1980 Drum Brake to Disc Conversion Questions

[JSak]

Hello everyone. I hope its warm enough to ride where you are

I have a 1980 XS400G with front drum brakes. I purchased these forks: . They are from a 1978 disc brake model. The forks are beautiful and were relatively cheap, but they obviously don't work with drum brakes. So, I've decided to ditch the drums and put on disc brakes, and (of course) I have some questions before I start purchasing things off ebay. I think I need a brake caliper, front wheel, brake disc, brake line, and a master cylinder with lever.

Question 1: Are all the front brake calipers for the XS400s interchangeable? Will the 650 calipers fit? I've searched the forum and haven't found a straight answer, but I think the new ones from MikesXS will fit.

Question 2: Do the front master cylinders for the XS400s all have the same piston size? Will the 650 front master cylinders fit? I know different piston sizes will make the brakes feel differently, but I'm looking more for 'cheap and usable' over 'race track perfection'.

Question 3: Are there multiple rim sizes for the front tire? I have a new 3.0x18 front tire on the bike now that I would like to keep, are there certain model years I should avoid?

Thank you for whatever information you have that can help me sort this out.

 

[OleDoc]

xs650 calibers should work

 

[Sandrew]

Hello everyone. I hope its warm enough to ride where you are

Yeah, quite. About -15 degrees and snowy as hell. (Talkin' celsius here).

 

[OliverB]

A 3.00 x 18 is an old size tire. The modern equiv. is 90/90x18. If that tire is truly years old, I would not use it no matter how much tread is on it or how "New" it looks. Just not safe.

Any XS400 front MC and caliper from '77 on should fit. If not, others will chime in. The difficult part will be finding a front hub for spokes and disc.

 

[Charles]

FYI, some brand new tires are still labeled with the old style sizing. I have a 3.00x19 on my Harley that I bought brand new a year ago.

 

[drewpy]

same here with the tracker tyres

 

[xschris]

Mine as well

 

[OliverB]

Then I stand corrected! Just wanted to caution against using an old tire.

 

[robertmcw]

I have a set of forks from a 1980 Yamaha XS400 you can use. The right fork tube is set up with a disk for the caliper. The chrome looks really good and they don’t leak and the springs feel tight. I was going to use them with my XS360 but they are about an inch too long. The 33mm tubes will fit your bike. If you interested, I can send you a couple of photos. The rubber caps are missing. I can sell you for them for $50.00.

Robert