Has anyone thought of using 4 'donut' tires? - Page 5 - Fuelly Forums

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Old 12-25-2006, 08:56 PM   #41
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Quote:
Originally Posted by The Toecutter
Honda complains it never sold enough Insights, but the real truth is, it never made enough to meet demand.
This is a bit off topic, but I remember the very first ad I saw for the Honda Insight:

An old Volkswagen Bus comes to a stoplight and the camera shows all the "Tree-Hugger" statements plastered all over the bus. Next, a weird looking car (the Insight) pulls alongside it, and I think both vehicles drive away when the light turns green. Right after that, there's text stating the Insight name and the (then) ludicrously high fuel economy it got.

Ever since then, I've never seen another ad for the insight . Too bad. it was a good one.
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Old 12-25-2006, 10:16 PM   #42
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185mm wide tires are crazy, even 175's are to wide for my taste, I feel very confident cornering as fast as I want with my 165mm wide tires, altho they were hard to find, they were well worth the search, and I think my next set is going to be 155mm if I can find some in a high performance modle.
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Old 01-04-2007, 03:01 PM   #43
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Quote:
Originally Posted by landspeed
I think the following video is probably a definitive comment on the use of 4 donut tyres on a car:

http://www.youtube.com/watch?v=T_1A4...elated&search=

It is FF drifting, and general craziness. Notice, just after one of the guys hanging out of the car punches the police car (37 seconds), they start doing
some FF drifting (47 seconds), You can see how thin the tyres are - they deliberately use those tyres so that they can slide around more easily. They can also drive completely sideways (e.g. at 55 seconds), without flipping the car over, despite doing very high speeds. It is also easy to lose control, and in fact they almost died at about 1 minute, by hitting a post!
Hmm, I'd have to disagree with you a little here. I think they are normally on stock tires, but at 47 seconds they do defintly look extra small/thin.

More imporantly, you can slide around just like they were doing with regular tires, and a removed front sway bar. For example, right after the first time I put a full tank of E-85 in the Lincoln, I was driivng home (on a closed course) on a divided highway. As I approached my corner I thought it would be fun to pitch it sidways (80mph) so I did. It did not roll, the body leaned until the suspension was completley resting on the bump stops (happens a lot), but there was no time I've ever been worried about rolling the car. It's nearly impossible unless you have an SUV or R-compound tires.

::EDIT:: hahaha, I just remebered the look on the drivers face of a pickup who was waiting at the corner! I'm sure he thought I almost died.
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Old 01-23-2007, 05:35 PM   #44
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My goodness, I started this thread in 09/06

Bought myself another never-used donut for my Geo for $8 a few days back. I could do a mini test sometime by attaching them to the front-drive wheels, but I want to wait until the snow clears up more.

Possible advantages to donut tires (for fuel economy):
1) less tire contact area
2) can be inflated to 60psi
3) lowers the vehicle
4) less rotational weight
5) faster acceleration

Impending disadvantages:
1) makes gearing shorter (bad for highway)
2) handling and braking characteristics worsen
3) low tread life
4) speedometer/odometer will show higher than actual speed/distance
5) makes wheel well space larger
6) might throw out alignment (but probably not)
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Old 01-26-2007, 09:59 AM   #45
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Now that the Geo is done being repaired at the shop, I decided to put the 2 donut tires on the front to give them a try and see how they feel:

Before:
Attachment 175

After:
Attachment 176

It did a good job of lowering the nose a bit but look at that massive wheel well space! I placed the bigger tires in the rear hatch, so my weight is the same. The odometer reads 248,547.35 kilometers when I did this, so I'll make a mental note that my speedometer will be optimistically high from this point on. This will also be needed to be taken into consideration since 1/2 of my tank was with the original tires, and the next half will be with the donuts. I plan to keep them on for as long as possible so I get a good sample. A-B-A testing really isn't practical since it still feels like 3*F outside.

Edit: I just went on the highway to see the difference in the speedometer. I drove 100km/h (read from the Scangauge II) and the "your speed" sign on the highway read 91km/h. I've noted the sign before with the normal tires and it's very accurate.

This means that all my speeds/distances will need to be multiplied by 0.91 to give the actual speed/distance.
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Old 01-26-2007, 10:05 AM   #46
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Looks like you could run duct tape over those wheel wells and cover a considerable amount of the space. I even think that it comes in green.
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Old 01-26-2007, 10:46 AM   #47
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Quote:
Originally Posted by Ryland View Post
185mm wide tires are crazy, even 175's are to wide for my taste, I feel very confident cornering as fast as I want with my 165mm wide tires
Agreed!

just drove 185/65/14s on hxs after driving on 165/70/13 vx's for a while, and whoa, i felt like i was glued to the ground. It is too much for 70hp. I love the 165/65/14 lrr potenzas on my new hx's, and am hoping the 175/65/14s I will be putting on soon won't be too much. They are the lrr kumho 795, so hopefully they will be smooth and quiet, and as light as kumho claims. 14lbs, we'll see.
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Old 01-26-2007, 02:28 PM   #48
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Exclamation First Impressions

After a short 81.3 mile drive today with the donut tires this is what I have to report:

The Good:
1). Incredible coasting capability. With the donuts on, the Geo can CODFISH like I couldn't imagine!
2) Uphill climbing is a sinch! I drove up a steep hill (one that usually takes me from 60-45mph by the time I get to the top) and the car only decreased in speed by about 3-4 mph (from 55mph, real speed) by the time I got the the top. No foot pressure was needed, the cruise control had it down pat.
3) Braking seemed to be just as good as before.

