Fuel economy drop after changing rear tyre

[prasannar2009]

Hello everyone,

I got a new rear tyre fitted in a workshop since the earlier one had already had a couple of patch-jobs and it was time to get a new one. With the new tyre, I don't notice any difference in handling compared to before, but the fuel economy has definitely become worse. The onboard computer shows that it increased from 2.1 to 2.3 L/100km (about 10-15 mpg drop, or 5-6 km/L). I know it's not easy to calculate the fuel economy very accurately. But I can clearly see that in my last full tank the scooter went about 60 km shorter. So I'm pretty sure it's a significant drop.

Just wondering if the tyre change process could cause any difference in fuel consumption? I'm not 100% sure but I kind of feel a difference if I rotate the back wheel manually when the scooter is on its stand - a bit more resistance than before. I'm clueless, but I'm just curious if the procedure of removing the wheel and putting it back contains any step that could increase the friction in the rotating wheel, for example, some nut tightened more than necessary etc.? Or am I looking completely in the wrong place?

[you you]

Hello everyone,

I got a new rear tyre fitted in a workshop since the earlier one had already had a couple of patch-jobs and it was time to get a new one. With the new tyre, I don't notice any difference in handling compared to before, but the fuel economy has definitely become worse. The onboard computer shows that it increased from 2.1 to 2.3 L/100km (about 10-15 mpg drop, or 5-6 km/L). I know it's not easy to calculate the fuel economy very accurately. But I can clearly see that in my last full tank the scooter went about 60 km shorter. So I'm pretty sure it's a significant drop.

Just wondering if the tyre change process could cause any difference in fuel consumption? I'm not 100% sure but I kind of feel a difference if I rotate the back wheel manually when the scooter is on its stand - a bit more resistance than before. I'm clueless, but I'm just curious if the procedure of removing the wheel and putting it back contains any step that could increase the friction in the rotating wheel, for example, some nut tightened more than necessary etc.? Or am I looking completely in the wrong place?

You haven't been on the pies?

[cnikonpete]

Think this is the second problem reported after tyre change on rear wheel, it's possible that the hub nut has been incorrectly torqued.
Was it a dealer or tyre place? Have you noticed any change in performance?
I would take it back and tell them that you have noticed the extra resistance.

[Cube]

I'd make sure they put the right size tire on too.

[you you]

Think this is the second problem reported after tyre change on rear wheel, it's possible that the hub nut has been incorrectly torqued.
Was it a dealer or tyre place? Have you noticed any change in performance?
I would take it back and tell them that you have noticed the extra resistance.

X2

[iceman]

When on the centre stand, does the rear wheel move and spin ok or is hard to move? Best check the rear brake adjustment too in case they played with that and the rear brake is on too early or on all the time, however you would have noticed the rear brake lever difference if this was the case.

[Old Grinner]

If the tire is a lower profile it will spin more per distance traveled. . .kind of like comparing two circles traveling over a line of equal length. . .the bigger circle will rotate less and the smaller one will rotate more over the same distance thus causing a drop in fuel efficiency.

Also, if it were me I would check for any undue heat in the hub or weird smells. . .like burning brakes. . .or even a fuel leak. . ..

It's possible it could be either a sticking brake shoe or the cable is too tight. Also. . .if yours has a brake lock system I would check to see if that's set properly and not engaged.

One last thing. . .see if where the rear brake cable is connected on hub it's in the correct position and hasn't been removed and reinstalled incorrectly.

[prasannar2009]

Hello everyone,

Thanks for the tips!
- The new tyre is the exact same size specifications as the previous one.
- It's hard to say about the extra resistance when I try to spin the wheel on the centre stand. I do feel that there is a slight increase in resistance than before, but that could just be confirmation bias.
- The brake lever setting can also be ruled out. I checked that out.

So, it's probably the axle nut. I took it back to the place. (It's not the dealer, but a workshop that works with scooters/motorcycles). The man insists that it cannot be the axle nut. According to him, it can't be loosened any more from the current setting since that will cause the wheel to wobble. I'm thinking maybe I should double check the torque setting myself sometime? I do have a torque wrench. I was just a bit worried will I screw up the wheel alignment/balance? Do you think this requires a lot of skill?

Thanks!

[you you]

Hello everyone,

Thanks for the tips!
- The new tyre is the exact same size specifications as the previous one.
- It's hard to say about the extra resistance when I try to spin the wheel on the centre stand. I do feel that there is a slight increase in resistance than before, but that could just be confirmation bias.
- The brake lever setting can also be ruled out. I checked that out.

So, it's probably the axle nut. I took it back to the place. (It's not the dealer, but a workshop that works with scooters/motorcycles). The man insists that it cannot be the axle nut. According to him, it can't be loosened any more from the current setting since that will cause the wheel to wobble. I'm thinking maybe I should double check the torque setting myself sometime? I do have a torque wrench. I was just a bit worried will I screw up the wheel alignment/balance? Do you think this requires a lot of skill?

Thanks!

Re torquing won't affect alignment or balance.

[springer1]

I'm not 100% sure but I kind of feel a difference if I rotate the back wheel manually when the scooter is on its stand - a bit more resistance than before.

You’re not 100%sure - not being snarky but is it hard to spin or not? I thought mine will turn only 2 rotations or so that’s it due to the drive mechanism drag. Typically removing a wheel or tire has no impact on the torque against the bearings at all unless Honda assembled it wrong and the bearing nuts were not locked. Totally different nuts.

