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-   -   help me choose the right size of the frame (https://www.bikeforums.net/showthread.php?t=1201591)

sweetspot 05-16-20 12:11 PM

help me choose the right size of the frame
 
Hi,

I am currently riding a Jamis Renegade Exploit 54 size bike with 30 mm spacers and 100 mm -6 stem. It fits me well but I am switching to titanium Enigma Escape and I have a big dilemma what size I should choose? 54 or 56? It would be easy if both sizes have the same seat tube angle and only different top tube lengths. But it is not that simple because size 54 has 74 seat tube angle and 540 mm top tube whereas 56 has 73 seat tube angle and 560 mm top tube. Effectively 56 has only slightly longer reach but due to the longer head tube (165 vs 145 mm) the stack is much bigger. What is even more interesting, the reach and stack of Enigma size 54 are very similar to my current bike but I am afraid that 74 seat tube angle and 540 mm top tube will feel worse than my current 73 seat tube angle and 551 mm top tube length.

Then there is also the topic of weight. Size 54 has thinner tubes and lower seat tube so it should be more compliant but with my 85 kg of weight I am afraid that the frame will be too flexy and I should go with thicker tubes of bigger 56 size.

I am 178 cm tall and my inseam is 85 cm.

What do you think?
Here is the link to the bike in question:
https://www.enigmabikes.com/pages/enigma-escape

Thanks for any advice!

gus6464 05-16-20 02:11 PM

You're looking at this the wrong way. The enigma is meant to fit differently than the bike you already have. Higher stack with same reach means that you will be more upright on the enigma vs the Jamis. You need to decide if that's what you're actually looking for. Also the 54 isn't going to be more flexy just because it's one size smaller. You downsize if you want a racier position and upsize if you want more stable feeling bike.

sweetspot 05-16-20 03:37 PM


Originally Posted by gus6464 (Post 21478746)
You're looking at this the wrong way. The enigma is meant to fit differently than the bike you already have. Higher stack with same reach means that you will be more upright on the enigma vs the Jamis. You need to decide if that's what you're actually looking for. Also the 54 isn't going to be more flexy just because it's one size smaller. You downsize if you want a racier position and upsize if you want more stable feeling bike.

it is interesting that you are saying that a smaller size will not be more flexy. Is this due to the fact that the tubes are shorter and this will compensate for thinner tube walls?

And regarding the difference between 54 and 56. Yes, 54 is racier but when you take into consideration the stem and spacers, you can easily achieve practically the same stack and reach on both frames. On 54 you have to use 30 mm of spacers and 100 mm stem (-6) and on 56, you use 10 mm of spacers and 90 mm stem (-6). This is based on this Stack and reach calculator But does the same reach and stack does mean that those bikes will handle in a similar way? The smaller bike will be more agile as a rule, but the stem will be longer so it will slow the steering slightly, and the bigger frame will be less agile, but the shorter stem will make things a little bit quicker. In terms of compliance, the smaller frame should be better due to the fact that seat tube will be shorter and thus seatpost will be more exposed and at the front, there will be 30 mm of spacers making a little more room for fork steerer to flex whereas bigger frame will have only 10 mm spacer (less flex). What would you choose?

gus6464 05-16-20 07:10 PM

You're not flexing anything regardless unless the bike is made is spaghetti. When sizing a bike taking into account headset spacers and using different amounts per bike is not an apples to apples comparison. You size it based on the raw numbers. If you like the position that your current bike gives you and you want the same one with the new one then go by whichever matches in raw numbers which looks to be the 54 enigma from what you're saying.


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