Track bike geometry charts - I need help

but will get lots of toe overlap, which will always be an issue with a shorter top tube compared to seat, without adjusting downtube

I've done a bit of research on fork rake (bought forks for a hybride, and a 29r), and after a headache decided togo with 'an informed guess'.

As road/track bikes are concerned I'm a bit surprised to hear 35mm decribed as 'very steep'

Would'nt it be something like..

35mm = steep
42mm = average
50mm = slack

I'm sure I've seen 30mm rake forks before, but its all tied into the head tube angle and the resulting 'trail'...theres my headache again.

try this
http://kogswell.com/trail.php

The guys at Tommasini probably know better than this amatuer internet bike nerd though ;)

35mm seems a little on the tight side for the street but certainly not out of the ordinary on the track.
With a 75 degree headtube you may find that a fork of 38-40 will be much more comfortable to ride on the road.

Don't think absolute chainstay length is critical, after all you can move a wheel back and forth a good 2cm in a horizontal drop-out.

chainstay length is absolutely critical to how a bike rides, slack seat tube angles will need longer stays and steep ones can use shorter.

Bear in mind for the road, the closer the rear axle is to your arse, and the nearer that axle is to your BB, the more of the road you are going to feel, this is why many track bikes give a harsh ride, but are responsive to what you are putting through the cranks. the link you posted about higher BBs shortening the stays bears this out. simple when you think about it.

a good road frame will be the perfect balance between the two.

this is why so many custom builds fall very short of the customer's expectations, the hard work has already been done. I would say a fixed frame for the road should be the same as a nice road bike that fits you, but with a 10mm higher BB height.

once you start tweaking seat and head tube beyond sensible parity, you have to be spot on with the angles, this is where people also fall down, a bike with a very long top tube compared to seat tube will usually be ok, within reason, but the other way round and it may handle like a pig with rabies ..

it looks like your amended geometry was the right thing to do SB

That post from tommasini is scary, they don't really sound like they know what they are doing.

Fork rake and headtube angle are inextricably linked.

When I was at the workshop of a certain experienced frame builder recently, 'Right, the fork rake on those is 28mm, so you will have to have a 75 degree headtube'

35mm sounds a bit slack to me. Will make for an awful weird ride with a steep headtube. My dolan has 30mm fork rake on a 74 degree headtube and the bianchi pista is 28mm.

My new frame, and I trust the experience of the builder, is 57cm c to c in both directions, 75 seat, 75 head, with 28mm fork, rear clearance will be 0mm on 22mm tubs to keep the rear stays short, and it is either 11.25 or 11.5 inch BB hight (I can't remember). That felt really nice for me on the jig and should handle well, I'm using a 12 stem.

35mm is slack for a track fork, but tight for a road fork. course all depends on HTA, as you say

pro-lite track forks and the older alpina wing tt forks were a 35mm rake.

thing is he wants a bitsa frame, tomassini normally would build a track or a road frame.

"bitsa frame" what does this mean? Tommasini already build a road/track sintesi so they ought to have this knowledge - the Cinelli SuperCorsa Pista has a 35mm rake with a 75 degree head angle and I doubt they built this strictly as a track bike - so I reckon 35mm must be near the mark - toe overlap isn't an issue - so is the relationship strictly headtube angle and fork rake or do other aspects of the geometry come into play? what about fork offset ? do 'track' forks have a fixed offset or does this vary also - I feel like I am delving into the dark arts of frame building here

To be fair to Tommasini this e-mail came from Barbara who works in the sales office and I doubt they get many request for this style of bike.

http://davesbikeblog.blogspot.com/2007/05/trail-fork-rake-and-little-bit-of.html

then get a 57cm sintesi

That post from tommasini is scary, they don't really sound like they know what they are doing.

Fork rake and headtube angle are inextricably linked.

When I was at the workshop of a certain experienced frame builder recently, 'Right, the fork rake on those is 28mm, so you will have to have a 75 degree headtube'

35mm sounds a bit slack to me. Will make for an awful weird ride with a steep headtube. My dolan has 30mm fork rake on a 74 degree headtube and the bianchi pista is 28mm.

My new frame, and I trust the experience of the builder, is 57cm c to c in both directions, 75 seat, 75 head, with 28mm fork, rear clearance will be 0mm on 22mm tubs to keep the rear stays short, and it is either 11.25 or 11.5 inch BB hight (I can't remember). That felt really nice for me on the jig and should handle well, I'm using a 12 stem.

this is where i started to get overwhelmed (see my above post). From the BB shell forward, there are a lot of variables which are all dependent on one-another for bike that will actually ride. I mean you can reallly fuck up the bike if the trail isn't dialed.

If i were building the bike in this thread, i would gank the geometry of the front (i.e. the headtube angle and fokr length/rake) of a Keirin or some other tight track bike and i wouldn't touch it. Leave it alone.

