New chain ring(s) for a 2005 Hardrock Sport

Londonscottish

Hi All,

I've just replaced the cassette and chain on my 2005 Hardrock Sport and would now like to fit a new chainring/chainrings.

TBH I'd be happy to just fit a new (larger) outer chainring to increase the gearing a bit.

The crankset is a TruVativ X-Flow fitted with 22/32/42 teeth.

If I wanted to order just a slightly larger outer chainring do I need to buy a TruVativ or are there pattern parts?

Anything else I need to be aware of?

Thanks

cooldad

As long as the BCD (bolt centre diameter) is the same any should fit but might need a touch of filing.
You might need to move the front mech a bit - make sure you can.
Make sure your rear mech has sufficient capacity for the new ring(s).

A couple of teeth shouldn't make much difference though.

Londonscottish

cooldad wrote:

As long as the BCD (bolt centre diameter) is the same any should fit but might need a touch of filing.
You might need to move the front mech a bit - make sure you can.
Make sure your rear mech has sufficient capacity for the new ring(s).

A couple of teeth shouldn't make much difference though.

Thanks CD - so assuming the BCD is 104 this might fit;

http://www.bikegoo.co.uk/product.php/61 ... 3594404ec7

Or this;

http://www.bikegoo.co.uk/product.php/10 ... 48t_4_bolt

I guess the other question is what % change in gearing it would make to go from 42 to 44 or from 42 to 48 teeth.

cooldad

Yes but 48 might be a bit of a jump from the 32 middle.

You can work out the proportion, or google gearing calculator.

http://sheldonbrown.com/gears/

http://www.bikecalc.com/gear_ratios

Londonscottish

cooldad wrote:

Yes but 48 might be a bit of a jump from the 32 middle.

You can work out the proportion, or google gearing calculator.

http://sheldonbrown.com/gears/

http://www.bikecalc.com/gear_ratios

Thanks for that.

I'm not too concerned about the jump from the middle chain wheel as it's a city bike and as such I'll only ever use the top ring.

So buy my calculations the 44 tooth ring gives me +6% in gearing

A 46 (if it existed) would give me +9%

And the 48 gives + 14%

The Rookie

How fast are you going - in a city - that you need a larger chainring?

At the right cadance you can do easily over 20mph.

If you want to go to a 48 (too big IMHO) you need trekking ratios throughout (28,38,48).

Londonscottish

The Rookie wrote:

How fast are you going - in a city - that you need a larger chainring?

At the right cadance you can do easily over 20mph.

If you want to go to a 48 (too big IMHO) you need trekking ratios throughout (28,38,48).

I'm not going very fast at all! I set off from my house, hook it up 1,2,3 gears, turn right down a slight incline and my legs are spinning out in top. Feels like it's got comedy gearing, tbh.

Certainly lower geared that the Diamondback that it replaced and my Cobia daily commuter.

As I'm going to change the chainring anyway it seemed to make sense to nudge the gearing up a little.

Sounds like the 44 would be the sensible choice - (way) cheaper than the 48, less of a jump from the middle ring, minimal technical issues and so on.

Londonscottish

44T it is then.

Just bought a Shimano chainring from Cycle Surgery which the fella assured me would fit.

Will find out today/tomorrow.

Thanks all for your help.

Londonscottish

The Rookie wrote:

How fast are you going - in a city - that you need a larger chainring?

If you want to go to a 48 (too big IMHO) you need trekking ratios throughout (28,38,48).

I checked the remains of my old Diamonback to see what it was running and in was a 46T.

Hence the disparity in gearing with my Hardrock on a 42T. (same 12T at the rear).

Still going with the new 44T as, apart from anything else, it's cheap and this is supposed to me my pub bike.

Happily left it locked in the street twice today. It's earning it's keep already :-)

The Rookie

Londonscottish wrote:

The Rookie wrote:

How fast are you going - in a city - that you need a larger chainring?

At the right cadance you can do easily over 20mph.

If you want to go to a 48 (too big IMHO) you need trekking ratios throughout (28,38,48).

