Double to Single chainring conversion

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TT25
Posts: 2
Joined: Wed Apr 29, 2015 4:40 am

by TT25

Hey everyone I'm a new member and hoping to get some advice for a conversion I want to do to my TT bike.

I want to convert my chain ring set up from a double 53/39 setup with a 11/23 rear cassette to a single oval chainring.

Would anyone be able to offer some advice as to what I should use?

My current set up is ROTOR noQ 53/39 with a 130 BCD.

I'm wondering about switching out the outer chainring for a "DOVAL" single oval chain ring but not sure what size I should go for as a single and what configuration cassette I should opt for?

Is there something I can use to avoid losing the chain up front so I can take the front Derailleur off?

I mainly race flat-ish TTs with inclines of up to 8% grades and with my current set up 39/23 as the lowest setting these can be a challenge if they're longer climbs so I would like to make that a little easier if possible but definitely no harder.

At the top end 53/11 seems nice on those longer descents but I rarely pedal in a race at 35mph or higher.

I usually achieve around the 58min mark for a flat 25mile TT and PB for a 56 mile race is 2:14 in a Triathlon.

I don't mind changing my rear derailleur if needed, my current derailleur is a Microshift Arsis, and does the job adequately with no issues over the last 3 years.

THANKS TO YOU ALL FOR READING AND YOUR INPUT!

Paul

spiderghost
Posts: 11
Joined: Fri Sep 12, 2014 5:52 am

by spiderghost

How much do you care about your cadence? To match your current range you would need a 53 front tooth and a 11-32 cassette which will have significant gaps.

It sounds like you are using the full range of your current double set-up. Whats the reasoning for going to a single ring?

by Weenie


TT25
Posts: 2
Joined: Wed Apr 29, 2015 4:40 am

by TT25

Hey Spiderghost, thanks for your reply!

I have a single ring MTB and I feel it takes all the decision making out of the riding, for example, if it gets steeper I have to decide whether to change to the smaller ring and then 2 gears up on the rear to match the same cadence in anticipation and on a TT bike with dual shifters it's time spent off the handlebars and sometimes a significant power drop. I train at all cadence ranges so not too worried about jumps in gears, I'm pretty sure I'll manage ok with the gaps, although that's yet to be proven!!haha

I've also had a few chain drop moments in races which makes me nervous shifting the front ring now. I've spent hours and many times tweaked the front mech set up and I think it's as good as it's going to get now but still nervous about that down and up shift.

What's the odds of dropping the single ring chain with no guard?

Would I need a new rear derailleur for a 32t ring?

Thanks again!

Marin
Posts: 2577
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

TT25, the Doval single rings have longer teeth with alternating thickness to prevent chain drops, so when you're running one you won't need a derailleur or chain guard/catcher unless you are racing CX in very thick mud.

Regarding cadence and speed, go to http://www.gear-calculator.com/ and play around with the settings.

If you really need to pedal up to 35mph, you'll need a 52 ring (narrow-wide chainrings only come in even tooth counts) which will leave you wanting on the climbs. Basically, you'll need to compromise on the low end, top end or gear spacing.

An 11-28 11 speed cassette is spaced close enough for racing, but the 52/28 low gear only equals a 39/21 on the double.

A 46 up front would get you 1 gear lower overall.

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