MGB: Spoiler / Air Dam performance

There has been a number of posts recently on air dams/spoiler. Moss offer 3 differnt varieties of these:

Urethane Air Dam @ $219.95
Special Tuning Spoiler @ $89.95
Limited Editon Spoiler @169.95

Does anyone know the relative effectiveness among these on the handling of the car? Are some just pretty or do they all do the job.

Cross posted to the motorsport forum.

I tryed the ST replica one on the V8. It makes a difference at more than 110 MpH but it is a very thin laminated piece that tends to brake immediately when you have contact to the pavement corners.
I recendly changed to the Frontline Developments (Frontline Costello) one. It was 89 GBP plus shipping but looks much more original than all the Moss versions and is a very solid GRP molding.
It looks like the Sebring front vallance with a spoiler integated at the lower edge and works great.

No further experience with spoilers on the B here.

I've got the ST spoiler on the V8. I notice the car's more stable at speed. Being fibreglass, it is a bit fragile but it can be reinforced with extra layers is so desired.

No experience with the others.

Ditto on the ST. Makes a huge improvement at highway speeds. Looks great painted body color with rubber bumpers!

Yes it is thin, but is more than strong enough. You can reinforce it til you are blue in the face, it will just relocate the area it will break. How many factory bent STEEL valances do you see.. lots.. The trick is to buy 2, have one on the side, so when it DOES get damaged, you can just swap it out and fix the broken one :)

I have the urethane one. I didn't really notice much of a functional difference.

Theoretically speaking, most of the drag that a car develops occurs in the undercarriage region. Turbulent air under the car has no where to go. If you use an air dam, you should expect better fuel economy and a higher top speed (if your gearing allows). That crappy little lip on modern cars right under the bumper, that usually falls off after the first parking curb hit, is responsible for about 2 mpg highway fuel economy on some family sedan type cars.

I've got the fiberglass ST spoiler on the '73. After cracking it against a parking-spot curb (not before, duh!) I reinforced the snot out of the back side, sanded it out and repainted it. It did make a difference in highway speed handling. I always felt the front end wanted to get away, before. Not so much, after.

Besides, I like the look. Even with chrome bumpers, painted body color they're a nice setup. (Not my car, but close enough for the purpose....)

I have the LE air dam. Looks good, but I don't know if it really does anything.

One thing I noticed.. My bushings are shot in the front end and at high speed the car tends to shake a bit. After installing the LE air dam, the shaking was reduced and I had to go faster for it to occur... so maybe it helps stabilizing the front end some at higher speeds.

I have the urethane piece. I've hit speed bumps and curbs and if just bounces right back. I mounted it on top of the valence panel not in place of it (less work on a hot day).

I feel it adds to stability on the freeway. It used to sort of "hunt" at 80+ and worse as one went faster. Not it seems not to, though I've not taken it to the "California Speedway" (Interstate 5) for testing. The unfinished piece also seems to "look right" on my somewhat scruffy car

as far as i am concerned, at the speeds an mg is normaly used at they are only for show, doesnt stop me owning one! lol

Matthew,

What speeds are you running? The interstate highways in Colorado are running at leat 75 MPH. A bit faster on the lonely parts. Most of the secondaries are 65.. Pikes Peak Hightway is 15 though, any faster than that near the top and you could test the aerodynamic lift component of the car.

The spoiler on my 75 killed the front end float that you could start to feel around 70 and got worse the faster you went. Its down right planted at 5500 in 4th and to think I was going just fast enough to keep from getting run over by the other traffic. You have to love driving in socal.

[quote="Ralph 7h"]... the Frontline Developments (Frontline Costello) one..[/quote]

I agree the ST does help with front end float somewhat.
A side benefit I found is that it helps with cooling when moving.

I like the looks of the Costello spoiler. Shipping it to the US must be PRICEY.

A different approach, but very effective at speed.

I have the ST and think it makes a difference with regard to front end lift. Seems more stable at any speed above 55. Can't say much on cooling since it has cooled off this fall, but I think it does help. I get great milage as well, checked it Friday after about 260 miles on a tank and got 33 mpg.

