Geo changes in a full sus bike (BMC Speedfox)

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Hex
Posts: 130
Joined: Sun Sep 09, 2018 10:30 am

by Hex

Wisemen of WW.

I have come across a Speedfox from 2015 on sale from someone I know and I was looking at the geo and it got me thinking about something.

The current fork travel is 130mm with a 535mm length fork. If I was to change it with a 100mm travel fork, effectively reducing the length of the fork by 30mm, would the following be true?

* seat angle increase
* head angle increase
* lower stack
* longer reach

If so, can I then assume I would have a more aggressive position, more efficient pedaling motion (body more directly on top of BB) and the bike will handle slightly more twitchy/precise?

I don't do gnarly trails...I am more inclined into long steady rides on hard packed gravel...it's just the deal might be a bit too good to pass and I am currently looking for hardtails without much success within my budget.

Thanks in advance!

by Weenie


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de lars cuevas
Posts: 182
Joined: Fri Jul 28, 2006 8:28 pm
Location: the Netherlands

by de lars cuevas

Hi, all said is true. Angles will increase about 1,5 degree.

It's big no-go, though. Your bottom bracket height will be far too low: pedal strikes galore. Front and Rear suspension will feel unbalanced, the bike will not feel good.

Better just run it with the default fork, give fork and damper a bit more air pressure for mellower rides, try to get the seat forward and bars lowered, maybe try another stem. Or just ride more gnarly stuff and enjoy the great bike as it is. :-)

Happy trails!

Hex
Posts: 130
Joined: Sun Sep 09, 2018 10:30 am

by Hex

Aahh!

OK... So the bike won't "convert" satisfactorily then.

I am happy with the 73.5 seat angle, but I don't know how I feel about the 68.5 head angle, though. Some weeks ago I was loaned a teamelite which, if memory serves, has a 70 degree head angle and I felt it could still do with a bit more reactive maneuverability. It did have a 60mm stem and a 72cm bar which felt weird to me (road experience only)

I am also thinking of monstercross potential (another topic I have babbled about here some time ago) in the future, hence why the lower stack and higher angles would appeal in the future.

Maybe not the bike for me, though. Better keep to finding that one hardtail. There is a Stevens Sentiero on the market as well, but that is being sold by someone that knows someone that lives some 5hrs away from me. Price not as attractive either and I can't find much info on it. All I know is the geo looks a bit more to what I may be looking at (73.5SA and 70HA with 58 stack and 43 reach)

Thanks replying!

jemima
Posts: 270
Joined: Fri Apr 22, 2011 12:36 am
Location: Perth

by jemima

Hex wrote:
Fri Jun 04, 2021 6:33 pm
Aahh!

OK... So the bike won't "convert" satisfactorily then.

I am happy with the 73.5 seat angle, but I don't know how I feel about the 68.5 head angle, though.


Put in a 2.0? degree angled headset to suit? (e.g. Works Components UK).
Curve Grovel ti.

Hex
Posts: 130
Joined: Sun Sep 09, 2018 10:30 am

by Hex

jemima wrote:
Sat Jun 05, 2021 11:03 am
Hex wrote:
Fri Jun 04, 2021 6:33 pm
Aahh!

OK... So the bike won't "convert" satisfactorily then.

I am happy with the 73.5 seat angle, but I don't know how I feel about the 68.5 head angle, though.


Put in a 2.0? degree angled headset to suit? (e.g. Works Components UK).
OMG!

I need to check compatibility bu this could be it.

I imagine that if I increase that angle by 2 degreess, the bike will be taller so I can then consider reducing fork travel?

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

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ghostinthemachine
Posts: 780
Joined: Thu May 07, 2015 9:18 pm

by ghostinthemachine

You'd only be able to reduce it ~10mm, hardly worth the effort. Just get a longer, -ve rise stem if you want to adjust your position on the bike.

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