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Discussion Starter · #1 ·
I was having the stock spring in my fork switched out, as well as having new upper seals, and all fluids changed out, which was all long overdue, when bicycle issues all popped up one after another, resulting in the image below:



Here is the current tally on what has gone wrong:
The fork rebuild went fine, until it was put back together and for whatever reason the Motion controll Dampener unit leaked out of the top of the fork. Parts are on order from SRAM through my local shop, which is who is doing the fork rebuild.

While the bike was down, i figured i would go ahead and take apart the linkage, clean up all the winter crap, re-grease and loc-tite the pivot bolts, etc.
When i pulled the BB linkage apart, the bearings were once again, demolished, not quite as bad as the first time, but two of them ended up leaving their outer race firmly pressed into the frame. So, lots of patient use of a hammer and punch and i was able to remove both outer races, one in the rocker arm, one in the swingarm.
So, Now we add 4 enduromax 688 bearings to the list.
additionally, my pivot mounting bolts are bent, and have play in them. so i have the reducers/spacers for the shock on order with Xfusion (or will tomorrow anyway), and the bolts, hopefully, will be ordered through performance bike from mongoose tomorrow.
The larger bearings feel no worse than at the beginning of last summer, so i am leaving them alone until they have more than just some slight indexing.

This is rediculous. i cannot even imagine how bad the design of the BB link pivot was before they made the improvements which was to move the bearings into the frame...

The BB link design is flawed:


this link transmits ALL the impacts and forces the rear swingarm encounters into the rocker arm, which compresses the rear shock, the BB link pivot uses bearings known as "microbearings". 4 of them. they should have used standard skate bearings, 608 bearings, instead of the microbearing 688., oh well. i like the bike, but what a design flaw. tear down and rebuild twice a year.
 

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I feel for you. My 2006 Teocali Super had a sleeve type bearing in the link that would rust and freeze up. Plastic spacers were the only seal, which would wear down quickly when riding in the wet.
 

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Discussion Starter · #3 ·
I was really tired when i posted that rambling above. also very annoyed.

At this point i realize i have to go fabricate new spacers for the BB link, to take out all the slop, and allow for the proper torque values to be applied to the bolts for the BB link pivots. This seems to be an issue for other riders. because this process should be very easy once i obtain the materials, and because i plan to only do this once (and make extras for the future), is anybody else interested in giving me precise measurements to make them some spacers for their freedrive bike's BB link??
let me know, we will discuss.
 

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I made custom spacers for mine and it solved the problem(so far). I have been running standard 688 bearings for a few months now with no issues.

I was going to make extras and post it on here and just mail them to people, but I noticed that the spacers I made for mine would not work on my friends teocali. They amount of play seems to differ from bike to bike. That doesnt say much for mongoose quality control, but explains why some people have more issues then others.
 

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Discussion Starter · #5 ·
Mullen, what material did you use for the spacers? they seem to be some type of anodized Aluminum. I would use Stainless steel, but as it is, the aluminum spacers seem to have caused some wear on the link itself (overtightened bolts), and I'm just not sure that putting a metal with a much higher hardness factor in place of the stock spacers might not be too wise, but most aluminum stock is very soft... what to do?
I plan to simply get a piece of bar stock of whatever material seems to be most appropriate, and use a lathe to bring it down to the proper OD, and then get an 8mm drill bit and use that to bore the proper sized hole, then use a simple cutoff tool to cut the spacers to size, deburring by hand.

I figured that other people would have differing amounts of slop in their frames, so if people have a particular measurement, and get it to me ASAP, i would be happy to snip off a few extras, if you've any need yourself mullen, just get me some sizes.

:thumbsup:
hope this works out! mullen, also what method did you use to measure for sizes? did you use a micrometer to measure the gap left when all hardware was in place, and then divide by two and add to the measurement of the spacers provided? that is my plan, but i have yet to implement it.

thanks man, glad I'm not venturing into completely unknown territory.

I love how this bike rides... I'll never buy another mongoose again.
 

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I used aluminum stock and had my dad who is a machinist get it down to the correct OD and drill it out for me.

To measure size, I used the old ones as a guide and just added a little bit to each. The ones on my swing arm had no play, it was just the ones on the BB that had a little play and needed to fixed. Hopefully it solves the problem completely.
 

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Discussion Starter · #9 ·
thats great info badmechanic but I'm not sure that they are the proper OD. I'll measure the OD of the spacers today, and post up what they are. But IIRC, when looking around for these types of shims, material type, and OD size were the troublesome aspects.

