Chainset Advice

cormacjones

Hi,

I'm buying a bike online and I need some advice on chainsets

My options are as below. Can anyone tell me what difference a chainset makes and what you'd recommend.
Chainset

Shimano Dura Ace 7900 Chainset 50/34 170mm
Shimano Dura Ace 7900 Chainset 50/34 172.5mm
Shimano Dura Ace 7900 Chainset 50/34 175mm
Shimano Dura Ace 7900 Chainset 53/39 170mm
Shimano Dura Ace 7900 Chainset 53/39 172.5mm
Shimano Dura Ace 7900 Chainset 53/39 175mm

thanks

edit same question re: which cassette

Shimano Dura Ace 7900 10 12-25 Cassette
Shimano Dura Ace 7900 10 12-27 Cassette

uberwolf

first off, and this isn't meant to be really cruel, but if you don't have the answer to this question, you probably don't need to be spending your money on Dura Ace, a more moderately priced level may suit?

the difference in chainset is two fold. The first figure is a split in gear sizes the larger number being the outside or big ring, and the other your small ring. Your decision here is somewhat guided by the decision you take with your cassette which I will come to.

the MM measurement is the length of the crank. The law of the lever, the longer the crank the harder to turn but the faster you will go. If your pedalling style is to plod the longer crank may suit, if you have a high cadence the shorter crank may suit. Unless you have a strong preference here, I would be taking the middle of the three here's a good looking guide

Back to gear choices. The 12-27 range has one further easy gear than 12-25. Mightn't seem like much, but you could really appreciate it some day! If you're a tourer or heavier cyclist this might be a reasonable selection.
The tighter selection might suit someone less likely to encounter steep climbs or who requires the option of finer adjustments to their gearing.

Likewise with 50/34, 53/39 question. Most cyclists, on a flat road at a modest cruising speed will be in their small gear at the front. Both 34 and 39 are small by Irish standards, and I would have though 39 would be more than small enough in combination with the 27 on the rear to facilitate you.

more reading here

ashleey

12 25 cassette, 53 (52?) 39 crankset and 175 if you are tallish. Don't buy dura ace unless you are a racer. If you are a keen amateur 105 is perfectly good. Spend the savings on some good other stuff

Liamo08

I think if you're asking this question then I'm guessing that you're not going to be racing on this bike if not then I'd go with the thought of giving yourself as wide a gear selection as possible and get the compact ie 50x34 and 12 - 27, if a 50 x 12 as your biggest gear isn't enough for you then you probably need to give up the day job. I think giving yourself a few easy gears is a great idea especially if you're going to be climbing any serious hills, at the end of the day when it comes to gears - Better to be looking at it than looking for it.

Lumen

Gearing depends on your power/weight and how many hills you'll be doing.

A wider spaced cassette will be more gappy, which can be slightly annoying, whereas not having a small enough gear will actually make you slower.

I blame my slowness on the Three Rock hillclimb down to gearing (easiest gear was 34/23). Average cadence was 63rpm, compared to my previous personal best 20 min power at about 75rpm.

Since I assume you're not racing, I'd choose 50/34 and 12-27.

Ideal crank length depends on height and other things (like how strong your knees are).

And buy Dura Ace if you want it/can afford it. The new Ultegra crankset is really ugly anyway.

blorg

As others have said if not racing go for 50-34 12-27 and have the gears. There really is no significant disadvantage if not racing and to be honest even only a minor one when racing; I have raced myself on this combo (and indeed won) because I didn't have a chance to change it over between hilly events... Better have the gears and not need them than not have them when you need them.

Also if you are asking these questions as others have said you probably don't need Dura-Ace, I wouldn't bother unless you are getting a particularly good deal.

cormacjones

thanks for all the advice and I decided against splurging on Dura Ace as a result of it. I actually went for the PX Ultegra deal (notwithstanding Lumen's correct obseration on the aesthetics). I went for the middle crank with the the bigger set of gears as I won't be using it for racing.

Thanks again to everyone who replied as I was completely clueless...