Modern Buddy

What is the biggest size tire that has been installed on a buddy 150 or 125? And what mods were done in order to get it in there?

I've never heard of anything other than stock sizes being installed.

Extensive research indicates to me that a 130/70 10 will fit on the rear, fender removed. I think the biggest front tire is the 110/80 10 but not totally sure on that one. If you miss match the tire sizes you'll have 2 slightly different roll centers and could result in less than interesting handling. The 130 tire will have a flat puckered look due to the narrow rim. I'm going 100/90 10 in a heidenau k61.

lovemysan wrote:Extensive research indicates to me that a 130/70 10 will fit on the rear, fender removed. I think the biggest front tire is the 110/80 10 but not totally sure on that one. If you miss match the tire sizes you'll have 2 slightly different roll centers and could result in less than interesting handling. The 130 tire will have a flat puckered look due to the narrow rim. I'm going 100/90 10 in a heidenau k61.

I just installed a 120/90/10 on the rear, and it took quite a lot of R&D to get it in there, and stop it from rubbing. Now its in there and it's working great. No flat or cupped look on the tire either. I was hoping for a higher gear ratio thats I went with the 90 and it worked! I lost about 5mph on the top end but I'm complete ok with it because of the gain in handling. I'm sure I can make that back with some added HP or Trans Tuning. I've been on this project for about 2 days and I had some doubts. Soon I'll explore with the front as well.

buddyguy wrote:

lovemysan wrote:Extensive research indicates to me that a 130/70 10 will fit on the rear, fender removed. I think the biggest front tire is the 110/80 10 but not totally sure on that one. If you miss match the tire sizes you'll have 2 slightly different roll centers and could result in less than interesting handling. The 130 tire will have a flat puckered look due to the narrow rim. I'm going 100/90 10 in a heidenau k61.

I just installed a 120/90/10 on the rear, and it took quite a lot of R&D to get it in there, and stop it from rubbing. Now its in there and it's working great. No flat or cupped look on the tire either. I was hoping for a higher gear ratio thats I went with the 90 and it worked! I lost about 5mph on the top end but I'm complete ok with it because of the gain in handling. I'm sure I can make that back with some added HP or Trans Tuning. I've been on this project for about 2 days and I had some doubts. Soon I'll explore with the front as well.

Pics or it didn't happen?

Seriously, though, I'd like to see how it looks and get more info about what you've done and how it handles if you have the time.

jonlink wrote:

buddyguy wrote:

lovemysan wrote:Extensive research indicates to me that a 130/70 10 will fit on the rear, fender removed. I think the biggest front tire is the 110/80 10 but not totally sure on that one. If you miss match the tire sizes you'll have 2 slightly different roll centers and could result in less than interesting handling. The 130 tire will have a flat puckered look due to the narrow rim. I'm going 100/90 10 in a heidenau k61.

I just installed a 120/90/10 on the rear, and it took quite a lot of R&D to get it in there, and stop it from rubbing. Now its in there and it's working great. No flat or cupped look on the tire either. I was hoping for a higher gear ratio thats I went with the 90 and it worked! I lost about 5mph on the top end but I'm complete ok with it because of the gain in handling. I'm sure I can make that back with some added HP or Trans Tuning. I've been on this project for about 2 days and I had some doubts. Soon I'll explore with the front as well.

Pics or it didn't happen?

Seriously, though, I'd like to see how it looks and get more info about what you've done and how it handles if you have the time.

I haven't posted pics on here before so I'll give it a try. If you go to my FB account and like my page I'll go and upload a bunch of clearer pics. I only have on pic right now. FB account: https://www.facebook.com/DimeloMotorWorks

buddyguy wrote:

jonlink wrote:

buddyguy wrote: I just installed a 120/90/10 on the rear, and it took quite a lot of R&D to get it in there, and stop it from rubbing. Now its in there and it's working great. No flat or cupped look on the tire either. I was hoping for a higher gear ratio thats I went with the 90 and it worked! I lost about 5mph on the top end but I'm complete ok with it because of the gain in handling. I'm sure I can make that back with some added HP or Trans Tuning. I've been on this project for about 2 days and I had some doubts. Soon I'll explore with the front as well.

