Why do people use different tire sizes than stock...? ? ?

[radguzzi]

I happened to notice that the front tire on the New-To-Me EV is checked, slightly but enough to bug me, the rear I wearing out fast too as I put miles on it. 

So I looked in the owner's manual for tire sizes and sure enough, the rear differs from that manual.  Not a great deal but enough to make me wonder why owners insist on making such odd changes...?  Don't they trust the Italian Engineers that think these sizes are best for this particular motorcycle..?

I will go with the stock 150/70-17 and 110/90-18 ME 880's, if I can find them.

Ciao,
Rob

[oldbike54]

 Smaller for quicker handling , larger for , well , mostly looks .

 Dusty

[guzzinka]

I (and many folks here) were forced to go from the "stock" 140 rear to a 130 on the Jackal because a new 140 doesn't fit!  Apparently a special batch of metzlers was made for guzzi in the 90s ugh.  Even the 130 clears with only 2 or 3 mm

[Perazzimx14]

Smaller for quicker handling , larger for , well , mostly looks .

 Dusty

DR650's have freakishly narrow 120 rear tire. Its not uncommon to bump to a 130 not for looks but for some more tire in the dirt or on the road for traction. Also not uncommon to run 120 front 150 rear on the DR setup w/ supermoto wheels

[Kiwi_Roy]

I (and many folks here) were forced to go from the "stock" 140 rear to a 130 on the Jackal because a new 140 doesn't fit!  Apparently a special batch of metzlers was made for guzzi in the 90s ugh.  Even the 130 clears with only 2 or 3 mm

:1:
I couldn't get a credit card between the Metzler and the frame on the EV I had
My local bike shop owner told me the same special Metzler story
I think I used a standard size Michelin to replace it and was very happy.

BTW those bikes are hard on wheel bearings, consider replacing those at the same time, cheap standard size.

[Perazzimx14]

I happened to notice that the front tire on the New-To-Me EV is checked, slightly but enough to bug me, the rear I wearing out fast too as I put miles on it. 

So I looked in the owner's manual for tire sizes and sure enough, the rear differs from that manual.  Not a great deal but enough to make me wonder why owners insist on making such odd changes...?  Don't they trust the Italian Engineers that think these sizes are best for this particular motorcycle..?

I will go with the stock 150/70-17 and 110/90-18 ME 880's, if I can find them.

Ciao,
Rob

Look no further:

http://www.americanmototire.com/catalog/index.php?cPath=33_165_172

[LowRyter]

Smaller for quicker handling , larger for , well , mostly looks .

 Dusty

I hate to say I agree with Dusty anymore than Lannis.  But I do.   

[rdbandkab]

Our 2015 Caponord 1200 came stock with a 180/50 on the rear and put our speedo off about 8%..  Installing a 190/50 brought the discrepancy down to a slightly more reasonable 5%.   I think aprilia spec'd the 190 on the next model year.

[Northern Bill]

I ordered stock tires for my Honda GB500. When they arrived the dealer phoned me and apologized because they had sent tires that were too narrow. I asked them what size they were and they were as I requested.  I told him to put them on. The bike handled better right away compared to the wider tires that were fitted by the previous owner. 

I also read somewhere in Ian Falloon's Sport And Le Mans Bible that the Le Mans handles much better with the narrower tires. It makes you wonder about the handling of many of the Moto Guzzi cafe racers out there with huge horsepower gains and much wider tires.

[twowings]

Let's ask this guy:

[oldbike54]

DR650's have freakishly narrow 120 rear tire. Its not uncommon to bump to a 130 not for looks but for some more tire in the dirt or on the road for traction. Also not uncommon to run 120 front 150 rear on the DR setup w/ supermoto wheels

 Lets parse this out . It is true that in really soft dirt a slightly wider tire with a more aggressive tread pattern will offer more traction . However on pavement traction and contact patch size have no relationship . Motorcycles that are capable of great lean angles, like sport and racing bikes employ wide tires for a just a couple of reasons .  The main being that increasing tire width allows for a more gentle transition as the bike leans over . Greater lean angles require a slower decrease in tire radius to keep the bike from rolling over way too rapidly . A 120 tire of the same brand and compound provides the same level of traction as a 200 section tire .

 Dusty

[giusto]

Let's ask this guy:

Hoy Hoy I'm the boy....your getting 300 pounds of heavenly joy! Chester Burnett AKA Hw

[Aaron D.]