Then i would shorten the back as much as possible and put some super long dropouts on it for adjustment. I would give a 50-60mm drop to the BB shell.

and then i would muck about with the seat tube angle/length depending on if i want a ride the places me over the front wheel Vs a ride the moves my ass backwards. I'd prolly go 1 degree slacker than whatever the headtube is.   

I like a shorter bike, so i'd keep the TT length on the shorter end of "normal"

I'd plug that into that link i posted earlier, fill in the other dimensions logically (mabye a slight sylish dip to the toptube?), and then i'd print out the dimensions.

yea. not sure why i typed all of that out, but i enjoyed it.

This is what Tommasini have to sayu about fork rake

The fork can be made but it would be very steep and not really rideable...
Consider that a track fork usually had a 40mm rake... with a customized head angle.

I can't figure this out, as I can think of several OTP frames with a 35mm fork rake, the Cinelli Supercorsa Pista for one ? what am I missing here ?

So I found this interesting article by our very own Don Walker

http://www.urbanvelo.org/issue3/urbanvelo3_p44-45.html

Remembering that he is a forum member I dropped him a line

He wrote back within ten minutes !

He suggested that I needed a trail of ~58cm the article above explains his reasoning for this

His estimation was that to achieve this trail I needed to adjust the headtube angle to 54 degrees

And set the fork rake to 36mm

This I confirmed with this bloody excellent trail/rake calculator

http://www.anvilbikes.com/images/1064634020.xls

He also suggested raising the BB by a further 0.5cm

Thank you Mr Walker you are a top bloke ...:)

Buddha.

54 degrees? 54??

Cheers for the calculator. I'm swapping out the sus fork on a hybride with a carbon cycloX fork (when the last part for the rebuild arrives). I guessed I'd be reducing the trail by 5-15 (15=bad, 5=good)), looks more like an ideal 6ish
(Still gives me a headache though)

So I found this interesting article by our very own Don Walker

http://www.urbanvelo.org/issue3/urbanvelo3_p44-45.html

Remembering that he is a forum member I dropped him a line

He wrote back within ten minutes !

He suggested that I needed a trail of ~58cm the article above explains his reasoning for this

His estimation was that to achieve this trail I needed to adjust the headtube angle to 54 degrees

And set the fork rake to 36mm

This I confirmed with this bloody excellent trail/rake calculator

http://www.anvilbikes.com/images/1064634020.xls

He also suggested raising the BB by a further 0.5cm

Thank you Mr Walker you are a top bloke ...:)

Buddha.

I think you used the wrong side of the calculator?

58 trail you get

75 hta with 30.4 mm fork
74 hta with 36.3 mm fork
73 hta with 42.2 mm fork

'Fast' handling bike track bikes have a trail around 64

Gizmond, I started with the Cinelli Supercorsa pista of about the same size 59 x 57
this has a HTA 75 and a rake of 35mm giving a trail of 53mm

Tommasini suggests a 40mm rake on a HTA 75 giving a trail of 48mm
this makes absolutely no sense to me - I am thinking that what they mean is a HTA 73 with 40mm fork to give a trail of 60mm - i.e a road bike! - evidently their jig is set up to build road forks.

Don Walker suggests a HTA 74 with a 35mm rake to give a trail of 58mm

I am not sure where you get the figure 64mm trail for a track bike - what would be the HTA and fork rake to achieve this - do you have an example of this I can look at - thank you for your input - I am really having to think this through.

Dolan track champ has a 74 hta and comes with a 30mm fork = 64.4 trail
Planet X pro carbon track has a 75 hta and comes with a 25mm fork = 63.6 trail

I understand, at least with dolan anyway, they publish 74 as the hta, but it is actually 74.something

I think 48 trail will be very odd to ride.

Your figure of 58 trail sounds like a good way to go

Don Walker suggests a HTA 74 with a 35mm rake to give a trail of 58mm .

The Cinelli MASH above has 74.0 HTA with 35mm rake (L/XL) trail = 59,4

So sounds pretty good.

For anyone who cares:
My geekhouse's new geo.
its like a mid between track/ CX/ and off road SS
32c tyres!

1 Attachment

• henryuk2.pdf

eyebrows I can't read the yellow script - is that a 58mm trail?

The Cinelli MASH above has 74.0 HTA with 35mm rake (L/XL) trail = 59,4

So sounds pretty good.

The pro-track bike look as if they have a trail 60mm plus

Street tracks it looks as if 58-60mm the popular choice

I don't really think there is a need for a 75 HTA

unless you are proper racing

so 74HTA 36mm rake looks like the way to go...:)

I love this thread. It makes my head hurt, but my inner geek is smiling.

eyebrows I can't read the yellow script - is that a 58mm trail?

56.9
and 50mm fork rake I think

I cheated though, got marty to make it up.
Not going fully custom I don't think, but might do.

I love this thread. It makes my head hurt, but my inner geek is smiling.

Jaygee I think we are all just learning as we go along..;)