Chainset change

[Chislenko]

I have 52-11 on my triple, can someone work out what speed someone who is a lot younger and fitter than I am attain because I feel sure I am never gonna find out 🙂

 

[Sharky]

I have 52-11 on my triple, can someone work out what speed someone who is a lot younger and fitter than I am attain because I feel sure I am never gonna find out 🙂

That's a 120"+ gear.

A young Chis Boardman, riding a 110" fixed gear returned comp record for 25 miles of 45 mins 57 secs. If only he'd listened to advice and ridden a 120"gear, he would have got under 40 minutes!

 

[Ajax Bay]

can someone work out what speed

Sure, in miles per hour = 0.0373 times wheel/tyre circumference (in metres) times cadence (rpm) times [number of teeth on large chainring] divided by [number of teeth on smallest sprocket].

set up: https://www.gear-calculator.com/?GR...20,23,28&UF=2170&TF=90&SL=2.6&UN=KMH&DV=teeth​

Put the tyre size in and it'll 'tell' you the estimated overall wheel circumference.​

 

[davidphilips]

Is that calculation relative to a 42t or 48t ch/ring?

Just to be clear I am stickiing with my 12-28t

I just used the cadence chart and used the 42 big ring input 700 wheel and forget the tyre size i guessed, but princable is the same a change of one tooth on the cassette makes a larger difference than one tooth on your front chain rings.
If you do go from a 42 chain ring to a 49 or a 48 chances are you may need new front and rear derailleurs chain and even a different chain set?

Know its easy to think a change to gearing, wheels, more expensive bike, whatever will make you faster but the truth is with in reason any bike that is the right size for you and set up correctly can be great fun , used for training, commuting or club cycle runs.

Want to really see an improvement in your speed, start training, rather than concerning yourself with gearing, concern more on cadence, with your present gearing if you sprinted at 120 cadence you would be doing about 33mph, i use a sightly lower gearing on my single speed bike and apart from fast club runs with the A group its more than high enough.

Just enjoy your bike and cycling, if you are really determined to cycle faster then you need to start to invest your time and effort in a training programme, when cycling you are the engine and an improvement in the engine will produce far better results than any gain by trying to improve your bike.

 

[Jameshow]

To give you a little more insight to speeds...

In the world of time trialling a 20 mph ride, either 10 miles or 25 miles, will be achieved by probably 99% of riders by the end of their first season.

But those achieving a 25mph ride in their first season is a very very low %. In my case, in over 500 timetrials, spanning over 50 years have only ever beaten 25 mph once. But at the tender age of 72, can still do a 10 mile TT at 20mph.

So you can see aspirations to increase speed from 20 to 25mph, will require gigantic effort.

Simple just find a 25mile long hill......!!!

 

[Dadam]

Maybe the OP just has a few short sections he's spinning out on and wants a couple more mph on, rather than trying to average 25 over mile after mile on a time trial. As a relative n00b myself with a flat bar hybrid, who's only just getting my head around gear ratios, I relate to this.

 

[Chislenko]

That's a 120"+ gear.

A young Chis Boardman, riding a 110" fixed gear returned comp record for 25 miles of 45 mins 57 secs. If only he'd listened to advice and ridden a 120"gear, he would have got under 40 minutes!

Next time I see Chris Boardman (from our area) I will go the other way then 😟😟

I came across him a couple of years back and rode with him for about a minute then gave up!

 

[Ajax Bay]

Amazon product ASIN B01HI6HARYView: https://www.amazon.co.uk/gp/product/B01HI6HARY/ref=ask_ql_qh_dp_hza

This chainset is 48-38-28 and needs a 122.5mm BB spindle (which I think the OP has, but needs to measure). £30

 

[notmyrealnamebutclose]

Maybe the OP just has a few short sections he's spinning out on and wants a couple more mph on, rather than trying to average 25 over mile after mile on a time trial. As a relative n00b myself with a flat bar hybrid, who's only just getting my head around gear ratios, I relate to this.

Yep, pretty much spot on. I average about 15 usually. Just like to be out in the fresh air enjoying the freedom
Then short burst of flat out when I'm in the mood and the wind permits. Just wanted to casually know what I
could expect from a larger ring, oh that sounds rude haha. I just want to lose the triple with a twin. All hail the
naysayers trying to shoot you down in flames, how dare a n00b question their reasoning. A vast majority are polite and give you their advice with good intentions and one or two may even encourage you.

TIL: 5mph simply cannot be done with just six extra teeth

 

[Peter Salt]

I just want to lose the triple with a twin.

If that's your motivation than you should make it clear in the original post. You were attempting to back it up with some sort of mechanical/mathematical reasoning that simply isn't there. People on here haven't questioned your desire but said motivation - primarily because they have a far greater understanding of the subject and recognised your motives as questionable, to say the least.

If you spin at 90RPM than that's 1.5 revolution per second (90/60). Then, calculate the top gear ratio, so for 42-12 it's 3.5, for 48-12 it's 4.0 (you divide the number of teeth on the front by the number of teeth in the back). Multiply your crank revs per second and the ratio - that's the revolutions of your rear wheel per second - 5.25 (42-12), 6.0 (48-12). If you're using a 700c wheel, the circumference of that is about 2.1m. Multiply the wheel revs and circumference - voila - you've got your rear wheel velocity. 11.025 m/s (42-12), 12.6 m/s (48-12). That should be all the guidance you need to work out any combination out yourself.

TLDR:

At 90RPM
42-12 = 24.8 mph
48-12 = 28.4 mph

At 95RPM
42-11 = 28.6 mph - not to mention a lot less fuss.

Or you can carry on being unpragmatic. Whatever.

 

[Chislenko]

Just a question for the OP.

(Not trying to be superior or condescending)

Why do you want to dump the triple? As someone who has bikes with triple and compact double I can see the pros and cons of both.

I actually prefer going out on my triple (winter bike). I just think it gives me more options depending on how I am feeling on the day. If the hills are "biting" I have the option of the 30, if I am just on a scenic ride I can sit in the 42 middle and pedal leisurely all day or if feeling good I can go into the 52 and have a blast.

When I compare to a compact I tend to sit in the 50 all day and use the rear cassette for change of effort etc. I am sure there are a lot of cyclists with a compact 50-34 who rarely use the 34.

I suppose my last statement could sum up the rise in popularity of the single front chainset / larger rear cassette bikes.

 

[Ajax Bay]

I want to go faster. I now have a 12-28 7sp cassette new shimano IG51 116 links. Has a triple crank T42-34- ? (never used it no interest) Hybrid I would really like just a 2x chainring set with either a T48 or T46.

there is slight play in the bb so thought would be a good time to replace the chain set that
I'm not that happy with atst. . . . . it's the gearing that's the main problem

Just to be clear I am stickiing with my 12-28t

I just want to lose the triple with a twin. All hail the naysayers trying to shoot you down in flames, how dare a n00b question their reasoning.

All good. Well just get on with it then.
To get that extra margin so you don't spin out with the wind behind you, I'd go to a compact (50-34). Your FD (triple type) will achieve shifting satisfactorily and as @C R has said your LH thumb lever will pull the cable.
Likely the new chainset will need a shorter BB spindle (this one needs a 110mm) to get the chainline right (and ensure the FD cage can reach). You will need a new chain as your large/large is 8 teeth more.
Moving from a 42t to a 50t ring would get you 19% more speed at the same/your highest achievable cadence.

 

[faster]

All good. Well just get on with it then.
To get that extra margin so you don't spin out with the wind behind you, I'd go to a compact (50-34). Your FD (triple type) will achieve shifting satisfactorily and as @C R has said your LH thumb lever will pull the cable.
Likely the new chainset will need a shorter BB spindle (this one needs a 110mm) to get the chainline right (and ensure the FD cage can reach). You will need a new chain as your large/large is 8 teeth more.
Moving from a 42t to a 50t ring would get you 19% more speed at the same/your highest achievable cadence.

I've not read through the thread in great detail, but just in case anyone else hasn't mentioned it...

As this is an MTB orientated bike, there is a good chance it will be impossible to fit a 50t chainring due to there not being enough clearance between the chainring and the chainstay.

Worth checking before you buy anything.

 

[Ajax Bay]

As this is an MTB orientated bike, there is a good chance it will be impossible to fit a 50t chainring due to there not being enough clearance between the chainring and the chainstay.

Good point, mitigated by the fact that the OP "wants to lose the triple with a twin (sic)" so the chainstay won't be in the way of the 50t ring - possibly the 34t (of a compact). The current middle ring (32t?) is about 3mm further out than an inner of a compact (34t). Checking the clearance now will give an idea whether it'd be an issue. A chainring radius increases by 2mm for each extra tooth (12.7/2pi).
A mitigation could be to use a 113mm spindle BB (vice a 110mm) to shift the chainline at the chainset end: the FD will have the reach needed.

 

[faster]

I don't understand why going from a triple to a double mitigates this risk, or why the 34t would be the problem.

The whole idea of going from an mtb to a road crankset is a massive minefield. Road and mtb cranksets are a very different shape, with road cranksets not being designed to accommodate the wider chainstays usually found on mtbs. You might find that it's impossible to get a satisfactory chainline and not have the cranks hit the chainstay.

I'd also doubt that a front derailleur designed to work with a 42t would shift well with a 50t.