Question from a serious cyclist with a cheap bike

[Dr_Pepper]

Hi Everyone, have had a nose around and this seems like a nice place to be. I wonder if anyone can help my dilema.

I have a relatively cheap (£300) bike which is a Felt MTB, and I don't cycle regularly but when I do it's always something big - I've done LEJOG and the length of Ireland, a few road races, and also lots of singletrack mountain biking at Afan Forest and the like, all on this bike. As I do both MTB and road racing, I have 2 sets of tyres which I swap as appropriate. I love the bike as it never goes wrong, also budget doesn't really allow an upgrade. The only thing is; on the road I often run out of gears for going fast on the flat - for this reason I swapped the original 12Tooth on the back to an 11Tooth which improved things a little but I feel I need more at the front - at the moment my top cog is a 48Tooth, I'm aware this is quite big for a MTB but I want bigger!

Anyway, the only thing that has EVER gone wrong with this bike is the bottom bracket (square taper type) which has failed 3 times and I annoyingly I can now hear is again on it's way out. I was trying to kill both birds with one stone here but I can't find out the info that I need - can I upgrade to the more modern bottom bracket and get a 3-cog chainset to go with it which has a 52T for example? I am having trouble finding out whether the BB is upgradable and whether I can buy such a chainset to go with it without breaking the bank?

Cheers for any help!!!
Richard

[Brucey]

http://www.chainreactioncycles.com/Models.aspx?ModelID=40623

is a basic ST triple which may do the job.

http://www.google.co.uk/products/catalog?hl=en&q=tiagra+chainset&um=1&ie=UTF-8&tbm=shop&cid=11433081182996921544&sa=X&ei=-BsxUKOrFbGV0QXM7YGADQ&ved=0CGgQ8wIwAg

is an 'improved' model with a H-II BB system but is now a NOS model so many shops don't actually have it.

Many folk find that the H-II system (for all its potential advantages) does not last as long in the real world as a half-decent ST BB unit. Something like a shimano UN53 normally lasts quite well. Do you have a 68mm or 73mm BB shell?

The chainsets you should be looking at to get the gearing right normally have a 'road' chainline which is slightly closer to the chainstays than the 'MTB' chainline. This (plus the bigger chainrings) means they don't fit every MTB frame and even if they do, it may only work with a different front mech and that may not play well with flat bar shifters because they pull a different length cable on the front mech to 'road' ones. However if you have a 68mm BB shell you may be able to shuffle everything around a little bit as there are 5mm of spacers with some H-II BB units, and this may let you keep the MTB front mech. There is still the chance of the big ring size being a problem tho'.

Only someone who has converted a bike like yours will be able to tell you for sure that it will work OK; it is otherwise a suck-it-and-see job.

It might be simplest to get a larger chainring set to fit your existing chainset.

cheers

[Brian73]

If the BB keeps failing prematurely then there's something wrong down there. Is the shell or threads misaligned? If there is a problem no BB will work well, an external bearing BB will be worse than a sealed cartridge as they require perfect alignment.

[Big T]

You do road racing on a Mountainbike? You must be seriously fit.

[Dr_Pepper]

You do road racing on a Mountainbike? You must be seriously fit.

Don't worry I'm only talking local events believe me I'm no Mark Cavendish. That said I do surprise a few people.

Thanks a lot for your answers especially Brucey that's really helpful. Thanks for that link I might go for one of those then - do you think 48T to 52T will make much difference? This is quite important to me because at the moment I sometimes do pretty much a whole ride without changing out of top gear (however I do live in Essex!)

Unfortunately I don't know what size BB I have because even though I have the tool, I can't get the f****r out. I'm happy to stick with the old-style tapered ones, Brian - the original was a bearing one but the current one is sealed unit, but it's still broken -any recommendation on a most quality brand?

Thanks again

[Brucey]

stuck BB units can be a nightmare; obviously don't forget that the left cup is a RH thread and the right cup is a LH thread!

You should notice the difference between a 52 and a 48; if not this would be rather unusual! I am a bit concerned that fitting a road crankset might throw up some problems but I guess you are going to have to find out.

However unless you are doing about 30mph everywhere it is most likely the case that you are not pedalling with a very high cadence as yet. It isn't compulsory to pedal at ~90-100rpm when road racing but this is the speed at which very many successful riders do pedal. Some time triallists pedal more slowly than this but most don't. A lot of riders start out mashing big gears and then find that their cadence goes up over time as they become better pedallers, but this does take practice.

To put things in perspective many racing cyclists can pedal usefully at 120rpm for short periods. IIRC V. Ekimov's pusuit world record saw him average ~145rpm from a standing start... I reckon the US ladies team pursuit squad lost so badly to the GB team in the olympics because they were (just fractionally) overgeared....

cheers

[Dr_Pepper]

thanks so much for the detailed reply.

I must admit that I am not an expert and I just had to look up what Cadence means but I see what you're saying. I do definitely tend to prefer as high a gear as possible, ie when going up hills at the same speed as someone else, they are usually pedalling much faster.

My regular circuit is 13.4 miles I know this because I just spent ages on google maps working it out, and it takes me just under 45mins so that's average only 18mph. I definitely feel that if I had a higher gear I could go a lot faster. Maybe I will try and count/work out my cadence too!

Cheers

[Tonyf33]

a 48x11 combo on narrower mtb slick tyres such as 26x1.25 tyres is 107, a 53/13 on 700x25 tyres is 107.5
Even at a steady 90rpm which isn't hard to attain that is almost 29mph on 26x1.25 tyres, so my question is do you do more than 30 mph regularly on the flat (I'd say downhill but you did say Essex..lol) or do you feel like you are spinning out at 90rpm??
It just seems odd that you feel the need for higher gears when the ratio you have seems to be more than adequate unless you are unable to spin the cranks at more than 90 rpm?
You'd likely need to change your mtb front mech if going for a 'road' chainset with anything bigger than 50T

[PBA]

Of course mashing a high gear is also not good for bottom brackets...