Going from 16" disc mag to 18" spoke drum? Looking to trade?

[ChewsVolt]

This topic has generally been discussed all over this forum....but. I have a rear 16" disc mag. I want to go with a bigger rear wheel, it looks like bigger mag means running a 19" xs650 front or borrow from sr500 or other model with machining needs. I have no ability to machine anything so I think 18" spoke, with the appropriate swingarm would be the easiest conversion, right? (cuz there aint no disc version)?
I am starting on a project that I hope will fall in the brat/scrambler/desert sled/tracker vein. Wheel proportions are important. It appears most of the bikes I am looking at for inspiration have same diameter wheels front and rear. I will maybe downsize the front to an 18" as well.

Is that the easiest route to a larger diameter rear? Anyone looking to go mag want to trade?

 

[ChewsVolt]

El- Bump-o!

 

[ChewsVolt]

Might as well keep shouting into the dark- another question:
I am wondering what differences I will run into with rim size and spoke count from different years/models. So far it looks like the 82-83 heritage special has a 16" rear with 48 spoke? Any other anomaly years? I am thinking the earlier models have more of what I am looking for, 36 spokes, 18" rear.

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[650Skull]

All this relates to the rear wheel

Any Special, 79-83, rear spoke wheel has a 16" rim.
79-81 Special rear 16" spoke wheel has a 36 spoke hub.
82/83 Special rear 16" spoke wheel has the 48 spoke hub.

Any rim from 70 -79 are 36 spoke.
70-73 rim is Chrome on steel.
74-79 rims are Alloy, (Mud-catcher/shouldered/H style). All these rims are 18".

Rear 36 Spoke hubs are on 70 to 79 Standards and 79 to 81 Specials

Check out the classifieds for Hubs/rims or complete wheels

Set of wheels from a 75XSB.
http://www.xs650.com/forum/showthread.php?t=41866

It is a simple operation to convert from Mag disk brake rear to drum brake rear. The brake pivot mechanism has to be changed and the rear brake stay arm, is shifted from the top of the swing arm to the bottom

 

[ChewsVolt]

Thanks skull! Lots of helpful info. Are the spacers identical as well?
I was looking at a 1975 parts bike locally for 250. I shouldve picked that up just for the wheels
The next thing I need to consider is how geometry will change. I will probably lace 2.5x18 up front. Larger diameter rear and smaller front leads me to think I will pitch the bike forward, but I think change in rim/tire widths will slightly compensate for that.

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[650Skull]

Spacer on one side of the rear is different, spacers for the front wheel interchange. Check out the parts files HERE.
longer rear shocks has the same effect

 

[kopcicle]

http://www.xs650.com/forum/showpost.php?p=351885&postcount=3

18" x Whatever works 40 hole , drilled for conical hub is best . Actually an easy build .

I have spacer detail if needed ...

~kop

 

[650Skull]

ChewsVolt,I have this bookmarked, just found it. Shows the Mag disk brake rear conversion to spoke Drum rear conversion.

 

[fredintoon]

- - - I have a rear 16" disc mag. I want to go with a bigger rear wheel, it looks like bigger mag means running a 19" xs650 front or borrow from sr500 or other model with machining needs. I have no ability to machine anything so I think 18" spoke, with the appropriate swingarm would be the easiest conversion, right? - - -

Hi ChewsVolt,
swapping from 16" disc mag wheel to 18" drum wire wheel is dead easy so long as the 18" wheel comes with all it's hardware.
When we did that swap in my son's 1980 Special we welded an extra brake torque arm stay onto the disc brake swingarm to make the existing swingarm dual-purpose.
But bigger? Not by much.
Theoretical OD of a 130/90-16 tire is 25.2"
Theoretical OD of a 110/90-18 tire is 25.8"
If 0.4" taller at the back is what you want, OK.
Mind you, those aluminum rim wire wheels do look nice.
But you gotta keep cleaning the bastards, eh?

 

[650Skull]

fred, the whole idea of the cafe style wheels, from the 16" rear to the 18" is not for looks alone or the circumference of the wheel/tire but for canyon carving. Better cornering on the narrower 18". If the front wheel is reduced to 18", or taller rear shocks installed, it shifts the geometry of the bike on to the front wheel for quicker turn in.

16" is for highway stability.

 

[fredintoon]

fred, the whole idea of the cafe style wheels, from the 16" rear to the 18" is not for looks alone or the circumference of the wheel/tire but for canyon carving. Better cornering on the narrower 18". If the front wheel is reduced to 18", or taller rear shocks installed, it shifts the geometry of the bike on to the front wheel for quicker turn in.
16" is for highway stability.

Hi Skull,
yeah, BTDT & posted about the difference mebbe a decade ago.
But my understanding of the OP's post was that he was more interested in how his bike looked than how it cornered.

 

[ChewsVolt]

Awesome guys, this helps a lot. In terms of my motivation, yes you're both right, looks and handling characteristics. This bike will be for fun rides, a couple of hours at time, not a lot of freeway, seeking twisties IF I can get the chassis to feel right. I am sure new suspension front and rear is going to take me a long way...and new swingarm pivots
Skull thanks for that "how-to", should be linked or re-posted in our tech section
Fred- I was looking at your "theoretical OD" numbers and it became obvious to me how I could find those numbers myself for any tire size. Thanks for that.
My 100/90-19 front should be 26.1 (measured at 25.7ish)
Switching to a 110/90-18 would give me 25.8,
dropping the front 0.3. In total rear end is up .7 inches with both wheel size changes.
And yeah, cleaning spokes isn't a fun job. I like the look of them better, but if I could get this done easily on mags I would

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[fredintoon]

- - - yeah, cleaning spokes isn't a fun job. I like the look of them better, but if I could get this done easily on mags I would. - - -

Hi ChewsVolt,
agreed that wire wheels, especially the deep groove aluminum rim wire wheels do look real nice.
Keeping wire wheels clean just takes effort, after all; I went back to cast wheels so I can run tubeless tires which is not possible with normal wire wheels.
But if you want 19" wheels back and front there's a kit for that. If it'll work on wires it'll work on cast as the disk brake fronts all swap except for the '73.

 

[ChewsVolt]

I looked at the 19s, I didn't want to pay for Omar's conversion, and looking at my 19 front it looks a bit skimpy to run on the rear. Also I have ha 100/90-19 front on so many of my recent bikes I want to try some changes to this set-up.
Thanks again for all the info guys

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