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I'm assuming my spare is around 30 lbs or so, and of course extra weight = less FE. However, I don't want the risk of no spare and was wondering if other Hypermilers use something else such as a repair kit and compressor...and if so any suggestions on brand?

If your car has a full-sized spare, you could save a few pounds with a limited service (donut) instead. Not personally a fan of those, though.

Roadside patching can only be done with a 'plug' and those are not a good idea in radial ply tires. The appropriate way to repair is with an internal flat patch, which of course requires dismounting the tire.

The aerosol cans (like fix a flat) are OK for emergencies but the will leave a lot of goo in the rim and your tire installer won't appreciate it next time.

In short, I know of no really good ways to accomplish your plan. It is a good idea to carry a 12 volt tire inflator though. Even the $20 ones are capable of doing the job, but good to test yours before you really need it.

DAS

If your car has a full-sized spare, you could save a few pounds with a limited service (donut) instead. Not personally a fan of those, though.

Roadside patching can only be done with a 'plug' and those are not a good idea in radial ply tires. .......

DAS

Good idea or not I've plugged in the ballpark of two dozen (I've lost count because I plug 'em at home and at work) in radials and the only problems I've had are slow leaks in two of them that had ragged holes. It seems like most of the flats I get are from nails/screws where plugs work pretty well. Plugs won't help with sidewall holes, blow outs or really big holes.

I just carry a can of fix-a-flat, a plug kit and a cell phone around town, but sometimes throw the spare and jack back in on long trips. The last time I used a donut spare (for a case of tread separation blowout) it was old and rotten so that it flatted too within 1/2 mile, at night, in snow and slush. :(

If you're carrying around a spare inspect it once in awhile so you don't end up like I did.

Carry the spare tire (full-size or donut), inspect it every so often. Around town, a cell phone's OK, but on longer trips or late at night the spare tire comes in uber handy. Also, swap the OEM jack & wrench for a lightweight aftermarket jack and regular lug wrench. You can come out with the same weight, but save yourself a LOT of grief if you destroy the tire.

Another option is to just fill the whole thing with sealant. messy, but lightweight and will stop most holes (Oilfield trucks do this a lot).

According to the Prius MPG Simulator (http://privatenrg.com), reducing weight in the Prius by 30# increases fuel mileage by 0.33% or less (depending on speed). The simulator assumes steady speed, so I'm guessing the effect is magnified somewhat with frequent accelerations and decelerations. I suspect the gain still is negligible, and to me it's not worth the tradeoff of not having a spare.

You don't say what kind of car you have, so the usual caveat applies: YMMV. A lighter-weight car might see a bit more of an effect, though I can't imagine it would be much.

There are cars designed for use without a spare. They use run-flat tires instead. Run-flat tires have stiff sidewalls to hold them up when there's no air pressure. The stiff sidewalls lower FE -- presumably a lot more than carrying around a 30 lb spare. Manufacturers generally use them in cars where space is at a premium, like convertibles and hybrids.

I have a donut, and it's served me well. I've learned to carry a spare tire (not just a tube) when cycling long distances as well. The main suggestion I'd make with a donut is to move it to the rear (on a FWD) as soon as it's convenient after putting it on -- you'll have better wear, better traction, less wear on the differential and higher FE. Putting it on the front of a FWD non-CVT will lower FE, whereas putting it on the rear should raise it above 4 normal tires. A test on Gassavers confirmed a significant increase from two donuts on the rear.

I'd also suggest that there are rare occasions where extra weight helps more than it hurts, since it'll help extend glide times. It depends on the particulars of your commute.

smaller alum rim and light tools will help. or the fixaflat/cell phone in case you have a chunk missing from the tire.

Manufacturers generally use them in cars where space is at a premium, like convertibles and hybrids.


You sure about that? Every hybrid I'm aware of uses LRR tires to boost FE, not run-flats.

Points well taken - I would never go on a long distance trip w/out a spare, but I was thinking of more my daily drives that are well commuted along w/my cell. If the numbers of .33% are true, every ounce adds up.

