MXUS XF15 rear hub what size chainring for my bike?

[Laissez]

Now it feels like I have pedal like mad man because not high enough gear when speeding up to and over 40km/h/25mp/h. My motor is rear hub mxus xf15 with 48V battery.

My bike has now:
tires 28x2.00” (ETRTO 50x622)
1x8 drivetrain (prowheel 38t front, Shimano CS-HG31-8 11-34t rear)
no suspension

 

[markz]

Then you need a 9 or 10 small gear rear with a 44 front gear or higher, depending on what the calculators say. Not sure if those small gears come in 8S cassette, I see lots of 11 speed small rear gear, if so then just get a bigger crank gear.


There are lots of calculators out there
https://sheldonbrown.com/gear-calc.html

 

[Laissez]

Then you need a 9 or 10 small gear rear with a 44 front gear or higher, depending on what the calculators say. Not sure if those small gears come in 8S cassette, I see lots of 11 speed small rear gear, if so then just get a bigger crank gear.


There are lots of calculators out there
https://sheldonbrown.com/gear-calc.html

Yeah 11 is the smallest for SHIMANO CS-HG 31. So I'll go for larger front chainring.

 

[markz]

Yeah but then you lose the high (?or is it low?) climbing gear ratio's. Thats why I like 3x8 bicycles even though us ebikers dont use a lot of gears to begin with but I like a 22x36 to help the motor out climbing, or 48x11 for cruising along.

Yeah 11 is the smallest for SHIMANO CS-HG 31. So I'll go for larger front chainring.

 

[Laissez]

Yeah but then you lose the high (?or is it low?) climbing gear ratio's. Thats why I like 3x8 bicycles even though us ebikers dont use a lot of gears to begin with but I like a 22x36 to help the motor out climbing, or 48x11 for cruising along.

Climbing is not problem for me now even with 11x38 ratio gear or there aren't steep enough hills here. My motor is geared rear hub motor so it doesn't depend on my bike's drivetrain.

 

[markz]

But you either want to pedal or not. Majority of people like pedal assist, the rest are on throttle only (no pas) and either choose to pedal or not.

Use the cadence calculators for figure out what gear to buy for the crank.

Climbing is not problem for me now even with 11x38 ratio gear or there aren't steep enough hills here. My motor is geared rear hub motor so it doesn't depend on my bike's drivetrain.

 

[Laissez]

But you either want to pedal or not. Majority of people like pedal assist, the rest are on throttle only (no pas) and either choose to pedal or not.

Use the cadence calculators for figure out what gear to buy for the crank.

I have both PAS and throttle and I use them both. I pedal also while using throttle.

 

[dogman dan]

Would help if you showed a closer picture of the chainring side of the bike. See if there is clearance for bigger ring.

Very hard sometimes, to fit a 52 tooth on bikes that are not racing road bikes. But you might be able to get a 48 tooth crank from an MTB and fit it on the bike. You'd have to of course, match the type of crank you have on the bike.

The problem with 52 t is it may rub the frame. With an MTB crank, it may still fit a 48, with a little help from the chain ring being a bit more offset on the mtb's.

52 is nice, enabling pedaling to at least 25 mph, with fast but not uncomfortable cadence. But with 11 in back instead of 14, a 48t will be about the same.

 

[Laissez]

Would help if you showed a closer picture of the chainring side of the bike. See if there is clearance for bigger ring.

Very hard sometimes, to fit a 52 tooth on bikes that are not racing road bikes. But you might be able to get a 48 tooth crank from an MTB and fit it on the bike. You'd have to of course, match the type of crank you have on the bike.

The problem with 52 t is it may rub the frame. With an MTB crank, it may still fit a 48, with a little help from the chain ring being a bit more offset on the mtb's.

52 is nice, enabling pedaling to at least 25 mph, with fast but not uncomfortable cadence. But with 11 in back instead of 14, a 48t will be about the same.

Ah, sorry for not having the picture of it. I heard you could offset this 4 bolt one a bit with spacers to fit larger chainring. I think 48t would at least fit my bike.

 

[markz]

The picture is still not clear, the chain stay frame from the bottom bracket to the rear dropout is of concern because of the teeth of the crank gear could hit the chain stay. Another option might be to get a longer bb axle to bring the crank out, but then your chain line changes to.

 

[Tommm]

I have simple freewheel rear (16t) and 42t cog front, it is alright to 38-40. For higher speed 44t or 46t front would be better.

 

[Laissez]

The picture is still not clear, the chain stay frame from the bottom bracket to the rear dropout is of concern because of the teeth of the crank gear could hit the chain stay. Another option might be to get a longer bb axle to bring the crank out, but then your chain line changes to.

Clipboard02.jpg

I have simple freewheel rear (16t) and 42t cog front, it is alright to 38-40. For higher speed 44t or 46t front would be better.

Yep it's tight call, I might try 44-48t first. I thing I can fit something in between of those.

 

[dogman dan]

Ohhh,,, thats looking real tight in the picture. Definitely no 52 tooth. If you really want to pedal at 25 mph, you are looking for a new bike.

 

[Chalo]

Ah, sorry for not having the picture of it. I heard you could offset this 4 bolt one a bit with spacers to fit larger chainring. I think 48t would at least fit my bike.

You can put a larger ring in the outer position, where the chainguard is now, than in the middle portion where your 38T ring is. I'd keep the 38t and add a front derailleur. 52-38 should work well with a normal road double front derailleur.

 

[dogman dan]

Yeah, enough offset would make any size work. But it might be a lot of offset. Enough to make running the bigger gears in back a problem? It just looked to me like even a 48t might be a problem. You can get a very inexpensive used MTB crank set in square taper on e bay, and just see if it fits, if that bike is square taper.

I was hoping to see more room in there before the frame got wider, enough for at least a 48t front ring without big offset.

Running without a derailleur is quite possible too, if shifting to the low gear is very seldom needed.

 

[Laissez]

Yeah, enough offset would make any size work. But it might be a lot of offset. Enough to make running the bigger gears in back a problem? It just looked to me like even a 48t might be a problem. You can get a very inexpensive used MTB crank set in square taper on e bay, and just see if it fits, if that bike is square taper.

I was hoping to see more room in there before the frame got wider, enough for at least a 48t front ring without big offset.

Running without a derailleur is quite possible too, if shifting to the low gear is very seldom needed.

With coupons I got 48t narrow wide chainring from AliExpress just for 10 dollars. So cheap way to try out if it's ok or no.

 

[999zip999]

I have a 52t 11t and peddle at 28mph . I needed a wider BB to clear. Plus put a hammer to the comoly frame for more Clarence.

 

[Chalo]

I needed a wider BB to clear. Plus put a hammer to the comoly frame for more Clarence.

 

[999zip999]

I'm a silversmith and goldsmith and have 25 to 30 hammers. Even one I made in 7th grade. Hammer's !

 

[999zip999]

I'm a silversmith and goldsmith and have 25 to 30 hammers. Even one I made in 7th grade. Hammer's !