Ambo tires'size combo

[arveno]

Hi All,

I am in the market for new set of tires for my Ambo and i was wondering what tires'size combo do you prefer ?

ant 100/90/18  rear 110/90/18

or  110/90/18  rear  120/90/18

Also even tho i am a big fan of metzeler , i am curious about the bridgestone BT45 ,the aspect is 80 instead of 90 what do you think about them ?

Thank you very much ( I posted the same question on the loopframe group but posted it here for those one that are not members of that group , i hope you guys dont mind. )

Best
Marco

[Yeahoo Whoyah]

Front:  [100/90-18]
Rear: [110/90-18]

[rodekyll]

 :+1

They like skinny.

[oldbike54]

:+1

They like skinny.

Me too  :o ;D

  Dusty

[Perazzimx14]

100/90-18  & rear 110/90-18 is what I run on the Eldo, 850T and soon the T3.

[lomax]

I am not sure if the specs are the same but on my 74 Eldo I run the factory recommended size of 110/90x18 front and back.

Gee I wonder why their engineers picked that size instead of something else mismatched.  ::)

Marc

[Perazzimx14]

I am not sure if the specs are the same but on my 74 Eldo I run the factory recommended size of 110/90x18 front and back.

Gee I wonder why their engineers picked that size instead of something else mismatched.  ::)

Marc

With Guzzi's day to day sometimes built consistency back then I surprised each year isn't different.

[rodekyll]

There are times when matched tires wouldn't do at all.

[Antietam Classic Cycle]

I am not sure if the specs are the same but on my 74 Eldo I run the factory recommended size of 110/90x18 front and back.

Gee I wonder why their engineers picked that size instead of something else mismatched.  ::)

Marc

The factory recommended tires were actually 4.00-18. 4.00-18 isn't quite the same as a 110/90-18 - both width and aspect ratio are different. Close, but not the same.

I've been running "mismatched" tire sizes on my Loop for the last 70k miles. Time and (tire technology) moves on and  things have changed considerably since '74.   

[grebmrof]

I am not sure if the specs are the same but on my 74 Eldo I run the factory recommended size of 110/90x18 front and back.
Gee I wonder why their engineers picked that size instead of something else mismatched.  ::)
Marc

I thought loop frame stock tires were 4.00x18 and that, that was equivalent to 120/90x18 today - so that a 110/90x18 is smaller and lighter steering and a 100/90x18 even smaller still.  My '74 is running 110/90x18s both front and rear and steers lightly.  I was thinking of going back to "stock" sizes (120/90) when these tires are kaput.  So, is not a 120/90 a "stock" size for the loops?

[Antietam Classic Cycle]

Purely by calculating, a 120 is 4.72" wide, a 110 is 4.33" wide. But a 4.00-18 may not actually measure 4.00". For instance: an Avon Roadrider in 4.00-18 size is 116 mm/4.6" wide, 671 mm/26.4" in diameter. Same tire in 120/90-18 is 129 mm/5.1" wide and is 675 mm/26.6" in diameter.

[grebmrof]

Hi Charlie,
So from your note...therefore a 110 is closer to the original 4.00 in width than is a 120/90, but a 110 has an aspect ratio that is a bit smaller than the older 4.00's did and that is why they don't fill the fenderwell as much as did the old 4.00's? 

As you probably remember my '74 carries an '83 CaliII engine with sump spacer bringing the sump closer to the ground - which has resulted in some broken fins on the sump.   (I now have a new/used sump to put on, but...) I know I could remove the spacer to give me more ground clearance, but I sort of like it and because the 110/90's that are on the bike are getting close to replacement time, I thought of going to 120/90's to get slightly more height - sump to ground clearance.  Now I am thinking that, that might not be a very good idea because of how much wider the 120/90 is than the older 4.00's.  Think there are any 120/90's out there that are very close to the sizes of the original 4.00's?

Thanks,
Tom

OP, sorry for the thread hijack.

