Custom titanium frame questions...

Discuss light weight issues concerning road bikes & parts.
2lo8
Posts: 440
Joined: Thu Mar 31, 2016 10:32 am

by 2lo8

pdlpsher1 wrote:
Wed Jun 20, 2018 12:19 am
415mm might be OK. My carbon bike has 405mm and I didn't like it. My builder's initial design has my Ti bike at 415mm. I requested him to increase it to 425mm because I wanted a smooth riding bike above everything else.

There's definitely a stigma on bike geometry. The opposite of tight handling is loose handling. The opposite of race handling is slow handling. Nobody wants a bike with loose and slow handling. So all marketing materials point to their bikes as having a tight and racy handling in order to sell more bikes. But what people often forget is that when it comes to bike design it's all about compromises. Each design has its pros and cons. The key is to find the right balance, not just buy what it sounds good from the marketing materials.

I should point out it's pointless to compare the trails between bikes from different makes. The trail is a function of the fork rake, the head angle, and the tire's outside circumferene. If you use a narrow tire the trail will decrease, and vice versa. My bike's trail is between 61mm to 63mm depending on what type of tire and rim I use. Since bike makers don't publish what tire circumference it used to calculate trail, it's not prudent to compare trails between different bikes made by different manufacturers. You can only compare different bikes within the same make.
Trail tells you at a glance if the front end geometry is out of whack. Fork rake can compensate for head tube angle to an extent. It's not unimportant as different makers have some very stange opinions on what a suitable front end geometry for XXS or XXL bikes is.
[6.6kg of no carbon fiber]
[2lo8.wordpress.com]
Your one-stop source for information and reviews on cheap eBay bike junk.

Hexsense
Posts: 462
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

pdlpsher1 wrote:
Wed Jun 20, 2018 12:19 am
Since bike makers don't publish what tire circumference it used to calculate trail, it's not prudent to compare trails between different bikes made by different manufacturers. You can only compare different bikes within the same make.
Then calculate it yourself from head angle, fork offset and tire size:
http://yojimg.net/bike/web_tools/trailc ... =622&tw=27

Most of the time, head angle and offset data from manufacturer are reliable enough for calculating trail with your desired tire size.
Then it is now comparable.

by Weenie


RyanH
Moderator
Posts: 1998
Joined: Tue Jan 17, 2012 4:01 pm
Location: Los Angeles, CA
Contact:

by RyanH

Finally got around to calipering the tubes:

Top tube vertically:
Image

Top tube horizontally at HT:
Image

Top tube horizontally at ST:
Image

Down tube horizontally at HT:
Image

Down tube vertically at HT:
Image

Down tube vertically at ST:
Image

Down tube horizontally at ST:
Image
Strava
Current Stable. The Snob Machine
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg | The Crumpton - 5.9kg

Berzin1
Posts: 14
Joined: Wed Jul 20, 2016 9:35 pm

by Berzin1

As for geometry, I was thinking of this-

1) 43mm fork rake

2) 73 degree head tube angle

3) 72.4 seat tube angle

4) 55mm top tube

5) 41.5 mm chainstay length

I wasn't thinking of getting another bike fit done, but I was recently made aware of a person who is excellent in my area, so the geometry may change.

I would like the funky-shaped oversize tubing similar to some Litespeed models, and I will be painting it glossy black with either light blue or Celeste lettering. That combination looks very nice and funny enough does stand out. When I had my LS Ultimate painted in black I got plenty of looks of admiration and compliments. Not that that matters, but I personally really loved the look.

As for who I'm thinking of doing the frame, it's a toss-up between Lynskey and Litespeed.

RyanH
Moderator
Posts: 1998
Joined: Tue Jan 17, 2012 4:01 pm
Location: Los Angeles, CA
Contact:

by RyanH

Litespeed doesn't do custom as far as I'm aware.
Strava
Current Stable. The Snob Machine
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg | The Crumpton - 5.9kg

RyanH
Moderator
Posts: 1998
Joined: Tue Jan 17, 2012 4:01 pm
Location: Los Angeles, CA
Contact:

by RyanH

Forgot to measure the chainstays and seatstays.

