Tires and gas mileage

[TGGRRR (Ali)]

I know that properly filling your tires will give you the best gas mileage but I've noticed a difference when switching between run flats and regular tires.

 

I've been on run flats since I bought Tigger, so I knew my gas mileage.

 

When I bought the Rotas they came with regular tires. My gas mileage went up noticeably. I was seeing an average of about 2 more miles per gal. My hwy mileage went from 30 to 32 mpg and my average miles for week day driving went from 24 - 26.

 

then I put the snow tires on which are run flats and my gas mileage went down again. This weekend I drove up to Baltimore with no traffic at all and could do better then 29.5 mpg.

 

At first I thought maybe the cold weather gave me better gas mileage, until I got back on the run flats.

 

Anyone else notice this?

 

Ali

[carman63]

Are the tires the same size across the board? Differences in tier circumference will change your speed and mileage slightly, which would affect the odometer reading and therefore, your mpg calculations

 

That, coupled with the rolling resistance, wheel weight, and a few other factors could add up to the difference you're seeing.

[TGGRRR (Ali)]

Both sets of tires are 17" but the Rota's are 215's and the Runflats are 205's

 

Would that make a difference?

[gtrnka]

I am considering not replacing my runflats next time I do a tire change. I'll run the risk of a flat tire but that is what slime and a pump are for....LOL....

 

When the time comes I will be asking for advice.:itsme:

[Edge]

Ali - one other very significant factor is the weight of the wheels themselves. You didn't just change to non-runflats, you also changed wheels. I'd be willing to bet that your Rotas weigh notably less than the wheels you had prior (and also than the wheels you have your snow tires on).

 

That alone can make the difference. The only way to truly compare the effect of tires on mileage is to test them both on the exact same wheel type.

[TGGRRR (Ali)]

I'm going to do the same thing Greg. I've done a lot of research and have decided I would much rather have an all season performance tire, I know Craig is happy with the one he has.

 

I figure if I carry a portable compressor and some slime. For longer trips I'll buy a small donut tire to carry, and if we take both cars Mark can carry the tire.

 

Run Flats are more expensive, they don't last very long and if you were stranded somewhere in the middle of no where, even if you can limp to a garage chances are they won't have run flats in stock. For this winter I had these tires, so figured I'd get a season out of them.

 

Ali

[TGGRRR (Ali)]

That makes sense Haemish

 

I miss my Rota's, I'm on the Web spokes now.

[Edge]

I figure if I carry a portable compressor and some slime. For longer trips I'll buy a small donut tire to carry, and if we take both cars Mark can carry the tire.

There is an official MINI spare tire - 1st gen Coopers (R50) didn't come with runflats and came with a spare. You can probably get that one. I also recall one enterprising lady who made (and sold) "totes" for the MINI spare to cleanly carry it in the boot, as a number of Cooper S owners bought the Cooper spare.

Run Flats are more expensive, they don't last very long and if you were stranded somewhere in the middle of no where, even if you can limp to a garage chances are they won't have run flats in stock. For this winter I had these tires, so figured I'd get a season out of them.

Yes, runflats are more expensive, but the difference in cost is not always as significant as you'd think. You have to compare runflat vs. non-runflat in the same brand and model of tire. If you're comparing one brand's runflats against another brand's non-runflats, it's an apples to oranges comparison. Some companies offer both (in the same tire design).

 

As for being stranded... your perspective changes when it happens during a snowstorm, and you're stuck on the side of the road with 4+ hours until a towtruck arrives, due to the sheer number of calls from people (mostly SUVs :laugh:) stuck in a ditch. Or, if you're traveling in a remote area... on NAM a few years back, one guy wrote of how he got a flat tire in Death Valley... and he said he would have been utterly screwed if not for his runflats. He had planned to get rid of them when they wore out. I agree that's also what a spare is for - but I'd personally rather not have to worry about toting a spare in my boot in the first place.

[cmcveay]

@ Ali. The difference in your gas mileage is probably due to the different weight of the RF's vs. traditional tires and (a combined effect) the different tire size between the tires you are switching between. If you compare the weights (as Edge stated above - compare the same brand/design or it doesn't work), you'll see that the RF's are heavier. It takes power (HP and torque) to make a heavier tire roll and to keep it rolling - it's like trying to push a heavier rock.

 

RF's and traditional tires all have their pro's and con's, it's a simple at that and it comes down to personal preference and the capabilities of the individual in question.