[oldbike54]

Formberg , your question doesn't compute  ???

  Dusty

[grebmrof]

Formberg , your question doesn't compute  ???
Dusty

Dusty, help me say it correctly.  I thought I was saying what I needed to in my note...  Where does my note go goofy?  
Thanks, Tom

[Antietam Classic Cycle]

I'm putting the same engine in my next Loop and will not be fitting a sump spacer for ground clearance reasons.

My experience with a 120 on the front is that it makes steering very high effort. My preference is a 110/90 front and 120/90 rear - more ground clearance than a 100/110 or 110/110 combo and isn't that much more "slow" steering.  

[oldbike54]

Dusty, help me say it correctly.  I thought I was saying what I needed to in my note...  Where does my note go goofy?  
Thanks, Tom

Tom, by definition a 120 metric sized tire is going to be wider than a tire sized with the old system at 4.00 , in fact almost 3/4 wider if the measurements are done correctly .

  Dusty

[Antietam Classic Cycle]

Tom, by definition a 120 metric sized tire is going to be wider than a tire sized with the old system at 4.00 , in fact almost 3/4 wider if the measurements are done correctly .

  Dusty

See the measurements I provided (straight from the Avon website).

Purely by calculating, a 120 is 4.72" wide, a 110 is 4.33" wide. But a 4.00-18 may not actually measure 4.00". For instance: an Avon Roadrider in 4.00-18 size is 116 mm/4.6" wide, 671 mm/26.4" in diameter. Same tire in 120/90-18 is 129 mm/5.1" wide and is 675 mm/26.6" in diameter.

[grebmrof]

Tom, by definition a 120 metric sized tire is going to be wider than a tire sized with the old system at 4.00 , in fact almost 3/4 wider if the measurements are done correctly .
Dusty

OK, so by definition the 120 is not only quite a bit wider than the old 4.00, but maybe so wide as to not have enough clearance within the fender and the stays I guess you're telling me.  And going to a 120/90 would make the loop steer like a truck.  So, then as Charlie advises, staying with a 110/90 on the front and maybe moving to a 120/90 on the rear should work just fine...and then I probably ought to remove that sump spacer to give myself proper sump to ground clearance.  I was hoping to get the look of the old 4.00 sized tire at both ends and in the process provide a bit more ground clearance but not deteriorate the handling - and that just can't be done.  Thanks Dusty and Charlie.

[Antietam Classic Cycle]

OK, so by definition the 120 is not only quite a bit wider than the old 4.00, but maybe so wide as to not have enough clearance within the fender and the stays I guess you're telling me.  And going to a 120/90 would make the loop steer like a truck.  So, then as Charlie advises, staying with a 110/90 on the front and maybe moving to a 120/90 on the rear should work just fine...and then I probably ought to remove that sump spacer to give myself proper sump to ground clearance.  I was hoping to get the look of the old 4.00 sized tire at both ends and in the process provide a bit more ground clearance but not deteriorate the handling - and that just can't be done.  Thanks Dusty and Charlie.

A 120 clears the fender and stays okay, but there's not much space on either side.

If running a sump spacer, I'd at least fashion a skid plate. 

[garbln]

On my 1970 Ambo I'm running Dunlop 404's, 110/90 front and 120/90 rear with no problems.  Not even close to hitting anything.

[arveno]

http://www.thisoldtractor.com/moto_guzzi_loopframe_tire_size_to_use_in_a_loopframe.html

[grebmrof]

On my 1970 Ambo I'm running Dunlop 404's, 110/90 front and 120/90 rear with no problems.  Not even close to hitting anything.

garbln - the only reason I've suffered some broken sump fins (outside right on two different sumps) is because of the spacer between the sump and engine - so the prudent thing to do is to remove that spacer and the tire sizes I am running (at 110/90 at both ends) are fine - but I probably will leave a 110/90 on the front and go to a 120/90 for the rear as Charlie recommends.  Now I did see that I could get one of the old design ContiTwins K112 in 4.00x18 and run them on both ends - but no doubt, that would degrade this thread into a deeper tire debate and how horrid the old ContiTwins were.  Please hold you expert opinions on that score, please.

