# STA, HTA, TT, and bike fit



## tx_newbie (Apr 23, 2006)

(Not sure if this is the right forum, but here goes).

Should I anticipate any major issues in bike fit if I were to change bikes with the following geometries:

Going from (currently riding)
-TT: 535mm
-HTA: 72.3 deg
-HT length: 122mm
-STA: 73.5 deg (with 30mm setback post, rails clamped in middle)

Going to
-TT: 525mm
-HTA: 72.5 deg
-HT length: 137
-STA: 74 deg (will use same seatpost)

I'm looking to switch geometries for a longer headtube to increase the effective stack while minimize the required spacers; I assume the STA can be overcome by moving the saddle ~0.5 cm (the HTA don't differ much). The shorter TT on the (potential) new bike is preferable, since I vary between a 100 or 90 mm stem on my current ride, depending on the course. 

Thanks


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## iliveonnitro (Feb 19, 2006)

Unless you are already on the verge of discomfort on your current bike, you probably won't even notice the 1cm difference. You'll feel a change in handling due to the different frame construction, but the fit probably won't matter.

The frame angles are negligible.


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## shomyoface (Nov 24, 2007)

At the saddle each angle difference in STA equates to roughly 1cm. In this example the difference is 0.5 degrees, and thus about 5mm steeper - losing 5mm. So in all, you will lose about 1.5cm, which is a ton the difference between two bike sizes. Unless you are using a bunch of spacers on your current bike, I would suggest getting a different bike, and/or moving up a size.


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## tx_newbie (Apr 23, 2006)

My current bike has 40 mm of spacers on an aluminum steerer tube (i.e. maxed out). Wanting to reduce the required spacers, I figure 1.5 cm increase length in headtube is a start (and yes, I have worked on flexibility and core strength--the upright riding position seems more agreeable to me). Part of me was wondering if the 74 deg STA on the (potential) new bike could be too steep that it coulnd't be overcome with the rearward saddle position--starting with the short TT means the effective reach wouldn't be too much with the rearward saddle position (I presume).

I'm essentially happy with my current bike and how my body feels on it (my everything bike--occasional racing, more often riding/training, schlepping around), though the 40mm spacer stack is occasionally concerning to me; this second bike is intended as a dedicated racer (crit and road). 

Custom aluminum (Tsunami) is a consideration, though I'm wondering if the stock geometry on the second bike might also work out [or if there are suggestions for a tall headtube/slackish STA bike].

Thanks all.


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## iliveonnitro (Feb 19, 2006)

shomyoface said:


> So in all, you will lose about 1.5cm, which is a ton the difference between two bike sizes.


I disagree. It's something that will be noticed, but it is hardly "a ton" of difference.


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