Rake & steering sensitivity

[531colin]

I will stick my neck out and say that Offset is self centering value, more is more stable

A commonly held misconception....but in fact; more offset = less trail, less self centring in the steering.

Actually, hiding in there is an accurate observation.......
...."most bikes with a lot of offset are stable".......is true
....but they are stable because of the shallow head angle that goes with the long offset, not because of the offset itself.....

[Norman H]

I think you can get used to most things.

I have a fairly old Thorn Club Tour. It's a small frame (I'm about 5'6”). I've never accurately measured the fork offset but it appears to be about 65-70mm and I've always suspected that it would benefit from a fork with less rake. I've no idea what the head angle is but I estimate that the trail is around 30mm or less. The front centres are 600mm and I just avoid toe overlap with my size seven feet and 170mm cranks. Despite the alarming numbers it rides surprisingly well. Unladen at slow speed it requires a fair bit of steering input. It's much better with a bit of weight on the front end and it's rock steady descending at speed. I run 28mm tyres at around 60psi on the front. I can certainly notice the difference when I swap between bikes but I adapt very quickly.

[NATURAL ANKLING]

Hi,
From my previous posts on another earlier post I know the connection between offset and trail.

BUT offset puts the Axel Further Forward of the pivot (steering head) even though trail puts the tyre contact patch (with tarmac) Behind the pivot ( steering head).

You can wangle the trail to be the same on all bikes with tyres and head angle, but still have a different offset

This is what I mean..........................

Also wider tyres move the pivot off centre of the the tyre contact patch More so there is more wanting to come straight.....thus heavier steering

Tell me that bikes with simmilar trail and different offset handle the same.................
P.S. I see another 3D model coming up soon.

Edited - Sorry 531colin, I quickly read your post and I see some agreement there with offset..........

[ukdodger]

Hi,
From my previous posts on another earlier post I know the connection between offset and trail.

BUT offset puts the Axel Further Forward of the pivot (steering head) even though trail puts the tyre contact patch (with tarmac) Behind the pivot ( steering head).

You can wangle the trail to be the same on all bikes with tyres and head angle, but still have a different offset

This is what I mean..........................

Also wider tyres move the pivot off centre of the the tyre contact patch More so there is more wanting to come straight.....thus heavier steering

Tell me that bikes with simmilar trail and different offset handle the same.................
P.S. I see another 3D model coming up soon.

Edited - Sorry 531colin, I quickly read your post and I see some agreement there with offset..........

It seems to me that even a small amount of change in rake is noticeable. Makes me wonder how these m/bikes with front wheels that disappear into the distance can be steered at all.

[531colin]

well, I'm just looking at pictures...https://www.google.co.uk/search?sourceid=ie7&q=chopper+bike+photos&rls=com.microsoft:en-GB:IE-SearchBox&ie=UTF-8&oe=UTF-8&rlz=1I7SUNC_enGB402&gfe_rd=cr&ei=tVtRU9GkBoib8QOMl4CIBA
But it seems to me the bikes with the wheel way out front all have a really really slack head angle.
The Raleigh Choppers by comparison are quite conventional.

[Brucey]

....It seems to me that even a small amount of change in rake is noticeable. Makes me wonder how these m/bikes with front wheels that disappear into the distance can be steered at all.

Trail value? About 300mm....

-ah, well (as I hinted at in an earlier post, but in reverse re short wheelbases) on those chopper bikes there is hardly any weight on the wheel. So the long trail value (which would normally create incredibly heavy steering) is mitigated somewhat.

Lots of 'flop' at low speeds though.

cheers