[acogoff]

     I have found that every tire brand and series has it's own handling characteristics relative to the front to back sizes. My advice would be to decide what handling do you prefer, I mean how would you want handling to be different from what you have now and adjust the front tire size to achieve this preference. Example is smaller front = quicker steering(turn in) or larger front + more bus like stability. If you change brand and series tire from what you have now then all bets are off and the advice would be to go with the stock size in the new type of tire and down the road change your front size to tweek your handling of that particular tire series and brand. 

[Antietam Classic Cycle]

garbln - the only reason I've suffered some broken sump fins (outside right on two different sumps) is because of the spacer between the sump and engine - so the prudent thing to do is to remove that spacer and the tire sizes I am running (at 110/90 at both ends) are fine - but I probably will leave a 110/90 on the front and go to a 120/90 for the rear as Charlie recommends.  Now I did see that I could get one of the old design ContiTwins K112 in 4.00x18 and run them on both ends - but no doubt, that would degrade this thread into a deeper tire debate and how horrid the old ContiTwins were.  Please hold you expert opinions on that score, please.

K112s are made in Korea now, along with many other Continentals. Put one on the back of a customer's BMW and he says it sticks better than the old K112, but that ain't saying much.  ;) K112 is twice the price of a Shinko (also made in Korea) and not any better, IMO.

[Groover]

I don't have an Ambo or Eldo (someday), but I have been obsessing and researching tires lately for my G5, and I think I may be able provide something here:

Michelin Activ Pilot does offer a 4.00-18 (Rear) if you want to stay skinny and keep the height, but not an equivalent for the front. If you want to widen thing a little and add height, then I would also suggest you take a look these same tires in a 110/90-18 Front and 120/90-18 Rear. If you want to look at the a different brand, then the Shinko 230 Tour Master 110/90/18 Front and 120/90/18 Rear also advertise the exact specs as the Michelin Activ Pilots.

The Avons... Not sure what they are thinking, but they sizes are just a little different in every way - I do like the Roadriders (I had them on a different bike in the past), but for the sizes needed for our bikes, now matter which you look at in that line that will physically fit our swingarms and rims, you'll be riding just a little lower to the ground than the other two brands in those similar sizes.

Here is a chart for the Michelins.




Good luck, and I hope that helps some.

[Groover]

Upon further measurement comparisons and since you are considering the Bridgestone BT-45, looks like the following sizes may be good options to what you are trying to achieve:
 
BT-45 Front: 3.50-18 (Overall Diameter 651mm, width 104mm)

BT-45 Rear: 4.00-18 (Overall Diameter 675mm , Width 117mm)

That actually gets you taller than the tallest 120/90 that I've come across during this "research" and almost as wide, and almost as tall as the tallest 110/90, and they are also Tube Type rated.

Charlie has actually recommended this tire to me a few times I believe  ;D, and now that I've actually looked at the nitty-gritty specs, I'm liking these sizes for my bike!

Here is the full chart: http://www.bridgestone.com/products/motorcycle_tires/products/battlax/bt45.html


Edit: And...... I just realized that I confused the OP's questions with a another question that popped up down the line - either way, I hope this information helps someone!  :BEER:

[garbln]

garbln - the only reason I've suffered some broken sump fins (outside right on two different sumps) is because of the spacer between the sump and engine - so the prudent thing to do is to remove that spacer and the tire sizes I am running (at 110/90 at both ends) are fine - but I probably will leave a 110/90 on the front and go to a 120/90 for the rear as Charlie recommends.  Now I did see that I could get one of the old design ContiTwins K112 in 4.00x18 and run them on both ends - but no doubt, that would degrade this thread into a deeper tire debate and how horrid the old ContiTwins were.  Please hold you expert opinions on that score, please.

Huh?