I'm not going very fast at all! I set off from my house, hook it up 1,2,3 gears, turn right down a slight incline and my legs are spinning out in top. Feels like it's got comedy gearing, tbh.

Certainly lower geared that the Diamondback that it replaced and my Cobia daily commuter.

As I'm going to change the chainring anyway it seemed to make sense to nudge the gearing up a little.

Sounds like the 44 would be the sensible choice - (way) cheaper than the 48, less of a jump from the middle ring, minimal technical issues and so on.

Sounds like you need to learn to pedal at the right cadence rather than changing gearing to be honest.

Londonscottish

The Rookie wrote:

Londonscottish wrote:

The Rookie wrote:

How fast are you going - in a city - that you need a larger chainring?

At the right cadance you can do easily over 20mph.

If you want to go to a 48 (too big IMHO) you need trekking ratios throughout (28,38,48).

I'm not going very fast at all! I set off from my house, hook it up 1,2,3 gears, turn right down a slight incline and my legs are spinning out in top. Feels like it's got comedy gearing, tbh.

Certainly lower geared that the Diamondback that it replaced and my Cobia daily commuter.

As I'm going to change the chainring anyway it seemed to make sense to nudge the gearing up a little.

Sounds like the 44 would be the sensible choice - (way) cheaper than the 48, less of a jump from the middle ring, minimal technical issues and so on.

Sounds like you need to learn to pedal at the right cadence rather than changing gearing to be honest.

Hi Rookie that's not the problem. I do 1500-2000 miles commuting a year and know how my legs work. The problem is that I broke my old Diamondback which, once I'd had a proper look, turned out to have had a 46 tooth front ring. I subsequently bought an old Hardrock frame and forks (with crankset) which, once I'd had a proper look, turns out to have had a 42 tooth front ring.

When I'd originally finished building one bike out of the two I found the gearing very low - I was topping out ridiculously easily. That's all.

Now I've had a look at the respective chainrings I understand And I've bought a 44 tooth chainring to replace the 42 to increase the gearing a bit.

That's all, just a fella learning about gear ratios as he goes along.

The Rookie

My point is that unless you are running road tyres (smaller diameter) or are a superman, I don't believe you are actually topping out, 42:11 and 26" wheels at an easy 90rpm cadence means 26mph, topping out would mean at least 120rpm and over 33mph, most people i know can only hit much over 20mph on an MTB on the level for fairly short bursts. I run a 46:11 top gear on my commuter and only get anywhere near using that once the road points down.

If you have some logs showing your speed as topping out then I'll stand corrected.

Londonscottish

The Rookie wrote:

My point is that unless you are running road tyres (smaller diameter) or are a superman, I don't believe you are actually topping out, 42:11 and 26" wheels at an easy 90rpm cadence means 26mph, topping out would mean at least 120rpm and over 33mph, most people i know can only hit much over 20mph on an MTB on the level for fairly short bursts. I run a 46:11 top gear on my commuter and only get anywhere near using that once the road points down.

If you have some logs showing your speed as topping out then I'll stand corrected.

Don't have any logs or any measurement as I gave up on computers - I was timing myself through London traffic and taking silly decisions too often to try and beat my PB's......

Maybe I should download something onto my iPhone to see what vmax is on the flat?

All I know is that back when I had a computer I would quite easily hit the low to mid 20's on the (46T) Diamond Back. Downhill if I pedalled like a complete maniac think I could just about hit 30mph IIRC. According to the computer at any rate. Note that I'm running Conti Top Contacts, inflated pretty hard.

For any given speed on the Hardrock my cadence is higher. I guess when I started this thread I was wondering (outloud) why and looking for a solution. Now I know the difference lies in the chainrings so I'll replace the 42 with a 44 today to up the gearing a little.

Thanks for the input, though. It's the first time I've built up a bike from the remains of two others. It's interesting and satisfying but I do find myself scratching my head quite a lot - hence asking my half-though-through questions.

I like this forum - plenty of good advice and insight.

The Rookie

Pedaling faster is unnatural any first, but it's more efficient, you fatigue less and would save you having to change chainrings, the speeds you quote are far from topping out a 42:11 even on 1" slicks.