I’m baffled

My Cannondale Trigger had Fox forks with a 51mm offset. I can’t seem to find another pair but have found a fork with a 41mm offset

Will I notice this difference?

Will I notice this difference?

Yes

yes…..and yes

I’m not sure anyone really understands it – it’s bloody weird how head angle, offset and wheel radius interact to affect stability due to trail, wheelbase and what I’ll have to call flip flop because I don’t know what it is (where turning the bars lifts the front of the frame).

Less offset increases trail whilst reducing wheelbase (and front centre) and the flip flop jacking thing.

Less offset gives more trail makes steering more stable but also reduces wheelbase and puts more weight on front tyre

Ah so I should stick with 51 or thereabouts?

safest option. However I am unconvinced it makes as much difference as folk think having seen some experiments with motorcycles where they tried changing offset / trail and rake a lot and they remained rideable adn even similar handling. also motorcycles have halved the trail they have in 25 years

Its a complex interaction tho – and there is a book that explains it all well but I can’t remember the title – sorry0

There used to be a helpful article on the Singular website but I can’t find it now….

I do.

By which I mean of course I bloody don’t, don’t be absurd. No one does.

I know it’s old, but does this sort of illustrate it?

[video]https://www.youtube.com/watch?v=PwR0T5a4uuM[/video]

[edit] that video covers it better

In oversimplified terms, trail provides slow speed stability (stability increases with trail) and head angle provides fast speed stability (stability increases with slackness).

Increasing fork offset reduces trail so makes the bike more twitchy in tight/slow corners.

Changing trail by 1cm is ~10% change which is significant, if you find the bike currently a bit twitchy at slow speeds then it could be a good thing, if you think the bike handles like a tank then it will certainly be a bad thing.

Is your bike 27.5 or 29?

YMMV 🙂

This explains it well:

http://www.bikeradar.com/mtb/gear/article/pushing-the-limits-of-fork-offset-an-experiment-45343/

this should help if you can get your head round it.
less trail = more twitchy, more trail = more stable

My bike came with 41mm offset and I replaced with forks with 51mm offset. The difference is noticeable. The bike rode fine on the 41mm offset forks, however the feel of the bike (not capability – that rests with the rider) was definitely improved with the 51mm forks. The steering felt more responsive for sure but I do get the flip flop more on steep climbs – not a problem at all, you just get used to it.

I’d stick with the 51mm offset if you can – surprised you are struggling to find forks with 51mm offset. I thought Fox forks were 51mm offset as standard whereas RS were 41mm with 51mm offset available for 29ers. I think the Lefty Max’s on the C’dale bikes has an even bigger offset than 51mm.

It’s not so much struggling to find a 51mm offset fork. It’s trying to find one with a 1.5in straight steerer

Knew there would be a reason those Triggers were cheap!

Cheers gents

Brant tried to explain it to me a couple of times when we were riding the Ragley TD1 prototypes. I still don’t know how it works.

fyi, bike24 seem to have most combinations of fork length, spring and offset.
It was the only place I could find that was a sensible price and offered the 51mm offset SID for my czar.

It’s not so much struggling to find a 51mm offset fork. It’s trying to find one with a 1.5in straight steerer

Does anyone make 650b forks with a straight steerer (other than Lefty’s?).

If you want to upgrade the fork I suspect it’ll mean a new headset and stem.

I’ve done a direct swap after someone ordered/supplied the wrong offset for a road fork.
Noticeable difference to handling, not saying it was bad. But i’d not have fancied doing anything other than a TT on it once the new fork was fitted (only temporarily, they ordered another one once i’d noticed and put the proper offset back in) I’d have probably got used to it eventually, was just a bit jarring to get on the bike. think it should have had a 38 and a 43 or 45 arrived, might have been the other way round. Was 20+ years ago.

I suspect on full suss and HT frames (or those with massive squishy tyres, or motorbikes) that there are so many degrees of movement that a few mm here and there will make virtually no difference.