Helvellyn tri - gearing suggestions?

vannen

Hi,



I'm doing the Helvellyn in September - the cycle goes over Kirkstone pass via The Struggle.



I tried the climb the other day and found my TT gearset just isn't up to it. I've got 42T on the front and 12-20T on the back.



So I need to change either my cassette or my small chainring or both!



I've got a Dura-ace hollowtech II chainset.



Does anyone know what the cheapest way would be to get a decent lowering in gear ratio would be? I was thinking of just changing my small ring for a 39T but I'm not sure that'd be enough?



Cheers!

vannen

Forgot I'd posted this.



I went for a cheap compact Shimano crank set on the front (going cheap at £55) but that wasn't enough (on a gear chart, having 34 on the front and 21 on the back wasn't any better than 39/25 or thereabouts), so ended up getting an Ultegra 27-12 cassette. Used the lowest three gears from that cassette, and the rest from my 21-11 cassette. Was in first gear through most of the Struggle.



I'd definitely recommend using the cassette combination I used. I've found it's not too much of a jolt going from the low three gears up to the fourth, and you get the advantage of the rest of the cassette being close ratio and going down to 11. For a race like Helvellyn this was ideal as there's very long, fast flat and downhill sections as well as the crazy steep short sections.