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Discussion Starter · #1 ·
Hello,

I've been lurking on these forums for a long time now, but this is my first time posting. I've been contemplating a sumo project for a dual sport, and I've sourced a set of ZX6R wheels from the local craigslist. The front wheel bearing size in the ZX6R is 25mm x 47mm x 12mm. The stock fork on mine accepts a 20mm axle, and I can get a pair of 6204s that fit in very nicely. So, here goes my questions:

1) What about the cylindrical thingy in between both the bearings? I've always called it a axle spacer, but I realize now that the word means something else :) I am talking about the tube with a ID slightly more than 25mm. Does that have to be 25mm? From what I understand, the only load in the setup should be on the ball bearings which should allow the wheel to rotate without any friction from the axle. Why is this spacer thing even present? Since my axle is 20mm, do I have to get a matching spacer in 20mm or can I reuse the 25mm ZX6R one?

2) In general, once I get the bearings and the innards swapped, I then need to get spacers on the end near the fork so that the disks are aligned correctly, right? In general, are there any other steps I might have to look for? I've eyeballed the width and while the ZX6R rim is thicker, there is plenty of space to fit it in there.

This is probably a very basic question and asked countless times before. I tried the search before posting, I promise!
 

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Discussion Starter · #3 ·
I've done a few bearing swaps on wheels. The answer to why you need the crush tube can be found HERE.

You should be able to use the 25mm ID tube but it may flop around the smaller axle. Lately, I've been going from 20mm axles to 25mm axles which requires sourcing a bigger tube. I do have a couple 20mm ID tubes that I can get you a length from and model if you want to source a smaller ID tube.

Later, Doug
Thanks Doug! That forum post was very useful - the lateral stress part looks apparent in hindsight, I should have thought about it before. I'll likely go to a 20mm ID tube, I first need to get those bearings off. They've been too darn tight and is my weekend project.
 

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Discussion Starter · #6 ·
Thanks guys. This is exactly the reason why this forum rocks! I've been trying to get the stock bearings off, and man they are hard. I've tried all the tricks except the blowtorch - I'd rather have a shop take them off than do it myself.

While thinking this through again, I am dropping the rake by roughly 2 degrees (26 to 24), which isn't much. But the trail is dropping from 116mm to 85mm, which is like 25%. Is the bike going to be very twichy in real life? Right now, it's just a slow turning pig, so I wouldn't mind some amount of nimbleness. Googling for a road bike with a <90mm trail doesn't show much. I guess I could take it out for a spin after this is done to see how significant it is in real life.
 
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