Aero-AntiCorrosion Mod to Trim Rings..

Hi All,

Who says the Trim Rings on the 15 Inch wheels are useless? Here is a mod to cover up the disk brakes from melting snow and rain when parked. They also should help aerodynamics, but I have not tested them for that. This mod may not be too durable, but so far so good.



This were made using .009" thick 20 inch wide Aluminum flashing. It was $16 at Ace Hardware. There is enough in one coil for about 6 wheels.

Fabrication consisted of scribing two circles (8 1/8 " and 8 3/8" radii) onto the flashing using a tramel point compas made from Dry Wall circle cutter points, and 1/4 inch square steel rod. The larger circle was used as a guide to cut the flashing out of the stock. After washing the trim ring, it was positioned onto the flashing circle. The trim ring has two notches. The first two 1/2 inch wide tabs were formed by cutting slits into from the flashing circle OD to the inner scribed circle. The first tab was folded up into the first notch. Then the ring carefully alligned to the inner scribed circle before cutting the second tab and folding it up into the second notch. Then 1/2 inch tabs 90 degrees to the first two notches were cut and folded using the scribed circle to keep the trim ring concentric with the flashing circle. At each section of the trim ring more 1/2 inch tabs were cut, bent and folded down. Then 1/2 inch tabs were made halfway between each of those. Eventually, you get to a situation where there is space for about two 1/2 inch tabs between the existing tabs. I cut a V slit halfway between the two tabs at this point, and cut away a V on the outer edges next to the existing tabs. This allowed these two new tabs to fold over flat onto the trim ring, without overlaping the existing fold tabs.

A machinists' hammer was was used to form the tabs onto the trim ring. After manual bending of the tab up, the hard plastic face of the hammer was used to form the tab tight to the circumference of the trim ring, then the rubber face of the hammer used to fold the tab down. The rubber face allows the tab to blend into the variations in the surface of the backside of the trim ring.

After forming the flashing to the trim ring, a hole for the air fittings was made with a drill press, and a forstner bit. Forstner bits work reasonably on aluminum. I used a piece of wood under the flashing so the bit could develop enough pressure to cut the aluminum. This is a little tricky, so be careful if you are not familiar with drill presses.

Next, I used a Demel style tool, with a serated 3/8 inch diamter ball cutter to put weep holes into the trim ring. These were cut from the back of the ring into the 6 depressed areas of the ring. The ring is apparently made from polystyrene, based on the styrene monomer smell when making these weep holes.


The flashing is thin enough that the V shaped spring loaded features of the trim ring still snap solidly into the internal groove of the wheel.

First impressions is that the car seems to be quieter at speed, but that is only anectodotal. Two reasons I wanted to do this was to reduce the rust spotting on the brakes while parked with various kinda of precipation occuring. And second, some road construction has concluded for the winter, resulting in my commute having higher speeds for about 1/3 of the distance. And its winter, and the air is more dense. The impact of cold air on aerodynamics is readily experienced watching planes land at O'hare. Below 10 F, one can hear the planes ripping through the air (it actually sounds pretty neet) over the noise of the engines.

 

Hi again,

More comments. I did not like the racing hub caps, because they are bowed out. This is done to accomodate a wider variety of cars. If you look a the Prius 15" wheel, its concave in, so it does not need this bowing. So a flat hub cap spans over the concave portion without touching any part of the wheel but the outer edge. The flat cap should be better aerodynamically.

 

Hi Best...,

I cut the flashing with tin snips. I have both straight, right cut and left cut tin snips. Its quite easy to make the cut if one is a little near sighted, take the glasses off, have good lighting with a curve cut tin-snip. And of course, the trim-ring forms the final perfect circle.

It took about an hour to do one of these. The material was an extra 10 minute stop on the way home from grocery shopping.

 

Hi All,

Here is an updated picture. The hole for the valve stem had to be made oblong to accomadate the angle of the valve. With the extender screwed onto the valve, the extender tip was missing the hole.

 

Hi Clubford,

Take your self a long trip, and bring your Prius home. Then reach into the hole in the wheel and feel the heat with a knuckle. Do not try this on a regular car!

