[admiral01]

Hi all, just another quick question:

For coil forks, when do you replace the springs in them?

Ive got spare springs and my fork is really plush but a little on the softer side. The spares are for the same weight category as the stock springs in fork and am wondering do springs get softer with increased fork usage, and whether changing them in my fork is a good idea or not.

Cheers

 

[127.0.0.1]

the only real answer is change them and you decide which set you like

springs do age with use and get slack, but it depends on how much use and compression over time, and the spring material. bushings, seals, and dampers are the things inside a fork that age quickly and can make it feel like a turd unless they are serviced/cleaned/lubed. the spring is likely the last thing that needs replacing

 

[fredcook]

Interesting question about whether coil springs wear out (get softer) over time. Me personally, I've never experienced a bikes coils going soft. But I'm pretty sure I haven't ridden any one coil shock/fork long enough to get to that point. Speaking from an automotive perspective, there was at time, i.e. vehicles from the 40's, 50's, etc., were it was common for coils to weaken. They got better through the 60's, 70's, etc. Nowadays, I've driven 2000+ model cars, trucks and SUV's over 300,000 miles with no evidence of coil spring sag at all (leaf springs... another story). Newer metallurgy and designs are much better. I suspect the same holds true for bikes. My guess, like 127.0.0.1 said, I'm pretty sure other parts of today's MTB forks and shocks will wear out ling before coils do. But... there may be compromises in a coil structural integrity for bikes, such as giving in to weaker designs that shorten life expectancy, in trade for less weight. But then, to save weight, we can go with air...

 

[dir-T]

Speaking from an automotive perspective, there was at time, i.e. vehicles from the 40's, 50's, etc., were it was common for coils to weaken.

My understanding, from reading a lot of stuff posted by a suspension parts supplier on a classic VW site, is that springs can settle (lose height) over time but the spring rate (firmness) will never change. So, as long as the exposed height of your fork stanchions is the same as it was when new, your springs aren't settling and there is no need to replace them.

 

[admiral01]

Interesting question about whether coil springs wear out (get softer) over time. Me personally, I've never experienced a bikes coils going soft. But I'm pretty sure I haven't ridden any one coil shock/fork long enough to get to that point. Speaking from an automotive perspective, there was at time, i.e. vehicles from the 40's, 50's, etc., were it was common for coils to weaken. They got better through the 60's, 70's, etc. Nowadays, I've driven 2000+ model cars, trucks and SUV's over 300,000 miles with no evidence of coil spring sag at all (leaf springs... another story). Newer metallurgy and designs are much better. I suspect the same holds true for bikes. My guess, like 127.0.0.1 said, I'm pretty sure other parts of today's MTB forks and shocks will wear out ling before coils do. But... there may be compromises in a coil structural integrity for bikes, such as giving in to weaker designs that shorten life expectancy, in trade for less weight. But then, to save weight, we can go with air...

wow I certainly weigh less than a car body so my springs should definitely be fine then hehe. Funny thing is, I am 60kg and the spring was set to 52-70kg but It is just really soft. It has 160mm travel and when I stand on the bike and push hard, I could push a little more than half the travel and have dialled the fork so It is only one click from max pre load.. I have had a 100mm air fork and It was definitely not this soft. Do you think this might just be the nature of coil forks ?
jeez I think im a little too paranoid about this new enduro bike i got. My old bike was an xc race hardtail and I thrashed It and was using way beyond its limits and nothing really bad happened apart from annoying creaks ...

 

[admiral01]

My understanding, from reading a lot of stuff posted by a suspension parts supplier on a classic VW site, is that springs can settle (lose height) over time but the spring rate (firmness) will never change. So, as long as the exposed height of your fork stanchions is the same as it was when new, your springs aren't settling and there is no need to replace them.

dunno about losing the exposed stantion travel as I bought the bike used. Its a 160 travel and When I measured the exposed stantions It was around 166-167mm. Interesting though although I say its soft, I have done 1.2 meter drops and only around 145-150mm travel was used.

 

[kapusta]

For all practical purposes, you should never need to replace a steel coil spring.

 

[kapusta]

wow I certainly weigh less than a car body so my springs should definitely be fine then hehe. Funny thing is, I am 60kg and the spring was set to 52-70kg but It is just really soft. It has 160mm travel and when I stand on the bike and push hard, I could push a little more than half the travel and have dialled the fork so It is only one click from max pre load.. I have had a 100mm air fork and It was definitely not this soft. Do you think this might just be the nature of coil forks ?
jeez I think im a little too paranoid about this new enduro bike i got. My old bike was an xc race hardtail and I thrashed It and was using way beyond its limits and nothing really bad happened apart from annoying creaks ...

A few things:

With proper spring/air pressure, a 160mm fork is going to feel softer than a 100mm fork - because it is more soft (lower spring rate). That is the whole point of having more travel.

Being able to push the fork through half its travel is normal in my experience. You can probably do the same with your 100mm fork.

Longer travel forks feel and behave differently than short travel ones, and there is some adaptation needed in how you ride the bike. Give it some time, if you have not already.

If it IS in fact too soft, you most likely simply need a stiffer spring. When you say the spring was set to 52-70 Kg, I assume you mean that the spring you chose was recommended for riders weighing 52-70Kg. That is just a recommendation, nothing is set in stone. It is not uncommon for people to get best results with spring firmer or softer than recommended.

 

[Velocipedist]

In reality if you cyclically stress a spring beyond elastic deformation near its plastic deformation range (unlikely with a steel or Ti spring on a mtb) the spring would undergo strain hardening and become stronger and therefore more brittle, and likely to crack as it has lost ductility. A spring will not get "softer" over time, it will mechanically harden.

MTB forces are highly unlikely to ever stress steel or Ti beyond its elastic regime. So it is a non issue, crashes or different spring rate would be the only reason I would change a MTB spring.