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PostPosted: Wed Oct 31, 2018 1:55 am 
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Hello to all

Over the years, I've come across three pairs of Mani 1 forks, none of which have worked and all have had completely dead internals. I've decided that the time has come to stop procrastinating and actually restore them back to working order. This has already proved to be more of a headache than I anticipated, but mainly in respect of sourcing some compatible elastomers. For the record - I know about the guys in the US that sell replacement elastomers for $55 - for me, this is too much for some slices of polyurethane rubber rod!

I actually sourced a digital copy of the Mani 1 owners manual and uploaded it on here some years ago now:

viewtopic.php?f=9&t=257529

I've been pouring over it, to try and work out what I need to source so that I can put the thing back together in some semblance of working order, as when I disassembled the forks, they don't particularly match the assembly instructions that I uploaded. Below is a picture of the inner legs, with the remains of the elastomer stack on my workbench. You can see that there were two smaller yellow elastomers, and one bigger red elastomer. The yellow elastomers that I have are 17mm in length (17mm x 20mm). The red's are harder to measure as they are a little deformed. Whilst they actually measure 44mm - I'm assuming that they were a little longer than this originally, and were probably also the same OD originally (20mm) so that they've been a bit squashed which has made them a bit shorter and a bit wider than they should be? Does anyone know how long they should be?

For me, this raises some questions:

1 - Is this all correct? The yellow elastomers are clearly much softer than the red one. The red one has almost no give at all and is more like a plastic than an elastomer in terms of compression spring. Am I right in understanding, that this stack of 2x yellow and 1x red elastomers functions are all to give all of the fork compression, and then the rebound spring of the fork? ... or does the red elastomer do something else or is there, for another purpose?

2 - Given that the red elastomer is more like a plastic, is this because it's just really, really old and has hardened up over the years and simply doesn't behave as it would have done when it was new anymore? If not, and it should be extremely hard by comparison to the yellow elastomers - why is this?

3 - Assuming that these are correct and/or yes, I'm trying to source some 20mm polyurethane rubber rod; 20mm OD and with a 6mm ID bore. Does anyone know the rated hardnesses of what I need to source to replace the stack reasonably accurately? I've already visited a local plastics manufacturer, and whilst this probably isn't going to be a cost effective solution, he seemed to think that the yellows were around 40-50 (just by feel in his fingers), and that the red was around the 90 mark. Does this sound about right?

4 - What's the purpose of the rebound elastomer that sits inside the inner leg just underneath the long bolt, and does anyone know what hardness and what size this elastomer needs to be?

5 - Of most concern to me, is to understand why my stack doesn't really resemble the original Manitou instructions? In the Manitou schematic, it clearly shows just two washers, and two elastomers in the stack - one small and one large. I'd be enormously grateful if someone had a little more tech spec on this. I don't mind at all if what I put back into the fork is different, as long as it works as it should as a result.

5 - Once I've sourced the rod, or elastomers that I'm going to use, is it ok to simply use Pace RC7 grease to lubricate everything, and not fall into the trap of using the wrong (lithium) grease that degrades the elastomers into mush?

Once I've got this all sorted, I'm quite happy to share the rebuild pictures and details of where to obtain the replacement elastomers to actually make the refurb work.... without having to pay $70-80 to have them shipped from the US (with shipping).


Attachments:
File comment: This is how the stack looked when I removed the outer legs. The other leg was worse, with most it remaining in the outer leg!
IMG_20181010_2116152-1.jpg
IMG_20181010_2116152-1.jpg [ 150.66 KiB | Viewed 305 times ]
File comment: What the stack looked like, with the remaining ok'ish elastomers.
IMG_20181021_2108005-1.jpg
IMG_20181021_2108005-1.jpg [ 83.34 KiB | Viewed 305 times ]


Last edited by rjsdavis on Thu Nov 08, 2018 5:37 pm, edited 1 time in total.
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PostPosted: Wed Oct 31, 2018 8:00 am 
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Not sure hope much help this is, but there is a chap in Europe selling elastomer replacements for about £36 with postage. He doesn't list M1 but he might be able to help. Might be worth a try.
viewtopic.php?f=2&t=385967&p=2857450&hilit=elastomers#p2857450.