I have done this and gone all the way to touching the disks. They were about 100 F or so. The Prius does not use its friction brakes until 7 mph in normal braking. It uses them only when the battery gets full (long downhills) and panic stops. We do not have long downhills here in Chicagoland. I will be sure to take them off at a rest stop in Nebraska before I proceed into the front range. But around here the disks are getting pitted from non-use.

Most of the braking energy of a Prius goes into the MG2 motor, and onto the batteries. In a regular car where all the slowing energy goes into those disks they run at 300 F or so in metropolitan area driving. My knuckle tells me not to get any closer to 1/2 an inch on those.

 

Hi Holy...,

Hard to say. Daily driving here has been so variable. I was at 57.5 mpg at the end of the day on Thursday last week, but then had to drive in 1 inch slush on the road on Friday in a short trip at 35 F, and more short trips over the weekend. By Friday this week I was down to 53.8 mpg.

Weather is just too variable here to say wether they are helping or not. It was 60 F deg last thursday, and today we are waking up to 20 F, and as I mentioned above the day after 60F was a slush storm at 35 F. Low traffic levels somedays, and heavier traffic with snow the other days just makes it unpredictable.

They are not getting all banged up though, like some of my ME work colleagues preditcted. They look pretty much the same as the day I put them on.

A true test will be some kinda down hill coasting test, and see what the final speed is at the bottom of the hill with them on or off. But or course its not good to coast in the Prius tranny above 40 mph, and 60 is the absolute max with engine off. Which is really not fast enough to get a see the difference for such a small aero mod. 75 mph should show the difference more readily. We do not have any hill long enough here to coast up to 75 mph in this area.

Cruising at 75 would not work, unless you had two Prius driving the same road at the same time both in cruise control for the same period, one with the hubcaps, and one without, and with no other traffic on the road. That is a hard situation to setup here in Chicagoland.

I will be setting up a MyScanPC (already have the EEE PC) to get some data acquistion. Possibly then I will be able to quantify a change.

I did get a compliment on them the other day. The guy said it made the car look very futuristic when driving down the road. I occasionally see people in the passenger seat do a double take looking at the wheels.

 

Hi All,

I have moved my front driver license to a mid lower grill position as well now. I used J-hooks from Ace Hardware and stainless steel nuts and washers in front and behind the the plate to adjust the fit and clamp the plate . I originally was going to use 4 J hooks, but two on the top two holes of the plate worked just fine. The J hooks are slightly pulling upward , and the plate is keyed into the recess for the grill. I used a piece of plastic tubing slit lengthwise to make a chafe gard on the plastic bumper protector. Its a very secure fit.

The idea behind this is a that the bumper protector is now a smooth blunt body aero surface, rather than having the plate protruding on its braket.

This makes a permanent 1/3 lower grill grill block, which may not be appropriate from hotter climates and mountain climb application, however.

 

Hi All,

Several months ago I found a problem with using the stock Prius (I think they were?) valve caps with the metal extenders.

Do not use the stock Prius valve caps on those metal extenders as shown in that picture. Only use the metal caps sold seperatly by the same valve equipment manufacturer. The Prius plastic valve caps have a small ring down in the cap which can cause a slow leak due to the design of the metal valve extenders. The ring alignes the cap into the normal ruber valve stem, so the O-ring in the cap seats properly. The metal extenders have a dust cover which the ring will push down on, and cause an open air path through the extender. The cap limits the leakage, but if it were to be hit by something and cracked, you could see your tire deflate rapidly while at speed.

 

Bump...

Important comment: DO NOT use metal valve extenders. They are not corrosion compatible with the metal the TPMS valves are made from. Use the plastic ones.

Another comment: The plastic valve extender springs are not corrosion resistant. These extenders will weep orange corroision after a while. Solution - get some vinyl caps (like used to protect SMA or other similar sized unmated threaded jack connectors) and put those on the plastic extenders. Why these do not come with the plastic extenders standard is beyond me.

 

Hi All,

As some of you may know, a 2000 Chevy Suburban totalled my 2006 Prius.

And I got a 2010 to replace it.

Here is a picture of the not flush, but application of the same 10 mil Alumimum sheet to the 2010 Prius trim rings:



The two concetric circles scribed onto the metal sheet were 16 7/8" and 16 1/4" diameters. Cut out the OD diameter, and cut slots, with Vee shape from the OD to the inner scored line. Then its just a matter of bending and forming the metal around the outside of the trim ring as previously described.