General Discussion Triathlon Talk » Short Cranks, Compact Chain Rings, Advantages? Rss Feed  
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2017-02-14 11:08 AM
in reply to: alath

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Subject: RE: Short Cranks, Compact Chain Rings, Advantages?
Originally posted by alath
I do understand why they don't go this route in a routine everyday LBS fitting session.


The road bike world seems slower to adopt shorter cranks even the guys that TT.

I was speaking to a former pro cyclist now turned triathlete and his take was "cycling is steeped in tradition, triathlon more in innovation". And he appreciates both. The more I think about it, the more I believe it.



2017-02-16 8:53 PM
in reply to: rjcalhoun

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Subject: RE: Short Cranks, Compact Chain Rings, Advantages?

Happy to see this thread has generated so much good discussion on the topic of short cranks.

For many of the reasons sighted here are the same reasons I decided to go for the shorties. After my last Triathlon in late Oct. having posted one of my best race times to date. I could only maintain the aggressive dropped (in the drops, no aero bars) position for about 6-8 miles, then I would have to come up to the top of the bars for a break and then get back down into position. It felt like my thighs where pounding into my chest and the next day after the race I was getting intermittent sharp stabbing pains in the right pelvic area.

Also I could never effectively push past the mid cogs (19-17 on 53) on the flats. On the hills/mountains I would hold 23 on the 38 before finally having to drop to the 25 and suffer the rest of eternity. This was my motivation for going compact. I still did not want to make things easy so I opted for the 36 instead of the common paired (50)/34's.

The gentleman whom did my custom crankset mentioned I should also be able to bring the seat up roughly 3/4". I think I will leave the seat alone and do a few test runs on the trainer and see where I feel after that.

So in short, my expectations are: Opening up the hip angle, improved breathing and more effective use of available gearing. 

Also I will post the link to the gentleman whom made my custom cranks. I purchased them mid -week, he machined them over the weekend and I had them on the following Tuesday. Great communication and excellent craftsmanship. He started out with 180's and and drill/tapped them to custom length, cut off the excess and gave the ends a soft rounded brushed aluminum finish.

Bikesmith Design & Fabrication - Short Cranks

2017-02-17 4:49 AM
in reply to: rjcalhoun

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Subject: RE: Short Cranks, Compact Chain Rings, Advantages?
Originally posted by rjcalhoun
The gentleman whom did my custom crankset mentioned I should also be able to bring the seat up roughly 3/4". I think I will leave the seat alone and do a few test runs on the trainer and see where


If your seat height was correct before, then you need to raise your seat by the amount you shortened your cranks. So if your cranks was shortened 1cm (from 175 to 165 for example) your seat goes up 1cm

If you don't raise your seat, you are not getting full benefit of opening the hip angle and you are closing your knee angle and you seat is now too low.

Imagine when your pedal is at 6 o'clock. With shorter cranks, the pedal is closer to the seat. So you have to move the seat up to keep the same distance from seat to pedal.

When the pedal is at 12'o'lock, it is now further from the saddle. This is what give you more hip roo. By raising the seat for the above reason, you give yourself even more hip room.

Shortening cranks without moving seat is not good IF the seat height was properly set perviously.
2017-02-17 6:09 PM
in reply to: marcag

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Ventura, California
Subject: RE: Short Cranks, Compact Chain Rings, Advantages?

If you don't raise your seat, you are not getting full benefit of opening the hip angle and you are closing your knee angle and you seat is now too low.

I was able to quickly jump on and get in a few minutes this morning, first thing I noticed was I needed to raise the seat as has been mentioned; but even then I could already feel the difference with the seat as is. Going to raise it up 20mm (2cm) and do a fresh FTP test just to get a sense of how much difference it makes.

 

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General Discussion Triathlon Talk » Short Cranks, Compact Chain Rings, Advantages? Rss Feed  
 
 
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date : November 5, 2008
author : FitWerx
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Is gear overlap from the big to small ring a consideration? Will the ratio increment of the compact setup be very beneficial to my riding?