# Why did Look abandon slack seat tube angles?



## oneslowmofo (Feb 29, 2004)

To a non-Look owner, it looks like Look has moved on from their slack seat tube and head tube angles. I think the last with this type of geometry was with the 481SL. Does anyone have insight as to why?

I have a Cyfac that has a similar geometry and convinced that that type of geo works for me.

Thanks!


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## C-40 (Feb 4, 2004)

*makes little difference...*

The head tube angles have not changed. The only thing the slack STA does is affect your choice of seatpost.

I have two LOOK frames, one traditional KG381 and the newer geometry KG461. They have the same steering geometry and they fit the same, within 2mm. The KG461 requires a seatpost with about 2cm more setback to center the saddle on the post and position it the same relative to the BB.

In the case of these two 51cm frames, a 74.5 degree STA with a 52.5cm TT has a reach that's only 2mm longer than the frame with the 72.5 degree STA and 54cm TT.

When comparing frames for fit, it's the reach that's important. Reach is the TT length minus setback. Setback is the c-c fame size times the cosine of the STA. Reach can only be compared directly on frames of the SAME size. If you're comparing frames of a different size, then compensation has to be made for the difference in size.


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## tsteahr (Dec 29, 2002)

*Short reach is now gone*



C-40 said:


> The head tube angles have not changed. The only thing the slack STA does is affect your choice of seatpost.
> 
> I have two LOOK frames, one traditional KG381 and the newer geometry KG461. They have the same steering geometry and they fit the same, within 2mm. The KG461 requires a seatpost with about 2cm more setback to center the saddle on the post and position it the same relative to the BB.
> 
> ...


Very true about the reach. A parallel point not explicitly stated in the OP is that the short reach of the 451 is no longer available in the 06 lineup. As soon as I realized the 451 geometry has been discontinued, I urged a fellow rider with a very short torso to buy a left over 451. To my knowledge, I am not aware of any other non-custom frames with a reach as short as the now-discontinued 451.


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## orange_julius (Jan 24, 2003)

*Wheelbase?*

Has the wheelbase changed from the 481 to the current lineup, say the 585? Steeper STA is sometimes used to put the rider's final position further back relative to the rear wheel, with shorter wheelbase. I can't get the damn LOOK website to give the complete geometry chart on my Mac and the one from Competitive Cyclist doesn't mention wheelbase.

Nowadays many manufacturers use chunky/thick, aero-looking seat tubes, so in some cases it could be a matter of necessity to steepen the STA to have the same wheelbase.


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## tsteahr (Dec 29, 2002)

It looks like the rear half of the wheelbase, from the bottom bracket to the rear axel, is identical between the 5xx and the 481. This is based on the fact that they all have a chainstay length of 405mm and a BB drop of 70mm. The 486 has a slightly longer chainstay length of 408mm and the 451 had a 410mm chainstay length. It does not appear Look has tried to shorten the wheelbase through the use of steeper STAs.

The front have of the wheelbase varies between models and sizes, but your question seems to center around the wheelbase as it relates to the rear triangle. I hope this is the info you were looking for.



orange_julius said:


> Has the wheelbase changed from the 481 to the current lineup, say the 585? Steeper STA is sometimes used to put the rider's final position further back relative to the rear wheel, with shorter wheelbase. I can't get the damn LOOK website to give the complete geometry chart on my Mac and the one from Competitive Cyclist doesn't mention wheelbase.
> 
> Nowadays many manufacturers use chunky/thick, aero-looking seat tubes, so in some cases it could be a matter of necessity to steepen the STA to have the same wheelbase.


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## orange_julius (Jan 24, 2003)

tsteahr said:


> It looks like the rear half of the wheelbase, from the bottom bracket to the rear axel, is identical between the 5xx and the 481. This is based on the fact that they all have a chainstay length of 405mm and a BB drop of 70mm. The 486 has a slightly longer chainstay length of 408mm and the 451 had a 410mm chainstay length. It does not appear Look has tried to shorten the wheelbase through the use of steeper STAs.
> 
> The front have of the wheelbase varies between models and sizes, but your question seems to center around the wheelbase as it relates to the rear triangle. I hope this is the info you were looking for.


Thanks, that's exactly what I was looking for. In that case the handling won't change that much either, unless some bikes are radically different than the others in terms of stiffness.


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## C-40 (Feb 4, 2004)

*confused...*



orange_julius said:


> Has the wheelbase changed from the 481 to the current lineup, say the 585? Steeper STA is sometimes used to put the rider's final position further back relative to the rear wheel, with shorter wheelbase. I can't get the damn LOOK website to give the complete geometry chart on my Mac and the one from Competitive Cyclist doesn't mention wheelbase.
> 
> Nowadays many manufacturers use chunky/thick, aero-looking seat tubes, so in some cases it could be a matter of necessity to steepen the STA to have the same wheelbase.


A steeper STA would not move the rider BACK. If nothing else was different, it would move the rider forward and increase the wheelbase.

As I explained in my earlier post, the front-center can be the same, regardless of the STA. As I also explained, the STA mainly affects your choice of seat post.

LOOK does not list the wheelbase, just the chainstay length and the front center. The overall philosophy with regard to chainstaly length and front center hasn't changed much. They have gone away with the steep 74 degree HTA on the larger sizes, so the steering should be a bit slower, since the same 43mm fork rake is used.

With regards to the 585, there are fewer sizes than the traditional 481, so there will be some differences. The 555 is also not exactly the same as the 585 & 565 in the same size. 

There seems to be a website problem with the geometry chart on the international website. The Icon doesn't even appear where it used to be. I was able to find a geometry chart at www.lookcycleusa.com by using the search function.


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## orange_julius (Jan 24, 2003)

*A few assumptions*

Sorry I wasn't clear:

When the STA is steeper, and using the same tubing, the rear wheel can be pushed forward, thus horizontally closer to the BB. This shortens the wheelbase. In order to get the same position horizontally and vertically, the rider has to push the saddle a bit aft relative to the seat tube, and thus is position further "back" relative to the rear wheel. 

Anyways, this reminds me of those TT-type bikes from the 80s and 90s which has curved seat tubes to allow the rear wheel to come closer to the BB horizontally, but this is probably not that LOOK has in mind!


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## C-40 (Feb 4, 2004)

*The fixed point in frame design...*

is the center of the BB. The BB never moves; everything else moves in relation to it. The only way to move a rear wheel forward is to shorten the chainstays. Of course, if the tire hits the seat tube, the STA must be made steeper, the seat tube offset forward from the BB center, or the seat tube curved to clear the tire. With shorter chainstays, the rider will be further back, relative to the rear wheel, assuming the same KOP.

Overly short chainstays have been used on some bikes, with the advertising claim of better power transmission, but without admitting that this design can foul up weight distribution (too much weight on the rear). A bike will generally corner better with around 45% of the weight on the front.


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## foz (Sep 30, 2004)

C-40 said:


> There seems to be a website problem with the geometry chart on the international website. The Icon doesn't even appear where it used to be. I was able to find a geometry chart at www.lookcycleusa.com by using the search function.


the geo chart works fine on www.lookcycle.com there´s more info on there than on the usa page too. i don´t even know why they bothered with a usa page. the normal one is in english too, not only french...

foz


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## C-40 (Feb 4, 2004)

*you're right...*

They moved the geometry icon over to the left side. It used to be on the right, above the pictures of the frames.


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