Were you the guy who posted a writeup on fixing the tight swingarm pivot on Schwinn sweetspot bikes?
 

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The OD on a shim is much easier to change than the ID. If it's thin enough, you can usually do it with a pair of good shears. McMaster has the shims I mentioned in stainless steel, which I think is the deal material for this application.

Yes.
 

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Discussion Starter · #11 ·
I disagree bad mechanic.

I would rather have a truly round spacer, 1 piece instead of a shim stack, made of the material the manufacturer used, which seems to be aluminum. the link that the spacer sits directly on is made from aluminum as well. Stainless is much harder, and might cause issues.

Mainly its a matter of the fact that if i cannot buy something that is one piece that will do exactly what I need, but I CAN make it, I'm going to make it. I purchsed the 6061 aluminum rod for under 9 dollars. I will have use of a lathe for the cost of a 6er of good beer, so another ten bucks. I'm not saying using shims isnt a good option, taking up the slack by stacking the shims on the bearing side would be ok, but you have the OD size issue, the inside would work without the need for the OD correction, but then you have a shim stack which might allow unwated noise to develop, AND you have stainless steel riding on aluminum.... maybe thats not as big a deal as i think, But it seems like a bad idea to me.
A once piece, aluminum spacer made to exact specs seems like the ideal choice however.
 

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Iridethedirt said:
I disagree bad mechanic.

I would rather have a truly round spacer, 1 piece instead of a shim stack, made of the material the manufacturer used, which seems to be aluminum. the link that the spacer sits directly on is made from aluminum as well. Stainless is much harder, and might cause issues.

Mainly its a matter of the fact that if i cannot buy something that is one piece that will do exactly what I need, but I CAN make it, I'm going to make it. I purchsed the 6061 aluminum rod for under 9 dollars. I will have use of a lathe for the cost of a 6er of good beer, so another ten bucks. I'm not saying using shims isnt a good option, taking up the slack by stacking the shims on the bearing side would be ok, but you have the OD size issue, the inside would work without the need for the OD correction, but then you have a shim stack which might allow unwated noise to develop, AND you have stainless steel riding on aluminum.... maybe thats not as big a deal as i think, But it seems like a bad idea to me.
A once piece, aluminum spacer made to exact specs seems like the ideal choice however.
The OD doesn't need to be perfectly round (or even close to it) in this application. It's simply not required. Also, the fact it's stainless also doesn't make any difference in this application, since the shims aren't moving relative to the aluminum axle. Additionally, since the shims are compressed against each other, and, again, aren't moving relative to the axle or each other, you're not going to have noise.

Yes, machining a single spacer is the ideal solution. However, most members don't have access to a lathe, and therefore being able to buy off the shelf is useful. From a mechanical standpoint, there are no issues using one or more stainless shims in this application.

Iridethedirt said:
note: we're talking about an ID of 8mm, and an OD of less than 1/2 inch. so snipping a SS spacer down with shears sounds like a hell of a difficult thing to do.
If it's required, it's not that hard. Though personally, I'll use a grinding stone on a Dremel when I need to adjust shims.
 

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Discussion Starter · #16 ·
bad mechanic said:
And what about the people who don't have access to a lathe? :confused:

Anyway, the option is there for people who want it.
Bad Mechanic, i can say that ading additional shims is very difficult, due to the way the linkage has to be assembled.

see the above illustration in the OP in this thread for a visual of the linkage described.

You have 2 female threaded bolts, and a piece of allthread rod with locktite on it, and grease on the shaft of the female bolt, you have to thread the bolts through the bearing, through the stock spacer, through the one, two, maybe 3 shims, and then the link, oh, and you'd better not get locktite on those spacers coated in grease that are sandwiched between the link, and the frame/bearing recess. Its tough enough passing through the bearing, the once spacer and into the link, meeting up with the bolt on the other side, keeping grease and loctite from making contact at all. Will SS shims work? yes. will they gouge into your aluminum link and/or frame when the bearings fail and you dont know just yet because they havent become bad enough to start making lots of noise... yes, SS is harder than aluminum, the softer metal will lose. facing the shims to the BB link would be ideal since its probably far cheaper than a rocker arm, or rear triangle, IF mongoose would even sell those parts to you, and thats doubtful anyway.

For those who do not have access to a lathe, yes, this is certainly a better option than nothing, and cheaper than paying for having something like this machined. however, i am going to make extras, as i have said, and i encourage any freedrive owner to contact me if they need these spacers, maybe i will have the size they need, as i plan on making a variety of thicknesses in the range that i suspect mongoose might have allowed out of the factory at either extreme of the tolerance range.

