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Bike sizing advice

Hi all

I unfortunately had one of my bikes stolen, however on the plus side the insurance has paid out so I am now in a position to buy a new bike. Silver clouds and all that…

I would like to get a Kinesis 4s disc as a 4 season bike, which I will run alongside a Giant TCR. However when I review the sizes I feel I am inbetween the 51 cm and 54 cm sizes. I am comparing to my TCR which fits me very well and believe that stack and reach are the most important figures to compare (please correct me if needed).

As you will see the stack on the 54cm is very close, but the reach on the 51cm very close. I am concerned if I go for one or other I will be either too stretched or too low. Although a 4 season bike I don’t want to be overly vertical.

Given I cannot go and see the bike at the moment does anyone look at these figures and have any advice? Whether that is on my interpretation of geometry or practical advice, either would be appreciated.

I cannot see how to add a picture, but hopefully this link take you to a comparison of the models: https://geometrygeeks.bike/compare/kinesis-4s-disc-2019-51cm,kinesis-4s-...

 – from the excellent site geometrygeeks.bike if you are not aware of it.

Cheers!

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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5 comments

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zedthegreat | 3 years ago
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Thanks all - useful advice! 

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AfterPeak | 3 years ago
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How many spacers do you have under your current stem and how long is it?

After cocking buying the wrong size bikes (and following proper bike fit) I would now always go for the smaller size personally. It is much easier to make a smaller l bike fit you. We are talking a couple of stem spacers and a longer stem to archive the identical stack and reach to your old model. You can also flip the stem to get extra height.

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Secret_squirrel replied to AfterPeak | 3 years ago
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I'd go with smaller for AfterPeak's reasons and the one below

A 4 seasons bike can afford a little more stack height than a heads down summer bike.

I am in a similar situation.  I have a 51R Strael and a 53cm Ribble carbon jobbie.  I actually spend more time in the drops on the Strael even though its a higher stack, because it feels more natural than the deeper drop & longer reach of the Ribble.

My theory (no proof) is that body shape from drops wins aerodynamically over a lower stack but riding on the hoods.

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zedthegreat | 3 years ago
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Looks like I can add a picture to the comments - geo's attached

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kil0ran replied to zedthegreat | 3 years ago
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They look pretty similar and I'd personally go with the 54 with a stem 10mm shorter than what you've got on your TCR. That shouldn't affect the handling too much. The critical measurement for me is the head tube length on the 51 Kinesis - 125mm vs 148mm is a big difference. Would mean that you'd end up running a lot of spacers under the bars if you went with the 51. Not necessarily a problem, other than aesthetics which may or may not be important.

The only thing I can't tell from the geo is position of the saddle relative to the BB (I forget what this measurement is called but it's as vital as stack and reach as getting it right provides your pedalling platform, and it's not as adjustable, particularly with short setback seatposts). It's generally a function of seat tube angle and saddle height, which is similar between the 54 Kinesis and your current bike. Are you currently running an inline or setback seatpost on your Giant? Is your saddle positioned at one of the extremities of travel or more or less in the middle?

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