I happened to notice that the front tire on the New-To-Me EV is checked, slightly but enough to bug me, the rear I wearing out fast too as I put miles on it. 

So I looked in the owner's manual for tire sizes and sure enough, the rear differs from that manual.  Not a great deal but enough to make me wonder why owners insist on making such odd changes...?  Don't they trust the Italian Engineers that think these sizes are best for this particular motorcycle..?

I will go with the stock 150/70-17 and 110/90-18 ME 880's, if I can find them.

Ciao,
Rob

I went from 150 to 140 880s on my old EV, it made it into a much better bike. All the other Calis of that year used the 140, and I hated it with the 150.

I figured it was for looks.

[Arizona Wayne]

I change front/rear tire sizes quite often on my 8 bikes.   Why?, to get more mileage out of them or to change their gearing for same or to change their handling.

MY `81 CX100 (LM II) came with a 110/90 rear & 100/90 front.  It now has a 120/90-18 rear & 110/90-16 front for better high mileage and faster front turning, like my `87 LM IV had.

My `91 VX800 came with a 150/70-17 rear & 110/80-17 front.  It now has a 130/90-17 rear & 110/90 front for longer tire mileage and it handles better too + changing the rear tire that much was like giving me another 500 rpm taller 5th gear, thus saving tire mileage & motor wear.

My `2000 MuZ 660 single came with a 150/60-17 rear.  I put on a 140/70-17 rear tire on for taller gearing + 3 teeth less on rear sprocket.  This is the best handling bike I've ever owned!

I change tire sizes to change gearing on shaft drive bikes for economy and handling as I see fit.  Being an ex-amateur road racer I can feel the differences and get what I prefer w/o spending a bundle of $. 

[radguzzi]

I went from 150 to 140 880s on my old EV, it made it into a much better bike. All the other Calis of that year used the 140, and I hated it with the 150.

Interesting Aaron,
You are correct, all the other Cali models on that year were equipped with the 140, no idea why... 

I think I will go with the 140.  I did go have a look at the '9 EV Hack and that has a130 on the rear.   The times that I have had motorcycles with wider tire than they were designed to use, they felt truckish and the steering was slow and odd, just my assessment.

Thanks,
Rob

Look no further:

http://www.americanmototire.com/catalog/index.php?cPath=33_165_172

Thanks...

 
BTW those bikes are hard on wheel bearings, consider replacing those at the same time, cheap standard size.

Yup, I always check and replace if needed but thanks for the reminder.

Best,
Rob

[Kiwi Dave]

Not a great deal but enough to make me wonder why owners insist on making such odd changes...?  Don't they trust the Italian Engineers that think these sizes are best for this particular motorcycle..?

It wouldn't be the first time that the Italian Engineers stuffed up the design on this model.  Hydraulic lifters and single plate clutch comes immediately to mind.

I found the stock 150/70 rear on my EV Touring made the bike slightly unstable at higher speeds, enough to not want to go any faster.

Because the earlier versions used a 140/80, I switched to that size with a noticeable improvement.

I've also had issues with Metzlers being too wide for the rim on other models, so chose Bridgestone BT45s.

[Rough Edge racing]

Lets parse this out . It is true that in really soft dirt a slightly wider tire with a more aggressive tread pattern will offer more traction . However on pavement traction and contact patch size have no relationship . Motorcycles that are capable of great lean angles, like sport and racing bikes employ wide tires for a just a couple of reasons .  The main being that increasing tire width allows for a more gentle transition as the bike leans over . Greater lean angles require a slower decrease in tire radius to keep the bike from rolling over way too rapidly . A 120 tire of the same brand and compound provides the same level of traction as a 200 section tire .

 Dusty

  It all sounds good...but....a larger section tire has a larger radius and I believe that gives more rubber on the road as the bike leans over... At least that's the way I see it...

[Groover]

MY `81 CX100 (LM II) came with a 110/90 rear & 100/90 front.  It now has a 120/90-18 rear & 110/90-16 front for better high mileage and faster front turning, like my `87 LM IV had.

Did you fit the 87 Lemans Wheels on the CX, maybe just the front? Intrigued.

[Arizona Wayne]

 . A 120 tire of the same brand and compound provides the same level of traction as a 200 section tire .

