I upgraded my stock chainring on the ultra eagle to a 50t wolftooth and I like it so much that I am wondering if I should have just gone to 52t. Would I notice more top speed? I will probably leave it as is for now but later on or if it starts wearing out I may consider it for next time. I can do 30s (mph) pretty easy on a full battery but I wouldn't mind a couple more mph just for fun.
50t vs 52t chainring?
- Thread starter 330rcs
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What is your rear cog? You'll see more difference if you lower your rear cog 2t better than up'n your chain ring 2t. Example if your smallest cog is 13, go for 11 instead of going 52t chain ring.
This is my cassette: SRAM PG-1130 11-50T
Is that what you meant? Do I need to go lower on the 11-50t number? Like an 11-46t? Or 11-42t? Right now I have so much torque that I only use the top 4 or so gears.
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Sierratim
Well-Known Member
- Region
- USA
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- Nevada City, CA & Paradise Valley, AZ
The 11t cog controls your top speed. I believe that EVH5150 was thinking that if your smallest cog was say a 13t you could change out the cassette to get the 11t cog and pickup an extra gear for more speed, but you're all ready there. Changing to a 11-xxt cassette (where xx is less than 50) won't affect your top speed, just your max wheel torque for climbing.
One thought would be to go with a 52t chain ring (4% higher gear) and combine that with a cassette change to a 10-42t cassette like the Sram CS-XG-1175-A1. This additional 10% change in the smallest cog combined with the chain ring change will give you the equivalent of a full higher gear for more top speed, but loses your lowest hill climbing gears. BTW - Sunrace makes a 10-46t 11-speed cassette, but compatability with your other Sram components would need some research.
This Gear Calculator is helpful evaluating the impact of any gearing changes on your top speed. Input your tire size and gearing then for 'Gear Units' select 'MPH' at your most comfortable cadence. It will calculate your speed.
In this calc with a 650bx3 tire and a comfortable cadence of 60rpm the 52t ring and 10t cog combo is 3.3 mph faster than the 50t ring and 11t cog combo. YRMV depending on tire size and cadence.
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Awesome so with the setup I have now I just need to change the cassette to CS-XG-1175-A1 and to 52t chainring and that's it? I won't need to change my shifter or derailer or anything else?
I don't use my lowest gear as it is infact it's been dangerous. I am more cautious about not going too low now but when I first got my bike it wheelied on me and the seat has rammed me a few times from being in too low of a gear and hitting the throttle while getting on the bike. I definitely am not concerned about losing my lowest gear!
Just out of curiosity if I will be getting an extra 10% top speed does that mean if say I can pedal comfortably and achieve 25 mph now with my current setup would 10% increase mean that I gain 2.5 mph with the same effort?
Appreciate it! I'm going to try this upgrade when I wear out my chainring or cassette.
Sierratim
Well-Known Member
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- USA
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- Nevada City, CA & Paradise Valley, AZ
You will most likely need to adjust your chain length going from a 50t x 50 setup to a 52t x 42. This Chain length Calculator can help predict this. You'll need to input your bike's actual chain stay length and the gearing setups to get the length calculations you need. Going with the Sram 10-42t cassette should avoid any other compatibility problems with your other drive train components.
The gearing change I've outlined is more than a 10% change, it's right at 14%. This will yield a proportional increase in top speed (26.6mph - 23.3 mph)/23.3mph = 14.1% at the same cadence. This isn't the same as saying you can get this 14% increase in speed "at the same effort". It will take more power (effort) to drive the bike faster due to wind resistance and other smaller affects. If your bike motor has excess power then it can provide the needed watts. Otherwise, you, as the rider, will need to add the extra power required at the faster speeds.
Ride On!...and good luck with your upgrade...
Sierratim
Well-Known Member
- Region
- USA
- City
- Nevada City, CA & Paradise Valley, AZ
As they say, Just One More Thing...You will most likely need to adjust your chain length going from a 50t x 50 setup to a 52t x 42. This Chain length Calculator can help predict this. You'll need to input your bike's actual chain stay length and the gearing setups to get the length calculations you need. Going with the Sram 10-42t cassette should avoid any other compatibility problems with your other drive train components.
The gearing change I've outlined is more than a 10% change, it's right at 14%. This will yield a proportional increase in top speed (26.6mph - 23.3 mph)/23.3mph = 14.1% at the same cadence. This isn't the same as saying you can get this 14% increase in speed "at the same effort". It will take more power (effort) to drive the bike faster due to wind resistance and other smaller affects. If your bike motor has excess power then it can provide the needed watts. Otherwise, you, as the rider, will need to add the extra power required at the faster speeds.
Ride On!...and good luck with your upgrade...
This Is a fun Wind Resistance calculator for cyclists. For a 180lb rider at 23.3mph on flat ground and no wind it predicts a power requirement of 149 watts. At 26.6mph it's at 221 watts; a surprising 72 watt/48% increase in power to drive the bike 14% faster. So even though the rider is still pedaling at the same 60rpm cadence, the power (effort) required to go 14% faster increases by 48% - has to do with wind pressure being proportional to the square of the wind speed...
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Sorry I wasnt thorough with explanation. I was just quickly answering your question if you should go up 2t on your chainring.
Sierratim pretty much summed it up. Bottom line if top speed is what your after, your maximum gear should be the smallest cog and the biggest chainring your bike will allow.
My max gear set up is 60x11. I didnt chose it for max speed but rather to lower my cadence. I didn't want to spinning my brains to cruise at higher speed. But its there if I really feel like gunning it. On top of that I chose longer crankarms (175's) too. Shifter are the same, added extra links to my chain.
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Clark Gryphyn
New Member
Wind resistance is no joke. I normally ride around at 30% juice and can comfortably ride in the 20 to 25 mph range. At 50% juice I can comfortably ride around 30 mph. But wind resistance really comes into play about then and I get diminishing returns. I can go 40 mph if I'm at 100% juice, but it sucks the battery down. I often wonder how fast I could go if I were wearing spandex. 
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