Bridgestone Delaminate = < MPG

[drmajor]

Interesting thing happened along with my Bridgestone 020 chunking some rubber.

Lately I noticed my MPG going down. No explanation.

Got new 020 put on and instantly the MPG went up more that 5 MPG!

Obviously, the internals of the tire are worse off than what I can see.

[graydude]

I changed my oil and filter as well as new stones front and rear at the same time. Since the day I took it off the jacks my MPG has gone down at least 5 MPG. I kept thinking it was the oil but I've used Amsoil 20/50 now for the last three changes. I never thought about the tires. I did notice a boat load of weight on each tire from balancing after I picked them up from Cycle Gear after being mounted. Do you think there is a connection?

[Holy Cow]

I can't see that balance or the weight of the tire making a difference. However, if the outside diameter of the tire is different, then that might make a difference.

How are you determining fuel economy?

Say you topped off your tank, drove 45 miles (using the odometer on the bike, and assuming it is accurate) to a gas station and found it took exactly 1 gallon, then your mileage is 45 miles/gallon.

Now, put a bigger tire on. Drive to the same gas station, and now the odometer is going to read less, lets say 40 miles, but you still use a gallon of gas (more on that later) so the indicated fuel economy dropped to 40 mpg, but in reality you went the same distance using the same amount of fuel, the fuel economy is the same.

But, is that really true? If you think about an engine, at a constant throttle position, each cylinder intake event should draw in a constant quantity of fuel, so, everything else being equal, the quantity of fuel used should be directly proportional to the number of crankshaft revolutions. That makes sense, right? If you make my hypothetical trip at 60 mph you would get, say 45 mpg. Now, make the same trip, but at 70 mph. Assuming you never shift out of 5th gear, the crankshaft has spun exactly the same number of times between the two trips, but you do need to crack open the throttle a little bit more, which allows in a little more air, increasing the volumetric efficiency of the engine, and causing the fuel injectors to spray fuel a little bit longer. The net effect is that you used a little more fuel, and the fuel economy dropped a bit.

Ok, back to the bigger tire. If you make the same trip and everything is the same, including the real speed, then with a bigger tire, the wheel spins slower and there are few crankshaft revolutions, so that would save fuel. However, the bigger tire will require more torque to turn (bigger lever), so the engine will be required to produce more power, which means opening the throttle a little more, and therefor using more gas. So, each cylinder event will use a little more fuel, but there are fewer cylinder events, so I don't know which would win. If the power required to drive the bike increased a lot with the bigger tire, I could see it really causing a drop in fuel economy.

Something to chew on, at least.

[messenger13]

Larry...your username says it all. :) I read your post and said, "Holy Cow! This guys knows his stuff!". http://www.r1-forum.com/forums/images/smilies/yesnod.gif But I digress...

Some factors you may need to consider.

Knowing both David and Todd, I know that they are GPS users. I'm fairly positive that they calculated there fuel economy using the actual distance covered with their GPS units, not the odometer or the LT's BC. They calculated gallons used according to the fuel pump. So the accuracy of these two factors should remain fairly constant.
The Bridgestone BT-020 is a "bigger" tire than the Metzeler due to it's rounder profile. The Metz is a flatter tire, as it is a Bias-Ply tire. So this factors seems to support your suspicions in your last paragraph.
So let's see...the Bridgestone BT-020 Radial is known to delaminate, doesn't get the mileage that the Metzeler gets, AND now may be found to cause decreased fuel economy. This just gets better and better...doesn't now? :D Seems a pretty high price to pay for a leetle edge in the performance department.

Bring on the Avons and the B'Stone Bias-Ply tires!!!

[ErnieA]

I changed my oil and filter as well as new stones front and rear at the same time. Since the day I took it off the jacks my MPG has gone down at least 5 MPG. I kept thinking it was the oil but I've used Amsoil 20/50 now for the last three changes. I never thought about the tires. I did notice a boat load of weight on each tire from balancing after I picked them up from Cycle Gear after being mounted. Do you think there is a connection?

I've been using Amsoil for nearly a year now and immediately noticed an avg of 2 MPG increase and a reduction of engine coolant temperature (at least at the gauge). For one I'm not concerned with the performance of this lubricant. However, the idea that the BStones are delaminating, and reducing MPG, is of concern for me because I'm scheduled to change over to some BStones in a few months. Perhaps a few of us can accumulate some definitive data that will help diagnose whether or not the definitive are truly a problem that is exceeding a nominal failure rate.

[drmajor]

Joe,
You are right about MPG-
I got the best millage from the 880- 48 average and up to 51 MPG.
When I put on the BS020 rear and Avon front, it dropped to 45-48.
When I put on the BS020 front and rear, it went down to 43-46.
With the delam- BS020, it was under 40.

