How much does a roof rack actually affect fuel economy?

[JBG3]

Great, spread the MPG reduction with a loved one.  Da heck?

hahaha, not at all.

The rack was originally bought for a 123 MB chassis diesel, and maybe its the shape of that car being wider and not particularly aerodynamic, or the fact that the gutters are much lower with the fairing resulting at a more sloped angle with all the equipment closer to the roof, but it never had much impact on fuel economy, not near as much as the same rack on this VW.  My MB from way back seemed to get about the same, no matter what was on the roof.  She's got the same model car and could use a roof rack, so I figure ill get some use out of this expensive yakima stuff. 

[JBG3]

maybe something like this would be way better-

http://www.a1-autoracks.com/perrycraft-dynsport-roof-rails.html

these guys have tons of products, some side rails with easily removable cross bars might be the best blend of have the ability to put stuff up there, and strip it down for best economy

[VW Smokr]

Seems like my Thule roof rack, naked, or with 2-6 pair of skis mounted up there drops highway mileage by 3-4 mpg, plus the thing makes 'whistling' noises at some speeds. Oddly, when the same rack is holding my monster 'Thule Pod' aero-box (skis inside), the fuel mileage does not suffer at all, and the wind noise is gone! Can only guess that the boys at Thule must have sent their 'Pod' designs over to their Scania aircraft division for wind tunnel testing, mounted on actual car roofs! Whatever... they succeeded; sure works 4 me.

J.R.
SoCal

[JBG3]

maybe something like this would be way better-

http://www.a1-autoracks.com/perrycraft-dynsport-roof-rails.html

these guys have tons of products, some side rails with easily removable cross bars might be the best blend of have the ability to put stuff up there, and strip it down for best economy

so I ended up buying the above rail system, along with some "monte blanc" aerodynamic cross bars.  Waiting for them in the mail.  I got the 45 inch long rails, which are the shortest option, but should just fit on the mk2 roof. 

Ill post back when I get them all installed and see how they look and affect my fuel economy.  Im hoping this will work nicely and allow my to carry my big Thule ski carrier without negative affect to efficiency. 

[scrounger]

If you want to keep your setup aero, put on a trailer receiver and hang your rack at the back when you need it.

I run snow tires on all wheels on my 86 Jetta and keep them at 50psi or higher. Higher pressure really helps the economy.

[JBG3]

If you want to keep your setup aero, put on a trailer receiver and hang your rack at the back when you need it.

I run snow tires on all wheels on my 86 Jetta and keep them at 50psi or higher. Higher pressure really helps the economy.

Might do that as well, however mostly I want a roof rack for my ski carrier, which is pretty aerodynamic when its up there, at least tested on other cars. 

Haven't tried that with the snow tires, but I think I will when I put them on and see what happens.  I have my summer tires at 40 psi right now

[R.O.R-2.0]

just keep in mind.. a SIDE MIRROR is like 6-10% of the total drag your car has..

a roof rack has ALOT MORE surface area than a mirror, so figure in ALOT MORE drag..

-5mpg sounds about right!

[JBG3]

got everything in the mail, here are a few pics-

stock roof (ignore the spiderweb paint problems and the heavily caulked windshield)



with the roof rails-



little further back for an overall view-



They are chunky and rounded, and really don't match the car at all at first, but after a few minutes, it didn't bother me in the least.  The ends certainly follow the contour of the roof perfectly. 

The plan is to get these mounted up permanently, and get a couple tanks of fuel through the car to see what affect they might have, then attach the cross bars and do the same thing. 
Here are the cross bars, they look exactly like a Mk4 factory cross bar

[Blocksmith]

Looking forward to the hard fuel economy numbers from this, seeing as how I am pretty much dead-set on installing a rack on my rabbit when time and funds allow 

[TylerDurden]

Good looking kit.

FWIW, On my Mk2 rigs, I use the old school Thule similar to this pic:


I cut the bars to ~50", so they easily fit into the trunk. I pop them on/off per use: drive to the store, put em on, load 4x8 ply, take em off at home.


P.S. My "Polar Silver"    Jetta has the same paint and windshield, lol.

[JBG3]

Looking forward to the hard fuel economy numbers from this, seeing as how I am pretty much dead-set on installing a rack on my rabbit when time and funds allow  

Waiting on some body repairs first, then I can post up some economy numbers hopefully, probably a week or so though.

 I had pulled the windshied and discovered extensive rust problems, so Im having that repaired right now.  

In the meantime, the convenience of having the windshield out means we can pull the headliner out from the front, and install the rack.  

I do have a couple complaints about this rack though so far.  1, it has no rubber gasket or grommet included, maybe its just missing and they meant to send it, but for something thats designed to bolt to the roof, it has to have some kind of water prevention.  If it actually does not come with one, that seems like a major oversight to me.  

2. the fastners are just sheet metal screws.  That may be pretty common, but i prefer a nice strong bolt and nut, so im gonna actually bolt them on instead through the roof and discard the sheet metal screws.  We are also making rubber feet for the rack.  

[JBG3]

Good looking kit.

FWIW, On my Mk2 rigs, I use the old school Thule similar to this pic:


I cut the bars to ~50", so they easily fit into the trunk. I pop them on/off per use: drive to the store, put em on, load 4x8 ply, take em off at home.


P.S. My "Polar Silver"    Jetta has the same paint and windshield, lol.

I love the Thule and yakima gutter racks, I just wish the mk2s had something more substantial to attach them to than the rubber trim over a pinchweld.  Even with my yakima rack cranked down, it was still movable, and was in danger of cutting the rubber. 

It just made me nervous (especially since I had ripped off some trim with another forum member on a parts car and saw how the trim itself was attached with just clips, which had a tendency to break easily as we removed it).  It just seemed to me that it was never a permanent roof solution, that I was always clamping something to what was effectively a trim piece, which always affected how I would use the rack. 

this change will be for peace of mind in my eyes.   

[R.O.R-2.0]

Looking forward to the hard fuel economy numbers from this, seeing as how I am pretty much dead-set on installing a rack on my rabbit when time and funds allow 

its gonna drop your economy..

its not like a light canopy on a caddy, where you see mileage INCREASE..

the light canopy makes them MORE aerodynamic most of the time..

a set of BARS coming off the roof does not..

expect a 3-5mpg loss..

[R.O.R-2.0]

its not the roof bars that are gonna kill the economy, but the cross bars that add all the drag..

[Blocksmith]

Easy solution to the problem--only put the cross bars on when you need 'em, store 'em in the trunk when you don't. Increased utility on demand, no permanent loss in economy--truly the best of all worlds  

just keep in mind.. a SIDE MIRROR is like 6-10% of the total drag your car has..

ROR--do you recall where you got that info? I would be interested in further investigation about how to reduce that--it seems like an easy way to get a noticeable increase in fuel economy, to address that drag. Anyone aware of any potential solutions?