Help with gearing please. Smaller cogs?

jackthehat

Hi folks,

I got a cheap road bike last week (Raleigh Airlite 100 2008) and I am really pleased with it. I will only be using it for commuting and have absolutely no intention of racing.

However, I was a little disappointed with top gear as it doesn't really get the bike moving quickly downhill (not much faster than my £65 mountain bike). So far I can't get it past 35mph as my legs won't go round any faster. I did a little bit of research and discovered that my bike has Shimano 14-28 cogs (sorry, I don't know the proper terminology yet). Would changing these to Shimano 11-28 make a big difference? I saw them on Wiggle for about £10. If so, is it a specialist job to change a set of rear cogs or can I do the job myself? I am not shy of getting stuck in with my spanners. Is there a special tool that is required?

Any advice appreciated.

tenbar

It's not a particularly tricky job but you do need the correct tools and compatible parts. Personally, I would take the bike into a good local bike shop and tell them your problem. Any LBS worth their salt will be able to tell you what you need and do the job for you very quickly.
cheers
tenbar

Bronzie

It's a doddle to swap the rear cassette - all you need is a chain whip tool, a cassette lockring tool to suit your cassette and a big adjustable spanner. The tools will cost you £20 or so, so it may be cheaper to get the LBS to do it for you if you don't plan on changing cassettes often.

Fitting an 11 instead of your 14 smallest sprocket will make quite a big difference to the gearing although to be honest it's not worth trying to pedal once you go over 35mph - just make yourself more aero on the bike by tucking your head down close to the bars and you'll accelerate down a hill anyway.

jackthehat

Thanks for answering my questions. Ideally I would like to do the job myself. I have bought some Continental Duraskin tyres to help stop punctures on my way to work so I would like to get those on at the same time as a new cassette. Plus, if I do it myself, I will know what to do in the future.

I am still a little puzzled as to which parts are compatible. Maybe you can help.

My bike currently has a Shimano TZ07 14-28 freewheel/cassette fitted. See here: http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0230087381

I have seen a Shimano HG30 11-28 cassette that I would like to fit, see here: http://www.wiggle.co.uk/ProductDetail.a ... 20Cassette

The HG30 cassette doesn't look like it has the centre section fitted (is that the freewheel bit?)

Any advice on whether the HG30 will fit my bike?

Bronzie

Doesn't look like it - the one you have fitted incorporates the freehub within the cassette body and screws onto a threaded section on the hub.

The HG30 fits onto a splined freehub body that is part of the rear wheel hub like this


You need to find a 7 speed freewheel cassette to fit a threaded hub with the correct sprockets you are after.

jackthehat

Thanks Bronzie, that's really helpful of you.

Oh well, the only freewheel cassette I can find is a Shimano 11-34 megarange. From what I have read, it seems as though I would also need to change the derailleur for the 34 tooth cog to work. I can't be bothered with all that and I certainly don't need a 34 tooth low gear. So, unless anybody knows of a 7 speed 11-28 freewheel, it looks like I'll have to put up with what I already have.

Thanks everybody for your time.

Redmog

What about putting a bigger sprocket on the front?

jackthehat

Yes, a friend of mine just suggested the same thing. Is there much work involved in changing the size of the front sprocket? What sort of increase in size should I be looking for to get a significant difference in the high gear?

jackthehat

Another problem with that... my bike already came with a 175mm 52/42 front crankset. I have had a quick look and I cant see any others much larger than that. I have seen one or two 180mm sprockets but these have no more than 50 teeth and are £200+.

Am I right in saying that I need more than my current 52 teeth to make a difference to the highest gear? If so, I think that option is also out of the window unless you chaps know different.

Bronzie

52x14 = 100 inch gear
52x11 = 127 inch gear
66x14 = 127 inch gear

So if you can find a 66T chainring to fit your cranks you are laughing :shock:

Presuming the chainrings are held onto the cranks with normal chainring bolts (rather than being permanently riveted to the cranks)..............and depending on the number of arms on the crank and the Bolt Circle Diameter (probably 130mm on Shimano) you will be able to get a bigger chainring, but 61T looks like the biggest available...............but that's going to cost you £55! You also need to check that such a huge ring won't grind on the rear chainstays! Back to square one?

To my mind I'd look for a cheap 2nd hand rear wheel on Ebay with the splined freehub as pictured above and then you have a much wider range of choice in terms of gearing.

IDK

Zenith do a 7-speed freewheel (13-21, 13-24) but apart from the Megarange I think you'll be lucky to find one that goes down to 11/12. But why bother? How often on your rides do you actually spin-out? If you really want bigger gearing then you'll probably have to ditch the screw-on hub and move to a free-hub. You can then build what ratios you like. You'll need some spacers to support a 7-speed cassette on a 8/9 speed hub but it will work fine.

jackthehat

Thanks again Bronzie and IDK.

I think the bigger front sprocket may be a bit more hassle than I expected, and a bit more expensive! IDK, I've only had the bike a week but I've done 100 miles on it back and forth to work. On 2 or 3 occasions I felt like I needed an extra gear to keep the bike accelerating. Most of my journey is on the flat. With a tailwind I feel I could do with a bit more oomph. I am a bit of a big bugger at 6' 4" and 100kg and bought the bike to make the journey quicker and easier. It's certainly made a big difference compared to my MTB but I find it frustrating when there's an opportunity to speed up but not having the extra gear to do it.

I suppose I'm being a bit picky. I may keep the bike as it is for a while. It's set up perfectly at the moment with lovely silky gear changes so it would be a shame to tamper with it. As you say Bronzie, maybe I'll wait a while and get new wheels in the future with the splined freehub.

Not quite as simple as I first thought! I'm loving the bike though... compared to my cast-iron MTB it feels like Lotus Esprit Turbo! Can't get it past 35mph yet though.