Love the 020 handling, but don't know if I'll use them when my supply is gone. Might try the 020 Bias.?

The 880 feathered pretty bad at 4000 miles. At 6-7,000 they started howling in 50 MPH+ sweepers, and started making the bike shake some in the sweeps. They did last till 13,500!!! I Just didn't like the ride

[meese]

That all sounds reasonable. But remember, you'll get a far bigger effect due to wind resistance, especially at higher speeds. Why do you think Burt Munro's bike looked like a small rocket. :)

[meese]

Remember Ernie, those are Bias BT020's in your garage. I don't think we've had any reports of those failing.

At least in my case, the BT020 Radials get less gas mileage because they're more fun to run hard. :D

[BillCav]

I used to ride a Yamaha Venture Royale and went through many sets of tires. Early in the life of the Venture I went to Dunlop and loved the wear and handling. I've only owned the LT since March 05. I have never read a thread talking about Dunlop tires on an LT. Has anyone ever had Dunlop tires on their LT and if so are they any good?

Cheers, Bill

[dshealey]

I used to ride a Yamaha Venture Royale and went through many sets of tires. Early in the life of the Venture I went to Dunlop and loved the wear and handling. I've only owned the LT since March 05. I have never read a thread talking about Dunlop tires on an LT. Has anyone ever had Dunlop tires on their LT and if so are they any good?

Cheers, Bill

There have been many threads on Dunlops over the years, starting with the old Yahoo group.

BMW put Dunlop D205's on LTs for a while after they stopped using the Bridgestone Excedras because of VERY low mileage. (The Excedras stuck like the proverbial glue though!) the Excedras were radials, the Dunlops bias ply. My first LT (2000) came with Dunlops. Decent mileage, but that was about it. Mine were toasted at 11,000 miles. Not very good handling in the twisties, and were the NOISEST tire I ever used, by far, once about half worn. They howled like bansees on ANY lean angle. So much so that you could ride near the center line on a straight two lane road and they were quiet, but just moving over to the right side of the lane where the road crown was more and they howled. Did not have to even lean the bike into a turn to get the howling. BMw did not use them very long, switched to ME880s when they came out, then started using both them and BT020s after Bridgestone introduced them to replace the Excedras.

I don't know if Dunlop has changed the tires any in the last few years, but if not, I certainly don't recommend them.

[Dick]

And David, weren't the Dunlops (D205x) famous for rubbing the swingarm and necessitating the installation of an additional wheel shim? Been so long ago, I've forgotten if the Dunlops were the culprit, or one of the other brands.

[BillCav]

I don't know if Dunlop has changed the tires any in the last few years, but if not, I certainly don't recommend them.

Thanks for the info David, It's hard to believe that one bike can virtually not have a problem with a certain type of tire but put the same tire on a different bike of similar weight and size and all hell breaks loose. I also noted to my dealer that the LT slipped many times for me in the rain on the steel bridge expansion joints and on corners. I also have had Bridgestone tires and hate them, not for the grip but the composition failure (bubbles & cord breaks).

Cheers, Bill

[ErnieA]

Remember Ernie, those are Bias BT020's in your garage. I don't think we've had any reports of those failing.

At least in my case, the BT020 Radials get less gas mileage because they're more fun to run hard. :D

This is very good to know since I very much like to test the lean angle at a very low MPG. http://www.bmwlt.com/forums/images/icons/icon12.gif With Bias BT020's I should break even on the MPG and have more fun than with the ME880's.

[dshealey]

And David, weren't the Dunlops (D205x) famous for rubbing the swingarm and necessitating the installation of an additional wheel shim? Been so long ago, I've forgotten if the Dunlops were the culprit, or one of the other brands.

Yep, that was the one. BMW dealers added a second shim to space them away from the swing arm when they rubbed.

This just came up recently here, as someone had Dunlops that were rubbing.

[Holy Cow]

I agree I also had an '86 Venture Royale and always used Dunlop K491 (Elite II and now Elite III) and thought they were great. Anyone run then 491's on a K1200LT

[messenger13]

Anyone run then 491's on a K1200LTThey're not rated to handle "the load".

[BillCav]

They're not rated to handle "the load".

Interesting cause my 87' Venture was 950 lb. wet not including rider(s) and my friend and his wife had Dunlops on a "Wing" and they both had a combined body weight of 575 lbs.

Cheers, Bill

[messenger13]

Well if they make one that fits the LT . . . by all means, try them out and let us know how they work for you. Lord knows I'm not in love with any of the options that I know of currently. (Although, eventually I do want to try the B'Stone Bias-Ply.)