Fork offset slack hta

Evening…

Struggling to get my head round the preffered fork for an upcoming build.

Hta 62 degrees (29er hard tail – hello dave by on one) and would appreciate thoughts on whether to go for a 51 or 42mm offset.

I generally ride twisty singletrack with occasional bike park visits.

I understand (rightly or wrongly) that a longer offset will promote a more agile ride which should suit my typical routes but as I’m generally wrong in my thought process I would welcome advice (correction) on which option to go for?

Cheers!!

Can you calculate the trail from the geometry numbers? Then compare with other bikes?

I’d go with the shorter offset, my 29er full-sus has similar angles at sag and I think it works better. Easier to weight the front tyre and it holds turns well.

I can’t explain it in terms of the trail figure because it seems that shorter offsets work better with slacker head angles, which mean you’re increasing the trail in two ways vs a steeper bike with longer offset. So comparisons to other bikes might just confuse you more.

Thanks, I’ve ordered a set of 51mm lyriks but it seems that shorter is the preffered route?
I was concerned that the short would make the the bike sluggish and cause too much trail (if that’s even a problem?)
I’ve got time to send back and opt for the shorter fork if this is deemed a better all rounder and would rather do it right the first time round!

For the twisty, I’d go 51. For the bike park, the shorter option might work better.

There is a calculator online that helps look at trail and wheel flop.

Short rake for high speed. Long rake for steep or lower speed.

When you hoping to get frame and start build?

So the general census suggests a longer fork for general UK trail riding which for me personally covers technical riding moreso over straight line speed so I’m guessing I’ve made the most compliant choice?
I’m looking to start the build as soon as I get the frame on 15th November so I’m buying parts now in readiness…
I’ve currently got the 150 lyrik ultimates (51mm), pacenti pdent bars with 20mm stem, hunt enduro wide wheels and Eagle gx groupset, will sort the rest out nearer the time but forks were my biggest concern due to the sheer cost.
Appreciate the answers and support!

Posted 52 minutes ago
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brant

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Short rake for high speed. Long rake for steep or lower speed.

I’m going for longer offset on my Doctahawk which also is a 29er with a 62 head angle. Most of my riding is steep tech.

Nice one, doctahawk seems a comparable bike in respect to sizing but not much feedback as its only just come out.
Great choice in bike, looks quality!

The frame is a really nicely put together bit of kit, Im in the process of getting all the bits together at the moment.

“Short rake for high speed. Long rake for steep…”

This makes sense to me. Not sure about low speed or climbing or cornering. But I don’t think it’s a huge deal.

This is an interesting read, from Doc Tomahawk himself:

https://m.pinkbike.com/news/chromag-doctahawk-a-nerdy-geometry-explanation.html

Ah sounds like a nice build look forward to hearing how you get on with it, Keep us posted.

Is there an ideal trail / flop target or is it the case of more of one and less of the other is better?

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I’d go with the shorter offset, my 29er full-sus has similar angles at sag and I think it works better. Easier to weight the front tyre and it holds turns well.

I can’t explain it in terms of the trail figure because it seems that shorter offsets work better with slacker head angles, which mean you’re increasing the trail in two ways vs a steeper bike with longer offset. So comparisons to other bikes might just confuse you more

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My understanding is the opposite of this. In essence if you have very slack head angles you risk wheel flop and vague steering, but gain in terms of high speed stability. So you want a force with a greater offset (ie 51mm which I think you’ve bought) in order to reduce trail and bring back a bit more control. With tighter head angles (particularly on 29ers) you want a shorter offset in order to increase trail and stop it being twitchy.

As I understand it the whole debate originated from the early days of 29ers. A 29 wheel on a frame with the same geometry as a 26 would naturally have more trail, so would suffer from wheel flop and feel slow and unwieldy in the turn. Solution was tighter head angles, but in turn this makes the bike feel skittery and prone to wheel tuck, so you shorten the offset to increase the trail as compensation. My 67 degree head angle hard tail has a 46mm trail fork, which feels perfect. If it was 70 degrees would want even less offset, slacker and would be looking at 51mm

Appreciate your detailed overview and glad it concurs with my initial thoughts.
Think I will stick with the longer offset on this case.

Still interested to know if there is a ‘golden’ trail / flop ratio as I’ve struggled to understand whether less is more or vice versa.

Any updates on the builds chaps?

There’s another factor. Where the weight is centred.

Move it forward or back and a particular trail/HA combo can feel wrong.

But not necessarily for long because we adapt.

hta = heavier than air?

If rake=angle

then what is short rake and long rake?

Does trail mean anything?
Castoration…

Ah saw that bike at bespoke a few years back and it was really heavy! Intresting to speak to the chap though.

Hullo,

A bit of a thread resurrection, but on the similar note.

HA in my new build will be 66.5 or 67, dependent on settings. 29er, 150 front, 135 rear.

Mainly riding UK, Lakes, Peaks a bit of odds and sods here and there. Definitely not a TC or Bike Park person. Natural, often technical stuff.

As a bike with complete build my frame is offered with 51mm off set. Would 42mm ruin it or make it vile?

Appreciate all input…

Cheers!
I.

In the bicycle world people refer to fork offset as rake as Brant does above

More exactly rake is the angle of the headtube, offset is the distance from the steerer centre to the axle

Edit – I don’t really know why this is but its often accepted in the bicycle world wheras in motorcycles rake is ALWAYs the head tube angle. Its also measured te opposite way so a bicycle head tube angle of 67 degrees would be 23 degrees on a motorcycle ie one measured from vertical the other from horizontal

It causes a lot of confusion that rake is used for a measurement in milimeters

For comparison my Slash 8 came with a 42mm offset fork and it feels great. Not sure if it feels slower or faster turning than my 51mm offset Ibis as they’re totally different bikes.

The future

That last one is probably “a tad” too progressive for my likings 😉

Thanks for opinions Good Peeps, keep them comming please.

Cheers!
I.

Enjoyed that PB video