sendgridover

Hi guys - it's my first post so please go easy on me.

OK, 55 year old guy in Sandhurst England who enjoys getting out on his bikes, I have a Giant CRS3 for general road and tow path use and a 12 year old Scott Vail for when I want a bit of off road fun. Just so that you are aware, Sandhurst is in the Blackwater Valley so there are some excellent flat roads, but lots of steep hills up the valley sides.

It's the Giant though where my question lies. This is a stock, off the shelf bike, with Shimano M151 crankset (28/38/48) and SRAM PG380 11-28 Cassette. The bottom end gearing is fine but I am looking to increase the top end gearing to bring it more in line with a road bike (rather than buying another bike which would not go down well believe me), so my question therefore is whether to change the crankset or the cassette?

Clearly I am not looking to spend big money on this because I may as well buy a second hand road bike, so any suggestions would be appreciated.

Thanks

Ian

stapfam

11/28 cassette and you will not get a higher gear than the 11t. so change of cassette will not help much.

28/38/48 chainrings though and you may not even have to change the crankset. Just the big ring to a 50t. That may take some looking for the bolt diameter that the M151 has fitted but After Market manufacturers will have one somewhere

And not too far from you over in Eastbourne so we might meet up sometime.

And welcome to the asylum.

tsl

I'm interested to know what the goal is that you're trying to achieve.

A standard road triple is only 52/39/30, newer ones 50/39/30. We're talking a only couple of teeth. Same on the rear where 12-27 is pretty much standard.

Having once owned a Giant hybrid similar as yours, I can say from experience, higher gears won't make that bike faster. Even work on the engine will have only a marginal impact.

However, one thing that made riding my Giant much more pleasant was that I switched from a wide-range cassette to a close-ratio one. At my typical speeds, I was forever hunting between one gear and the next, with one being too easy and the next being too hard. I found I was using only five of the eight on the back, so I got a cassette whose range was the same as those five I was using, but gave me eight choices in that same range.

I gave up the two lowest gears, but I didn't climb trees with that bike anyway. I also gave up the very top gear, but I'm not a Tour de France rider. I had to granny down a bit more often, but that's what the 28 ring is there for. At cruising speeds, however, the smaller jumps between the gears made things much more pleasant, as minor changes in grade or winds could be compensated for with correspondingly minor changes in gearing.

Now, if you're looking for snappy acceleration, and a drivetrain that moves a bike with alacrity and verve, the save your money for a road bike. After the first 100 yards on my first road bike, (second-hand, seven years old) my entire being just said, "Whoa!" When I pushed the pedals, Things Happened. And quickly.

I never went back. I own four of the blasted things now. And I have close-ratio cassettes on every one.

cyclinfool

Both previous posts have given you all you need - no more to add.

sendgridover

Thanks chaps, I suppose I need to go back to basics and ask myself the question - what is it you really want ?

Cycling came back to me about two years ago after a 50km charity ride that I did on an old shed of a bike that weighed a ton. Strangely enough I actually enjoyed it, and I guess I had been looking for something that would get me off my backside and out doing a bit of excercise, because 15 years ago when I came out of the army, I was as fit as a butchers dog.

So, one mad day I went down to our local bike shop and spoke to the nice people and told them my story. I was really unclear as to what it was I wanted, but knew that it couldn't cost the earth so I ended up with the Crs3. Great, I loved it and still do, as there is hardly a mark on it even now. I started going out on a Saturday doing a little 10 mile circuit, which was reasonably flat and slowly moved out into areas where there are more hills and the round trip is now about 20 miles. One particular hill I can only climb in bottom gear. So, is different gearing going to make me go faster, well the physics say so, but so what, just means I would get home quicker - do I like going fast down hill? well yes, but it can be scary especially when the road surface is not so good. I do like the sound of closer gearing though, because I find myself constantly up and down gears as the incline or wind changes.

I had the opportunity of a very cheap second hand Scott mountain bike last year so I jumped at it. I love it being out with my two son in laws across the trails of Long Valley Aldershot and up to the top of Ceasars Fort (which is a very long cross country climb).

Sorry, I am waffling on a bit now - I guess I have sort of settled into a routine but mainly use the weekends to be out on the bike for the purpose mainly of excersise, but also of enjoyment.

Yes I would love a road bike, but at 55 and 15 stone plus, I am not exactly Alberto Contador.

Thanks chaps

Ian

DnvrFox

WRONG!!