Chainstay at dropout:
Image

Chainstay height at dropout:

Image

Chainstay height at bb:

Image

Chainstay width at bb:

Image

Seastays:

Image

Image

So, ya, every tube is shaped on the LS except the head tube and I think the seat tube. The top tube is roughly shaped like an upside down bloated triangle at the head tube and tapers down to the rear seat tube.
Strava
Current Stable. The Snob Machine
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg | The Crumpton - 5.9kg

Hexsense
Posts: 462
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

Berzin1 wrote:
Sat Jun 23, 2018 2:10 pm
As for geometry, I was thinking of this-

1) 43mm fork rake

2) 73 degree head tube angle
Very standard and legit conventional balanced geometry.
These days people are running bigger tire than ever, which increase the trail. So to make it as racy as old 73deg+43mm rake with narrow tire, some brand move more fork rake or steepen head tube on their very racy bike. But there is nothing wrong with being a bit less twitchy with bigger tires, as people also ride on rougher road than before which benefit from less sensitive front end.

User avatar
kdawg
Posts: 92
Joined: Wed Nov 20, 2013 9:10 pm

by kdawg

I just got a custom steel bike. The contact points are basically all in the same place but the wheelbase is a little longer than my off the shelf Trek - and the first time I rode it home from work I noticed how well it handles - it just feels so much more stable leaning into a corner. I suppose that’s at the expense of quick maneuverability but it feels really good.
I'm left handed, if that matters.

jeanjacques
Posts: 121
Joined: Thu Apr 14, 2016 11:01 am
Location: France

by jeanjacques

Better to have have short wheelbase and long stem (like what we saw usually) or longer wheelbase and a short stem ? Maybe the second point permit the stability whitout sacrifing to much of maneuvrability.

Marin
Posts: 2819
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

In my opinion, better a longer wheelbase and a longer stem.

Nixster
Posts: 62
Joined: Wed Oct 04, 2017 3:30 pm

by Nixster

Thanks RyanH.
Lots of shaping as you say. Starting to get like a carbon frame with some of those, like flattened stays laterally instead of vertically for example.
Interesting that the DT is basically round at the HT then ovalised only at the B.B.

Berzin1
Posts: 14
Joined: Wed Jul 20, 2016 9:35 pm

by Berzin1

Well, Litespeed definitely do not do custom geometry, as someone previously mentioned, so Lynskey seems to be the front runner for now.

Question-is it true that a frame taking a traditional headset will be stronger than an internal headset? I'm just not a fan of the way ti builders design their headtubes, so I would consider some way to avoid that particular aesthetic.

Nixster
Posts: 62
Joined: Wed Oct 04, 2017 3:30 pm

by Nixster

Interesting one, I too have been weighing the pro and con of the two options. Are you talking tapered or straight steerer on the fork?

Inset headsets use smaller diameter tubes, usually 44mm. Tapered would be from 44-52mm or 44-56mm depending on whether the fork was 1.25 or 1.5". So the internal (tapered) heat tube would on the face of it be stiffer but more prone to local buckling failure, assuming the same wall thickness. Having said that I would expect that the DT would go before the HT in a typical front end crash type collision. So I don't personally think that strength in the sense of resistance to failure of the tube is much of an issue either way.

I think a lot of it comes down to aesthetics. Tapered can look pretty bulky on shorter head tubes, straight with an inset lower headset cup can look a little 'traditional' for some tastes. Certainly straight steerer forks with smaller dia headtubes and traditional headsets look pretty old fashioned to my eyes these days. I guess we're used to seeing bikes where the HT is larger than the other tubes in the frame because, you know, carbon. :)

Post Reply
  • Similar Topics
    Replies
    Views
    Last post