Does the fix-a-flat damage the wheel and/or tire permanently, or just piss off the tire shop?

Short answer : yes it would save minute amount of gas.
Best answer : you can be penny wise and pound foolish.

Does the fix-a-flat damage the wheel and/or tire permanently, or just piss off the tire shop?



It won't damage the wheel or tire but most shops will refuse to fix the tire once you run that stuff trough it. Not only is it messy but it's very difficult to clean up. You'll find yourself buying a new tire.

Points well taken - I would never go on a long distance trip w/out a spare, but I was thinking of more my daily drives that are well commuted along w/my cell. If the numbers of .33% are true, every ounce adds up.

Does the fix-a-flat damage the wheel and/or tire permanently, or just piss off the tire shop?

It makes working on the tire an absolute B$$$$, but by the time you'd need to do more than a cover patch the tire will be Swiss cheese anyway. You have to clean the wheel off if the fix-a-flat gets on it. a pain, but not impossible.

Most good garages will fix tires with small amounts of fix-a-flat. Beyond that, its a lost cause anyway.

I've used a tire plug kit for many years. As long as the hole is not in (or very near) the side wall, the plugs seem to work well. Shops I've visited use them. Ones I've inserted have lasted (let's see) 3 or 4 years for me. I've never had one fail. So, I carry a small kit that includes the tool to remove the screw or nail, and it doubles as the tool to insert the plug. I use a soap solution (Snoop) first to find the leak, and second to check the repair. I do this at home (because I don't normally carry Snoop with me). On the other hand, I've never filled a plugged tire to 45-55 psi, only to posted pressure. Perhaps someday soon I'll get that chance with my Aveo - I've got it up to 55 psi presently.

I can't wait to see what the airless tires can do.

.....I use a soap solution (Snoop) first to find the leak, and second to check the repair. ......

I've noticed that Windex (or the homebrew equivalent) works as well for tires as the Snoop does and the widespray squirt bottle is the right tool for the job. Personally I like to use rubber cement as my lubricant to buy a little more insurance against leaks.

I have used nothing but plugs for nearly 20 years now with almost absolute success. It takes less time to plug a tire than it does to jack the car up literally and in fact I rarely do be it car or truck. That's as long as I can find the hole. The hardest holes to fix are the tiny ones that don't show themselves, the easiest are nails sitting there looking at you. The big problem at the side of the road doing this sort of thing though is the danger of other vehicles hitting you. I would hazard that in the city at certain times of day and situations but your situation may dictate otherwise. I will say that there is probably no more dangerous place common to all of us on earth than the side of an interstate highway, even one being sparsely used. Been there seen that one or at least my wife did.
We used to have a 96 grand cherokee that the spare stole about 1/4 of the rather small rear interior. Unless going long distance which was rare the spare sat in the basement. All we ever had was 2 cans of run flat and a small inflator you plug into the dash. Minimal but enough to get you going to someplace to fix it right if driven slowly. The inflate a tire cans of goop do work though not enough to get much more than 20 psi. The repair places might not like the stuff but that's their problem. It's not really intended for long term use but I haven't seen any signs of it causing problems.
As for sealing pesky leaks and doing a better job the best stuff is that bright green stuff you see in Walmart and everywhere else. I think its called SLIME. That is what I typically put in after I plug a tire to make sure it stays sealed. Great stuff in my experience but it doesn't come in an inflater can which can be a negative and another good reason to carry a tiny compressor. They are damned slow but they do work.

When i owned my Chrysler Crossfire, i discovered that it did not have a spare. It had a can of goop(tire sealer) and a 12V compressor. I bought a plug kit from advance auto parts for 10 bucks and carried it in the Crossfire.
The smart also carries no spare. Same deal, a can of goop and a compressor. I have the plug kit in there now. I actually do have a tire and wheel i bought as a back up, but i leave it in the garage. If the tire cannot be repaired roadside with the plug kit or goop, i will just have AAA tow it to the smart dealer, or to my house.

