Author Topic: Bike stuff: My fork blew a seal.  (Read 2230 times)

Le Poisson

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Bike stuff: My fork blew a seal.
« on: July 24, 2017, 07:54:59 PM »
The issue: While out on a ride last week, I attempted to re-pressurize my fork. When I put a frame pump on it to pump up, a froth of oil sprayed out the bottom of the fork. I believe that the seals in the fork are blown. When I got back on the bike, the fork bottomed out on every bump and riding was distinctly not fun. What shall I do about this?

The Bike: 12 yr old Devinci Desperado with Rock Shock SID air/oil Fork. The fork has been mushy for a while, but rideable. Other components are good, but I am not in love with the handlebars and teh bottom bracket has an annoying "Click" to it. Bike mechanics haven't been able to figure out the click.

Use: Commuter bike, gearing up for first attempt at cycletouring.

The Choice - Do I:
1. Have the fork rebuilt - I don't know the price, but will parts even be available on a fork this old? I believe the tech is long past prime.
2. Replace the fork: Looking online, I have seen forks as cheap as $400 and as expensive as $2,000. I think a decent replacement is likely in the $800 range.
3. Replace the bike. I can get a good used bike for close to the price of a new fork, and without the hassle of having to take everything apart and put it back together. I like my bike, but I am not in love with it.

What say ye, oh internet people?

Ocelot

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Re: Bike stuff: My fork blew a seal.
« Reply #1 on: July 24, 2017, 08:38:10 PM »
OK, there are a few things going on here:

1. A regular tire pump won't work to fill the air chamber in your fork. This is because the chamber is tiny and much higher pressure than a tire and thus you need a proper suspension pump. This is almost certainly why you lost all the air pressure and the fork now can't support your weight.

2. When you say "a froth of oil sprayed out the bottom of the fork", exactly which part did it spray out? Is your fork Solo Air (one + air valve at the top of the lefthand leg) or Dual Air ( a + valve at the top and a - valve at the bottom of the leg near the wheel axle)? Which valve were you trying to inflate? Or did you have the bike upsidedown, and oil sprayed out of the main seals where the fork slides into itself?

3. After 12 years and presumably little or no maintenance, your fork likely needs a lot more work than just seals replaced, and if you ride a lot may be beyond economic repair. To put this in context, RockShox recommends main seal replacement every 40 hours riding and a full rebuild every 100 hours - this is, as you'd expect, pretty conservative but you really do need to rebuild every 1-2 years in order to keep your fork from eating itself.
Also bear in mind that the SID is RockShox's highest end, lightest weight racing fork. It's not designed to be mega durable, it's designed to be as light and fast as possible for the type of rider who replaces their equipment every season or two. Frankly, to get 12 years out of one is a pretty sweet run!

If you're mainly commuting, and the touring you aspire to do is mainly on roads, then even a budget $200-300 fork is actually going to be better suited to your riding than the one you have, albeit a little heavier. You could also consider a rigid fork which would be under $200 and have zero maintenance costs. If the rest of your bike is in mechanically good shape then there's not much reason to change it - it's a good bike, and the handlebar and BB issues sound pretty minor.

VCaddy

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Re: Bike stuff: My fork blew a seal.
« Reply #2 on: July 24, 2017, 08:51:20 PM »
You could find a RockShox Recon Silver for around $250.  Might be even less since you need the 26" version with the 1 1/8 steerer tube. 

SRAM still has technical data for your SID, and I was able to find soft parts to rebuild it.  Might be tough to find hard parts for a fork that old. 

Le Poisson

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Re: Bike stuff: My fork blew a seal.
« Reply #3 on: July 24, 2017, 08:53:16 PM »
@Ocelot:

1. Thanks, I didn't know that.

2. It came out the bottom. I didn't realize it was pressurized from the top - in fact I only realized that this am.

3. Sounds like getting an estimate from a good bike shop would be a reasonable option? Let them make the call? Or just go straight to replacement? I did have the fork rebuilt once, about 4 years ago. And the bike has spent much of its existence rusting on a wall. It has only really seen real service in the past 4 years or so.




Le Poisson

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Re: Bike stuff: My fork blew a seal.
« Reply #4 on: July 24, 2017, 09:00:09 PM »
You could find a RockShox Recon Silver for around $250.  Might be even less since you need the 26" version with the 1 1/8 steerer tube. 