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PostPosted: Wed Nov 07, 2018 2:24 pm 
retrobike rider / Gold Trader
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rjsdavis wrote:
1 - Is this all correct? The yellow elastomers are clearly much softer than the red one. The red one has almost no give at all and is more like a plastic than an elastomer in terms of compression spring. Am I right in understanding, that this stack of 2x yellow and 1x red elastomers functions are all to give all of the fork compression, and then the rebound spring of the fork? ... or does the red elastomer do something else or is there, for another purpose?

Nope, the yellow elastomer is the harder elastomer, it’s just in your case, the yellow is less degraded….
Blue = soft
Red=Med
Yellow=hard
And IIRC, black is extra soft, or rebound (often goes to treacle).
There was a super-soft green “cold weather kit”, but IIRC this was for the 3/4/EFC with the 4mm hole.

Manitou 1, factory, had one small elastomer, then one really long elastomer. This in part was to be a little less fiddly getting the bolt back into the lowers, which on M1 is particularly fiddly.
Manitou 2 moved onto all small elastomers, with more in the stack, so you could better fine-tune your stack. You can do this on M1 also, but it’s really easy to drop a small elastomer off the end of the bolt.
People were chopping the elastomers from day one to mix-and-match the stack in M1s, but people hacked them really badly as a dry Stanley knife won’t make a clean cut (you need to oil the blade). The hack-lines on the elastomers caused them to split and jam in the lowers. From M2 on, Answer had effectively done this for you.

rjsdavis wrote:
2 - Given that the red elastomer is more like a plastic, is this because it's just really, really old and has hardened up over the years and simply doesn't behave as it would have done when it was new anymore? If not, and it should be extremely hard by comparison to the yellow elastomers - why is this?

See above. The elastomers seem to go one of two ways, either to mush and really sticky, or to swell and go rock hard. “Wrong” grease doesn’t help, but they’re all on a free-fall to degradation.

rjsdavis wrote:
3 - Assuming that these are correct and/or yes, I'm trying to source some 20mm polyurethane rubber rod; 20mm OD and with a 6mm ID bore. Does anyone know the rated hardnesses of what I need to source to replace the stack reasonably accurately? I've already visited a local plastics manufacturer, and whilst this probably isn't going to be a cost effective solution, he seemed to think that the yellows were around 40-50 (just by feel in his fingers), and that the red was around the 90 mark. Does this sound about right?

I’ll let someone else answer this particular part of the question. If you do a search I think it’s been covered before.

rjsdavis wrote:
4 - What's the purpose of the rebound elastomer that sits inside the inner leg just underneath the long bolt, and does anyone know what hardness and what size this elastomer needs to be?

Same diameter and bore. Short. From memory about 15mm long.
The purpose is to stop the top-out “clunk” that will occur when the fork tops out i.e. rebounds quickly to top-out

rjsdavis wrote:
5 - Of most concern to me, is to understand why my stack doesn't really resemble the original Manitou instructions? In the Manitou schematic, it clearly shows just two washers, and two elastomers in the stack - one small and one large. I'd be enormously grateful if someone had a little more tech spec on this. I don't mind at all if what I put back into the fork is different, as long as it works as it should as a result.

See above, question 1. 2 elastomers was the early M1 configuration, pretty much universally abandoned.

rjsdavis wrote:
5 - Once I've sourced the rod, or elastomers that I'm going to use, is it ok to simply use Pace RC7 grease to lubricate everything, and not fall into the trap of using the wrong (lithium) grease that degrades the elastomers into mush?

Sounds like the best sort of stuff to use! Using heavy oil based car axle grease is not the stuff to use.


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PostPosted: Thu Nov 08, 2018 5:33 pm 
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Joined: Sat Jul 14, 2012 8:23 pm
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elite504 wrote:
rjsdavis wrote:
3 - Assuming that these are correct and/or yes, I'm trying to source some 20mm polyurethane rubber rod; 20mm OD and with a 6mm ID bore. Does anyone know the rated hardnesses of what I need to source to replace the stack reasonably accurately? I've already visited a local plastics manufacturer, and whilst this probably isn't going to be a cost effective solution, he seemed to think that the yellows were around 40-50 (just by feel in his fingers), and that the red was around the 90 mark. Does this sound about right?


I’ll let someone else answer this particular part of the question. If you do a search I think it’s been covered before.


Thank you Elite, this is a really helpful reply, which has helped me enormously. I am really grateful.