IMHO if there are any real dynamics I doubt they'd kick in until speeds over 150MPH...same with a rear wing. This is mostly functional track stuff adoped to street "he man" looks as in all the Rice Burners with Euro treatment....Those guys REALLY throw good money after a hum drum car purchase....

If you do not believe that aero effects happen at lower speeds... then you've never driven with the top down or done something as simple as sticking your hand out the window in the shape of an aerofoil at freeway speed. While aero effects increase at the inverse square of speed, they start happening as soon as air starts flowing over or around an object. It's obvious that some have never experienced the actual change of an airdam on vehicle dynamics on a first person basis. Try a back-to-back comparison at something as slow as interstate highway speed... and you'll understand the difference.

[quote=Steve64B]
If you do not believe that aero effects happen at lower speeds... then you've never driven with the top down or done something as simple as sticking your hand out the window in the shape of an aerofoil at freeway speed. While aero effects increase at the inverse square of speed, they start happening as soon as air starts flowing over or around an object. It's obvious that some have never experienced the actual change of an airdam on vehicle dynamics on a first person basis. Try a back-to-back comparison at something as slow as interstate highway speed... and you'll understand the difference.[/quote]

+1

:drinking:

Questions about the Costello air dam. Is it made of fiberglass and is it substituted for the valence as well?
Frank

@ Frank,
yes, it is made of fibreglas but very solid and it substitudes the mormal front valance.
Compared to the Moss ST front spoiler it seems to have 3 to 4 times thicker materieal and mine was finished very well,
although the gelcoat finish needed sanding at some spots.

@Robert,
on the GTV8 the difference in handling was dramatic at speeds in access of 110 MpH.
With the stock valance the GT became extremely uncomfortable at 125 MpH and was hard to keep under controll at 135 MpH. With the spoiler valance it feels much safer at this speeds, so it does not need to be 150+MpH before there are real benefits.

Ralph

The product description for the ST says can be modified to fit later models... anyone know how much modification is involved? I have a '77.

Kevin

All you have to do is make a cut out for the Rubber Bumper attachment point. It ends up being a notch covered up by the bumper when you re-install. Not difficult.

Kevin,

As Jon says, it's relatively easy to cut out the material. I added an ST spoiler to my (originally a RB) car but added CB's. The principle is the same except you need bigger notches.

In this photo, you can see where the old RB mounts were cut back but if you imagine them still in place, you can get an idea of where they'd meet up with the spoiler. The small notches you can see are for the CB mounting brackets I used.

Hope this helps.

not too much modification to fit a 79 rubber bumper..

about 1/4-1/2 inch taken off the top edge. cut outs to clear the brace fittings[outboard] from the bumper to the longitudinal thrust member
1/4-1/8 inch off the outside ends/edge to match contour..
its a Fit up, dismount , cut and fit operation..
i never did get it to fit flush on the center fixing positions , stands forward of the mounting surface .. a little , perhaps that is because i started fitting out board [both sides ] instead of center, but then had i fitted center first i expect more would have been trimmed from the outboard. i fitted up with bumper installed, would have been easier bumper dismounted , now i have bumper dismounted , perhaps i will try to make those center fixing points ,,,

perhaps today i will take a pic of the cutouts to clear the outboard braces

I like the Costello valance as well, simular to the Sebring piece but with a chin spolier included. I wonder if it mounts flush with the fenders and front of the car or sits inboard like the other airdams, this is important when doing a bumpless look.

I got some feedback on shipping for a Costello spoiler to the US. The cost of the spoiler plus shipping appear to be something in excess of $500 total. I would be less if mutiple pieces were shipped.

I think I am going with the ST part and add siffening to it. I have access to boat buliding supplies that offer a multitude of alternatives.

Hap,

the Frontlne/Costello spoiler can be fitted the same way as the Sebring replica one. There are some pics shown on this page: http://www.upgrades4mgs.co.uk

Ralph

Try calcuating that shipping cost via post office service. I ship all over the world and if you don't mind waiting a few weeks you can get things shipped to or from other countries rather reasonably. Not cheap but livable.

Costello claims they only ship UPS internationally.