A road MTB?

bliarout

I've got a Claud Butler Cape Wrath D24 which I've had for a while. It's now got to the point where it's running 26x1 slicks and I'm almost always in top gear and typically doing an indicated 18MPH on the flat.

My riding is mostly on fire trails which are well pot holed and on quiet but very badly surfaced/rutted roads. I live in the fens so hills aren't an issue, in fact the only time I see them is on the TV!

So I got to thinking, rather than get a roadie (which might be a bit sensible for me) Why shouldn't I increase my gearing, pare a little more weight and have a bike that's quick yet can still handle being thrown around on badly surfaced tracks.

The geo and quick steering make sense where I ride, I like the discs for their good wet/dry performance the SDG Bel Air it now sports is comfy And I can still wheelie and behave like a fool when the mood takes me.

I'm 45 so I'm never going to win any races but I'd like the quickest road bike that can handle very bad surfaces(think of having your jaw slammed shut and you'll get the idea)

So why shouldn't I do it or if I should what should I do to improve my on road speed?

skyd0g

You have probably done as much as you can do on your current steed. Next move is a CX.

night_porter

I don't know what your current gearing is but if I compare a road 9 speed cassette with an mtb 9 speed cassette they would be 12-25 or 11-34 this would indicate that the road cassette would only give you closer gears but not improve top gear, no help there then.

The largest standard chainring is likely to be 1 or 2 teeth bigger than your mtb (52 - 54) so very little gain there.

As skyd0g says you are probably maxxed out on your 26" wheels and need to move to 700c or a 29er or some custom fixed/single speed setup.

bliarout

Thanks chaps I believe my front ring is 22/32/42, I've only used the 22 once. I'm just trying to understand what each component does.

So, what difference does a close ratio chainset actually make? I assume it allows you to work your way up to the higher ratio more easily? If i lost the 22 i could start using the front ring more for my lower ratios?

What difference would 700 wheels make? I'm currently running 1"slicks on my 26" wheels. I don't mind having spare wheels with knobblies for riding in the snow if that's what it takes

Lillywhite

I've had Continental I" high pressure slicks on my Trek carbon fibre road bike with 42x13 as the largest gear. It's OK to a point but it's still a lot heavier than my Trek carbon road bike and that's the problem you will always have.

I personally, wouldn't spend any more money, trying to make the MTB lighter or attempt to put 700c wheels on which I doubt would fit or mess about putting a larger chainset on.

You need to consider getting a proper road bike IMHO.

Bobbinogs

...or something like a Kona Jake

Keep your current bike for pulling the wheelies though

bliarout

I'd love a road bike, I really would but the lightnes wouldn't cope with my commute (I've got to replace a bent rear spindle this morning) and there's a section of gravel for half a mile, wouldn't fancy negotiating that on a roadie

I know what I want probably won't suit most people but I can spin out on 42/11 with a moderate tail wind now. Just wondering what I can do with the wasted 22 ring.

My current rear cassette is a CS-HG30-8I which has the following ratios
11/ 13 /15 /17 /20 /23 /26 /30


I think could swap that for an HG90 which has 12 / 13 / 14 / 15 / 17 / 19 / 21 / 23 teeth and pair it with the FC-M311 which has 48, 38 and 28 teeth.

Woukld it be possible to climb the odd hill (less than one a month) on 28-23 gearing and would 48-12 give me a better top speed assuming I can pull it?

Mike67

I managed to get a square taper Stronglight crankset (double with a 130BCD chainring hole spacing) onto my old GT with a 48, 38 up front and a 12-34 at back for the hills.

The thing to be careful with when fitting big rings up front is the clearance to the chainstay. On MTB frames these tend to be quite widely spaced (mud clearance) so a large ring may catch on it.

I did get a 53 front ring on it for a while for use on the turbo trainer but found this a bit big for general use....mighty fast though when I was feeling up for it

Have a look at the clearance that your current 42 ring has..you may be able to judge just how much larger a ring will fit. I'm guessing your current chainset takes 110BCD rings.

Weight wise, the whole rig was under 10kg, but then it was a rigid with no heavy suspension forks.

night_porter

I think that close ratio cassettes allow a constant cadence (spinning) by not changing the gear too much. I don't think that will help you as the top gear is slightly larger than what you currently have and it needs to be smaller to increase speed.

