Modern Vespa

Hey all! I got my 500 back from the dealer and its running like new after the fuel pump exploded on me after a big bump in the road! Anyway, my stock tires only have 700 miles on them but I'd like to change them out for bigger/better tires so I can get a better ride and also corner better. it seems as if the Diablo's are the best for the rear but what about the fronts? Can I have a diablo on the rear and a different tire on the fronts? If so, what would you guys recommend. Also, I really want to order the 160 for the rear but I'm super nervous about hitting the shocks...you huys that have been running them on the 500, how are they working? Any problems/rubbing at all? I'm ordering tires tomorrow. Thanks everyone! I love this forum!!

Many have installed the 150/70-14 and a few the 160/60-14 rear tires in multiple brands. They are close to the shocks but installed properly do not touch.

For me on my 400 the ride improvement isn't enough to throw away a good tire with only 700 miles on it.

Don't worry about the fronts being different. The tires perform a different function and even in the same line of tires are made different for front and rear and the position is specified on the tire. The Diablo fronts are not yet available in the U.S.

Yes and no.

All I can report on is using a 150/70 instead of a 140/70, MGS.

The ride is superb - no more conscious counter-steering, the bike just flops over when you just think about it. The lean angle acheivable is greater, no more centre-stand scrapes - but if you do scrape something it'll be the exhaust shield or the transmission case.

However - acceleration is definitely slower from the off - but (with the J Costa) still very smooth and controllable. Top speed seems to be down, strangely - at least that was what I thought until I had a downhill 'private road' and got it over 7,000 rpm, then it was like another gear had been added for the flatter miles thereafter.

Then there's the problem of the extra forward slope given to the seat. Not good for taller (6' 0" here) person.

As this is not my main bike for touring, I'd use a 150/70 again. If it was my main bike for touring, I'd revert to the 140/70, for the comfort and the performance when playing with other traffic (overtakes).

I don't know that I would change tires until the existing one needs replacing, but that is your decision to make. However, I'm not sure a 160/60 will fit on a mp3/500. I posted some pictures of a 150/70 on my scoot at

https://modernvespa.com/forum/topic53312

A 160 would be wider. I think all the 160's I have read about are on MP3/400 scoots, though I may be wrong.

The larger tire does give a better ride, though.

if you search this forum you will discover that there are enough people with th 160 tire and no problems.

wait till your ready for a new tire. Go ahead and order one and have it sitting there for when yoou need it.
As far as the ride difference, I can report on the pirelli diablo 150/70. I really like how it gives greater ground clearance, the grip in the dry is very good. I have not been in the rain yet with it. JimC is correct it does give that little forward lean , but I personally like it,

I seem to be alone in my opinion, but after maybe 1500 miles currently on the 150 tire, I am going back to the 140 size. The quicker cornering also ( to me) affected the general ride, making it a bit quirky. I think the engineers knew what they were doing when they chose the 140 size tire.

I've been on the 160/40 for about 500 miles. No shock scraping issues at all and I'm close to 200 lbs. I think the 160 is slightly lower than the 140, and I routinely scrape the stand on turns. And with all the dragging going on, I still have 1/4" chicken strips on both edges. Unlike Jim's report on the 150, I find the 160 does not like to lean all that well. The only positive thing to report about the 160, in my opinion, is it looks mean. When my 160 is done, if not before, I'm going to switch to a 150.

I weigh 230lbs and run the 160 Diablo rear tire. It does well in my particular application that includes carving some nifty country roads enroute to offroad / sand path adventures. The fatter rear tire is a big advantage in the sand and in my estimation does not hinder performance on the asphalt. I'm not going back to a skinnier tire. The 160 has never touched my shocks, but it remains very close to them, maybe 1/8 inch away.

I ordered a 160/60 Pirelli Diablo today for my Saturday 6k service and tire install. I really am excited after hearing sushiman007's glowing reviews on his 500. I wanted the wide tire look, and (being vertically challenged) didn't want the tail of my 500 any higher than stock, which was even more of a reason why I chose to run with the 160/60 vs. 150/70.

I will post my thought after the tire and I get better acquainted Saturday.

By the way, I got 7500+ miles out of my stock Dunlop rear 140/70. I really enjoyed that tire, and if I had to go back to a 140/70 I would most certainly look for the Dunlop!

I had the 140/70/14 Michellin GS replaced by the Bridgestone Hoop2 150/70/14 tire and I couldn't have done better.
The bike became more secure and with more top speed (160km/h to 170km/h) because the tire is slightly bigger.
I didn't notice any loss of power when accelerating and I also believe that the lean angle is greater
I recomend it

I have a 150/70 and am happy with it but I'd not dump the stock tire after 700 miles for it. There are too many other things that would come first for a "better ride."

Do you have a J Costa? That will make a difference in the ride. Do you go on long trips? A Throttlemeister will make a difference in the ride. Are you trying to turn the MP3 into a sport bike? Maybe another clutch but that leads to a big kettle of fish. Some things are worthwhile, some are not.

Jim and OAD, I have a question about your comments regarding the rear tire changing the angle of the rider. I'm nowhere near changing my tire yet, just curious.

If I understand it, a 140/70R14 is 14" in inside diameter, or 7" in inside radius. It is 140mm or 5.5" wide. The tire extends for 5.5*.7 or 3.85" past the rim. That means the total height of the axle above the ground is 7" plus an additional 3.85" = 10.85". Am I right so far?

If so, then a 150/70R14 is 7" in inside radius, 150mm or 5.9" wide, and an additional 5.9*.7 or 4.1" larger than the rim. The total height of the axle above the ground is 7" plus an additional 4.1" = 11.1".

If so, then (at least sitting straight up and not accounting for contact patch compression), the rear of a trike mounting a 150/70R14 is only 0.25" higher. I thought maybe the difference becomes apparent in a turn, but the drawing below indicates that in a 40 degree bank, the difference in height between the axles of the two tires actually decreases slightly to 0.24".

Does that 1/4" really make a noticeable difference, or am I missing something in my calculations?

rjeffb, you're not missing anything at all. Your just not feeling it!

You are missing the fact that the 150mm wide tyre is being compressed into a 140mm rim - this squashes the tyre in and increases the curvature of the tread. The total diameter of the tyre increases - by over 6cm.

>You are missing the fact that the 150mm wide tyre is being compressed into a 140mm rim - this squashes the tyre in and increases the curvature of the tread. The total diameter of the tyre increases - by over 6cm.

Aha, of course. My calculations are absolutely correct - if the rim was replaced as well. Of course putting a larger tire on a smaller rim is going to affect overall diameter, that extra rubber has to go somewhere.

Stupid neophyte question: when one installs a larger width tire on the same rim, that has to change the forces acting at the rim-tire boundary. Does doing so affect the bead integrity? (Especially on a tubeless tire, which must not only be mechanically sound but airtight.)

You say it increases diameter 6cm (wow, that really is a lot), so that would be a 3cm radius increase and therefore will lift the rear up by about that much. Thanks!

I wondered about the wisdom of putting an over-size tyre on, so asked a few trusted mechanics. They all said the same thing - one size up or down is perfectly OK, and a common thing to do.

On manufacturers' tire specifications they give recommended rim width and acceptable rim width. OEM tires are at the recommended rem width but there is a significant range in the tire specs around the width.

Continental's web page has a pdf download over 100 pages with a lot of information on their motorcycle tires much of which applies to all motorcycle tires.