[Eiron]

Here's a diagram of the rear wheel parts and their orientations. I recently removed my rear wheel and there's really not a whole lot that can bugger up the re-installation other than getting the spacers out of order or in the wrong orientation (for example, part #3 could be turned around on the axle). You can pull the wheel off yourself and check that all of the spacers are correct. You have to remove the muffler first, and an impact wrench makes it easy to remove the big 22mm axle locknut. Here's one video showing how to do it, but look for other videos too.

[springer1]

I'm not 100% sure but I kind of feel a difference if I rotate the back wheel manually when the scooter is on its stand - a bit more resistance than before.

You’re not 100%sure - not being snarky but is it hard to spin or not? I thought mine will turn only 2 rotations or so that’s it due to the drive mechanism drag. Typically removing a wheel or tire has no impact on the torque against the bearings at all unless Honda assembled it wrong and the bearing nuts were not locked. Totally different nuts.

prasannar2009 - I read my above post and it seems a bit rough - sorry about that, no harm intended. But normally the nuts effecting the bearings can’t be moved unless you really try doing so. When I try to spin my PCX rear wheel with the scoot on the center stand, I get 1.5 turns - that’s all.

[prasannar2009]

Hi springer1, not sure if I quite get you. When I try to spin the rear wheel on the centre stand, I can hardly get one complete turn with a lot of force. What I meant by not being 100% sure was that, I have a feeling it was pretty much the same even before the tyre change. I don't think I could get much more than 1 turn. But I never really measured this consciously. So, I'm not very sure.

[springer1]

Hi springer1, not sure if I quite get you. When I try to spin the rear wheel on the centre stand, I can hardly get one complete turn with a lot of force. What I meant by not being 100% sure was that, I have a feeling it was pretty much the same even before the tyre change. I don't think I could get much more than 1 turn. But I never really measured this consciously. So, I'm not very sure.

OK understood thanks. I only get 1.5 turns with a very hard spin - and 1 turn with a good push. If others could reply with what they get when they spin their rear wheel get it would help get an average experience. But, it shouldn’t spin freely like a bicycle.

[prasannar2009]

I think I figured out what was causing the fuel economy drop. After checking the torque on the axle nut and other things suggested on this thread, everything seemed to be normal! But now I think I was mistakenly correlating the time of the tyre change the the fuel economy drop. Looking at my fuel data, I saw a more gradual decrease rather than a sudden one, and I now think it's due to the seasons!

We had a very above-average warm and dry summer here with temperatures >25 C for multiple months, and so I did quite a bit of long distance riding in the summer that gave me fuel economy values of 48+ km/L. And once the temperatures started to drop around September, I started riding more within the city and short distances. And last month or so has been close to freezing on most of the mornings. I think that caused the fuel economy to drop down to 42 km/L. We had a week of 'higher' temperatures recently around 13-15C. So I went on a couple of longer rides, and the fuel economy went back up to almost 46 km/L.

This makes me conclude that the fuel economy drop was merely due to air temperature drop. So, I have a thermometer in my PCX then

[you you]

I think I figured out what was causing the fuel economy drop. After checking the torque on the axle nut and other things suggested on this thread, everything seemed to be normal! But now I think I was mistakenly correlating the time of the tyre change the the fuel economy drop. Looking at my fuel data, I saw a more gradual decrease rather than a sudden one, and I now think it's due to the seasons!

We had a very above-average warm and dry summer here with temperatures >25 C for multiple months, and so I did quite a bit of long distance riding in the summer that gave me fuel economy values of 48+ km/L. And once the temperatures started to drop around September, I started riding more within the city and short distances. And last month or so has been close to freezing on most of the mornings. I think that caused the fuel economy to drop down to 42 km/L. We had a week of 'higher' temperatures recently around 13-15C. So I went on a couple of longer rides, and the fuel economy went back up to almost 46 km/L.

This makes me conclude that the fuel economy drop was merely due to air temperature drop. So, I have a thermometer in my PCX then

Hurray

[kramnala58]

I think I figured out what was causing the fuel economy drop. After checking the torque on the axle nut and other things suggested on this thread, everything seemed to be normal! But now I think I was mistakenly correlating the time of the tyre change the the fuel economy drop. Looking at my fuel data, I saw a more gradual decrease rather than a sudden one, and I now think it's due to the seasons!

We had a very above-average warm and dry summer here with temperatures >25 C for multiple months, and so I did quite a bit of long distance riding in the summer that gave me fuel economy values of 48+ km/L. And once the temperatures started to drop around September, I started riding more within the city and short distances. And last month or so has been close to freezing on most of the mornings. I think that caused the fuel economy to drop down to 42 km/L. We had a week of 'higher' temperatures recently around 13-15C. So I went on a couple of longer rides, and the fuel economy went back up to almost 46 km/L.

This makes me conclude that the fuel economy drop was merely due to air temperature drop. So, I have a thermometer in my PCX then

Temperature plays a huge roll in fuel consumption. As you summarize, combining that and the change in your riding habits (shorter trips vs. long trips) is like the cause of the reduced mileage.

I recall reading years ago that ideal mileage conditions are about 50 mph with 50°F temps at 1,200 ft altitude (80kmh, 10°C, 360 mtrs).