Need advise for changing front cog

[novetan]

I'm using a Tern Verge S11i, front cog 46T with rear cog Shimano Alfine 11 speed (9T to 34T). Most of the time I'm using between 8 and 9 gear and my av. cadence is 80. I felt its about time that I need a bigger cog to give my lung a lower heart beat.

Would you recommend a front cog 50T or 52/53T? Would jumping to 52T or 53T too great a difference from my present one?

 

[TheDoctor]

Failing to see the problem here.
If 8 or 9 is too low, then what's wrong with 10 or 11?

 

[novetan]

Failing to see the problem here.
If 8 or 9 is too low, then what's wrong with 10 or 11?

Tks for reply.

The general belief (not sure whether using right word after I chance upon below article) was that we have to emulate the pro which generally produce 80 to 100 rpm and goes into extreme drive mode of 120 rpm in TT. So if I pedal at 80 rpm and complaining about not getting fast enough, I'd have recieve advise to peddle faster. This is contrary to below article and I sum up as:

We have to mirror our cadence according to our power output. I'm small build and mere mortals and at most generate 150W unlike those pro which goes as high as 400W to 500W. In the article, I was advised to use 60 rpm with my 150W output. Any faster cadence doesn't help and will in fact drain off my energy.

http://www.pponline.co.uk/encyc/cycling-training-can-your-pedalling-technique-make-you-a-more-efficient-rider-42241

Although I use mainly gear 8 and 9, I still have 10 and 11 gear as reserve. When I switch to either 10 or 11, I find its extremely taxing on my leg which I realised I don't have the muscle to peddle faster than my current 80rpm on 8 or 9 gear.

So my question is:
1) Will changing from my current 46T/11T to say 52T/11T much easier on my leg than 46T/9T (which is gear 11)
2) My cadence 46T/9T is abt 48 rpm. I like to give that article a try to reach a cadence of 60. Hence toying with the ideal of changing the front cog.

Appreciate any good advise instead of simply throwing away good money.

 

[RecordAceFromNew]

Tks for reply.

The general belief (not sure whether using right word after I chance upon below article) was that we have to emulate the pro which generally produce 80 to 100 rpm and goes into extreme drive mode of 120 rpm in TT. So if I pedal at 80 rpm and complaining about not getting fast enough, I'd have recieve advise to peddle faster. This is contrary to below article and I sum up as:

We have to mirror our cadence according to our power output. I'm small build and mere mortals and at most generate 150W unlike those pro which goes as high as 400W to 500W. In the article, I was advised to use 60 rpm with my 150W output. Any faster cadence doesn't help and will in fact drain off my energy.

http://www.pponline.co.uk/encyc/cycling-training-can-your-pedalling-technique-make-you-a-more-efficient-rider-42241

Although I use mainly gear 8 and 9, I still have 10 and 11 gear as reserve. When I switch to either 10 or 11, I find its extremely taxing on my leg which I realised I don't have the muscle to peddle faster than my current 80rpm on 8 or 9 gear.

So my question is:
1) Will changing from my current 46T/11T to say 52T/11T much easier on my leg than 46T/9T (which is gear 11)
2) My cadence 46T/9T is abt 48 rpm. I like to give that article a try to reach a cadence of 60. Hence toying with the ideal of changing the front cog.

Appreciate any good advise instead of simply throwing away good money.

If your cadence at 46T/9T is 48rpm, then given the Tern has 406-42 tyres, you would only be travelling at about 13mph according to this, when you are generating roughly 70W according to this.

What you need to understand is the larger the front chainring and/or the smaller the rear (effective) sprocket the higher the gear. For a given power output the higher the gear the less rpm you can pedal because the resistance (air, friction etc.) increases with bike speed until it matches the power you can generate. If just by having higher gear (e.g. larger chainring) means we can be quicker for the same effort (power) we will all have chainrings bigger than our wheels!

So what that means is if you are only able to achieve 48rpm with 46T/9T, you are likely to be able to achieve 60rpm with 46T/11T delivering roughly the same road speed (and combating roughly the same wind/road/mechanical resistance). What you will find is if you change the 46T to a 52T you will need to be on an even lower gear (e.g. 12T or 13T) at the back to maintain 60rpm - so there is hardly any point for the change.

What that paper says (based on just this paper in 2000 it appears) is people at different level of fitness do have different optimal pedalling rpm. Subsequent research has opened up the issue of what optimal means exactly because it can mean energy conservation, comfort, max power delivery etc. etc. For a more recent review see this.

 

[TheDoctor]

Indeed.
If you don't have the power to turn a high gear, then it doesn't matter how you achieve that high gear, as you still won't be able to turn it!! Unless and until you're spinning out in top, there's no point fitting a bigger chainring.

 

[novetan]

Thanks guys for your explanation. Seems like I have to be on my training shorts for quite a fair bit of time. Save me the money with your explanation.