35mm Tonti Front Ends General Design

[ozarquebus]

What if I wanted to swap a rebuilt Convert Front End onto a Square Head 1000SP II to get an 18" Wheel on the SP?

The Tonti Frame Front Ends that are 35mm seem to share many parts and some identical dimensions.

So I am trying to figure out if the spacing between the forks.

Probably need some modified axle spacers?

Are the heads and stems all the same between a 87 1000SPII and a 81 Convert?

[mtiberio]

I believe the steering head is longer on the SP II.

[Antietam Classic Cycle]

Aren't the fork tubes on the SP II 38 mm? All of them I've seen were.

[Two Checks]

They changed the neck of the SP II frame to accommodate the 16" tire.
Putting the 18" on would change the steering geometry.
I'm sure its been done, though.

[Cdn850T5NT]

All SP II's and 850 T5's have 38mm fork tubes, 16" frt wheels, and triple clamps to suit the 16" wheel with the strg axis offset Guzzi deemed appropriate for this set up. If your front end on your  SP II is misbehaving - try what Patrick Hayes and others have suggested - 37- 40 psi frt tire pressure... and Patrick seems to like the Bridgestone Battleax frt tire pattern. Said bike is sensitive to tire pressure and tread pattern.

If you go to the 35mm forks it'll be more flexible + you'll lose the factory fork brace.

[ozarquebus]

Sounded like a good idea at the time, now it sounds like a bad idea.

[Cdn850T5NT]

All SP II's and 850 T5's have 38mm fork tubes, 16" frt wheels, and triple clamps to suit the 16" wheel with the strg axis offset Guzzi deemed appropriate for this set up. If your front end on your  SP II is misbehaving - try what Patrick Hayes and others have suggested - 37- 40 psi frt tire pressure... and Patrick seems to like the Bridgestone Battleax frt tire pattern. Said bike is sensitive to tire pressure and tread pattern.

If you go to the 35mm forks it'll be more flexible + you'll lose the factory fork brace.

I guess my comments are moot because the steering head on a T5 and an SP II is the longer one. Early Tonti 35mm triple clamps / triple tree would not fit. Possibly Cal II ones might.

[Turin]

If you want to slow down the steering, you can fit a taller profile tire. Worked on my 750 Paso and on my '87 LeMans.

[acguzzi]

the stems can be swapped easily with a press

[Antietam Classic Cycle]

ozarquebus: There's a guy on Facebook with an SP II that has a Cal II front end on it. He's looking to swap it for the original SP II stuff. Maybe y'all can work something out?

Jeremy Brewer‎

 Moto Guzzi Classifieds | Buy, Sell, and Trade
18 mins ·

ISO front fork and wheel set up for a 1000 SP II. Wanting to revert this front end back... I believe that this may be a California II set up so willing to trade or make a deal. Working on cleaning it up so better pics to follow and please correct me on anything I may be wrong about. This is my first Moto Guzzi.

[Cdn850T5NT]

The source of the SP II frame was the 850 T5 NT (the Series III bike). When they went from Series II to Series III (16" rear wheel to 18" rear wheel) they kicked out the inclination of the frt steering head so that with the jacked up rear end - they'd maintain the Series II effective fork rake. If you go to an 18" frt wheel - the resulting rake will favour stability even more than just having an 18" wheel... and you may find it a pig to steer. I THINK my info is correct.

Just reading some of the earlier posts... I guess this was what Two Checks was saying...

[Groover]

The picture Charlie posted from the Facebook ad looks like a 16" rear which could be a T5? Doesn't change the front end or front end discussion, so you all carry on..

[Cdn850T5NT]

Yes but the steering head tube is NOT a T5 Series I or II (which did have a 16"rear wheel). This might be neither here nor there, so to speak, because it's a custom in any case... and parts could come from anywhere. Looks like a Cal II or early MilleGT frt end.

[ozarquebus]

Viewing the classified ad of the SP with a Cal II front end that Antietam posted makes obvious the difference in steering head offset extremes. Also after seeing other pix of this 18" FR wheel conversion done to SPs makes it look to me like a bad idea unless I'm looking for the "THEN CAME BRONSON" bobber look. (not me)

What about jacking up rear end  to maintain steering angle?? What would 3" longer shocks do to the rear drive shaft angle? The SP slowly begins to transform into fat Stornello? The idea is looking even worse.

[Cdn850T5NT]

If you want to change your '87 1000 SP II's frt wheel to an 18" for more stability at speed (rather than for aesthetics or for frt tire availability reasons) maybe consider what Turin said and what Patrick Hayes said... Turin suggests a higher profile ratio 16" tire and Patrick suggests OVER about 37 psig pressure.

Having said this - I'm not sure about the availability of, say, a 110/100-16... Looks poor.

[Cdn850T5NT]

You might consider Metzeler ME77 Perfect frt tire, 110/90-16 59S (I believe)... or H.  You may however have to import this from Germany or from the UK as it does not appear to be avail. in all countries.  It's twin - for the rear, though, is only avail. in a max width of 110/90-18... but this would still fit your rear 3.00 rim.  These tires look "classic" rather than the sportiest modern-day tires, but they apparently are modern-day build style and perform well.

[Turin]

I run a Bridgestone  Battlax 110/90 16 and keep the pressure at 38 psi.
Bike rides likes she's on rails and cuts into a turn like a champ.

[Cdn850T5NT]

Turin what rear tire type and size do you run... and on which bike?