Fork stop rings busting up?

[tunnelrider]

I put in new fork damper rod stop rings (like a thick hard piece of synthetic rubber in a ring shape) while replacing the fork seals.  I've just taken a fork apart a year later to work on the slider and there's a fair bit of mashed up debris floating around in there which looks like it's some of the stop ring as it's the same colour.  Surely this can't be normal to wear out if it's not listed as a usual piece of bike maintenance?

The fork tube isn't completely disassembled so I can't see what condition the stop ring is in, but struggle to think of what else in the fork could cause the debris.  The previous ones had disappeared too, just a layer of sludge at the bottom when I first took the forks completely apart.

Just wondering if anyone's come across this before too?

[Barry]

It's not normal for the topping out bump stops to break up so quickly but there was another thread recently (might have been on another forum) where the same thing happened. Possibly a bad batch of spares, were they red ?

Motobins carry a white plastic  version which by all accounts sounds to be much firmer and  tougher. They don't work as well as the red ones in terms of absorbing the shock of topping out but I've had them in for 7 years without any sign of a problems from breaking up.

[tunnelrider]

Oh yeah, thanks Barry for posting your reply.  Yes they were red stop rings that I put in and very good of you to post the picture of the white plastic ones that sound a lot sturdier!  Can't say I notice topping out the forks too often except when I'm tempted to take her over boulders but will look to put in the hardier component.

[Barry]

This was the other recent thread I was thinking about with some pics of chewed up red rubber rings.

http://advrider.com/index.php?threads/79-r65-front-end-all-forked-up.1081586/

[Tony Smith]

The red stop rings get eaten by the additives in a number of fork fluids - I can pretty much guarantee from personal experience that Belray and Motul fluids cause premature death of the stop ring (aside of course from neither of them actually making a fork fluid suitable for our Bavarian Babies.

The "correct" Aeroshell fluid is considered to be a bit "light" by many (including me), in any event Dexron  III trans-fluid is an acceptable replacement for the now obsolete and unavailable specified Aeroshell fluid if you want to try that.

To the extent that it might be useful to you, my 37 years of general experimentation has led me to be firmly of the opinion that Castrol Fork Fluid ios superior to just about anything else and that the correct "weight" for an R65 depending on the weight of the rider and the vigor with which they ride is somewhere between 100% Castrol Fork 5 and 100% Castrol fork 10 (I am currently running 50/50 in the wife's bikle and 100% 10weight in mine.

[tunnelrider]

Good info and link thanks very much Barry and Tony!

I hadn't thought of the fork oil being a degradation problem.  Guess I'll get new plastic stop rings and if I find Castrol fork oil, well, 37 years experience Tony is a time well spent!  I was using Spectro 10 weight fork oil I think but don't have the bottle to check now.

The dude who started the thread on Barry's post seems like a good bloke, unlike his putty like bushes mine were as solid as when I put them in.  And pretty sure I put those parts in the right order!  Cheers. 

[Barry]

Barry, you mentioned you've taken apart your forks many times, did you get sick of changing the stop ring and use the white plastic bush instead?I think I'll try the red bushes one more time.

No, mine had the original  28 year old black bushes which had gone rock hard.  I put the white ones in because that's all Motobins stock.
Taking the forks apart multiple times was experimentation with modified valve washers in an attempt to get rid of the topping out clunk.

[montmil]

Before red, they were black. My 1981 R65.

[nhmaf]

Like Monte's my original black ones had totally disintegrated into fragments.  I replaced them with red ones a couple years back, and have had no problems whatsoever.  Maybe a recent batch of red ones are bad.  I do know that you want to be CAREFUL that you ONLY put in real fork oil, as some of these plastics/synthetic rubbers do not take kindly to various chemicals.

[tunnelrider]

I'll take the damper rod out this weekend and post a picture of the current state of the stop ring.  Thinking I'll order another set of reds and find some decent fork oil. The roads around my town are pretty rough (due to fairly large earthquakes in 2011) and I like taking her on gravel so maybe they'll just bust up again anyway with my riding.  If so I'll have to go for the plastics...

[tunnelrider]

As suspected the stop rings had basically disappeared again.  They'd only done 10 000km / 14 months with Spectro 10 weight fork oil.  Have ordered new red rings and will look for good fork oil. Are there known good fork oils? (I can't find any Castrol fork oil to use that Tony recommended).

[SoloLobo]

That's bad news.  I have about 300 miles on a new set of the red bushes, and am running spectro 5wt.

[montmil]

The 'Bins white nylon rings have enough 'give' to do the job. Unless you just really enjoy regularly taking apart the fork legs... I'd rather be riding than fettling.

Spec fork oil weight is 7.5 wt. A variance between brands is common so do not be mislead by labeling. Can get expensive trying different brands of the same so-called 'weight'. If you can source it, try Dexron III transmission fluid.

[SoloLobo]

Just ordered a set of the Motobins bushes... just under $13 delivered to the USA

[nhmaf]

Yikes, those clearly aren't behaving the way they are supposed to!      Maybe someone at the factory has been making them out of red licorice candy these days.