Pics or it didn't happen?

Seriously, though, I'd like to see how it looks and get more info about what you've done and how it handles if you have the time.

I haven't posted pics on here before so I'll give it a try. If you go to my FB account and like my page I'll go and upload a bunch of clearer pics. I only have on pic right now. FB account: https://www.facebook.com/DimeloMotorWorks

Shoot I don't know how to post pics on here yet. Please go to my FB I will post one up right now. Sorry.

A link to your fb account would help.

buddyguy wrote:

buddyguy wrote:

jonlink wrote:Pics or it didn't happen?

Seriously, though, I'd like to see how it looks and get more info about what you've done and how it handles if you have the time.

I haven't posted pics on here before so I'll give it a try. If you go to my FB account and like my page I'll go and upload a bunch of clearer pics. I only have on pic right now. FB account: https://www.facebook.com/DimeloMotorWorks

Shoot I don't know how to post pics on here yet. Please go to my FB I will post one up right now. Sorry.

Hope you don't mind, but I've taken it from your FB page and uploaded it here. If you'd rather me not do that, just let me know and I'll take it down. It looks great, too. What did you have to do to make this fit?

ps. to upload photos you just use the "add an attachment" option (located just below the text box when you post a reply).

Thanks, jonlink.

That looks pretty neat!

jonlink wrote:

buddyguy wrote:

buddyguy wrote:

I haven't posted pics on here before so I'll give it a try. If you go to my FB account and like my page I'll go and upload a bunch of clearer pics. I only have on pic right now. FB account: https://www.facebook.com/DimeloMotorWorks

Shoot I don't know how to post pics on here yet. Please go to my FB I will post one up right now. Sorry.

Hope you don't mind, but I've taken it from your FB page and uploaded it here. If you'd rather me not do that, just let me know and I'll take it down. It looks great, too. What did you have to do to make this fit?

ps. to upload photos you just use the "add an attachment" option (located just below the text box when you post a reply).

No I don't mind at all. Thanks for posting it. For some reason it didn't post for me.
It took a lot of trail an error on machining everywhere the tire rubbed. I think I may have it down to a science now, but this 1st time I wanted to do it in stages till it stopped rubbing, so it took a couple of days to figure out. The ride is unbelievable! I'm going to do a few finishing touches then work on the front as well. Unless some one buys her before I'm done. She is up for sale.

Where does it rub? I'm guessing the fender and the engine rubber cover are two places. I'd love to try this out on mine.

jonlink wrote:Where does it rub? I'm guessing the fender and the engine rubber cover are two places. I'd love to try this out on mine.

Yup both. I wish I had the time to document everything. I may put on my FB page in the future.

buddyguy wrote:I just installed a 120/90/10 on the rear, and it took quite a lot of R&D to get it in there, and stop it from rubbing. Now its in there and it's working great. No flat or cupped look on the tire either. I was hoping for a higher gear ratio thats I went with the 90 and it worked! I lost about 5mph on the top end but I'm complete ok with it because of the gain in handling. I'm sure I can make that back with some added HP or Trans Tuning. I've been on this project for about 2 days and I had some doubts. Soon I'll explore with the front as well.

buddyguy, if I interpret the tire codes correctly, the 120/90-10 (dia=18.5") is larger than the stock 100/90-10 (dia=17.1"). So shouldn't you see a higher top end, not slower? Assuming the wheel is rotating the same rpms, such as at WOT. I can see losing a bit of acceleration, but gaining top end.

Or is that much larger of a tire too taxing on the engine?

