Bicycle Mechanics - Is This Right?

I am installing a 7-Speed cassette on a new 8/9-Speed rear wheel that I just bought from Nashbar. I was also sold a 4.5mm spacer by Nashbar, and told I'll need to put it on the hub b/4 sliding in the cassette.

Well, I just got my wheel back from the tech that worked on de-stressing and tensioning the wheel, and he put two spacers, with a combined thickness of 3.5mm on the wheel, instead of the 4.5mm single spacer I had given him. He claims the 3.5mm spacers are gonna work better, and that the 4.5mm was way too thick.

I have not had time to ride the bike, so as to make sure the chainline and shifting both work well.

Is he right? Or, should I remove the two spacers (3.5mm total) he installed and replaced them with the single 4.5mm spacer Nashbar sold me?

Thanks for all responses.

Regards,

3.5mm is the correct spacer size. 4.5 would probably be too thick. Trust your tech. :)

Take your cassette off and take a look at it's backside. You'll probably see some bolt or rivet heads sticking up. The 4.5mm spacer that you bought is the right size after you remove the bolt or rivet heads.

Take your cassette off and take a look at it's backside. You'll probably see some bolt or rivet heads sticking up. The 4.5mm spacer that you bought is the right size after you remove the bolt or rivet heads.

There are indeed some rivet heads. The rivet heads were not taken off by the tech. And it was in fact, according to him, these rivet heads that dictated the size of the spacer. The 4.5mm spacer would not fit, because of the rivet heads, according to the tech, hence the 3.5mm.

Should the rivet heads have been taken off? And if so, how?

Regards,

There are indeed some rivet heads. The rivet heads were not taken off by the tech. And it was in fact, according to him, these rivet heads that dictated the size of the spacer. The 4.5mm spacer would not fit, because of the rivet heads, according to the tech, hence the 3.5mm.

Should the rivet heads have been taken off? And if so, how?

Regards,
Your tech is correct and the rivet heads do prevent the 4.5 mm spacer from allowing the lockring to seat if you put the spacers behind the largest cog. I used a 4.5 mm spacer to install a 7-speed cassette on an 8/9/10-speed freehub but I installed the spacer between the smallest cog and the lock ring and every thing fit fine and the bike shifts as well as ever.

Leave the rivets in place. They bolt the majority of the cogs together and make assembly easier as well as keeping the individual cogs from wearing the freehub body splines. Not terribly important with a steel freehub but absolutely essential with an Al body and very useful with a Ti body.

Should the rivet heads have been taken off? And if so, how?

I just grind them down with a bench grinder. My experience has been that the cassette still stays together. Even if it didn't, however, it would only require installing it piecemeal which wouldn't take very much additional time.

On the other hand, how does it work using a 3.5mm spacer? If it ain't broke maybe there's no need to fix it.