SRAM still has technical data for your SID, and I was able to find soft parts to rebuild it.  Might be tough to find hard parts for a fork that old.

So you think something like these would work OK?

http://www.chainreactioncycles.com/ca/en/manitou-marvel-comp-forks-9mmqr-crc-exclusive-2017/rp-prod158510

Ocelot

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Re: Bike stuff: My fork blew a seal.
« Reply #5 on: July 24, 2017, 09:20:15 PM »
If you were trying to pump a valve at the bottom of the fork and that caused foamy oil to gush out that same valve, then that's likely just bath oil which was forced into the valve by gravity then sprayed out by escaping air from you opening it. If this is the case no seals would be damaged, all you need is for the chamber to be inflated. That said, I doubt that is exactly what happened in your case because if you'd only lost air from the bottom valve - the negative chamber - the fork would still support your weight as well as it did before, it would  just feel a bit less plush and top out badly.
It would be very unusual, actually almost impossible, for oil to spray out the bottom of the fork if you were pumping the top chamber even if seals failed.  So I'm still a little confused as to exactly what's happened.

The Recon Silver that Prospector mentioned is a good option, and the Manitou you linked would also work. If you've not comfortable cutting a steerer tube, pressing in the starnut and removing/reinstalling the headset crown race, then if might be in your best interests to get a shop to do the installation for you. It's not too technical but requires some precision and having the right tools minimizes the chance of damaging anything.

Le Poisson

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Re: Bike stuff: My fork blew a seal.
« Reply #6 on: July 24, 2017, 09:49:29 PM »
I just found the cutsheet for my bike: http://www.devinci.com/archive/2006/montagne/EN/desperado.pdf

It was a really good bike when new, but I bought it as old stock from a shop going out of business at a time when buying toys and letting them sit was sortof my lifestyle.


Are you suggesting that the oil may have just been seepage and that if I inflate the top of the fork, it may go back to normal? It has lost a lot of stiffness, and is not recoiling well. What you are describing is close to what I observed.

VCaddy

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Re: Bike stuff: My fork blew a seal.
« Reply #7 on: July 24, 2017, 09:57:53 PM »
That Marvel Comp would work great, I've heard those are a nice fork. 

Rebuild kits are definitely available for the 2006 SID, Universal Cycles has them.  RockShox recommends service every 100 hours, might be worth seeing what your LBS would charge for a rebuild.  If the stanchions and internal shafts aren't scored, I'd think it could be rebuilt. 

bortman

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Re: Bike stuff: My fork blew a seal.
« Reply #8 on: July 25, 2017, 07:19:44 AM »
Another option from a confirmed retrogrouch, consider replacing with a suspension-corrected rigid fork, like the Kona Project 2.

http://www.bikeman.com/KON-P2MTN410.html

I've had front suspension on several of my bikes -- among them, the SID -- and had enough issues (stiction, blown seals, maintenance) that I went back to rigid steel/titanium forks on all my bikes. With a rigid fork you'll save you some weight, have zero maintenance, the fork goes exactly where you point it and does exactly what you tell it to do.

I generally run slightly larger tires to soak up some of the bigger hits, but I'm not a speed daemon.

rothwem

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Re: Bike stuff: My fork blew a seal.
« Reply #9 on: July 25, 2017, 07:46:04 AM »
Another option from a confirmed retrogrouch, consider replacing with a suspension-corrected rigid fork, like the Kona Project 2.

http://www.bikeman.com/KON-P2MTN410.html

I've had front suspension on several of my bikes -- among them, the SID -- and had enough issues (stiction, blown seals, maintenance) that I went back to rigid steel/titanium forks on all my bikes. With a rigid fork you'll save you some weight, have zero maintenance, the fork goes exactly where you point it and does exactly what you tell it to do.

I generally run slightly larger tires to soak up some of the bigger hits, but I'm not a speed daemon.

This.  If you're not riding on singletrack, a suspension fork is totally worthless.  It just bobs around and wastes energy.  I've done literally thousands of road rides over 3 hours on a road bike with 23mm tires and a rigid carbon fiber fork and I've never wished to have suspension on the road. 

Get a rigid fork, but make sure its "suspension corrected" so your geometry isn't screwed up by having a fork that's too short. 