 Dusty
[/quote]


That depends on how much torque/hp the motor has that's using it.  A fatter tire has more rubber on the road to handle more power. 

[Arizona Wayne]

Did you fit the 87 Lemans Wheels on the CX, maybe just the front? Intrigued.

It was a 16" rim off a T4 or 5.  I had to lower the CX calipers w/alum. strips but it works good and the other rim brake rotors are much lighter than the original CX iron discs.  Rodekyll is here and may be able to take a pic of my CX front end to send here to Wildguzzi soon if interested to see it.

[oldbike54]

 Once again , contact patch size has nothing to do with traction . The only factors involved in traction are how hard or soft a tire is , and the force being applied to the contact patch . Increasing contact patch size decreases the force per sq MM of contact patch , thereby negating any gains from increasing the area . Basic physics , we've been over this several times . Racing cars and bikes run huge wide tires so they can use incredibly soft compounds and still last a few miles  , and MC's run wide tires for the aforementioned reason also .

 Dusty

[Arizona Wayne]

Once again , contact patch size has nothing to do with traction . The only factors involved in traction are how hard or soft a tire is , and the force being applied to the contact patch . Increasing contact patch size decreases the force per sq MM of contact patch , thereby negating any gains from increasing the area . Basic physics , we've been over this several times . Racing cars and bikes run huge wide tires so they can use incredibly soft compounds and still last a few miles  , and MC's run wide tires for the aforementioned reason also .

 Dusty

Sorry, Dusty, but I disagree.   Decades(late 60's) ago I had a friend that had a 496 Chevy Chevelle he put stock car racing mags & tires on.  It totally transformed the traction of that car from it's original narrow street tires and the car handled like a true race car then from just that alteration.  Those tires lasted quite a while too.   With those tires he could not chirp the rear tires any more nor light them up as before. w/street tires.

[oldbike54]

Sorry, Dusty, but I disagree.   Decades(late 60's) ago I had a friend that had a 496 Chevy Chevelle he put stock car racing mags & tires on.  It totally transformed the traction of that car from it's original narrow street tires and the car handled like a true race car then from just that alteration.  Those tires lasted quite a while too.   With those tires he could not chirp the rear tires any more nor light them up as before. w/street tires.

Wayne , those tires were softer than the original hard narrow tires . Once again , this is basic physics . Now , if you can break or bend those laws , then maybe the discussion will change 

 Dusty

[ponti_33609]

Was common in early v11 sports to go a size smaller than stock on the rear for improved handling. I did when I swapped and it did handle noticeable better.  I love my v7 but there are days I miss this.




Sent from my iPhone using Tapatalk

[Aaron D.]

Once again , contact patch size has nothing to do with traction . The only factors involved in traction are how hard or soft a tire is , and the force being applied to the contact patch . Increasing contact patch size decreases the force per sq MM of contact patch , thereby negating any gains from increasing the area . Basic physics , we've been over this several times . Racing cars and bikes run huge wide tires so they can use incredibly soft compounds and still last a few miles  , and MC's run wide tires for the aforementioned reason also .

 Dusty

You are correct as far as friction goes-but tires are not just friction devices, they actually "gear" into the pavement, and the new force is shear.

A greater patch in shear will certainly allow more force to be transmitted.

[oldbike54]

You are correct as far as friction goes-but tires are not just friction devices, they actually "gear" into the pavement, and the new force is shear.

A greater patch in shear will certainly allow more force to be transmitted.

 Think about what you just said Aaron ? The only way to increase shear is to increase the load , or make the tire softer . Making the contact patch larger simply spreads the load out , thus negating the effect of a larger contact patch .

 Dusty

[Robert]

496 Chevy Chevelle


New math?

[Arizona Wayne]

496 Chevy Chevelle


New math?

No, old memory.  What was it, 396?  My brain memory is sometimes suspect, but you get the idea..

[Rough Edge racing]

 Drag racing, wider tires of the same compound as more narrow tires ,will hook up better off the line..In this case is must be a larger contact patch giving better traction..?

[oldbike54]

Drag racing, wider tires of the same compound as more narrow tires ,will hook up better off the line..In this case is must be a larger contact patch giving better traction..?

 The force of friction is equal to the product of normal force and the coefficient of friction .

 Basic physics , contact area never shows up in the equation .

 The force per unit area is all that matters .

 Dusty