I am 70+ and ride a road bike, and I weigh about 209 lbs. We have folks in this forum in their mid to late 70's riding road bikes. I ride about 125-150 miles per week. Others more.

Don't paint yourself in a corner on this issue.

cyclinfool

What he said!

BTW - no one here is Alberto Contador, we have a few who think they are and a few who make claims as it they are but we all know the truth.
So don't feel like you are not good enough for that road bike, the bike should never be the limiting factor - the real question is whether or not the bike is good enough for you!

Pat

I will pretty much repeat what the others have said. On the rear cluster, you are not going to get anything smaller than an 11 tooth cog. There is no way to get a higher gear that way.

On the chain rings, you can probably swap out the 48 big ring for a 50 or 52 big ring. But even that is only an 8% increase.

The probelm you are probably having is that you do not know how to "spin". Going fast in cycling requires being able to maintain high RPMs. Some people like pushing big gears at relatively low RPMS. I think that Gregg Lemond ran RPMs in the high 80s. Other cyclists spin and often run a bit over 100 RPM. In a sprint, one can hit over 150 rpm.

Your top gear is 118 chain inches. That comes out to a speed of 35 mph at a 100 rpm. It is still over 27 mph at 90 rpm. I have a feeling that your RPM is probably at 80 rpm or even lower.

You could get a bike computer with an RPM output and work on your spin. Being able to maintain higher RPMs is pretty much the only way you are going to increase your top end.

billydonn

It's settled then: N+1 is the only answer.

Retro Grouch 

Actually, I disagree. I think he should work on the motor. Two possibilities:

If you are not in your 48/11 a lot, you would benefit from building your muscular strength.
If you are in your 48/11 and spinning out a lot, you will benefit from increasing your cadence.

Speedo

You're already there.

A typical road bike high gear would be 52 in the front 12 in the back. That's a gear ratio of 4.333. Your bike has a 48 in the front and 11 in the back. That's a gear ratio of 4.364. Assuming equal wheels/tires you've got a slightly bigger gear with your 48/11.

Speedo

sendgridover

Doh - I should have worked that one out myself speedo me being an engineer. So given that the ratios are all but equal and the wheel diameter is the same (700c), there can other than friction, be only one other factor, speed of rotation.

BluesDawg

You already have a taller top gear than I have on any of my road bikes. If you can spin 100 rpm in that gear and still want more, by all means, get yourself a 53 ring. But I'm thinking you need to work on the motor and the spinning mechanics to get the most out of the gearing you have. Another factor may be wind resistance. It is pretty hard to push a bike to 30 mph while sitting upright. Drop bars would help with that.

sendgridover

Wind resistance is a significant factor when you are my shape. I have the aerodynamic features of a hippo

fietsbob

You need a Motor pace to use that 118" gear as is.

have a similar sized friend, with a Moped, to ride in front of you?

I'd say, at 15 stone you should plummet down hill quite well , even without pedaling.

badamsjr

When I wanted higher top speed, I tried higher gears, and a lighter bike. NO HELP! It took a while, but I came to the same conclusion as these posters--work on the motor. Maintaining a higher cadence takes some work. Your aerobic efficiency will build up slowly, as you practice it. A few times a month, go out with the express purpose of "spinning". Ride at a cadence as high as you can maintain, without bouncing on the saddle. Do a few 'intervals' of this with rest of a couple minutes between 'spins', and sooner than you might think, you will be able to maintain a higher cadence for extended periods. Now if you want to go 'harder', the real fun begins! Now we are talking low rpm 'grunt' work. You can decide for yourself if these will work for YOU.

stapfam

Easy way top check your cadence. Count how many full revolutions the crank does in 15 Seconds and multiply X 4. It will only give an indication of what you are at but good enough.

If Cadence is below 80 then try to get it up to that. If it is more than 100- then why are you worrying. I like to ride at 90 to 95 but on hills I will slow to 80 or even less. And don't dismiss the road bike. I only went road 4 years ago after 16years of MTB's But if you realise that the South Downs are only 6 miles from where I live- Then you can see why I went Mountain Biking. Road bikes are different and do take some getting used to but on the road- they are the best bike. Check out the Giant Defy3 to see what is available at a cheap(er) price.

cranky old dude

Unless money is an acutely limiting factor I see no reason why you can't work on both the bike and the engine. I found I was spinning out on long (1/2 mile) gentle downhills at speeds bearly breaking 30 mph.

I feel that I got immediate results by increasing the size of my middle and outer chainrings, and I'm now improving on those results by learning to spin faster and more efficiently.