If i dont have what someone needs, and if they dont have access to a lathe, and its too costly to pay a machine shop to make them a set, then the SS shim option is good to have, as it is most certainly better than doing nothing.

Bad Mechanic, I dont doubt you know your way around dealing with mountain bike suspension linkages, and so on, probably quite well... however, I'm still going to stick with my plan of making a single piece spacer from the same material the manufacturer used, rather than using a stack of shims to get close enough. I also would still reccomend that as the best option IF it is available. However, as you pointed out, its not commonly available to anybody, where as these shims at McMaster are.
Again thanks for the info, freedrive owners need to know that there are options, even if all of them are total PITAs.

Bad Mechanic, I have not heard of these kinds of problems from owners of bikes like Giant, Trek, etc... Also, the GT owners seem very happy with their I-drive bikes and they ride very similarly to the freedrive bikes. What is your experience with other brands regarding tolerances and longevity of pivots and linkage? The mongoose's only issue i see is with this BB link, the other pivots are built just fine, and i have had no issues with them, though i am replacing all the pivot bearings on the bike durring this rebuild as the aparently stock main pivot and rocker arm pivot bearings are worn and becoming indexed now as well. I have more Enduromax bearings on order.

Regarding enduromax bearings: mullen you said you had trouble tracking them down before, and i recall you found some other ABI bearings with decent specs to use instead, and they are holding up for you along with the new spacers, however, here is your source, since i would still replace those bearings probably twice a year anyway, before they fall apart and require you to fiddle with getting the stuck outer race out of the frame.
www.enduroforkseals.com
I also just had my fork fitted with their fork seals as well, I'll let you know how i like them, but i have only heard good things.
 

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ARGH!!!! Seriously?!? :madmax: I'm not saying your method isn't good. In fact, it is the best one available for multiple reasons. I'm not saying you should use the McMaster shims. All I am saying, all I have been saying, is it's a readily available alternative for people unable get a spacer machined for their bike. Does that make it clear enough for you?

Also, the shims will not eat into the aluminum. I'm sorry, but they just won't. The forces in your suspension simply don't work that way.
 

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Discussion Starter · #18 ·
Bad mechanic... if the bearings dont fail catastrophically then yes, you're right, there is no way for there to be enough play to allow the forces to dig into the link.
But when the balls inside a ball bearing are crushed, then, suddenly there is enough play to allow for the movement that will damage parts. Unfortunatly, with these bikes, the undersized bearings used in such a high stress pivot, this type of failure CAN happen without much notice, and before you know it the damage is done.

still don't believe me? here's a picture, sorry its low res, but the silver areas are not supposed to be silver, this occured from the stock aluminum spacer. you can see that it is not uniformly the same width all the way around, the play that allowed this, was the failed bearings.



Uploaded with ImageShack.us

Bad mechanic, as you can see, the wear on the parts you say cannot happen, does, and in fact, DID happen to me. I ride this bike, I work on this bike, I know this bike. I also know what you were saying, but you ignore that I am making extras, or even custom sizes available to folks if they got me the info quickly enough. again, I think this is the third time THANK YOU FOR THE HELPFUL INFO! it is a decent enough semi-solution to the problem.
 

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The problem with the shims you listed badmechanic is the OD is to big and would need to be cut down. most people wouldnt be able to cut them down to the proper OD which is 10mm if i remember correctly. The easiest thing to do would be to find some 10mm OD with any size less then 8mm ID and drill it out to 8mm. Then just cut it to the right thickness. Im sure somewhere there is 10mm OD, 8mm ID stock that you buy and only have to cut to length.
 

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Discussion Starter · #20 ·
mullen119 said:
The problem with the shims you listed badmechanic is the OD is to big and would need to be cut down. most people wouldnt be able to cut them down to the proper OD which is 10mm if i remember correctly. The easiest thing to do would be to find some 10mm OD with any size less then 8mm ID and drill it out to 8mm. Then just cut it to the right thickness. Im sure somewhere there is 10mm OD, 8mm ID stock that you buy and only have to cut to length.
I believe his intention is to run the shims in addition to the stock spacers, putting the shims against the BB link itself. this way you dont need to clear the opening in the rear triangle and rocker arm where the spacers contact the bearings. and this WOULD work. I just worry it might allow the SS shims to dig into the link more than what happened to mine with the stock alum. spacers.
 
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