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 Post subject: 2018 Cervelo R5 geometry
PostPosted: Sat Dec 16, 2017 7:31 pm 
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Joined: Wed Aug 17, 2016 2:54 am
Posts: 4
Hello, I am thinking of getting a new R5.

I'm 169cm and fairly flexible. Currently I ride a Specialized Allez DSW SL size 52 and Focus Izalco SL size small.

The Allez, is the best fitting bike with a 100 mm -12 stem and 20mm spacers including headset cap.

I've been trying to calculate and compare stack and reach from the geometry tables using a downloaded excel spreadsheet and various online apps.

I'm struggling to replicate the size 51 R5's claimed stack and reach of 524 and 371 respectively, whereas Specialized numbers are pretty close.

Velologic frame comparison app, reports that only a 10mm spacer and 110mm -8 stem would be needed with the size 51 R5 in order to closely replicate the position of the Allez....this would seem too few spacers, my own calc's put it closer to 30mm!!!

Can anybody tell me if the claimed head tube length of 103mm is correct?

I've been using a nominal fork length of 370mm is the R5 fork longer?


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PostPosted: Sat Dec 16, 2017 9:42 pm 
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Joined: Thu Mar 08, 2012 11:43 pm
Posts: 3411
Yes, the R5 fork has a non standard axle to crown. Ignore the headtube length, you don’t need it. That’s why the stack measurement exists.

By the way, what do you actually mean you’re struggling to replicate the stack and reach? They are what they are.


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Posted: Sat Dec 16, 2017 9:42 pm 


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PostPosted: Sun Dec 17, 2017 7:11 am 
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Joined: Mon Mar 09, 2009 10:10 am
Posts: 37
What wingguy said. Look at stack and reach, will give you all of the info you need. You may not be able to replicate the position down to the mm without a custom stem, but you'll be pretty close.


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PostPosted: Sun Dec 17, 2017 8:50 am 
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Joined: Wed Aug 17, 2016 2:54 am
Posts: 4
Cheers guys,

The reason I was concerned about head tube length was that I use a spreadsheet to calculate Stack and Reach from the geometry and then compare them against published figures.

Its proved pretty accurate against real world measurements, but it seems to be very off when I input the R5 dimensions.

I don't suppose either of you happen to know what is the angle of the new Cervelo stems?


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PostPosted: Sun Dec 17, 2017 9:04 am 
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Joined: Mon Mar 09, 2009 10:10 am
Posts: 37
Stack and reach are published. Work's already done for you.


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PostPosted: Sun Dec 17, 2017 9:47 am 
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Joined: Tue Jul 18, 2006 5:18 am
Posts: 750
Location: Cambridge, New Zealand
Have a look at the distance from the brake mount to the fork crown (new bike on right)
Image

You can see the fork ax-cr has increased a lot. Likely so they can put a big clearance disc fork on and also have tyre-DT clearance. Visually I'd guess it's around 380, which is borne out by the comparison to the S5 (which has a 363mm fork).

So yes, you do get a perfect stack match with a 110x-8 stem and just a 9mm top cover. I've spent over a decade refining the velogicfit calculator and Cervelo were the first brand to supply stack and reach and I've never seen them go wrong. Specialized otoh frequently have mistakes in their geo charts (we run checking algorithms over all the data with the aim of ensuring quality).

_________________
http://www.speedtheory.co.nz
http://www.velogicfit.com - 3D Motion Capture and Frame Finder Software


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PostPosted: Sun Dec 17, 2017 6:11 pm 
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Joined: Thu Mar 08, 2012 11:43 pm
Posts: 3411
cyclenutnz wrote:
You can see the fork ax-cr has increased a lot. Likely so they can put a big clearance disc fork on and also have tyre-DT clearance.
Partly yeah (the clearance in the disc fork is practically gravel standard!). They also claim it lets them use more continuous fibres with less acute bends in the layup so the fork crown can be made lighter.

OP: The Cervelo carbon stem is a -8. One small oddity to be aware of if you're using the AB06 carbon bar that comes with the bike, it has a slight downsweep so the outside of the bar is somewhere between 5mm to 1cm lower than normal.


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Posted: Sun Dec 17, 2017 6:11 pm 


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