A mere pondering I suppose but how much do we think its noticable when changed?

I understand the general idea of it, that by increasing the offset you decrease the trail, in theory making the bike steer quicker but lose some stability at higher speeds.

In reality though, how pronounced is the effect.

For instance, on an xc hardtail how noticeable would a change from 45mm to 50mm offset be?

I ask mainly due to the number of forks out there that are cropping up with different offset options. Fox and Marzocchi do it, I expect rockshox do too. But most shops don't list what they are selling and use generic pictures.
So sometimes I guess people wouldn't know what they are fitting.

anybody tried anything that gives them an opinion, or indeed have an opinion any way?

For instance, on an xc hardtail how noticeable would a change from 45mm to 50mm offset be?

I think the effect is noticable but certainly not by everyone and you have to be aware of what you're trying to feel ... we all know the stories about people happily riding round with their suspension locked out or forks fitted backwards

I reckon a 10psi change in tyre pressure would produce a more noticeable effect for most.

You need a play on Tony Corke's (torke system & bicycle academy) adjustable geometry bike.


http://instagram.com/p/yCrNUpMHVF/

I'm gonna get some 50mm offset forks, maybe....

mountainbaker wrote:You need a play on Tony Corke's (torke system & bicycle academy) adjustable geometry bike.


http://instagram.com/p/yCrNUpMHVF/

Oooh, I like that!

Agree with what Stu said, some people won't notice (I mean some people don't even notice flat tyres!). Some people on the other hand are quite in tune with it all and can notice / utilise the subtle changes in geometry. But obviously it's not just geo on it's own, it's the whole system including where all the mass is etc. etc. etc. etc.

I've started to read this (well the 2002 version): http://www.tonyfoale.com/book.htm which is quite interesting, it's on pause at the moment though... but that gives a nice insight into things. Can't beat good old real life testing though.

That bike is amazing .. : ) Tony Foale did similar things with motorbikes (edit, as zippy just mentioned - his essays are worth a flip through). Those experiments and Mike Burrows' book suggests that most of it is about ergonomics, just fitting in the parts and achieving a layout that we can fit to with good weight distribution. And styling.. it's got to 'look right' .. whatever 'right' is this year.

In reality though, how pronounced is the effect.

For instance, on an xc hardtail how noticeable would a change from 45mm to 50mm offset be?

I'd notice it (I hope / usually) but it's subtle and I'm used to comparing changes like that. 5mm of rake has the same effect on trail as just under a degree on the head angle, at least for common 29er layouts.
And Stu's spot on, add a bit of tyre radius, or pressure change affecting tyre drop and contact patch and similar changes happen.

Some quick XL geekery on some middling numbers to illustrate ..

H Angle / Fork Offset / Wheel Rad / Trail
70.0 45.00 370.0 86.8
70.0 50.00 370.0 81.5
70.8 45.00 370.0 81.2
70.0 45.00 355.0 81.3

1st and 2nd rows compare the 5mm of rakes effect on trail. 3rd and 4th show other ways to get similar numbers to the second set. Not big differences here but once you get into 10% changes of trail it's notable and then it can come down to how you want your weight distributed as well. Mike Burrows' book Bicycle Design explains it all well. So much of it preference and habit though, there's no right answers but some bikes do it better than others I think.

So if i get some forks with extended offset that can have the travel adjusted to fiddle with the HA I could have a good old experiment

Cheers for the considered answers all.

FLV wrote:So if i get some forks with extended offset that can have the travel adjusted to fiddle with the HA I could have a good old experiment

Cheers for the considered answers all.

You could also try a range of wheels what with 650B ad 29er wheels, then a selection of tyres too to alter the overall radius

Agree with what Stu said, some people won't notice (I mean some people don't even notice flat tyres!). Some people on the other hand are quite in tune with it all and can notice / utilise the subtle changes in geometry.

As an example ... Ron Haslam maynot have the the most successful racer (although not bad, just often overshadowed) he was a brilliant development rider and could pick-up on tiny changes and alterations. He also had a great understanding of the mechanical principles so was able to give really constructive feedback / suggestions ... was a tester for many teams but didn't actually ride for them come race day.