 

I opted to ditch the RF's for traditional tires because I lowered the car, stiffend the suspension and as a result the ride with the RF's was absolutely unbearable. The traditional tires with the "softer" sidewalls improved the quality of the ride and they really lowered the road noise level inside the car. I compromised and went with a lower profile tire that was wider than OEM so I kept that the responsive qualities of the car while getting a better sidewall angle to absorb the shock of road imperfections. (I'm running 235/45R-17's on 7.5 inch wheels so the tire beads are sucked in and the sidewalls are canted inward which protects the wheels from being curbed so easily and it creates an angular profile to deflect/absorb the bumps).

 

When I made that choice, it was knowing that I would be without a spare tire so I had to prepare myself. I now have a 12v compressor (that I have tested in actual use), a plug kit and a bottle of "Slime". I know how to use my tools and I'm not afraid of doing so. Of course, if I slash a tire sidewall, I'm not going anywhere but I have AAA, MINI roadside assistance and towing through my auto insurance.

 

This past Sunday, I did actually pick up a 2" long screw in my left front tire. The TPMS sensor detected the change in air pressure and alerted me. Here's a "downfall" of RF's. You can't tell by looking at them which tire is in trouble unlesss you can see the damage. The tire was low but not flat so I drove home on it (about a mile). It took roughly 20 minutes from opening the boot to closing the boot to make the car road worthy again.

 

As far as handling? The majority of the cars running autocross and track aren't on RF tires, the weight is a serious detractor for those who are really trying to win at those activities. I'm not trying to argue that one handles better than the other as that is an individual perception but what I can say that is I don't notice any decrease in the responsivness of my car with the traditional tires and that's even with the sport mode on - which makes the steering "heavier".

 

And then there's this. I can stop at ANY Sears, Discount Tire, Big-O tire or a basic mom and pop gas station and get a tire replaced, even if it's not the same brand. With RF's, not all stations will even try to mount/dismount them and it can be very, very hard to find a RF replacement tire if you are out in the "sticks"... Once you've run a runflat at speed and it's flat it MUST be replaced as they sacrifice themselves to offer that feature. When I have a flat, I'll plug it or slime it, air it back up and I'll hit the road. Beware though! Fix-a-Flat DOES NOT work at/below freezing temps!

[Edge]

@ Ali. The difference in your gas mileage is probably due to the different weight of the RF's vs. traditional tires and (a combined effect) the different tire size between the tires you are switching between. If you compare the weights (as Edge stated above - compare the same brand/design or it doesn't work), you'll see that the RF's are heavier. It takes power (HP and torque) to make a heavier tire roll and to keep it rolling - it's like trying to push a heavier rock.

I don't doubt that RFs are "generally" heavier, but I'd wager that the difference in wheel weight with Ali's switch was more significant than the tire weight, and therefore the larger impact in her experience. Rotas are known for their light weight!

RF's and traditional tires all have their pro's and con's, it's a simple at that and it comes down to personal preference and the capabilities of the individual in question.

Agreed!

I opted to ditch the RF's for traditional tires because I lowered the car, stiffend the suspension and as a result the ride with the RF's was absolutely unbearable.

"Unbearable" is relative. I honestly don't give a crap how harsh the ride is, provided I get the driving feel I want. If I wanted a Cadillac, I would have bought one! Different people, different preferences.

The traditional tires with the "softer" sidewalls improved the quality of the ride and they really lowered the road noise level inside the car.

Absolutely true. No argument there - software sidewalls lower the noise and smooth the ride. Check out the sidewalls on (stock) Cadillacs!

Here's a "downfall" of RF's. You can't tell by looking at them which tire is in trouble unlesss you can see the damage.

Well, in 2nd Gen MINIs, the TPMS reports which tire is low - but you have to have the factory Nav system to see it. In 1st Gen MINIs (or 2nd Gen without Nav), it's nothing that a tire gauge can't tell you very quickly.

As far as handling? The majority of the cars running autocross and track aren't on RF tires

Track driving (even autocross driving) is a totally different animal than street driving.

 

Non-runflats tend to have softer rubber, as well as more sidewall flex (obviously). This does increase the limit of handling - i.e. in very hard corning or very fast sweeping turns, non-runflats will generally grip better. That obviously is preferred in high performance environments, which the track clearly is. However, when driving on the street, it's exceedingly rare to actually need to handle at the limits of the car. The majority of our driving is dodging in and out of traffic. That's why I love runflats, because the steering response is positively amazing with the ultra-stiff sidewalls. It feels like a dragonfly (or a bumblebee, or a hummingbird...), where quick lane changes are immediate and without "mushy" tire roll.