LittleWanderer

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Re: Bike stuff: My fork blew a seal.
« Reply #10 on: July 25, 2017, 11:50:07 AM »
Another option from a confirmed retrogrouch, consider replacing with a suspension-corrected rigid fork, like the Kona Project 2.

http://www.bikeman.com/KON-P2MTN410.html

I've had front suspension on several of my bikes -- among them, the SID -- and had enough issues (stiction, blown seals, maintenance) that I went back to rigid steel/titanium forks on all my bikes. With a rigid fork you'll save you some weight, have zero maintenance, the fork goes exactly where you point it and does exactly what you tell it to do.

I generally run slightly larger tires to soak up some of the bigger hits, but I'm not a speed daemon.

This.  If you're not riding on singletrack, a suspension fork is totally worthless.  It just bobs around and wastes energy.  I've done literally thousands of road rides over 3 hours on a road bike with 23mm tires and a rigid carbon fiber fork and I've never wished to have suspension on the road. 

Get a rigid fork, but make sure its "suspension corrected" so your geometry isn't screwed up by having a fork that's too short.

I was hoping someone would say this.  Why do you need a suspension fork?  If you're using this bike for commuting and possibly touring in the future, rigid is the way to go.  Do you ever ride off road? 

Le Poisson

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Re: Bike stuff: My fork blew a seal.
« Reply #11 on: July 25, 2017, 12:07:43 PM »
I took the bike to the shop at lunch. They are going to do a tune and take a look at the fork/bottom bracket. They didn't sound like they wanted to sell me a fork, so I guess that is good.

The Rigid fork ideas make sense to me. If I get this back and it still feels like mush, I'll likely make a swap.

Reynolds531

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Re: Bike stuff: My fork blew a seal.
« Reply #12 on: July 25, 2017, 01:14:34 PM »
It warms my tiny black little heart that there are other retrogrouches on here. ALL HAIL GRANT PETERSON!

Le Poisson

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Re: Bike stuff: My fork blew a seal.
« Reply #13 on: July 25, 2017, 01:49:54 PM »
Another option from a confirmed retrogrouch, consider replacing with a suspension-corrected rigid fork, like the Kona Project 2.

http://www.bikeman.com/KON-P2MTN410.html

I've had front suspension on several of my bikes -- among them, the SID -- and had enough issues (stiction, blown seals, maintenance) that I went back to rigid steel/titanium forks on all my bikes. With a rigid fork you'll save you some weight, have zero maintenance, the fork goes exactly where you point it and does exactly what you tell it to do.

I generally run slightly larger tires to soak up some of the bigger hits, but I'm not a speed daemon.

This.  If you're not riding on singletrack, a suspension fork is totally worthless.  It just bobs around and wastes energy.  I've done literally thousands of road rides over 3 hours on a road bike with 23mm tires and a rigid carbon fiber fork and I've never wished to have suspension on the road. 

Get a rigid fork, but make sure its "suspension corrected" so your geometry isn't screwed up by having a fork that's too short.

I was hoping someone would say this.  Why do you need a suspension fork?  If you're using this bike for commuting and possibly touring in the future, rigid is the way to go.  Do you ever ride off road?

When I was 20, I rode off-road a lot. back then, any suspension on a bike was a novelty and cutting edge, and weird.

My first suspension bike was a Trek 7000 and I loved it dearly. It was a crazy expense to me at the time. I rode it competitively back in the '90s and had hella fun. It was stolen from my back yard, and I went out and bought a Stumpjumper M2FS which I proceeded to trick out with as much purple ano as I could afford while working in a factory and trying to buy a house. It was also stolen - this time from the locked garage. Someone was watching the house. After that I took a break from bikes, and took up whitewater canoeing for about 10 years.

So when I was wandering in a closeout sale for an indie bike shop and saw this bike for something like 70% off, I snagged it since it was everything I would have wanted in a race bike back when I was racing - and then I abused/ignored it for about 5 years until fate had the bike shop's owner buy the house next door to us. He did me a favour and tuned the bike up once - and made a few comments about how rough a shape it was in... and how much rust has gotten into it. (never leave a bike in a pool shed full of chlorine).

Now I have no interest in racing, but commuting is fun, and touring is worth trying. The frame geometry is comfortable enough that I think this will work for touring. I found panniers that (kindof) fit it. I've spent little, but I think done enough to give a short/easy ride a try. I will go to rigid forks if the touring bug strikes me. They seem like a much better option for attaching racks to, for weight savings, and for control/rigidity on a loaded bike.