Also, how much clearance is there between the tire and the back of the engine?

eDan wrote:

buddyguy wrote:I just installed a 120/90/10 on the rear, and it took quite a lot of R&D to get it in there, and stop it from rubbing. Now its in there and it's working great. No flat or cupped look on the tire either. I was hoping for a higher gear ratio thats I went with the 90 and it worked! I lost about 5mph on the top end but I'm complete ok with it because of the gain in handling. I'm sure I can make that back with some added HP or Trans Tuning. I've been on this project for about 2 days and I had some doubts. Soon I'll explore with the front as well.

buddyguy, if I interpret the tire codes correctly, the 120/90-10 (dia=18.5") is larger than the stock 100/90-10 (dia=17.1"). So shouldn't you see a higher top end, not slower? Assuming the wheel is rotating the same rpms, such as at WOT. I can see losing a bit of acceleration, but gaining top end.


Or is that much larger of a tire too taxing on the engine?

Also, how much clearance is there between the tire and the back of the engine?

I'm still working on the clearance of the tire, It doesn't rub, but It's a little to close for my comfort. I haven't actually measured the clearance though. There could be quite a few factor for loosing top end speed. Centrifugal force mass, clutches slipping, more friction from larger contact patch, or a combination of all of these.. etc. Most of the time when we make major modifications to these small engines tuning will be required to unlock its true potential. You are not incorrect in your statement, the bigger tire will have a higher gear ratio so technically it will be faster at the same rpm as before, but all the other factors need to be considered to achieve the same are rpm.

Well you can always MAKE them fit.. like this Honda Metro.

That Metro looks almost amazing. If it looked a bit more comfortable being the size it is, I'd love it. I'm really interested in experimenting with a larger back tire. I think it might make a Boston winter more doable.

I would love to see a stretched Buddy.

z20k wrote:Well you can always MAKE them fit.. like this Honda Metro.

That's actually a Zuma engine. Not exactly a Metro anymore. I'd like to keep the Buddy looking as close to stock as possible so it could kinda have a sleeper look.

buddyguy wrote:

z20k wrote:Well you can always MAKE them fit.. like this Honda Metro.

That's actually a Zuma engine. Not exactly a Metro anymore. I'd like to keep the Buddy looking as close to stock as possible so it could kinda have a sleeper look.

So I took the Fatty, on a long interstate ride today and hit right in the middle of 75 on the speedo. Took her forever to get there so that doesn't really count in my book. I gotta start thinking power and tranny tuning soon!

That's not bad at all though. Please keep us posted!

I'd like to be able to fit taller tires for high speed stability and to correct the speedometer! Anyone modded for taller tires?

130/70-10 Rear Tire - NO Mods Needed - Higher MAX Speed

MYSCTR wrote:130/70-10 Rear Tire - NO Mods Needed - Higher MAX Speed

Nice! that is a lot of tire! What is your top speed with your scooter stock and on these tires?

Well - I dunno - my scoot is not stock yet everything we did affected the bottom end and gave me nothing extra on the top so when we installed this tire we came pretty close to 80 bmph on the highway. There was about a 7-8 mph gain when we put the 130/70-10 on. They are definitely taller and I like that a lot.

My wife rides the Italia has a 110/80-10 on the rear yet she rides like a girl so can’t say except anytime we ride together she can match my top speed. Hers is stock and she is about 70 pounds lighter than I am.

We both have the 100/90-10 on the front.

Hey, what does the taller tire mean for the rear shock?

MYSCTR wrote:Well - I dunno - my scoot is not stock yet everything we did affected the bottom end and gave me nothing extra on the top so when we installed this tire we came pretty close to 80 bmph on the highway. There was about a 7-8 mph gain when we put the 130/70-10 on. They are definitely taller and I like that a lot.

by 4.2mm over the 3.5 -10 and only 2mm over 100/90 -10's.

That isn't very much change in height or gain. that is 6.6mm in rolling distance per revolution at most.

