manual says " install with long pitch up". That's the way mine were/are. Cheers

NPLO · **Reply #14 on:** May 26, 2020, 09:30:18 am

Thanks for all your comments. I will be replacing the springs with the tighter coils at the bottom with the thought that it probably doesn’t matter which way round they go. The start of this thread was my first foray into this forum which is obviously a really useful and friendly resource.

Rattlebattle · **Reply #15 on:** May 27, 2020, 08:43:00 am

Quote from: GlennF on May 25, 2020, 01:29:08 am

In terms of just the compression - a spring is a spring it should not matter.

The two things that come to mind that may differ would be less unsprung weight with the heavier, more compressed, part at the top (on the basis that the "top" of the spring is unsprung and the "bottom" is not) and potentially some sort of difference in the hydraulic damping effect of the oil, depending what part of the spring is immersed. I very much doubt either would be significant (or even noticeable) unless you are doing 130 mph laps around the Isle of Mann on a Manx.

If for some reason unsprung weight matters for you, put the heavy part of the spring at the top, otherwise just go which ever way the mood strikes you.

Wouldn't the up sprung weight be the same? The entire spring is in the fork leg- the sprung part of the bike. Anyway the spring weighs the same whichever way it's mounted.

Haggis · **Reply #16 on:** May 27, 2020, 10:38:52 am

Ye but, theres only one end of the spring moving. ?

Rattlebattle · **Reply #17 on:** May 27, 2020, 02:22:38 pm

Sorry about my last post; it is of course garbage. I don’t know what was in my head at the time. I blame the lockdown and too much heat......

Narada · **Reply #18 on:** May 29, 2020, 08:11:43 pm

FWIW, Stuart Fillingham (of you tube) put YSS springs in his Interceptor and clearly pointed out that even though the springs look symmetrical, there is one end (with numbers etched in) that goes on top, other end is bottom.

ringoism · **Reply #19 on:** May 31, 2020, 08:38:59 am

Quote from: NPLO on May 23, 2020, 02:16:37 pm

the Haynes manual says “fit the spring with its closer-wound coils at the bottom"

If you think about it, this WOULD kinda help reduce "unsprung weight", since if upside down (close coils at top) on small bumps the greater part of the spring would be in constant up/down motion. The correct way, only those tighter coils will be moving most of the time, and the rest is stationary.

I had mine (on the UCE) open a couple weeks ago for the first time.

-Eric

Derek · **Reply #20 on:** June 04, 2020, 10:27:24 am

Found this on the Hitchcock's website under the dual rated fork springs the sell for some of the other non UCE models:

Q:
When fitting the dual rated spring should the section with the tighter coils be at the top or bottom of the fitted spring?
A:
There's no agreement among experts on the best way to fit these springs - only that it doesn't affect the way the springs work or their rating. But both springs should be fitted the same way round. It's suggested that with the closer coils to the top the unsprung weight of the bike is lower.

Ove · **Reply #21 on:** June 04, 2020, 11:56:39 am

Quote from: ringoism on May 31, 2020, 08:38:59 am

If you think about it, this WOULD kinda help reduce "unsprung weight", since if upside down (close coils at top) on small bumps the greater part of the spring would be in constant up/down motion. The correct way, only those tighter coils will be moving most of the time, and the rest is stationary.

I had mine (on the UCE) open a couple weeks ago for the first time.

-Eric

Dont think so. The loosely wound part of the spring would always move first, whether at the top or bottom, wouldn't it? The tightly wound section will weigh more per inch of height than the other section. There's more metal per inch. If the tightly wound section is at the bottom, that is moving up and down as the lightly wound section compresses and rebounds first. So more weight is moving up and down with the tighter coils at the bottom. Whether it makes any difference in the real world, I'd doubt TBH. If it's a serious concern, get some ohlins, or a different bike!