NRS frame for new e-bike project

[minde28383]

Yesterday I bought Giant NRS XL 22.5" frame for my new e-bike project. Looks like this is 2004 model, though I found no sticker with years on it. Frame itself has no cracks or bends except some scratches which are seen on pics.
One of bearing is worn out, because some movement is easily noticeable when shaking rear shock (see pic with red note). Some other bearing (probably pivot) is also slightly cracking though can't find yet which one exactly. I was trying to find bearing kit online though no results. Also most probably that original Air shock will need change because it holds no air-pressure and makes noise like it would crack every time when fully compressed. It would be better to rebuild original shock with rebuild seal kit then to change to new one but found no Giant Air shock seal kit on Giant online store.
I'm transferring from HT to FS frame because I expect smoother rides on uneven pavements in the city.

Plan is equip the frame with: 2806 rear hub, 26" wheels 2.2 tires, 72V, 25Amps Infineon, front fork Spinner 300.

 

[GrayKard]

Here's probably why you haven't found a rebuild kit:

Excerpt from NRS 2004 owners manually pdf.

There are no serviceable parts inside these Giant shock units. For maintenance, repair or service, return
only to an authorised Giant dealer (or call the Giant distributor in your country) once a year or more often
if the bike is used in extreme conditions.
This service is not necessarily free of charge!
WARNINGS:
• All service and maintenance of the rear shocks should only be performed with proper tools by
an authorised Giant dealer or by the Giant distributor in your country.
• Do not disassemble or otherwise modify the shock unit or attachments.
Doing so will not only void all warranties but can lead to serious injury or death.
There’s high pressurised gas inside the shock.
Also, don’t place it into the fire.
• Don’t turn the rebound damping adjust knob with pliers or another tool.
Only use your fingers to turn the knob to adjust the rebound damping.

http://www.giant-bicycles.com/_upload_it/bikes/models/manual/NRS Owners Manual.pdf

 

[dogman dan]

Place called chain reaction cycles is a good source for older, shorter size shocks. Only place I could find a shorty that fit my specialized. Good prices, and suprisingly fast shipping from Europe.

http://www.chainreactioncycles.com/Categories.aspx?CategoryID=175

 

[minde28383]

GrayKard, I like "Do not disassemble or otherwise modify the shock unit or attachments" the most

dogman, I think I'll find 6.5" shock easily, these are still manufactured and available.


Today is disassembled rear fork to find what's shape bearing truly are and found that one of them (pic 4) is truly done... The real change came across when inner peace of bearing (pic 4) came off and outer bearing's ring left inside, currently see no option to remove it, so kinda stuck now till will get some ideas how to remove it.
Actually even another bearing in whole peace (pic 7) is not coming out. I was hammering it with rod quite hard but no movement at all, looks like during so many years it glued together with rear shock

When whole rear fork was in one peace, attached to the frame, it was much less noticeable how much bearing are worn out. After dismantle I want to change all bearings to new ones.

 

[michaelplogue]

Somehow, I'm not too surprised with the failure of those bearings. Just looking at that setup, it does not look to be very well designed. I'm no engineer, but the lines of force versus the various pivot points don't look to be thought out very well, and look like they would put a lot of undue stress on all of the pivot points. The only way I can really explain what I'm seeing is that it looks like the entire rear suspension system would be fighting itself.... :|

 

[michaelplogue]

.

Maybe this will illustrate it better....

When your rear wheel hits a bump and moves upward, the 'seat-stay' (red portion) will want to rotate clockwise. However, it's arc of rotation intersects the arc of rotation of the rocker for the shock (in a bad way). So basically they will end up just pushing against each other putting stress on both of their pivot points - in effect they are sort of locked into position without either of them having any way of pivoting smoothly. This is why I suspect the bearings are pulverized - it's putting a lot of lateral stress on them (and on the lever arm pivot as well).

.....Unless I'm completely missing something here...

.

 

[michaelplogue]

Ahh... Disregard! I finally found a picture of a bare frame for one of these bikes. Didn't realize that the chainstay also pivots at the bottom bracket. Makes sense to me now.....

 

[minde28383]

Hi michaelplogue, you missed it yes, chainstay also pivots; NRS stands for "No Resonance System". This is 4 point system and is revolutionary system by the way . It was found to by so effective that it is used since these days when it was started (~2000 year) till present. 4 point system helps to escape bob when pedaled. The main difference from this NRS 2004 compared to some new FS bike is rear wheel travel distance. This one has ~8cm and present models have ~15cm, so rear wheel travel increased about twice. But even few cm rear wheel's travel makes big difference (in a good way) when run for higher speeds. Currently I run HT and when I rush on bumpy paths, bike's rear wheel goes up on bumps loosing traction and making hard smash on the way down.