It seems to be more common for cars not to have spares these days. You could ditch the spare for driving around town, as mentioned above, but if you leave town DON'T FORGET to put the spare back in. Personally, I wouldn't trust myself to always remember, and the one time I forgot the spare would almost certainly be the one time I got a flat. For the tiny amount of gas it would save (on my cars it should amount to about 0.15-0.2mpg in urban driving) , I personally choose to leave the spare in the car.

Run-flats... it scares me a bit but i've seen them a lot these days ( Cruze, Elantra, etc... )

The last two flats that I've had couldn't have been repaired by a can of goop, plug kit, and compressor. One occurred when a semi swerving into my lane forced me to hit a traffic island which dented the wheel rim and popped the tire bead off the rim. The second flat occured when some sharp road debris made a rip in the sidewall. So I always carry a spare, full sized, because a donut spare would cause my wheel aero mods to scrape the road on bumps.

the 2011 Hyundai Elantra9US model) does not come with a spare. It comes with a pump and sealant. The canadian version comes with the spare. Hyundai states that with the 10year 100,000 mile warranty, you don't need a spare. That is BS. You get a blowout in the middle of no where (Let's say on the road from LA to Vegas) and you will be stuck for a while. Or, what if you're on a vacation and all of the tire shops are closed. You are forced to wait until the next day. With a spare, you could continue on.

We did buy the Elantra with the promise from the dealer that when US supplies the spare kit, they will contact us. 3 months later, we are still waiting.

There is so much you can do to shave off MPG, but when you start talking about no spare, then you are really taking your chances, JMHO

Run-flats... it scares me a bit but i've seen them a lot these days ( Cruze, Elantra, etc... )

2011 elantra does not have run-flats.

Hyundai states that with the 10year 100,000 mile warranty, you don't need a spare.

When did warranties start covering tires? The way they say that it seems like the tires won't get worn out or go flat for 100k miles.

In the past few model years, maybe still, the Canadian Honda Fit with automatic did not come with a spare: just had a can of "flat fix". The manual version did come with a compact spare.

The rational I heard was that the manual version was fairly fuel efficient, but the automatic's mileage was just worse enough that it tipped them over some boundary for economic advantages bestowed on the more fuel efficient vehicles.

So, to tip back the other way, they resorted to removing the spare. For an additional charge, somewhere between $200 and $300 I think, you could add the spare. So, going from manual to comparably equipped automatic cost you the usual automatic premium, plus this extra $200~300 for the spare.

Bottom line: Honda seemed to think the weight of the spare had a significant and measurable impact on mileage.

Personally, I would not drive without at least a compact spare. Even if I never use it, just insurance.

I carry a cell phone and a can of air in my EV. Won't ever be that far from home and the spare is extra weight and is really in the way.

On my van which spends about 2+ months a year in the wilderness on roads that make some people's knees shake and knuckles turn white I carry a real 6 ply extra tire, a couple of cans of air, tire plugs, a hand pump and heavy duty 12V compressor, fills a truck tire fast. In addition to a extra jack and blocking material.

Have used all at times.

Tip from the wilds about 12V pumps. Another driver came back to a low tire and put one of those slow 12V pumps to work filling the tire. As noted by many they are really slow so he went off in search of a short adventure on the beach. Came back later to find the tire almost full and the battery "empty"; he was unable to start the car. Happy we also had jumper cables in the box with all that heavy extra tire stuff. He thought his battery could do a tire, wrong.

FWIW if your planning for the worst the list can get a lot longer than a spare tire. For sure have a flashlight that works (or don't drive at night) as it makes putting the spare on a lot easier if it is dark and certainly safer if your on a traveled road. Also keeps the beasties away in the wilderness or at least you can see their eyes watching you.

A salvage yard is a good place to get a extra wheel to replace a space saver. Be sure the spare location will hold a full size tire.

But not counting the back country rock eating roads my personal experience (almost 50 years driving) doesn't include jacking up a vehicle more than a few times. Tires are pretty impressive when you consider what they take in the way of punishmnet.:flag: