swapping to a larger chainring.

col230

I have an FSA comet crank with a 42t large chainring, could I swap out the chainring for something larger without having to change the derailleur, or messing up the set up? I use the bike mainly for commuting, so I want a bit more speed.

Chunkers1980

Pedal faster then?

Ouija

Can always increase chainring size but you'll need to move the derailleur further up the seat post and pull the shifting wire tight again. Also, if it's a multi ring chainset, you'd need to increase the relative size of all the other chainrings as most derailleurs can't handle very large difference between big ring and small ring.

The Rookie

41/11 will see you topping out at over 35mph, how much faster do you want to go....or are you not pedaling fast enough?

gt-arrowhead

The Beginner wrote:

41/11 will see you topping out at over 35mph, how much faster do you want to go....or are you not pedaling fast enough?

35mph is very accurate, thats the maximum i reached at 42/11 (reckon i could have got 1-2 more if i gave 100%). I spin out 42t quite often on my commute, it does get irritating.

Ive tried a Marin with 48t and i found it very sluggish really, probably because i wasnt used to it. I had to change gears quite frequently as i was pretty slow pulling off etc. The top speed was better obviously. So based on what ive experienced, id recommend going for something like a 46t up front.

As mentioned, the derailleur needs to come up, and the cable needs to be released and re-tentioned. Im not sure if you will have any problems with other parts of your drivetrain, like your mech. A step up of 4 teeth shouldnt create any problems really. But you probably will have to add a link or two to your chain.

col230

35 mph!? I must be a puny weakling! I'll have to count the teeth on the back, the fastest I can get out of the bike is about 21mph, that is flat out, thats with slicks, 26inch , this is an MTB I'm talking about!

cooldad

Pedal faster. A bigger chainring isn't going to help if you can't max out the one you have.

bennett_346

col230 wrote:

35 mph!? I must be a puny weakling! I'll have to count the teeth on the back, the fastest I can get out of the bike is about 21mph, that is flat out, thats with slicks, 26inch , this is an MTB I'm talking about!

21mph?! What the hell are you doing, freewheeling?

col230

I counted the rings on the back smallest is 12. 35mph! Are you kidding me? I ride every day, 15 miles, 7.5 in the morning, 7.5 in the evening, I run a 10k at least once a week in around 48 minutes, their is no way I'm out of shape, the most I have ever had out of my bike is 27Mph, going down hill, pedals spinning out, with the wind behind me.

supersonic

Your cadence must be quite low when gunning it - 42/12 at 120 pedal revs a minute is still about 30mph.

And you can't change to a larger ring wiithout replacing the other as the gap for the derailer is too much.

col230

I googled how fast cyclists are on the Tour de France, it says Lance holds the record averaging about 25 mph, and he was 8 miles high!

Chunkers1980

What's your point?

Track sprinters get closer to 50mph

cooldad

col230 wrote:

I googled how fast cyclists are on the Tour de France, it says Lance holds the record averaging about 25 mph, and he was 8 miles high!

Average is quite different to top speed. Think about it.

cooldad

But if you want to go really fast on the road, buy a road bike. Mine has 52/42 rings, and would go really fast, if I had bigger balls.

The Rookie

I can hit 26mph on the flat on my commuter (Hybrid frame, MTB finishing kit, 26" slicks), I regularly hit 35mph downhill (46/13) and have had a 45mph (scary!). I'm 46, fat and unfit enough to suffer fom low blood pressure!

At 27mph the pedals are not spinning out, you need to learn higher cadence (sorry, but it's true), a larger chainwheel isn't going to help you.

supersonic

col230 wrote:

I googled how fast cyclists are on the Tour de France, it says Lance holds the record averaging about 25 mph, and he was 8 miles high!

The best average is higher than that on the TdF for a stage. Lance's average you quote is for the whole race! And is an average, not a maximum.

gt-arrowhead

If you are only doing 27mph max then you need to pedal more! Its hard to believe that you only got 27 with slicks, downhill, pedals spinning, and the wind behind you. No way.

Ouija

col230 wrote:

35 mph!? I must be a puny weakling! I'll have to count the teeth on the back, the fastest I can get out of the bike is about 21mph, that is flat out, thats with slicks, 26inch , this is an MTB I'm talking about!

Ignore them. I run 48 teeth on two of my hybrids and the most i ever get out of those is around 27mph on a flat and about 24mph with a 44 tooth ring. Going down hill is a completely different thing of course. I've done over 50mph on a 44 tooth bike (Rosedale chimney down to Hutton Le Hole). And while there is some truth to the advice to pedal faster (edit: when going down hill)... why should you have to if you can get the same speed at a more relaxed cadence with a bigger ring?

cooldad

Physics and logic are presumably not your strongest attributes.

bennett_346

Ouija wrote:

col230 wrote:

35 mph!? I must be a puny weakling! I'll have to count the teeth on the back, the fastest I can get out of the bike is about 21mph, that is flat out, thats with slicks, 26inch , this is an MTB I'm talking about!

Ignore them. I run 48 teeth on two of my hybrids and the most i ever get out of those is around 27mph on a flat and about 24mph with a 44 tooth ring. Going down hill is a completely different thing of course. I've done over 50mph on a 44 tooth bike (Rosedale chimney down to Hutton Le Hole). And while there is some truth to the advice to pedal faster... why should you have to if you can get the same speed at a more relaxed cadence with a bigger ring?

You're pedalling at about half the RPM you should be... You make no sense. Would you drive everywhere in fourth gear in your car because the engine rpm is lower? No, you wouldn't because it's actually more taxing on the engine than a lower gear and higher RPM. Same with your body.

And what does the gradient have to do with it? Nothing at all. 48t = 48t.

The Rookie

Ouija wrote:

Ignore them. I run 48 teeth on two of my hybrids and the most i ever get out of those is around 27mph on a flat

Thus proving a 48t doesn't make you faster, power = speed, not gearing, and 26/27 is easily achievable with a 42T.

Ouija

The Beginner wrote:

Thus proving a 48t doesn't make you faster, power = speed, not gearing, and 26/27 is easily achievable with a 42T.

Only if you pedal like an idiot. Why bother? Just shift into a bigger ring and take it easy.

bennett_346

Nope. My big ring on the commuter is 42t and 28mph is perfectly achievable without spinning out.

supersonic

Most people are most efficient between cadences of 60-120 - I wouldn't say the latter was pedalling like an idiot lol, though is fast. Some riders can sustain even more.

If a larger ring is needed, I would get a new chainset, maybe a triple (if the front derailer and shifter are suitable, and it clears the chainring) ie a 48/38/28.

cooldad

Ouija wrote:

The Beginner wrote:

Thus proving a 48t doesn't make you faster, power = speed, not gearing, and 26/27 is easily achievable with a 42T.

Only if you pedal like an idiot. Why bother? Just shift into a bigger ring and take it easy.

Because if your legs aren't strong enough to manage it in an easier (lower) gear, they are unlikely to manage it in a higher gear. Plus grinding in a high gear is more likely to blow your knees up.

The Rookie

Plenty of testing that shows a human pedals most efficiently at 90-100rpm (watch the TdF), lower cadance may feel better but wears you out faster and kills your knees quicker, 120rpm isn't pedaling like an idiot, I have people I ride with who ride SS and they can spin at 160rpm....now that is pedaling like an idiot.