Page 1 of 1

Mag and spoke drum interchangeable?

Posted: 17 Aug 2017 07:04
by holeinthehead
Hey all,
Mid-way through getting my Christmas present back on the road and I'm planning ahead for a spoke order to rebuild the crusty wheels. I may have a lead on a drum brake mag rear wheel (not sure if there was ever a rear disc brake) and may get it on in the interim - the front wheel isn't too far gone and can get by with a little scouring.

The wheel in question is a Grimeca 18" and I thought it might just take the drive and brake without any fuss. Anyone know better?
Thanks in advance.

Re: Mag and spoke drum interchangeable?

Posted: 17 Aug 2017 07:25
by 72degrees
There were two rear hub/brake sizes on the spoked wheel 350 machines and two versions of sprocket carrier (5 bolt and 6 bolt). If yours is 5 bolt then a cast wheel uses the same brake shoes, spindle and cush drive rubber so I'm guessing it should fit though I've never done it. Someone who knows for sure will be along in a moment. By the way, make sure it is a 350 wheel. The 250 twin uses only a 1.85 rim rear cast wheel and a 5 bolt sprocket carrier.

Re: Mag and spoke drum interchangeable?

Posted: 17 Aug 2017 08:49
by MickeyMoto
Later bikes disc rear.

Re: Mag and spoke drum interchangeable?

Posted: 17 Aug 2017 09:30
by Ming
72degrees wrote:T...The 250 twin uses only a 1.85 rim rear cast wheel and a 5 bolt sprocket carrier.
... unless you have one with a 1.85 rim and a 6 bolt carrier... :wink:

Re: Mag and spoke drum interchangeable?

Posted: 17 Aug 2017 11:23
by huub
depends on what spoked rear wheel you have.
the 180 mm sport drum sprocket carrier fits the cast wheel, , the 160 mm strada drum sprocket carrier doesn't.

Re: Mag and spoke drum interchangeable?

Posted: 17 Aug 2017 12:20
by 72degrees
Ming wrote:
72degrees wrote:T...The 250 twin uses only a 1.85 rim rear cast wheel and a 5 bolt sprocket carrier.
... unless you have one with a 1.85 rim and a 6 bolt carrier... :wink:
D'oh - quite correct! 6 bolt on the 250 and the early Strada drum sprocket carrier

Re: Mag and spoke drum interchangeable?

Posted: 17 Aug 2017 12:22
by 72degrees
huub wrote:depends on what spoked rear wheel you have.
the 180 mm sport drum sprocket carrier fits the cast wheel, , the 160 mm strada drum sprocket carrier doesn't.
That makes sense. The 160mm Strada sprocket carrier is 6 bolt not 5.

Re: Mag and spoke drum interchangeable?

Posted: 18 Aug 2017 04:07
by holeinthehead
Thanks all, I thought it might be a specific fit. My spoked rear is a 6 bolt sprocket - I'll measure the drum tomorrow. The cast wheel I'm looking at is a E-1.85x18" DOT-D if that means anything.

Re: Mag and spoke drum interchangeable?

Posted: 18 Aug 2017 06:09
by 72degrees
holeinthehead wrote:Thanks all, I thought it might be a specific fit. My spoked rear is a 6 bolt sprocket - I'll measure the drum tomorrow. The cast wheel I'm looking at is a E-1.85x18" DOT-D if that means anything.
That sounds like it could be a 250 cast wheel, which would be confirmed by it having 6 'vanes' on the driven side and 160mm brake, so in theory it would fit a 6 bolt spoked wheel sprocket carrier, but would be restricted on the tyre width you could fit. However, the 250 uses a completely different rear wheel spindle and the part number for the brake plate is different (though the shoes are the same) to the 350 160mm version - so there may be issues when you came to put it in.

Having said that, I did once put a complete 180mm Sport spoked rear wheel and carrier in to a 250 swing arm (for the Rotax-Morini) - but it required a bit of ingenuity by modifying the nut for the 'dummy spindle'.

Re: Mag and spoke drum interchangeable?

Posted: 20 Aug 2017 05:20
by holeinthehead
WELL - as luck would have it, I came across a 36 spoke Borrani rim at a swap meet yesterday or $20. So that takes out the refurb on the old rim out of the equation - I can just make the swap and maybe I'll come across it's narrower counterpart one of these weekends.
Will still do some measuring, it'd be good to know I can make a change if I need to.
Thanks all

Re: Mag and spoke drum interchangeable?

Posted: 21 Aug 2017 11:22
by 72degrees
holeinthehead wrote:WELL - as luck would have it, I came across a 36 spoke Borrani rim at a swap meet yesterday or $20. So that takes out the refurb on the old rim out of the equation - I can just make the swap and maybe I'll come across it's narrower counterpart one of these weekends.
Will still do some measuring, it'd be good to know I can make a change if I need to.
Thanks all
Which reminds me that I have an old, but sound, Akront non-valanced 2.15 x 18 36 spoke holes, drilled for a Morini, alloy rim in the shed if anyone can make use of it. Can't remember for sure but probably off a 180mm rear hub wheel I had on the Rotarini racer.