Boxerworks.com

What year did the axles change diameter on the /6 or was it /7? Was it both front and rear that changed?

And will a /7 rear drive fit my /5 with the smaller axle?

Front changed after '74 model year (or there about)

Rear was the same until it went to disc rear end.

Thx, I have to make an offer on a rear drive today, and want to make sure it would fit.

Yeah, I believe as long as it's not a disc one, should be fine.

Unless it's from one of those freak bikes. (R65 or R45)

Drum brake RS axle is the same diametre as a disc brake RS.
The step up on the drum axle is longer than the disc step up.
The drum axle is 8-10 mm shorter o/all than the disc axle.

That's my experience after receiving the wrong rear axle for my disc brake RS.
The supplier said "oops, I thought you had a drum brake RS"

Clymer covers wheels well , including changing from the early 15 mm spindle to the 17 mm.

Pity the guy at Cycleworks doesn't appear to have read it ---------.

The rear axle diameter will be the same and no problems in drum type to drum type, as other folks have said. The drive splines on the /6 and /7 final drives are a bit different than the splines on your /5 wheel. Unless you have also replaced the /5 wheel with a /6 or later. Not the best for extended mileage wear patterns. I believe the /6, /7's have a longer and possible wider spline. There may even be a fitting problem, if the mismathed sets of splines are new or nearly new, as in an in an interference fit?? Perhaps someone else will know for sure. I did use a 90/6 FD on my /5 for about a year or so and survived. I eventually went to new wheel and FD spline setup, both /5 style. I didn't replace them at the same time, but in retrospect it would have made more sense to replace them both with the superior /6, /7 style.

You may want consider replacing the wheel spline cup at this time if you still have the original /5 unit and it's pretty worn.
HTH!
hank2

I picked up the drive today and the splines look very good with no dicernable wear.

I did a tiny bit of surfing on the early/late spline isue and as far as I can tell the splines in the drive remained the same. The wheel splines got deeper in 74 to reduce wear. So if I run my /5 wheel on this drive for a long time with minimal lubrication, it will develop a wear pattern to match the /5 hub and be useless for a later hub down the road.

UPDATE:

I installed the /7 drive today on my /5 and used the /5 rear wheel. All went smoothly and I got in a quick ride after. I have not paid a lot of attention to the temperature of the rear drive before, but after about 5 miles on the highway I pulled over and the drive felt about as hot as the gearbox.

I came back home aand went upstairs and took off my gear then went down to she shop to double check everthing. After sitting for about ten minuets the drive was definatly cooler than the gearbox.

Everything spinns freely and quietly, so I asume that all is well. The 37/11 ratio sure wakes up my R75 compared with the 31/10 that came off.

Also it is clear to see the wear pattern on the splines of the drive that came out as the /5 hub only contacts about 2/3 of the available spline of the drive. I will need to find a /6 or later hub quickly or this drive will become a /5 only.

Or you could replace the spline on the hub with a later one...