SF - SG wheel change(?)

[UncleSpot]

'just picked up a 1979 (XS1100) SF 17" rear wheel, and I own a 1980 (XS1100) SG (16" rear wheel on the bike)

My question: can you use the 17" wheel on the 16" mc? ...for better MPG, 'taller' gears, etc... anyone ever tried this?

[Czekus21]

My 79sf has a 16 inch rear and 19 inch front. Hope this helps

[Bill__Woods]

I believe all the specials came with the 16 inch wheels. Most likey the 17 inch wheel is off a Standard . I am not certian if you can put a 17 incher on a special, but someone around here knows I bet.
Personally I would need Gene Simmons boots if my bike was any taller. At 5'8 I got just enough reach to be comfortable on the bike.
let us know if it works!

[rover]

You will gain very little in your gear ratio, probably not enough to notice. You bike will lean farther when on the kickstand. There should be enough room in the swingarm, and it will be easier to get it on the center stand. Brakes should work the same, but not real sure of this.

[Dennyz]

The 16" and 17" rim can be interchange. To do a straight bolt on swap, the spacer, bearing cap, caliper brace and maybe the caliper mount need to be of the same model as the rim.

[iron_llama]

Originally posted by Dennyz
The 16" and 17" rim can be interchange. To do a straight bolt on swap, the spacer, bearing cap, caliper brace and maybe the caliper mount need to be of the same model as the rim.

That's good to hear. I've got the larger wheel on my Standard (in AZ, if UncleSpot is interested in a swap) and I'd like to put on the smaller wheel- the bike just sits a few inches high for my taste.

Have you done the swap? I get the feeling I'll need to ask someone for advice once I start.

Thanks,
-M

[jetmechmarty]

I don't expect there's really much difference in the wheel diameter between the Special and the standard. I'd run the numbers, but I don't know what tire size goes on the standard.

Width*aspect ratio=sidewall height*2+wheel diameter=tire diameter

1 inch = 25.4 mm

Of course, the tire manufacturers only get close, so these numbers are not always exact.

[Renegade]

Re: SF - SG wheel change(?)

Originally posted by UncleSpot
'just picked up a 1979 (XS1100) SF 17" rear wheel, and I own a 1980 (XS1100) SG (16" rear wheel on the bike)

My question: can you use the 17" wheel on the 16" mc? ...for better MPG, 'taller' gears, etc... anyone ever tried this?

If you have a special with a 17" rear, then someone has already performed the swap on that one. Specials are all 16" rear wheel. From what I have read, it doesn't make very much difference in speed or economy going from the 16" to a 17" rear wheel.

[Geezer]

Re: Re: SF - SG wheel change(?)

Originally posted by Renegade
From what I have read, it doesn't make very much difference in speed or economy going from the 16" to a 17" rear wheel.

I disagree. I put a 17" on the back of my 80 Special and while it only dropped 600 or so RPM at 65 MPH, crusing at the speed is a lit less buzzy.

On the down side my center stand is less usefull and I needed to add spacers to the headlight adjuster in the windjamer faring.

Geezer

[Renegade]

Re: Re: Re: SF - SG wheel change(?)

Originally posted by Geezer


I disagree. I put a 17" on the back of my 80 Special and while it only dropped 600 or so RPM at 65 MPH, crusing at the speed is a lit less buzzy.

Geezer

I guess it depends on the perspective. I got used to machinery that had to rev to make power. I had one bike a few years ago that the tach and speedo read the same in 5th gear. 110mph was 11000rpm. Take a bike like that on a 300 mile trip with loud pipes and you learn to love the big torquers real quick. After years of riding stuff like that, 500 rpm difference is barely noticeable.

[Geezer]

Re: Re: Re: Re: SF - SG wheel change(?)

Originally posted by Renegade


I guess it depends on the perspective. I got used to machinery that had to rev to make power. I had one bike a few years ago that the tach and speedo read the same in 5th gear. 110mph was 11000rpm. Take a bike like that on a 300 mile trip with loud pipes and you learn to love the big torquers real quick. After years of riding stuff like that, 500 rpm difference is barely noticeable.

My old Guzzi was 4k RPM at 80 MPH. I do miss that bike...

Anyway at 65 MPH the drop in RPM with the bigger tire & wheel is worth the effort to me. I already had the wheel and I scored 3 Avon 130-90-17" rear tires for under $150. I'm keeping the 17" rear wheel at least until I run out of tires.

Geezer

[Renegade]

Re: Re: Re: Re: Re: SF - SG wheel change(?)

Originally posted by Geezer


My old Guzzi was 4k RPM at 80 MPH. I do miss that bike...
Geezer

Yep, I know what you mean there. We have 2 Guzzi's here, a V11 Bassa and a heavily modified V65. Some PO spent a lot of money on performance work on the V65...12:1 pistons, Daytona cam, Dyna ignition, V50 gearing, and probably a good bit more that we haven't discovered yet. Carbs are beyond help (last owner parked it for 10 years in a barn and stacked bags of fertilizer on it. Aluminum and ammonia nitrate = massive corrosion). With good carbs, it should be about equal to my XS performance wise.

[Geezer]

Re: Re: Re: Re: Re: Re: SF - SG wheel change(?)

Originally posted by Renegade


Yep, I know what you mean there. We have 2 Guzzi's here, a V11 Bassa and a heavily modified V65. Some PO spent a lot of money on performance work on the V65...12:1 pistons, Daytona cam, Dyna ignition, V50 gearing, and probably a good bit more that we haven't discovered yet. Carbs are beyond help (last owner parked it for 10 years in a barn and stacked bags of fertilizer on it. Aluminum and ammonia nitrate = massive corrosion). With good carbs, it should be about equal to my XS performance wise.

Before I got back into riding and bought my XS11s, I parked my 1976 T3 in the back of the garage and piled boxes of miscellaneous junk on it. I had hoped to someday rebuild the engine and restore the bike but lately I'm thinking it's beyond help. Like I said before, I really miss riding it but not to the tune of a couple grand (or more) in Italian hardware.

Geezer

[Dennyz]

16" verses 17":

I have spent most of the last 5 years riding a Standard (17" rim) to the tune of 50K+ miles. A couple of weeks ago I did a nice 1500 mile ride on my newly acquired Special (16" rim). The two things I noticed most were the increased engine noise and improved deceleration/acceleration in and out of the turns.

I am a lugger, meaning I don't shift much. I like to stuff the XS into a turn and let the torque pull it out. The XS does this nicely. I notice my Special does this better than my Standard. I felt I scrubbed off speed faster when I let off and climbed out of the turn quicker.

On the open roads, I felt like I needed to shift the Special to a higher gear. The Standard has noticeably less vibration and engine noise at a given speed, say 65mph.

Both bikes seem to get around the same mileage (35-38mpg). Both are ‘79s and have 130x90 tires.

P.S.

If the rear wheels are swapped, make sure to swap the kick stands also, they are different.

[jetmechmarty]

Tell me what size tire is supposed to be on the standard and I'll post the calculations and the difference between the diameters of the Special vs. standard.

I need the metric rather than letter system.