Cassette sizing help please

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Cassette sizing help please

Postby cerv50 » Sat Dec 28, 2013 06:10 am

Booked myself on a sportive for April which has a 25% climb in it. Around my way the steepest we get is at 20% and on my current 11-25 I think it could be a bit of a struggle. Chainset is compact so would you go for a 28 or 30?

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Re: Cassette sizing help please

Postby Carbonator » Sat Dec 28, 2013 07:18 am

:shock: 1 in 4!

How long is the climb and how far into the ride?

I would seek out a similar hill and see how you do first. You may not need it.

I put an 11-28 on for a sportive (ok, not 1 in 4) and did not end up using the 28 at all, so my lowest sprocket was 24 instead of 25.
I found myself using the 28 a lot in training though. Not because I needed it, just because it was there.

I am probably going to put an 11-23 (or poss 12-23) on this year as the closer gearing/ratios will be better for 95% of the ride than the help the largest sprocket gives on the hilly bits.

1 in 4 sounds tough though and there is no harm in a bit of insurance :wink:
How about go for the 28 (over the 30) and do a lot of hill training.
Your derailleur will be happier and your ratios will be closer.

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Re: Cassette sizing help please

Postby cerv50 » Sat Dec 28, 2013 09:59 am

Not sure how far in and for how long the climb is but from the route profile it looks pretty evil compared to what I normally ride.

Here is the site ... ute=full_j

I will probably go with the 28 as an emergency get out and try not to use it unless absolutely necessary :)

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Re: Cassette sizing help please

Postby Bobbinogs » Sat Dec 28, 2013 10:25 am

Gearing is very personal so it is hard for anyone to give specific advice. However, I do a lot of longer/hilly rides and never use an 11 sprocket for compact since I can spin ok up to ~120 and anymore than that I just don't bother but tuck in and concentrate on getting the lines right. That means I can go 12-27 (on compact 9 speed) and keep the ratio range from getting too great. Note: A nice wide range will give a nice benefit in that a majority of the ride can be done in a single chainring...but the downside of a big range is the gaps also get big and disrupt cadence.

There are a few 25% climbs around here and the problem most folks find is not about getting low enough gears but keeping traction on the back wheel (too low a gear means a very high level of leverage whilst the weight on the back is at its minimum). Hence, practice technique as well as look at gearing.

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