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Tire Change: Race To The Finish

Thursday, January 3, 2008

Back on the beat here as we count down to the final tire installation, modification and road test. Don’t start until you have all three of these items (seen below); plus,don’t forget to have a 12-inch zip tie, a large metal file and mostly importantly, a torque wrench (with ft/lb settings from zero up to 100 ft/lb) handy.

Must have: thread locker, lithium grease, and a new single-use DAX flange nut (aka: rear axle nut).

 

(Modification No. 1) During the initial fitting with the newly mounted Pirelli Diablo 150/70-13, I discovered that a 1/2-inch corner portion of the lower aluminum exhaust mount (where the exhaust hanger goes) would have to be filed off so that the wide-profiled tire could slide in properly.

Slide the rear brake caliper over the disc rotor first before it's bolted on. This will give you more space to easily slide the brake caliper over the disc rotor.

Put some lithium grease over the rear axle, except at the end--that's where the thread locker will be applied.

Tighten the screws only half-way here. (Just enough for torquing the rear axle nut later.)

This is how the rear brake is applied--using the zip tie. Basically this will lock up the rear wheel, allowing you to torque the rear axle nut.

The proper torque spec is in your owner's manual. Don't over-torque it!

Once the torque is set, hold the left-hand brake lever while carefully cutting off the zip tie. Very slo-o-owly release the lever completely; then very slo-o-owly squeeze the lever again. Repeat the release and squeeze actions for a few times until the brake pressure is restored. Now, basically–You’re Done!

Now, check out the tight squeeze on the air-box side--only a 1/4" gap!

Over to the exhaust hanger side, there's a slightly larger clearance, 1/2-inch. Safe!

The look of a superbike is achieved.

(Modification No. 2) Noticed the missing mud guard? It had to go because it just wouldn't fit.

Project accomplished!*

Road Test Impressions:

  • Ride height is now a few inches taller–naturally due to a larger tire-diameter upgrade.
  • Riding ergonomics is now more forward-leaning yet comfortable.
  • Larger tire is a little harder to accelerate from a standstill.
  • Top speed seems improved (to 51 mph).
  • During cornering, the larger contact patch of the Diablo firmly stablizes the rear end.
  • Smooth ride of a larger, brand-new tire can’t be beat!
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Oops! Spring turned slightly to illustrate the extent of the damage. Noticed the scrape mark on the tire?

*Update:

(1/10/08) Less than 2 weeks after the installation, I remain largely satisfied with the performance and the look of the new tire. However, as I was washing the scooter today, I noticed that the left sidewall of the Diablo had rubbed against the spring of the shock absorber, causing a small patch of the yellow paint to be removed. Hmmm, I have got to find a way to move the shock absorber (slightly) away from the path of rotating tire. I believe that I have upset the Balance when I up-sized the tire; so now I must fix it! Stay tuned

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Problem Solved!

(1/11/08) I contemplated over the last 24 hours and finally arrived at a difficult scheme which would involve adding several stainless washers to the bottom bracket of the shock absorber where it is bolted to the transmission; and by so doing push the entire shock absorber away from the rotating tire by about 1/4-inch–enough to keep the tire from grinding up against the spring. However, as I loosened the bottom bolt, I thought of another far simpler and more elegant solution to the problem at hand–asymmetry! By reversing the (asymmetric) bottom bracket of the shock absorber, the shock absorber naturally swung away from the tire about 1/2-inch. Voilà, problem solved! I quickly tighten the bolt, and made several crayon marks along the area of the tread that was rubbing against the spring previously just to see if they would make further contact during a road test. After 30-min of trial run (riding through the city, over the RR tracks, bumps, potholes and so many twists and turns), I am glad to report that the tire no longer comes in contact with the spring of the shock absorber. Very glad that I was able to catch this problem early (as I was washing the scooter) ; and even happier that a simple, yet elegant solution was available to save the day.

With the bottom bracket of the spring turned 180-degrees; the bolt now has to be tightened from the right-hand side.

There should be plenty of space to keep the moving tire away from the spring.

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Update #2

Recently, I had to change out a burnt-out headlight bulb; so the first thing to do was to disconnect the battery, in this case, the negative wire would do.  As I removed the plastic outer cover of the battery compartment, I was surprised to find a high accumulation of dirt and sand on top of the battery.   I instantly realized that by removing the rear mud guard (as it was necessary for the tire up-sizing), I had exposed the engine area as well as the backside of the battery compartment to mud in wet weather.

After replacing the headlight light bulb, I wiped off the top of the battery and applied some Vaseline to both postive as well as the negative connections to control corrosion.  I happen to be a big tofu-eater, so there’s always a handful of 14~16 oz. plastic tofu containers around; and as it turned out, they make great battery covers.  I carefully trimmed off two corners of a tofu container and it fit perfectly over the battery.  Hopefully, this would prevent water and mud from fouling or messing up the battery.  Finally,  I secured the outer battery cover over the whole thing; and again, the fit was just right.–Lorenzo

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The last known photo of my Aprilia SR before it was sidelined in July,  2008:

Well, do you like the new look?

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4 Comments leave one →
  1. Thursday, September 11, 2008 12:15 pm

    Wow! I enjoyed reading your post – it’s always a joy to do maintenance yourself and to find easy solutions to problems. The one thing I’d want, however, is to see a whole picture of your ride!

    Over here in Taiwan, it’s so cheap to get tires changed – around $8 USD – that it’s probably not worth it to change the tire yourself. Not only that, but all the residences in the city are apartments, which means there’s no private space to do these things.

  2. Thursday, September 11, 2008 12:50 pm

    Hi, Shawn

    See “Members” page for a full picture of my SR!

    Lorenzo

  3. Thursday, August 20, 2009 11:24 pm

    I am building a custom scoot. I would REALLY like a before and after pic of that 150 compared to the 130. I am making a chopper and size matters… I hope you have one of both tires looking from taillight…. Skyetone@msn.com

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