Think of it like this: The fewer teeth at the rear means harder to pedal but faster speed. The reverse is true for the chainring the fewer teeth on the gear at the front means easier to pedal but slower speed.

My road bike has a compact groupset with 36/50 at the front and 12/25 at the rear so as Mike has said get the biggest gear which will fit at the front and I would suggest keeping the broad spread mtb cassette to make life easier for any hills.

To be honest the granny gear (small ring) on the front should be pretty useless when riding on roads for most riders but comes into it's own off road when climbing very steep inclines.

Also bear in mind that a bigger ring at the front will need you to increase the size of your chain and possibly replace the rear derailleur if it cannot cope with the added slack. This might be okay if you never use maximum crossover with big front and big rear or small front and small rear, this is very bad for chains anyway.

Sorry about the confusion in my previous post but your frame decides the size of wheels you can fit so it is not possible to fit larger wheels to your bike. Larger wheels = bigger circumference = more travel per revolution = faster for the same turn of the pedals. But to get bigger wheels you would need a new bike.

The 29ers are mtb bikes (strong and tough) but with the same size wheels as a roadie for speed. People who ride 29ers look like giants when they ride past me on my 26" wheeled mtb.

Hope this helps if it doesn't try looking at http://www.sheldonbrown.com/ for some real expert advice.

bliarout

Thanks again I went to my local shop and they had a 44 tooth chainring and a 12/23 cassette but that would have given me a lower top gear (I think)

Is 48/12 much of an upgrade? I think I can probably get a 11/23 casette online.

The roadies did look lovely but I can't see one coping with a mile of gravel and four miles of rutted track.

bliarout

I believe I've calculated myself into a corner

According to the Sheldon Brown ratio calculator my standard gearing is as follows:

22 32 42
11 3.6 5.2 6.8
13 3.0 4.4 5.8
15 2.6 3.8 5.0
17 2.3 3.4 4.4
20 2.0 2.9 3.8
23 1.7 2.5 3.3
26 1.5 2.2 2.9
30 1.3 1.9 2.5

If I go for a 28/38/48 chainset and a close ratio cassette I get:

28 38 48
12 4.2 5.7 7.2
13 3.9 5.2 6.6
14 3.6 4.9 6.1
15 3.3 4.5 5.7
17 3.0 4.0 5.1
19 2.6 3.6 4.5
21 2.4 3.2 4.1
23 2.2 3.0 3.7


Which seems to be about "half a gear" to me, not really a worthwhile gain?

My only option might be just to change the chainset which would give me

28 38 48
11 4.6 6.2 7.8
13 3.9 5.2 6.6
15 3.3 4.5 5.7
17 3.0 4.0 5.1
20 2.5 3.4 4.3
23 2.2 3.0 3.7
26 1.9 2.6 3.3
30 1.7 2.3 2.9

Which ups my top gear ratio by effectively one gear?


Unless anyone can see a flaw in my thinking/calcs I think thanks to the links I found in here and the info posted I've laid the idea to rest.

Bum.

dannc

cyclocross??

night_porter

A complex subject with no easy answers!

I think the suggestion of a CX or Cyclocross bike might be your best solution.

Although they look similar to a racing bike they are very much a different beast, I think of it in these terms:

Racing bike = Ferrari sports car - Road racing vehicle, lightweight bike with high gears and large wheels for speed

Mountain Bike = Landrover short Wheelbase - Go anywhere mudplugger not too fast on smooth roads, heavyweight bike with low gears and smaller wheels for power

Cyclocross Bike = Range Rover - Fast on and off road, wider tyred comfort and grip but will take narrow tyres too, medium weight bike with in between groupset and bigger wheels for speed

There are many other incarnations but these show how well a Cyclocross bike might suit your purposes better than your current steed.

grantus

Rigid fork - evena cheap alloy one will save you 1.5kg over what is stock on the claud butler. A bit more dosh on a nice Pace carbon would save you even more.

50/34 compact up front and a 11-28 rear will give you all you need.

Sora chainset, BB cups, cassette and cheap alloy fork - £100 - second hand you could get it a lot cheaper