SYMbionic Duo wrote:

MYSCTR wrote:Well - I dunno - my scoot is not stock yet everything we did affected the bottom end and gave me nothing extra on the top so when we installed this tire we came pretty close to 80 bmph on the highway. There was about a 7-8 mph gain when we put the 130/70-10 on. They are definitely taller and I like that a lot.

by 4.2mm over the 3.5 -10 and only 2mm over 100/90 -10's.

That isn't very much change in height or gain. that is 6.6mm in rolling distance per revolution at most.

How do you calculate the diameter?

MYSCTR wrote:Well - I dunno - my scoot is not stock yet everything we did affected the bottom end and gave me nothing extra on the top so when we installed this tire we came pretty close to 80 bmph on the highway. There was about a 7-8 mph gain when we put the 130/70-10 on. They are definitely taller and I like that a lot.

My wife rides the Italia has a 110/80-10 on the rear yet she rides like a girl so can’t say except anytime we ride together she can match my top speed. Hers is stock and she is about 70 pounds lighter than I am.

We both have the 100/90-10 on the front.

What mods do you have on your scoot? I've gotten mine to about 77 bmph on a good day with my mods and the 120/90. I really like the feel of it but I lost a lot of low end due to the size and the bigger carb. I plan to get it all back when I tune my tranny or install a big bore if I have to.

Tocsik wrote:Hey, what does the taller tire mean for the rear shock?

I don't think it does much to the shock, however the because of the added grip of the wider tire, you can l lean in a little more and I higher speeds. Not to mention the slightly higher ride height give a bit more clearance in the corners.

before I installed my fatty tire, my bike was a bit squirmish around the turns, and I would have to really slow down just to feel safe. Now I can fly thru the same turns doing 60bmph and feel completely confident. It make a world of difference. I don't know why they didn't do this in manufacturing.

SYMbionic Duo wrote:

MYSCTR wrote:Well - I dunno - my scoot is not stock yet everything we did affected the bottom end and gave me nothing extra on the top so when we installed this tire we came pretty close to 80 bmph on the highway. There was about a 7-8 mph gain when we put the 130/70-10 on. They are definitely taller and I like that a lot.

by 4.2mm over the 3.5 -10 and only 2mm over 100/90 -10's.

That isn't very much change in height or gain. that is 6.6mm in rolling distance per revolution at most.

according to some online calculator I change my rear wheel diameter by 35.9918mm Does that sound right? Going from 100/90 to 120/90? I measured in diameter not circumference.

Yes. 120/90 is a larger change than 130/70.

120mm * 90% = 108mm

130mm * 70% = 91mm

100mm * 90% = 90mm

You have a difference of 18mm per sidewall or 36mm total.

SYMbionic Duo wrote:Yes. 120/90 is a larger change than 130/70.

120mm * 90% = 108mm

130mm * 70% = 91mm

100mm * 90% = 90mm

You have a difference of 18mm per sidewall or 36mm total.

You are missing the biggest jump in height with this equation - the width of the 130 squeezed into the stock rim. This pushed the tire taller - and yes rolls into corners like way sweeeeet! We have the adjustable rear shock and already had the height pushed up some so with this we have a big difference in clearance. Got on my wife"s Italia (stock) and hit both sides first day in the turns.

I thought about the tire bulge, but i have no way of measuring that.

Yep - we didn't calculate that when getting the tires - Pro: more height (so faster top end) and takes corners so much better with the rounded tire Con: no bigger (maybe smaller) tire patch on road - our intent with the wider tire was to spread the weight or wear over a larger tire patch to get more miles out of the tire.

I see the Continental Zippy's and Michelin S1's come in both 130/70 and 110/80. Might have to give this a try next time. The larger tire would probably help with center stand and Prima header scraping, too.

Tocsik wrote:I see the Continental Zippy's and Michelin S1's come in both 130/70 and 110/80. Might have to give this a try next time. The larger tire would probably help with center stand and Prima header scraping, too.

I have the prima pipe and have put mine thru it's paces. Haven't grounded the pipes yet!

