Triumphrat

mbalce

I know there have been a lot of different threads on the large variance of gas mileage on these bikes. Thought I might share. Got my 2002 T100 about 2 months ago with 11k on the clock. Was getting a pretty disappointing but consistent 32-34 MPG which seems to be the very low range of reports. Didnt seem to matter much if I rode it hard or "for mileage" (when I thought about it... )

As mentioned in a different thread, I found that my front brake was dragging very slightly. Not enough to warp or otherwise damage the rotor, and I have also seen a lot of reports that leads me to believe that both: 1. Stock rotors are very susceptible to damage and 2: dragging brakes from infrequent fluid changes are not that uncommon on these bikes.

Just filled up this morning, probably 2/3 of this tank was run post-brake work. 43 MPG. Dont find any other variables to pin this on. Looking forward to reading the mileage on this next tank...

Just wanted to suggest to the people on the low end of mileage even after the bikes broken in to make sure your brakes are releasing properly and both tires spin freely.

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Mark
2002 Bonneville T100

DrewDesign007

I do hear a slight but constant grind from the front brake when I roll the bike (engine-off).

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Scored as a rocker!
75% rocker - 50% mod

mbalce

That could be pretty normal, pads almost always touch the rotor. My thing was on a lift, if I started spinning the wheel by grabbing the spoke as soon as I let go, the wheel stopped. Now it makes about a half to a full revolution, depending on how much muscle I throw at it.

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Mark
2002 Bonneville T100

Baltobonneville

Same applies to the back brake, worse if you keep your foot over/on it. The pedal sits too high for many riders. I tilt my foot to the right unless I'm using the rear brake, will eventually try to adjust it.

This might explain why many riders only get 5000 miles out of a set of rear brake pads. At 8500 miles, mine still have plenty of life left in them.

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Marty
2005 Bonneville Blue 790cc, AI removed, Staintunes RC, Unifilter, no snorkel, 120/40/Thrux needle/1 shim/3 turns, fly screen, tacho, D9 gauge panel, center stand, Ikon 7610s, Hagon fork springs, gaiters, Pirelli Sport Demons, 3 seats.

mbalce

I concur, I went to change my rears when I was doing my fronts and found they still had lots of meat left and they appear to be original. And thats with over 12k. Previous rider(s) must ride like me, I change fronts 2 to 3 times to a set of rears.

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Mark
2002 Bonneville T100

357Bob

One fillup won't tell you anything. May be a change in temp. You may not have filled it the same amount. The pump may be lying to you. Your math may be off. There may be an astroid coming.

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357bob

mbalce

yeah, I guess all those could have bigger affects on a mpg calculation than a dragging brake. Guess I wont worry about checking my air pressure anymore either...

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Mark
2002 Bonneville T100

357Bob

I don't know why but I can never fill my bike up the same way everytime. I try to fill it slow but it still splashes out on the tank. After 15,000 miles I still haven't mastered it. So I always come up with different amounts on a fill up. Sometimes I can get it to fill that recessed area then the next time I can only get it to the bottom of it.
Automotive disk brakes are supposed to pull the pads a little distance back from the disk. This was done for gas mileage. Bikes and/or Triumphs I am not sure of. I have never heard of it. If they did, the first apply of the front brake would have some free travel in it & might be dangerous. Bob.

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357bob

mbalce

My logic says that fillup variance probably doesnt throw things off more than .2 gallons even if you dont try to make a concious effort. Thats one reason you see 2-3 MPG variances on about a 3 gallon fill. (i.e. if I go 125 miles and fill with 2.9 gallons in I calc 43 MPG, which was this mornings fillup. If I would have managed to squeeze in 3.1, it would have still been just north of 40)

There is no free travel in motorcycle brakes, my understanding is at full release there should be ever so slight contact but little appreciable drag. Thats why you can hear brake contact on a lot of bikes when they coast. But there should be no significant friction. I saw a lot of difference in the amount of drag in the front wheel when it was on the lift after I put in new pads and completely changed the fluid. Actually probably flushed it more like since I pulled a whole new bottle of fluid through the system with a vacuum bleeder and just topped it off with the last little bit that was left. Also rode the bike for 5 miles without touching the front brake lever, hopped off and felt the rotor. Cool to the touch. I was happy.

The apparent MPG increase is just bonus, but since I have read a fair amount of threads on both dragging front brakes on these bikes and totally seperate threads on seemingly unexplainable mpg variances, I just thought I would throw it out as something to check if you have a bike that is getting on the lower end of the mileage spectrum and the two maybe connected in some circumstances.

And not to gloat, but here in Southern Cal there is not much temp variance this time of year. Sunny and 70s in the daytime with lows about 50.

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Mark
2002 Bonneville T100

J44Clark

Disk brakes pads run pretty close to the rotors. There are no return springs like on drum brakes. On application the pistons move toward the rotor slightly deforming the O-rings that sit in the groove in the pot. When the pressure is released the O-ring spring back just a bit carrying the pistons back with them and away from the rotors.

DOT 3 & $ brake fluid is hydroscopic, that is it absorbs moisture. After awhile that moisture will corrode the pistons and pots causing the pistons to bind in the pots and not retract fully. At some point they just don't retract at all and you get smoke, or at least I did. So change the fluid every two years as prescribed in the service schedule.

To test raise the front wheel off the ground and apply the front brake firmly. Then release the brake and spin the front wheel. It should spin easily and coast a bit with just the slightest drag between the pads and rotors. A rotor with too much lateral runout will drag hard at a certain spot. Bad bearings could cause similar behavior.

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'05 T100 creamsicle, TORS, xSnorkle, xAI, xRestrictor, Uni, 128/42