The Bad:
1) Speed is shown to be higher (both on SG and speedometer) so when I'm doing 100km/h (62mph) I'm actually only doing about 91km/h (56mph). This means the odometer needs adjustment for figuring out FE.
2) the Geo rides like a tank! I have to go across a gravel road to get to my cheap gas station and the glovebox kept opening from all the nasty bumps.
3) the RPMs are higher (for the actual speed) than if I had the original tires on. 3000 RPM (@ 60mph, real speed with regular tires and wheels) divided by 0.91 is around 3300 RPM (@ 60mph real speed, with donut tires).

The Questionable:
1) The car's acceleration seems to be a lot faster whether in city or on highway, but again this could be an illusion as I'm technically going slower than what the SG and speedo says.
2) Handling. The car did have a considerable amount of understeer on icy turns, but remember: I had ice-trac tires on. So this comparison would be unfair.
3) Aero improvements/disadvantages. The car is a bit lower now and there is less width to the tires, but now there is more space in the wheel well.

And Finally: the appetizer FE results (19.4*F with 30mph N/W winds and cruise control on flat terrain):

Going north-west:
55mph: 41.0mpg (actually 37.3 mpg @ 50 mph)
50mph: 42.8mpg (actually 38.9 mpg @ 45.5 mph)
45mph: 45.5mpg (actually 41.7 mpg @ 41 mph)

Going south-east:
55mph: 58.8mpg (actually 53.5 mpg @ 50 mph)
50mph: 64.8mpg (actually 59.0 mpg @ 45.5 mph)
50mph: 65.5mpg (actually 59.6 mpg @ 41 mph)

I've even had a couple of 'Current MPG' readouts in the mid 70s @ ~45 mph real speed. Granted that's only high 60s in real FE, but that has never happened to me before on highway driving.

So in other words FE increase/decrease is not conclusive with this information. It's also really strange that FE (according to the SG) was pretty much the same @ 45.5 mph real speed compared to 41 mph real speed (this pattern was predominant thought the trips).

Overall, I'm really intrigued by the unusual results. I think it's definitely worth A-B-A testing when the weather gets nice in the future. Like I said in a previous post, I'm going to keep the 'donut' configuration on for as long as possible and see how my future tanks turn out (just filled my tank today and came out with 48+ mpg).
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Old 01-26-2007, 03:12 PM   #49
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Quote:
Originally Posted by zpiloto View Post
Be careful those tires are not designed to last very long and have a max speed around 50 mph. Let us know how the tread wear goes.
Yeah that's what I've been told. I checked the wear just a few minutes ago and it seems fine, for now.

Actually, *looks at owner's manual*: "The compact spare is made to perform well at posted speed limits for distances up to 3,000 miles (5 000 km), so you can finish your trip and have your full-size repaired or replaced where you want."
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Old 01-26-2007, 05:43 PM   #50
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Quote:
Originally Posted by Peakster View Post
The Good:

2) Uphill climbing is a cinch! I drove up a steep hill (one that usually takes me from 60-45mph by the time I get to the top) and the car only decreased in speed by about 3-4 mph (from 55mph, real speed) by the time I got the the top. No foot pressure was needed, the cruise control had it down pat.

The Bad:

3) the RPM are higher (for the actual speed) than if I had the original tires on. 3000 RPM (@ 60mph, real speed with regular tires and wheels) divided by 0.91 is around 3300 RPM (@ 60mph real speed, with donut tires).

The Questionable:
1) The car's acceleration seems to be a lot faster whether in city or on highway, but again this could be an illusion as I'm technically going slower than what the SG and speedo says.
No illusions. You have effectively geared the car 10% lower. You should expect 10% quicker acceleration by changing the engine revolutions per mile by the mentioned factor of .91.
My winter snow tires have taken me the other way. The OEM summer size is 215-50-15. My soft tread, (high rolling resistance too I presume), snow tires are 205-60-15 or about 14% taller than the speedo and odo were intended to use for accuracy. My acceleration is more leisurely, but my rpm (and speedometer) are lower at a true road speed. It also means my fuel economy has taken a hit because my 'miles' are now 14% longer.
On the plus side my office is now 14% closer to home.
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