Now, is that b/c of the 120/90/10 tire or are you a featherweight?
Or both?
Maybe I compress the rear shock more; recently weighed at 173.

Tocsik wrote:Now, is that b/c of the 120/90/10 tire or are you a featherweight?
Or both?
Maybe I compress the rear shock more; recently weighed at 173.

It's a little bit of both, I try to keep as lean as possible. It's the cheapest high performance upgrade.

MYSCTR wrote:Yep - we didn't calculate that when getting the tires - Pro: more height (so faster top end) and takes corners so much better with the rounded tire Con: no bigger (maybe smaller) tire patch on road - our intent with the wider tire was to spread the weight or wear over a larger tire patch to get more miles out of the tire.

Are you sure the tire patch is smaller? It looks bigger to me. I only ask because this would be the main reason i do it...

jonlink wrote:

MYSCTR wrote:Yep - we didn't calculate that when getting the tires - Pro: more height (so faster top end) and takes corners so much better with the rounded tire Con: no bigger (maybe smaller) tire patch on road - our intent with the wider tire was to spread the weight or wear over a larger tire patch to get more miles out of the tire.

Are you sure the tire patch is smaller? It looks bigger to me. I only ask because this would be the main reason i do it...

Larger or actually a wider tire patch is exactly why we did it. The idea was to get more mileage out of my rear tire.

We have come to the conclusion there are several factors that wear out a rear tire quicker including;

More weight on the rear of the scoot
Riding style – more aggressive like wot on most takeoffs
Engine big bore and other mods which have created a lot more torque

Maybe with the weight it would flatten enough to get the wider patch yet as high as we sit I am not sure. I do know I can lean a lot more in turns without scraping so we know we have height.

Anyone know of the tallest front tire that can be used... to correct the annoyingly inaccurate speedometer?

Threads I've addressed this in for reference...
spedometer inaccuracy...can it be fixed???
Buddy digital speedo? Way to make stock one more accurate?
How inaccurate is your Buddy Speedometer & Odometer

I want to put slightly taller tires on my buddy 125. my bike came with 3.5-10 tires. from my vast experience with car tires you cant trust tire size numbers form different manufactures. tires sizes vary ALOT. with that being said the numbers will be helpful within the same tire brand.

size---------height----width
3.5-10
90/90-10...16.38 .....3.54
110/80......16.93.......4.33
100/90.......17.03.......3.94
130/70.......17.17....... 5.12
120/90.......18.50....... 4.72

I am not so much caring about correcting speedo or increasing top speed. to me this scoot is fun to 45mph. I am just looking for better stability and handling.

I think i will go with 110/80 front and 130/70 rear. should be noticeable difference.

Read the above posts - the 130/70 will squeeze onto the factory rim, yet doing so will cause more height or "bulge' which will give you more height (and ground clearance) for the scoot, better in turns if you like to lay over, higher top end yet we didn't find any downside putting this on our rear wheel. Been off the scoot for awhile so do not have any data on how many miles it will last compared to the stock size.

did the 110/80 on rear increase diameter as well? or only 130/70?

shame they dont make a 120/80 or 110/90. seems like big gap in tire sizes having to jump to 120/90 which is huge jump in diameter.

How do you calculate the diameter?

First you measure the circumference of the tire with a cloth tape measure.
Circumference = 2πr (where π = 3.14 and r is the radius)
Rearrange the formula to solve for r. This gives r = circumference /2π
The diameter is simply 2 times the radius (r).

Tire size does not affect contact patch size, only shape. The weight on the tire and the tire's pressure determine the actual contact patch area. That having been said, contact patch shape is an important factor in handling characteristics, as others have noted.

I installed a 120/90 10 on a 5" wide rim on a Buddy 125 motor, but it's going into a Ruckus. The tire fits, but I had to do a bit of modding on the case to make it work...

is that the sams club rim? it looks monster. should be real nice for the ruck.