XS400 swingarm fitment

[esmith87]

I am rounding up parts for my 1981 xs400 Café build. I recently located and purchased an 18" rear mag wheel with drum brake off a German XS400, from a gentleman in Germany. From the research I've done the wheel will work fine and is identical to the US models as far as bearings and axle are concerned. What I am wondering, is if the swingarms between the US and Euro models are the same? I didn't buy the swingarm from the gentleman due to price, but now wonder if I should have. Is there anyone one here who has done this wheel swap using the stock US swingarm? Any input is greatly appreciated.

 

[bcware]

The swing-arms did change at some point, yes. I think it was around '81 when this happened. The older models with the 18" real wheel actually have a narrower swing-arm. The later models with the 16" rear wheel have a slightly wider swing-arm. They are not directly interchangeable.

XSChris can tell you more. He knows everything about the different models

 

[esmith87]

I would be more concerned with length between the center of swingarm pivot shaft to center of axle slots. By older models, are you referring to the Euro models or the 77-79 US models with the 18 inch disc brake rear wheel?

 

[bcware]

The '81+ swing-arm is too wide for my '78 frame at the pivot/bushings area. So, the pre '81 swing-arms for 18" wheels should be too small for an '81 frame without using some kind of spacer.

 

[esmith87]

oops!!! sorry but I just now realized that I didn't make it known in my first post that I have an original 1981 US model swingarm. Just wondering if it is the same as the 81 Euro models. bcware, your explanation does make perfect sense though, if I am forced to use an older swingarm, then I'll keep that in mind. thanks for your input.

 

[bcware]

I don't think there are any differences in the euro models other than options for brakes and wheels combinations.

A swing-arm made for a disc brake has a different bracket for the caliper whereas one made for a drum will have a place for the bracing arm.

As far as I know and to be totally explicit:

18" wire wheel drum brake -> 18" mag wheel drum brake = same swing-arm

18" wire wheel disc brake -> 18" mag wheel disc brake = same swing-arm

18" wire wheel drum brake -> 18" mag wheel disc brake = same size swing-arm, but different mounting bracket for brakes

18" wire wheel disc brake -> 18" mag wheel drum brake = same size swing-arm, but different mounting bracket for brakes

16" wheel any brake -> 18" wheel any brake = swing-arm does NOT bolt up without modification

18" wheel any brake -> 16" wheel any brake = swing-arm does NOT bolt up without modification

 

[esmith87]

ok I see now what you were getting at earlier. I'm just in for some mods I suppose. Thanks for your help.

 

[bcware]

So you have a 16" wheel right now and you want to convert to an 18" wheel?

 

[esmith87]

Yes, exactly but I don't want to change brake style, so I figure the Euro drum alloy mag is my best option.

 

[bcware]

Ok, I think the bearings are the same size, so the axle would also be the same diameter.

The 16" wheel swing-arm is wider (at least internally allowing for a larger tire and also wider at the pivoting point) than the 18" wheel swing-arm. This is good, because your new 18" wheel will definitely not have an issue with clearance.

What I don't know, is if the wheels are the same width at the hub (distance from outside of left bearing to distance on outside of right bearing). If they are not you may only need to make some spacers. If they are you may not have to change anything.

 

[esmith87]

Well don't tell me too much possible good news , because if it doesn't work then I might cry! Not really, but I have had this idea for a while as part of my build, and it would ruin my plans for the build if it doesn't work.

 

[bcware]

There is a good chance it will work. Take in to consideration that the engine is constant. This means that the offset of the rear sprocket on both wheels must ultimately be the same because the chain needs to be straight.

I actually have an '81 swing-arm in my garage. Let me go check.

 

[esmith87]

I have one in my garage too, but my garage is at my younger bros house about 20 minutes from here

 

[Scorpio1963]

Good info in this thread cause I also thought about converting to an 18 inch rear tire.I wanted to raise up the rear stance of my bike but I can probably do this easier by swapping to longer spring and shock.

 

[bcware]

So, I'm back. And...







I have good news.

It looks as though the swing-arms are the same width at the axle. Granted I simply held it up to my swing-arm and didn't measure, but they look the same.

It appears as though they are only different in terms of internal clearance and at the pivot point.

Going from an 18" to a 16" wheel wouldn't work because the 16" tire is wider and would rub. Going from 16" to 18" looks like it will work.

Be sure to follow up when the parts come in. I'd like to know if this is correct!

 

[esmith87]

I'm raising the stance too, I'm 6'4" tall so bigger rear wheel plus tall shocks and tensioner to keep chain off swingarm are all in order.

 

[bcware]

I'm 6'1" but have a long inseam (like 35") and the way mine sits currently is very comfortable for me and I have a very low custom seat on it. My tires are slightly over sized and I have 14.5" shocks.

 

[esmith87]

BCWare: Will do! Thanks for investigating for me, as I'm currently snowed in at the moment. You've been a big help. Yeah, I'm a 36 inseam, so I'll look like a polar bear on a unicycle, no matter what I do.

 

[bcware]

No problem! We're having a heat wave here; it's like 30 degrees out!

 

[xschris]

Going drum to drum should work. The drum mag swing arm should be the same as the 78-79 drum spoke swing arm's. The 80-82 16" rear wheel swing arm's are wider at the front and 1" longer the the "standard" one's. BC has it right. It all should work but far as I can remember no one on here has done it before and you will be the first.