 

[michaelplogue]

Yea, looking at it, it's basically how a double a-arm front suspension system works on cars. The 'seat-stay' would equate to the uprights, with the 'chain-stay' and rocker arm acting as the two wishbones. Clever!

 

[minde28383]

now I'm in big hesitation. Encountered these cracked ball bearing outer ring's removal problem plus started counting how much I'll spend for new bearings and am I happy with 75mm rear wheel travel. Newer frames have twice rear wheel travel. I think at the end sum will count up so that I would buy new model frame.

 

[minde28383]

Today I did some search online and found all ball bearings I need except 1910. Actually I found 1910 online in catalogs but it's not on sell by one piece; seller needs to be inquired with bigger quantities like 100 pieces. Possibly you mates know some online shop which would sell ball bearing 1910 (model). Bu the way, what bearings would be better to install Ceramic or Chrome. Ceramic bearings are much expensive compared with Chrome, but are they really needed in bicycle applications?

Swing arm left ballbearing
688RS Size: 8x16x5 mm
Ball Material: Ceramic Silicon Nitride $9.69
Ball Material: Chrome Steel $2.19



Swing arm middle ballbearing
6900RS Size: 10X22X6 mm
Ball Material: Chrome Steel $3.19


Chain-stay right
6000 Size: 10x26x8 mm
Product Seal: One Rubber Seals (RS)
Ball Material: Chrome Steel 3.19
Ball Material: Ceramic Silicon Nitride $16.97



Chain-stay left
1910 Still searching for this one


By the way, ball bearings much cheaper to buy separately then bearing kits which include screws and washers which can be taken from current setup.

Also possibly you have some comments on ball bearings which are installed by bicycle manufactures vs regular Chrome bearings which can be acquired through online bearings shops. Maybe manufacturers put only best bearings, - presumably Ceramic?

In bellow pic you can see joints with bearing number, you can ignore letters next to numbers, basically they can differ from manufacturer to manufacturer.

 

[liveforphysics]

Did you check VBX bearing?

I don't see the purpose of ceramic balls for a suspension pivot. The big advantages of ceramic are higher speed ratings (and slightly less drag, less lube needs, lighter weight etc).

 

[minde28383]

Good to know, that's even better because Chrome bearings are cheaper. So I'll get Chrome balls. VBX bearing helped a lot, thanks liveforphysics.

Does anybody has ideas how how to remove that outer ring which left after I removed cracked inner ring with balls? Outer ring left inside... (more pics above) Somehow it needs to be pulled out, but I can't come up with a tool which is needed for the purpose.

 

[mdd0127]

For your own safety, I would not recommend building an e-bike with one of these frames. My local bike shop had a few that were too dented and were replaced. I was going to rob the bottom bracket and head tube from one. The alloy is very poor quality. It evaporates when welded and has very low density.....or it's porous or something. I don't know exactly how to describe it. After looking over a few of these frames, it's a design issue, not a manufacturing flaw. I've also seen a few for sale with cracked and/or broken chain stays. If you can dent the top tube by squeezing it in your hand, it's probably not a good platform for an e-bike. If you do build it, don't ever let it get dented and inspect for cracks frequently. I don't mean to rain on your parade, I just don't want anyone getting hurt and I wouldn't ride one of those frames as a bicycle, much less an e-bike.

 

[minde28383]

I think you just had bad experience seeing those cracked frames; mine has 6 years of abuse and still good. In mtbr.com mostly good reviews about AluxX 6061. I don't say that its best composition of aluminum, nowadays there is 7xxx but I think I'll give a try to oldie

 

[minde28383]

trying to remove cracked bearing I should it for a few workshops, none managed to take out it, so I decided to tackle it myself .It took 4 hours literally to hammer 1 millimeter cracked bearing's ring. After it moved milliliter I manager to insert spring washer and pressed it out. Now have measurements of bearings; have checked online bearing shop; all needed bearings are online, needs to be ordered, will cost ~ 35 bucks.

Currently shopping for a rear shock 6.5". Currently there frame has original NRS shock which is wear out' probably repair kit for 30 pounds would fix it but I think new SR rear shock for ~150bukcs will do job much better. I hope shocks manufacturers makes far better shocks than 7 years ago, I hope so.

 

[Mark_A_W]

I'd be careful with this frame - I've busted two XC dually frames now, one on the chainstay.

Those webbings to the bearing on the chainstay look very weak, I would find a way to reinforce them.


IMO only a heavy DH frame is suitable for an ebike, XC duallies are too lightly built.

Also, in my experience the XC duallies have to much side to side wobble in them, when you fit a heavy motor to them.


I hate to be constantly negative, I guess if you treat it gently then it will be ok...but then what's the point in a dually if you don't go over bumps?

 

[full-throttle]

Check this viewtopic.php?f=6&t=17330