 

By the sounds of how you've set up your car, you've done some things to counteract this (running 235s on a MINI is certainly an "extreme" setup!), but many people may not want to go to those lengths.

 

Don't get me wrong - if I was buying tires for the track (or for autocross), I'd buy non-runflats. Just not for the street/highway.

 

True, getting service on RFs is more difficult, but that is slowly changing over time as RFs become more and more common. I wouldn't take my MINI to any Mom and Pop place anyway (if I had a choice). I pay for the AAA Premier membership, which includes a 200+ mile tow. In most cases, that's far enough to get to a MINI dealership, for example (unless you're driving cross-country, perhaps).

Beware though! Fix-a-Flat DOES NOT work at/below freezing temps!

Yup! All the more reason to buy runflats for a winter set. It's why I went for the Blizzaks (despite my dislike of them for the DC region) over the non-runflat Pirellis when those were the only two choices I had left in the size I wanted (205/45R17).

[cmcveay]

Edge,

My only disagreement would be on the TPMS system telling you which tire. Maybe with the NAV system but, without it, you just know that it's one of them. Or did I miss something... Which is entirely possible.

 

Totally agree with the wheel weight being a factor as well. Ali is fixated on tires right now so I didn't want to bring in the other variables and confuse her ya know!

[TGGRRR (Ali)]

I am not fixated on tires, I'm simply in a state of deep research

 

[RichSperry]

Before I even bought the Mini last year, I ordered a set of 16" wheels, tpms sensors and run flat snow tires from TireRack. I just didn't want to deal with any flat in winter.

 

As soon as i use up the stock 17" rf tires, I won't be getting runfalts to replace them.

[gtrnka]

I am not fixated on tires, I'm simply in a state of deep research

 

 

Hmmm :hmmmm: scary thought....:alberteinstein:

[Edge]

Edge,

My only disagreement would be on the TPMS system telling you which tire. Maybe with the NAV system but, without it, you just know that it's one of them. Or did I miss something... Which is entirely possible.

Craig,

 

I do believe you skimmed - are you trying to take Ali's title?

Well, in 2nd Gen MINIs, the TPMS reports which tire is low - but you have to have the factory Nav system to see it. In 1st Gen MINIs (or 2nd Gen without Nav), it's nothing that a tire gauge can't tell you very quickly.

[MOMINIDC]

That makes sense Haemish

 

I miss my Rota's, I'm on the Web spokes now.

 

I also agree with Edge that the weights of the wheels are a factor. Don't know which Rotas you had but they're around 17-19lbs each, whereas your web spokes (looks like R98?) are around 22lbs each. Add the runflats' weight (around 21-22lbs each and probably a bit more than non-RFs) and that's higher unsprung weight at each wheel than the Rotas/non-RFs, and perhaps that's why your mileage is lower.

[GreenCactus]

I've only had my winter tires on for a few days, so I can't comment on my gas mileage yet. However, my winter wheels are 5 pounds (each) heavier than my summer wheels. Cricket just feels heavier. I can imagine that extra 20 pounds will make some difference in my gas mileage.

 

Both my summer and winter tires are runflats, so they should weigh about the same.

[cmcveay]

Edge,

Well, my "bald" is supposedly contagious so it looks like Ali's "skimming" is too! I actually did read that but my brain didn't process it right. I'm fine with it just telling me that there's a low tire though.

 

Looks like we solved Ali's MPG problem/question though!

[TGGRRR (Ali)]

grrrr you guys never give up a chance for a shot at Ali

 

Don't think I'm not noticing

 

Thanks for solving my little mystery

[Edge]

Totally agree with the wheel weight being a factor as well. Ali is fixated on tires right now so I didn't want to bring in the other variables and confuse her ya know!

Looks like we solved Ali's MPG problem/question though!

I can appreciate you not wanting to confuse, but I spoke up because I thought that the runflats were getting more blame than they deserved. I don't think they deserve quite as much hatred as I've seen some people give them (for years now). I suspect the added weight for runflat vs. non-runflats is probably little more than 1 lb per tire in most cases (with all other factors being equal, like same size). Rota wheels vs. OEM? Umm yeah much bigger difference.

grrrr you guys never give up a chance for a shot at Ali

 

Don't think I'm not noticing

Oh Ali - you know we wouldn't do that if we didn't love ya!

[TGGRRR (Ali)]

Oh Ali - you know we wouldn't do that if we didn't love ya!

 

 

I feel the love

 

:love::marshmellow:

 

Thanks for all the input guys.

 

Ali