I've done a search for elastomer hardness ratings, and I can't find anything anywhere. Do you happen to know anything about what the varying hardnesses are of the different types of elastomer that you outlined in your post?

I think I've now found a plastics firm here in the UK, that are prepared to make and supply custom rod, but I just need to get a better idea of what spec to order from them. I think I'm ready to go after that!

If it all works out, happy to offer up the excesses elastomers on here, as it's proving to be a real pain in the ass, to find any elastomers at all! I know the forks are crap by today's standards, but for an early 90's bike, it's just got to be just so!

PS - with my original picture, with the 2x yellow and 1x red elastomer, as I look at it, am I right in thinking that the stack should largely end at the end of the non-threaded section of the bolt, just where the threads start? I'm assuming that once you've got some nice new elastomers on the stack bolt, that when the inner legs are slid into the outer legs, that you should simply bolt down the stack bolt and the bottom of the elastomer stack should be snug against the bottom of the inner leg? I'm also realising that there would be 15mm or so approx less bolt available for the compression stack, as in this instance the rebound elastomer is effectively mush and in effect missing!


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 Post subject: Re: Re:
PostPosted: Thu Nov 08, 2018 5:39 pm 
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Gerard wrote:
Not sure hope much help this is, but there is a chap in Europe selling elastomer replacements for about £36 with postage. He doesn't list M1 but he might be able to help. Might be worth a try.
viewtopic.php?f=2&t=385967&p=2857450&hilit=elastomers#p2857450.


Thanks Gerard - I'll take a look...


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PostPosted: Thu Nov 15, 2018 7:46 pm 
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Not sure any of this will help further, but I've just bought a Manitou 1 and ordered a load of spares and new elastomers from SFP. They also have some guides on their website.

http://suspensionforkparts.net/manuals/ ... itou_1.pdf


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PostPosted: Thu Nov 15, 2018 9:46 pm 
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Thanks Regan, but as per the first para of my OP, am well aware of these guys, and $55 for some rubber, plus a further 20 bucks in postage to the UK, is way too much for some small pieces of rubber!

I think I may have found a far better source for elastomers going forward, and will be updating this thread in due course, if it pans out.


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PostPosted: Thu Nov 15, 2018 9:48 pm 
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rjsdavis wrote:
Thanks Regan, but as per the first para of my OP, am well aware of these guys, and $55 for some rubber, plus a further 20 bucks in postage to the UK, is way too much for some small pieces of rubber!

I think I may have found a far better source for elastomers going forward, and will be updating this thread in due course, if it pans out.

Strange though it seems, I read the thread form the bottom up and missed the detail in the OP :facepalm:


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PostPosted: Fri Nov 16, 2018 8:10 am 
retrobike rider / Gold Trader
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rjsdavis wrote:
am I right in thinking that the stack should largely end at the end of the non-threaded section of the bolt, just where the threads start? I'm assuming that once you've got some nice new elastomers on the stack bolt, that when the inner legs are slid into the outer legs, that you should simply bolt down the stack bolt and the bottom of the elastomer


Apologies for the delay in responding, I'm not able to be as active on the forum as I used to be.
Paraphrasing your question (and my answer) a little, to be crystal, the order of parts should be thus:
Bolt, washer, black top-out elastomer (NOW drop the parts into the stanchion), then WASHER, elastomer, washer elastomer etc etc, <repeat>however many you use, depending on size.

THE CRITICAL DETAILS:
-If you have all the washers and elastomers (PUSHED UP) on the bolt, the bolt is longer, and there would be threads visible. These will screw into the slider when the time comes
-BUT, you need to pull the stack down, to allow the stanchion bottom bushing to be put into place around the top of the washer/ elastomer stack.
- the top steel washer above the elastomer stack is CRITICAL. When everything is pushed together, and the bolt pushed down with the long allen key, the top washer ABOVE the elastomer stack will push on the bottom of the split bushing, pushing it into place on the bottom of the stanchion.

Hope this makes sense!

NOTE: Having had a look at the manual scan on SFP.net, there is a label omission. On the diagram it is not clear that the top-washer I describe is there as it has no label. It IS there in the diagram, on the end of the stanchion. It makes the stanchion look like it is 'grooved' at the end, when in fact the stanchion has shoulder (not a groove).
You can see from the diagram that the position of the bushing tries to show that the bushing goes between the washer and the stanchion end, albeit though as I say, not too clearly.


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