Ask RIDE…Can you explain meaning behind the jig test data?

I had recently been to the local supplier for Cannondale in Launceston and obtained a catalogue as I was interested in the CAAD10 and wanted to upgrade from my CAAD5, so your review was timely. The disappointing aspect of your review was not your words as they were complementary, but the results of your tests. Am I reading too much into the technical aspects about bike construction as I have gone cold on the idea of upgrading?

Regards Bob.

Hi Bob,

Glad you enjoyed reading the CAAD10 review because I thoroughly enjoyed riding it – even more than my CAAD9. Jig data and subsequent numbers from the test is something I discuss with people frequently. Generally it’s along the same lines as you have mentioned; that they had read about a particular bike, become interested in it but then thought it may be too stiff or compliant based on the jig test. From my experience using the jig data is best viewed as a base line of the frame’s characteristics and remember we are talking about deflection of less than one millimetre and the bike is also static.

The difference between the CAAD10′s bottom bracket of 0.58mm and the MCipollini RB1000 of 0.27mm from the latest edition of RIDE is really very small. The most relevant aspect – in my opinion – of the jig test is the correlation between the numbers and not just the raw data. The CAAD10 for example is balanced across the three points of measurement: bottom bracket, head tube and seat tube is 0.58, 0.45 and 0.57mm respectively and the bike performed in this fashion in it’s real test. When making a decision about purchasing a particular bike consumers need to be informed. If you have concerns then go to your local dealer and take it for a test ride.

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For your reference here is a full description about the jig test data which we have used for some time. It was written by Cam Whiting.

The test jig measures deflection of three frame points under a load applied via the crank arm. Basically, because it is a static test, it’s a ‘snapshot’ of how stiff the frame is. It is also an empirical test, ie. measurements gained from our jig tests are comparable only to each other. For instance, if the bottom bracket on bike ‘A’ deflects greater than bike ‘B’, we can only say that ‘A’ deflects more than ‘B’. We cannot say outright that ‘A’ will be any less stiff to ride than bike ‘B’ because frame dynamics are not accounted for.
The three fields of information presented are: the bottom bracket junction; head tube and top tube junction; and seat tube and top tube junction. Generally the lower the reading, the less the frame deflects. This would lead us to believe that the frame is laterally stiff (this property is mostly noted when riding).
Other points to note: 1. The weights are butted against the steel rod at a point which correlates to the average cleat centre of every pedal system on the market. 2. The bike is anchored at the fork and frame dropouts, via nutted axles. 3. We use calibrated Kincrome analogue gauges that measure to 0.01mm deflection.

Please take a moment and click on the Queensland floods charity auction. For sale is a Trek Madone 6.9SSL RadioShack bike signed by Lance Armstrong.

www.bikeexchange.com.au/auctions/20

Thanks for the question,

Alex.

Alex Malone is the Technical Editor for RIDE Cycling Review.

Author: design@ride

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